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UBC Theses and Dissertations

Cardiovascular responses to a psychological stressor in high versus low reactive women Frankish, Charles James 1985

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CARDIOVASCULAR RESPONSES TO A PSYCHOLOGICAL STRESSOR IN HIGH VERSUS LOW REACTIVE WOMEN by CHARLES JAMES FRANKISH B . A . , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES Depar tment o f P s y c h o l o g y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BR IT ISH COLUMBIA J u l y , 1985 © C h a r l e s F r a n k i s h , 1985 7 8 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my d e p a r t m e n t o r b y h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f PSYCHOLOGY The U n i v e r s i t y o f B r i t i s h C o l u m b i a 1956 Main M a l l V a n c o u v e r , C a n a d a V6T 1Y3 D a t e November 15, 1985. /si ^  ABSTRACT Re cen t s t u d i e s have i m p l i c a t e d a c u t e r e a c t i v i t y t o a p s y c h o l o g i c a l s t r e s s o r as a p o t e n t i a l marke r i n t h e p a t h o g e n e s i s o f c a r d i o v a s c u l a r d i s o r d e r s . However , o n l y v e r y few w e l l c o n t r o l l e d p r o s p e c t i v e s t u d i e s n e c e s s a r y t o c o n f i r m t h i s h y p o t h e s i s have been c o n d u c t e d . Such s t u d i e s wou l d need t o d e m o n s t r a t e t h a t c a r d i o v a s c u l a r h y p e r r e a c t i v i t y i s a s t a b l e , i n d i v i d u a l - s p e c i f i c p r e d i s p o s i t i o n wh i c h i s n o t s i g n i f i c a n t l y a f f e c t e d by r e s p o n s e h a b i t u a t i o n t o r e p e a t e d s t r e s s o r e x p o s u r e s . I n t h e p r e s e n t s t u d y t h e r e l a t i o n s h i p between deg ree o f c a r d i o v a s c u l a r r e s p o n s i v e n e s s and r e s p o n s e h a b i t u a t i o n as a f u n c t i o n o f number o f s t r e s s o r r e p e t i t i o n s and l e n g t h o f i n t e r s t r e s s o r i n t e r v a l was a s s e s s e d . Responses t o a m e n t a l a r i t h m e t i c t a s k were compared w i t h i n t r i a l s (3 m i n u t e s ) , a c r o s s t r i a l s ( 3 per s e s s i o n ) , and a c r o s s e x p e r i m e n t a l s e s s i o n s (2 s e s s i o n s w i t h a 4-week i n t e r v a l ) i n h i g h v e r s u s l ow c a r d i o - r e a c t i v e women. N i n e t y f e m a l e , n o r m o t e n s i v e s u b j e c t s (mean age 2 4 . 6 y e a r s ) p a r t i c i p a t e d i n t h e s t u d y . S u b j e c t s were r andom ly a s s i g n e d t o one o f two e x p e r i m e n t a l c o n d i t i o n s : i n C o n d i t i o n 1 ( r e p e a t e d e x p o s u r e ) a twen t y m inu t e a d a p t a t i o n p e r i o d was f o l l o w e d by a s e r i e s o f t h r e e , 3 m inu t e m e n t a l a r i t h m e t i c t a s k s w i t h a 90 db w h i t e n o i s e i n t e r f e r e n c e d u r i n g t h e f i r s t l a b o r a t o r y s e s s i o n . A t h r e e m i nu t e r e s t p e r i o d f o l l o w e d each t a s k p e r i o d . S u b j e c t s i n C o n d i t i o n 2 ( s i n g l e e x p o s u r e ) c o m p l e t e d t h e t w e n t y - m i n u t e a d a p t a t i o n p e r i o d f o l l o w e d by a s i n g l e 3 -m inu t e t a s k and a s ub sequen t f i f t e e n - m i n u t e r e c o v e r y p e r i o d . D u r i n g t h e i r s e cond v i s i t a l l s u b j e c t s c o m p l e t e d a s e r i e s o f t h r e e m e n t a l a r i t h m e t i c t a s k s i d e n t i c a l t o t h o s e c omp l e t ed i n C o n d i t i o n 1, v i s i t 1. Th roughou t t h e e x p e r i m e n t a l s e s s i o n s h e a r t r a t e (HR ) , s y s t o l i c ( S B P ) , d i a s t o l i c ( D B P ) , and - i i i -mean a r t e r i a l p r e s s u r e (MAP) were m o n i t o r e d a t one m inu t e i n t e r v a l s u s i n g an a u t o m a t e d , d i g i t a l Dinamap 845 V i t a l S i g n s M o n i t o r . S u b j e c t s were c l a s s i f i e d i n t o h e a r t r a t e and SBP r e a c t i v i t y t e r c i l e s on the b a s i s o f t h e i r r e s p o n s e t o t h e f i r s t s t r e s s t a s k i n t h e i n i t i a l s e s s i o n . On l y t h o s e s u b j e c t s who f e l l i n t o t h e l o w e s t and h i g h e s t r e a c t i v i t y t e r c i l e s were i n c l u d e d i n s ub sequen t a n a l y s e s . G i v e n t h a t n o t a l l s u b j e c t s r e c e i v e d a l l t r i a l s t h r e e s e t s o f a n a l y s e s o f c o v a r i a n c e were n e c e s s a r y t o f u l l y examine t h e 2 ( l ow v e r s u s h i g h r e a c t i v i t y ) X 2 ( c o n d i t i o n s ) X 2 ( v i s i t s ) X 3 ( t r i a l s ) X 3 ( m i n u t e s pe r t r i a l ) r e p e a t e d measures f a c t o r i a l d e s i g n . Age and r e s p e c t i v e b a s e l i n e s were emp loyed as c o v a r i a t e s . The r e s u l t s c o n s i s t e n t l y i n d i c a t e d ma in e f f e c t s (_p_ < .001) f o r t h e r e a c t i v i t y g r o u p s , v i s i t s , t r i a l s , and m i n u t e s f a c t o r s on ea ch o f t h e f o u r dependent m e a s u r e s . These f i n d i n g s t o g e t h e r w i t h t h e r e s u l t s o f s ub sequen t t r e n d a n a l y s e s and Newman-Keuls p o s t - h o c t e s t s i d e n t i f i e d s i g n i f i c a n t d e c r e a s e s i n r e s p o n s e l e v e l s w i t h i n t r i a l s , a c r o s s t r i a l s , and a c r o s s t h e two e x p e r i m e n t a l s e s s i o n s . D e c r e a s e s f r om m inu t e 1 t o m inu te 2 o f each t r i a l were g r e a t e r t h an t h o s e f r om m inu t e 2 t o m inu t e 3 on h e a r t r a t e m e a s u r e s . The same p a t t e r n o f d e c r e a s e s was o b s e r v e d f o r t h e t r i a l s f a c t o r . B l o o d p r e s s u r e r e s p o n s e s showed a d e l a y e d o n s e t o f d e c r e a s e s i n r e s p o n s e magn i t ude w i t h i n e x p e r i m e n t a l t r i a l s . A l l b l o o d p r e s s u r e measures showed e v i d e n c e o f r e s p o n s e d e c r e a s e s f r om m i n u t e 2 t o m i n u t e 3 o f ea ch t r i a l . H i g h r e a c t o r s showed g r e a t e r d e c r e a s e s i n r e s p o n s e s t han low r e a c t o r s a c r o s s t h e e x p e r i m e n t a l s e s s i o n s . F o r t h e f i n a l s t r e s s t a s k t h e HR, DBP and MAP r e s p o n s e s o f t h e h i g h r e a c t i v i t y g r oup s i n t h e r e p e a t e d s t r e s s o r c o n d i t i o n c o u l d n o t be d i s c r i m i n a t e d f r om t h o s e o f t h e low r e a c t o r s . The n o t i o n o f w i t h i n - i n d i v i d u a l r e s p o n s e s p e c i f i c i t y and t he use o f a c u t e c a r d i o v a s c u l a r r e a c t i v i t y as b o t h a c l a s s i f i c a t i o n and an outcome measure may t h e r e f o r e need t o be r e - e v a l u a t e d . - iv -TABLE OF CONTENTS ABSTRACT Response stereotypy Psychological mediators Physiological mediators Classification of stressors Sensory intake versus sensory rejection Active versus passive coping Engagement-involvement Mental arithmetic as a stressor Summary: Stimulus specificity versus response stereotypy Page i i L i st of Tables v i l L i s t of Figures List of Appendices Acknowledgement v x x x i x x INTRODUCTION x LITERATURE REVIEW 5 Basic Cardiophysiology Stress and Cardiovascular Disease Cardiovascular Reactivity and Coronary Heart Disease ^ Q Animal models Q Prospective human studies Retrospective studies ^ Type-A studies ^ Individual Differences ^ 12 12 13 Task Influences ^ Stimulus specificity ^ 16 16 17 19 20 24 Task-Person Interactions 25 Stability of Individual Differences in Cardiovascular Reactivity 28 Habituation of Cardiovascular Responses 30 Characteristics of cardiovascular habituation 31 - V -Page M e t h o d o l o g i c a l I s s u e s R e g a r d i n g R e a c t i v i t y and H a b i t u a t i o n 32 S u b j e c t c h a r a c t e r i s t i c s 33 A d a p t a t i o n and b a s e l i n e measures 36 I n s t r u c t i o n e f f e c t s 38 Task c h a r a c t e r i s t i c s 39 S t i m u l u s r e p e t i t i o n and i n t e r - s t r e s s o r i n t e r v a l 40 Summary 42 S e l e c t i o n o f r e s p o n s e measures 43 Pu r po s e o f t h e S tudy and E x p e r i m e n t a l Hypo t he se s 45 Method S y n o p s i s 47 Method 49 S u b j e c t c h a r a c t e r i s t i c s 49 E x p e r i m e n t a l s e t t i n g 49 A p p a r a t u s and Equ ipment 49 C a r d i o v a s c u l a r dependent measures 50 S e l f - r e p o r t measures 50 S t r e s s t a s k 5 0 P r o c e d u r e 51 P r e - e x p e r i m e n t a l p r e p a r a t i o n s 51 P r e - s t r e s s a d a p t a t i o n 51 E x p e r i m e n t a l c o n d i t i o n 52 D e b r i e f i n g 53 E x p e r i m e n t a l d e s i g n and s t a t i s t i c a l a n a l y s e s 55 R e s u l t s 55 D e s c r i p t i v e c h a r a c t e r i s t i c s o f c a r d i o v a s c u l a r dependent measures 55 D e s c r i p t i v e c h a r a c t e r i s t i c s o f s e l f - r e p o r t dependent measures 56 D e s c r i p t i v e c h a r a c t e r i s t i c s o f c a r d i o v a s c u l a r r e a c t i v i t y g r oups 56 C o r r e l a t i o n a l A n a l y s e s 69 W i t h i n s e s s i o n c a r d i o v a s c u l a r c o r r e l a t i o n s 72 A c r o s s s e s s i o n c a r d i o v a s c u l a r c o r r e l a t i o n s 74 I n t e r c o r r e l a t i o n s o f s e l f - r e p o r t measures 75 I n t e r c o r r e l a t i o n s o f s e l f - r e p o r t and c a r d i o v a s c u l a r measures 75 A n a l y s e s o f c o v a r i a n c e 77 H e a r t r a t e ANCOVAs 78 C o n d i t i o n 1 ANCOVA 79 Task 1 ANCOVA 84 V i s i t 2 ANCOVA 86 S y s t o l i c b l o o d p r e s s u r e ANCOVAS 90 C o n d i t i o n 1 ANCOVA 90 Task 1 ANCOVA 94 V i s i t 2 ANCOVA 95 - v i -Page D i a s t o l i c b l o o d p r e s s u r e ANCOVAs 97 C o n d i t i o n 1 ANCOVA 97 Task 1 ANCOVA 103 V i s i t 2 ANCOVA 104 Mean a r t e r i a l p r e s s u r e ANCOVAS 106 C o n d i t i o n 1 ANCOVA 106 Task 1 ANCOVA 109 V i s i t 2 ANCOVA 110 Summary o f ANCOVA E f f e c t s 112 D i s c u s s i o n 114 S u b j e c t c h a r a c t e r i s t i c s and r e a c t i v i t y g r oups 115 C a r d i o v a s c u l a r Dependent measures 120 S e l f - r e p o r t measures 122 C o n d i t i o n 1 ANCOVAS 123 Task 1 ANCOVAS 124 V i s i t 2 ANCOVAs 125 Ma j o r c o n c l u s i o n s and r e commenda t i ons 126 R e f e r e n c e s 131 A p p e n d i c e s 155 - v i i -L IST OF TABLES T a b l e 1 C o r r e l a t i o n s Among C a r d i o v a s c u l a r Change S c o r e s E l i c i t e d by a V a r i e t y o f T a s k s T a b l e 2 C a r d i o v a s c u l a r Changes A s s o c i a t e d w i t h a M e n t a l A r i t h m e t i c S t r e s s o r T a b l e 3 E x p e r i m e n t a l D e s i g n T a b l e 4 B l o o d P r e s s u r e Norms f o r Women Aged 18-67 Y e a r s T a b l e 5 Means and S t a n d a r d D e v i a t i o n s o f C a r d i o v a s c u l a r Dependent Measu re s T a b l e 6 Means and S t a n d a r d D e v i a t i o n s o f S e l f - R e p o r t Measu re s T a b l e 7 F r e quen c y D i s t r i b u t i o n o f S y s t o l i c B l o o d P r e s s u r e and H e a r t Ra t e R e a c t i v i t y G roups T a b l e 8 Compa r i s on o f H e a r t Ra t e and S y s t o l i c R e a c t i v i t y a c r o s s E x p e r i m e n t a l S e s s i o n s T a b l e 9 C l a s s i f i c a t i o n o f S u b j e c t s by H e a r t Ra t e v e r s u s S y s t o l i c B l o o d P r e s s u r e R e a c t i v i t y T a b l e 10 C r o s s t a b u l a t i o n o f B i r t h C o n t r o l , M e n s t r u a t i o n and R e a c t i v i t y V a r i a b l e s T a b l e 11 I n t e r c o r r e l a t i o n s o f C a r d i o v a s c u l a r Dependent Measu re s T a b l e 12 C o r r e l a t i o n s o f S u b j e c t Age w i t h B a s e l i n e B l o o d P r e s s u r e and S t r e s s Response Measu re s T a b l e 13 C o r r e l a t i o n s o f S e l f - R e p o r t e d F i t n e s s L e v e l and F r equen cy o f P h y s i c a l A c t i v i t y w i t h C a r d i o v a s c u l a r S t r e s s Response and Re cove r y P e r i o d V a l u e s T a b l e 14 I n t e r c o r r e l a t i o n s o f S e l f - R e p o r t Measu re s T a b l e 15 - Summary o f ANCOVA E f f e c t s Page 11 21 49 55 58 63 65 66 68 69 71 72 74 77 114 V - v i i i -L I ST OF FIGURES Page F i g u r e 1 C o n d i t i o n 1: H e a r t Ra t e Da t a 58 F i g u r e 2 Task 1: H e a r t Ra t e Da ta 80 F i g u r e 3 V i s i t 2: H e a r t Ra t e Da t a 81 F i g u r e 4 C o n d i t i o n 1: S y s t o l i c B l o o d P r e s s u r e Da t a 59 F i g u r e 5 Task 1: S y s t o l i c B l o o d P r e s s u r e Da t a 91 F i g u r e 6 V i s i t 2: S y s t o l i c B l o o d P r e s s u r e Da ta 92 F i g u r e 7 C o n d i t i o n 1: D i a s t o l i c B l o o d P r e s s u r e Da t a 60 F i g u r e 8 Task 1: D i a s t o l i c B l o o d P r e s s u r e Da ta 89 F i g u r e 9 V i s i t 2: D i a s t o l i c B l o o d P r e s s u r e Da t a 100 F i g u r e 10 C o n d i t i o n 1: Mean A r t e r i a l P r e s s u r e Da t a 61 F i g u r e 11 Task 1: Mean A r t e r i a l P r e s s u r e Da t a 107 F i g u r e 12 V i s i t 2: Mean A r t e r i a l P r e s s u r e Da t a 108 F i g u r e 13 Task 1 H e a r t R a t e : V i s i t s X C o n d i t i o n s X Groups I n t e r a c t i o n 87 F i g u r e 14 V i s i t 2 H e a e r t R a t e : T r i a l s X M i n u t e s X Groups I n t e r a c t i o n 89 F i g u r e 15 V i s i t 2 S y s t o l i c B l o o d P r e s s u r e : C o n d i t i o n s X T r i a l s X Groups I n t e r a c t i o n 98 F i g u r e 16 C o n d i t i o n 1 D i a s t o l i c B l o o d P r e s s u r e : T r i a l s X M i n u t e s X Groups I n t e r a c t i o n 102 F i g u r e 17 V i s i t 2 D i a s t o l i c B l o o d P r e s s u r e : C o n d i t i o n s X M i n u t e s X Groups I n t e r a c t i o n 105 F i g u r e 18 Task 1 Mean A r t e r i a l P r e s s u r e : C o n d i t i o n s X M i n u t e s X Groups I n t e r a c t i o n 111 F i g u r e 19 C o n d i t i o n 1 H e a r t R a t e : V i s i t s X T r i a l s X Groups I n t e r a c t i o n 83 L IST OF APPENDICES Page Append i x 1 S u b j e c t Con sen t Form 155 Append i x 2 P a r -Q S c r e e n i n g Q u e s t i o n n a i r e 156 Append i x 3 S t r e s s P e r c e p t i o n Q u e s t i o n n a i r e 157 Append i x 4 E x p e r i m e n t a l S c r i p t 158 Append i x 5 C o n d i t i o n 1 H e a r t Ra t e ANCOVA 160 Append i x 6 Task 1 H e a r t Ra t e ANCOVA 161 Append i x 7 V i s i t 2 H e a r t Ra t e ANCOVA 162 Append i x 8 Newman K u e l s T e s t s o f H e a r t Ra t e Da ta 163 Append i x 9 S c h e f f e ' s T e s t s o f H e a r t Ra t e Da t a 164 Append i x 10 C o n d i t i o n 1 S y s t o l i c B l o o d P r e s s u r e ANCOVA 165 Append i x 11 Task 1 S y s t o l i c B l o o d P r e s s u r e ANCOVA 166 Append i x 12 V i s i t 2 S y s t o l i c B l o o d P r e s s u r e ANCOVA 167 Append i x 13 Newman-Keuls T e s t s o f S y s t o l i c B l o o d P r e s s u r e Da t a 168 Append i x 14 S c h e f f e ' s T e s t s o f S y s t o l i c B l o o d P r e s s u r e Da t a 169 Append i x 15 C o n d i t i o n 1 D i a s t o l i c B l o o d P r e s s u r e ANCOVA 170 Append i x 16 Task 1 D i a s t o l i c B l o o d P r e s s u r e ANCOVA 171 Append i x 17 V i s i t 2 D i a s t o l i c B l o o d P r e s s u r e ANCOVA 172 Append i x 18 Newman-Keuls T e s t s o f D i a s t o l i c B l o o d P r e s s u r e Da t a 173 Append i x 19 S c h e f f e ' s T e s t s o f D i a s t o l i c B l o o d P r e s s u r e Da t a 174 Append i x 20 C o n d i t i o n 1 Mean A r t e r i a l P r e s s u r e ANCOVA 175 Append i x 21 Task 1 Mean A r t e r i a l P r e s s u r e ANCOVA 176 Append i x 22 V i s i t 2 Mean A r t e r i a l P r e s s u r e ANCOVA 177 Append i x 23 Neuman-Keu ls T e s t s o f Mean A r t e r i a l P r e s s u r e Da t a 178 A p p e n d i x 24 S c h e f f e ' s T e s t s o f Mean A r t e r i a l P r e s s u r e Da ta 179 - X -ACKNOWLEDGEMENTS I wou l d l i k e t o t hank my f r i e n d and s u p e r v i s o r , D r . W. L i n d e n , whose s u p p o r t and a d v i c e n e v e r w a v e r e d . S e c o n d , I w i s h t o e x p r e s s my g r a t i t u d e t o my t h e s i s c ommi t t ee members: D r . G . J . J o h n s o n , D r . W. I a c o n o , and D r . D. C r o c k e t t f o r t h e i r h i g h q u a l i t y g u i d a n c e . T h i r d , my t h a n k s a r e e x t ended t o t h e r e s e a r c h a s s i s t a n t s and c ompu t i ng c e n t r e s t a f f f o r t h e i r a s s i s t a n c e . F i n a l l y , I am i n d e b t e d t o my f a m i l y , f r i e n d s , and f e l l o w s t u d e n t s whose s u p p o r t and c a r i n g a r e i n e x t r i c a b l y woven i n t o t h e s u b s t a n c e o f t h i s t h e s i s . - 1 -INTRODUCTION Over t h e p a s t t h r e e decades numerous r e s e a r c h e r s ( E l i o t , B u e l l , & D e m b r o s k i , 1982; F r a n k e n h a e u s e r , 1975; G l a s s , 1977; O b r i s t , 1981) have p r o v i d e d e v i d e n c e o f a p o s i t i v e r e l a t i o n s h i p between t he deve l opment o f c o r o n a r y p a t h o l o g y and m a l a d a p t i v e r e s p o n s e s t o s t r e s s . R e s e a r c h r e g a r d i n g t he i n f l u e n c e o f b e h a v i o r a l and p s y c h o s o c i a l f a c t o r s on c o r o n a r y d i s e a s e has i n f a c t , become one o f t h e most e x t e n s i v e l y d e v e l o p e d a r e a s i n t h e s t u d y o f p s y c h o l o g i c a l i n f l u e n c e s on h e a l t h . C a r d i o v a s c u l a r p a t h o l o g y has been a s s o c i a t e d w i t h b o t h an i n d i v i d u a l ' s i n i t i a l o r a c u t e r e s p o n s e t o s t r e s s and h i s o r he r c h r o n i c c o p i n g r e s p o n s e t o a g i v e n s t r e s s o r o v e r t i m e . Re cen t b i o m e d i c a l and b e h a v i o r a l r e s e a r c h has l i n k e d b e h a v i o r a l l y - i n d u c e d , a c u t e e n d o c r i n e and c a r d i o v a s c u l a r r e s p o n s e s t o p s y c h o l o g i c a l s t r e s s w i t h an i n c r e a s e d i n c i d e n c e o f e s s e n t i a l h y p e r t e n s i o n and o t h e r c a r d i o v a s c u l a r p a t h o l o g y . F o r e xamp l e , i t has been s u g g e s t e d t h a t p h y s i o l o g i c h y p e r r e s p o n s i v e n e s s t o p s y c h o l o g i c a l s t r e s s may be a marke r o f p a t h o g e n i c p r o c e s s e s and i n c r e a s e d r i s k i n t h e e t i o l o g y o f c o r o n a r y h e a r t d i s e a s e and e s s e n t i a l h y p e r t e n s i o n ( s ee E l i o t , B u e l l , & D e m b r o s k i , 1982; K r a n t z , Baum, & S i n g e r , 1983; K r a n t z & Manuck, 1984 f o r e x t e n s i v e r e v i e w s ) . I n g e n e r a l , p h y s i o l o g i c a l h y p e r r e s p o n s e s have been a s s o c i a t e d w i t h an i n c r e a s e d i n c i d e n c e o f p s y c h o s o m a t i c d i s o r d e r s ( D e m b r o s k i , 1978; S t e p t o e , R o s s , & M e l v i l l e , 1 9 8 4 ) . S t u d i e s o f b o t h a n i m a l s and humans i n d i c a t e t h a t p o t e n t i a l l y p a t h o g e n i c s t a t e s can be p roduced t h r o u g h e x p o s u r e t o b e h a v i o r a l s t i m u l i ( E n g e l & B i c k f o r d , 1 961 ; Manuck, K a p l a n , & C l a r k s o n , 1 9 8 3 ) . Such s t u d i e s have emp loyed b o t h n a t u r a l i s t i c and l a b o r a t o r y s t r e s s o r s . P s y c h o l o g i c a l s t r e s s i s most o f t e n i n d u c e d i n t h e l a b o r a t o r y t h r o u g h t h e use o f m e n t a l s t r e s s t a s k s . D u r i n g s u ch a t a s k t he s u b j e c t p e r f o r m s a c o g n i t i v e t a s k w h i l e m u l t i p l e - 2 -s u b j e c t i v e , b e h a v i o r a l , and p h y s i o l o g i c a l dependent v a r i a b l e s a r e a s s e s s e d . S t r e s s t a s k r e s p o n s e l e v e l s a r e t h e n compared t o p r e - s t r e s s o r b a s e l i n e v a l u e s ( L i n d e n & McEa che rn , 1 9 8 5 ) . P e r h ap s t h e most f r e q u e n t l y emp loyed c o g n i t i v e s t r e s s o r i s a m e n t a l a r i t h m e t i c t a s k . T y p i c a l l y , s u b j e c t s a r e r e q u i r e d t o s e r i a l l y s u b t r a c t a g i v e n number f r om t h e number 1 , 000 . Some r e s e a r c h e r s have added an a d d i t i o n a l w h i t e n o i s e component i n an a t t e m p t t o d e v e l o p a r e l i a b l e p s y c h o l o g i c a l s t r e s s o r ( V o s s e l & L a u x , 1977; S c h u l t e & Neus , 1979; Neus e t a l . , 1981 ; S c h u l t e F r i e d r i c h , R u d d e l , S c h i r m e r , & von E i f f , 1981 ; L i n d e n , F r a n k i s h , & McEa che r n , 1 9 8 5 ) . The s t u d y o f a c u t e c a r d i o v a s c u l a r r e s p o n s e s t o s t r e s s o r s s u ch as m e n t a l a r i t h m e t i c has been u n d e r t a k e n by many a u t h o r s ( O b r i s t , 1981 ; K r a n t z & Manuck, 1984; L i n d e n , 1984; L i n d e n e t a l . , 1 9 8 5 ) . Responses t o c o g n i t i v e s t r e s s o r s have been v a r i o u s l y c h a r a c t e r i z e d as b e i n g due t o i n d i v i d u a l - s p e c i f i c f a c t o r s , s t i m u l u s - s p e c i f i c f a c t o r s , o r some i n t e r a c t i o n o f t h e s e two d i m e n s i o n s . I n d i v i d u a l - s p e c i f i c r e s p o n s e s t o s t r e s s have been a t t r i b u t e d t o b o t h p s y c h o l o g i c a l c h a r a c t e r i s t i c s su ch as n e u r o t i c i s m ( E y s e n c k , 1 9 6 7 ) , l o c u s o f c o n t r o l ( H a r r e l , 1980) and r e p r e s s i o n - s e n s i t i z a t i o n ( L i n d e n , 1 9 8 4 ) , and t he p r e v i o u s l y n o t e d p h y s i o l o g i c a l c h a r a c t e r i s t i c s su ch as s y m p a t h e t i c h y p e r r e s p o n s i v e n e s s . E v i d e n c e e x i s t s t h a t i n d i v i d u a l s t e nd t o d i s p l a y a r e l a t i v e l y s t a b l e , i d i o s y n c r a t i c a l l y d e t e r m i n e d s t r e s s r e s p o n s e p a t t e r n ( L a c ey & L a c e y , 1962; M i n e r , M cK i nney , R u d d e l , B u e l l , E l i o t , & G r a n t , 1 9 8 4 ) . From a s t i m u l u s - s p e c i f i c p e r s p e c t i v e r e s p o n s e s t o t a s k s su ch as m e n t a l a r i t h m e t i c have been c h a r a c t e r i z e d as i n v o l v i n g s e n s o r y r e j e c t i o n ( L i b b y , L a c e y , & L a c e y , 1962) and a c t i v e c o p i n g ( O b r i s t , G a b e l e i n , T e l l e r , L a n g e r , G r i g n o l o , L i g h t , & McCubb i n , 1978; L i n d e n , 1 9 8 4 ) . A c t i v e c o p i n g , s e n s o r y r e j e c t i o n t a s k s t y p i c a l l y p roduce s i g n i f i c a n t e l e v a t i o n s o f h e a r t r a t e and b l o o d p r e s s u r e . Such hemodynamic changes a r e presumed i n s t r u m e n t a l i n t he - 3 deve l opment o f e s s e n t i a l h y p e r t e n s i o n ( O b r i s t , 1981 ; H i j z e n , van de r G u g t e r , & B o n t e r , 1984) t h u s j u s t i f y i n g t h e r e c e n t f o c u s o f c a r d i o v a s c u l a r r e s e a r c h e r s on s t r e s s and c o p i n g . L a z a r u s and Fo l kman (1984) have p r e s e n t e d f u r t h e r e v i d e n c e t h a t t h e e f f e c t i v e n e s s o f p s y c h o s o c i a l f a c t o r s i n p r o d u c i n g p o t e n t i a l l y p a t h o g e n i c s y m p a t h e t i c a r o u s a l depends on t h e i n d i v i d u a l ' s c o g n i t i v e a p p r a i s a l o f h i s o r h e r a b i l i t y t o cope i n a g i v e n s i t u a t i o n . I n a d d i t i o n t o a s s e s s i n g a c u t e c a r d i o v a s c u l a r r e a c t i v i t y t o p s y c h o l o g i c a l s t r e s s , r e s e a r c h e r s a r e c on c e r ned w i t h t h e r o l e o f r e p e a t e d e x p o s u r e t o s t r e s s i n t h e t r a n s d u c t i o n o f a c u t e h y p e r r e s p o n s e s i n t o c h r o n i c c o r o n a r y d i s e a s e . O b r i s t e t a l . ( 1978 ) have s u g g e s t e d f o r e x amp l e , t h a t a m a l a d a p t i v e r e s p o n s e t o p s y c h o l o g i c a l s t r e s s may be one i n w h i c h i n c r e a s e d o r m a i n t a i n e d c a r d i o v a s c u l a r a r o u s a l i s n o t a s s o c i a t e d w i t h a s p e c i f i c m e t a b o l i c n e e d . H a b i t u a t i o n o f h e a r t r a t e r e s p o n s e s f o l l o w i n g r e p e a t e d p r e s e n t a t i o n o f a c o g n i t i v e s t r e s s o r has been r e p o r t e d ( L a n e , 1984; Manuck & S c h a e f f e r , 1978; Manuck & G a r l a n d , 1980; S c h u l t e e t a l . , 1981 ; Zwaga, 1 9 7 3 ) . A l t h o u g h t h e r e i s some e v i d e n c e o f s y s t o l i c b l o o d p r e s s u r e h a b i t u a t i o n t o a m e n t a l a r i t h m e t i c s t r e s s o r a c r o s s r e l a t i v e l y s h o r t i n t e r - s t r e s s o r i n t e r v a l s ( L a n e , 1 9 8 4 ) , t h e q u e s t i o n o f s t i m u l u s r e p e t i t i o n e f f e c t s on s y s t o l i c ( S B P ) , d i a s t o l i c ( D B P ) , and mean a r t e r i a l p r e s s u r e (MAP) has n o t been a d e q u a t e l y a d d r e s s e d . Th rough t h e use o f e x p e r i m e n t a l pa r ad i gms s i m i l a r t o t h o s e emp loyed i n s t u d i e s o f a c u t e c a r d i o v a s c u l a r r e a c t i v i t y , r e s e a r c h e r s have a t t e m p t e d t o a s s o c i a t e i n d i v i d u a l - s p e c i f i c and s t i m u l u s - s p e c i f i c c h a r a c t e r i s t i c s w i t h p o t e n t i a l l y p a t h o g e n i c p a t t e r n s o f p h y s i o l o g i c h a b i t u a t i o n . The e l e c t r o d e r m a l r e s p o n s e r e p r e s e n t s t h e most e x t e n s i v e l y r e s e a r c h e d p h y s i o l o g i c r e s p o n s e s y s t em (O 'Go rman , 1 9 7 7 ) . Much l e s s e v i d e n c e e x i s t s as t o t h e r e l a t i o n s h i p between c o r o n a r y d i s e a s e and c a r d i o v a s c u l a r r e s p o n s e h a b i t u a t i o n . G e n e r a l l y , s t u d i e s o f p e r s o n a l i t y and c a r d i o v a s c u l a r h a b i t u a t i o n have y i e l d e d _ 4 -i n c o n c l u s i v e r e s u l t s ( c f . O'Gorman, 1977). Age and aerobic f i t n e s s l e v e l have been a s s o c i a t e d w i t h p o s t - s t r e s s p h y s i o l o g i c recovery r a t e s , however n e i t h e r f a c t o r has been r e l a t e d to w i t h i n task h a b i t u a t i o n . With regard to gender d i f f e r e n c e s i n c a r d i o v a s c u l a r h a b i t u a t i o n , measures of heart r a t e and blood pressure h a b i t u a t i o n have not been reported. In an extensive review O'Gorman (1977) concluded that subject s t r e s s task mentation d i d not exert a strong i n f l u e n c e on electrodermal h a b i t u a t i o n . S i m i l a r s t u d i e s i n v o l v i n g c a r d i o v a s c u l a r response measures were not reported. The r o l e of task c h a r a c t e r i s t i c s i n c a r d i o v a s c u l a r h a b i t u a t i o n has been only p a r t i a l l y assessed. Factors such as stimulus complexity, i n t e r - s t i m u l u s i n t e r v a l , and stimulus duration have been i m p l i c a t e d as probable mediators of response h a b i t u a t i o n . The s i g n a l - v a l u e and s u b j e c t i v e importance of the s t r e s s task has been r e l a t e d to delayed response h a b i t u a t i o n (Iacono & Lykken, 1984). H a b i t u a t i o n of heart r a t e responses has been demonstrated across i n t e r - s t i m u l u s i n t e r v a l s ranging from a few minutes to four weeks. I n t e r v a l s ranging from two months to four years have been shown to produce l i t t l e or no r e t e n t i o n of h a b i t u a t i o n e f f e c t s (Manuck & Garland, 1980). L i t t l e evidence e x i s t s however as to the s p e c i f i c e f f e c t of c o g n i t i v e s t r e s s o r c h a r a c t e r i s t i c s on h a b i t u a t i o n of blood pressure responses. Acute c a r d i o v a s c u l a r r e a c t i v i t y and repeated exposure to s t r e s s have each been separately i m p l i c a t e d as probable exacerbators of the pathogenesis of coronary heart disease. The r e l a t i o n s h i p between acute p h y s i o l o g i c hyperresponsiveness and h a b i t u a t i o n of responses to a repeated c o g n i t i v e s t r e s s o r has not been thoroughly examined. The present study examines low r e a c t i v e versus hype r r e a c t i v e female subjects f o r p o t e n t i a l l y maladaptive patterns of c a r d i o v a s c u l a r response h a b i t u a t i o n across varying i n t e r - s t r e s s o r i n t e r v a l s . - 5 -LITERATURE REVIEW B a s i c C a r d i o p h y s i o l o g y The s t u d y o f s i n g l e r e s p o n s e s su ch as b l o o d p r e s s u r e o r h e a r t r a t e r e s p o n s e s t o a g i v e n s t i m u l u s can a t b e s t p r o v i d e o n l y an i n c o m p l e t e p i c t u r e o f b a s i c c a r d i o v a s c u l a r p s y c h o p h y s i o l o g y i n an i n t a c t f u n c t i o n i n g i n d i v i d u a l . A p e r s o n ' s a d j u s t m e n t t o h i s o r h e r e n v i r o n m e n t i n v o l v e s s h i f t i n g p a t t e r n s o f i n t e g r a t e d somatomoto r , p h y s i o l o g i c a l , and n e u r o e n d o c r i n e b e h a v i o r s t h a t a r e a p p r o p r i a t e t o a g i v e n p e r s o n - e n v i r o n m e n t i n t e r a c t i o n . T h u s , a c omp rehens i v e a p p r o a c h t o c a r d i o v a s c u l a r p s y c h o p h y s i o l o g y i n v o l v e s t h e d e t e r m i n a t i o n o f w h i c h p a t t e r n s o f m u l t i p l e r e s p o n s e measures r e l i a b l y o c c u r i n a s s o c i a t i o n w i t h a g i v e n t y p e o f p e r s o n - e n v i r o n m e n t i n t e r a c t i o n . B a s i c a s p e c t s o f c a r d i o v a s c u l a r mechan isms and p h y s i o l o g y a r e b r i e f l y r e v i e w e d i n t h e f o l l o w i n g s e c t i o n . An u n d e r s t a n d i n g o f t h e s e b a s i c p r i n c i p l e s i s a n e c e s s a r y p r e c u r s o r t o a r e v i e w and d i s c u s s i o n o f t h e c a r d i o v a s c u l a r r e s p o n s e s a s s o c i a t e d w i t h a g i v e n i n d i v i d u a l i n r e s p o n s e t o a g i v e n s t r e s s o r . The f i r s t , and s i m p l e s t , p r i n c i p l e i s t h a t t he p r i m a r y f u n c t i o n o f t h e c a r d i o v a s c u l a r s y s t em i s t o meet t h e m e t a b o l i c needs o f v a r i o u s body t i s s u e s and o r g a n s . T h i s f u n c t i o n i n v o l v e s t h e d e l i v e r y o f o x y g e n , n u t r i e n t s , e l e c t r o l y t e s , v i t a m i n s , and t h e r emova l o f was te m a t e r i a l s . The key a s p e c t o f t h i s s y s t e m i s t h e ma i n t enance o f a r a t e o f b l o o d f l o w t o t i s s u e s t h a t i s c o n s i s t e n t w i t h t h e i r m e t a b o l i c n e e d s . The means by w h i c h t h e c a r d i o v a s c u l a r s y s t em f u n c t i o n s i n an i n t e g r a t e d manner t o meet t h e s e m e t a b o l i c needs i s e x t r e m e l y c omp l e x . Changes i n c a r d i a c o u t p u t and d i s t r i b u t i o n a r e r e g u l a t e d on b o t h a c e l l u l a r and a c o r t i c a l l e v e l . The hypo tha l amus and b r a i n s tem f u n c t i o n as t h e i n t e g r a t i n g c e n t r e f o r n e u r o g e n i c c a r d i o v a s c u l a r c o n t r o l . The e f f e r e n t - 6 -l i m b o f n e u r a l c o n t r o l i n v o l v e s changes i n s y m p a t h e t i c and p a r a s y m p a t h e t i c n e r v o u s s y s t em m e d i a t i o n . The re i s a l s o an a f f e r e n t f e e dba c k mechan ism w h i c h p r o v i d e s i n f o r m a t i o n abou t t h e s t a t u s o f t h e c a r d i o v a s c u l a r s y s t e m v i a m e c h a n o - p r e s s o r . a n d c h e m o r e c e p t o r s t h r o u g h o u t t h e body . B l o o d p r e s s u r e i s d e t e r m i n e d by t h e p r o d u c t o f t h e c a r d i a c o u t p u t and t o t a l p e r i p h e r a l r e s i s t a n c e w h i c h a r e i n t u r n c o m p l e x l y d e t e r m i n e d by t h e v a r i o u s a f o r e m e n t i o n e d mechan i sms . I t s h o u l d be n o t e d t h a t t h e r e a r e q u a l i t a t i v e l y d i f f e r e n t mechan isms by w h i c h b e h a v i o r a l i n f l u e n c e s can a c t t o i n c r e a s e o r d e c r e a s e b l o o d p r e s s u r e . I n c r e a s e s i n b l o o d p r e s s u r e may be p r i m a r i l y due t o i n c r e a s e s i n c a r d i a c o u t p u t o r a l t e r n a t i v e l y t o an i n c r e a s e i n t o t a l p e r i p h e r a l r e s i s t a n c e . Changes i n b l o o d f l o w may however be i n d e p e n d e n t o f changes i n c a r d i a c o u t p u t . I n c r e a s e s o r d e c r e a s e s i n b l o o d f l o w a r e g e n e r a t e d by bo t h a c t i v e and p a s s i v e mechan i sms . A c t i v e i n c r e a s e s i n b l o o d f l o w a r e a c h i e v e d by means o f i n c r e a s e d s y m p a t h e t i c n e r v e s t i m u l a t i o n o f a l p h a r e c e p t o r s i n a r t e r i a l smooth m u s c l e . B e t a - a d r e n e r g i c s t i m u l a t i o n , by c i r c u l a t i n g e p i n e p h r i n e , r e s u l t s i n a c t i v e v a s o d i l a t i o n and a d e c r e a s e i n b l o o d p r e s s u r e . W i t h d r a w a l o f t h e i n f l u e n c e o f e i t h e r o f t h e s e s o u r c e s o f a c t i v e v a s o d i l a t i o n o r v a s o c o n s t r i c t i o n r e s u l t s i n a c o r r e s p o n d i n g c o u n t e r r e s p o n s e . S t r e s s and C a r d i o v a s c u l a r D i s e a s e Over t h e p a s t s e v e r a l decades numerous a u t h o r s have p r e s e n t e d e v i d e n c e o f a p o s i t i v e r e l a t i o n s h i p between m a l a d a p t i v e r e s p o n s e s t o s t r e s s and t h e deve l opment o f c o r o n a r y h e a r t d i s e a s e ( G l a s s , 1 9 7 6 ) . C a r d i o v a s c u l a r p a t h o l o g y has been a s s o c i a t e d w i t h b o t h an i n d i v i d u a l ' s i n i t i a l o r a c u t e r e s p o n s e t o s t r e s s and h i s o r he r c h r o n i c o r c o p i n g r e s p o n s e t o a g i v e n s t r e s s o r o v e r t i m e . Cannon (1932) a r gued t h a t r e p e a t e d o r p r o l o n g e d e l i c i t a t i o n o f s t r e s s r e s p o n s e s p r oduced p o t e n t i a l l y p a t h o g e n i c e f f e c t s . The n o t i o n t h a t o n e ' s - 7 -r e s p o n s e t o s t r e s s may p l a y a f u n d a m e n t a l r o l e i n t h e e t i o l o g y and deve l opmen t o f a v a r i e t y o f d i s o r d e r s , b o t h p s y c h o l o g i c a l and p h y s i o l o g i c a l i n n a t u r e , was f u r t h e r d e v e l o p e d by S e l y e ( 1 9 7 6 ) . More r e c e n t l y , G l i n e r , B e d i and H o r v a t h (1979 ) s u g g e s t e d t h a t a c u t e p s y c h o l o g i c a l s t r e s s o r s may evoke p o t e n t i a l l y p a t h o g e n i c c a r d i o v a s c u l a r r e a c t i o n s o f a magn i t ude and d u r a t i o n g r e a t e r t h a n t h a t r e q u i r e d t o meet e x i s t i n g m e t a b o l i c r e q u i r e m e n t s . The e v i d e n c e f o r a p o s i t i v e r e l a t i o n s h i p between a c u t e h y p e r r e a c t i v i t y and t he p a t h o g e n e s i s o f c a r d i o v a s c u l a r d i s e a s e i s r e v i e w e d i n t h e f o l l o w i n g s e c t i o n . C a r d i o v a s c u l a r R e a c t i v i t y and C o r o n a r y H e a r t D i s e a s e The re has been much r e s e a r c h on c a r d i o v a s c u l a r d i s o r d e r s , p h y s i o l o g i c a l r e a c t i v i t y and t h e p a t t e r n s o f p s y c h o p h y s i o l o g i c a l r e s p o n s e s seen i n r e s p o n s e t o e n v i r o n m e n t a l s t i m u l i ( B r o d , F e n c l , H e j l , & J i r k a , 1959; E n g e l & B i c k f o r d , 1961 ; K e y s , T a y l o r , B l a c k b u r n , B r o z e k , A n d e r s o n , & S imonsen , 1 9 7 1 ) . I t has been s u g g e s t e d t h a t p h y s i o l o g i c h y p e r r e a c t i v i t y t o e m o t i o n a l o r p s y c h o l o g i c a l s t r e s s may be a marke r f o r i n c r e a s e d r i s k o f c o r o n a r y p a t h o l o g y ( E l i o t , B u e l l , & D e m b r o s k i , 1982; O b r i s t , 1 9 8 1 ) . I n g e n e r a l , p h y s i o l o g i c a l h y p e r r e s p o n s e s appea r t o be a s s o c i a t e d w i t h an i n c r e a s e d i n c i d e n c e o f p s y c h o s o m a t i c d i s o r d e r s ( D e m b r o s k i , 1978; Manuck, H a r v e y , L e c h l e i t e r , & N e a l , 1978; S t e p t o e , M e l v i l l e , & R o s s , 1 9 8 4 ) . S t u d i e s o f b o t h a n i m a l s and humans s u g g e s t t h a t p o t e n t i a l l y p a t h o g e n i c p h y s i o l o g i c a l c o n d i t i o n s can be p roduced by s p e c i f i c t y p e s o f e n v i r o n m e n t a l s t i m u l i . L a r g e c a r d i o v a s c u l a r and n e u r o e n d o c r i n e r e s p o n s e s have been p r oduced (Cannon , 1936; F r a n k e n h a e u s e r , 1975; F r a n k e n h a e u s e r & J o h a n s s o n , 1976) i n r e s p o n s e t o b o t h n a t u r a l i s t i c and l a b o r a t o r y - i n d u c e d s h o r t - t e r m p s y c h o l o g i c a l s t r e s s o r s . I t s h o u l d be r e c o g n i z e d t h a t p h y s i o l o g i c a l r e a c t i v i t y t o s t r e s s r e s u l t s f r om a comp lex i n t e r a c t i o n o f b i o b e h a v i o r a l f a c t o r s ( W a t k i n s & Ro s e , i n p r e s s ) . Numerous a u t h o r s have a l s o r e c o g n i z e d t h a t p h y s i o l o g i c r e a c t i o n s t o 8 c h r o n i c s t r e s s a r e more v a r i a b l e and comp lex t h a n a c u t e r e s p o n s e s (Baum, G a t c h e l , & S c h a e f f e r , 1983; Manuck & K r a n t z , 1984; Mason , 1968; S e l y e , 1 9 7 6 ) . G i v e n t he p r e s e n t body o f e v i d e n c e , i t i s p l a u s i b l e t o s u g g e s t howeve r , t h a t r e s p o n s e s t o a c u t e s t i m u l i may have s i g n i f i c a n t e f f e c t s on t he p r o c e s s e s u n d e r l y i n g c h r o n i c c a r d i o v a s c u l a r d i s o r d e r s . As n o t e d by Manuck and K r a n t z ( 1984 ) f o u r p r i m a r y l i n e s o f e v i d e n c e s u p p o r t t h i s h y p o t h e s i s . These i n c l u d e d a t a f r om a n i m a l m o d e l s , p r o s p e c t i v e human s t u d i e s , r e t r o s p e c t i v e o r c a s e - c o n t r o l human s t u d i e s , and s t u d i e s o f Type A b e h a v i o r i n humans. Each o f t h e s e a r e a s o f e v i d e n c e i s r e v i e w e d i n t h e f o l l o w i n g s e c t i o n s . A n i m a l m o d e l s . The f i r s t t y p e o f e v i d e n c e l i n k i n g a c u t e r e a c t i v i t y t o c h r o n i c c o r o n a r y d i s e a s e i s t h a t f r om a n i m a l r e s e a r c h . Manuck, K a p l a n and C l a r k s o n ( 1 9 8 3 ) , i n a s t u d y o f b e h a v i o r a l l y - i n d u c e d h e a r t r a t e r e a c t i v i t y i n monkeys , f ound t h a t h i g h h e a r t r a t e r e a c t o r s d i s p l a y e d s i g n i f i c a n t l y g r e a t e r i n c i d e n c e o f c o r o n a r y a t h e r o s c l e r o s i s t h a n d i d low h e a r t r a t e r e a c t o r s . These f i n d i n g s p r o v i d e i n i t i a l s u p p o r t f o r t h e h y p o t h e s i s t h a t c a r d i o v a s c u l a r h y p e r r e s p o n s i v i t y under s t r e s s i s a p r e c u r s o r t o t h e deve l opmen t o f a t h e r o s c l e r o s i s and sub sequen t c o r o n a r y f a t a l i t y . Human s t u d i e s have n o t y e t c o r r o b o r a t e d t h i s f i n d i n g (Manuck & K r a n t z , 1 9 8 4 ) . P r o s p e c t i v e human s t u d i e s . I n a r e c e n t p r o s p e c t i v e s t u d y , W i l s o n and Meyer (1981 ) f ound t h a t t h e r e l a t i v e r i s k o f d e v e l o p i n g h y p e r t e n s i o n was 2 .28 t i m e s g r e a t e r i n t h o s e i n d i v i d u a l s e x h i b i t i n g a b l o o d p r e s s u r e h y p e r r e s p o n s e t o e x e r c i s e i n d u c e d s t r e s s . I n a p r o s p e c t i v e s t u d y w h i c h examined r e a c t i v i t y a s a p r e d i c t o r o f i n c i d e n c e o f c o r o n a r y p a t h o l o g y , Keys e t a l . ( 1971 ) f ound t h a t magn i t ude o f d i a s t o l i c b l o o d p r e s s u r e r e s p o n s e t o a c o l d p r e s s o r t a s k was a s i g n i f i c a n t p r e d i c t o r o f s ub sequen t c o r o n a r y h e a r t d i s e a s e . These f i n d i n g s were s u p p o r t e d by Wood, Sheps , E l v e b a c k , and S c h i n g e r (1984) who f ound t h a t r e a c t i v i t y t o a c o l d p r e s s o r t e s t was p r e d i c t i v e o f s ub sequen t h y p e r t e n s i o n . - 9 ~ Retrospective, case-control studies. Several retrospective or case-control studies comparing the psychophysiological responses of persons with and without coronary heart disease have been reported (Corse, Manuck, Cantwell, Giordani, & Matthews, 1982; Dembroski, MacDougall, & Lushene, 1979; Krantz, Schaeffer, Davia, Dembroski, MacDougall, & Schaeffer, 1981; Nestel, Verghese, & L o v e l l , 1967; Sime, B u e l l , & E l i o t , 1980; S h i f f e r , Hartley, Schulman, & Abelman, 1976). Most of these studies found a greater r e a c t i v i t y i n terms of blood pressure responses to laboratory stressors i n patients with previous h i s t o r i e s of angina or myocardial i n f a r c t i o n . Disconfirmatory results have however also been reported (Krantz et a l . , 1981). While case-control studies have revealed some suggestive evidence, a consistent association between a given measure of physiologic r e a c t i v i t y and a s p e c i f i c c l i n i c a l endpoint has not yet been established. Light (1981) found that parents of high heart reactors showed a greater incidence of essential hypertension. This finding supports the notion of a possible genetic or f a m i l i a l factor i n the process l i n k i n g acute r e a c t i v i t y to chronic coronary pathology. Type A studies. Research on the Type A or coronary-prone behavior pattern has stimulated much of the current interest i n the measurement of cardiovascular r e a c t i v i t y to stress. Type A persons are characterized as impatient, hard-driving, and ambitious (Matthews, Glass, Rosenman, & Bortner, 1977). The hypothesis has been suggested that the types of behaviors which are t y p i c a l of Type A individuals are related to pathogenic neuroendocrine and cardiovascular responses. These pathogenic responses are thought to l i n k psychosocial stressors to coronary heart disease. For example, Type A persons display heightened physiological responsiveness (Dembroski, 1978), greater catecholamine secretion (Levi, 1974), and vasoconstriction responses to - 10 -p s y c h o l o g i c a l s t r e s s ( W i l l i a m s , B i t t k e r , Buchsbaum, & Wynne, 1 9 7 5 ) . I n a r e c e n t r e v i e w (Manuck & K r a n t z , 1984) t h e a u t h o r s s u r v e y e d t h e r e s u l t s o f 37 s t u d i e s o f Type A and r e a c t i v i t y . T w e n t y - s i x s t u d i e s r e p o r t e d g r e a t e r r e a c t i v i t y t o s t r e s s among t y p e A s u b j e c t s . E l e v e n s t u d i e s r e p o r t e d no d i f f e r e n c e o r g r e a t e r r e a c t i v i t y by Type B s u b j e c t s . Manuck and K r a n t z ( 1984 ) c o n c l u d e t h a t t h e Type A b e h a v i o r p a t t e r n i s o n l y m o d e r a t e l y c o r r e l a t e d w i t h p h y s i o l o g i c a l h y p e r r e a c t i v i t y i n s p e c i f i c l a b o r a t o r y p a r a d i g m s . S y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y a p p e a r s t o be t h e most c o n s i s t e n t c o r r e l a t e o f Type A b e h a v i o r ( W r i g h t , C o n t r a d a , & G l a s s , i n p r e s s ) . I n d i v i d u a l D i f f e r e n c e s i n C a r d i o v a s c u l a r R e a c t i v i t y The r e a p p e a r s t o be a v a r i e t y o f i n d i v i d u a l - s p e c i f i c c h a r a c t e r i s t i c s t h a t a r e r e l a t e d t o t h e deg ree o f h y p e r r e a c t i v i t y w h i c h an i n d i v i d u a l d i s p l a y s i n r e s p o n s e t o a g i v e n s t r e s s o r ( c f . Manuck, M o r r i s o n , B e l l a c k , & P o l e f r o n e , i n p r e s s ) . S c h u l t e , F r i e d r i c h , R u d d e l , S c h i r m e r , and von E i f f ( 1981 ) a r gue t h a t t h e l a r g e s t p r o p o r t i o n o f t h e v a r i a n c e i n p s y c h o p h y s i o l o g i c a l r e a c t i v i t y s een a c r o s s i n d i v i d u a l s can be a t t r i b u t e d t o i n d i v i d u a l - s p e c i f i c c h a r a c t e r i s t i c s . E n g e l and B i c k f o r d ( 1 9 6 1 ) , f o r e xamp l e , f ound w i de i n d i v i d u a l d i f f e r e n c e s i n au t onom i c n e r v o u s s y s t e m r e s p o n s e s t o e m o t i o n a l s t r e s s . The t endency f o r some p e r s o n s t o d i s p l a y a c h a r a c t e r i s t i c c a r d i o v a s c u l a r h y p e r r e a c t i v i t y t o e m o t i o n a l s t r e s s has a l s o been e s t a b l i s h e d ( F a l k n e r , O n e s t i , A n g e l a k o s , F e r n a n d e s , & Langmann, 1979; E l i o t e t a l . , 1982; O b r i s t , 1 9 8 1 ) . K r a n t z and Manuck (1984 ) r e v i e w e d f i v e s t u d i e s i n an a n a l y s i s o f t h e c o r r e l a t i o n between h e a r t r a t e and b l o o d p r e s s u r e change s c o r e s w i t h i n i n d i v i d u a l s a c r o s s a v a r i e t y o f s t r e s s t a s k s . These d a t a a r e p r e s e n t e d i n T a b l e 1. The a u t h o r s f ound t h a t most o f t h e i n t e r - t a s k c o r r e l a t i o n s were s i g n i f i c a n t i n d i c a t i n g t h a t t h e r e was a s h a r e d v a r i a n c e i n r e a c t i v i t y as a s t a b l e , i n d i v i d u a l - s p e c i f i c c h a r a c t e r i s t i c a c r o s s t a s k s . However , t h e a u t h o r s n o t e - 11 -TABLE 1* C o r r e l a t i o n s Among Change Scores on Cardiovascular Measures  (Task Mean Minus B a s e l i n e ) Study/subject Stressor/procedure SBP DBP HR Dembroski (personal communication, 1983) College students Mental a r i t h m e t i c / .57 .62 .44 s t r u c t u r e d i n t e r v i e w Manuck & Garland (1979) College students C o g n i t i v e test/mental .50 .23 (ns) .86 H i l l & Krantz (1983) Medical students Reaction t i m e / s t r u c t u r e d .54 .60 .57 i n t e r v i e w Reaction time/medical quiz .54 .66 .53 Medical q u i z / s t r u c t u r e d .74 .60 .81 i n t e r v i e w Dembroski (personal communication, 1983) Executives Video game/1 minute c o l d .79 .62 .49 pressor Video game/reaction time .73 .74 .67 Reaction time/1 minute c o l d .70 .53 .43 pressor Glass et a l . (1983) B l u e - c o l l a r working males Stroop color-word a/mental .69 .47 .45 a r i t h m e t i c Note. C o r r e l a t i o n s are s t a t i s t i c a l l y r e l i a b l e unless i n d i c a t e d ( n s ) . SBP = s y s t o l i c blood pressure; DBP = d i a s t o l i c blood pressure; HR = heart r a t e . a S t r o o p task was administered at second session 2 months l a t e r . *Taken from Krantz & Manuck, 1984. - 12 -t h a t t h e s t r e n g t h o f r e l a t i o n s between t he a s s e s s e d change s c o r e s can be c h a r a c t e r i z e d as m o d e r a t e . T h i s d i s p o s i t i o n t owa r d s h y p e r r e a c t i v i t y c o n c e i v a b l y a r i s e s f r om e i t h e r h e r e d i t a r y o r p s y c h o s o c i a l f o r c e s o r some i n t e r a c t i o n o f t h e s e . Kagan ( 1 9 8 4 ) , f o r e xamp l e , r e p o r t e d t h a t n e o n a t e s d i s p l a y d i f f e r e n t t h r e s h o l d s o f v u l n e r a b i l i t y t o s t r e s s . Some neona t e s may be c l a s s e d as h i g h r e a c t o r s on t he b a s i s o f t h e magn i t ude o f t h e i r h e a r t r a t e and s y m p a t h e t i c n e r v o u s s y s t e m r e s p o n s e s t o s t r e s s . Response s t e r e o t y p y . The v a r i a b i l i t y i n magn i t ude and p a t t e r n o f a u t onom i c r e s p o n s e s t o s t r e s s a c r o s s i n d i v i d u a l s has been t e rmed i n d i v i d u a l r e s p o n s e s t e r e o t y p y o r i n d i v i d u a l r e s p o n s e s p e c i f i c i t y . I n d i v i d u a l r e s p o n s e s t e r e o t y p y has been d e f i n e d as " t h e h a b i t u a l d i s p o s i t i o n o f an i n d i v i d u a l t o e x h i b i t a s i m i l a r r e s p o n s e p a t t e r n t o v a r i o u s s t i m u l i o r s i t u a t i o n s " ( F o e r s t e r , S c h n e i d e r , & W a l s c h b u r g e r , 1 9 8 3 ) . Response s t e r e o t y p y has been s t u d i e d t h r o u g h t h e c o m p a r i s o n o f i n d i v i d u a l d i f f e r e n c e s i n r e s p o n s e t o s t r e s s under c o n t r o l l e d e x p e r i m e n t a l c o n d i t i o n s . I t has a l s o been s t u d i e d by c ompa r i n g t h e p s y c h o p h y s i o l o g i c a l c h a r a c t e r i s t i c s o f i n d i v i d u a l s d i s p l a y i n g a d a p t i v e p a t t e r n s o f r e s p o n s e s p e c i f i c i t y w i t h t h o s e d i s p l a y i n g p o t e n t i a l l y m a l a d a p t i v e p a t t e r n s . I n t h e f o l l o w i n g two s e c t i o n s e v i d e n c e r e g a r d i n g i n d i v i d u a l - s p e c i f i c p s y c h o l o g i c a l and p h y s i o l o g i c a l m e d i a t o r s o f r e a c t i v i t y i s r e v i e w e d . P s y c h o l o g i c a l m e d i a t o r s o f r e a c t i v i t y . Numerous a u t h o r s have a t t e m p t e d t o c h a r a c t e r i z e and d i s t i n g u i s h v a r i o u s g r oup s o f i n d i v i d u a l s on t h e b a s i s o f t h e i r members e x h i b i t i n g common p s y c h o p h y s i o l o g i c a l r e s p o n s e s t o s t r e s s ( G r o v e s e t a l . , 1982; Manuck & G a r l a n d , 1 9 8 0 ) . C e r t a i n p h y s i o l o g i c a l r e s p o n s e p a t t e r n s have been v a r i o u s l y c h a r a c t e r i z e d as b e i n g t y p i c a l o f i n t r o v e r s i o n - e x t r o v e r s i o n ( H i n t o n & C r a s k e , 1 9 7 7 ) , Type A b e h a v i o r (Demb ro sk i - 13 -e t a l . , 1 9 7 8 ) , l e v e l l i n g - s h a r p e n i n g ( I s r a e l , 1 9 6 9 ) , n e u r o t i c i s m ( E y s e n c k , 1 9 6 7 ) , f i e l d i n dependen ce v e r s u s f i e l d dependence ( G r o v e s e t a l . , 1 9 8 2 ) , and l o c u s o f c o n t r o l ( H a r r e l , 1 9 8 0 ) . G e n e r a l l y , h i g h h e a r t r a t e r e a c t i v i t y i s a s s o c i a t e d w i t h h i g h e r l e v e l s o f i n t r o v e r s i o n , n e u r o t i c i s m , l e v e l l i n g o r i g n o r i n g c e r t a i n s t i m u l u s a s p e c t s , f i e l d dependence , e x t e r n a l l o c u s o f c o n t r o l , and Type A b e h a v i o r . O t he r r e c e n t r e p o r t s s u g g e s t t h a t i n d i v i d u a l d i f f e r e n c e s s u ch as deg ree o f s e l f - i n v o l v e m e n t ( S c h e r w i t z , B e r t o n , & L e v e n t h a l , 1 9 7 8 ) , and o r s e l f - r e p o r t e d ange r ( G l a s s , L a k e , C o n t r a d a , Kehoe , & E r l a n g e r , 1983) a l s o r e l a t e t o l e v e l o f h e a r t r a t e r e a c t i v i t y . P h y s i o l o g i c a l M e d i a t o r s o f R e a c t i v i t y . A t t e m p t s t o i d e n t i f y s ubg roups o f i n d i v i d u a l s on t he b a s i s o f common b i o l o g i c a l c h a r a c t e r i s t i c s su ch a s gender .or a g e , o r on t he b a s i s o f a common p h y s i o l o g i c a l r e s p o n s e p a t t e r n under c o n d i t i o n s o f p s y c h o l o g i c a l s t r e s s have a l s o been made. I n t e rms o f t h e i r p h y s i o l o g i c a l r e s p o n s e p a t t e r n g r oups have been v a r i o u s l y d i s c r i m i n a t e d on t h e b a s i s o f b l o o d p r e s s u r e , h e a r t r a t e , and au t onom i c n e r v o u s s y s t e m r e a c t i v i t y . P a t t o n ( 1 9 6 9 ) , f o r e xamp l e , c l a s s i f i e d s u b j e c t s a s e i t h e r s y m p a t h e t i c r e a c t o r s o r p a r a s y m p a t h e t i c r e a c t o r s on t h e b a s i s o f t h e r e l a t i v e deg ree o f s y m p a t h e t i c o r p a r a s y m p a t h e t i c a r o u s a l d i s p l a y e d a t r e s t . S y m p a t h e t i c r e a c t o r s showed g r e a t e r i n c r e a s e s i n b l o o d p r e s s u r e and h e a r t r a t e under a v a r i e t y o f s t r e s s o r c o n d i t i o n s . A s y s t o l i c h y p e r r e s p o n s e t o a p s y c h o l o g i c a l s t r e s s o r has a l s o been f ound t o d i s t i n g u i s h m i l d h y p e r t e n s i v e s f r om n o r m a l c o n t r o l s ( E n g e l & B i c k f o r d , 1961 ; L i n d e n & F e u e r s t e i n , 1983; O h l s s o n & H e n n i n g s e n , 1 9 8 2 ) . H e a r t r a t e , howeve r , was no t s i g n i f i c a n t l y d i f f e r e n t i n m i l d h y p e r t e n s i v e s v e r s u s c o n t r o l s e i t h e r a t r e s t , o r d u r i n g v a r i o u s s t r e s s t a s k s . Mos t d a t a on r e a c t i v i t y have been c o l l e c t e d f r om homogeneous s a m p l e s , u s u a l l y composed o f w h i t e m a l e , c o l l e g e s t u d e n t v o l u n t e e r s o r matched c o r o n a r y p a t i e n t and n o n - p a t i e n t s amp l e s ( K r a n t z & Manuck, 1 9 8 4 ) . On l y r e c e n t l y have _ 14 _ r e s e a r c h e r s begun t o a s s e s s t h e c o m p a r a t i v e c a r d i o v a s c u l a r r e a c t i v i t y o f p e r s o n s d i f f e r i n g i n g e n d e r , a g e , s o c i o e c o n o m i c s t a t u s , and e t h n i c i t y . W i t h r e s p e c t t o g ende r , i t has been commonly o b s e r v e d t h a t r e s t i n g b l o o d p r e s s u r e l e v e l s a r e l owe r i n women t h a n i n men u n t i l abou t 50-60 y e a r s o f a g e , a f t e r w h i c h b l o o d p r e s s u r e and t he i n c i d e n c e o f c o r o n a r y h e a r t d i s e a s e and e s s e n t i a l h y p e r t e n s i o n r i s e s m a r k e d l y i n women ( B o y l e , G r i f f e y , N i chaman , & T a l b e r t , 1 9 7 6 ) . I n p s y c h o p h y s i o l o g i c s t u d i e s , women have been r e p o r t e d t o d i s p l a y l e s s p ronounced c a t e c h o l a m i n e and c a r d i o v a s c u l a r r e s p o n s i v i t y t o b e h a v i o r a l s t i m u l i t h a n do men ( F r a n k e n h a e u s e r , 1 9 8 3 ) . O the r a u t h o r s , howeve r , have r e p o r t e d h i g h e r l e v e l s o f h e a r t r a t e ( C o l l i n s & F r a n k e n h a e u s e r , 1978) and s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y (Forsman & L i n b l a d , 1983) t o a c o g n i t i v e s t r e s s t a s k among f e m a l e s u b j e c t s . H a s t r u p , L i g h t , and O b r i s t ( 1980 ) a r gue t h a t t h i s v a r i a n c e i n f e m a l e c a r d i o v a s c u l a r r e a c t i v i t y may be a c c o u n t e d f o r by v a r i a t i o n s i n hormone l e v e l s c o i n c i d i n g w i t h s p e c i f i c phases o f t h e m e n s t r u a l c y c l e . These a u t h o r s f ound d e c r e a s e d c a r d i o v a s c u l a r r e a c t i v i t y d u r i n g t h e p r e - o v u l a t o r y p ha s e . T h i s f i n d i n g o f m e n s t r u a l p h a s e - s p e c i f i c r e s p o n s i v i t y has been r e f u t e d by o t h e r s who have f ound no r e l i a b l e v a r i a t i o n s i n c a r d i o v a s c u l a r r e a c t i v i t y a s a f u n c t i o n o f m e n s t r u a l phase ( A s s o , 1978; S t r a u s s , S c h u l t h e i s s , & Cohen , 1 9 8 3 ) . C a r r o l l , T u r n e r , L e e , and S t ephenson (1984) have r e p o r t e d i n d i v i d u a l - s p e c i f i c s t a b i l i t y o f c a r d i o v a s c u l a r r e a c t i v i t y a c r o s s m e n s t r u a l c y c l e s . F i n a l l y , s i m i l a r i t i e s i n magn i t ude o f c a r d i o v a s c u l a r r e a c t i v i t y among t w i n s have a l s o been r e p o r t e d ( R o s e , G r i m , & M i l l e r , 1 9 8 4 ) . Da t a d i s t i n g u i s h i n g same gender v e r s u s c r o s s gender t w i n s were n o t r e p o r t e d . Some a u t h o r s have s u g g e s t e d t h a t e l d e r l y i n d i v i d u a l s appea r l e s s r e a c t i v e t h a n young a d u l t s on h e a r t r a t e r e s p o n s e m e a s u r e s . T h i s d e c r e a s e d r e a c t i v i t y i s p o s t u l a t e d t o be due t o a d e c r e a s e d s e n s i t i v i t y t o b e t a - a d r e n e r g i c - 15 " s t i m u l a t i o n . The n o t i o n o f d e c r e a s e d b e t a - a d r e n e r g i c s e n s i t i v i t y has i n t u r n , been s u b s t a n t i a t e d by t h e f a c t t h a t s e n s i t i v i t y t o d r u g - i n d u c e d b e t a - a d r e n e r g i c s t i m u l a t i o n a p p e a r s t o d e c l i n e w i t h a d v a n c i n g age ( B u h l e r , K i o s k i , van Brummelen , Amann, B e r t e l , Landmann, L u t o l d , & B o l l i , 1 9 8 0 ) . Task I n f l u e n c e s S t i m u l u s s p e c i f i c i t y . I n s p i t e o f s t r o n g e v i d e n c e t h a t t h e r e i s a l e v e l and p a t t e r n o f c a r d i o v a s c u l a r f u n c t i o n under s t r e s s t h a t t e n d s t o be c h a r a c t e r i s t i c o f an i n d i v i d u a l ( F a h r e n b e r g , W a l s c h b u r g e r , F o e r s t e r , M y r t e k , & M u l l e r , 1979) a number o f s t u d i e s have f ound t h a t r e s p o n s e s t e r e o t y p y a c c o u n t s f o r o n l y a modest p o r t i o n o f t h e v a r i a n c e seen i n an i n d i v i d u a l ' s p h y s i o l o g i c a l r e s p o n s e s t o s t r e s s . F o e r s t e r e t a l . ( 1 9 8 3 ) , f o r e xamp l e , f ound t h a t o n l y 23% - 29% o f t h e r e s p o n s e v a r i a n c e i n p h y s i o l o g i c a l measures c o u l d be a t t r i b u t e d t o i n d i v i d u a l - s p e c i f i c f a c t o r s a c r o s s d i f f e r e n t s t r e s s o r c o n d i t i o n s . F ou r s t u d i e s u sed a measure o f r e s p o n s e c on c o r d an c e a c r o s s s i t u a t i o n s i n a t t e m p t i n g t o e s t i m a t e t h e p e r c e n t a g e o f s u b j e c t s show ing an i n d i v i d u a l -s p e c i f i c r e s p o n s e ( E n g e l , 1960; K n o b l o c h & K n o b l o c h , 1979; F o e r s t e r e t a l . , 1983; F o e r s t e r e t a l . , 1 9 8 3 b ) . These s t u d i e s f ound a h i g h deg ree o f s i m i l a r i t y i n t h e amount o f v a r i a n c e a s s o c i a t e d w i t h an i n d i v i d u a l - s p e c i f i c r e s p o n s e . However , t h e y a l s o r e v e a l e d t h e e x i s t e n c e o f c o n s i d e r a b l e u n e x p l a i n e d v a r i a b i l i t y . T h i s a d d i t i o n a l v a r i a n c e has been a t t r i b u t e d t o what has been te rmed s i t u a t i o n a l s t e r e o t y p y ( L a c e y , 1 9 6 7 ) . The s t i m u l u s - s p e c i f i c o r s i t u a t i o n - s t e r e o t y p e r e s p o n s e has been d e f i n e d as a t e n d e n c y f o r s p e c i f i c s t i m u l i t o e l i c i t u n i f o r m and c o n s i s t e n t r e s p o n s e p a t t e r n s a c r o s s i n d i v i d u a l s ( L a c e y , 1967; F o e r s t e r e t a l . , 1 9 8 3 ) . F o r t h e p a s t s e v e r a l decades r e s e a r c h e r s have a t t e m p t e d t o i d e n t i f y t h e r e l a t i o n s h i p between s t i m u l u s c h a r a c t e r i s t i c s and s p e c i f i c c a r d i o v a s c u l a r r e s p o n s e p a t t e r n s ( L a c e y & L a c e y , - 16 -1966; O b r i s t , 1981 ; L i n d e n e t a l . , i n p r e s s ) . C l a s s i f i c a t i o n o f s t r e s s o r s . The r e s e a r c h l i t e r a t u r e on methods f o r c l a s s i f y i n g s t i m u l i a s s o c i a t e d w i t h c a r d i o v a s c u l a r r e s p o n s e measu res i n e x p e r i m e n t a l s t r e s s r e s e a r c h i s r e v i e w e d i n t h e f o l l o w i n g s e c t i o n . Th r ee ma jo r t h e o r e t i c a l c o n c e p t u a l i z a t i o n s : s e n s o r y i n t a k e v e r s u s s e n s o r y r e j e c t i o n ( L a c e y , K agan , L a c e y , & Moss , 1 9 6 3 ) , a c t i v e v e r s u s p a s s i v e c o p i n g ( O b r i s t , G a b e l e i n , T e l l e r , L a n g e r , G r i g n o l o , L i g h t , & McCubb i n , 1 9 7 8 ) , and e ngagemen t - i n v o l v emen t ( W i l l i a m s , F r a n k e l , G i l l i n , & W e i s s , 1973) a r e r e v i e w e d . S e n s o r y i n t a k e v e r s u s s e n s o r y r e j e c t i o n . The e a r l i e s t p r e s e n t a t i o n o f what has been t e rmed t h e L a c e y s ' a t t e n t i o n a l h y p o t h e s i s ( L a c e y e t a l . , 1963) d e s c r i b e d an a s s o c i a t i o n between c a r d i a c a c c e l e r a t i o n o r d e c e l e r a t i o n and f o c u s o f a t t e n t i o n . I n s e v e r a l s ub sequen t e x p e r i m e n t s ( L a c e y , 1967; L a c e y & L a c e y , 1966; L i b b y , L a c e y , & L a c e y , 1973) t h e L a c e y s and t h e i r c o l l e a g u e s c o n f i r m e d t h a t h e a r t r a t e d e c e l e r a t e d i n s i t u a t i o n s where t h e s u b j e c t was r e q u i r e d t o a t t e n d t o s i m p l e a u d i t o r y o r v i s u a l s t i m u l i . These s t i m u l i were t e rmed " s e n s o r y i n t a k e " s t i m u l i . I n s i t u a t i o n s where t h e s u b j e c t was r e q u i r e d t o engage i n more e l a b o r a t e c o g n i t i v e a c t i v i t i e s an a c c e l e r a t i o n i n h e a r t r a t e was o b s e r v e d . The s t i m u l i a s s o c i a t e d w i t h t h i s p a t t e r n o f r e s p o n s e were te rmed " s e n s o r y r e j e c t i o n " s t i m u l i . T h i s g roup o f s t i m u l i i n c l u d e n o x i o u s s t i m u l i and t h o s e i n v o l v i n g r e t r i e v a l o f s t o r e d i n f o r m a t i o n , m e n t a l c o n c e n t r a t i o n and p r ob l em s o l v i n g . I n g e n e r a l , s e n s o r y r e j e c t i o n s t i m u l i p r oduce b l o o d p r e s s u r e and h e a r t r a t e i n c r e a s e s i n d i c a t i v e o f h e i g h t e n e d s y m p a t h e t i c a r o u s a l ( L a c e y , 1 9 6 7 ) . The a f o r e m e n t i o n e d f i n d i n g s a r e i m p o r t a n t f o r a number o f r e a s o n s . F i r s t , L a c ey ( 1967 ) c h a l l e n g e d t h e c o n c e p t o f n o n - s p e c i f i c a r o u s a l ( S e l y e , 1976) by s u g g e s t i n g t h a t a s u b j e c t ' s p h y s i o l o g i c a l r e s p o n s e p a t t e r n was i n l a r g e p a r t , a f u n c t i o n o f t h e t y p e o f s t i m u l u s i n v o l v e d . P r o p o n e n t s o f t r a d i t i o n a l - 17 _ a r o u s a l t h e o r y ( D u f f y , 1962) wou ld p r e d i c t f o r example t h a t t h e h a r d e r t h e t a s k , t h e g r e a t e r t h e p h y s i o l o g i c a l a r o u s a l , and h en c e , t h e h i g h e r t h e h e a r t r a t e s h o u l d b e . L a c ey (1967 ) a r gued t h a t a r o u s a l may no t be a u n i t a r y , a l l - o r - n o n e phenomenon w h i c h i s s o l e l y r e s p o n s i v e t o s t i m u l u s i n t e n s i t y . L a c e y ' s v i e w p o i n t i s s u p p o r t e d by a s t u d y by C o l e s (1972 ) i n w h i c h t h e a u t h o r f ound t he c a r d i a c d e c e l e r a t o r y r e s p o n s e t o be g r e a t e r d u r i n g a h a r d t h a n d u r i n g an e a sy s e n s o r y i n t a k e t a s k . The L a c e y s ' r e s u l t s a r e a l s o c o n s i s t e n t w i t h t h e c o n c e p t o f " d i r e c t i o n a l f r a c t i o n a t i o n " o f r e s p o n s e mea su r e s . S i m p l y p u t , d i r e c t i o n a l f r a c t i o n a t i o n r e f e r s t o t h e e x i s t e n c e o f low c o r r e l a t i o n s between v a r i o u s body s y s t em r e s p o n s e m e a s u r e s . L a c ey (1967 ) f ound f o r e xamp l e , t h a t s e n s o r y i n t a k e s t i m u l i p r oduced h e a r t r a t e and b l o o d p r e s s u r e d e c r e a s e s a c compan i ed by an i n c r e a s e i n s k i n c ondu c t an c e and p u p i l d i a m e t e r . On t h e b a s i s o f t h i s e a r l i e r work by t h e L a c e y s ( L a c ey & L a c e y , 1 9 7 0 ) , W i l l i a m s ( i n p r e s s ) p r opo sed t h a t s e n s o r y i n t a k e and s e n s o r y r e j e c t i o n a r e a c compan i ed by d i s t i n c t and c o n s i s t e n t p h y s i o l o g i c r e s p o n s e p a t t e r n s . A c c o r d i n g t o W i l l i a m s ' v i e w p o i n t when a s t i m u l u s s u ch as a m e n t a l a r i t h m e t i c t a s k r e q u i r e s s e n s o r y r e j e c t i o n t h e d e f e n s e r e a c t i o n i s a c t i v a t e d . T h i s r e a c t i o n i s c h a r a c t e r i z e d by e m o t i o n a l a r o u s a l , and a c a r d i o v a s c u l a r r e s p o n s e p a t t e r n o f i n c r e a s e d c a r d i a c o u t p u t . When s e n s o r y i n t a k e o r a t t e n t i o n t o t h e e n v i r o n m e n t i s r e q u i r e d a d i f f e r e n t r e s p o n s e p a t t e r n i s e l i c i t e d . T h i s p a t t e r n , t y p i c a l o f r e s p o n s e s t o r e a c t i o n t i m e t a s k s ( L a c ey & L a c e y , 1974; N o w l i n , Thompson, & E i s d o r f e r , 1969) i s c h a r a c t e r i z e d by d e c r e a s e d e m o t i o n a l a r o u s a l , d e c r e a s e d h e a r t r a t e and c a r d i a c o u t p u t , d e c r e a s e d motor a c t i v i t y and i n c r e a s e d s k e l e t a l mus c l e v a s o c o n s t r i c t i o n ( W i l l i a m s , B i t t k e r , Buchsbaum, & Wynne, 1 9 7 5 ) . A c t i v e v e r s u s p a s s i v e c o p i n g . O b r i s t and h i s c o l l e a g u e s d e f i n e a s t i m u l u s - 18 -i n t e rms o f t h e t y p e o f " c o p i n g s t y l e " w h i c h i t e l i c i t s f r om a g i v e n i n d i v i d u a l ( O b r i s t e t a l . , 1 9 7 8 ) . O b r i s t h y p o t h e s i z e d t h a t a c r u c i a l q u a l i t a t i v e f e a t u r e o f s t r e s s f u l t a s k s i s whe the r s u b j e c t s a c t i v e l y o r p a s s i v e l y cope w i t h s t r e s s . P a s s i v e c o p i n g i s e x e m p l i f i e d by t h e p a t t e r n o f r e s p o n s e s p r oduced by s t r e s s o r s s u c h a s t h e c o l d p r e s s o r t e s t o r a p o r n o g r a p h i c f i l m w h i c h s u b j e c t s t o l e r a t e p a s s i v e l y . S t i m u l i s u ch as t h e s e a r e a s s o c i a t e d w i t h s i g n i f i c a n t i n c r e a s e s i n d i a s t o l i c b l o o d p r e s s u r e and l e s s e r changes i n h e a r t r a t e and s y s t o l i c b l o o d p r e s s u r e . O b r i s t e t a l . ( 1978 ) f ound t h a t d u r i n g p a s s i v e c o p i n g c o n d i t i o n s b e t a - a d r e n e r g i c , i . e . , a c c e l e r a t i v e i n f l u e n c e s on h e a r t r a t e were e i t h e r m i n i m a l o r were r a p i d l y d i s s i p a t e d . On t h e o t h e r h and , O b r i s t e t a l . ( 1978 ) f ound t h a t c e r t a i n k i n d s o f s t r e s s f u l t a s k s were more l i k e l y t o e l i c i t a c a r d i o v a s c u l a r r e s p o n s e p a t t e r n i n d i c a t i v e o f s t r o n g b e t a - a d r e n e r g i c i n f l u e n c e s on t h e h e a r t . These i n f l u e n c e s a r e r e f l e c t e d i n s i g n i f i c a n t i n c r e a s e s i n s y s t o l i c b l o o d p r e s s u r e and h e a r t r a t e ( L i g h t & O b r i s t , 1 9 8 0 ) . T h i s t y p e o f t a s k was te rmed an " a c t i v e c o p i n g " t a s k . A c t i v e c o p i n g s i t u a t i o n s a r e t h o s e w h e r e i n t h e s u b j e c t c an seek t o m o d i f y t h e e f f e c t o f t h e s t r e s s o r . T a sk s c h a r a c t e r i z e d by O b r i s t e t a l . ( 1978 ) a s r e q u i r i n g a c t i v e c o p i n g p roduce p h y s i o l o g i c a l r e s p o n s e p a t t e r n s s i m i l a r t o t h o s e p r odu ced by s e n s o r y r e j e c t i o n t a s k s . L i n d e n ( 1984 ) f o r e xamp l e , n o t e d t h a t an a c t i v e c o p i n g t a s k su ch a s m e n t a l a r i t h m e t i c r e q u i r e s g o a l - d i r e c t e d , s p e c i f i c , o v e r t b e h a v i o r s and t h a t s i g n i f i c a n t e l e v a t i o n s o f s y s t o l i c b l o o d p r e s s u r e and h e a r t r a t e c h a r a c t e r i z e t h e s t r e s s r e s p o n s e . F u r t h e r e v i d e n c e f o r t h e a s s e r t i o n o f a p o s i t i v e r e l a t i o n s h i p between a c t i v e c o p i n g and b e t a - a d r e n e r g i c i n f l u e n c e s d e r i v e s f r om two s t u d i e s , one w h i c h m a n i p u l a t e d t h e s u b j e c t ' s a b i l i t y t o cope w i t h i n t h e same t a s k ( L i g h t & O b r i s t , 1 9 8 0 ) , and a s e c o n d , w h i c h f o und t h a t d r u g s w h i c h b l o c k e d b e t a - a d r e n e r g i c e f f e c t s e l i m i n a t e d t he t y p i c a l a c t i v e c o p i n g p a t t e r n o f - 19 -response (Obrist et a l . , 1978). Active coping appears to be associated with the type of hemodynamic changes presumed to be instrumental i n the development of e s s e n t i a l hypertension (Obrist et a l . , 1978). Glass (1977) argued that an i n d i v i d u a l ' s habitual p h y s i o l o g i c a l coping s t y l e may predispose one to produce f l u c t u a t i o n s i n sympathetic arousal which are s u f f i c i e n t l y dramatic so as to influence the pathogenesis of coronary heart disease. This hypothesis i s supported by several studies. Sherwood, A l l e n , Obrist, and Langer (1984) for example, found that active coping tasks produced an increase i n heart rate greater than that required to meet metabolic demands i n a given s i t u a t i o n . Hijzen, Van der Gugter and Bouter (1984) also found increases i n c i r c u l a t i n g catecholamines during a c t i v e coping. Both increased sympathetic a c t i v i t y and increased endocrine secretions are of i n t e r e s t because a number of t h e o r e t i c a l approaches have implicated these factors i n the development of coronary pathology (Krantz & Manuck, 1984). Engagement-involvement. A t h i r d l i n e of i n v e s t i g a t i o n relevant to the issue of stimulus s p e c i f i c i t y i n cardiovascular responses to str e s s has been conducted by Williams and colleagues (Williams, Frankel, G i l l i n , & Weiss, 1973; Williams, B i t t k e r , Buchsbaum & Wynne, 1975; Williams, 1981). Williams et a l . (1973) found a d i a s t o l i c pressure increase i n response to a s t r e s s f u l interview, a sensory r e j e c t i o n s i t u a t i o n . In a subsequent study ( B i t t k e r , Buchsbaum, Williams, & Wynne, 1975) the n a t u r a l i s t i c interview was compared to a sensory intake (word i d e n t i f i c a t i o n ) , and a sensory r e j e c t i o n (mental arithmetic) task. The r e s u l t s indicated that the l e v e l of sympathetic cardiac a c t i v i t y was d i r e c t l y r e l a t e d to the associated l e v e l of "engagement-involvement" with the current environment. Decreased involvement or sensory r e j e c t i o n produced s i g n i f i c a n t elevations i n heart rate and s y s t o l i c blood - 20 -p r e s s u r e w i t h o n l y m i n i m a l changes i n d i a s t o l i c p r e s s u r e . I n t h e same v e i n , L i n d e n and F e u e r s t e i n ( 1983 ) d e m o n s t r a t e d t h a t i n h y p e r t e n s i v e p a t i e n t s i n c r e a s e d i n v o l v e m e n t o r s e n s o r y i n t a k e was a s s o c i a t e d w i t h a f l a t , n o n s i g n i f i c a n t d i a s t o l i c r e s p o n s e . M e n t a l a r i t h m e t i c a s an e x p e r i m e n t a l s t r e s s o r . The c h o i c e o f a m e n t a l a r i t h m e t i c t a s k a s an e xemp l a r y examp le o f an a c t i v e c o p i n g t a s k and r e l i a b l e e x p e r i m e n t a l s t r e s s o r i s based on a r e v i e w o f t h e l i t e r a t u r e on t h e t a s k - s p e c i f i c c a r d i o v a s c u l a r e f f e c t s a s s o c i a t e d w i t h t h i s t y p e o f s t r e s s o r . T y p i c a l l y r e s e a r c h e r s have emp loyed e i t h e r a m e n t a l a r i t h m e t i c a l o n e o r a m e n t a l a r i t h m e t i c p l u s n o i s e s t r e s s t a s k . The most common f o rm o f m e n t a l a r i t h m e t i c t a s k i n v o l v e s a s k i n g t h e s u b j e c t t o s e r i a l l y s u b t r a c t a g i v e n number, f o r e xamp l e , s even f r om t h e number one t hou sand ( S c h u l t e & Neus , 1 9 7 9 ) . A r e v i e w o f t h e l i t e r a t u r e r e v e a l e d t h i r t y - o n e s t u d i e s , t w e n t y - t h r e e u s i n g m e n t a l a r i t h m e t i c a l o n e , and e i g h t u s i n g m e n t a l a r i t h m e t i c p l u s n o i s e i n w h i c h r e s e a r c h e r s emp loyed t h e a f o r e m e n t i o n e d t y p e o f m e n t a l a r i t h m e t i c s t r e s s o r . These f i n d i n g s a r e p r e s e n t e d i n T a b l e 2 . On a v e r a g e , m e n t a l a r i t h m e t i c a l o n e p r oduced i n c r e a s e s o f 13 b e a t s pe r m i n u t e f o r h e a r t r a t e , and i n c r e a s e s o f 10 mm Hg and 5 mm Hg f o r s y s t o l i c and d i a s t o l i c b l o o d p r e s s u r e , r e s p e c t i v e l y . N i n e t e e n s t u d i e s c i t e s i g n i f i c a n t i n c r e a s e s i n h e a r t r a t e i n r e s p o n s e t o a m e n t a l a r i t h m e t i c s t r e s s o r ( B r o d , 1979; D e m b r o s k i , M c D o u g a l l & L u shene , 1979; Diamond & C a r v e r , 1980; F r a n k e n h a e u s e r & J o h a n s s o n , 1976; F r e d r i k s e n e t a l . , 1982; H e s l e g r a v e & F u r e d y , 1979; H i n t o n & C r a s k e , 1977; J o r g e n s e n & H o u s t o n , 1981 ; L ake e t a l . , 1985 ; L ane , 1984; L a w l e r , 1980; L i n d e n e t a l . , 1984; L i n d e n e t a l . , 1985; L u d b r o o k , V i n c e n t , & W a l s h , 1976; Neus e t a l . , 1981 ; S c h e r w i t z e r e t a l . , 1978; Rudde l e t a l . , 1983 ; V o s s e l & L a u x , 1977; Zwaga, 1 9 7 3 ) , w h i l e f i f t e e n s t u d i e s f ound s i g n i f i c a n t i n c r e a s e s i n b l o o d p r e s s u r e (Benthem & G l a r o s , 1980; Demb ro s k i & M a c D o u g a l l , 1979 , 1979; Diamond & C a r v e r , 1980; - 21 -TABLE 2 C a r d i o v a s c u l a r Changes A s s o c i a t e d w i t h a M e n t a l A r i t h m e t i c S t r e s s o r AUTHOR HEART RATE SYSTOLIC DIASTOLIC MAP E n g e l & B i c k f o r d , 1961 +10 Zwaga, 1973 +10 Ludb rook & W a l s h , 1976 +20% +15% W i l l i a m s e t a l . , 1976 +15% +10% +12% Manuck & S c h a e f e r , 1978 +8 +12 B r od e t a l . , 1979 +16 +19 H e s l e g r a v e & F u r e d y , 1979 +12 L a w l e r , 1980 +25 +5 +2 Manuck & G a r l a n d , 1980 +13 +17 Kushne r & F a l k n e r , 1981 +17 +6 +4 Benthem & G l a r o s , 1982 Drummond, 1983 +14 +10 +6 F o e r s t e r e t a l . , 1983 +15 L i n d e n , i n p r e s s +8 +9 +9 F r e d r i k s e n e t a l . , 1982 +12 +15 +9 Diamond & C a r v e r , 1980 +4 +8 .3 +5.2 Demb ro sk i & M a c D o u g a l l +10 +21 +11 Lake e t a l . , i n p r e s s +13 +14 +13 +14 L i n d e n e t a l . , 1985 +10 +10 +11 J o r g e n s o n & H o u s t o n , 1981 +15 +18 L a n e , 1984 +10 +11 +10 S c h e r w i t z e r e t a l . , 1978 +17 +7 +14 R u d d e l e t a l . , 1983 +17 +16 +12 Mean Change: 13 . 45 9 . 83 5 .25 +17% C a r d i o v a s c u l a r Changes A s s o c i a t e d w i t h a M e n t a l A r i t h m e t i c N o i s e S t r e s s o r V o s s e l & L a u x , 1977 +3 Neus e t a l . , 1981 +11 S c h u l t e & Neus , 1979 +11 +14 +11 S c h u l t e e t a l . , 1981 +16 +10 F r a n k e n h a e u s e r e t a l . , 1983 +9 F r a n k e n h a e u s e r & J o h a n s s o n , 1976 F r a n k e n h a e u s e r & L u n d b e r g , 1974 L i n d e n e t a l . , i n p r e s s +14 +13 +12 Mean Change: 8 . 5 1 5 . 0 1 0 . 5 n . a . N o t e : H e a r t r a t e i s e x p r e s s e d i n b e a t s pe r m i n u t e , b l o o d p r e s s u r e i n mm Hg, MAP = mean a r t e r i a l p r e s s u r e . * % change were r e p o r t e d by o r i g i n a l a u t h o r s % change s c o r e s . - 22 -F r e d r i k s e n e t a l . , 1982 ; Lake e t a l . , 1985; L a n e , 1984; L a w l e r e t a l . , 1980; L i n d e n i n p r e s s ; L i n d e n e t a l . , i n p r e s s ; L u d b r o o k , e t a l . , 1976; Neus e t a l . , 1981 ; R u d d e l e t a l . , 1983; S c h e r w i t z e r e t a l . , 1978; S c h u l t e & Neus , 1979; S c h u l t e e t a l . , 1 9 8 1 ) . S i n c e n o i s e a l o n e i s known t o p roduce a r o u s a l e f f e c t s (Oken , H e a t h , Sh i pman , G o l d s t e i n , G r i n k e r & F i s h , 1966; F r a n k e n h a e u s e r & L u n d b e r g , 1974; T e r a s a k i , 1981) s e v e r a l r e s e a r c h e r s have added n o i s e t o m e n t a l a r i t h m e t i c a s a l a b o r a t o r y s t r e s s o r . The d e c i s i o n o f p r e v i o u s a u t h o r s t o add ba ckg round n o i s e t o a t a s k a l r e a d y r e q u i r i n g e f f o r t was based on t he o b s e r v a t i o n t h a t n o i s e i n t e r f e r e n c e was a s s o c i a t e d w i t h d e c r e a s e s i n t a s k p e r f o rmance ( B r o a d b e n t , 1981 ; T e r a s a k i , 1981) and s i g n i f i c a n t i n c r e a s e s i n s u b j e c t i v e a r o u s a l ( F r a n k e n h a e u s e r & L u n d b e r g , 1 9 7 4 ) . The a r o u s a l e f f e c t s o f n o i s e have been e x t e n s i v e l y s t u d i e d ( c f . Graham, 1973; B r o a d b e n t , 1 9 8 1 ) . P h y s i o l o g i c a l changes a s s o c i a t e d w i t h e x p o s u r e t o n o i s e appea r t o be m u l t i p h a s i c and v a r y w i t h s t i m u l u s i n t e n s i t y . F o r t h e c a s e o f w h i t e n o i s e t h e r e a r e o p p o s i n g d i r e c t i o n s o f c a r d i o v a s c u l a r change a s s o c i a t e d w i t h l ow v e r s u s h i g h n o i s e l e v e l s . Wh i t e n o i s e c l e a r l y above t h r e s h o l d bu t be l ow 85 db t e n d s t o e l i c i t a b r i e f s t a r t l e r e f l e x ( l a s t i n g 2-4 s e c o n d s ) and when p r o l o n g e d i s a c compan i ed by s l i g h t c a r d i a c d e c e l e r a t i o n (Graham, 1 9 7 3 ) . L oude r n o i s e i n t h e 90 -110 db r ange i s g e n e r a l l y e x p e r i e n c e d as n o x i o u s and a v e r s i v e . I f p r e s e n t e d f o r a number o f m i n u t e s t h i s l e v e l o f n o i s e p r o d u c e s i n c r e a s e s i n h e a r t r a t e (Graham, 1 9 7 3 ) . Oken e t a l . ( 1 9 6 6 ) , f o r examp le measured b l o o d p r e s s u r e and h e a r t r a t e r e s p o n s e s t o a one m i n u t e e x p o s u r e t o a h i g h l e v e l w h i t e n o i s e . The a u t h o r s f ound s y s t o l i c b l o o d p r e s s u r e changes o f +8 mm Hg , h e a r t r a t e changes o f +6 b e a t s pe r m i n u t e , and d i a s t o l i c p r e s s u r e changes o f - 5 mm Hg . O v e r a l l , t h e s e f i n d i n g s c o n f i r m t h a t n o i s e a l o n e i f h i g h i n vo lume (>85 db) p r o v o k e s s i g n i f i c a n t c a r d i a c a r o u s a l i n -23 -healthy adults. This arousal however tends to be le s s than the cardiovascular changes observed i n t y p i c a l active oping conditions ( c f . Obrist, 1981; Linden, et a l . , i n press). Eight studies which employed mental arithmetic plus noise (90 db) as a stressor were reviewed. Mental arithmetic plus noise was found to produce average increases of 15 mm Hg, 11 mm Hg d i a s t o l i c , and 9 beats per minute i n heart rate. Five studies (Frankenhaeuser & Johansson, 1976; Linden et a l . , i n press; Schulte & Neus, 1979; Schulte et a l . , 1981; Vossel & Laux, 1977) c i t e s i g n i f i c a n t increases i n heart rate, while three (Linden et a l . , i n press; Schulte & Neus, 1979; Schulte et a l . , 1981) c i t e increases i n blood pressure. In a d d i t i o n to increases i n r e a c t i v i t y , Linden et a l . ( i n press) reported l e s s v a r i a b i l i t y of responses within high versus low heart rate reactor groups under a mental arithmetic plus 90 db white noise interference condition. In summary, a mental arithmetic plus noise stressor appears to produce r e l i a b l e and s i g n i f i c a n t increases i n heart rate and blood pressure. The pattern of heart rate and s y s t o l i c pressure responses e l i c i t e d i s consistent with that described by Obrist (Obrist et a l . , 1978) as an a c t i v e coping response. The d i a s t o l i c blood pressure response to mental arithmetic plus noise requires further examination. As previously noted, d i a s t o l i c responses to mental arithmetic plus white noise are often s i m i l a r i n magnitude to the aforementioned s y s t o l i c blood pressure increases. This f i n d i n g i s inconsistent with Obrist's formulation of an a c t i v e coping task. Obrist would predict very l i t t l e change i n d i a s t o l i c pressure. This discrepancy i n r e s u l t s may be due i n part to differences i n the c h a r a c t e r i s t i c s of the tasks involved i n Obrist's t y p i c a l active coping paradigm versus the t y p i c a l mental arithmetic plus noise condition. Obrist t y p i c a l l y employs a shock avoidance task as an active coping task. C l e a r l y the aforementioned d i f f e r e n c e s i n - 24 _ d i a s t o l i c r e s p o n s e p a t t e r n may a r i s e f r om d i f f e r e n c e s i n t h e i n d i v i d u a l ' s s u b j e c t i v e e x p e r i e n c e o f t h e demands imposed by m e n t a l a r i t h m e t i c v e r s u s a shock a v o i d a n c e t a s k . Summary: S t i m u l u s s p e c i f i c i t y v e r s u s r e s p o n s e s t e r e o t y p y . I n summary, i t c an be s een t h a t t h e c a r d i o v a s c u l a r s y s t em i s c h a r a c t e r i z e d by b o t h i n d i v i d u a l r e s p o n s e s t e r e o t y p y and a s e n s i t i v i t y t o s t i m u l u s - s p e c i f i c v a r i a b l e s . The deg ree o f i n f l u e n c e o f t h e s e d i m e n s i o n s v a r i e s b o t h a c r o s s g r o u p s , i . e . , h i g h v e r s u s l ow h e a r t r a t e r e a c t o r s ; and w i t h i n i n d i v i d u a l s a c r o s s s i t u a t i o n s . These a p p a r e n t l y c o n f l i c t i n g p o s i t i o n s , t e m p o r a l s t a b i l i t y v e r s u s s i t u a t i o n a l r e a c t i v i t y r em ind one t h a t i n d i s s e c t i n g an i n d i v i d u a l ' s r e s p o n s e t o a g i v e n s t r e s s o r one i s c o n s t a n t l y c o n f r o n t e d by t h e need t o s i m u l t a n e o u s l y c o n s i d e r b o t h f a c t o r s . F o e r s t e r e t a l . ( 1983 ) s u g g e s t t h a t t h e i n d i v i d u a l - s p e c i f i c r e s p o n s e and t h e s t i m u l u s - s p e c i f i c r e s p o n s e i n t e r a c t t o p r oduce what may be c a l l e d t h e " i n d i v i d u a l - s i t u a t i o n - s p e c i f i c " r e s p o n s e whereby i n d i v i d u a l r e s p o n s e s a r e i n f l u e n c e d by a s t i m u l u s t o t h e deg ree t h a t t h e r e s u l t i n g p a t t e r n o f r e s p o n s e c on f o rms t o t h a t o f t y p i c a l r e s p o n s e s seen under a g i v e n s t i m u l u s s i t u a t i o n . I t s h o u l d a l s o be n o t e d t h a t t h e d e l i n e a t i o n o f s p e c i f i c s u b j e c t o r s t i m u l u s p r o p e r t i e s i n a g i v e n s t r e s s o r s i t u a t i o n i s a v e r y d i f f i c u l t and comp lex u n d e r t a k i n g . The i n d i v i d u a l and h i s o r h e r e n v i r o n m e n t a r e i n v o l v e d i n a t r a n s a c t i o n i n w h i c h each r e c i p r o c a l l y i n f l u e n c e s t h e o t h e r on an o n g o i n g b a s i s ( P e r v i n , 1 9 6 8 ) . An a c c e p t a n c e o f t h e i n t e r a c t i v e n a t u r e o f t h e a f o r e m e n t i o n e d f a c t o r s i s c r u c i a l t o an u n d e r s t a n d i n g o f t h e r e l a t i v e i n f l u e n c e o f t h e v a r i a b l e s i n v o l v e d i n an i n d i v i d u a l ' s r e s p o n s e t o s t r e s s . K o r n e r and S imon ( 1975 ) s u g g e s t e d t h a t t h e c e n t r a l n e r v o u s s y s t e m i s s e t up t o i n t e g r a t e " n o t o n l y a u t onom i c bu t a l s o s o m a t i c and b e h a v i o r a l r e s p o n s e s by w h i c h t h e o r g a n i s m meets b o t h p h y s i o l o g i c a l and p s y c h o l o g i c a l demands" . - 2 5 -They a rgue t h a t t h e b r a i n i s o r g a n i z e d t o p r odu ce somatomotor and c a r d i o v a s c u l a r " b e h a v i o r s " a s components o f a s i n g l e i n t e g r a t e d p a t t e r n , d e p e n d i n g upon t he a d j u s t m e n t s r e q u i r e d by e n v i r o n m e n t a l e v e n t s . A number o f s u c h i n t e g r a t e d p a t t e r n s o f r e s p o n s e have now been i d e n t i f i e d as b e i n g a s s o c i a t e d w i t h o r g a n i s m - e n v i r o n m e n t i n t e r a c t i o n s i n v o l v i n g e x e r c i s e , f i g h t o r f l i g h t , f e e d i n g , o r d i v i n g b e h a v i o r s ( s e e Aboud , H e i s t a d , Ma rk , & S c h m i d , 1976 f o r a r e v i e w o f t h e s e p a t t e r n s ) . Among t h e i n t e g r a t e d p a t t e r n s o f r e s p o n s e ( H i l t o n , 1975) t h a t have been s t u d i e d , t h e b e s t known and most e x t e n s i v e l y s t u d i e d i s t h e a f o r e m e n t i o n e d d e f e n s e r e a c t i o n . The d e f e n s e r e a c t i o n i s c h a r a c t e r i z e d by i n t e n s e a f f e c t , h e i g h t e n e d somatomotor a c t i v i t y , i n c r e a s e d c a r d i a c o u p u t , and a s h u n t i n g o f b l o o d f r om t h e s k i n and v i s c e r a t o t h e s k e l e t a l mus c l e v a s c u l a t u r e . A l l o f t h e s e c o o r d i n a t e d r e s p o n s e s have been shown t o be m e d i a t e d by a common b r a i n s y s t em (Abrahams , H i l t o n , & Z b r o z y n a , 1 9 6 0 ) . S e v e r a l i n v e s t i g a t o r s (Aboud , 1976; F o l k ow & N e i l , 1971 ; H e n r y , E l y , & S t e p h e n s , 1972) have p r o po s ed t h a t t h e e f f e c t s o f t h e r e p e a t e d a c t i v a t i o n s o f t h e d e f e n s e r e a c t i o n upon b a r o r e c e p t o r and v a s c u l a r f u n c t i o n may be i m p o r t a n t i n t h e p a t h o g e n e s i s o f c o r o n a r y d i s e a s e . As H a l l b a c k ( 1976 ) n o t e d , " i t seems l i k e l y t h a t t h e d e f e n s e r e a c t i o n i s o n l y one o f s e v e r a l e m o t i o n a l l y i n d u c e d b e h a v i o r a l r e s p o n s e p a t t e r n s w h e r e i n neu r oho rmona l a d j u s t m e n t s may p roduce s e r i o u s d i s t u r b a n c e s c o n c e r n i n g b o t h o r gan f u n c t i o n and m e n t a l s t a t e " . I t i s p e r hap s n o t t o o s u r p r i s i n g , t h e r e f o r e , t h a t r e c e n t i n v e s t i g a t i o n s have s u g g e s t e d t h a t t h e p a t t e r n o f c a r d i o v a s c u l a r r e s p o n s e s seen i n r e a c t i o n t o a p s y c h o l o g i c a l s t r e s s o r s u c h as m e n t a l a r i t h m e t i c may r e p r e s e n t a q u a l i t a t i v e l y d i f f e r e n t , y e t e q u a l l y p a t h o g e n i c s e t o f c a r d i o v a s c u l a r r e s p o n s e s ( G l a s s , 1977; H i j z e n e t a l . , 1984; L i n d e n e t a l . , i n p r e s s ) . Task X p e r s o n i n t e r a c t i o n s . The f o r m a l a p p r o a c h e s f o r c l a s s i f y i n g - 26 -s t r e s s o r t a s k s p r e v i o u s l y d e s c r i b e d , i . e . , s e n s o r y r e j e c t i o n v e r s u s s e n s o r y i n t a k e and p a s s i v e v e r s u s a c t i v e c o p i n g c o m p r i s e o n l y two p o s s i b l e s t i m u l u s d i m e n s i o n s o f p r o b a b l e i m p o r t a n c e i n t h e d e t e r m i n a t i o n o f p h y s i o l o g i c r e s p o n s e s t o a g i v e n s t r e s s o r . Numerous a u t h o r s h a v e , f o r e x amp l e , i m p l i c a t e d g e n e t i c , p s y c h o s o c i a l , p h y s i o l o g i c a l , and e n v i r o n m e n t a l f a c t o r s i n t h e i r a t t e m p t s t o a n a l y z e t h e s t r e s s r e s p o n s e f r om a t r a n s a c t i o n a l o r d i a t h e s i s - s t r e s s v i e w p o i n t ( G r i n k e r , 1953; L e v i , 1 9 7 4 ) . I t has a l s o been s u g g e s t e d t h a t t h e e m o t i o n a l q u a l i t y o f t h e t a s k i n v o l v e d i n f l u e n c e s t h e n a t u r e o f t h e s ub s equen t s t r e s s r e s p o n s e . T h i s h y p o t h e s i s i s s u p p o r t e d by r e s e a r c h w h i c h d i f f e r e n t i a t e d f e a r and a n g e r , r e s p e c t i v e l y , i n t e rms o f " e p i n e p h r i n e - l i k e " v e r s u s " n o r e p i n e p h r i n e - l i k e r e s p o n s e s " ( A x , 1953 ; S c h a c t e r , 1 9 5 7 ) . The r e a r e howeve r , i n c o n s i s t e n c i e s i n t h e l i t e r a t u r e on t h e p h y s i o l o g i c a l c o r r e l a t e s o f emo t i o n ( G l a s s & C o n t r a d a , 1 9 8 4 ) . K r a n t z and Manuck (1984 ) c o n c l u d e d t h a t w h i l e d i f f e r e n t emo t i o n s appea r t o be a c compan i ed by d i f f e r e n t p a t t e r n s o f p h y s i o l o g i c r e s p o n d i n g (Ekman, L e v e n s o n , & F r i e s e n , 1 9 8 3 ) , t h e p r e c i s e p h y s i o l o g i c a l p a t t e r n a s s o c i a t e d w i t h ea ch s u b j e c t i v e e x p e r i e n c e o r emo t i on r e m a i n s t o be d e t e r m i n e d . A l a r g e body o f p s y c h o e n d o c r i n e and p s y c h o l o g i c a l r e s e a r c h on s t r e s s ( F r a n k e n h a e u s e r , 1983; G l a s s & S i n g e r , 1972; L a z a r u s , 1966; L a z a r u s , 1974; L a z a r u s & F o l k m a n , 1984; Mason , 1975) s u p p o r t s t h e h y p o t h e s i s t h a t t h e e f f e c t i v e n e s s o f p s y c h o s o c i a l f a c t o r s i n p r o d u c i n g p o t e n t i a l l y p a t h o g e n i c s y m p a t h e t i c a r o u s a l depends on t h e i n d i v i d u a l ' s c o g n i t i v e a p p r a i s a l o f t h e s i t u a t i o n . L a z a r u s ( 1966 ) p r o po s ed t h a t p s y c h o l o g i c a l s t r e s s r e q u i r e s a judgement t h a t t h e demands i n h e r e n t i n a g i v e n s i t u a t i o n t a x o r e x ceed t h e i n d i v i d u a l ' s s e l f - p e r c e i v e d a b i l i t y t o d e a l w i t h t hem. L a z a r u s ( 1966 ; L a z a r u s & F o l k m a n , 1984) p o s t u l a t e d t h a t two i n t e r a c t i n g p r o c e s s e s t e rmed a p p r a i s a l and c o p i n g a r e i n v o l v e d . A p p r a i s a l i n v o l v e s a judgement t h a t an e v e n t i s - 27 -e i t h e r i r r e l e v a n t o r s t r e s s f u l i n i t s p o s s i b l e c on sequence s ( G o l d b e r g e r & B r e z n i t z , 1 9 8 2 ) . B o t h p o s i t i v e and n e g a t i v e e v e n t s may be a p p r a i s e d as s t r e s s f u l . Depue, Monroe , and Shackman (1979) o f f e r e d a c ogen t a n a l y s i s o f t h e way a p p r a i s a l p r o c e s s e s may m e d i a t e t h e i m p a c t o f p s y c h o s o c i a l f a c t o r s on t h e p a t h o g e n e s i s o f c a r d i o v a s c u l a r d i s o r d e r s : " A t a s p e c i f i c l e v e l , c e r t a i n p s y c h o l o g i c a l c h a r a c t e r i s t i c s may o p e r a t e d i r e c t l y on t h e a p p r a i s a l p r o c e s s and may p r e d i s p o s e t h e i n d i v i d u a l t o p e r c e i v e a p a r t i c u l a r c l a s s o f e v e n t s as t h r e a t e n i n g . A t a more g e n e r a l l e v e l , p s y c h o l o g i c a l c h a r a c t e r i s t i c s may l e a d t o t h e deve l opment o f schema p r e d i s p o s i n g t h e i n d i v i d u a l t o p e r c e i v e a w i d e r r ange o f e v e n t s a s t h r e a t e n i n g . By i n c r e a s i n g t h e p o t e n t i a l impa c t o f p s y c h o s o c i a l s t i m u l i , p s y c h o l o g i c a l p r e d i s p o s i n g v a r i a b l e s may p l a y a key r o l e i n e x a c e r b a t i n g t h e e m o t i o n a l - b i o l o g i c a l m e d i a t o r s t h a t s e r v e t o a c t i v a t e b i o l o g i c a l p r e d i s p o s i n g b i a s e s l e a d i n g t o d i s e a s e " . A p p r a i s a l s w h i c h r e s u l t i n h o s t i l i t y and anger f o r e xamp l e , have been l i n k e d t o a c u t e m a l a d a p t i v e b l o o d p r e s s u r e and h e a r t r a t e r e s p o n s e s ( S t e p t o e , M e l v i l l e , & R o s s , 1 9 8 4 ) , and have been f ound t o p r e d i c t t h e deve l opmen t o f h e a r t d i s e a s e ( S h e k e l l e , G a l e , O s t f e l d , & O g l e s b y , 1 9 8 3 ) . As p r e v i o u s l y n o t e d , p h y s i o l o g i c a l r e s p o n s e s t o s t r e s s a r e c r i t i c a l l y dependent on t he manner i n w h i c h s u b j e c t s i n t e r p r e t t h e s t i m u l i p r e s e n t e d t o them. I n t u r n each i n d i v i d u a l makes a judgement o f h i s o r he r a b i l i t y t o cope w i t h a g i v e n s t r e s s o r based upon h i s o r h e r a p p r a i s a l o f t h e s i t u a t i o n . Judgements o f p e r c e i v e d i n a b i l i t y t o cope w i t h p s y c h o l o g i c a l s t r e s s have been l i n k e d t o t h e s ub sequen t deve l opmen t o f v a r i o u s p s y c h o s o m a t i c d i s o r d e r s ( E n g e l , 1968; M u l l e n & S u l s , 1981 ; G l a s s , 1976; L l o y d , A l e x a n d e r , R i c e , & G r e e n f i e l d , 1 9 8 0 ) . Bandu ra (1982 ) a l s o f ound t h a t s u b j e c t s who were l ow on p e r c e i v e d s e l f - e f f i c a c y d i s p l a y e d g r e a t p h y s i o l o g i c a l a r o u s a l i n r e s p o n s e t o p s y c h o l o g i c a l s t r e s s . Re cen t e v i d e n c e d e r i v e d f r om s t u d i e s o f c a r d i a c p a t i e n t s under g e n e r a l a n e s t h e s i a ( K a h n , K o r n f i e l d , F r a n k , H e l l e r , & H o a r , 1980; K r a n t z , A r a b i a n , D a v i a , & P a r k e r , 1982) f u r t h e r s u g g e s t s t h a t c o n s c i o u s - 2 8 -m e d i a t i o n may no t be a n e c e s s a r y c o n d i t i o n f o r t h e e l i c i t a t i o n o f p o t e n t i a l l y p a t h o g e n i c s y s t o l i c b l o o d p r e s s u r e r e s p o n s e s . P h y s i o l o g i c a l r e a c t i v i t y a p p e a r s t o be most p ronounced t o p s y c h o l o g i c a l c h a l l e n g e s i n v o l v i n g a h i g h deg ree o f t a s k i n v o l v e m e n t r a t h e r t h a n p h y s i c a l t a s k s s u c h as t h e c o l d p r e s s o r t e s t ( K r a n t z , G l a s s , S c h a e f f e r , & D a v i a , 1982; Manuck e t a l . , i n p r e s s ) . I n t h e c a s e o f c o g n i t i v e t a s k s s u ch a s m e n t a l a r i t h m e t i c t h e s u b j e c t ' s p e r c e p t i o n o f t h e s t r e s s f u l n e s s , d i f f i c u l t y , and i m p o r t a n c e o f t h e t a s k may v a r y as a f u n c t i o n o f t h e s t r e s s o r ' s c h a r a c t e r i s t i c s . F o r e x amp l e , n o i s e has been shown t o i n c r e a s e p e r c e i v e d t a s k d i f f i c u l t y ( L o v a l l o & P i s h k i n , 1 9 8 0 ) . P e r c e p t i o n s o f t a s k d i f f i c u l t y , s t r e s s f u l n e s s , p e r f o r m a n c e , and i m p o r t a n c e may a l s o v a r y a s a f u n c t i o n o f t h e s u b j e c t ' s g e n d e r , e d u c a t i o n , and s o c i o e c o n o m i c s t a t u s ( K r a n t z & Manuck, 1 9 8 4 ) . C o p i n g c o g n i t i o n s have a l s o been f ound t o e f f e c t an i n d i v i d u a l ' s s t r e s s t a s k b e h a v i o r ( K r a n t z , 1 9 8 3 ) . F ow l e s (1983 ) f o r e xamp l e , f ound t h a t h e a r t r a t e v a r i e d as a f u n c t i o n o f t h e s u b j e c t s ' s e l f - r e p o r t e d l e v e l o f m o t i v a t i o n . E s t i m a t e s o f i n c r e a s e d t a s k d u r a t i o n have a l s o been l i n k e d t o h i g h h e a r t r a t e r e a c t i v i t y (Manuck, C o r s e , & W inke lman , 1 9 7 9 ) . The e x i s t e n c e o f t h e a f o r e m e n t i o n e d e v i d e n c e r e g a r d i n g t he s i g n i f i c a n t i m p a c t o f t h e p s y c h o l o g i c a l p r o c e s s e s o f a p p r a i s a l and c o p i n g on t h e n a t u r e o f t h e s t r e s s r e s p o n s e s h o u l d a l e r t r e s e a r c h e r s t o t h e danger o f a d o p t i n g a r e d u c t i o n i s t i c a p p r o a c h t o t h e measurement o f c a r d i o v a s c u l a r r e a c t i v i t y t o p s y c h o l o g i c a l s t r e s s . R e s e a r c h e r s must c o n t i n u e t o i n c l u d e m u l t i - d i m e n s i o n a l c o g n i t i v e and p h y s i o l o g i c a l measu res i n t h e i r e f f o r t s t o a n a l y z e P e r s o n X Task i n t e r a c t i o n s . S t a b i l i t y o f i n d i v i d u a l d i f f e r e n c e s i n c a r d i o v a s c u l a r r e a c t i v i t y . A l a r g e body o f e v i d e n c e e x i s t s w h i c h s u p p o r t s t h e n o t i o n o f i n d i v i d u a l r e s p o n s e s t e r e o t y p y ( F o e r s t e r e t a l . , 1983) i n c a r d i o v a s c u l a r r e s p o n s e s t o c o g n i t i v e - 29 -s t r e s s o r s . I n s e e k i n g t o f u r t h e r a n a l y z e t h e i m p a c t o f i n d i v i d u a l - s p e c i f i c f a c t o r s on t h e s t r e s s r e s p o n s e numerous a u t h o r s ( L a c e y & L a c e y , 1962 ; P a t t o n , 1969; Manuck & S c h a e f f e r , 1978; Manuck & G a r l a n d , 1980; S c h u l t e e t a l . , 1 981 ; C a r r o l l e t a l . , 1984) have i n v e s t i g a t e d t h e s t a b i l i t y o f p h y s i o l o g i c a l r e s p o n s e s t o a g i v e n s t r e s s o r o v e r t i m e . I n an e a r l y p a p e r , L a c ey and L a cey (1962 ) n o t e d t h a t s u b j e c t s d i s p l a y e d an i d i o s y n c r a t i c a l l y d e t e r m i n e d , max ima l l e v e l o f r e s p o n s e t o a s t r e s s o r a d m i n i s t e r e d o v e r a f o u r - y e a r p e r i o d . T h i s max ima l l e v e l was i n d e p e n d e n t o f w i d e l y v a r y i n g i n i t i a l w i t h i n - s u b j e c t r e s p o n s e l e v e l s . M i n e r , M cK i nney , R u d d e l , B u e l l , E l i o t , and G r a n t ( 1984 ) a l s o f ound good t e s t - r e t e s t r e l i a b i l i t y f o r a m e n t a l a r i t h m e t i c s t r e s s o r i n t e rms o f i n d i v i d u a l - s p e c i f i c r e a c t i v i t y . P a t t o n (1969 ) c o n c u r r e d i n f i n d i n g t h a t s u b j e c t s r e s ponded c o n s i s t e n t l y t o a v a r i e t y o f s t r e s s o r s i n c l u d i n g anag rams , c o l d p r e s s o r t e s t , e x p o s u r e t o h e a t , and e x p o s u r e t o a f i l m o f s u r g e r y . S u b j e c t s d i s p l a y e d i n d i v i d u a l - s p e c i f i c r e s p o n s e s i n t e rms o f b o t h magn i t ude o f r e s p o n s e change and a b s o l u t e l e v e l o f c a r d i o v a s c u l a r a c t i v i t y on h e a r t r a t e and s y s t o l i c b l o o d p r e s s u r e m e a s u r e s . I n a s e r i e s o f s t u d i e s Manuck and h i s c o l l e a g u e s have examined t h e r e p r o d u c i b i l i t y o f i n d i v i d u a l d i f f e r e n c e s i n b l o o d p r e s s u r e and h e a r t r a t e r e a c t i o n s t o a d i f f i c u l t c o n c e p t f o r m a t i o n t a s k a c r o s s v a r y i n g i n t e r - s t r e s s o r i n t e r v a l s . S u b j e c t s were c l a s s i f i e d as h i g h o r l ow r e a c t o r s on t h e b a s i s o f t h e magn i t ude o f t h e i r i n i t i a l r e s p o n s e s t o t h e s t r e s s t a s k . H i g h and l ow h e a r t r a t e r e a c t o r s were f ound t o d i f f e r a t each o f two f o l l o w - u p e v a l u a t i o n s a f t e r 1 week and 13 month i n t e r v a l s , r e s p e c t i v e l y (Manuck & S c h a e f f e r , 1978; Manuck & G a r l a n d , 1 9 8 0 ) . S i m i l a r r e s u l t s were f ound f o r measures o f s y s t o l i c r e a c t i v i t y . H i g h and low d i a s t o l i c r e a c t o r s were d i s t i n g u i s h a b l e a f t e r one week, bu t n o t a f t e r t h i r t e e n mon ths . G i o r d a n i , Manuck and Farmer ( 1981 ) i n a s ub s equen t s t u d y o f h e a r t r a t e r e s p o n s i v i t y i n c h i l d r e n a l s o f ound - 30 -r e p r o d u c i b l e i n d i v i d u a l d i f f e r e n c e s o v e r a one week i n t e r v a l . P e a r s o n c o r r e l a t i o n s between change s c o r e s c a l c u l a t e d f o r ea ch o f t h e two v i s i t s r a nged f r om .60 t o .80 f o r b o t h s y s t o l i c b l o o d p r e s s u r e and h e a r t r a t e . S i m i l a r i n t e r - t a s k c o r r e l a t i o n s have been r e p o r t e d e l s e w h e r e ( O b r i s t , 1981 ; L a n e , 1 9 8 4 ) . As n o t e d by Lane ( 1 9 8 4 ) , t h e magn i t ude o f t h e a f o r e m e n t i o n e d c o r r e l a t i o n s means however t h a t a p p r o x i m a t e l y h a l f o f t h e v a r i a n c e i n t h e second r e s p o n s e i s n o t a c c o u n t e d f o r by t h e f i r s t r e s p o n s e . I n a r e p e a t e d measures d e s i g n t h i s u n a c c o u n t e d - f o r v a r i a n c e c o n t r i b u t e s t o t h e o v e r a l l e r r o r v a r i a n c e . The r e s u l t o f t h i s l ow r e l i a b i l i t y may be a r e d u c t i o n i n t h e power o f a g i v e n e x p e r i m e n t t o d e t e c t a t r e a t m e n t e f f e c t . I n summary, a modera te deg ree o f s t a b i l i t y o f i n d i v i d u a l - s p e c i f i c r e a c t i v i t y t o a g i v e n s t r e s s o r o v e r s i g n i f i c a n t t ime i n t e r v a l s has been r e p o r t e d by s e v e r a l r e s e a r c h e r s . I t s h o u l d be n o t e d howeve r , t h a t i n d i v i d u a l d i f f e r e n c e s i n s t r e s s r e s p o n s e o v e r r e p e a t e d e x p o s u r e s a r e n o t e n t i r e l y c o n s t a n t . I n a r e v i e w o f r e s e a r c h i n v o l v i n g r e l a t i v e l y s h o r t t e s t - r e t e s t p e r i o d s o f 1 t o 4 weeks a t t e n u a t i o n o f r e a c t i v i t y t o t h e second s t r e s s o r e xpo su r e was r e p o r t e d ( H i l l & K r a n t z , 1983; Manuck e t a l . , 1 981 ; Manuck & S c h a e f f e r , 1 9 7 8 ) . W i t h l o n g e r t e s t - r e t e s t i n t e r v a l s o f 1 y e a r , a t t e n u a t i o n o f r e a c t i v i t y was no t o b s e r v e d (Manuck & G a r l a n d , 1 9 8 0 ) . H a b i t u a t i o n o f C a r d i o v a s c u l a r Responses I n a d d i t i o n t o a s s e s s i n g t h e r e l a t i v e s t a b i l i t y o f r e s p o n s e s , one must a l s o c o n s i d e r t h e d i m e n s i o n o f r e s p o n s e h a b i t u a t i o n when c o n s i d e r i n g c a r d i o v a s c u l a r changes o v e r t i m e . The t e r m , h a b i t u a t i o n , i s u sed t o r e f e r t o a d e c r e a s e i n magn i t ude o f a r e s p o n s e w i t h r e p e a t e d o r e x t ended p r e s e n t a t i o n o f an e l i c i t i n g s t i m u l u s when t h a t d e c r e a s e c anno t be a c c o u n t e d f o r i n t e rms o f f a t i g u e o r r e c e p t o r a d a p t a t i o n (Thompson & S p e n c e r , 1966; Graham, 1 9 7 3 ) . - 31 -I n man, h a b i t u a t i o n i s t y p i c a l l y s t u d i e d i n t e rms o f c o r t i c a l o r a u t onom i c r e s p o n s e s t o s i m p l e s e n s o r y s t i m u l a t i o n r e c o r d e d v i a n o n - i n v a s i v e t e c h n i q u e s . H a b i t u a t i o n has been l e s s commonly measured i n t e rms o f motor r e s p o n s e s ( S c h o l a n d e r , 1 9 6 1 ) , and s e l f - r e p o r t measures ( G l a s e r , 1 9 6 6 ) . As p r e v i o u s l y n o t e d , a d j u s t m e n t t o s t r e s s by an i n d i v i d u a l r e q u i r e s a c o g n i t i v e a p p r a i s a l o f t h e s i g n i f i c a n c e o f a g i v e n e v e n t ( L a z a r u s , 1 9 6 6 ) . I a c ono and L y k k e n ( 1983 ) have s u g g e s t e d t h a t h a b i t u a t i o n i n v o l v e s s u c h an a p p r a i s a l . H a b i t u a t i o n i s s een as i n v o l v i n g t h e a b i l i t y t o t une ou t o r s t o p r e a c t i n g t o a s t i m u l u s t h a t has no s i g n a l v a l u e o r has l o s t i t s s i g n i f i c a n c e . The i d e n t i f i c a t i o n o f s p e c i f i c p a t t e r n s o f c a r d i o v a s c u l a r h a b i t u a t i o n may have p r o f o u n d i m p l i c a t i o n s f o r t h e i d e n t i f i c a t i o n o f p o s s i b l e pa thways i n v o l v e d i n t h e t r a n s d u c t i o n o f a c u t e s t r e s s r e s p o n s e s , i . e . , h y p e r r e a c t i v i t y , i n t o c h r o n i c c o r o n a r y p a t h o l o g y . O b r i s t e t a l . ( 1978 ) have s u g g e s t e d f o r e x amp l e , t h a t a m a l a d a p t i v e r e s p o n s e may be one i n w h i c h i n c r e a s e d o r m a i n t a i n e d a r o u s a l i s n o t a s s o c i a t e d w i t h a m e t a b o l i c n e e d . M a l a d a p t i v e r e s p o n s e s may c o n t i n u e t o o c c u r d e s p i t e t h e c e s s a t i o n o r ab sence o f an e l i c i t i n g s t i m u l u s . C h a r a c t e r i s t i c s o f c a r d i o v a s c u l a r h a b i t u a t i o n . E a r l y work on • c a r d i o v a s c u l a r p a t t e r n s o f h a b i t u a t i o n t o p s y c h o l o g i c a l s t r e s s f o c u s e d on h e a r t r a t e i n c r e a s e s as a dependent measure o f h a b i t u a t i o n ( E n g e l , 1 9 6 0 ) . S e v e r a l o t h e r r e s e a r c h e r s ( J o ne s & J o h n s o n , 1975; Manuck & S c h a e f f e r , 1978; Manuck & G a r l a n d , 1980; S c h u l t e e t a l . , 1 981 ; L a n e , 1984; Zwaga, 1973) have r e p o r t e d h a b i t u a t i o n o f h e a r t r a t e r e s p o n s e s f o l l o w i n g r e p e a t e d e x p o s u r e t o a c o g n i t i v e s t r e s s o r s u c h as m e n t a l a r i t h m e t i c . L a c ey and o t h e r s ( L a c e y , 1963; L a cey e t a l . , 1967) have a r gued t h a t h e a r t r a t e r e s p o n s e s a r e m u l t i - p h a s i c i n n a t u r e . The h e a r t r a t e r e s p o n s e i n v o l v e s b o t h a c c e l e r a t i v e and d e c e l e r a t i v e componen t s . I n g e n e r a l , d e c e l e r a t i v e components have been f ound t o h a b i t u a t e r a p i d l y w h i l e a c c e l e r a t i v e components show f a r g r e a t e r v a r i a b i l i t y d epend i ng - 32 -on t h e s t i m u l u s c o n d i t i o n s ( Lang & H n a t i o w , 1 9 6 2 ) . A l t h o u g h t h e r e i s some r e c e n t e v i d e n c e o f s y s t o l i c b l o o d p r e s s u r e h a b i t u a t i o n a c r o s s r e l a t i v e l y s h o r t i n t e r - s t r e s s o r i n t e r v a l s ( L a n e , 1984) t h e q u e s t i o n o f s t i m u l u s r e p e t i t i o n e f f e c t s on b l o o d p r e s s u r e has n o t been t h o r o u g h l y e x p l o r e d . I n r e v i e w i n g t h e r e s e a r c h l i t e r a t u r e , B o h l i n ( 1973 ) r e a c h e d a number o f g e n e r a l c o n c l u s i o n s r e g a r d i n g t h e c h a r a c t e r i s t i c s o f c a r d i o v a s c u l a r h a b i t u a t i o n . F i r s t , t h e r e i s a s t r o n g d i m e n s i o n o f i n d i v i d u a l d i f f e r e n c e s f o r b o t h l e v e l o f a r o u s a l and r a t e o f h a b i t u a t i o n . These d i f f e r e n c e s a r e m e d i a t e d on b o t h a p h y s i o l o g i c a l ( O b r i s t , L a w l e r , Howard , S m i t h s o n , M a r t i n , & M a n n i n g , 1974; F r a n k e n h a e u s e r , F r o b e r g , H a g d a h l , R i s s l e r , B o r k v a l l , & W o l f f , 1967) and a p s y c h o l o g i c a l l e v e l ( L a z a r u s , 1 9 6 6 ) . S e c o n d , t h e p r o c e s s o f h a b i t u a t i o n p r o d u c e s a c o n c u r r e n t d e c r e a s e i n a r o u s a l . S c h o l a n d e r ( 1960 ) h e l d t h a t an i n v e r s e r e l a t i o n s h i p e x i s t s between a r o u s a l l e v e l and r a t e o f h a b i t u a t i o n . B o h l i n and T i z a r d ( 1966 ) howeve r , f ound no s u c h r e l a t i o n s h i p . B o h l i n ( 1973 ) s u g g e s t s t h a t t h e d i s c r e p a n c y i n r e s u l t s i s due t o t h e use o f d i f f e r e n t c r i t e r i a i n t h e measurement o f r e s p o n s e h a b i t u a t i o n . T h i r d , B o h l i n ( 1973 ) c o n c l u d e d t h a t i n c r e a s e d a r o u s a l b r i n g s abou t a d e l a y i n h a b i t u a t i o n w h i c h i s i n d e p e n d e n t o f t h e c h a r a c t e r i s t i c s o f t h e s t r e s s o r i n v o l v e d . T h i s f i n d i n g i s a l s o s u p p o r t e d by Mat thews and L a d e r ( 1 9 6 5 ) . M e t h o d o l o g i c a l I s s u e s R e g a r d i n g R e a c t i v i t y and H a b i t u a t i o n I n o r d e r t o s t u d y t h e r e l a t i o n s h i p between c a r d i o v a s c u l a r r e a c t i v i t y and r e s p o n s e h a b i t u a t i o n i t i s n e c e s s a r y t o o b t a i n v a l i d and r e l i a b l e measurements a c r o s s t i m e . I n t h i s r e g a r d , s e v e r a l m e t h o d o l o g i c a l and m e a s u r e m e n t - r e l a t e d i s s u e s a r e o f c o n c e r n . These i s s u e s w h i c h i n c l u d e s u b j e c t c h a r a c t e r i s t i c s , s i t u a t i o n a l i n f l u e n c e s , p r e - s t r e s s a d a p t a t i o n and b a s e l i n e , i n s t r u c t i o n e f f e c t s , t a s k c h a r a c t e r i s t i c s , s t i m u l u s r e p e t i t i o n , i n t e r - s t r e s s o r i n t e r v a l , and t h e d e f i n i t i o n and s e l e c t i o n o f a p p r o p r i a t e r e s p o n s e measu res a r e 33 d i s c u s s e d i n t h e f o l l o w i n g s e c t i o n s . S u b j e c t c h a r a c t e r i s t i c s . A number o f m e t h o d o l o g i c a l p r ob l ems a r i s e i n a t t e m p t s t o i n v e s t i g a t e t h e r e l a t i o n s h i p between s u b j e c t c h a r a c t e r i s t i c s and i n d i v i d u a l d i f f e r e n c e s i n r e a c t i v i t y and r e s p o n s e h a b i t u a t i o n . P r o b l ems s p e c i f i c t o t h e e f f e c t s o f p e r s o n a l i t y on h a b i t u a t i o n have been r e v i e w e d e l s e w h e r e ( A v e r i l l & Op t on , 1968; F i s k e , 1971 ; J ohn son & L u b i n , 1972; C h r i s t i e & Todd , 1 9 7 5 ) . I n a more r e c e n t r e v i e w O'Gorman (1977) f ound t h a t t h e d i m e n s i o n s o f a n x i e t y and e x t r a v e r s i o n were most f r e q u e n t l y f ound t o be i m p l i c a t e d i n p r e d i c t i o n s abou t i n d i v i d u a l d i f f e r e n c e s i n r e s p o n s e h a b i t u a t i o n . A n x i e t y as d e f i n e d by t h e M a n i f e s t A n x i e t y S c a l e ( T a y l o r , 1983) was p o s i t i v e l y c o r r e l a t e d w i t h c a r d i a c o u t p u t . A d i f f i c u l t y f o r h y p o t h e s e s r e g a r d i n g i n d i v i d u a l d i f f e r e n c e s i n h a b i t u a t i o n based on measures o f a r o u s a l i s t h e p r e v i o u s l y c i t e d e v i d e n c e on t he d i s s o c i a t i o n o f r e s p o n s e s y s t e m s . As L a c e y ' s ( 1967 ) r e s e a r c h has made c l e a r , a r o u s a l i s n o t a u n i t a r y phenomenon. Most h y p o t h e s e s abou t p e r s o n a l i t y and r e s p o n s e h a b i t u a t i o n have a v o i d e d t h i s i s s u e by r e s t r i c t i n g t h e i r p r e d i c t i o n s t o one r e s p o n s e s y s t e m , t h e e l e c t r o d e r m a l (O 'Go rman , 1 9 7 7 ) . S t u d i e s o f p e r s o n a l i t y and c a r d i o v a s c u l a r h a b i t u a t i o n i n v o l v i n g n o n - c l i n i c a l p o p u l a t i o n s have y i e l d e d i n c o n c l u s i v e r e s u l t s ( B a r r a t t , 1968; Dykman e t a l , 1959; G a l b r e c h t e t a l . , 1965; I s r a e l , 1969; K o r i a t e t a l . , 1 9 7 3 ) . The o v e r a l l r e s u l t i s t h a t h y p o t h e s e s i n v o l v i n g p e r s o n a l i t y measures have a l i m i t e d r ange o f a p p l i c a b i l i t y i n d i s c u s s i o n s o f h a b i t u a t i o n o f c a r d i o v a s c u l a r r e s p o n s e s . C h a r a c t e r i s t i c s o f t h e s u b j e c t , i n d e p e n d e n t o f p e r s o n a l i t y v a r i a b l e s w h i c h have been s u g g e s t e d as p o t e n t i a l c o n f o u n d i n g f a c t o r s i n t h e measurement o f r e s p o n s e h a b i t u a t i o n a r e g e n d e r , a g e , method o f r e c r u i t m e n t f o r t h e s t u d y , a e r o b i c f i t n e s s l e v e l , and s u b j e c t m e n t a t i o n d u r i n g t he t a s k . McGu i ne s s (1973 ) r e p o r t e d t h a t f e m a l e s t o o k l o n g e r t h a n ma l e s t o h a b i t u a t e t o an - 34 -a u d i t o r y s t i m u l u s on a measure o f f o r e a r m b l o o d v o l ume . C r o s s - g e n d e r d i f f e r e n c e s i n b l o o d p r e s s u r e o r h e a r t r a t e h a b i t u a t i o n have no t been r e p o r t e d . The e f f e c t s o f age on h a b i t u a t i o n and r e a c t i v i t y have a l s o n o t been s t u d i e d i n d e t a i l ( 0 'Go rman , 1 9 7 7 ) . S t e r n (1968 ) r e p o r t e d t h a t t h e s k i n c o n d u c t a n c e r e s p o n s e s t o a c o o l a i r s t i m u l u s i n a d u l t s h a b i t u a t e d more r a p i d l y t h a n i n c h i l d r e n . More r e c e n t l y G reen (1976) o b s e r v e d no d i f f e r e n c e s i n s k i n c o n d u c t a n c e r e s p o n s e o r h e a r t r a t e h a b i t u a t i o n i n a c o m p a r i s o n o f c h i l d r e n and c o l l e g e u n d e r g r a d u a t e s . Some e v i d e n c e e x i s t s t h a t s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y i s n o t a s s t r o n g l y l i n k e d t o age as i s h e a r t r a t e r e a c t i v i t y ( G l a s s e t a l . , 1 9 8 3 ) . The e f f e c t s o f age on b l o o d p r e s s u r e h a b i t u a t i o n however have n o t y e t been c l o s e l y e x a m i n e d . B l o o d p r e s s u r e i s known t o i n c r e a s e w i t h a ge , and t h e r e i s a l s o e v i d e n c e t h a t h y p e r t e n s i v e s show s l o w e r h a b i t u a t i o n (Baumann, Z i p r i a n , G o d i c k e , H a r t r o d t , Naumann, & L a u t e r , 1 9 7 3 ) , and s l o w e r r e c o v e r y f o l l o w i n g a m e n t a l a r i t h e m t i c t a s k ( B r o d , 1960) t h a n do n o r m o t e n s i v e s . _ G i v e n t h e s e two p i e c e s o f e v i d e n c e f u t u r e r e s e a r c h may s u c c eed i n e s t a b l i s h i n g a more d e f i n i t i v e p i c t u r e o f t h e r e l a t i o n s h i p between age and c a r d i o v a s c u l a r r e s p o n s e h a b i t u a t i o n . K o t s e s , G l a u s and F i s h e r ( 1974 ) s t u d i e d t h e e f f e c t o f d i f f e r e n t s u b j e c t r e c r u i t m e n t p r o c e d u r e s on c a r d i a c r e s p o n s i v e n e s s t o n o i s e . No d i f f e r e n c e s between g r oup s v o l u n t e e r i n g , c o n s c r i p t e d , o r b e i n g p a i d f o r t h e s t u d y were o b s e r v e d i n t e rms o f h a b i t u a t i o n o f h e a r t r a t e . The e f f e c t o f d i f f e r e n t r e c r u i t m e n t p r o c e d u r e s on r e s p o n s e s t o c o g n i t i v e s t r e s s o r s has no t been r e p o r t e d . An i n d i v i d u a l ' s a b i l i t y t o cope w i t h p s y c h o l o g i c a l s t r e s s i s a l s o med i a t e d by h i s o r he r l e v e l o f a e r o b i c f i t n e s s ( F o l k i n s & S ime , 1981 ; Mo rgan , 1 9 8 2 ) . P h y s i o l o g i c a l c o r r e l a t e s o f a e r o b i c f i t n e s s may m e d i a t e o n e ' s s u b j e c t i v e e x p e r i e n c e o f a g i v e n s t r e s s o r and o n e ' s s ub sequen t r e a c t i v i t y l e v e l and r a t e - 35 -o f h a b i t u a t i o n . The r e l a t i o n s h i p be tween a e r o b i c f i t n e s s l e v e l and c a r d i o v a s c u l a r h a b i t u a t i o n t o a r e p e a t e d s t r e s s o r ha s n o t been a d d r e s s e d . S e v e r a l s t u d i e s have however examined p o s t s t r e s s r e c o v e r y r a t e s and t h e i r r e l a t i o n s h i p t o a e r o b i c f i t n e s s l e v e l . H o l l a n d e r and S e r a g a n i a n (1984 ) s t u d i e d t h e r e l a t i o n s h i p between i n d i v i d u a l - s p e c i f i c c a r d i o v a s c u l a r r e s p o n s e s and a e r o b i c f i t n e s s l e v e l . The a u t h o r s measured p h y s i o l o g i c a l r e a c t i v i t y d u r i n g and f o l l o w i n g e x p o s u r e t o a m e n t a l a r i t h m e t i c t a s k and f ound t h a t a e r o b i c f i t n e s s l e v e l was u n r e l a t e d t o h e a r t r a t e d u r i n g t h e t a s k . Cox , E v a n s , and J a m i e s o n ( 1979 ) a l s o r e p o r t e d t h a t h e a r t r a t e r e a c t i v i t y d i d n o t v a r y as a f u n c t i o n o f t h e s u b j e c t ' s a e r o b i c f i t n e s s l e v e l . F o l l o w i n g t h e m e n t a l a r i t h m e t i c t a s k H o l l a n d e r and S e r a g a n i a n (1984 ) f ound howeve r , t h a t a e r o b i c f i t n e s s l e v e l was p o s i t i v e l y c o r r e l a t e d w i t h speed o f p o s t t a s k h e a r t r a t e r e c o v e r y t o b a s e l i n e . S i n y o r , S c h w a r t z , P e r r o n e t , B r i s s o n , and S e r a g a n i a n (1983 ) a l s o f ound t h a t a e r o b i c a l l y f i t s u b j e c t s showed f a s t e r h e a r t r a t e r e c o v e r y f r om a m e n t a l a r i t h m e t i c p l u s n o i s e s t r e s s o r . These f i n d i n g s s u g g e s t t h e r e l a t i o n between p h y s i o l o g i c a l r e a c t i v i t y and a e r o b i c f i t n e s s c e n t r e s n o t upon i n i t i a l magn i t ude o f r e s p o n s e bu t upon t h e d u r a t i o n o f t i m e f o r w h i c h a r o u s a l p r e v a i l s . F u t u r e r e s e a r c h s h o u l d f o c u s on t h e r o l e o f a e r o b i c f i t n e s s i n m e d i a t i n g p h y s i o l o g i c a l h a b i t u a t i o n and i t s p o s s i b l e i m p o r t a n c e i n a m e l i o r a t i n g t h e e f f e c t s o f c h r o n i c e x p o s u r e t o s t r e s s . S u b j e c t m e n t a t i o n d u r i n g t h e s t r e s s t a s k has a l s o been s u g g e s t e d by some a u t h o r s as a p o s s i b l e s o u r c e o f e r r o r v a r i a n c e i n s t u d i e s o f h a b i t u a t i o n ( B a r r a t t , 1972; G a l e , 1973; L u b o r s k y , 1 9 6 7 ) . Dykman, R e e s e , G a l b r e c h t , and Thomasson ( 1959 ) a t t e m p t e d t o a s s e s s t h e s u b j e c t i v e s t a t e o f t h e s u b j e c t d u r i n g h a b i t u a t i o n t h r o u g h t h e use o f a p o s t s t r e s s o r i n t e r v i e w . On l y s e l f - r a t e d a n x i e t y showed a p o s i t i v e c o r r e l a t i o n t o p h y s i o l o g i c a l i n d i c e s o f a r o u s a l . More r e c e n t l y , Neary and Zuckerman (1976) r e p o r t e d a s i g n i f i c a n t - 36 -r e l a t i o n s h i p between s e l f - r a t e d a n x i e t y and h a b i t u a t i o n o f s k i n c o n d u c t a n c e r e s p o n s e s t o an a u d i t o r y s t i m u l u s . O'Gorman (1977) r e v i e w e d t he l i t e r a t u r e on m e n t a l e x p e r i e n c e and h a b i t u a t i o n . No s t u d i e s i n v o l v i n g c a r d i o v a s c u l a r measu res were c i t e d . O'Gorman c o n c l u d e d t h a t i n t e rms o f e l e c t r o d e r m a l measu res s u b j e c t m e n t a t i o n does n o t e x e r t a s t r o n g i n f l u e n c e on r e s p o n s e h a b i t u a t i o n . F u t u r e s t u d i e s o f t h e e f f e c t s o f c o g n i t i o n and i m a g i n a t i o n on b o t h c a r d i o v a s c u l a r r e a c t i v i t y and h a b i t u a t i o n s h o u l d be c o n d u c t e d . A d a p t a t i o n and B a s e l i n e . R e a c t i v i t y o r h a b i t u a t i o n measures o f c a r d i o v a s c u l a r f u n c t i o n d e r i v e t h e i r mean ing t h r o u g h c o m p a r i s o n o f t h e s e measu res w i t h c o r r e s p o n d i n g measures made on t h e same i n d i v i d u a l bu t unde r r e s t i n g , o r b a s e l i n e , c o n d i t i o n s . Because t h e a t t a c h m e n t o f r e c o r d i n g d e v i c e s i s l i k e l y t o p r oduce an a r o u s i n g e f f e c t on t h e s u b j e c t i t i s n e c e s s a r y t o p r e c e d e measurement o f b a s e l i n e v a l u e s w i t h a p e r i o d o f i n a c t i v i t y and q u i e t d u r i n g w h i c h t h e s u b j e c t may a d a p t t o t h e e x p e r i m e n t a l s e t t i n g . The r e i s howeve r , some c o n t r o v e r s y r e g a r d i n g t h e o p t i m a l p e r i o d needed t o a c h i e v e s t a b i l i z a t i o n o f b l o o d p r e s s u r e o r h e a r t r a t e m e a s u r e s . I n a r e c e n t r e v i e w o f t h e l i t e r a t u r e on p h y s i o l o i g c a l p r e - s t r e s s a d a p t a t i o n ( L i n d e n & M c E a c h e r n , 1985) t h e a u t h o r s examined t he q u e s t i o n o f e f f e c t s o f t h e d u r a t i o n o f a d a p t a t i o n p e r i o d s on s t a b i l i z a t i o n o f v a r i o u s p h y s i o l o g i c a l r e s p o n s e p a r a m e t e r s . The a u t h o r s n o t e d s u b s t a n t i a l v a r i a b i l i t y i n t h e l e n g t h o f a d a p t a t i o n p e r i o d s b e i n g emp loyed i n v a r i o u s s t u d i e s . These p e r i o d s r a n g e d i n l e n g t h f r om 5 m i n u t e s (Benthem & G l a r o s , 1978) t o 60 m i n u t e s (Drummond, 1 9 8 3 ) . On l y two o f 35 s t u d i e s r e p o r t e d e m p i r i c a l d a t a on o b s e r v e d changes i n p h y s i o l o g i c a l a c t i v i t y d u r i n g p r e s t r e s s a d a p t a t i o n . L i n d e n and McEache rn ( 1985 ) c o n c l u d e d t h a t t h e r e i s some e v i d e n c e t h a t h e a r t r a t e t e n d s t o be f a i r l y s t a b l e whe reas b l o o d p r e s s u r e t e n d s t o d e c r e a s e c o n t i n u o u s l y o v e r a 2 0 - m i n u t e a d a p t a t i o n p e r i o d . I t r e m a i n s u n c e r t a i n a s t o how l o n g f u l l - 3 7 -s t a b i l i z a t i o n o f b l o o d p r e s s u r e may r e q u i r e . W h i l e t h e c h o i c e o f an o p t i m a l l e n g t h o f a d a p t a t i o n p e r i o d r e m a i n s u n c l e a r , Zwaga ' s ( 1973 ) s u g g e s t i o n t h a t t h e e n t i r e t i m e s p e n t i n t h e l a b o r a t o r y s h o u l d be v i ewed as a s o u r c e o f v a l u a b l e d a t a a p p e a r s w a r r a n t e d . L i n d e n and McEache rn ( 1985 ) a l s o a d d r e s s e d t he q u e s t i o n o f a p p r o p r i a t e d e f i n i t i o n o f b a s e l i n e v a l u e s . O b r i s t ( 1 9 8 1 ) , f o r examp le had a r gued t h a t a c c u r a t e d e t e r m i n a t i o n o f b a s a l hemodynamic l e v e l s c anno t be made d u r i n g t h e same r e c o r d i n g s e s s i o n a t w h i c h a s t r e s s o r i s p r e s e n t e d , due t o a n t i c i p a t o r y a r o u s a l . O b r i s t p r e s e n t e d e v i d e n c e t h a t t h e magn i t ude o f h e a r t r a t e and p r e s s o r changes s c o r e s i n r e s p o n s e t o a g i v e n s t r e s s o r a r e u n d e r e s t i m a t e d when c a l c u l a t e d as changes f r om b a s e l i n e measures made i m m e d i a t e l y p r i o r t o t h e p r e s e n t a t i o n o f t h e s t r e s s o r . Meye r s and C r a i g h e a d ( 1978 ) on t h e o t h e r hand a r gued t h a t t h e u se o f m i n u t e 6 o f a 20 -m i nu t e a d a p t a t i o n p e r i o d as a b a s e l i n e v a l u e wou l d a l l o w f o r adequa t e p h y s i o l o g i c a l s t a b i l i z a t i o n and a t t h e same t i m e a v o i d t h e p r ob l em o f a n t i c i p a t o r y a r o u s a l . W h i l e numerous o t h e r s t u d i e s ( E l l i o t t , 1975 ; Mona t , A v e r i l l , & L a z a r u s , 1972 ; Mona t , 1976; Rakove r & L e v i t a , 1973) c o n f i r m t h e e x i s t e n c e o f a n t i c i p a t o r y a r o u s a l p r i o r t o s t i m u l u s o n s e t i t i s p o s s i b l e t h a t t h i s b a s e l i n e p r ob l em i s e x a g g e r a t e d i n O b r i s t ' s d a t a by t h e f a c t t h a t h i s s u b j e c t s e x p e c t e d a v e r s i v e s h o c k s . I n t h e c a s e o f Meye r s and C r a i g h e a d (1978) t h e i r c h o i c e o f m i nu t e 6 a s an o p t i m a l b a s e l i n e a p p e a r s a r b i t r a r y g i v e n t h e f a c t t h a t change a c r o s s v a r i o u s p h y s i o l o i g c a l r e s p o n s e s y s t ems i s a s y n c h r o n o u s and v a r i o u s measures a r e n o t c o n s i s t e n t l y a t t h e i r l o w e s t l e v e l s a t m i nu t e 6 . I n t h e i r r e v i e w o f t h e l i t e r a t u r e , L i n d e n and McEache rn (1985 ) f ound t h a t t h e most f r e q u e n t l y u s ed b a s e l i n e v a l u e was t h e a v e r a g e o f m i n u t e s t o 1 t o 5 o f t h e a d a p t a t i o n p e r i o d . C l e a r l y , t h i s c h o i c e o f b a s e l i n e s a l s o does n o t a d e q u a t e l y a d d r e s s t h e a f o r e m e n t i o n e d p r ob l ems r e g a r d i n g s t a b i l i z a t i o n o f - 38 -p h y s i o l o g i c a l p a r a m e t e r s and a n t i c i p a t o r y a r o u s a l . The a u t h o r s n o t e t h a t i n r e s e a r c h w i t h i n f o r m e d s u b j e c t s e x p e r i m e n t e r s c an e x p e c t a r e v e r s e d J - s h a p e a r o u s a l c u r v e d u r i n g p r e s t r e s s a d a p t a t i o n f r om t h e f i r s t m i n u t e o f o b s e r v a t i o n t o t h e immed i a t e p r e s t r e s s p e r i o d . They s u g g e s t s t a b l e r e s p o n s e s o ve r a s e r i e s o f r e a d i n g s t a k e n d u r i n g a l a t e r bu t n o t t h e f i n a l segment o f p r e s t r e s s p e r i o d may be c o n s i d e r e d t h e b e s t a p p r o x i m a t i o n o f a " t r u e " b a s e l i n e . R e a d i n g s t a k e n a t t h i s p o i n t wou l d r e p r e s e n t t h e presumed bo t t om o f t h e r e v e r s e d J a r o u s a l c u r v e . I n d e f i n i n g s u ch a b a s e l i n e i n d i v i d u a l - s p e c i f i c o r g roup mean s c o r e s c o u l d be emp l o yed . I n s t r u c t i o n e f f e c t s . I a c ono and L y k k e n ( 1983 ) f ound t h a t s k i n c o n d u c t a n c e r e s p o n s e s c an be a f f e c t e d by t h e t y p e o f p r e - t a s k i n s t r u c t i o n s p r o v i d e d . I n s t r u c t i o n s t o a t t e n d t o a s t i m u l u s o r n e u t r a l i n s t r u c t i o n s d e c r e a s e d h a b i t u a t i o n o f r e s p o n s e s ; w h i l e i n s t r u c t i o n s t o i g n o r e t h e s t i m u l u s s e r v e d t o f a c i l i t a t e h a b i t u a t i o n . The p r o v i s i o n o f an a l t e r n a t i v e f o c u s f o r t h e s u b j e c t s ' a t t e n t i o n a l s o i n c r e a s e d h a b i t u a t i o n o f r e s p o n s e s d u r i n g n e u t r a l p r e - t a s k i n s t r u c t i o n s . Drummond (1983) f ound t h e g r e a t e s t be tween -g roup ( h y p e r t e n s i v e s v e r s u s n o r m o t e n s i v e s ) d i f f e r e n c e s i n h e a r t r a t e d u r i n g n e u t r a l p r e - t a s k i n s t r u c t i o n s . No d i f f e r e n c e s i n b l o o d p r e s s u r e were s e e n . The r e s u l t s o f t h e s e two s t u d i e s i n d i c a t e t h a t s u b j e c t s ' f o c u s o f a t t e n t i o n and s u b s e q u e n t l e v e l o f r e a c t i v i t y may be s e n s i t i v e t o t h e t y p e o f i n s t r u c t i o n s p r o v i d e d . To a v o i d t h e p o t e n t i a l c o n f o u n d i n g e f f e c t s o f t y p e o f i n s t r u c t i o n s r e s e a r c h e r s s h o u l d p r o v i d e s p e c i f i c t a s k i n s t r u c t i o n s o n l y a f t e r t h e c o m p l e t i o n o f t h e p r e s t r e s s a d a p t a t i o n p e r i o d . A p o s t - i n s t r u c t i o n , w a i t i n g p e r i o d s h o u l d s e p a r a t e t h e p r o v i s i o n o f i n s t r u c t i o n s f r om t h e f i r s t p r e s e n t a t i o n o f t h e e x p e r i m e n t a l s t r e s s o r . The i n c l u s i o n o f s u c h a b r i e f w a i t i n g p e r i o d wou l d s e r v e t o m i n i m i z e t h e e f f e c t s o f i n s t r u c t i o n - r e l a t e d a n t i c i p a t o r y a r o u s a l on i n i t i a l s t r e s s r e s p o n s e l e v e l s . - 3 9 - \ Task C h a r a c t e r i s t i c s . I n a s s e s s i n g t h e r e l a t i o n s h i p between a c u t e c a r d i o v a s c u l a r r e a c t i v i t y and s ub sequen t r e s p o n s e h a b i t u a t i o n t o a r e p e a t e d s t r e s s o r a number o f t a s k c h a r a c t e r i s t i c s a r e o f i m p o r t a n c e . F i r s t , t h e t a s k must be one w h i c h r e l i a b l y e voke s s i g n i f i c a n t c a r d i o v a s c u l a r r e s p o n s e s . S e c o n d , t h e t a s k must y i e l d a s i g n i f i c a n t r ange o f i n d i v i d u a l d i f f e r e n c e s i n r e a c t i v i t y . T h i r d , t h e t a s k must show good t e s t - r e t e s t r e l i a b i l i t y and i n d i v i d u a l r e s p o n s e s t e r e o t y p y . A r e v i e w o f t h e l i t e r a t u r e on t a s k - s p e c i f i c e f f e c t s a s s o c i a t e d w i t h a m e n t a l a r i t h m e t i c p l u s n o i s e s t r e s s o r r e v e a l s t h a t s u c h a s t r e s s o r s a t i s f i e d ea ch o f t h e a f o r e m e n t i o n e d c r i t e r i a ( S c h u l t e e t a l . , 1981 ; L a n e , 1 9 8 4 ) . N o v e l t y e f f e c t s o r t h e e f f e c t s o f p r i o r e x p o s u r e t o t h e s t r e s s o r on r e a c t i v i t y a r e a l s o o f i n t e r e s t . O ' N e i l l and H i n t o n ( 1 9 7 9 ) , f o r e xamp l e , f ound t h a t t h e h y p o t h e s i s o f d e c r e a s e d h e a r t r a t e v a r i a b i l i t y d u r i n g an a t t e n t i o n a l t a s k , r e l a t i v e t o a r e s t i n g b a s e l i n e p e r i o d , was s u p p o r t e d o n l y when t h e s u b j e c t had p r e v i o u s e x p e r i e n c e i n t h e t e s t s i t u a t i o n . The e f f e c t s o f p r i o r e x p o s u r e t o a d i f f e r e n t s t r e s s o r have a l s o been i n v e s t i g a t e d . V o s s e l and Laux ( 1978 ) exposed s u b j e c t s t o a d i f f e r e n t s t r e s s o r i n ea ch o f two e x p e r i m e n t a l s e s s i o n s . S u b j e c t s p r e v i o u s l y exposed t o a g i v e n s t r e s s o r showed a d e c r e a s e i n h e a r t r a t e r e a c t i v i t y t o a n o v e l s t r e s s o r i n a s ub sequen t t e s t i n g p h a s e . I n o r d e r t o c o n t r o l f o r thes p o s s i b l e e f f e c t s o f p r i o r e x p e r i e n c e on p h y s i o l o g i c a l r e s p o n s i v i t y , r e s e a r c h e r s s h o u l d employ o n l y n a i v e s u b j e c t s who have no t p r e v i o u s l y p a r t i c i p a t e d i n s t r e s s r e s p o n s e r e s e a r c h . Task c h a r a c t e r i s t i c s a r e a l s o r e l e v a n t t o t h e a s s e s smen t o f c a r d i o v a s c u l a r r e s p o n s e h a b i t u a t i o n . F i r s t , t h e t a s k must be c o n s i s t e n t l y a d m i n i s t e r e d a c r o s s e a ch t r i a l . S t i m u l i w h i c h v a r y f r om t r i a l t o t r i a l r e s u l t i n s l o w e r h a b i t u a t i o n (O 'Go rman , 1 9 7 7 ) . S i n c e h a b i t u a t i o n i s c o n s i d e r e d t o depend on t h e s u b j e c t ' s a p p r a i s a l o f t h e s t i m u l u s c h a r a c t e r i s t i c s ( I a c o n o & L y k k e n , - 40 -1983) u n v a r y i n g s t i m u l i s h o u l d f a c i l i t a t e h a b i t u a t i o n . S u p p o r t f o r t h i s h y p o t h e s i s comes f r om t h e r e s e a r c h o f B e r l y n e , C raw, S a l a p a t e k and L e w i s ( 1 9 6 3 ) , and S p i n k s and S i d d l e ( 1 9 7 6 ) . More r e c e n t l y , p h y s i o l o g i c a l r e s p o n s e h a b i t u a t i o n has been f ound t o be d e l a y e d under c o n d i t i o n s o f h i g h s i g n a l v a l u e ( H u l s t j i n , 1 9 8 3 ) , and h i g h t a s k - r e l e v a n c e (Woes t enbu rg , V e r b a t e n , & S l a n g e n , 1 9 8 3 ) . S t r e s s o r c o m p l e x i t y may a l s o be i n c r e a s e d t h r o u g h t h e s i m u l t a n e o u s p r e s e n t a t i o n o f m u l t i p l e s t i m u l i , i . e , m e n t a l a r i t h m e t i c p l u s n o i s e . The p r e s e n t a t i o n o f m u l t i p l e s t r e s s o r s may s e r v e t o d e l a y r e s p o n s e h a b i t u a t i o n . A c o n f u s i n g p i c t u r e emerges however f r om a r e v i e w o f t h e l i t e r a t u r e on t h e e f f e c t s o f c o m p e t i n g s t i m u l i on h a b i t u a t i o n . Such t a s k s have been f ound t o d e l a y ( B o h l i n , 1 9 7 6 ) , and t o speed ( F r i t h & a l i e n , 1983) h a b i t u a t i o n ; w h i l e o t h e r s t u d i e s have f ound no e f f e c t ( v an 0 1 s t , H e e m s t r a , & t e n K o r t e n a a r , 1 9 7 9 ) . I t s h o u l d be n o t e d t h a t t h e s e s t u d i e s d i d n o t employ c o g n i t i v e s t r e s s o r s o r c a r d i o v a s c u l a r r e s p o n s e m e a s u r e s . A r e v i e w o f t h e r e l e v a n t l i t e r a t u r e r e v e a l e d t h a t t h e e f f e c t s o f s i m u l t a n e o u s s t r e s s o r s s u ch a s n o i s e i n t e r f e r e n c e and m e n t a l a r i t h m e t i c on c a r d i o v a s c u l a r r e s p o n s e h a b i t u a t i o n has no t been t h o r o u g h l y examined ( L i n d e n e t a l . , i n p r e s s ) . F i n a l l y , t h e s t r e s s o r must be o f s u f f i c i e n t d u r a t i o n so as t o a l l o w f o r an a c c u r a t e a s s e s smen t o f t h e p r e s e n c e o f h a b i t u a t i o n e f f e c t s . A l t h o u g h e x p e r i m e n t a l t a s k s have v a r i e d i n d u r a t i o n f r om 1 hou r t o a few m i n u t e s , r e s e a r c h e r s have g e n e r a l l y u sed s i n g l e s t r e s s t a s k s r e q u i r i n g f ewe r t h a n 15 m i n u t e s t o a d m i n i s t e r ( K r a n t z & Manuck , 1 9 8 4 ) . I n c i r c u m s t a n c e s where a c r o s s t a s k h a b i t u a t i o n i s o f i n t e r e s t s t i m u l u s r e p e t i t i o n i s n e c e s s a r y . S t i m u l u s r e p e t i t i o n and i n t e r - s t r e s s o r i n t e r v a l . The c h o i c e o f number o f s t i m u l u s r e p e t i t i o n s and l e n g t h o f i n t e r - s t r e s s o r i n t e r v a l a r e o f paramount i m p o r t a n c e i n any a t t e m p t t o a s s e s s r e s p o n s e h a b i t u a t i o n . As p r e v i o u s l y - 41 -n o t e d , ea ch s t i m u l u s p r e s e n t a t i o n must be o f s u f f i c i e n t d u r a t i o n so a s t o a l l o w w i t h i n s t r e s s o r h a b i t u a t i o n t o o c c u r . I n a d d i t i o n , t h e s t r e s s o r must be r e p e a t e d l y p r e s e n t e d w i t h i n a g i v e n s e s s i o n . A r e v i e w o f t h e l i t e r a t u r e on w i t h i n - s e s s i o n r e s p o n s e s t o a m e n t a l a r i t h m e t i c s t r e s s o r r e v e a l e d two c o n s i s t e n t r e s u l t s . F i r s t , i n d i v i d u a l s d i s p l a y an i d i o s y n c r a t i c p a t t e r n o f c a r d i o v a s c u l a r r e s p o n s i v i t y i n t e rms o f t h e i r i n i t i a l l e v e l o f r e a c t i v i t y t o e a ch s t r e s s o r p r e s e n t a t i o n ( L a c ey & L a c e y , 1962; Manuck & G a r l a n d , 1980; G l a s s e t a l . , 1984; M i n e r e t a l . , 1 9 8 4 ) . S e c o n d , w i t h i n e x p e r i m e n t a l s e s s i o n s r a n g i n g f r o m 2 m i n u t e s (Drummond, 1983) t o 1 hour ( F r a n k e n a e u s e r e t a l . , 1967) o t h e r s t u d i e s have d e m o n s t r a t e d c a r d i o v a s c u l a r r e s p o n s e h a b i t u a t i o n t o a m e n t a l a r i t h m e t i c t a s k on a v a r i e t y o f measures s u c h as h e a r t r a t e (Zwaga , 1973; J o n e s & J o h n s o n , 1975 ; Neus e t a l . , 1 9 8 1 ) , b l o o d p u l s e a m p l i t u d e ( T u r p i n & S i d d l e , 1 9 8 3 ) , and p u l s e t r a n s i t t i m e ( S t e p t o e , 1 9 7 7 ) . S o s n o w s k i ( 1983 ) a l s o r e p o r t e d s i g n i f i c a n t h a b i t u a t i o n o f h e a r t r a t e r e s p o n s e s t o a n o i s e s t i m u l i a c r o s s f i v e , 1 -m inu te t r i a l s . W h i l e t h e r e i s some e v i d e n c e t h a t women d i s p l a y g r e a t e r h e a r t r a t e h a b i t u a t i o n t h a n men t o a S t r o o p p e r c e p t i o n t a s k a c r o s s 3 , t w e n t y - m i n u t e t a s k p e r i o d s , gende r d i f f e r e n c e s i n r e s p o n s e t o h a b i t u a t i o n t o a m e n t a l a r i t h m e t i c p l u s n o i s e t a s k have n o t been r e p o r t e d . Taken t o g e t h e r t h e s e r e s u l t s s u g g e s t t h a t w i t h i n a g i v e n e x p e r i m e n t a l s e s s i o n an a c c u r a t e a s s e s smen t o f t a s k - s p e c i f i c h a b i t u a t i o n c an be a c h i e v e d o n l y t h r o u g h t h e use o f a r e l i a b l e s t r e s s o r r e p e a t e d a t s p e c i f i c d i s c r e t e t i m e i n t e r v a l s . Each s t r e s s t a s k s h o u l d be f o l l o w e d by a r e c o v e r y p e r i o d o f a t l e a s t e q u a l d u r a t i o n . Hokanson , DeGood, F o r r e s t , and B r i t t a i n ( 1971 ) n o t e d t h a t changes i n p h y s i o l o g i c a l p a r a m e t e r s a c r o s s s t r e s s o r t r i a l s v a r i e d as a f u n c t i o n o f t h e l e n g t h o f t h e between t r i a l r e c o v e r y p e r i o d . G i v e n t h e p o t e n t i a l c l i n i c a l s i g n i f i c a n c e o f c h r o n i c , r e p e a t e d e x p o s u r e t o s t r e s s (Cannon , 1932; F r a n k e n h a e u s e r , 1 9 8 0 ) , t h e i m p a c t o f l o n g e r - 42 -i n t e r - s t r e s s o r i n t e r v a l s i s a l s o o f i n t e r e s t . A t h o r o u g h r e v i e w o f t h e l i t e r a t u r e r e v e a l s t h e use o f i n t e r - v i s i t i n t e r v a l s r a n g i n g f r om one week (Manuck & S c h a e f f e r , 1978; Neus e t a l . , 1981) t o s e v e r a l months (Cohen & S e d l a c e k , 1982 ; Manuck & G a r l a n d , 1 9 8 0 ) . The e v i d e n c e s u g g e s t s t h a t i n t e r - v i s i t i n t e r v a l s r a n g i n g f r om one day t o s e v e r a l weeks p r oduce s u b s t a n t i a l r e t e n t i o n o f h a b i t u a t i o n e f f e c t s , i . e . , d e c r e a s e d c a r d i o v a s c u l a r r e a c t i v i t y and an i n c r e a s e d r a t e o f r e s p o n s e h a b i t u a t i o n ( G l a s e r , 1966; Neus e t a l . , 1 981 ; F r a n k e n h a e u s e r e t a l . , 1 9 6 7 ) . I n t e r - v i s i t i n t e r v a l s i n e x c e s s o f f o u r weeks appea r t o p r odu ce l i t t l e o r no r e t e n t i o n o f h a b i t u a t i o n e f f e c t s and s u b s t a n t i a l l y l e s s r e s p o n s e v a r i a b i l i t y (Cohen & S e d l a c e k , 1982 ; L udb r ook & W a l s h , 1982; Manuck & G a r l a n d , 1 9 8 0 ) . Summary. I n a r e v i e w o f f a c t o r s w h i c h i n f l u e n c e p h y s i o l o g i c a l h a b i t u a t i o n , O'Gorman (1977 ) c o n c l u d e d t h a t f o r t h e f o l l o w i n g f a c t o r s t h e r e i s s t r o n g e v i d e n c e o f t h e i r i n f l u e n c e : s u b j e c t g e n d e r , i n t e r - s t i m u l u s i n t e r v a l , s t i m u l u s c o m p l e x i t y and i n t e n s i t y , s u b j e c t ' s e x p e c t a t i o n s , and p r e v i o u s h a b i t u a t i o n t o t h e same s t i m u l u s w i t h i n a p e r i o d o f one mon th . The m a j o r i t y o f s t u d i e s r e v i e w e d i n v o l v e d e l e c t r o d e r m a l m e a s u r e s . The e v i d e n c e r e g a r d i n g t h e i n f l u e n c e o f s u c h f a c t o r s on c a r d i o v a s c u l a r r e s p o n s e s i s n o t a s e x t e n s i v e o r a s c o n c l u s i v e . I n a more r e c e n t r e v i e w and m e t h o d o l o g i c a l c r i t i q u e ( K r a n t z & Manuck, 1984) o f a c u t e c a r d i o v a s c u l a r r e a c t i v i t y and i t s r e l a t i o n s h i p t o c o r o n a r y d i s e a s e t h e a u t h o r s i d e n t i f i e d s i m i l a r i n d i v i d u a l - s p e c i f i c and s i t u a t i o n - s p e c i f i c f a c t o r s a s i m p o r t a n t i n f l u e n c e s on c a r d i o v a s c u l a r r e a c t i v i t y . S e l e c t i o n o f r e s p o n s e m e a s u r e s . A t h o r o u g h e v a l u a t i o n o f c a r d i o v a s c u l a r r e a c t i v i t y and h a b i t u a t i o n based on t e c h n i q u e s commonly emp loyed i n p s y c h o p h y s i o l o g i c s t u d i e s wou l d i n c l u d e s i m u l t a n e o u s a s s e s smen t o f s y s t o l i c and d i a s t o l i c b l o o d p r e s s u r e , mean a r t e r i a l p r e s s u r e , s t r o k e vo l ume , s y s t o l i c - 43 -t i m e i n t e r v a l s , and h e a r t r a t e ( K r a n t z & Manuck, 1 9 8 4 ) . Such an a p p r o a c h i s b o t h t i m e - c o n s u m i n g and e x p e n s i v e . S e v e r a l o f t h e m e t h o d o l o g i c a l q u e s t i o n s p r e s e n t e d e a r l i e r do however s u g g e s t some g e n e r a l g u i d e l i n e s f o r t h e s e l e c t i o n o f r e s p o n s e m e a s u r e s . F i r s t , a s n o t e d by S t e p t o e ( 1 9 8 0 ) , p h y s i o l o g i c a l measures s h o u l d be u n o b t r u s i v e , a u t o m a t i c , and f r e q u e n t . S e c o n d , t h e c h o i c e o f p h y s i o l o g i c a l v a r i a b l e s t o be r e c o r d e d i s b e s t g u i d ed by t he h y p o t h e s e s t o be t e s t e d . Where hemodynamic r e s p o n s e c h a r a c t e r i s t i c s a r e o f i n t e r e s t , measures o f t a s k - r e l a t e d changes i n h e a r t r a t e and b l o o d p r e s s u r e a r e most f r e q u e n t l y t h e v a r i a b l e s o f c h o i c e . T h i r d , i n a d d i t i o n t o c h o o s i n g a p p r o p r i a t e r e s p o n s e mea su r e s , e x p e r i m e n t e r s must d e c i d e when p h y s i o l o g i c a l r e c o r d i n g s w i l l be made d u r i n g a l a b o r a t o r y s e s s i o n . C o n t i n u o u s measurement o f some v a r i a b l e s , e . g . , h e a r t r a t e , i s r e a d i l y a c h i e v e d , w h i l e o t h e r v a r i a b l e s s u ch as b l o o d p r e s s u r e can be samp led o n l y a t d i s c r e t e t i m e i n t e r v a l s . To e n su r e measurement r e l i a b i l i t y i n v e s t i g a t o r s must c o l l e c t m u l t i p l e r e c o r d i n g s f o r each au t onom i c pa r ame te r o f i n t e r e s t . - F i n a l l y , i f r e p e a t e d e x p e r i m e n t a l s t r e s s o r s a r e u sed i t i s n e c e s s a r y t o i n t e r p o s e b a s e l i n e o r r e c o v e r y p e r i o d s between each s t r e s s o r p r e s e n t a t i o n . S u b j e c t s ' r e s p o n s i v i t y t o ea ch t a s k w i l l t h en r e f l e c t changes f r om r e s t i n g v a l u e s r a t h e r t h a n changes f r om r e s p o n s e l e v e l s a c h i e v e d d u r i n g i m m e d i a t e l y p r e c e d i n g t a s k p e r i o d s . Two i s s u e s s p e c i f i c a l l y r e l a t e d t o t h e measurement o f a c u t e c a r d i o v a s c u l a r r e a c t i v i t y a r e a l s o r e l e v a n t t o t h e a p p r o p r i a t e s e l e c t i o n o f r e s p o n s e m e a s u r e s . F i r s t , a r e v i e w o f t h e l i t e r a t u r e ( K r a n t z & Manuck, 1984) r e v e a l s t h a t t h e r e i s no c on sen su s as t o t h e b e s t d e f i n i t i o n o f r e a c t i v i t y . K r a n t z and Manuck (1984 ) n o t e d t h a t r e a c t i v i t y has been v a r i o u s l y d e f i n e d as a b s o l u t e changes f r om b a s e l i n e , changes a d j u s t e d f o r b a s e l i n e , and a v e r a g e s t r e s s r e s p o n s e l e v e l . A b s o l u t e changes s c o r e s a r e t h e most f r e q u e n t l y used measure o f r e a c t i v i t y . R e c e n t l y howeve r , some a u t h o r s have recommended t he use o f - 44 -c o v a r i a n c e t e c h n i q u e s t o d e f i n e measu res o f change w h i c h a r e i n d e p e n d e n t o f b a s a l l e v e l s ( G l a s s e t a l . , 1984; L i n d e n e t a l . , i n p r e s s ) . S e c o n d , t h e r e i s a l s o no c o n s e n s u s a s t o w h i c h r e s p o n s e measure p r o v i d e s t h e most r e l i a b l e and v a l i d measure o f r e a c t i v i t y . I t i s w e l l known t h a t v a r i o u s p h y s i o l o g i c a l r e s p o n s e s a r e m o d e s t l y c o r r e l a t e d and r e f l e c t t h e i n f l u e n c e o f d i f f e r e n t u n d e r l y i n g mechan i sms . O b r i s t e t a l . ( 1 9 7 8 ) , f o r e xamp l e , f ound t h a t m e n t a l a r i t h e m t i c p r oduced i n c r e a s e s i n h e a r t r a t e and s y s t o l i c b l o o d p r e s s u r e due t o common s y m p a t h e t i c a l l y m e d i a t e d , b e t a - a d r e n e r g i c i n f l u e n c e s . T a s k - r e l a t e d d i a s t o l i c p r e s s u r e changes were s a i d t o r e f l e c t an i n d e p e n d e n t r e s p o n s e d i m e n s i o n unde r t h e i n f l u e n c e o f p e r i p h e r a l v a s c u l a r r e s i s t a n c e . G i v e n t h i s f r a c t i o n a t i o n o f r e s p o n s e measu res v a r i o u s a u t h o r s have c ho s en t o employ d i f f e r e n t c a r d i o v a s c u l a r v a r i a b l e s a s i n d i c e s o f r e a c t i v i t y . O b r i s t and L i g h t ( O b r i s t e t a l . , 1978; L i g h t , 1981) a r gue t h a t h e a r t r a t e i s a s u p e r i o r measure o f r e a c t i v i t y due t o t h e f a c t t h a t h e a r t r a t e changes a r e most s e n s i t i v e t o t h e b e t a - a d r e n e r g i c mechan isms i m p l i c a t e d i n t h e p a t h o g e n e s i s o f c o r o n a r y d i s e a s e . G l a s s e t a l . ( 1984 ) a r g u e howeve r , t h a t s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y i s a s u p e r i o r c l a s s i f i c a t i o n v a r i a b l e in* t h a t s y s t o l i c r e a c t i v i t y i s i n d e p e n d e n t o f a g e - r e l a t e d c h a n g e s . The deg ree o f c o n c o r d a n c e between measu res o f b l o o d p r e s s u r e and h e a r t r a t e r e a c t i v i t y has n o t been e s t a b l i s h e d . The adequacy o f any s i n g l e measure o f r e a c t i v i t y seems q u e s t i o n a b l e . R e c en t work by Demb ro sk i and M c D o u g a l l ( 1983 ) p o i n t s o u t t h e a d v a n t a g e s o f s a m p l i n g m u l t i p l e r e s p o n s e d i m e n s i o n s . These a u t h o r s f o und t h a t i n d i v i d u a l s c o u l d be c l a s s i f i e d i n t o t h r e e c a r d i o v a s c u l a r r e s p o n s e p a t t e r n s on t h e b a s i s o f t h e i r r e s p o n s e s t o a m e n t a l a r i t h m e t i c t a s k . The f i r s t p a t t e r n i n v o l v e d i n c r e a s e d c a r d i a c ouput and d e c r e a s e d s y s t e m i c r e s i s t a n c e ; t h e s e cond showed d e c r e a s e d c a r d i a c oupu t and i n c r e a s e d p e r i p h e r a l r e s i s t a n c e ; w h i l e t h e t h i r d i n v o l v e d i n c r e a s e s i n b l o o d p r e s s u r e due t o i n c r e a s e d c a r d i a c o u t p u t , - 45 -w i t h s m a l l changes i n p e r i p h e r a l r e s i s t a n c e . These r e s u l t s u n d e r s c o r e t h e f a c t t h a t d i f f e r e n t p a t t e r n s o f r e s p o n d i n g may r e f l e c t t h e i n f l u e n c e s o f d i f f e r e n t mechan isms o f c a r d i o v a s c u l a r c o n t r o l . The a s s e s smen t o f r e s p o n s e h a b i t u a t i o n i n a g i v e n s t u d y a l s o depends on t h e p h y s i o l o g i c a l s y s t e m t o be e x a m i n e d , t h e method o f r e c o r d i n g , t h e method o f d a t a a n a l y s i s , and p a r t i c u l a r l y t h e i n d e x o f h a b i t u a t i o n t o be u s e d . D i f f e r e n c e s i n r e s p o n s e a m p l i t u d e between two o r more p o i n t s i n a s e r i e s o f t r i a l s have been t h e most w i d e l y u sed i n d e x f o r c o m p a r i s o n o f be tween g roup d i f f e r e n c e s i n r e s p o n s e h a b i t u a t i o n (O 'Go rman , 1 9 7 7 ) . T h i s method i n v o l v e s an a n a l y s i s o f v a r i a n c e on a m p l i t u d e o f r e s p o n s e o ve r t r i a l s f o r c o n t r a s t i n g g r oup s o f s u b j e c t s . A s i g n i f i c a n t g r o u p s - b y - t r i a l s i n t e r a c t i o n i s i n t e r p e t e d as e v i d e n c e o f a s i g n i f i c a n t d i f f e r e n c e i n h a b i t u a t i o n a c r o s s g r o u p s . As n o t e d by Huck and McLean (1975) t h i s i n t e r a c t i o n t e rm i s e q u i v a l e n t t o t h a t o b t a i n e d i n a one-way a n a l y s i s o f v a r i a n c e on d i f f e r e n c e s s c o r e s be tween t h e f i r s t and l a s t t r i a l s f o r t h e e x p e r i m e n t a l g r o u p s . R e c e n t l y , t h e u se o f b a s e l i n e c o v a r i a t e s i n an a n a l y s i s o f c o v a r i a n c e a p p r o a c h has been recommended a s a method o f r emov i ng t h e p o s s i b l e c o n f o u n d i n g e f f e c t s o f d i f f e r e n c e s i n b a s e l i n e l e v e l s on measu res o f r e s p o n s e h a b i t u a t i o n ( L i n d e n e t a l . , i n p r e s s ) . P u r p o s e o f t h e S t udy and E x p e r i m e n t a l H ypo t he s e s A r e v i e w o f t h e l i t e r a t u r e r e v e a l s a r e l a t i v e s c a r c i t y o f e v i d e n c e r e g a r d i n g t h e r e l a t i o n s h i p between a c u t e c a r d i o v a s c u l a r r e a c t i v i t y and s ub s equen t r e s p o n s e h a b i t u a t i o n t o p s y c h o l o g i c a l s t r e s s o r s s u c h as m e n t a l a r i t h m e t i c p l u s n o i s e . The p r e s e n t s t u d y was d e s i g n e d t o a d d r e s s s e v e r a l r e s e a r c h q u e s t i o n s i n t h i s a r e a . The p u r p o s e s o f t h e p r e s e n t s t u d y w e r e : 1. t o a n a l y z e t h e t i m e c o u r s e and p a t t e r n s o f b l o o d p r e s s u r e and h e a r t r a t e changes seen i n r e s p o n s e t o a m e n t a l a r i t h m e t i c p l u s n o i s e , e x p e r i m e n t a l s t r e s s o r . - 46 -2. to identify and compare patterns of blood pressure response in high versus low heart rate reactivity groups. 3. to identify and compare patterns of heart rate response in high versus low systolic blood pressure reactivity groups. 4. to compare systolic reactivity versus heart rate reactivity as subject classification variables. 5. to identify and compare the stability of patterns of heart rate versus systolic reactivity across a four-week interval. 6. to identify and compare the effect of single versus repeated exposure to the stressor on cardiovascular responses in high versus low reactor groups. 7. to identify and compare the effects of short, i.e., 3 minutes versus long, i.e., 4 weeks, inter-stressor intervals on cardiovascular responses in high versus low reactor groups. 8. to analyze the relationship between subject's perception of task d i f f i c u l t y , task importance, stressfulness of task, and perceived performance, acute cardiovascular reactivity and habituation of cardiovascular responses. With regard to the aforementioned purposes the following experimental hypotheses were tested: 1. heart rate and blood pressure responses to the stressor w i l l decrease within t r i a l s (3 minutes duration) and experimental sessions (3 t r i a l s per session), and across two sessions scheduled four weeks apart. 2. high heart rate reactors w i l l show greater decreases in blood pressure than low heart rate reactors. 3. high systolic blood pressure reactors w i l l show greater decreases in heart rate than low systolic reactors. - 47 -4 . s u b j e c t s c l a s s i f i e d a s h i g h h e a r t r a t e r e a c t o r s w i l l a l s o be h i g h s y s t o l i c r e a c t o r s . S i m i l a r o v e r l a p w i l l o c c u r i n t h e two l ow r e a c t i v i t y g r o u p s . 5 . r e p e a t e d e xpo su r e t o t h e s t r e s s o r w i l l i n c r e a s e t h e magn i t ude o f d e c r e a s e s i n r e s p o n s e i n a l l s u b j e c t s . The re w i l l a l s o be a s i g n i f i c a n t e x p o s u r e by r e a c t i v i t y i n t e r a c t i o n s u ch t h a t r e p e a t e d e x p o s u r e w i l l have g r e a t e r e f f e c t on h i g h r e a c t o r s . 6 . t h e magn i t ude o f d e c r e a s e s i n r e s p o n s e w i l l be n e g a t i v e l y c o r r e l a t e d w i t h t h e l e n g t h o f i n t e r - s t r e s s o r i n t e r v a l . 7 . r e p e a t e d e x p o s u r e t o t h e s t r e s s o r w i l l p r oduce a g r e a t e r d e c r e a s e d i n i t i a l l e v e l o f r e a c t i v i t y d u r i n g t h e s e cond e x p e r i m e n t a l s e s s i o n . 8 . t h e s u b j e c t s ' l e v e l o f r e a c t i v i t y w i l l be p o s i t i v e l y c o r r e l a t e d w i t h p e r c e i v e d t a s k s t r e s s f u l n e s s , d i f f i c u l t y , and i m p o r t a n c e and n e g a t i v e l y c o r r e l a t e d w i t h p e r c e i v e d p e r f o r m a n c e . The magn i t ude o f r e s p o n s e d e c r e a s e s w i l l be n e g a t i v e l y c o r r e l a t e d w i t h p e r c e i v e d t a s k s t r e s s f u l n e s s , d i f f i c u l t y , and i m p o r t a n c e , and p o s i t i v e l y c o r r e l a t e d w i t h p e r c e i v e d t a s k p e r f o r m a n c e . Method S y n o p s i s I n o r d e r t o t e s t t h e f o r e g o i n g h y p o t h e s e s a b e t w e e n - w i t h i n f a c t o r i a l d e s i g n was emp loyed i n t h e p r e s e n t s t u d y . The be tween -g r oups f a c t o r s were c o n d i t i o n s and r e a c t i v i t y g r o u p s , w h i l e t h e w i t h i n - s u b j e c t r e p e a t e d measu res were v i s i t s ( 2 ) , t r i a l s ( 3 ) , and m i n u t e s ( 3 ) . The c o n d i t i o n s v a r i a b l e i n v o l v e d e i t h e r r e p e a t e d o r s i n g l e e x p o s u r e t o t h e s t r e s s t a s k d u r i n g t h e f i r s t l a b o r a t o r y v i s i t . R e a c t i v i t y was d e f i n e d i n t e rms o f h e a r t r a t e and s y s t o l i c b l o o d p r e s s u r e r e s p o n s e s t o a m e n t a l a r i t h m e t i c p l u s n o i s e s t r e s s o r a d m i n i s t e r e d d u r i n g t h e f i r s t 3 -m i nu t e t r i a l i n t h e f i r s t e a ch o f two e x p e r i m e n t a l s e s s i o n s o v e r a f o u r - w e e k i n t e r v a l . The e x p e r i m e n t a l d e s i g n i s d i s p l a y e d i n T a b l e 3 . 48 TABLE 3 EXPERIMENTAL DESIGN: C o n d i t i o n 1 V i s i t 1 - 4 week i n t e r - v i s i t i n t e r v a l V i s i t 2 (N = 45 ) H i gh r e a c t o r s Low r e a c t o r s 20 m i n . , a d a p t a t i o n 3 X 3 m i n . s t r e s s t a s k s 3 X 3 m i n . i n t e r - s t r e s s o r r e s t p e r i o d s same as v i s i t 1 C o n d i t i o n 2 V i s i t 1 (N = 45 ) H i g h r e a c t o r s Low r e a c t o r s 20 m i n . , a d a p t a t i o n 1 X 3 m i n . s t r e s s t a s k 15 m i n . r e c o v e r y p e r i o d V i s i t 2 same as C o n d i t i o n 1, V i s i t 1 N o t e : The s u b j e c t s i n ea ch o f t h e e x p e r i m e n t a l c o n d i t i o n s w i l l be d i v i d e d i n t o r e a c t i v i t y t e r c i l e s on t h e b a s i s o f t h e i r a ) b l o o d p r e s s u r e a n d , b) h e a r t r a t e change s c o r e s . Method S u b j e c t s ' c h a r a c t e r i s t i c s . N i n e t y - s e v e n , n o r m o t e n s i v e , f e m a l e s u b j e c t s f r om a u n i v e r s i t y campus p o p u l a t i o n v o l u n t e e r e d t o p a r t i c i p a t e i n t h e p r e s e n t s t u d y . T h e i r p a r t i c i p a t i o n i n v o l v e d two e x p e r i m e n t a l s e s s i o n s o f f o r t y - f i v e m i n u t e s d u r a t i o n s e p a r a t e d by a f o u r - w e e k i n t e r v a l . S u b j e c t s were o f f e r e d c o u r s e c r e d i t f o r t h e i r p a r t i c i p a t i o n . Seven s u b j e c t s chose t o d r op ou t p r i o r t o c o m p l e t i n g t h e f u l l e x p e r i m e n t a l p r o c e d u r e . The mean age o f t h e r e m a i n i n g s u b j e c t s was 2 2 . 5 y e a r s (SD = 7 . 6 ) . S u b j e c t s r a nged i n age f r om 17 t o 45 y e a r s . T h e i r mean body w e i g h t was 124 . 2 l b s (SD = 1 5 . 5 ) w i t h a r ange o f 86 t o 170 l b s . The mean r e s t i n g h e a r t r a t e was 7 2 . 0 (SD = 1 0 . 1 ) b e a t s p e r m i n u t e . Mean b l o o d p r e s s u r e l e v e l s were 1 0 8 . 3 (SD = 1 0 . 7 ) mm Hg , 6 0 . 2 (SD = 8 . 1 ) mm Hg , and 7 8 . 5 (SD = 1 1 . 2 ) mm Hg f o r s y s t o l i c , d i a s t o l i c , and mean a r t e r i a l p r e s s u r e r e s p e c t i v e l y . A t t h e t i m e o f t h e i r f i r s t l a b o r a t o r y s e s s i o n e i g h t e e n s u b j e c t s were m e n s t r u a t i n g , w h i l e f i f t e e n were m e n s t r u a t i n g d u r i n g t h e second s e s s i o n f o u r week l a t e r . The number o f s u b j e c t s t a k i n g b i r t h c o n t r o l p i l l s d e c r e a s e d f r om twen t y d u r i n g t h e f i r s t s e s s i o n t o e i g h t e e n d u r i n g t h e s e cond s e s s i o n . E x p e r i m e n t a l s e t t i n g . A l l e x p e r i m e n t a l s e s s i o n s were c o n d u c t e d i n t h e c a r d i o v a s c u l a r p s y c h o p h y s i o l o g y l a b o r a t o r y a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , Depa r tmen t o f P s y c h o l o g y . Th roughou t t h e e x p e r i m e n t a l p r o c e d u r e t h e s u b j e c t and t h e e x p e r i m e n t e r were l o c a t e d i n s e p a r a t e r ooms . These rooms were c o n n e c t e d v i a an i n t e r c o m and a one-way m i r r o r . A l l s u b j e c t - e x p e r i m e n t a l c o m m u n i c a t i o n s were e x e c u t e d ove r t h e i n t e r c o m . I n a d d i t i o n , t h e b l o o d p r e s s u r e c u f f and c a b l e were f e d t h r o u g h a w a l l t o a s e p a r a t e room where t h e m i c r o c o m p u t e r and r e c o r d i n g u n i t were l o c a t e d . A p p a r a t u s and e q u i p m e n t . B l o o d p r e s s u r e and h e a r t r a t e measures were c o l l e c t e d v i a a Dinamap 8 4 5 , V i t a l S i g n s M o n i t o r ( C r i t i k o n C o r p o r a t i o n , Tampa, - 50 -F l o r i d a ) . The Dinamap 845 i s an au toma ted m o n i t o r w i t h d i g i t a l d i s p l a y s w h i c h u s e s t h e o s c i l l o m e t r i c method o f d a t a c o l l e c t i o n . P r e v i o u s r e s e a r c h e r s ( Y e l d e rman & Ream, 1979; Borow & Newburge r , 1982) have d e m o n s t r a t e d t h a t t h e Dinamap 845 p o s s e s s e s e x c e l l e n t r e l i a b i l i t y when compared t o i n v a s i v e measurement p r o c e d u r e s . The Dinamap 845 i s a l s o e q u i p p e d w i t h a s e l f - c a l i b r a t i o n f u n c t i o n f o r i n c r e a s e d r e l i a b i l i t y . C a r d i o v a s c u l a r dependen t m e a s u r e s . The Dinamap 845 p r o v i d e d an e s t i m a t i o n o f f o u r c a r d i o v a s c u l a r dependen t measures a t one m i nu t e i n t e r v a l s . These i n c l u d e d h e a r t r a t e , s y s t o l i c and d i a s t o l i c b l o o d p r e s s u r e , and mean a r t e r i a l p r e s s u r e . S y s t o l i c b l o o d p r e s s u r e i s an e s t i m a t i o n o f s y s t e m p r e s s u r e d u r i n g max ima l c o n t r a c t i o n o f t h e h e a r t . D i a s t o l i c b l o o d p r e s s u r e r e p r e s e n t s p r e s s u r e l e v e l s p r e s e n t d u r i n g d i a s t o l e o r max ima l r e l a x a t i o n o f t h e h e a r t m u s c l e . Mean a r t e r i a l p r e s s u r e i s d e f i n e d a s t h e l a r g e s t vo lume change d u r i n g e a ch c a r d i a c c y c l e . The b e h a v i o r a l s i g n i f i c a n c e o f mean a r t e r i a l p r e s s u r e has n o t been e s t a b l i s h e d . S e l f - r e p o r t m e a s u r e s . D u r i n g each o f t h e two e x p e r i m e n t a l s e s s i o n s s u b j e c t s were a s k e d t o c o m p l e t e a S t r e s s P e r c e p t i o n Q u e s t i o n n a i r e f o l l o w i n g t h e f i n a l p o s t - s t r e s s o r r e c o v e r y p e r i o d . The S t r e s s P e r c e p t i o n Q u e s t i o n n a i r e i s c o n t a i n e d i n A p p e n d i x 3 . T h i s q u e s t i o n n a i r e was composed o f f i v e , 1 0 - p o i n t L i k e r t s c a l e s r e g a r d i n g p e r c e i v e d s t r e s s , t a s k d i f f i c u l t y , t a s k i m p o r t a n c e , p e r c e i v e d p e r f o r m a n c e , and i n f l u e n c e o f mood on p e r f o r m a n c e . S t r e s s t a s k . A m e n t a l a r i t h m e t i c p l u s n o i s e s t r e s s o r was emp loyed i n t h e p r e s e n t s t u d y . F o r t h e f i r s t t r i a l , s u b j e c t s were i n s t r u c t e d t o c o n s e c u t i v e l y s u b t r a c t a g i v e n number , i . e . , 7 f r om t h e number 1 , 000 . The e x p e r i m e n t e r i n i t i a l l y mode led t h e p r o c e d u r e . S u b j e c t s were a l s o t o l d t h a t t h e e x p e r i m e n t e r was l i s t e n i n g v i a t h e i n t e r c o m and wou l d c oun t t h e number o f e r r o r s made. Ea ch s t r e s s t a s k was t h r e e m i n u t e s i n d u r a t i o n . I n o r d e r t o - 51 -r e d u c e t h e p o s s i b i l i t y o f p r a c t i c e e f f e c t s t h e number t o be s u b t r a c t e d was changed f o r ea ch t a s k p e r i o d . A l l s u b j e c t s c o m p l e t e d t he m e n t a l a r i t h m e t i c t a s k w h i l e l i s t e n i n g t o a 90 db w h i t e n o i s e p r e s e n t e d v i a a u d i o c a s s e t t e and s t e r e o headphones . The n o i s e s t i m u l u s t a p e was i n i t i a l l y c a l i b r a t e d t o a 90 db l e v e l by t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a A u d i o l o g y D e p a r t m e n t . P r o c e d u r e P r e - e x p e r i m e n t a l p r e p a r a t i o n s . A l l s u b j e c t s were c o n t a c t e d v i a t e l p h o n e and s c h e d u l e d f o r t h e i r f i r s t l a b o r a t o r y s e s s i o n . S u b j e c t s were s c r e e n e d f o r e a r l i e r p a r t i c i p a t i o n i n s i m i l a r s t r e s s r e s p o n s e e x p e r i m e n t s ( E l l i o t t , 1 9 6 6 ) . No s u b j e c t s needed t o be e x c l u d e d on t h e b a s i s o f t h i s c r i t e r i o n . P r i o r t o t h e i r p a r t i c i p a t i o n , a l l s u b j e c t s were g i v e n i n s t r u c t i o n s t o r e f r a i n f r om e n g a g i n g i n s t r e n u o u s p h y s i c a l e x e r c i s e , o r u se o f t o b a c c o , c a f f e i n e , o r a l c o h o l f o r 2 h o u r s p r i o r t o t h e i r s c h e d u l e d a p p o i n t m e n t . Each o f t h e s e f a c t o r s has p r e v i o u s l y been i d e n t i f i e d as h a v i n g an i n f l u e n c e on c a r d i o v a s c u l a r f u n c t i o n ( J e n n i n g s , B e r g , H u t c h e s o n , O b r i s t , P o r g e s , & T u r p i n , 1981 ; L a n e , 1984; D e m b r o s k i , 1 9 8 4 ) . P r e - s t r e s s a d a p t a t i o n . Upon a r r i v a l and f o l l o w i n g f a m i l i a r i z a t i o n w i t h t h e l a b o r a t o r y s e t t i n g , ea ch s u b j e c t was i n f o r m e d o f h e r r i g h t s a s a s u b j e c t and a s k e d t o s i g n a c o n s e n t f o r m . S u b j e c t s were t h en i n f o r m e d t h a t t h e y wou l d be c o m p l e t i n g a t w e n t y - m i n u t e a d a p t a t i o n p e r i o d and one o r more m e n t a l a r i t h m e t i c p l u s n o i s e t a s k s . The n a t u r e o f t h e s t r e s s o r s i n v o l v e d was b r i e f l y e x p l a i n e d . S u b j e c t s were a l s o g i v e n a b r i e f e x p l a n a t i o n o f t h e f u n c t i o n s o f t h e b l o o d p r e s s u r e c u f f and m o n i t o r . T h i s i n f o r m a t i o n was p r e s e n t e d u s i n g a s t a n d a r d i z e d s c r i p t , w h i c h i s c o n t a i n e d i n Append i x 4 . The b l o o d p r e s s u r e c u f f was t h e n a t t a c h e d t o t h e s u b j e c t ' s non -dom inan t a rm. D u r i n g t he a d a p t a t i o n p e r i o d s u b j e c t s r e s t e d c o m f o r t a b l y i n an a r m c h a i r . S u b j e c t s were a s k e d t o r e f r a i n f r om mov ing so a s t o d e c r e a s e t h e i n f l u e n c e o f movement a r t i f a c t s on t h e c a r d i o v a s c u l a r dependent m e a s u r e s . S u b j e c t s a l s o c o m p l e t e d a P a r - Q S c r e e n i n g Q u e s t i o n n a i r e ( B r i t i s h C o l u m b i a Depar tment o f H e a l t h , 1 9 7 5 ) . The P a r - Q i d e n t i f i e s p r e v i o u s o r c u r r e n t c a r d i o v a s c u l a r p r ob l ems and c u r r e n t usage o f c a r d i o a c t i v e m e d i c a t i o n s . T h i s q u e s t i o n n a i r e i s c o n t a i n e d i n A p p e n d i x 2 . S u b j e c t s a l s o p r o v i d e d i n f o r m a t i o n r e g a r d i n g t h e i r m e n s t r u a l p h a s e , u se o f b i r t h c o n t r o l , and l e v e l o f a e r o b i c f i t n e s s . F o l l o w i n g c o m p l e t i o n o f t h e a d a p t a t i o n p e r i o d a l l s u b j e c t s were s c r e e n e d f o r use o f c a r d i o a c t i v e m e d i c a t i o n , p r e v i o u s o r c u r r e n t c a r d i o v a s c u l a r d i f f i c u l t i e s , and r e s t i n g d i a s t o l i c b l o o d p r e s s u r e l e v e l g r e a t e r t h a n 90 mm H g . No s u b j e c t s needed t o be e x c l u d e d f r om f u r t h e r p a r t i c i p a t i o n on t h e b a s i s o f t h e s e s c r e e n i n g c r i t e r i a . E x p e r i m e n t a l c o n d i t i o n s . A l l s u b j e c t s were r andom ly a s s i g n e d t o one o f two e x p e r i m e n t a l c o n d i t i o n s . F o r t y - f o u r s u b j e c t s i n C o n d i t i o n 1 c o m p l e t e d t h e e n t i r e e x p e r i m e n t , w h i l e 46 s u b j e c t s d i d so i n C o n d i t i o n 2 . Those s u b j e c t s a s s i g n e d t o C o n d i t i o n 1 c o m p l e t e d a s e r i e s o f t h r e e s t r e s s t a s k s d u r i n g t h e f i r s t e x p e r i m e n t a l s e s s i o n . S u b j e c t s i n C o n d i t i o n 2 c o m p l e t e d o n l y one s t r e s s t a s k d u r i n g t h e f i r s t s e s s i o n . The f i r s t e x p e r i m e n t a l s e s s i o n i n C o n d i t i o n 1 began w i t h a 20 -m i nu t e p r e s t r e s s a d a p t a t i o n p e r i o d . T h i s a d a p t a t i o n p e r i o d was f o l l o w e d by a p r e - t a s k i n s t r u c t i o n p e r i o d d u r i n g w h i c h s u b j e c t s were g i v e n s p e c i f i c i n s t r u c t i o n s r e q u i r e d t o c o m p l e t e t h e m e n t a l a r i t h m e t i c s t r e s s t a s k . S u b j e c t s were en cou r aged t o c o n t i n u e c o u n t i n g f o r t h e e n t i r e t a s k p e r i o d . The p r e - t a s k i n s t r u c t i o n p e r i o d was f o l l o w e d by a two -m inu t e p r e - t a s k w a i t i n g p e r i o d . F o l l o w i n g t h e b a s e l i n e p e r i o d ea ch s u b j e c t c o m p l e t e d a s e r i e s o f t h r e e m e n t a l a r i t h m e t i c p l u s n o i s e t a s k s . Each t a s k was t h r e e m i n u t e s i n d u r a t i o n . Each t a s k p e r i o d was f o l l o w e d by a f i v e - m i n u t e r e c o v e r y p e r i o d . The S t r e s s P e r c e p t i o n Q u e s t i o n n a i r e was c o m p l e t e d f o l l o w i n g t h e f i n a l r e c o v e r y p e r i o d . - 53 -The f i r s t e x p e r i m e n t a l s e s s i o n i n C o n d i t i o n 2 began w i t h a d a p t a t i o n , p r e - t a s k i n s t r u c t i o n , and p r e - t a s k b a s e l i n e p e r i o d s w h i c h were i d e n t i c a l t o t h o s e a d m i n i s t e r e d i n C o n d i t i o n 1, v i s i t 1. I n C o n d i t i o n 2 , v i s i t 1, t h e p r e - t a s k b a s e l i n e was f o l l o w e d by a s i n g l e 3 -m inu t e t a s k p e r i o d . T h i s s i n g l e t a s k was f o l l o w e d by a 1 5 - m i n u t e r e c o v e r y p e r i o d . T h i s e x t e n d e d r e c o v e r y p e r i o d a l l o w e d s u b j e c t s i n b o t h c o n d i t i o n s t o spend t h e same l e n g t h o f t i m e unde r e x p e r i m e n t a l c o n d i t i o n s . S u b j e c t s i n C o n d i t i o n 2 c o m p l e t e d t h e S t r e s s P e r c e p t i o n Q u e s t i o n n a i r e a t t h e end o f t h e 1 5 - m i n u t e r e c o v e r y p e r i o d . A t t h e c o m p l e t i o n o f t h e f i r s t e x p e r i m e n t a l s e s s i o n a l l s u b j e c t s were r em i nded o f t h e i r commitment t o a s e cond s e s s i o n f o u r weeks l a t e r . S u b j e c t s were a s k e d no t t o d i s c u s s t h e f o r m a t o f t h e e x p e r i m e n t w i t h o t h e r p o t e n t i a l p a r t i c i p a n t s . A l l s u b j e c t s were c o n t a c t e d v i a t e l e p h o n e a few day s p r i o r t o t h e i r s e cond v i s i t and r em inded o f t h e i r s c h e d u l e d a p p o i n t m e n t t i m e and t h e n e c e s s a r y p r e - e x p e r i m e n t a l p r e p a r a t i o n s , i . e . , a b s t e n t i o n f r om t o b a c c o , a l c o h o l , c a f f e i n e , and e x e r c i s e . D u r i n g t h e i r s e cond v i s i t s u b j e c t s i n b o t h e x p e r i m e n t a l c o n d i t i o n s c o m p l e t e d i d e n t i c a l e x p e r i m e n t a l p r o t o c o l s . The f o r m a t o f t h e second s e s s i o n was i d e n t i c a l t o t h a t a d m i n i s t e r e d t o s u b j e c t s i n C o n d i t i o n 1, v i s i t 1. The s e s s i o n began w i t h an a d a p t a t i o n p e r i o d w h i c h was f o l l o w e d by p r e - t a s k i n s t r u c t i o n and b a s e l i n e p e r i o d s . E v e r y s u b j e c t t h e n c o m p l e t e d a s e r i e s o f t h r e e , 3 -m i nu t e s t r e s s t a s k s . E a ch s t r e s s t a s k was f o l l o w e d by a 3 -m inu t e r e c o v e r y p e r i o d . A l l o f t h e s e cond v i s i t s e s s i o n s were c o m p l e t e d w i t h i n 26 -31 d ay s o f t h e i n i t i a l s e s s i o n . D e b r i e f i n g . F o l l o w i n g t h e c o m p l e t i o n o f t h e i r s e cond e x p e r i m e n t a l s e s s i o n a l l s u b j e c t s were p r o v i d e d w i t h a b r i e f e x p l a n a t i o n o f t h e i r r e s t i n g and s t r e s s r e s p o n s e s . H e a r t r a t e and b l o o d p r e s s u r e r e a d i n g s were compared t o norms f o r women aged 18-64 y e a r s . These d a t a a r e p r e s e n t e d i n T a b l e 4 . - 54 -TABLE 4 Blood Pressure Norms for Women aged 18 - 64 Years* SYSTOLIC** Age Mean Standard error of mean 18-24 yrs. 110.9 0.64 25-34 yrs. 112.2 0.67 35-44 yrs. 119.4 0.85 45-54 yrs . 128.6 0.96 55-64 yrs. 137.4 1.03 DIASTOLIC L8-24 YRS. 070.0 0.45 25-34 YRS. 072.5 0.56 35-44 YRS 077.1 0.59 45-54 YRS. 080.9 0.73 55-64 YRS. - 081.7 0.58 *Data are drawn U.S. Government Survey 1976-1980. **Blood pressure i s expressed in mm Hg. A l l measurements are based on the average of 3 measurements. - 55 -S u b j e c t s were a l s o a d v i s e d t o engage i n r e g u l a r p r e v e n t i v e b l o o d p r e s s u r e c h e c k - u p s . E x p e r i m e n t a l D e s i g n and S t a t i s t i c a l A n a l y s e s The e x p e r i m e n t a l d e s i g n was a m i xed -mode l f a c t o r i a l d e s i g n . The d e s i g n i s p r e s e n t e d i n T a b l e 3 . Between g roup f a c t o r s were c o n d i t i o n s ( 1 : r e p e a t e d e x p o s u r e v e r s u s 2: s i n g l e e x p o s u r e ) and c a r d i o v a s c u l a r r e a c t i v i t y ( l o w v e r s u s h i g h ) . W i t h i n - s u b j e c t r e p e a t e d measu res were v i s i t s ( 2 ) by t r i a l s ( 3 ) by m i n u t e s ( 3 ) . S e v e r a l s t a t i s t i c a l p a ckages were u sed i n t h e a n a l y s i s o f t h e d a t a . These i n c l u d e d t h e S t a t i s t i c a l Package f o r t h e S o c i a l S c i e n c e s ( N i e , H u l l , J e n k i n s , S t e i n b r e n n e r , & B e n t , 1970) and t h e B i o m e d i c a l Da t a P rog ram ( D i x o n , 1 9 8 1 ) . R e s u l t s I n o r d e r t o t e s t t h e e x p e r i m e n t a l h y p o t h e s e s a s e r i e s o f d e s c r i p t i v e and i n f e r e n t i a l t e s t s were p e r f o r m e d . These i n c l u d e d d e s c r i p t i v e a n a l y s e s o f c a r d i o v a s c u l a r b a s e l i n e , r e a c t i v i t y and s t r e s s r e s p o n s e mea su r e s , d e s c r i p t i v e a n a l y s e s o f s e l f - r e p o r t dependen t m e a s u r e s , d e s c r i p t i v e a n a l y s e s o f h i g h v e r s u s l ow r e a c t i v i t y g r o u p s , a n a l y s e s o f c o v a r i a n c e , and p o s t - h o c t e s t s . The r e s u l t s o f ea ch o f t h e s e t e s t s i s r e v i e w e d i n t h e f o l l o w i n g s e c t i o n s . D e s c r i p t i v e C h a r c t e r i s t i c s o f C a r d i o v a s c u l a r Dependent Measu re s F ou r c a r d i o v a s c u l a r dependen t measu res were a n a l y z e d i n t h e p r e s e n t s t u d y . These i n c l u d e d h e a r t r a t e , s y s t o l i c b l o o d p r e s s u r e , d i a s t o l i c b l o o d p r e s s u r e , and mean a r t e r i a l p r e s s u r e r e s p o n s e m e a s u r e s . The mean and s t a n d a r d d e v i a t i o n f o r ea ch c a r d i o v a s c u l a r dependen t measure d u r i n g b a s e l i n e , s t r e s s t a s k , and p o s t - s t r e s s r e c o v e r y p e r i o d s were compu ted . B a s e l i n e v a l u e s r e p r e s e n t t h e a v e r a g e o f r e s p o n s e s d u r i n g m i n u t e s 19 and 20 o f t h e a d a p t a t i o n - 5 6 " period. Stress response and recovery values represent the average of minutes 1, 2, and 3 of each respective period. These values for each of the two experimental conditions during each of the two laboratory sessions are displayed i n Table 5. Data from the repeated stressor condition are also displayed i n Figures 1, 4, 7 and 10. Subjects displayed increases of +14 beats per minute i n heart rate and +16 mm Hg, +14 mm Hg, +15 mm Hg for s y s t o l i c , d i a s t o l i c , and mean a r t e r i a l pressure, r e s p e c t i v e l y from the pos t - i n s t r u c t i o n baseline period to the i n i t i a l s tress task during the f i r s t experimental session. During the second v i s i t s y s t o l i c , d i a s t o l i c and mean a r t e r i a l pressure readings increased +10 mm Hg, +10 mm Hg and +11 mm Hg, re s p e c t i v e l y . Heart rate increased 15 beats per minute i n response to the f i r s t stressor during the second v i s i t . , Descriptive C h a r a c t e r i s t i c s of Self-Report Dependent Measures Five s e l f - r e p o r t dependent measures were analyzed through responses to the f i v e scales included i n the Stress Perception Questionnaire. This questionnaire i s contained i n Appendix 3. The s e l f - r e p o r t measures included perceived task s t r e s s f u l n e s s , task d i f f i c u l t y , task importance, task performance, and perceived influence of mood on task performance. The mean and standard deviation for each s e l f - r e p o r t measure are presented i n Table 6. Responses to measures of perceived s t r e s s f u l n e s s , d i f f i c u l t y , and importance ranged from 5.9 to 7.0 on a 10-point L i k e r t scale, i . e . , 0 = not s t r e s s f u l , 10 = very s t r e s s f u l . These r e s u l t s confirm the subjective v a l i d i t y of the mental arithmetic task as a v a l i d experimental s t r e s s o r . Descriptive C h a r a c t e r i s t i c s of Cardiovascular R e a c t i v i t y Groups R e a c t i v i t y groups were formed on the basis of cardiovascular change scores. In the present study, change was defined as the average response during minutes 1, 2 and 3 of the i n i t i a l s t r e s s task period i n V i s i t 1 minus J 57 -TABLE 5 Means, and S t a n d a r d D e v i a t i o n s o f C a r d i o v a s c u l a r Response Measu res V i s i t 1 HR SBP DBP MAP B a s e l i n e Task 1 R e c o v e r y 1 Task 2 R e c o v e r y 2 Task 3 R e c o v e r y 3 7 2 . 6 ( 1 0 . 0 ) 9 6 . 0 ( 1 3 . 5 ) 7 2 . 3 ( 1 0 . 3 ) 8 4 . 9 ( 1 2 . 2 ) 7 0 . 6 ( 1 0 . 0 ) 8 1 . 5 ( 1 3 . 3 ) 7 0 . 6 ( 9 . 3 ) 1 0 8 . 6 ( 1 1 . 5 ) 1 2 4 . 3 ( 1 3 . 0 ) 1 1 2 . 3 ( 1 2 . 0 ) 1 2 3 . 7 ( 1 0 . 4 ) 1 0 9 . 0 ( 1 0 . 3 ) 1 1 7 . 3 ( 1 0 . 2 ) 1 0 8 . 0 ( 1 0 . 7 ) 6 1 . 1 ( 8 . 2 ) 7 5 . 3 ( 1 0 . 7 ) 6 2 . 3 ( 8 . 7 ) 6 8 . 2 ( 8 . 4 ) 6 2 . 0 ( 8 . 7 ) 6 6 . 6 ( 8 . 2 ) 5 9 . 9 ( 8 . 3 ) 7 9 . 1 ( 1 0 . 5 ) 9 4 . 0 ( 1 0 . 8 ) 8 0 . 7 ( 9 . 5 ) 8 7 . 9 ( 1 0 . 0 ) 7 8 . 0 ( 7 . 8 ) 8 6 . 1 ( 9 . 7 ) 7 7 . 7 ( 7 . 9 ) V i s i t 2 B a s e l i n e Task 1 Re c ove r y Task 2 R e c o v e r y Task 3 R e c o v e r y 1 2 3 7 2 . 1 ( 9 . 3 ) 8 7 . 0 ( 1 2 . 9 ) 7 1 . 6 ( 1 0 . 0 ) 8 3 . 8 ( 1 2 . 2 ) 7 0 . 6 ( 9 . 3 ) 8 1 . 4 ( 1 1 . 7 ) 7 1 . 6 ( 9 . 0 ) 1 0 6 . 3 ( 8 . 9 ) 1 1 6 . 7 ( 1 1 . 9 ) 1 0 8 . 3 ( 8 . 2 ) 1 1 4 . 0 ( 9 . 6 ) 1 0 6 . 7 ( 8 . 6 ) 1 1 1 . 8 ( 9 . 9 ) 1 0 8 . 3 ( 8 . 2 ) 6 0 . 0 ( 6 . 2 ) 6 9 . 7 ( 8 . 3 ) 6 1 . 6 ( 6 . 6 ) 6 5 . 8 ( 7 . 9 ) 5 9 . 9 ( 7 . 3 ) 6 4 . 4 ( 7 . 1 ) 5 9 . 2 ( 7 . 0 ) 7 6 . 5 ( 6 . 8 ) 8 7 . 6 ( 9 . 3 ) 7 8 . 5 ( 7 . 2 ) 8 4 . 2 ( 9 . 1 ) 7 7 . 6 ( 7 . 9 ) 8 3 . 6 ( 8 . 9 ) 7 6 . 6 ( 7 . 8 ) N o t e : The v a l u e s f o r t h e s e cond and t h i r d s t r e s s t a s k s and r e c o v e r y p e r i o d s d u r i n g V i s i t 1 a r e based on r e s p o n s e s o f s u b j e c t s i n C o n d i t i o n 1 o n l y . A l l v a l u e s r e p r e s e n t t h e a v e r a g e r e s p o n s e s o f a l l s u b j e c t s i n b o t h c o n d i t i o n s 1 and 2 . FIGURE 1 CONDITION I: REPEATED EXPOSURE HEART RATE DATA Legend i »HGHs»siaxtTAaag/vi 3 -Ht^ SYSTOCRE>CICR^V2 4 'UJWaSICUCRDCIORS^Q 1 ST1 RC1 ST2 RC2 ST* RC3 1 "ST1 RCf ST2 Rt2 ST3 RC3 oo FIGURE 4 CONDITION l:REPEATED EXPOSURE SYSTOUC BLOOD PRESSURE DATA 150-1 uoH VISIT I VISIT II jr. E E c 130 H 110 H CO 120-1 0 UJ 0£ 0_ Q O s CD O o 100 H 1 0 >-oo Legend j_ 'UGHHRREACTTJRSyVl 2 •LCWHRREACTCRSArl 3 °HGH HR REAGTORyV2 4 •L0WHRF€ACTTJR^V2 4 WK. INTERVAL 90H 80- 1 1 1 ST1 RC1 ST2 RC2 ST3 RC3 ST1 RC1 ST2 RC2 ST3 RC3 FIGURE 7 CONDITION I DIASTOUC BLOOD PRESSURE DATA 85-| 55 H 50 4 WK. INTERVAL 1 1 1 1 1 1 1 r ST1 RC1 ST2 RC2 ST3 RC3 ST1 RC2 ST2 RC2 ST3 RC3 FIGURE 10 TABLE 6 Means and S t a n d a r d D e v i a t i o n s o f S e l f - R e p o r t Measu re s Measure Mean S . D . P e r c e i v e d P e r f o r m a n c e 1 4 . 04 1.75 P e r c e i v e d P e r f o r m a n c e 2 5 .02 1.54 P e r c e i v e d S t r e s s 1 6 .12 2 .22 P e r c e i v e d S t r e s s 2 5 .90 2 .05 P e r c e i v e d D i f f i c u l t y 1 6 .97 2 .11 P e r c e i v e d D i f f i c u l t y 2 6 .38 1.97 P e r c e i v e d Impo r t a n c e 1 6 .57 2 .08 P e r c e i v e d Impo r t an ce 2 6 .69 1.98 I n f l u e n c e o f Mood 1 5 .59 2 .19 I n f l u e n c e o f Mood 2 5.37 2 .50 *A11 s e l f - r e p o r t r a t i n g s were done on a 1 0 - p o i n t L i k e r t S c a l e . - 63 -t h e a v e r a g e o f m i n u t e s 19 and 20 o f t h e a d a p t a t i o n p e r i o d . The p r e s e n t d e f i n i t i o n o f change was based on p r e v i o u s o b s e r v a t i o n s t h a t b o t h b l o o d p r e s s u r e and h e a r t r a t e unde rgo s i g n i f i c a n t changes f r om t h e end o f t h e a d a p t a t i o n t o t h e p o s t - i n s t r u c t i o n , p r e - t a s k w a i t i n g p e r i o d ( L i n d e n , M c E a c h e r n , & F r a n k i s h , i n p r e s s ) . R e a c t i v i t y s c o r e s were computed f o r h e a r t r a t e and s y s t o l i c dependent m e a s u r e s . D e s c r i p t i v e s t a t i s t i c s f o r t h e d i s t r i b u t i o n o f h e a r t r a t e r e a c t i v i t y s c o r e s a r e p r e s e n t e d i n T a b l e 7 . H i g h and l ow r e a c t i v i t y g r oup s were composed o f t h o s e s u b j e c t s whose change s c o r e s p l a c e d them i n t h e uppe r and l o w e r t e r c i l e s o f t h e d i s t r i b u t i o n o f h e a r t r a t e change s c o r e s . The c u t - o f f p o i n t s f o r t h e h i g h and l ow r e a c t i v i t y g r oup s were >+27 b e a t s pe r m i n u t e ( h i g h ) , and <+15 b e a t s pe r m i n u t e ( l o w ) . These h e a r t r a t e c u t - o f f s c o r e s a r e s i m i l a r t o t h o s e f ound i n p r e v i o u s r e s e a r c h on a s i m i l a r p o p u l a t i o n ( L i n d e n , 1984; L i n d e n e t a l . , i n p r e s s ) . H e a r t r a t e r e a c t i v i t y was s u b s e q u e n t l y emp loyed as a be tween -g roup c l a s s i f i c a t i o n v a r i a b l e i n a n a l y s e s o f c o v a r i a n c e o f b l o o d p r e s s u r e r e s p o n s e s . G roups were f o rmed i n t h i s manner t o a v o i d t h e c o n f o u n d i n g e f f e c t s p r o du c ed by s i m u l t a n e o u s l y u s i n g a g i v e n c a r d i o v a s c u l a r measu re , f o r examp le h e a r t r a t e , a s b o t h a c l a s s i f i c a t i o n v a r i a b l e and a dependen t v a r i a b l e . I n o rde r - t o a n a l y z e t h e s t a b i l i t y and c h a r a c t e r i s t i c s o f t h e d i s t r i b u t i o n o f h e a r t r a t e r e a c t i v i t y a c r o s s t h e two e x p e r i m e n t a l s e s s i o n s , h e a r t r a t e r e a c t i v i t y t o t h e f i r s t t a s k i n t h e second s e s s i o n was c a l c u l a t e d . H e a r t r a t e r e a c t i v i t y i n V i s i t 1 was t h e n compared t o t h a t f r om V i s i t 2 ( s e e T a b l e 8 ) . The mean h e a r t r a t e r e a c t i v i t y i n V i s i t 2 was 8 . 5 b e a t s l o w e r t h a n v i s i t 1 . I n a d d i t i o n t h e r a n g e , s t a n d a r d d e v i a t i o n , and p e r c e n t a g e o f h e a r t r e a c t o r s were r e d u c e d i n t h e s e cond s e s s i o n . I n V i s i t 2 t h e d i s t r i b u t i o n o f h e a r t r a t e r e a c t i v i t y was more l e p t o k u r t i c and more p o s i t i v e l y skewed t h a n i n V i s i t 1 . - 6 4 -TABLE 7 Frequency Distribution of Cardiovascular Reactivity Scores Mean Mode Median Minimum Maximum Range Variance Standard Deviation Heart Rate Reactivity** 22.44 14.17 21.58 -3.33 66.67 70.0 209.68 14.48 Systolic Blood Pressure React ivi ty* * *  14.52 21.16 13.33 -2.17 41.67 43.8 71.37 8.45 High reactivity cut-off > +27 bpm Low reactivity cut-off < +15 bpm High reactors N_ = 33 Low reactors N = 30 > +18 mm Hg < +11 mm Hg N = 30 N = 33 *Reactivity was defined as the average f i r s t task response level minus minutes 19 and 20 of the adaptation period. **Heart rate measures are expressed in beats per minute. * * *Blood pressure measures are expressed in mm Hg. A l l values represent the average of responses in both Conditions 1 and 2. - 65 -TABLE 8 Compa r i s on o f H e a r t Ra t e and S y s t o l i c P r e s s u r e  R e a c t i v i t y A c r o s s E x p e r i m e n t a l S e s s i o n s H e a r t Ra t e R e a c t i v i t y V i s i t 1 V i s i t 2 Mean 22 . 44 1 3 . 9 1 S . D . 1 4 . 4 8 , 9 . 9 0 Minimum - 3 . 3 3 - 4 . 6 7 Maximum 6 6 . 6 7 5 5 . 8 3 Range 70 6 0 . 5 % > +2 S . D . 5% 0% % > +1 S . D . 13% 6% Skewness .681 1.11 K u r t o s i s .567 2 .66 % Low R e a c t o r s 36% 61% % H i g h R e a c t o r s 36% 9% S y s t o l i c R e a c t i v i t y Mean 1 4 . 5 2 1 0 . 5 6 S . D . 8 . 45 6 . 83 Minimum - 2 . 1 7 - 6 . 6 7 Maximum 4 1 . 6 7 29 .67 Range 4 3 . 8 3 6 . 3 % > + 2 S . D . 2% 0% % > + 1 S . D . 13% 4% Skewness . 561 .240 K u r t o s i s .605 .517 % Low R e a c t o r s 34% 61% % H i g h R e a c t o r s 31% 13% H e a r t r a t e i s e x p r e s s e d i n b e a t s pe r m i n u t e . SBP i s e x p r e s s e d i n mm H g . - 66 -D e s c r i p t i v e s t a t i s t i c s f o r t h e d i s t r i b u t i o n o f s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y s c o r e s a r e p r e s e n t e d i n T a b l e 7 . The c u t - o f f p o i n t s f o r t h e h i g h and low s y s t o l i c r e a c t i v i t y g r oup s were >+18 nun Hg ( h i g h ) , and < + l l mm Hg ( l o w ) . S y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y was u sed as a be tween -g roup c l a s s i f i c a t i o n v a r i a b l e i n t h e a n a l y s e s o f c o v a r i a n c e o f h e a r t r a t e r e s p o n s e s . A c o m p a r i s o n o f s y s t o l i c r e a c t i v i t y a c r o s s t h e two e x p e r i m e n t a l s e s s i o n s r e v e a l e d a mean d e c r e a s e o f 4 . 1 mm Hg i n V i s i t 2 . The r a n g e , s t a n d a r d d e v i a t i o n , and p e r c e n t a g e o f h i g h r e a c t o r s were a l l r e d u c e d i n t h e s e cond s e s s i o n . The p e r c e n t a g e o f l ow s y s t o l i c r e a c t o r s changed f r om 34% i n V i s i t 1 t o 61% i n V i s i t 2 . The skewness and k u r t o s i s o f t h e d i s t r i b u t i o n o f s y s t o l i c r e a c t i v i t y d i d n o t change a c r o s s s e s s i o n s . A e r o s s - t a b u l a t i o n a n a l y s i s o f h e a r t r a t e r e a c t i v i t y and s y s t o l i c r e a c t i v i t y a c r o s s t h e two e x p e r i m e n t a l c o n d i t i o n s was c o n d u c t e d . The r e s u l t s r e v e a l e d no s i g n i f i c a n t d i f f e r e n c e s i n t h e number o f h i g h and l ow r e a c t o r s a s s i g n e d t o e a ch o f t h e two c o n d i t i o n s . A s ub s equen t c r o s s - t a b u l a t i o n o f a l l s u b j e c t s on t h e b a s i s o f b o t h s y s t o l i c and h e a r t r a t e r e a c t i v i t y s c o r e s r e v e a l e d t h a t 100% o f t h o s e women i d e n t i f i e d as h i g h s y s t o l i c r e a c t o r s were a l s o h i g h h e a r t r a t e r e a c t o r s ; w h i l e 91% o f t h e l ow h e a r t r a t e r e a c t o r s f e l l i n t o t h e c a t e g o r y o f l ow s y s t o l i c r e a c t i v i t y ( s e e T a b l e 9 ) . F i n a l l y , a c r o s s - t a b u l a t i o n a n a l y s i s o f r e a c t i v i t y a c r o s s m e n s t r u a t i n g v e r s u s n o n - m e n s t r u a t i n g , and s u b j e c t s t a k i n g b i r t h c o n t r o l p i l l s v e r s u s no b i r t h c o n t r o l p i l l s was p e r f o r m e d . These d a t a a r e p r e s e n t e d i n T a b l e 1 0 . The r e s u l t s i n d i c a t e t h a t d u r i n g t h e s e cond e x p e r i m e n t a l s e s s i o n a m a j o r i t y o f low s y s t o l i c and l ow h e a r t r a t e r e a c t o r s c o u l d be d e s c r i b e d as n o n - m e n s t r u a t i n g , n o t on b i r t h c o n t r o l s u b j e c t s . These r e s u l t s s u g g e s t t h a t b o t h b i r t h c o n t r o l p i l l s and m e n s t r u a t i o n need t o be i n v e s t i g a t e d as p o t e n t i a l m e d i a t o r s o f c a r d i o v a s c u l a r r e s p o n s e s t o p s y c h o l o g i c a l s t r e s s . However a f o l l o w - u p - 67 -TABLE 9 C l a s s i f i c a t i o n o f S u b j e c t s by H e a r t Ra t e v e r s u s  S y s t o l i c B l o o d P r e s s u r e R e a c t i v i t y H i g h S y s t o l i c R e a c t o r s (N = 31) H i g h H e a r t Ra t e R e a c t o r s (N = 30) Low H e a r t Ra t e R e a c t o r s (N = 0 ) Low S y s t o l i c R e a c t o r s (N = 34) H i g h H e a r t Ra t e R e a c t o r s (|[ = 3) Low H e a r t Ra t e R e a c t o r s (N = 30) ^ R e a c t i v i t y s c o r e s were c a l c u l a t e d as t h e a v e r a g e o f t h e f i r s t t a s k s t r e s s r e s p o n s e m inus t h e a v e r a g e o f m i n u t e s 19 and 20 o f t h e p r e - s t r e s s a d a p t a t i o n p e r i o d d u r i n g t h e f i r s t e x p e r i m e n t a l s e s s i o n . - 68 -TABLE 10 C r o s s - T a b u l a t i o n o f S u b j e c t s by B i r t h C o n t r o l ,  M e n s t r u a t i o n and R e a c t i v i t y V a r i a b l e s B i r t h C o n t r o l M e n s t r u a t i o n V i s i t 1 V i s i t 2 S y s t o l i c R e a c t i v i t y S y s t o l i c R e a c t i v i t y H i g h Low H i g h Low Yes 6 7 0 15 No 23 22 12 37 Yes 7 4 3 6 No 22 25 9 46 B i r t h C o n t r o l M e n s t r u a t i o n V i s i t 1 V i s i t 2 H e a r t Ra t e R e a c t i v i t y H e a r t Ra t e R e a c t i v i t y H i g h Low H i g h Low Yes 12 6 2 8 No 23 24 7 44 Yes 10 3 3 7 No 25 27 6 45 - 69 -analysis of covariance with age and baseline as covariates, and b i r t h control (yes or no) and menstruating (yes or no) as between group factors revealed no s i g n i f i c a n t between-group differences on any of the cardiovascular dependent measures. In addition, tetrachoric correlations between b i r t h control, menstruation, and cardiovascular r e a c t i v i t y were not s i g n i f i c a n t when Bonferroni-corrected to reduce the li k e l i h o o d of alpha errors. Correlational Analyses Three sets of co r r e l a t i o n a l analyses were conducted. F i r s t , the intercorrelations between subject age, baseline, f i r s t task stress response, and r e a c t i v i t y measures were computed for each of the four dependent measures. Second, intercorrelations of the self-report measures were computed. F i n a l l y , the inte r c o r r e l a t i o n between each of the self-report and cardiovascular baseline, f i r s t task stress response, f i n a l task stress response, and r e a c t i v i t y measures was assessed. In order to reduce the li k e l i h o o d of alpha errors the significance c r i t e r i o n for each correlation matrix was set at _p_ < .001 through the use of a Bonferroni procedure (Larzelere & Mulaik, 1977). The intercorrelations between cardiovascular dependent measures were calculated i n two stages. F i r s t , correlations between each of the four dependent variables on baseline, f i r s t stress task, and r e a c t i v i t y measures were calculated independently for each of the two experimental sessions. Second, the intercorrelations between baseline, stress response, and r e a c t i v i t y measures across the two sessions were computed. These correlations are presented i n Table 11. The intercorrelations between cardiovascular measures and age of subject are presented i n Table 12. Subject age was found to be s i g n i f i c a n t l y correlated < .001) with baseline measures of blood pressure taken during -70-TABLE 11 I n t e r c o r r e l a t i o n s o f C a r d i o v a s c u l a r Dependent Measu re s W i t h i n S e s s i o n 1* W i t h i n S e s s i o n 2 B a s e l i n e 1 HR SBP MAP DBP B a s e l i n e 2 HR SBP DBP MAP HR HR .7223 .6283 .6467 SBP — . 8935 — SBP — — / . 6283 .7657 MAP .8935 — — DBP — — — — DBP MAP — — — — S t r e s s Response 1 S t r e s s Response 2 HR .3847 .3768 HR SBP — .8709 — SBP — .7508 .8358 MAP DBP — — — — DBP .6899 .8131 — MAP — — — .8553 R e a c t i v i t y 1 R e a c t i v i t y 2 HR — .7056 .5408 .6426 HR .3556 .3095 SBP — — . 5355 .6580 SBP — — .5055 .5982 MAP — — — — DBP — — — — DBP — — — .7216 MAP — — — .6648 A c r o s s E x p e r i m e n t a l S e s s i o n s HR SBP DBP MAP B a s e l i n e .6117 .6222 .6801 • 5595 Task Response L e v e l .6869 .7623 .6679 • 6860 R e a c t i v i t y * * * .6649 .3175 . 1290** 2271** * 0 n l y s i g n i f i c a n t w i t h i n - s e s s i o n c o r r e l a t i o n s a r e d i s p l a y e d . **These between s e s s i o n c o r r e l a t i o n s were n o n s i g n i f i c a n t and a r e i n c l u d e d f o r p u r p o s e s o f c l a r i t y o n l y . * * * R e a c t i v i t y was d e f i n e d as change f r om t he l a s t two m i n u t e s o f t h e a d a p t a t i o n p e r i o d t o a v e r a g e f i r s t t a s k r e s p o n s e l e v e l s . - 71 -TABLE 12 Correlations of Subject Age with Baseline and Stress Response Measures Visit 1 Baseline 1 Stress Response 1 Recovery 1 Stress Response 2 Recovery 2 Stress Response 3 Recovery 3 Visit 2 Baseline 2 Stress Response 4 Recovery 4 Stress Response 5 Recovery 5 Stress Response 6 Recovery 6 Repeated Stressor SBP* DBP** MAP*** .4979 .5896 .4460 .5055 .4515 .4932 .5814 .4595 .4856 .4678 .5072 SBP DBP MAP .6158 .6115 .5851 .4505 .4593 .4426 .5647 .6085 .4919 .4341 .6018 .5118 .4937 .5413 .4265 .4011 .5623 .4491 .5667 .6602 .5524 .5088 .4504 .4279 .4441 .4814 *Systolic Blood Pressure **Diastolic Blood Pressure ***Mean Arterial Pressure - l i -the, f i r s t e x p e r i m e n t a l s e s s i o n . The a v e r a g e magn i t ude o f t h e s e c o r r e l a t i o n s (r_ = . 60 ) i n d i c a t e d t h a t t h e s u b j e c t ' s age a c c o u n t e d f o r a p p r o x i m a t e l y 35% o f t h e v a r i a n c e i n b a s e l i n e b l o o d p r e s s u r e l e v e l s . Age was a l s o s i g n i f i c a n t l y c o r r e l a t e d w i t h s y s t o l i c b a s e l i n e d u r i n g t h e s e cond s e s s i o n ( r = . 5 0 , ]3 < . 0 0 1 ) . S y s t o l i c , d i a s t o l i c and mean a r t e r i a l p r e s s u r e and s t r e s s r e s p o n s e and r e c o v e r y p e r i o d v a l u e s d u r i n g V i s i t 2 were s i g n i f i c a n t l y c o r r e l a t e d w i t h s u b j e c t s ' age (r_ = .40 t o . 6 6 ) . D u r i n g V i s i t 2 d i a s t o l i c p r e s s u r e r e c o v e r y v a l u e s were s i g n i f i c a n t l y c o r r e l a t e d w i t h age f o r s u b j e c t s i n t h e r e p e a t e d s t r e s s o r c o n d i t i o n . S u b j e c t s i n t h e p r e s e n t s t u d y r e p o r t e d a mean p e r c e i v e d f i t n e s s l e v e l o f 6 . 4 5 / 1 0 , and a mean r e p o r t e d l e v e l o f p h y s i c a l a c t i v i t y o f 7 . 1 / 1 0 . B o t h l e v e l o f p h y s i c a l a c t i v i t y and p e r c e i v e d f i t n e s s were s i g n i f i c a n t l y c o r r e l a t e d w i t h h e a r t r a t e d u r i n g s t r e s s t a s k and r e c o v e r y p e r i o d s . These c o r r e l a t i o n s a r e p r e s e n t e d i n T a b l e 1 3 . B l o o d p r e s s u r e measu res were n o t s i g n i f i c a n t l y c o r r e l a t e d w i t h e i t h e r o f t h e two f i t n e s s m e a s u r e s . B o t h f i t n e s s measures were r e l i a b l e a c r o s s v i s i t s ( p e r c e i v e d f i t n e s s : r_ = . 7 7 ; a c t i v i t y l e v e l : r_ = . 71 ) and showed good c o n v e r g e n t v a l i d i t y ( r = . 5 6 ) . W i t h i n S e s s i o n s C a r d i o v a s c u l a r C o r r e l a t i o n s D u r i n g a g i v e n e x p e r i m e n t a l s e s s i o n s y s t o l i c , d i a s t o l i c , and mean a r t e r i a l p r e s s u r e b a s e l i n e measures were s i g n i f i c a n t l y c o r r e l a t e d . C a r d i o v a s c u l a r r e s p o n s e measu res d i s p l a y e d i n t e r c o r r e l a t i o n s o f .76 t o .90 d u r i n g t h e p r e - t a s k b a s e l i n e p e r i o d d u r i n g V i s i t 1 . D u r i n g t h e s e cond v i s i t t h e s e c o r r e l a t i o n s r anged f r om .63 t o . 7 7 . H e a r t r a t e b a s e l i n e was s i g n i f i c a n t l y c o r r e l a t e d w i t h b a s e l i n e b l o o d p r e s s u r e measu res d u r i n g t h e s e cond l a b o r a t o r y v i s i t . A ve r age b l o o d p r e s s u r e l e v e l s d u r i n g t h e f i r s t s t r e s s t a s k i n a g i v e n v i s i t were a l s o s i g n i f i c a n t l y c o r r e l a t e d . H e a r t r a t e d u r i n g t h e f i r s t s t r e s s t a s k was s i g n i f i c a n t l y c o r r e l a t e d w i t h mean a r t e r i a l and s y s t o l i c p r e s s u r e - 73 -TABLE 13 Correlations of Self-Reported Fitness Level and Frequency of Physical  Act ivi ty with Stress Response and Recovery Period Heart Rate* Perceived Fitness V i s i t 1 V i s i t 2 HR Measure *r r Stressor 1 n.s. -.2850 Recovery 1 -.4562 -.4381 Stressor 2 -.3656 -.3047 Recovery 2 -.4329 -.4032 Stressor 3 -.3973 -.3047 Recovery 3 -.4932 -.4037 Physical Act ivi ty Level V i s i t 1 V i s i t 2 Stressor 1 n.s. -.3043 Recovery 1 -.3935 -.4235 Stressor 2 -.3272 -.3109 Recovery 2 -.3748 -.4035 Stressor 3 -.3748 -.3109 Recovery 3 -.4589 -.4450 *Unless otherwise indicated a l l correlations are significant at JD < .002. - 74 -l e v e l s d u r i n g t h e 1 s t l a b o r a t o r y s e s s i o n (r_ = . 3 8 ) . S y s t o l i c , d i a s t o l i c and mean a r t e r i a l p r e s s u r e d u r i n g t h e f i r s t t a s k p e r i o d were s i g n i f i c a n t l y c o r r e l a t e d i n b o t h V i s i t s 1 and 2 (_r = .68 t o . 8 7 ) . A l l measures o f c a r d i o v a s c u l a r r e a c t i v i t y t a k e n i n t h e f i r s t v i s i t were s i g n i f i c a n t l y r e l a t e d . D u r i n g t he s e cond s e s s i o n f o u r weeks l a t e r , measu res o f b l o o d p r e s s u r e r e a c t i v i t y were s i g n i f i c a n t l y c o r r e l a t e d w h i l e h e a r t r a t e r e a c t i v i t y was c o r r e l a t e d w i t h s y s t o l i c and mean a r t e r i a l m e a s u r e s . The c o r r e l a t i o n between h e a r t r a t e r e a c t i v i t y and s y s t o l i c r e a c t i v i t y (r_ = .71 d u r i n g V i s i t 1 and r_ = .36 d u r i n g V i s i t 2 ) r e f l e c t s t h e i n f l u e n c e o f a common s y m p a t h e t i c a l l y - m e d i a t e d n e u r o g e n i c c o n t r o l mechan i sm. The c o r r e l a t i o n be tween d i a s t o l i c and h e a r t r a t e r e a c t i v i t y a r g u e s a g a i n s t t h e e x i s t e n c e o f i n d e p e n d e n t mechan isms o f c o n t r o l f o r t h e s e two r e s p o n s e d i m e n s i o n s . A c r o s s S e s s i o n C a r d i o v a s c u l a r C o r r e l a t i o n s I n o r d e r t o t e s t t h e r e l i a b i l i t y and s t a b i l i t y o f b a s e l i n e , s t r e s s r e s p o n s e and r e a c t i v i t y measu res t h e c o r r e l a t i o n between 1 s t and 2nd v i s i t measu res t a k e n o v e r a f o u r - w e e k i n t e r v a l was a s s e s s e d . These d a t a a r e p r e s e n t e d i n T a b l e 1 1 . F i r s t s e s s i o n b a s e l i n e and 1 s t t a s k s t r e s s r e s p o n s e measu res were s i g n i f i c a n t l y c o r r e l a t e d w i t h t h o s e t a k e n i n t h e s e cond e x p e r i m e n t a l s e s s i o n . C o r r e l a t i o n s r a n g e d f r om .5595 t o .7623 (ja < . 0 0 1 ) . These r e s u l t s s u g g e s t t h a t 1 s t v i s i t measu res e x p l a i n 30% - 60% o f t h e v a r i a n c e i n se cond v i s i t b a s e l i n e and s t r e s s r e s p o n s e m e a s u r e s . Measu re s o f h e a r t r a t e r e a c t i v i t y (r^ = . 67 ) and s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y ( r = . 32 ) t a k e n d u r i n g e a ch o f t h e two s e s s i o n s were a l s o h i g h l y c o r r e l a t e d . F i r s t s e s s i o n r e a c t i v i t y a c c o u n t e d f o r 45% and 10% o f t h e v a r i a n c e i n s e cond s e s s i o n h e a r t r a t e and s y s t o l i c r e a c t i v i t y , r e s p e c t i v e l y . H e a r t r a t e a p p e a r s t o be a more r e l i a b l e measure o f c a r d i o v a s c u l a r r e a c t i v i t y . Measu re s o f d i a s t o l i c and mean a r t e r i a l p r e s s u r e r e a c t i v i t y were no t s i g n i f i c a n t l y c o r r e l a t e d a c r o s s t h e _ 75 _ two v i s i t s . I n t e r c o r r e l a t i o n s of Self-Report Measures I n t e r c o r r e l a t i o n s between the s e l f - r e p o r t dependent measures were f i r s t c a l c u l a t e d on a w i t h i n - s e s s i o n b a s i s . These data are d i s p l a y e d i n Table 14. Only those c o r r e l a t i o n s which are s i g n i f i c a n t at _p_ < .001 are d i s p l a y e d . During the f i r s t experimental s e s s i o n r a t i n g s of perceived s t r e s s explained approximately 19% of the variance i n r a t i n g s of perceived task d i f f i c u l t y ( r = .4318). Perceived performance was n e g a t i v e l y c o r r e l a t e d w i t h perceived task d i f f i c u l t y ( r = .3710). During the second v i s i t , r a t i n g s of perceived s t r e s s were p o s i t i v e l y c o r r e l a t e d w i t h perceived task d i f f i c u l t y and importance, and n e g a t i v e l y c o r r e l a t e d w i t h perceived task d i f f i c u l t y . Perceived performance measures were a l s o n e g a t i v e l y c o r r e l a t e d w i t h perceived task d i f f i c u l t y . In order to assess the t e s t - r e t e s t r e l i a b i l i t y of each of the s e l f - r e p o r t measures, the i n t e r c o r r e l a t i o n between 1st and 2nd v i s i t r a t i n g s on each measure was computed. These data are presented i n Table 14. Ratings of perceived task d i f f i c u l t y were not s i g n i f i c a n t l y c o r r e l a t e d across the two v i s i t s . F i r s t v i s i t r a t i n g s on the other four s e l f - r e p o r t measures accounted f o r 10% - 35% of the variance i n second v i s i t r a t i n g s ( r = .3169 to r = .5876), which i n d i c a t e s that only a modest proportion of response v a r i a b i l i t y can be a t t r i b u t e d to i n d i v i d u a l response stereotypy i n s u b j e c t i v e a p p r a i s a l . I n t e r c o r r e l a t i o n s of Cardiovascular and Self-Report Measures The c o r r e l a t i o n between each of the s e l f - r e p o r t measures and c a r d i o v a s c u l a r b a s e l i n e , f i r s t task response, and r e a c t i v i t y w i t h i n each of the two l a b o r a t o r y sessions were computed. Heart r a t e r e a c t i v i t y and r a t i n g s of perceived task importance acquired during the second s e s s i o n were s i g n i f i c a n t l y c o r r e l a t e d (r_ = .3105). C o r r e l a t i o n s between the s e l f - r e p o r t - 76 -TABLE 14 In t e r c o r r e l a t i o n s of Self-Report Dependent Measures Within V i s i t 1 PDl PPI PS1 .4318 PDl -.3710 Within V i s i t 2 PD2 PI2 PPI PS2 .4530 .4324 -.4217 PD2 -.4379 Across V i s i t s PS1 - PS2 .3449 PDl - PD2 .1182* PII - PI2 .4823 PPI - PP2 .5876 PIM1 - PIM2 .3169 *PS = Perceived Stress *PD = Perceived D i f f i c u l t y PI = Perceived Importance PP = Perceived Performance PIM = Perceived Influence of Mood on Performance *Nonsignificant c o r r e l a t i o n s , included for c l a r i t y . - 77 -measures and cardiovascular response levels during the f i n a l stress task in each session were not significant. Ratings of perceived performance were significantly correlated (_r = .280, JJ < .005) with each of the three heart rate recovery values in the second v i s i t . Analyses of Covariance Three sets of analysis of covariance were performed for each of the four cardiovascular dependent measures. Subject age and pre-task baseline were treated as covariates in each analysis. The three sets of analysis of covariance were labelled as Condition 1 ANCOVA, Task 1 ANCOVA, and Vi s i t 2 ANCOVA, respectively. The Condition 1 ANCOVA was based on data from subjects in the repeated stressor experimental condition. High and low reactivity was treated as a between-group factor, while v i s i t s (2), t r i a l s (3), and minutes (3) were treated as factorial within-subject repeated measures. The Condition 1 ANCOVAs allowed for analyses of the effects of repeated stress tasks for those 45 subjects exposed to a total of 2 x 3 t r i a l s . However, they did not include an analysis of the effects of varying amounts of stressor exposure on cardiovascular responses. In the Task 1 ANCOVA experimental conditions and reactivity were between-group factors. Visits (2) and minutes (3) were analyzed as repeated measures. The Task 1 ANCOVAs included an analysis of the effects of repeated versus single stress tasks across the high versus low reactivity groups. They did not however allow for analysis of across t r i a l s effects within a given session only. The Vi s i t 2 ANCOVA was performed on data gathered during the second experimental session. Conditions and reactivity were between-group variables, while t r i a l s (3) and minutes (3) were analyzed as factorial repeated measures. The V i s i t 2 ANCOVAs included analyses of both t r i a l s and minutes repeated measures following repeated versus single stressor - 78 -e x p o s u r e d u r i n g V i s i t 1. The V i s i t 2 ANCOVAs d i d n o t a l l o w f o r a n a l y s i s o f t h e e f f e c t s o f t h e f o u r -week i n t e r - v i s i t i n t e r v a l . I n o r d e r t o r e d u c e t h e l i k e l i h o o d o f Type I e r r o r i n t h e r e p e a t e d measures a n a l y s e s o f c o v a r i a n c e d e s c r i b e d b e l o w , an e p s i l o n - c o r r e c t i o n p r o c e d u r e was used t o a d j u s t t h e d eg r ee s o f f r eedom (Greenhouse & G e i s s e r , 1959; see a l s o Kese lman & Rogan , 1980; I a cono & L y k k e n , 1 9 8 4 ) . The F t e s t s , w h i c h i n v o l v e d r e p e a t e d measures a n d ' a r e p r e s e n t e d be l ow , i n c l u d e t he c o r r e c t e d p v a l u e and t h e v a l u e o f e p s i l o n a s s o c i a t e d w i t h t h e e r r o r t e r m . F o l l o w i n g each a n a l y s i s o f c o v a r i a n c e f o u r a d d i t i o n a l a n a l y s e s were c o n d u c t e d . F i r s t , a t r e n d a n a l y s i s o f s i g n i f i c a n t ANCOVA t e rms was p e r f o r m e d . S e c o n d , Newman-Keuls t e s t s were u sed t o make a l l p o s s i b l e p o s t hoc p a i r w i s e c o m p a r i s o n s between l e v e l s o f t h e t r i a l s and m i n u t e s ma in e f f e c t s . The Newman-Keuls t e s t s r e p o r t e d be low i n c l u d e t h e d eg r ee s o f f r e e d o m , p v a l u e , and r v a l u e a s s o c i a t e d w i t h each between l e v e l c o m p a r i s o n . I n ea ch c a s e t h e r v a l u e r e p r e s e n t s t h e number o f l e v e l s encompassed i n a g i v e n c o m p a r i s o n , where t h e v a r i a b l e l e v e l means have been a r r a n g e d i n o r d e r o f m a g n i t u d e . T h i r d , a l l s i g n i f i c a n t i n t e r a c t i o n s between c a r d i o v a s c u l a r r e a c t i v i t y and t he v i s i t s , t r i a l s , and m i n u t e s r e p e a t e d measures were p l o t t e d . F i n a l l y , S c h e f f e ' s t e s t s were u sed t o make p a i r w i s e c o m p a r i s o n s between s e l e c t e d c e l l means f r om t h e h i g h e s t - o r d e r ANCOVA i n t e r a c t i o n t e rm i n a g i v e n ANCOVA. The r e s u l t s o f t h e ANCOVAs, t r e n d a n a l y s e s , p o s t - h o c t e s t s , and g r aphs a r e p r e s e n t e d s e p a r a t e l y f o r h e a r t r a t e , s y s t o l i c b l o o d p r e s s u r e , d i a s t o l i c b l o o d p r e s s u r e , and mean a r t e r i a l p r e s s u r e i n t h e f o l l o w i n g s e c t i o n s . H e a r t Ra t e ANCOVAS Th ree a n a l y s e s o f c o v a r i a n c e o f h e a r t r a t e d a t a as o u t l i n e d above were p e r f o r m e d . These i n c l u d e d t he a f o r e m e n t i o n e d C o n d i t i o n 1, Task 1, and V i s i t 2 t y p e s o f ANCOVA. The d a t a r e p r e s e n t e d i n t h e s e a n a l y s e s a r e p l o t t e d i n - 79 -F i g u r e s 1, 2 , and 3 . The summary ANCOVA t a b l e s a r e p r e s e n t e d i n A p p e n d i c e s 5, 6 , and 7, r e s p e c t i v e l y . I n each a n a l y s i s c a r d i o v a s c u l a r r e a c t i v i t y was d e f i n e d on t he b a s i s o f s y s t o l i c b l o o d p r e s s u r e r e a c t i v i t y t o t h e f i r s t s t r e s s t a s k i n t h e i n i t i a l e x p e r i m e n t a l s e s s i o n . C o n d i t i o n 1 ANCOVA. The a n a l y s i s o f c o v a r i a n c e a p p l i e d t o t h e C o n d i t i o n 1 ( r e p e a t e d e x p o s u r e ) h e a r t r a t e d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r s y s t o l i c r e a c t i v i t y G r o u p s , F ( l , 27) = 3 0 . 5 4 , £ < . 0000 ; V i s i t s , F ( l , 28) = 3 9 . 3 4 , £ < - 0001 ; T r i a l s , F ( 2 , 57) = 3 4 . 7 5 , £ < . 0 0 0 1 , e = . 6 9 9 ; and M i n u t e s v a r i a b l e s , F ( 2 , 58) = 5 2 . 5 6 , £ < . 0 0 0 1 , e = . 7 1 0 . The Groups ma in e f f e c t i n d i c a t e d t h e p r e s e n c e o f s i g n i f i c a n t d i f f e r e n c e s i n h e a r t r a t e between t h e h i g h and low s y s t o l i c r e a c t i v i t y g r o u p s . P r e - t a s k h e a r t r a t e b a s e l i n e was s i g n i f i c a n t l y r e l a t e d t o t h e g r oup s e f f e c t , F_(l, 27) = 5 4 . 4 8 , £ < . 0 0 0 1 . The V i s i t s , T r i a l s , and M i n u t e s ma in e f f e c t s p r o v i d e e v i d e n c e o f d i f f e r e n c e s i n h e a r t r a t e a c r o s s t h e l e v e l s - o f ea ch o f t h e s e v a r i a b l e s . Ave r age h e a r t r a t e was s i g n i f i c a n t l y l owe r d u r i n g t h e second v i s i t . The V i s i t s ma in e f f e c t was s i g n i f i c a n t l y r e l a t e d t o t h e b a s e l i n e c o v a r i a t e , F_(l, 28) = 2 9 . 2 5 , £ < . 0 0 0 1 . A t r e n d a n a l y s i s o f t h e T r i a l s ma in e f f e c t y i e l d e d s i g n i f i c a n t l i n e a r , F ( l , 28) = 1 3 . 0 6 , £ < . 0 0 1 2 , and q u a d r a t i c t r e n d s , F ( l , 28) = 8 . 9 9 , £ < . 0 0 5 6 . Newman-Keuls t e s t s were p e r f o rmed t o a s s e s s t h e d i r e c t i o n a l i t y o f t h e s e t r e n d s . The r e s u l t s o f t h e Newman-Keuls t e s t s a r e p r e s e n t e d i n Append i x 8 . D i f f e r e n c e s i n h e a r t r a t e a c r o s s t r i a l s 1, 2 , and 3 were compared . S i g n i f i c a n t d i f f e r e n c e s were f ound between t r i a l s 1 and 3 , q ( 5 7 ) = 3 . 7 1 , r_ = 3 , and between t r i a l s 1 and 2, q ( 5 7 ) = 3 . 0 8 , _r = 2, £ < . 0 5 . No s i g n i f i c a n t d i f f e r e n c e s were f ound between t r i a l s 2 and 3 . These r e s u l t s i n d i c a t e t h a t d e c r e a s e s i n h e a r t r a t e were g r e a t e s t f r om t r i a l 1 t o t r i a l 2, w i t h s m a l l e r d e c r e a s e s f r om t r i a l 2 t o t r i a l 3 . T r end a n a l y s i s o f t h e m i n u t e s v a r i a b l e y i e l d e d s i m i l a r l i n e a r , F_(l, 29) = FIGURE 2 TASK I HEART RATE VISIT I VISIT II 120-1 110 H 3 £ © 100-Q. W o £ 90H < a: 80 H \ Legend 1 'HMS«SCUCIC»OCR5<XM>»Vl 3 •io»srsiajiEAacR5<gMVVi 4 'uwagcucioooiscawva 5 -ms«njciocCT»cow»vi 8 • i a » s t a o u c i o Q O H S < p i B A a 70 H 60-V1/FIRST TASK 4 WK. INTERVAL V2/FIRST TASK oo o FIGURE 3 IIO-i VISIT 2 HEART RATE DATA 105 H JD 100-1 c c3 95 -OL CO •+-O (D X> 90 -ce 8 5 -h -< Ixl X 80H 75-\ \\ \ \ \ V 11 3 q 6 12 - O 1 2 3 4 5 6 7 8 9 10 11 12 Legend •misBPtEianK&aa/tmu »HmSg>BDOF3g<XK)/rm3 'tOWSBPBBICOtVCf3C»lHC2 •lQW»IOCCT5VCCHi|^W.3 •HMSgHDOCBS'tXKtVTWU •HWSBPIEWICHS<XMai1ll»t2 -U»ygPRE*aCB5*XX>VBMU •ia>»SBPipcos<iKiimi<i2 70- -i 1 r TRIAL 1 ~i 1 TRIAL 2 T 1 r TRIAL 3 - 82 -68.27, £ < .0001, and quadratic trends, F ( l , 29) = 8.95, £ < .0001. The only decreases in heart rate occurred from minutes 1 to 2, q(29) = 3.6, r_= 2, £ < .05. Decreases from minute 2 to minute 3 were not significant (see Appendix 8). The systol ic react ivity Groups variable also showed a significant interaction with each of the V i s i t s , F ( l , 28) = 10.96, £ < .0026; T r i a l s , F(2, 56) = 12.31, £ < .0003, e = .699; and Minutes variables, F(2, 58) = 8.21, £ < .0007, e = .710. High systol ic reactors displayed means of 94 and 82 beats per minutes during v i s i t s 1 and 2. The mean heart rate for low reactors was 85 and 79 beats per minute. Across t r i a l s the mean heart rate was 99, 89, and 81 for high reactors and 83, 80, and 78 beats per minute for low reactors. The mean heart rate across minutes was 97, 89, and 83 for high reactors and 84, 79, 78 beats per minute for low reactors. Inspection of these mean scores indicates that high systol ic reactors show greater decreases in heart rate across v i s i t s , t r i a l s and minutes. A significant V i s i t by Tr ia l s by Groups interaction also occurred, F_(2, 57) = 11.16, £ < .0001, e = .747. This interaction i s presented in Figure 19. Between groups differences in heart rate across t r i a l s were greatest during the f i r s t laboratory session. The presence of significant Tr ia l s ( l inear) X Groups, F_(l, 28) = 8.53, £ < .0068, and Minutes (l inear) X Groups, F_(l, 29) = 10.94, £ < .0025, interactions also suggests that the linear nature of heart rate changes across Tr ia l s and Minutes varies as a function of systol ic react iv i ty . A comparison of the effects of short (3 minutes) versus long (4 weeks) inter-stressor intervals on high versus low systol ic reactors yielded no significant between-group differences in heart rate. Significant Vis i t s by T r i a l s , F(2, 57) = 12.47, £ < .0002, e = .747; Vis i t s by Minutes, F(2, 58) = 7.09, £ < .0032, e = .844; and Tr ia l s by 83 FIGURE 19. CONDITION 1 HEART RATE TRIALS X VISITS X GROUPS 110-1 i 1 r 1 2 3 TRIALS - 84 -M i n u t e s , F ( 4 , 116) = 1 1 . 6 5 , _p_ < . 0 0 0 1 , e = . 7 3 0 , i n t e r a c t i o n s were a l s o f o u n d . The r e s u l t s s u g g e s t t h a t d e c r e a s e s a c r o s s T r i a l s and a c r o s s M i n u t e s were g r e a t e s t i n t h e f i r s t v i s i t , and d e c r e a s e s a c r o s s m i n u t e s were g r e a t e s t i n t r i a l 1 and l e s s i n t r i a l s 2 and 3 . S c h e f f e ' s t e s t s p e r f o rmed on t h e c e l l means f r om t he h i g h e s t - o r d e r g r oups X v i s i t s X t r i a l s X m i n u t e s i n t e r a c t i o n r e v e a l e d no s i g n i f i c a n t between g roup d i f f e r e n c e s i n h e a r t r a t e d u r i n g t h e f i n a l m i nu t e o f t h e f i n a l s t r e s s t a s k i n v i s i t 2 (p_ < . 0 5 ) . These r e s u l t s a r e p r e s e n t e d i n Append i x 9 . F i n a l l y , a number o f t r e n d i n t e r a c t i o n s were f ound w h i c h were no t o f p r i m a r y i m p o r t a n c e w i t h r e g a r d t o t h e p r e s e n t e x p e r i m e n t a l h y p o t h e s e s . These i n c l u d e d V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) , F ( l , 28) = 1 0 . 3 2 , JJ < . 0 0 3 3 , T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 29) = 2 7 . 9 4 , _p_ < . 0 0 0 1 , V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) X G r o u p s , F ( l , 28) = 1 1 . 2 5 , JJ < . 0 0 2 3 , V i s i t s ( l i n e a r ) X T r i a l s ( q u a d r a t i c ) X G r o u p s , F ( l , 28) = 1 0 . 4 0 , JJ < . 0 0 3 2 , and V i s i t s ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 29) = 1 2 . 1 5 , £ < . 0 0 1 6 . The C o n d i t i o n 1 H e a r t Ra t e Summary ANCOVA t a b l e i s p r e s e n t e d i n Append i x 5 . Task 1 ANCOVA. The Task 1 ANCOVA i n v o l v e d c o n d i t i o n s and r e a c t i v i t y g r oups as between g roup v a r i a b l e s , and v i s i t s and m i n u t e s as f a c t o r i a l r e p e a t e d m e a s u r e s . The summary ANCOVA t a b l e f o r t h e Task 1 h e a r t r a t e ANCOVA i s p r e s e n t e d i n Append i x 6 and F i g u r e 2 . The m i n u t e s v a r i a b l e was based on h e a r t r a t e r e a d i n g s f r om t he f i r s t s t r e s s t a s k i n ea ch v i s i t . The a n a l y s i s o f c o v a r i a n c e o f Ta sk 1 h e a r t r a t e d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r s y s t o l i c r e a c t i v i t y g r o u p s , F ( l , 55) = 5 2 . 1 8 , JJ < . 0 0 0 1 ; v i s i t s , F ( l , 56) = 5 6 . 0 4 , JJ < . 0 0 0 1 ; and m i n u t e s , F ( 2 , 114) = 6 6 . 3 5 . The Groups ma in e f f e c t i n d i c a t e d t he p r e s e n c e o f s i g n i f i c a n t between g roup d i f f e r e n c e s i n h e a r t r a t e , r e g a r d l e s s o f e x p e r i m e n t a l c o n d i t i o n . B a s e l i n e h e a r t r a t e was a s i g n i f i c a n t c o v a r i a t e o f t h e g r oups v a r i a b l e s , F_(l, 55) = 2 7 . 9 0 , JJ < . 0 0 0 1 . B o t h b a s e l i n e 85 and f i r s t task heart rate were signif icantly higher in the high systolic reactivity group. The main effect for experimental conditions, i . e . , repeated versus single stressor exposure during V i s i t 1 was non-significant, which indicated that on average heart rate levels during the f i r s t task of each session did not vary across conditions. The Vis i t s and Minutes main effects indicate the presence of significant differences in heart rate across the levels of each of these variables. For both experimental conditions average heart rate during task 1 was lower during the second v i s i t . Pre-task baseline was a significant covariate of the v i s i t s effect, F ( l , 56) = 34.39, JJ_ < .0001. A trend analysis of the Minutes main effect yielded a significant linear trend, _F(1, 57) = 97.66, JJ < .0001. Newman-Keuls tests revealed significant decreases in heart rate from minute 1 to 2, q(57) = 7.25, jr = 2, and from minute 2 to minute 3, Q(57) = 5.35, r_ = 2, p_ < .05. The magnitude of heart rate decreases was greatest from minute 1 to 2 with lesser decreases from minute 2 to 3 (see Appendix 8). The reactivity Groups variable showed a significant interaction with the V i s i t s , F ( l , 56) = 18.12, JJ < .0001, and the Minutes variables, F(2, 114) = 7.40, JJ < .0010, e = .8051. High systolic reactors showed a mean heart rate of 107 beats per minutes (bpm) in v i s i t 1 and 94 bpm in v i s i t 2. The means for low reactors across v i s i t s were 86 and 82 bpm. Across minutes the mean heart rate for high reactors was 108, 101, and 92 bpm. For low systolic reactors the respective minute heart rate means were 90, 82, and 81 bpm. These means reveal that high systolic reactors show greater decreases in heart rate than low reactors across v i s i t s and minutes. In addition, a significant Conditions X Groups X Vis i t s interaction, F_(l, 56) = 4.39, JJ < .0406, reveals that between groups differences in heart rate from v i s i t 1 to v i s i t 2 were greatest in the repeated stress condition. This interaction i s displayed in - 86 _ Figure 13. The presence of s i g n i f i c a n t Minutes ( l i n e a r ) X Groups, F_(l, 56) = 7.63, £ < .0077, and Minutes (quadratic) X Groups, F(2, 57) = 6.91, £ < .0110, trend i n t e r a c t i o n s suggests that the l i n e a r i t y of decreases i n heart rate across minutes varies as a function of s y s t o l i c r e a c t i v i t y . A s i g n i f i c a n t V i s i t s by Minutes, F(2, 114) = 7.97, £ < .0011, e = .857, i n t e r a c t i o n was also found. Decreases across minutes were greatest during the f i r s t v i s i t . F i n a l l y , two trend i n t e r a c t i o n s which were not of primary importance were found. These were V i s i t s ( l i n e a r ) X Minutes ( l i n e a r ) , F_(l, 57) = 14.21, £ < .0004 and V i s i t s ( l i n e a r ) X Minutes ( l i n e a r ) X Groups, F ( l , 57) = 4.01, £ < .0499. Scheffe's t e s t s were used to make pairwise comparisons of the Conditions X Groups X V i s i t s X Minutes c e l l means. Results are displayed i n Appendix 9. The Scheffe's test indicated no s i g n i f i c a n t between group differences (£ < .05) i n heart rate during the f i n a l minute of the f i n a l s tress task for subjects i n Condition 1, V i s i t 2. The heart rate responses of the high s y s t o l i c reactors were in d i s t i n g u i s h a b l e from those of the low reactors. V i s i t 2 ANCOVA. The v i s i t 2 heart rate ANCOVA was based s o l e l y on data c o l l e c t e d during the second experimental session. Conditions and r e a c t i v i t y were between group f a c t o r s , T r i a l s and Minutes were f a c t o r i a l repeated measures. The summary ANCOVA table i s presented i n Appendix 7. The data are displayed i n Figure 3. The analysis of covariance yielded s i g n i f i c a n t main e f f e c t s for Conditions, F_(l, 55) = 4.57, £ < .0369, r e a c t i v i t y Groups, F_(l, 55) = 15.05, p < .0003, T r i a l s , F(2, 113) = 12.52, £ < .0001, e = .782, and Minutes, F(2,114) = 61.93, £ < .0001, e = .742. Heart rate was s i g n i f i c a n t l y higher i n Condition 2, i . e . , si n g l e exposure. High s y s t o l i c reactors also displayed higher heart rates during v i s i t 2. Pre-task baseline, F_(l, 55) = 287.10, £ < .0001, and age of subject, F ( l , 55) = 4.57, £ < .0370, were 87 FIGURE 13. TASK I HEART RATE DATA VISIT X CONDITION X GROUP INTERACTION - 8 8 -significant covariates of the conditions and groups main effects. The Tr ia l s and Minutes main effects provided evidence of differences in heart rate across the levels of these two variables. The t r i a l s variable was s ignif icantly related to the baseline covariate, F_(l, 113) = 21.96, JJ < .0001. The linear and quadratic trends for the t r i a l s effects were non-significant. Newman-Keuls tests revealed significant decreases in heart rate from T r i a l 1 to 2, q(113) = 7.7, r_ = 2, and from T r i a l 2 to T r i a l 3, q(57 = 3.56, r_=2, JD< .05. A trend analysis of the minutes main effect yielded a significant linear trend, F_(l, 57) = 74.19, JJ < .0001. Significant decreases in heart rate occurred from Minute 1 to Minute 2, q(57) = 6.44, r_ = 2, J J < .05. Decreases from minutes 2 to 3 were not significant (see Appendix 8). The systol ic react ivity groups variable showed a significant two-way interaction with Minutes, F_(2, 114) = 7.69, JJ < .0024, e = .742 and a significant three-way interaction with Tr ia l s X Minutes, _F(4, 228) = 3.08, JJ < .0296. The three-way interaction i s displayed in Figure 14. High systol ic reactors showed a greater decrease in heart rate across minutes than did low reactors. The mean heart rate for high reactors across Minutes was 95, 88, and 85 bpm. Low reactors displayed means of 83, 78, 78 bpm across minutes. These between group differences across minutes were greatest on t r i a l 1 and smaller on subsequent t r i a l s . The presence of significant Minutes (linear) X Groups, F ( l , 57) = 9.71, JJ < .0029 and Tr ia l s (quadratic) X Groups, F ( l , 56) = 6.07, jj < .0169 trend interactions indicates that the slope of heart rate changes across t r i a l s and minutes parallels level of systol ic react iv i ty . A significant Tr ia l s X Minutes interaction, F(4, 228)) = 4.39, JJ < .0055, e = .739 was found. Decreases in heart rate across minutes were greatest on t r i a l 1 and less on subsequent t r i a l s . Additional trend interactions which 89 FIGURE 14. VISIT 2 HEART RATE DATA TRIAL X MINUTE X GROUP INTERACTION 105-i 100 H •§ 95-c CD Q. jo 90-D CD •Q C UJ 85-i2 80-75 H 70- ~~T~ 3 Legend A TRIAL 1/H SBP REACTORS X TRUL2/H SBP REACTORS • TRUU. 3/H SBP REACTORS B TRIAL VLO SBP REACTORS MINUTES - 90 _ were no t o f d i r e c t i n t e r e s t w i t h r e s p e c t t o t h e p r e s e n t h y p o t h e s e s were T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 57) = 1 1 . 4 6 , £ < . 0 0 1 3 , T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) X C o n d i t i o n s , J _ ( l , 57) = 4 . 3 6 , JJ < . 0 4 1 3 , and T r i a l s ( l i n e a r ) X M i n u t e s ( q u a d r a t i c ) X G r o u p s , F ( l , 5 7 _ = 6 . 1 3 , £ < . 0 1 6 3 . F i n a l l y , S c h e f f e ' s t e s t s were u sed t o c ondu c t p a i r w i s e c o m p a r i s o n s o f s e l e c t e d c o n d i t i o n s X G roups X T r i a l s X M i n u t e s c e l l means. The means and c r i t i c a l v a l u e s used i n t h e S c h e f f e ' s t e s t s a r e d i s p l a y e d i n Append i x 9 . No s i g n i f i c a n t d i f f e r e n c e s (JJ < . 05 ) i n h e a r t r a t e were f ound i n a c o m p a r i s o n o f t h e C o n d i t i o n 1, h i g h v e r s u s l ow s y s t o l i c r e a c t o r s d u r i n g t h e f i r s t m i nu t e o f t h e f i n a l s t r e s s t a s k . These r e s u l t s i n d i c a t e t h a t a r e p e t i t i o n o f s i x s t r e s s o r p r e s e n t a t i o n s o ve r two s e s s i o n s was s u f f i c i e n t t o make i n i t i a l b e tween -g roup d i f f e r e n c e s i n h e a r t r a t e r e a c t i v i t y d i s a p p e a r . S y s t o l i c B l o o d P r e s s u r e ANCOVAS Th r ee a n a l y s e s o f c o v a r i a n c e o f s y s t o l i c b l o o d p r e s s u r e d a t a were p e r f o r m e d . These i n c l u d e d t he a f o r e m e n t i o n e d C o n d i t i o n 1, Task 1, and V i s i t 2 t y p e s o f ANCOVAS. The d a t a r e p r e s e n t e d i n t h e s e a n a l y s e s a r e p r e s e n t e d i n F i g u r e s 4 , 5 and 6 . The summary ANCOVA t a b l e s a r e p r e s e n t e d i n A p p e n d i c e s 10 , 1 1 , and 1 2 , r e s p e c t i v e l y . I n each a n a l y s i s c a r d i o v a s c u l a r r e a c t i v i t y was d e f i n e d on t h e b a s i s o f h e a r t r a t e r e a c t i v i t y t o t h e f i r s t s t r e s s t a s k i n t h e i n i t i a l e x p e r i m e n t a l s e s s i o n . C o n d i t i o n 1 ANCOVA. The a n a l y s i s o f c o v a r i a n c e o f C o n d i t i o n 1 ( r e p e a t e d e x p o s u r e ) s y s t o l i c b l o o d p r e s s u r e d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r h e a r t r e a c t i v i t y g r o u p s , F ( l , 31) = 2 1 , 3 1 , £ < . 0 0 0 1 , v i s i t s , F ( l , 32) = 4 4 . 4 4 , JJ < . 0 0 0 1 , T r i a l s , F ( 2 , 65) = 1 8 . 6 3 , £ < . 0 0 0 1 , e = . 9 8 0 , and M i n u t e s , F ( 2 , 66) = 7 . 5 4 , £ < . 0 0 1 6 , e = . 9 2 3 . S y s t o l i c b l o o d p r e s s u r e was s i g n i f i c a n t l y h i g h e r i n t h e h i g h h e a r t r a t e r e a c t o r g r o u p . P r e - t a s k b a s e l i n e was a s i g n i f i c a n t c o v a r i a t e o f t h e r e a c t i v i t y v a r i a b l e , F_(l, 31) = 1 2 4 . 8 5 , £ < FIGURE 5 TASK I SYSTOLIC BLOOD PRESSURE DATA H O - i VISIT I VISIT II 135 H CD sz E E C 130-OO to UJ £ 125" Q O 3 CO O 120-00 >-to 115-4 WK. INTERVAL 1 2 3 4 5 6 7 Legend hPHrRREQ3RS*X>Cyv2 110-FIRST TASK FIRST TASK FIGURE 6 130-. 125-1 c n E E c 120-LJ cm CO CO UI £ 115-o o 3 m y iio-_ l CO >-CO 105-VISIT 2 SYSTOUC BLOOD PRESSURE DATA 7 4 / 9 * i i 6 Q 12 H * Legend 1 *HGHWIBClCR5<XHVimi 2 'WwipgoB»tOK)»Tw»a 3 -TOwic«cioH5ytoivni«L3 7 -HGHHR HDOCRS/COCg/lTMtJ 8 -mH>ia>goHS«M]g/iiwta 10 •1W«WWEBBC»CR5A2 11 'iwKieqcHs/mm 12 • W t < ' P O g B / l l W 3 ffl 100- ~i 1 1 — i — : 1 r TRIAL 1 TRIAL 2 ~i 1 r TRIAL 3 _ 9 3 _ . 0 0 0 1 . The ma in e f f e c t s f o r V i s i t s , T r i a l s , and M i n u t e s p r o v i d e d e v i d e n c e o f s i g n i f i c a n t d i f f e r e n c e s i n s y s t o l i c p r e s s u r e a c r o s s l e v e l s o f ea ch o f t h e s e v a r i a b l e s . Mean s y s t o l i c b l o o d p r e s s u r e was s i g n i f i c a n t l y l o w e r d u r i n g t h e second v i s i t . B a s e l i n e s y s t o l i c p r e s s u r e was a s i g n i f i c a n t c o v a r i a t e o f t h e V i s i t s ma in e f f e c t , F ( l , 32) = 2 9 . 7 1 , £ < . 0 0 0 1 . A t r e n d a n a l y s i s o f T r i a l s ma in e f f e c t y i e l d e d s i g n i f i c a n t l i n e a r , F ( l , 32) = 1 8 . 4 3 , _p_ < . 0 0 0 2 , and q u a d r a t i c t r e n d s , F ( l , 32) = 4 . 9 7 , £ < . 0 3 3 0 . Newman-Keuls t e s t s were p e r f o rmed t o f u r t h e r a s s e s s t h e changes i n s y s t o l i c p r e s s u r e a c r o s s t r i a l s . The r e s u l t s o f t h e s e t e s t s a r e p r e s e n t e d i n A p p e n d i x 1 3 . S i g n i f i c a n t d e c r e a s e s i n s y s t o l i c p r e s s u r e o c c u r r e d f r om t r i a l 1 t o t r i a l 2 , q ( 6 5 ) = 4 . 7 5 , r_ = 2 , and f r om t r i a l t o 2 t o 3 , ( 65 ) = 3 . 7 5 , r. = 2, £ < . 0 5 . The magn i t ude o f t h i s d e c r e a s e was i n v e r s e l y r e l a t e d t o t h e number o f t r i a l s . A s i g n i f i c a n t q u a d r a t i c t r e n d was f ound w i t h r e g a r d t o M i n u t e s ma in e f f e c t , F_(2, 66) = 1 6 . 5 2 , £ < . 0 0 0 3 . On a v e r a g e , mean s y s t o l i c p r e s s u r e l e v e l s were h i g h e s t d u r i n g m i nu t e 2 . No s i g n i f i c a n t d i f f e r e n c e s were f ound i n p a i r w i s e c o m p a r i s o n s o f m i nu t e by m i nu t e p r e s s u r e l e v e l s . On l y t h e V i s i t s r e p e a t e d measure showed a s i g n i f i c a n t i n t e r a c t i o n w i t h t h e r e a c t i v i t y b e tween -g r oups v a r i a b l e , F_(l, 32) = 7 . 2 9 , £ < . 0 1 1 0 . The v i s i t means f o r h i g h h e a r t r a t e r e a c t o r s were 124 and 115 mm Hg . Low r e a c t o r s d i s p l a y e d mean s y s t o l i c p r e s s u r e o f 119 and 111 mm Hg d u r i n g v i s i t s 1 and 2 . I n s p e c t i o n o f t h e s e means i n d i c a t e s t h a t h i g h h e a r t r a t e r e a c t o r s showed s l i g h t l y l a r g e r d e c r e a s e s i n s y s t o l i c p r e s s u r e a c r o s s v i s i t s t h a n d i d l ow r e a c t o r s . A s i g n i f i c a n t V i s i t s by T r i a l s i n t e r a c t i o n , F_(2, 65) = 5 . 2 0 , £ < . 0 1 1 5 , e = . 8 5 9 , r e v e a l e d t h a t a c r o s s t r i a l d e c r e a s e s i n s y s t o l i c b l o o d p r e s s u r e were g r e a t e s t d u r i n g v i s i t 1. A c o m p a r i s o n o f t h e e f f e c t s o f s h o r t ( 3 m i n u t e s ) v e r s u s l o n g (4 weeks) i n t e r - s t r e s s o r i n t e r v a l s on h i g h v e r s u s l ow h e a r t r a t e r e a c t o r s y i e l d e d no s i g n i f i c a n t between g roup d i f f e r e n c e s i n - 94 -s y s t o l i c b l o o d p r e s s u r e . F i n a l l y , s i g n i f i c a n t t r e n d i n t e r a c t i o n s were f ound f o r V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) F ( 2 , 65) = 4 . 7 8 , £ < . 0 3 6 0 , and V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) , F ( l , 32) = 1 3 . 4 9 , JJ < . 0 0 0 9 . These t r e n d i n t e r a c t i o n s were no t o f p r i m a r y i n t e r e s t . S c h e f f e ' s t e s t s were used t o make p a i r w i s e c o m p a r i s o n s o f g r oups X v i s i t s X t r i a l s X m i n u t e s c e l l means. R e s u l t s i n d i c a t e d t h a t s i g n i f i c a n t between g roup d i f f e r e n c e s i n s y s t o l i c p r e s s u r e r ema i ned a t t h e end o f t h e f i n a l s t r e s s t a s k . The S c h e f f e ' s v a l u e s a r e p r e s e n t e d i n Append i x 14 . Ta sk 1 ANCOVA. The Task 1 ANCOVA i n v o l v e d c o n d i t i o n s and r e a c t i v i t y g r oups a s be tween-g roup v a r i a b l e s , and V i s i t s and M i n u t e s as r e p e a t e d m e a s u r e s . The summary ANCOVA f o r t h e Task 1 s y s t o l i c b l o o d p r e s s u r e i s p r e s e n t e d i n Append i x 1 1 . The M i n u t e s v a r i a b l e was based on s y s t o l i c r e a d i n g s t a k e n d u r i n g t h e f i r s t s t r e s s t a s k i n ea ch o f t h e two s e s s i o n s . The a n a l y s i s o f c o v a r i a n c e o f Task 1 s y s t o l i c d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r r e a c t i v i t y G r o u p s , F ( l , 62) = 7 0 . 6 0 , JJ < . 0 0 0 1 , V i s i t s , F ( l , 63) = 5 1 . 0 4 , p < .0001 and M i n u t e s , F ( 2 , 128) = 1 0 . 2 4 , £ < . 0 0 0 1 , e = . 9 6 4 . The ma in e f f e c t f o r e x p e r i m e n t a l c o n d i t i o n s was n o t s i g n i f i c a n t . The h e a r t r a t e r e a c t i v i t y g roup ma in e f f e c t i n d i c a t e d t h e p r e s e n c e o f s i g n i f i c a n t between g roup d i f f e r e n c e s i n s y s t o l i c p r e s s u r e r e g a r d l e s s o f e x p e r i m e n t a l c o n d i t i o n . B a s e l i n e h e a r t r a t e was a s i g n i f i c a n t c o v a r i a t e o f t h e g r oup s ma in e f f e c t , _F(1, 62) = 1 1 2 . 6 3 , £ < . 0 0 1 . The ma in e f f e c t f o r e x p e r i m e n t a l c o n d i t i o n s was no t s i g n i f i c a n t . The v i s i t s and m i n u t e s ma in e f f e c t s i n d i c a t e s i g n i f i c a n t d i f f e r e n c e s i n s y s t o l i c b l o o d p r e s s u r e l e v e l s a c r o s s t h e v i s i t s and m i n u t e s . S y s t o l i c b l o o d p r e s s u r e was h i g h e r d u r i n g t h e f i r s t v i s i t . P r e - t a s k b a s e l i n e was a l s o a s i g n i f i c a n t c o v a r i a t e o f t h e V i s i t s ma in e f f e c t , F_(l, 63) = 6 . 3 8 , £ < . 0 1 4 1 . A t r e n d a n a l y s i s o f t h e M i n u t e s ma in e f f e c t y i e l d e d s i g n i f i c a n t l i n e a r , F_(l, _ 9 5 _ 64) = 4 . 0 6 , £ < .0481 and q u a d r a t i c t r e n d s , F ( l , 64) = 1 8 . 6 9 , £ < . 0 0 0 1 . Newman-Keuls t e s t s r e v e a l e d a s i g n i f i c a n t i n c r e a s e i n s y s t o l i c p r e s s u r e f r om m i n u t e 1 t o m i n u t e 2, q ( 6 4 ) = 3 . 7 5 , r_ = 2 , and a s i g n i f i c a n t d e c r e a s e f r om m i n u t e 2 t o m i n u t e 3 , q ( 6 4 ) = 1 . 75 , r_ = 2, £ < . 0 5 . Mean s y s t o l i c b l o o d p r e s s u r e was h i g h e s t d u r i n g t h e s e cond m inu t e o f t h e t a s k p e r i o d . T h i s p a t t e r n o f r e s u l t s s u g g e s t s s y s t o l i c b l o o d p r e s s u r e showed a s l o w e r a r o u s a l r e s p o n s e t h a n h e a r t r a t e t o t h e m e n t a l a r i t h m e t i c s t r e s s o r . The r e s u l t s a r e d i s p l a y e d i n Append i x 1 3 . The h e a r t r a t e r e a c t i v i t y g r oups v a r i a b l e showed a s i g n i f i c a n t i n t e r a c t i o n w i t h t h e V i s i t s , F ( l , 63) = 1 5 . 4 8 , £ < .0002 and t he M i n u t e s v a r i a b l e s , F ( 2 , 128) = 5 . 1 0 , £ < . 0 0 8 1 , e = . 9 6 4 . The v i s i t means were 129 and 120 f o r h i g h r e a c t o r s and 116 and 115 mm Hg f o r l ow r e a c t o r s . A c r o s s m i n u t e s h i g h r e a c t o r s d i s p l a y e d means o f 1 2 1 , 1 2 5 , and 120 mm Hg . Low r e a c t o r s showed m i nu t e means o f 1 15 , 116 and 115 mm H g . These means r e v e a l t h a t h i g h h e a r t r a t e r e a c t o r s show a g r e a t e r d e c r e a s e i n s y s t o l i c p r e s s u r e a c r o s s v i s i t s and a g r e a t e r d e c r e a s e i n s y s t o l i c p r e s s u r e f r om m i n u t e 2 t o 3 o f t h e t a s k p e r i o d . A s i g n i f i c a n t M i n u t e s ( l i n e a r ) X G roups i n t e r a c t i o n , F_(l, 64) = 6 . 7 3 , £ < .0118 was a l s o f o u n d . The l i n e a r t r e n d f o r m i n u t e s i s much s t r o n g e r i n t h e low h e a r t r a t e r e a c t i v i t y g r o u p . The V i s i t s ( l i n e a r ) X M i n u t e s ( l i n e a r ) i n t e r a c t i o n was a l s o s i g n i f i c a n t , F_(l, 64) = 4 . 6 5 , £ < . 0 3 4 8 . F i n a l l y , S c h e f f e ' s t e s t s were u sed t o make p a i r w i s e c o m p a r i s o n o f c e l l means d u r i n g t he f i r s t t a s k i n t h e s e cond v i s i t . H i g h and l ow h e a r t r a t e r e a c t o r s i n t h e s i n g l e e x p o s u r e c o n d i t i o n ( 2 ) showed no d i f f e r e n c e i n s y s t o l i c p r e s s u r e d u r i n g t h e f i r s t m i n u t e o f f i r s t s t r e s s t a s k i n t h e second v i s i t . S i g n i f i c a n t between g roup d i f f e r e n c e s i n s y s t o l i c p r e s s u r e r ema i ned d u r i n g t he f i n a l m i nu t e o f t h e t a s k . R e s u l t s a r e p r e s e n t e d i n Append i x 14 . V i s i t 2 ANCOVA. The v i s i t 2 s y s t o l i c b l o o d p r e s s u r e ANCOVA was based on 9 6 d a t a c o l l e c t e d d u r i n g t h e second s e s s i o n . C o n d i t i o n s and h e a r t r a t e r e a c t i v i t y were between g roup f a c t o r s and T r i a l s and M i n u t e s were f a c t o r i a l r e p e a t e d m e a s u r e s . The ANCOVA summary t a b l e i s p r e s e n t e d i n Append i x 1 2 . S i g n i f i c a n t ma in e f f e c t s were f ound f o r g r o u p s , F_(l, 62) = 3 0 . 6 9 , JJ < . 0 0 0 1 ; t r i a l s , F ( 2 , 127) = 3 . 7 1 , £ < . 0317 , e = . 8 9 8 ; and m i n u t e s , F ( 2 , 1 2 8 ) = 6 . 3 5 , JJ < . 0 0 1 1 , e = . 9 7 5 . P r e - t a s k b a s e l i n e was a s i g n i f i c a n t c o v a r i a t e o f t h e g r o u p s , F ( l , 62) = 1 6 1 . 2 9 , JJ < .0001 and t r i a l s , F ( l , 1 2 7 ) = 1 3 . 4 9 , JJ < . 0 0 0 4 . The ma in e f f e c t f o r e x p e r i m e n t a l C o n d i t i o n s was n o t s i g n i f i c a n t . Newman-Keuls t e s t s were used t o f u r t h e r a s s e s s t h e n a t u r e o f changes i n s y s t o l i c p r e s s u r e a c r o s s l e v e l s o f t h e T r i a l s and M i n u t e s v a r i a b l e s . S i g n i f i c a n t d e c r e a s e s i n s y s t o l i c b l o o d p r e s s u r e were f ound f r om t r i a l 1 t o 2, q ( 127 ) = 2 . 9 2 , £ = 2, and f r om t r i a l 2 t o t r i a l 3 , q ( 127 ) = 6 . 4 2 , r_ = 2, £ < . 0 5 . A s i g n i f i c a n t i n c r e a s e i n s y s t o l i c p r e s s u r e was seen f r om m inu t e 1 t o m i nu t e 2, q ( 1 2 8 ) = 2 . 1 7 , r_ = 2, w h i l e s y s t o l i c p r e s s u r e d e c r e a s e d s i g n i f i c a n t l y f r om m i n u t e 2 t o m i n u t e 3 , q ( 128 ) = 1 0 . 1 7 , r_ = 2, £ < . 0 5 . R e s u l t s a r e d i s p l a y e d i n A p p e n d i x 1 3 . A s i g n i f i c a n t T r i a l s ( l i n e a r ) X G r o u p s , F ( l , 63) = 6 . 4 3 , £ < .0137 i n t e r a c t i o n was f o u n d . T h i s r e s u l t i n d i c a t e d t h a t t h e l i n e a r n a t u r e o f d e c r e a s e s i n s y s t o l i c p r e s s u r e a c r o s s t r i a l s v a r i e d as a f u n c t i o n o f h e a r t r a t e r e a c t i v i t y . I n a d d i t i o n , t h e b a s e l i n e c o v a r i a t e was s i g n i f i c a n t l y r e l a t e d t o t h e T r i a l s ( l i n e a r ) e f f e c t , F ( l , 63) = 2 2 . 4 1 , £ < . 0 0 0 1 . The q u a d r a t i c t r e n d f o r M i n u t e s , F_(l, 64) = 1 6 . 8 1 , £ < .0001 was a l s o s i g n i f i c a n t . S y s t o l i c p r e s s u r e v a l u e s showed an i n c r e a s e f r o m m inu t e 1 t o m i n u t e 2 and a d e c r e a s e f r om m i n u t e 2 t o 3 i n each t a s k p e r i o d . S u b j e c t s i n b o t h c o n d i t i o n s and b o t h r e a c t i v i t y g r oup s d i s p l a y e d t h e h i g h e s t mean s y s t o l i c l e v e l s d u r i n g t h e second m i nu t e o f ea ch t a s k p e r i o d . F i n a l l y , a s i g n i f i c a n t t h r e e - w a y C o n d i t i o n s X Groups X T r i a l s , F ( 2 , 127) = 4 . 0 5 , £ < . 0 2 3 8 , e = .898 - 97 -i n t e r a c t i o n was f o u n d . T h i s i n t e r a c t i o n i s p r e s e n t e d i n F i g u r e 1 5 . H i g h h e a r t r a t e r e a c t o r s showed g r e a t e r changes i n s y s t o l i c p r e s s u r e a c r o s s t r i a l s . T h i s e f f e c t was s t r o n g e s t i n t h e r e p e a t e d s t r e s s o r c o n d i t i o n . The p r e s e n c e o f a s i g n i f i c a n t C o n d i t i o n s X Groups X T r i a l s ( q u a d r a t i c ) e f f e c t , F_(l, 63) = 5 . 4 1 , £ < .0232 f u r t h e r i n d i c a t e s t h a t t h e q u a d r a t i c e f f e c t i s s t r o n g e s t i n t h e s i n g l e e x p o s u r e c o n d i t i o n . S c h e f f e ' s t e s t s r e v e a l e d t h a t s i g n i f i c a n t between g roup d i f f e r e n c e s i n s y s t o l i c p r e s s u r e r ema i ned d u r i n g t h e f i n a l s t r e s s t a s k f o r s u b j e c t s i n b o t h e x p e r i m e n t a l c o n d i t i o n s . R e s u l t s o f t h e S c h e f f e ' s t e s t s a r e i n Append i x 14 . D i a s t o l i c B l o o d P r e s s u r e ANCOVAS Th ree a n a l y s e s o f c o v a r i a n c e o f d i a s t o l i c b l o o d p r e s s u r e d a t a were p e r f o r m e d . The summary ANCOVA t a b l e s f o r t h e C o n d i t i o n 1, Task 1, and V i s i t 2 ANCOVAs a r e p r e s e n t e d i n A p p e n d i c e s 1 5 , 1 6 , and 17 , r e s p e c t i v e l y . I n each a n a l y s i s r e a c t i v i t y was d e f i n e d on t he b a s i s o f h e a r t r a t e r e s p o n s e s t o t h e f i r s t s t r e s s t a s k i n t h e i n i t i a l e x p e r i m e n t a l s e s s i o n . The d a t a r e p r e s e n t e d i n t h e s e a n a l y s e s a r e g r a p h i c a l l y d i s p l a y e d i n F i g u r e s 7, 8 and 9 . C o n d i t i o n 1 ANCOVA. The a n a l y s i s o f c o v a r i a n c e a p p l i e d t o t h e C o n d i t i o n 1 ( r e p e a t e d e x p o s u r e ) d i a s t o l i c b l o o d p r e s s u r e d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r r e a c t i v i t y g r o u p s , F ( l , 31) = 1 2 . 4 7 , _p_ < . 0 0 1 3 ; V i s i t s , F ( l , 32) = 3 1 . 5 3 , _p_ < . 0 0 0 1 ; T r i a l s , F ( 2 , 65) = 2 7 . 6 7 , £ < . 0 0 0 1 , e = . 9 59 ; and M i n u t e s , F ( 2 , 33) = 5 . 8 7 , _p_ < . 0 0 5 7 , e = . 9 2 3 . The Groups ma in e f f e c t i n d i c a t e s t h e p r e s e n c e o f be tween g roup d i f f e r e n c e s i n d i a s t o l i c p r e s s u r e . S u b j e c t s i n t h e h i g h h e a r t r a t e r e a c t o r g roup d i s p l a y e d h i g h e r d i a s t o l i c p r e s s u r e l e v e l s . P r e - t a s k b a s e l i n e was a s i g n i f i c a n t c o v a r i a t e o f t h e g r oups e f f e c t , F_(l, 32) = 6 0 . 1 5 , JD < . 0 0 0 1 . The V i s i t s , T r i a l s and M i n u t e s ma in e f f e c t s i n d i c a t e d i f f e r e n c e s i n d i a s t o l i c p r e s s u r e a c r o s s l e v e l s o f t h e s e v a r i a b l e s . The V i s i t s ma in e f f e c t was s i g n i f i c a n t l y r e l a t e d t o t h e b a s e l i n e c o v a r i a t e , F_(l, 98 FIGURE 15. VISIT 2 SYSTOLIC PRESSURE TRIAL X CONDITION X GROUP INTERACTION 130 n 125 H 120 H JZ E E jc U l CE CO CO Lxl O O 3 m o —i no 4 CO >-CO 105 H 100 2 Legend A COWPyX HR REACTORS X COND1/L0 HR REACTORS • CONDZ/HI HR REACTORS B COND2AJ0HR REACTORS TRIALS FIGURE 8 90 -i T A S K I D I A S T O U C B L O O D P R E S S U R E D A T A 85-VISIT I VISIT II CT JZ | 80-U l or oo 7 5 . to 7 5 L d OC CL O to < Q 70 H 65H 4 WK. INTERVAL Legend 7 'U)WWRDCI0^<XNXyV1 8 •iQMMivaaPGfiae&a 60- i r FIRST TASK FIRST TASK vo vo FIGURE 9 8O-1 VISIT 2 DIASTOLIC BLOOD PRESSURE DATA CO XT. E E c 77 H 74 H 7H 3 68-to U l £ 65-Q O 3 62H 0 0 o O 59 H to < Q 56-^ 3 1 2 3 4 5 6 7 8 9 10 11 12 Legend •HmhsiocgRvccMynwj •tqyHRREAocRs^xxymj •UWHBRaCCT5/XHyniW3 •HWHRIBODaSyttMayTIMU •HmHRtoaaf^oa^m^ •lDWHBR&aD35/<XKgrtR*U •\0Uy*l£MXfSAXKB/mL5 53-5 0 - 1 1 TRIAL 1 TRIAL 2 TRIAL 3 - 101 -32) = 13.12, £ < .0010. Diastol ic pressure levels were lower during the second experimental session. A trend analysis of the Tr ia l s main effect yielded significant l inear, F ( l , 37) = 9.37, £ < .0044 and quadratic trends, F ( l , 32) = 7.10, £ < .0120. Newman-Keuls tests showed that significant decreases in diastol ic blood pressure occurred from t r i a l 1 to t r i a l 2, q(32) = 5.42, r_ = 2, £ < .05 and from t r i a l s 2 to 3, q(32) = 3.16, r_ = 2. Decreases were largest from t r i a l s 1 to 2. A significant quadratic trend, F_(l, 33) = 11.33, £ < .0019 for minutes was found. Diastol ic pressure were highest during minute 2. No significant between-minute differences in diastol ic pressure were found. Results are displayed in Appendix 18. The heart rate react ivi ty groups variable showed a significant two-way interaction with V i s i t s , F_(l, 32) = 11.03, £ < .0023, and a significant three-way interaction with Tr ia l s X Minutes, F(4, 132) = 3.98, £ < .0080, e = .816. The three-way interaction i s displayed in Figure 16. High heart rate reactors showed a greater decrease in diastol ic pressure across v i s i t s . The mean diasto l ic pressure for high reactors.was 75 and 68 mm Hg. Low reactors displayed v i s i t means of 67 and 65 mm Hg. High heart rate reactors also showed greater changes in diastol ic pressure across minutes of the stress task. Between-group differences were greatest during the f i r s t and third t r i a l s . High and low heart rate reactors showed no differences in diastol ic blood pressure across short (3 minutes) versus long (4 weeks) inter-stressor intervals . Significant Vis i t s X T r i a l s , F(2, 65) = 5.76, £ < .0065, e = .912, and Tr ia l s X Minutes, F(4, 132) = 3.11, £ < .0258, e = .816 interactions were also found. Decreases in diastol ic pressure across t r i a l s were greatest during the f i r s t v i s i t . Changes in diastol ic pressure across minutes were larger during FIGURE 16. CONDITION 1 DIASTOUC PRESSURE TRIALS X MINUTES X GROUPS 80-, n 1 r 1 2 3 MINUTES Legend A TRIAL t/H HR REACTORS X TRIAL 1M HR REACTORS • TRIAL VHl HR REACTORS B TRIAL y\0 HR REACTORS X TRIAL VtO HR REACTORS - 103 -t h e f i r s t t r i a l . S e v e r a l s i g n i f i c a n t t r e n d i n t e r a c t i o n s , w h i c h were no t o f p r i m a r y i n t e r e s t , were f o u n d . These i n c l u d e d V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) , F ( l , 32) = 6 . 6 0 , _p_ < . 0 1 5 1 , T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 33) = 8 . 0 5 , £ < . 0 0 7 7 , V i s i t s ( l i n e a r ) X T r i a l s ( q u a d r a t i c ) , F ( l , 32) = 9179 , £ < . 0 0 3 7 , T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) X G r o u p s , F ( l , 33) = 1 0 . 8 0 , £ < . 0 0 2 4 , and V i s i t ( l i n e a r ) X T r i a l s ( q u a d r a t i c ) X G r o u p s , F ( l , 32) = 5 . 9 6 , £ < . 0 2 0 3 . S c h e f f e ' s t e s t s were u sed t o compare c e l l means d u r i n g t h e f i n a l s t r e s s t a s k . H i g h and low h e a r t r a t e r e a c t o r s d i d n o t d i f f e r i n d i a s t o l i c p r e s s u r e l e v e l s d u r i n g t h e f i n a l m i nu t e o f t h e second l a s t s t r e s s t a s k o r d u r i n g t h e f i n a l 3 m i n u t e s t r e s s t a s k . Ta sk 1 ANCOVA. The Task 1 ANCOVA i n v o l v e d c o n d i t i o n s and r e a c t i v i t y a s be tween-g roup v a r i a b l e s , and v i s i t s and m i n u t e s as r e p e a t e d m e a s u r e s . The summary ANCOVA t a b l e i s p r e s e n t e d i n Append i x 1 6 . The m i n u t e s v a r i a b l e was based on d i a s t o l i c p r e s s u r e r e a d i n g s f r om t h e f i r s t s t r e s s t a s k i n ea ch v i s i t . The a n a l y s i s o f c o v a r i a n c e o f Task 1 d i a s t o l i c d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r C o n d i t i o n s , F_(l, 62) = 6 . 7 6 , £ < . 0 1 1 6 , r e a c t i v i t y g r o u p s , F ( l , 62) = 4 1 . 2 2 , £ < . 0 0 0 1 , and V i s i t s , F ( l , 63) = 3 4 . 2 6 , £ < . 0 0 0 1 . The ma in e f f e c t f o r m i n u t e s was n o t s i g n i f i c a n t . D i a s t o l i c p r e s s u r e l e v e l s were h i g h e r i n t h e r e p e a t e d e xpo su r e c o n d i t i o n , i n t h e h i g h h e a r t r a t e r e a c t o r g r o u p s , and i n t h e second v i s i t . The b a s e l i n e c o v a r i a t e was s i g n i f i c a n t l y r e l a t e d t o b o t h t h e c o n d i t i o n s ma in e f f e c t and t h e g r oups ma in e f f e c t , F ( l , 62) = 8 9 . 6 2 , £ < . 0 0 0 1 . A s i g n i f i c a n t q u a d r a t i c t r e n d was f ound f o r t h e m i n u t e s e f f e c t , F_(l, 64) = 5 . 5 4 , £ < . 0 2 1 6 . D i a s t o l i c p r e s s u r e was h i g h e s t d u r i n g t h e s e cond m i nu t e o f t h e t a s k p e r i o d . F i n a l l y , a s i g n i f i c a n t V i s i t s X G r o u p s , ( 1 , 63) = 4 . 3 8 , £ < .0404 i n t e r a c t i o n i n d i c a t e d t h a t h i g h h e a r t r a t e r e a c t o r s showed a g r e a t e r - 104 -d e c r e a s e i n d i a s t o l i c p r e s s u r e a c r o s s v i s i t s . The mean d i a s t o l i c p r e s s u r e was 78 and 71 mm Hg f o r h i g h r e a c t o r s and 70 and 68 mm Hg f o r l ow r e a c t o r s d u r i n g v i s i t s 1 and 2 r e s p e c t i v e l y . S c h e f f e ' s t e s t s o f c e l l means a d j u s t e d f o r age and b a s e l i n e f ound no s i g n i f i c a n t be tween-g roup d i f f e r e n c e s i n d i a s t o l i c p r e s s u r e d u r i n g t h e f i n a l 2 m i n u t e s o f t h e l a s t s t r e s s t a s k f o r s u b j e c t s i n t h e r e p e a t e d e x p o s u r e c o n d i t i o n . These S c h e f f e v a l u e s a r e d i s p l a y e d i n A p p e n d i x 19 . V i s i t 2 ANCOVA. The v i s i t 2 ANCOVA i n c l u d e d c o n d i t i o n s and r e a c t i v i t y a s be tween-g roup f a c t o r s , and T r i a l s and M i n u t e s as r e p e a t e d m e a s u r e s . The summary ANCOVA i s p r e s e n t e d i n Append i x 1 7 . S i g n i f i c a n t ma in e f f e c t s were f ound f o r g r o u p s , F ( l , 62) = 1 2 . 3 8 , £ < . 0 0 0 8 , and t r i a l s , F ( 2 , 127) = 1 4 . 5 0 , £ < . 0 0 0 0 , e = . 9 7 7 . The b a s e l i n e c o v a r i a t e was s i g n i f i c a n t l y r e l a t e d t o t h e Groups ma in e f f e c t , F ( l , 62) = 2 9 4 . 9 0 , £ < . 0001 ) and t o t h e T r i a l s ( l i n e a r ) , F ( l , 63) = 1 2 . 9 7 , £ < . 0 0 0 6 , and T r i a l s ( q u a d r a t i c ) , F ( l , 63) = 5 . 4 6 , £ < . 0 2 2 6 , t r e n d e f f e c t s . The ma in e f f e c t s f o r C o n d i t i o n s and M i n u t e s were no t s i g n i f i c a n t . D i a s t o l i c p r e s s u r e l e v e l s d u r i n g v i s i t 2 were h i g h e r among t he h i g h h e a r t r a t e r e a c t o r s . Newman-Keuls t e s t s i n d i c a t e d s i g n i f i c a n t d e c r e a s e s i n d i a s t o l i c p r e s s u r e f r om t r i a l s 1 t o 2 , q ( 1 2 7 ) = 3 . 6 6 , jr = 2, and f r om t r i a l s 2 t o 3 , Q;(127) = 7 . 0 7 , r_ = 2, £ < .05' . D i a s t o l i c p r e s s u r e was h i g h e s t d u r i n g t h e f i r s t t r i a l . ' A s i g n i f i c a n t q u a d r a t i c t r e n d was f ound f o r t h e M i n u t e s e f f e c t , _F(1, 64) = 4 . 0 0 , £ < . 0 4 9 7 . I n s p e c t i o n o f F i g u r e 17 r e v e a l s t h a t w i t h t h e e x c e p t i o n o f t h e c o n d i t i o n 2, l ow r e a c t o r g roup d i a s t o l i c p r e s s u r e was h i g h e s t d u r i n g t h e s e cond m i nu t e o f t h e s t r e s s t a s k p e r i o d i n V i s i t 2 . The s i g n i f i c a n t T r i a l s X M i n u t e s i n t e r a c t i o n , F_(4, 256) = 6 . 7 7 , £ < . 0 0 0 1 , e = . 8 8 0 , i n d i c a t e d t h a t t h e magn i t ude o f changes i n d i a s t o l i c p r e s s u r e a c r o s s m i n u t e s was i n v e r s e l y r e l a t e d t o t r i a l number. The r e a c t i v i t y g r oups v a r i a b l e showed s i g n i f i c a n t t h r e e - w a y i n t e r a c t i o n s 105 FIGURE 17. VISIT 2 DIASTOLIC PRESSURE CONDITIONS X MINUTES X GROUPS 70 n 68 H CT E E .£ 66-a: to to L d QC Q_ O 64H to < 62 H 60 J , 1 r 1 2 3 MINUTES Legend A CONDl/W HR REACTORS X CONDt/LO HR REACTORS • CON02/H1 HR REACTORS B COND2/L0 HR REACTORS 106 w i t h M i n u t e s X C o n d i t i o n s , F ( 2 , 128) = 3 . 8 3 , _p_ < . 0 2 7 9 , e = . 9 1 6 , and w i t h M i n u t e s ( l i n e a r ) X C o n d i t i o n s , F ( l , 64) = 5 . 1 9 , £ < . 0 2 6 0 . The G roups X C o n d i t i o n s X M i n u t e s i n t e r a c t i o n i s d i s p l a y e d i n F i g u r e 1 7 . Two t r e n d i n t e r a c t i o n s w h i c h were n o t r e l a t e d t o t h e p r e s e n t e x p e r i m e n t a l h y p o t h e s e s were f o u n d . These were T r i a l s ( q u a d r a t i c ) X M i n u t e s ( l i n e a r ) , F_(l, 64) = 1 1 . 5 5 , _p_ < . 0 0 1 2 , and T r i a l s ( q u a d r a t i c ) X M i n u t e s ( q u a d r a t i c ) X C o n d i t i o n s , F ( l , 64) = 4 . 4 3 , _p_ < . 0 3 9 3 . S c h e f f e ' s t e s t s were u sed t o make p a i r w i s e c o m p a r i s o n s o f b a s e l i n e a d j u s t e d c e l l means. H i g h and low r e a c t o r s i n b o t h c o n d i t i o n s showed no s i g n i f i c a n t d i f f e r e n c e s i n d i a s t o l i c p r e s s u r e d u r i n g t he f i n a l s t r e s s t a s k . The S c h e f f e v a l u e s a r e p r e s e n t e d i n Append i x 1 9 . Mean A r t e r i a l P r e s s u r e ANCOVAS. Th r ee a n a l y s e s o f c o v a r i a n c e o f mean a r t i e r i a l p r e s s u r e (MAP) were compu ted . The summary ANCOVA t a b l e s f o r t h e C o n d i t i o n 1, Task 1, and V i s i t 2 ANCOVAs a r e p r e s e n t e d i n A p p e n d i c e s 2 0 , 2 1 , and 2 2 , r e s p e c t i v e l y . C a r d i o v a s c u l a r r e a c t i v i t y was d e f i n e d i n t e rms o f h e a r t r a t e changes f r om b a s e l i n e t o t h e f i r s t s t r e s s t a s k i n t h e i n i t i a l e x p e r i m e n t a l s e s s i o n . The d a t a r e p r e s e n t e d i n t h e s e a n a l y s e s a r e p r e s e n t e d i n F i g u r e s 1 0 , 11 and 1 2 . C o n d i t i o n 1 ANCOVA. The a n a l y s i s o f c o v a r i a n c e a p p l i e d t o t h e c o n d i t i o n 1 ( r e p e a t e d e x p o s u r e ) MAP d a t a y i e l d e d s i g n i f i c a n t ma in e f f e c t s f o r G r o u p s , F_(l, 31) = 1 1 . 5 7 , £ < . 0 0 1 9 , V i s i t s , F ( l , 32) = 2 9 . 0 8 , £ < . 0 0 0 1 , T r i a l s , F ( 2 , 65) = 1 9 . 5 9 , £ < . 0 0 0 1 , e = . 9 5 3 , and M i n u t e s , F ( 2 , 66 ) = 4 . 7 0 , £ < . 0 1 5 1 , e = . 0 9 0 . P r e - t a s k b a s e l i n e MAP was s i g n i f i c a n t l y r e l a t e d t o t h e g r oup s ma in e f f e c t , F ( l , 32) = 8 . 0 4 , £ < . 0 0 7 9 . MAP was h i g h e r d u r i n g v i s i t 1. H i g h h e a r t r a t e r e a c t o r s d i s p l a y e d h i g h e r MAP l e v e l s t h a n l ow r e a c t o r s . A t r e n d a n a l y s i s o f t h e t r i a l s ma in e f f e c t y i e l d e d s i g n i f i c a n t l i n e a r , F ( l , 32) = 1 1 . 1 7 , £ < . 0 0 2 1 , and q u a d r a t i c t r e n d s , F ( l , 32) = 5 . 5 7 , £ < FIGURE 11 TASK I MEAN ARTERIAL PRESSURE 110-1 105-VISIT I cn sz E E 100 A ZD 00 to £ 95-Q_ _ l < OH DC < z < L d 2 90H 85 H I-B7 4 WK. INTERVAL Legend 1 •HraHRREKTORS/XTOM 3 •UJWHRIEAaOR^OMJVVl 4 •IXWf«REAQClMXK3yV2 5 •HPHWREACTOR^XKI^Vl 6 •HPHHRHDOOR^ OMX^ fl 7 •bOWHRRDCTJRVCCNI&'Vl 8 »L0yHRHE*CTO5>tCHgA2 8 0 -V1/FIRST TASK V2/FIRST TASK FIGURE 12 VISIT 2 MEAN ARTERIAL PRESSURE DATA 100-< < Ixl 11 80- 9 0 / 6 X ' 1 2 a-x,-- a Legend . 95 cn JO 1 •HmHHRaacRs<xMynMu E 3 -HmHRREACcRsyteMVims £ / 4-UJWWR£AqCR5/XHVIRW QJ g 0 - / ^  5 •IQWKRRETOCRS/XXVTBWt^  cc 0_ 2 ^ / > s ^ _ 8-HD<HRIC»CIOi5>eCNPViat2 9 *t^J*J¥^9!5$?$B^!!*y < 1 0 ^ \ 8 ® 10-UWHRR£ACCT5/CQCyWIU g 8 5 - \ 5 O \ P 11 •WHRRDCTOS/XNXyffiWJZ 12 • lOW HR RDOCRS/<X>Bg/TRHl3 "109 " . 0 2 4 5 . Newman-Keuls t e s t s i n d i c a t e d s i g n i f i c a n t d e c r e a s e s i n MAP f r om t r i a l 1 t o t r i a l 2 , q ( 3 2 ) = 5 . 2 5 , r_ = 2, JJ < . 0 5 . D e c r e a s e s f r om t r i a l s 2 t o 3 were n o t s i g n i f i c a n t . S i g n i f i c a n t l i n e a r , F ( l , 33) = 4 . 5 5 , JJ_ < . 0 4 0 5 , and q u a d r a t i c , F_( l , 33) = 4 . 9 8 , JJ < .05 t r e n d s were a l s o f ound f o r t h e M i n u t e s e f f e c t . MAP was h i g h e s t d u r i n g m i nu t e 2 o f t h e t a s k p e r i o d . I n c r e a s e s i n MAP f r om m i n u t e 1 t o m i n u t e 2 were no t s i g n i f i c a n t . D e c r e a s e s f r om m i n u t e s 2 t o 3 were a l s o n o t s i g n i f i c a n t . The r e s u l t s o f t h e Newman-Keuls t e s t s a r e d i s p l a y e d i n Append i x 2 3 . The Groups X V i s i t s , F ( l , 32) = 9 . 8 1 , JJ < . 0 0 3 7 , i n t e r a c t i o n was s i g n i f i c a n t . H i g h h e a r t r a t e r e a c t o r s d i s p l a y e d a c r o s s - v i s i t s means o f 95 and 87 mm Hg . Low r e a c t o r s showed a c r o s s - v i s i t s MAP means o f 85 and 83 mm Hg . Q These means show t h a t h i g h h e a r t r a t e r e a c t o r s d i s p l a y a g r e a t e r d e c r e a s e i n MAP a c r o s s v i s i t s . H i g h v e r s u s l ow h e a r t r a t e r e a c t o r s showed no d i f f e r e n c e s i n MAP a c r o s s s h o r t v e r s u s l o n g i n t e r - s t r e s s o r i n t e r v a l s . S e v e r a l s i g n i f i c a n t t r e n d i n t e r a c t i o n s were n o t o f p r i m a r y i n t e r e s t . These were V i s i t ( l i n e a r ) X T r i a l s ( l i n e a r ) F ( l , 32) = 1 0 . 4 7 , £ < . 0 0 2 8 , V i s i t s ( l i n e a r ) X T r i a l s ( q u a d r a t i c , F ( l , 32) = 4 . 2 8 , £ < . 0 4 6 8 , T r i a l s ( l i n e a r ) X M i n u t e s ( q u a d r a t i c , F ( l , 33) = 5 . 1 2 , £ < . 0 3 0 3 , and V i s i t s ( l i n e a r ) X T r i a l s ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 33) = 4 . 3 5 , £ < . 0 4 4 8 . S c h e f f e ' s t e s t s o f b a s e l i n e a d j u s t e d c e l l means i n d i c a t e d t h a t t h e h i g h and l ow r e a c t o r g r oup s d i d no t d i f f e r i n MAP d u r i n g t he f i n a l m i n u t e o f t h e f i n a l s t r e s s t a s k . These r e s u l t s a r e d i s p l a y e d i n Append i x 2 4 . Ta sk 1 ANCOVA. The Task 1 ANCOVA i n v o l v e d c o n d i t i o n s and r e a c t i v i t y g r oup s as between g roup f a c t o r s , and V i s i t s and M i n u t e s as r e p e a t e d m e a s u r e s . The summary ANCOVA t a b l e i s p r e s e n t e d i n Append i x 2 1 . The M i n u t e s v a r i a b l e , was based on MAP r e a d i n g s t a k e n d u r i n g t he f i r s t s t r e s s t a s k i n each v i s i t . S i g n i f i c a n t ma in e f f e c t s were f o und f o r c o n d i t i o n s , F_(l , 62) = 4 . 9 7 , £ < - no -. 0 2 9 4 , r e a c t i v i t y g r o u p s , F ( l , 62) = 3 9 . 8 8 , £ < . 0 0 0 1 , V i s i t s , F ( l , 63) = 3 7 . 0 7 , _p_ < . 0 0 0 1 , and M i n u t e s , F ( 2 , 128) = 5 . 7 0 , _p_ < . 0 0 5 4 , e = . 9 2 0 . B a s e l i n e MAP was s i g n i f i c a n t l y r e l a t e d t o t h e c o n d i t i o n s and g r oup s ma in e f f e c t s , ' F ( l , 62) = 4 4 . 6 4 , £ < .0001 and t h e V i s i t s ma in e f f e c t , F ( l , 63) = 4 . 7 2 , £ < . 0 3 3 6 . MAP was h i g h e r i n b o t h t h e s i n g l e e xpo su r e c o n d i t i o n and t h e f i r s t v i s i t . H i g h h e a r t r a t e r e a c t o r s a l s o d i s p l a y e d h i g h e r MAP v a l u e s . A t r e n d a n a l y s i s o f t h e M i n u t e s ma in e f f e c t y i e l d e d a s i g n i f i c a n t q u a d r a t i c t r e n d , F ( l , 64 ) = 1 2 . 5 0 , £ < . 0 0 0 8 . MAP was h i g h e s t d u r i n g t h e second m i nu t e o f t h e s t r e s s t a s k p e r i o d . I n c r e a s e s i n MAP f r om m i n u t e 1 t o m i n u t e 2, q ( 6 4 ) = 2 . 8 7 , r = 2, £ < . 0 5 , were s i g n i f i c a n t w h i l e d e c r e a s e s f r om m i n u t e s 2 t o 3 were n o t s i g n i f i c a n t . The V i s i t s X G r o u p s , F ( l , 63) = 9 . 1 2 , £ < .0037 i n t e r a c t i o n was s i g n i f i c a n t . H i g h h e a r t r a t e r e a c t o r s showed g r e a t e r d e c r e a s e s i n MAP a c r o s s v i s i t s . The a c r o s s v i s i t MAP means were 97 and 90 mm Hg f o r h i g h r e a c t o r s and 87 a n d 0 8 5 mm Hg f o r l ow r e a c t o r s . S i g n i f i c a n t G roups X C o n d i t i o n s X M i n u t e s , F ( 2 , 128) = 4 . 4 3 , £ < . 0 1 6 3 , e = .920 and Groups X C o n d i t i o n s X M i n u t e s ( l i n e a r ) , F_(l, 64) = 6 . 8 0 , £ < . 0 114 , i n t e r a c t i o n s were a l s o f o u n d . The Groups X C o n d i t i o n s X M i n u t e s i n t e r a c t i o n i s d i s p l a y e d i n F i g u r e 1 8 . The be tween -g roup d i f f e r e n c e s i n MAP a c r o s s m i n u t e s were g r e a t e s t i n t h e r e p e a t e d e x p o s u r e c o n d i t i o n . S c h e f f e ' s t e s t s were u sed t o compare b a s e l i n e - a d j u s t e d c e l l s means. S i g n i f i c a n t between g roup d i f f e r e n c e s i n MAP r ema i ned d u r i n g t h e f i n a l m i nu t e o f Task 1 i n t h e s e cond v i s i t . V i s i t 2 ANCOVA. The v i s i t 2 MAP ANCOVA i n v o l v e d c o n d i t i o n s and r e a c t i v i t y g r oups a s be tween -g roup v a r i a b l e s and t r i a l s and m i n u t e s as r e p e a t e d m e a s u r e s . The summary ANCOVA i s p r e s e n t e d i n Append i x 2 2 . S i g n i f i c a n t ma in e f f e c t s were f ound f o r t h e G r o u p s , F ( l , 62 ) = 9 . 8 3 , £ < . 0 0 2 6 , and T r i a l s , I l l FIGURE 18. TASK 1 MEAN ARTERIAL PRESSURE CONDITIONS X MINUTES X GROUPS 100 T CT E E oc z> CO CO UI oc Q . < oc UI I— oc < 95 H 90 H 8 5 H 8 0 - T ~T~ Legend A COMD t/HI HR REACTORS X COHD VLO HR REACTORS • COUP 3/HI HR REACTORS B COHD 2AjQ HR REACTORS 1 2 3 MINUTES 112 F ( 2 , 127) = 5 . 0 4 , £ < . 0 0 8 9 , e = .951 v a r i a b l e s . The ma in e f f e c t s f o r C o n d i t i o n s and M i n u t e s were n o t s i g n i f i c a n t . P r e - t a s k b a s e l i n e was a s i g n i f i c a n t c o v a r i a t e o f t h e g r oup s v a r i a b l e , F_(l, 62) = 1 5 8 . 6 6 , £ < . 0 0 0 1 , and t h e l i n e a r , F ( l , 63) = 1 5 . 7 , _p_ < .0002 and q u a d r a t i c , F ( l , 63) = 1 7 . 4 6 , £ < .0001 t r e n d s o f t h e t r i a l s v a r i a b l e . Newman-Keuls t e s t s i n d i c a t e d s i g n i f i c a n t , q ( 127 ) = 3 . 2 5 , r_ = 2, d e c r e a s e s i n MAP f r om t r i a l 1 t o t r i a l 2 , and f r om t r i a l 2 t o t r i a l 3 , q ( 1 2 7 ) = 4 . 9 2 , r_ = 2 , _p_ < . 0 5 . These r e s u l t s a r e d i s p l a y e d i n Append i x 2 3 . Two s i g n i f i c a n t i n t e r a c t i o n s were f o u n d . These were T r i a l s X M i n u t e s , _F(4, 256) = 4 . 1 3 , £ < . 0 0 3 3 , e = . 9 6 2 , and M i n u t e s ( l i n e a r ) X Groups X C o n d i t i o n s , F ( l , 64) - 5 . 1 5 , £ < . 0 2 6 6 . D e c r e a s e s i n MAP a c r o s s m i n u t e s v a r i e d i n v e r s e l y a s a f u n c t i o n o f t h e number o f t r i a l s . I n a d d i t i o n , two t r e n d i n t e r a c t i o n s w h i c h were n o t o f p r i m a r y i n t e r e s t were f ound t o be s i g n i f i c a n t . These were T r i a l ( l i n e a r ) X M i n u t e s ( l i n e a r ) , F ( l , 64) = 7 . 5 3 , £ < . 0 0 7 9 , and T r i a l s ( l i n e a r ) X M i n u t e s ( q u a d r a t i c ) , F ( l , 64) = 6 . 9 3 , £ < . 0 1 0 6 . S c h e f f e ' s t e s t were emp loyed t o compare c e l l means. H i g h and low r e a c t o r s i n t h e r e p e a t e d s t r e s s o r c o n d i t i o n s showed no s i g n i f i c a n t d i f f e r e n c e i n MAP d u r i n g t h e f i n a l m i n u t e o f t h e f i n a l s t r e s s t a s k . The S c h e f f e v a l u e s a r e d i s p l a y e d i n Append i x 24 . Summary o f ANCOVA E f f e c t s . As p r e v i o u s l y n o t e d , t h r e e a n a l y s e s o f c o v a r i a n c e were computed f o r ea ch o f t h e f o u r dependent m e a s u r e s . An o v e r a l l summary o f t h e s i g n i f i c a n t ANCOVA t e rms i s p r e s e n t e d i n T a b l e 1 5 . The ma in e f f e c t s , t r e n d e f f e c t s , and i n t e r a c t i o n s i n v o l v i n g t h e r e a c t i v i t y g r oups v a r i a b l e a r e summar i zed i n t h e f o l l o w i n g s e c t i o n . The e x p e r i m e n t a l c o n d i t i o n s v a r i a b l e , i . e , r e p e a t e d e x p o s u r e v e r s u s s i n g l e e x p o s u r e showed a s i g n i f i c a n t ma in e f f e c t on h e a r t r a t e d u r i n g v i s i t 2 and on DBP and MAP d u r i n g Ta sk 1. The r e a c t i v i t y g r oups v a r i a b l e was s i g n i f i c a n t on - 113 -TABLE 15 Summary o f C o n d i t i o n 1, Task 1 and V i s i t 2 ANCOVA E f f e c t s Dependent Measure E f f e c t HR SBP DBP MAP c o n d i t i o n s ( c ) V2 T l T l g r oups ( g ) C 1 . T 1 . V 2 C 1 . T 1 . V 2 C 1 . T 1 . V 2 C l . T l v i s t C l . T l C l . T l C l . T l C l . T l t r i a l s ( t ) C1 .V2 C1 .V2 V2 C1 .V2 m i n u t e s (m) C 1 . T 1 . V 2 C 1 . T 1 . V 2 C l C l . T l t ( l i n ) C l C l C l C l t ( q u a d ) C l C l C l C l m ( l i n ) C 1 , T 1 , V 2 T l C l m(quad) C l C 1 . T 1 . V 2 C 1 , T 1 , V 2 C l . T l c x g v x g C l . T l C l . T l C1 , T1 C l . T l g x t C l g x m C 1 , T 1 , V 2 T l b a s e l i n e C l C l C l V x t C l C l C l V x t x g C l v x m C l . T l t x m C1 .V2 C1 .V2 V2 t x m x g V2 C l v x c X T l m x c x g V2 t x m x c V2 T1 .V2 C l T l V2 = C o n d i t i o n 1 ANCOVA = Ta sk 1 ANCOVA = V i s i t 2 ANCOVA - 114 " measures of HR, SBP, DBP, and MAP for each of the three sets of analyses of covariance. The Vi s i t s repeated measure was significant for each of the four dependent measures in both the Condition 1 and Task 1 ANCOVAs. Similar effects were found for the Tr ia l s variable. Heart rate and SBP measures showed significant Minutes effects for each analysis of covariance. DBP and MAP showed a Minutes effect during the Condition 1 ANCOVA. Significant l inear and quadratic trends were found for the T r i a l s variable for each of the four cardiovascular dependent measures during the Condition 1 ANCOVA. The Minutes variable displayed a l inear trend for heart rate across analyses, and a significant quadratic trend for SBP, DBP and MAP during each analysis. A significant Vis i t s X Groups interaction was found for each of the four dependent measures during each analysis. The Minutes X Groups interaction was significant for heart rate only during each analysis. A significant groups X t r i a l s interaction was found for heart rate in the repeated exposure condition. A l l other Tr ia l s X Groups and Conditions X Groups interactions were consistently non-significant. DISCUSSION The results of the present study indicate that heart rate and blood pressure responses to a repeated mental arithmetic plus noise stressor decrease both within and across experimental sessions. High systol ic and heart rate reactive, normotensive women displayed greater i n i t i a l react ivity and greater decreases in responsivity to the repeated stressor than did low reactors. Stress response levels in V i s i t 2 were only minimally different in subjects exposed to one versus three stress tasks in V i s i t 1. In general, measures of cardiovascular baseline react iv i ty , stress response and recovery levels were not correlated with psychological self-report measures of stress - 115 -task perceptions. The age of the subject was s ignif icantly related to diastol ic blood pressure levels during post stress recovery periods. Aerobic fitness and level of physical act iv i ty were correlated with heart rate act iv i ty levels through a l l phases of the study. The experimental results and their significance with respect to the present experimental hypotheses are discussed in the following sections. F i r s t , relevant subject characteristics and the composition of the cardiovascular react ivity groups are reviewed. Second, the nature of the cardiovascular baseline, react iv i ty , stress response and recovery values and their intercorrelations are discussed. Third, the descriptive characteristics of the self-report measures and the correlations between the cardiovascular response measures and task perceptions are presented. Fourth, the results of the analyses of covariance, trend analyses, and post-hoc tests for each of the Condition 1, Task 1 and V i s i t 2 types of ANCOVAs are discussed. F ina l ly , a summary of the major conclusions pertaining to each experimental hypothesis and suggestions regarding future research are presented. Subject Characteristics and Reactivity Groups Ninety, normotensive female subjects participated in the present study. The mean resting blood pressure levels for the present sample were s l ight ly lower than blood pressure norms for women of similar age. Given the resting blood pressure levels, age (17-45 yrs . ) and weight (86-170 lbs . ) of the subjects involved i t can be assumed that the present sample i s representative of a normal, healthy female population. This is further strengthened by the fact that subjects with a previous history of cardiovascular problems or with current use of cardioactive medications were excluded. The number of subjects who were menstruating and/or taking birth control p i l l s decreased s l ight ly from V i s i t 1 to V i s i t 2. Previous researchers - 116 -(Carrol l et a l . , 1984) have noted individual-specif ic levels of cardiovascular react ivity across menstrual cycles. This finding is supported by the results of the present study which found a significant amount of individual speci f ic i ty in heart rate react ivity and to a lesser extent in systol ic pressure react ivi ty across a single four-week menstrual cycle. The presence or absence of birth control medication and/or menstruation were not s ignif icantly correlated with react iv i ty , stress response or recovery levels . The apparent shift of a larger proportion of low react ivi ty subjects to the no birth control non-menstruation groups during V i s i t 2 warrants further research. Subjects in the present study reported a mean physical act iv i ty level of 7.1/10 and a mean self-perceived fitness level of 6.45/10. As expected the subjects' self-reported level of physical act iv i ty and self-perceived aerobic fitness level were s ignif icantly correlated. While previous authors (Hollander & Seraganian, 1984) have noted that aerobic fitness level was s ignif icantly correlated with post task heart rate recovery levels , the present study found that both fitness measures were s ignif icantly correlated with stress response and recovery heart rate values. Aerobic fitness was more strongly related to heart rate recovery than to stress response levels . The magnitude of these correlations increased with the number of stress tasks and recovery periods administered. Heart rate during the i n i t i a l stress task was not s ignif icantly correlated with the fitness measures. It appears that the magnitude of decreases in heart rate responsivity to repeated stress vary as a function of one's aerobic fitness l eve l . Given the nature of the fitness measures administered in the present study, these findings should be cautiously interpreted. The possible preventive effects of aerobic exercise on cardiovascular responses to psychological stress should however continue to be explored. The apparent lack of relationship between blood pressure - 117 -react ivity and aerobic fitness in response to a mental arithmetic stressor i s consistent with previous findings (Lake, Suarez, Schneiderman, & Tocci , 1985). As previously noted, subjects in the present study ranged in age from 17-45 years. It i s interesting to note that within a normotensive sample covering a relat ively limited age range (28 yrs . ) age was found to be s ignif icantly correlated with both stress response and recovery period blood pressure levels for subjects in the single stressor condition. The magnitude of these correlations was consistent across systo l ic , d ias to l i c , and mean a r t e r i a l pressure measures (r_ = ,40 to r = .62). During V i s i t 1 age was s ignif icantly correlated with recovery period blood pressure levels only for subjects in the repeated stressor condition. For subjects in the single stressor condition age was related to the magnitude of their stress task and recovery period blood pressure levels . During V i s i t 2 age was related to recovery but not to stress response levels . Diastol ic blood pressure levels of subjects in the repeated stressor condition were s ignif icantly correlated with age for recovery period values during V i s i t 2. These findings suggest several conclusions. F i r s t , blood pressure and heart rate responses to stress were not s imilarly affected by increases in age. No correlation between heart rate and age was found. Second, on an overall basis age was more s ignif icantly related to cardiovascular recovery from stress than to react ivi ty or the stress response leve l . Heart rate and systol ic react ivity were not s ignif icantly correlated with age. Third, the presence of significant correlations between age and diastol ic pressure during the f i r s t , second and third post-stress recovery periods in V i s i t 2 for subjects in the repeated stressor condition suggests that the effects of age on diastol ic responsivity may increase as the number of stressor repetitions increases. These findings just ify the use of age as a covariate in analyses of repeated - 118 -stressor effects as was done in the present study. The absence of significant correlations between heart rate, systol ic pressure and mean ar ter ia l pressure and age during post-stress recovery suggests that changes in peripheral resistance may mediate these interactions. Subjects were c lass i f ied as either high or low cardiovascular reactors on the basis of their change in heart rate and systol ic blood pressure. Subjects in the upper and lower terc i les of the distribution of reactivity scores were assigned to the high and low reactor groups. This procedure represents several improvements over previous studies. F i r s t , the present definit ion of change minimizes the effect of anticipatory arousal on stress response levels in that specif ic , pre-task instructions were not administered unt i l after the completion of the adaptation period. These instructions were then followed by a post-instruction, pre-task waiting period. The potential effect of differences in i n i t i a l values was further controlled in that values from the f ina l two minutes of the adaptation period were treated as a covariate in a l l subsequent analyses of cardiovascular data. Second, the inclusion of multiple measures of cardiovascular reactivity revealed a complete overlap of the high heart rate and high systol ic react iv i ty groups, and a 91% overlap of the low heart rate and low systol ic reactivity groups. Three subjects were c lass i f ied as low systol ic , high heart rate reactors. While previous authors (Manuck & Schaeffer, 1978; Manuck & Garland, 1980) have employed both heart rate and systol ic blood pressure as measures of react ivi ty the overlap between these two response dimensions was not assessed. This overlap in heart rate and systol ic pressure act iv i ty seems to reflect the common influence of sympathetic mediation of cardiovascular changes (Lacey & Lacey, 1966). A subsequent analysis of the correlation between reactivity to the f i r s t stress task in each of the two experimental sessions revealed a correlation of - 119 -.67 for heart rate and .32 for systol ic reactivity across v i s i t s . These correlations suggest that f i r s t v i s i t heart rate react ivi ty explains approximately four times as much of the variance in second v i s i t responses as does systol ic react iv i ty . Given the relative ease of measurement, low cost and apparent r e l i a b i l i t y of heart rate measures, i t appears that heart rate would be the measure of choice in analyses of cardiovascular react ivity to stress. The use of SBP react ivi ty as a c lass i f icat ion variable i s recommended for analysis of heart rate data only. Equal numbers of high and low heart rate and systol ic reactors were assigned to each of the two experimental conditions. The cut-off points for the high (>+27 bpm) and low (<+15 bpm) heart rate react ivity terc i les are similar to those reported in previous mental arithmetic paradigms (Linden et a l . , 1985). The wide range of heart rate reactivity in the present study i s of interest. The responses of subjects in the high reactor groups ranged from +27 to +67 beats per minute, while the responses of low reactors ranged from +15 to -3 bpm. Within the high reactor group one would argue that an increase of 67 beats may be more c l i n i c a l l y significant than one of 27 beats per minute. At the very least one i s struck by the var iab i l i ty in responses of a group already singled out as the upper terc i l e of the distribution of heart rate react ivi ty scores. The presence of extreme scores or outl iers within this group may affect the va l id i ty of between group analyses. During V i s i t 2 the distribution of HR react ivi ty was much more leptokurtic and positively skewed. This change in the shape of the distribution provides further evidence of the ins tab i l i ty of the upper end of the f i r s t v i s i t HR reactivity scores. The range of systol ic blood pressure react ivi ty in the present study requires similar attention. Previous authors have c lass i f ied individuals in - 120 -terms of blood pressure react ivity (Manuck & Schaeffer, 1978; Manuck & Garland, 1980). However, SBP react ivi ty has not previously been employed as a c lass i f icat ion variable in the analysis of heart rate data. The responses of subjects in the high systol ic react iv i ty group ranged from +18 mm Hg to +42 mm Hg. While the number of high SBP reactors decreased in the second session, the overall shape of the distribution of SBP react ivi ty did not change s ignif icantly across sessions. Numerous authors have provided evidence of fluctuations in systol ic blood pressure of up to 30 mm Hg during normal daily ac t iv i t i e s (Harshfield et a l . , 1982). Given such "normal" fluctuations in SBP i t may be d i f f i c u l t to argue that the magnitude of SBP responses shown by the high SBP reactors in the present study i s predictive of increased cardiovascular r i s k . The study of individuals who are both high reactors to laboratory-induced psychological stress and highly labi le during daily ac t iv i t i es may serve to reveal a better predictive l ink to heart disease. Cardiovascular Dependent Measures The means and standard deviations of the cardiovascular dependent measures and the correlations between baseline, stress response and reactivity levels are presented in Tables 6 and 11, respectively. As previously noted, the magnitude of heart rate and systol ic pressure responses observed are typical of responses to a mental arithmetic task (see Table 2). The fact that the mental arithmetic plus noise stressor produced approximately equal increases in SBP, DBP and MAP levels i s somewhat discrepant with the typical pattern of blood pressure responses associated with an active coping task (cf. Obrist , 1981). Obrist (1981) predicts smaller d iasto l ic than systol ic responses. Linden et a l . (in press) noted however that this difference may be attributable to Obrist 's use of a shock avoidance paradigm rather than mental arithmetic. - 121 -Inspection of the correlation between cardiovascular baseline measures within sessions revealed significant correlations (r_ = .67 to _r = .90) between each of the three pressure measures. These correlations provide evidence of stable, individual-specif ic baseline blood pressure levels . In contrast, heart rate baseline was s ignif icantly correlated with SBP and MAP baseline during V i s i t 2 only. This finding confirms the directional fractionation of HR and DBP measures and the relative independence of their control mechanisms. The magnitude of within-session stress task level correlations between the cardiovascular dependent measures i s typical of those reported elsewhere (Foerster et a l . , 1983). Blood pressure levels during the f i r s t stress task within each session were highly correlated. HR, SBP and MAP stress task levels were correlated during the f i r s t session only. These results are indicative of individual-specif ic effects on blood pressure stress response levels . The s imi lar i ty in magnitude of these correlations within each session reflects some relative s tabi l i ty of blood pressure control mechanisms. The absence of a significant correlation between HR, SBP and MAP levels during the f i r s t task in V i s i t 2 however suggests a lack of response s tab i l i ty which may be due to differences in habituation of heart rate and blood pressure across the two sessions. An analysis of the across session baseline, stress response and react ivi ty levels i s presented in Table 11. Baseline measures were stable across the four-week interval for each of the four dependent measures (_r = .63). Responses to the f i r s t task were also consistent (r = .70). These findings are supportive of those of previous researchers (Lacey & Lacey, 1966; Manuck & Schaeffer, 1978; Manuck & Garland, 1980) who noted that subjects displayed relat ively stable, idiosyncratical ly determined cardiovascular response levels during psychological stress. As previously noted, heart rate react ivity (r_ = - 122 -.66) proved to be more rel iable than systol ic reactivity (r = .32) as a measure of stable across session cardiovascular react iv i ty . DBP and MAP react ivi ty were not s ignif icantly correlated across sessions. Manuck and Garland (1980) also found ins tab i l i ty of DBP reactivity across a similar time interval suggesting the involvement of different or more complex control mechanisms. Self-Report Measures The mean scores for ratings of perceived stress (PS), perceived performance (PP), perceived task d i f f i cu l ty (PD), and perceived importance of the task (PI) ref lect the fact that on average subjects perceived the mental arithmetic plus noise stressor to be important, stressful and d i f f i c u l t . During the second v i s i t ratings of PP and PI increased while ratings of PS and PD decreased. While these changes were not s ta t i s t i ca l l y significant they do suggest the possible presence of practice effects and changes in task appraisal across sessions. The lack of correlation between psychological self-report and cardiovascular response measures i s consistent with reports elsewhere (Linden, in press; Linden et a l . , in press). In the present study only heart rate react ivity and recovery rate were correlated with PI and PP, respectively in V i s i t 2. Subjects who appraised the task to be more important were more highly reactive. Linden et a l . ( in press) suggested that the academic-like nature of a mental arithmetic task may serve to influence perceptions of task performance and importance in some subjects. The results of the present study suggest that HR recovery from repeated stress i s influenced by one's perception of task performance such that self-perceptions of poor performance delay heart rate recovery. Such delay in heart rate recovery i f chronic may lead to potentially pathogenic insult to the cardiovascular system. - 123=-Condition 1 ANCOVAs The results of the Condition 1 (repeated exposure) ANCOVA for each of the four cardiovascular dependent measures are discussed in the following section. The average heart rate and SBP levels displayed by" the high systol ic and high heart rate reactors were consistently higher than those of low reactors across v i s i t s , t r i a l s and minutes within Condition 1. Significant v i s i t s X groups, t r i a l s X groups and minutes X groups interactions also indicated that high systolic reactors showed greater decreases in HR across each of the repeated measures. It is important to note that differences were independent of i n i t i a l response levels in that baseline measures were treated as a covariate in a l l analyses. High systol ic reactors appear to be more sympathetically labi le than do low reactors. The blood pressure X HR reactivity interactions are less consistent. The v i s i t s X groups interaction on each of the three pressure measures indicated that high HR reactors displayed greater decreases in blood pressure across the four-week i n t e r - v i s i t interval . The absence of significant t r i a l s X groups or minutes X groups interactions suggests that changes in blood pressure occur more slowly than do changes in heart rate. The time span involved in a given experimental session may not have been sufficient for between group differences in blood pressure to become evident. Each of the four dependent measures showed significant Tr ia l s ( l inear) and Tr ia l s (quadratic) effects. While Figures 1, 4, 7 and 10 indicate that decreases in cardiovascular responsivity across Tr ia l s are primarily l inear in nature, the significant quadratic trend indicates that heart rate and blood pressure show the greatest decreases from t r i a l 1 to t r i a l 2. This result i s supported by the results of the Newman-Keuls test between levels of the t r i a l s variable. Heart rate displayed similar linear and quadratic trends with _ 124 _ respect to the minutes variable. The greatest decreases in heart rate occurred from minute 1 to minute 2 within a given t r i a l . The trend analysis of the blood pressure data across minutes revealed a significant quadratic trend. Blood pressure levels were generally highest during the second minute of each task. These results provide further evidence of the slower-changing nature of blood pressure responses. Task-induced arousal did not become evident unt i l the second minute of each task period. Scheffe's tests indicated that high and low HR reactors differed only in terms of SBP during the f ina l minute of the f ina l task. No differences in DBP or MAP were found. High and low SBP reactors did not differ in heart rate during the f ina l minute. It appears that between group differences in HR, DBP and MAP disappear over the presentation of six stressor t r i a l s . The use of cardiovascular reactivity as a c lass i f icat ion measure in the analysis of cardiovascular responses to a repeated stressor may be confounded by the greater habituation of responses in the high reactor groups. Task 1 ANCOVAs The results of the Task 1 (Conditions X Groups X Vis i t s X Minutes) ANCOVAs for HR, SBP, DBP and MAP measures are discussed in the following section. The Task 1 ANCOVAs yielded main effects for groups, v i s i t s and t r i a l s similar to those in the Condition 1 ANCOVA for HR, SBP and MAP measures. The minutes effect displayed a similar linear trend for HR and quadratic trend for blood pressure measures. Several results were unique to the Task 1 analyses. The repeated versus single exposure conditions variable yielded main effects on measures of DBP and MAP such that responses were lower in the repeated stressor condition. HR and SBP measures taken during the f i r s t task in the second v i s i t were not affected by varying amounts of prior exposure to the stressor. These results suggest that HR and SBP outcome measures ~ 125 " involving the single presentation of a psychological stressor in each of two sessions w i l l not provide evidence of the potential effects of prior exposure to the stressor. V i s i t 2 ANCOVAs The results of the V i s i t 2 (conditions X groups X t r i a l s X minutes) ANCOVAs are discussed in the following section. The V i s i t 2 ANCOVAs yielded main effects for groups, t r i a l s and minutes for HR and SBP similar to those in the Condition 1 analyses. DBP and MAP showed main effects for groups and t r i a l s only. Within V i s i t 2 the condition variable yielded a main effect for HR only. Heart rate was lower in those subjects who had undergone repeated stress tasks in V i s i t 1. The absence of a conditions effects on blood pressure measures suggests that habituation of blood pressure measures across a four-week interval i s more resistant to the effect of varying exposure to the stress task. No significant l inear or quadratic trends were found for the t r i a l s effect within V i s i t 2. Blood pressure responses yielded significant minutes (quadratic) trend effects. The absence of significant t r i a l trends suggests that as the number of stressor t r i a l s increases the patterns of habituation of HR and blood pressure responses becomes more variable. A comparison of high versus low reactors during the f ina l minute of the f ina l task in V i s i t 2 showed no differences in HR, DBP and MAP for subjects in the repeated stressor condition. Between group differences remained in the single task condition. Between group differences in SBP remained for subjects in both conditions. As previously noted, the lack of re l iable between group differences after re lat ively few stress tasks presents problems for the uncr i t i ca l use of cardiovascular reactivity as a c lass i f icat ion variable. - 126 ~ Major Conclusions and Recommendations The aforementioned experimental hypotheses and major conclusions regarding each hypothesis are l i s ted in the following section. In addition, outstanding issues and recommendations regarding future research are discussed. F i r s t , i t was hypothesized that both heart rate and blood pressure would decrease within and across experimental sessions. The highly significant (_p_ < .001) main effects for v i s i t s , t r i a l s and minutes on each of the four dependent measures provides strong support for this hypothesis. Second, i t was hypothesized that high reactors would show greater decreases in heart rate and blood pressure than low reactors across levels of the repeated measures. The most rel iable effect was the significant v i s i t s X groups interaction which indicated that high reactors showed greater decreases across v i s i t s on each of the four cardiovascular dependent measures. A groups X t r i a l s effects was found for HR only in the repeated stressor condition. A groups X minutes effects was also found for a l l HR ANCOVAs. Between group differences in blood pressure were mot evident on a within-session basis. It was also hypothesized that repeated exposure to the stressor would fac i l i t a t e cardiovascular habituation. No support for this hypothesis was found in that one-way interactions between the conditions variables and the repeated measures were non-significant. There was part ia l support for the hypothesis that repeated exposure would have a greater effect on the high reactivity groups. Significant conditions X v i s i t s X groups and conditions X minutes X groups interactions were found for HR in the Task 1 ANCOVA and for DBP in V i s i t 2, respectively. High reactors showed greater decreases in heart rate during the f i r s t task across v i s i t s in the repeated stressor condition. They also displayed greater decreases in DBP across minutes of the f i r s t task in V i s i t 2, Condition 1. - 1 2 7 -The results of the present study indicate that highly reactive subjects show the greatest decreases in cardiovascular response levels . Bohlin (1973) in a review of factors influencing cardiovascular habituation, had concluded that increases in arousal produce a corresponding delay in physiological habituation. It appears that the level of arousal produced by the present stressor was not sufficient to produce a delay in response habituation. High reactors were generally more labi le than low reactor throughout a l l phases of the experimental sessions. Acute react ivity to an i n i t i a l stress task may represent only one facet of an overall pattern of increased cardiovascular l a b i l i t y . The hypothesized significant negative correlation between cardiovascular habituation and length of inter-stressor interval was found for each of the dependent measures. The effect was strongest for HR data. The delayed impact of the stressor on blood pressure responses complicated the interpretation of blood pressure data with respect to this hypothesis. It was also hypothesized that repeated exposure to the stressor would produce a greater decrease in the i n i t i a l level of HR and SBP react ivi ty during the second session. HR and SBP reactivity to the f i r s t stress task in v i s i t 2 were only s l ight ly lower for subjects in the repeated stressor condition (-2.2 beats per minute; -0.80 mm Hg). These differences were not s ta t i s t i ca l l y s ignif icant. The hypothesis of an overlap in the groups formed by measures of HR and SBP reactivity was strongly supported. The present evidence also suggests that HR react ivi ty i s a more re l iable across-session c lass i f icat ion variable. Limited evidence was found in support of the hypothesized relationship between cardiovascular react ivi ty and task perceptions. Perceived performance during V i s i t 2 was negatively correlated with HR recovery levels; while HR reactivity - 1 2 8 -was negatively correlated with perceived task importance. No relationship was found between blood pressure responses and self-report measures of subjects' task perceptions. The present study included several methodological improvements and additions to previous studies. These included: a) the use of a female population. b) the inclusion and comparison of different inter-stressor intervals . c) the inclusion and comparison of repeated versus single stress tasks. d) the use of multiple dependent measures. e) a comparison of HR versus SBP react iv i ty . f) the treatment of age and baseline as covariates. g) the use of a definition of cardiovascular change which accommodates both the problem of i n i t i a l values and the problem of anticipatory arousal. h) i t controls for the possible effects of caffeine, alcohol, tobacco, exercise, age, aerobic fitness, menstruation, and birth control or cardioactive medications on response levels . i ) i t provides an analysis of the relationship between acute cardiovascular react ivi ty and subsequent response habituation. The results of the present study clearly support the majority of the experimental hypotheses. However they also raise a number of potential questions for future research. Future researchers must continue to distinguish between the s ta t i s t i ca l and c l i n i c a l significance of cardiovascular responses to a given stressor. Given the large range and variance within the high HR reactor group, individuals at the upper and lower l imits of this group may be at different levels of cardiovascular r i sk . Other researchers (Manuck & Schaeffer, 1978; Manuck & Garland, 1980) have found a - 129 -different distribution of HR and SBP reactivity to a concept formation task among male subjects. These authors employed upper and lower terc i l e cut-off points of +13.4 bpm and +4.0 bpm for heart rate, and +20.1 mm Hg and +4.0 mm Hg for SBP react iv i ty . The upper terc i l e cut-off point for HR react ivi ty i s 14..beats lower than that employed in the present study. This difference in cut-off points may reflect the effects of gender or different tasks. The c l i n i c a l appropriateness of a given react ivity cr i ter ion remains an open question. Researchers should explore the predictive va l id i ty of various react ivi ty c r i t e r i a . They should also assess the potential benefits of simultaneously employing multiple response measures in their attempts to identify re l iab le , predictive react ivity groups. Krantz and Manuck (1984) concluded in a review of the l i terature that cardiovascular react ivi ty per se was not yet a proven risk factor. The results of the present study also indicate that react ivi ty group differences in response levels are not stable across repeated stress tasks. The question arises as to how acute react ivity can be predictive of long term risk when a relat ively mild, repeated experimental stressor eradicates between group differences in response levels . In the present study high versus low reactivity groups were not affected differently by single versus repeated exposure to the stress task. These results pose a question as to the role of necessary stressor frequency in the transduction of acute responses into chronic coronary pathology. Aerobic fitness level was correlated with HR recovery following repeated stress tasks in the present study. Age was related to DBP recovery values. Menstruation and birth control were linked to higher HR and SBP reactivity in the second experimental session. Each of these subject characteristics'should be further assessed as potential mediators of cardiovascular responsivity to - u n -s t r e s s . F i n a l l y , t h e p r e s e n t r e s u l t s i n d i c a t e t h a t s i g n i f i c a n t h a b i t u a t i o n o f c a r d i o v a s c u l a r r e s p o n s e s o c c u r s w i t h r e l a t i v e l y few s t r e s s o r p r e s e n t a t i o n s . H a b i t u a t i o n e f f e c t s a r e r e t a i n e d o v e r a f o u r - w e e k i n t e r v a l . P r e v i o u s r e s e a r c h e r s have emp loyed s t r e s s t a s k r e s p o n s e s as p r e - p o s t measures o f t r e a t m e n t e f f i c a c y . The o b s e r v e d h a b i t u a t i o n t o t h e e x p e r i m e n t a l s t r e s s t a s k may c on f ound a t t e m p t s t o o b s e r v e t h e e f f e c t s o f a t r e a t m e n t i n t e r v e n t i o n . D e c r e a s e d r e s p o n s e l e v e l s o b s e r v e d d u r i n g a p o s t - t r e a t m e n t s t r e s s t e s t may be m i s t a k e n l y l a b e l l e d as t r e a t m e n t e f f e c t s . The use o f c o n t r o l g r oup s wou l d a l l o w f o r c o m p a r i s o n o f c a r d i o v a s c u l a r changes i n t r e a t m e n t v e r s u s no t r e a t m e n t g r oup s ( M i n e r e t a l . , 1 9 8 4 ) . R e s e a r c h e r s a r e however s t i l l f a c e d w i t h t h e p r o b l e m o f i s o l a t i n g t r e a t m e n t v e r s u s h a b i t u a t i o n e f f e c t s w i t h i n a g i v e n t r e a t m e n t g r o u p . T h i s p r ob l em i s c o m p l i c a t e d by t h e f a c t t h a t i n d i v i d u a l s d i s p l a y s u b s t a n t i a l h a b i t u a t i o n o v e r t h e c o u r s e o f a s i n g l e s t r e s s t a s k . I n a d d i t i o n , r e s p o n s e s t o s ub sequen t n o v e l s t r e s s t a s k s a r e a l s o c o n s i s t e n t l y s m a l l e r i n magn i t ude ( V o s s e l & L a u x , 1977; L i n d e n , F r a n k i s h , & M c E a c h e r n , i n p r e s s ) . - 131 -References Abboud, F . M. (1976). Relaxation, autonomic control and hypertension. New England Journal of Medicine, 294, 107-109. Abboud, F . , Heistad, D. D . , mark, A. L . , & Schmid, P. G. (1976). Reflex control of the peripheral c irculat ion. 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Ergonomics, 16(1), 61-67. - 155 -APPENDIX 1 CONSENT FORM I , freely and voluntarily and without undue inducement or any element of force, fraud, deceit, or other form of constraint or coercion consent to be a participant in the research project entitled "Habituation and Cardiovascular Responses" to be conducted in the Cardiovascular Psychophysiology Laboratory in the Kenny Building for 2 experimental sessions each of a duration of 30 to 40 minutes with Dr. W. Linden as principal investigator. The procedures to be followed and their purposes, including identif icat ion of any procedures which are experimental, have been explained to me. As a understand i t , the study is concerned with the cardiovascular changes. In order to assist in obtaining this information, i t w i l l be necessary to undergo the following experiences: 1. Assignment at random to one of two treatment conditions: (a) single stress or (b) repeated stressor. The stressor w i l l be a mental arithmetic task. 2. Measurement of heart rate and blood pressure in the cardiovascular psychophysiology lab. During the session which w i l l last 30-40 minutes, I w i l l be connected to a non-invasive blood pressure monitor, completely non-dangerous, and only minimally discomforting. I understand that there are no foreseeable attendant risks in my participation in this project. I understand that I may refuse to participate or may withdraw at any time without influence on class standing. I also realize that a l l information obtained i s s t r i c t l y confidential . While findings may be used in future studies, there w i l l be no identi f icat ion of me personally on any permanent records. A l l information w i l l be reported in group form and w i l l remain s t r i c t l y anonymous. I have been given the right to ask and have received answers on any inquiry concerning the foregoing. Questions, i f any, have been answered to my satisfaction. I have read and understand the foregoing. I have received a copy of this consent form. Witness Research Participant - 156 -APPENDIX 2 MODIFIED PAR-Q (PHYSICAL ACTIVITY READINESS QUESTIONNAIRE) 1. Has your doctor ever said you have heart trouble? Yes No 2. Do you frequently suffer from pains in your heart or chest? Yes No 3. Do you feel faint or have spells of severe dizziness? Yes No 4. Has your doctor ever said your blood pressure was too high? Yes No 5. Have you ever taken medication for a heart problem? Yes No 6. Are you presently taking any medications? Yes No 7. Do you smoke? Yes No 8. Do you regularly engage in vigorous exercise? Yes No Reference: Par-Q Validation Report Br i t i sh Columbia Department of Health June 1975 (modified version) - 157 -APPENDIX 3 POST-STRESSOR QUESTIONNAIRE You have just completed the stressor phase. We would l ike to find out how you perceived the experience. Please c i rc l e on the following scales the number which best approximates your view. How do you rate your performance on the mental arithmetic in comparison to other people with your age and background? 1 2 3 4 5 6 7 8 9 a lot equal a lot worse better 2. How stressful did you find the mental arithmetic task? 1 2 3 4 5 6 7 8 9 10 not at very a l l much so 3. How d i f f i c u l t did you find the mental arithmetic task? • 1 2 3 4 5 6 7 8 9 10 not at very a l l much so 4. How much did your current mood influence your performance on the mental arithmetic task? 1 2 3 4 5 6 7 8 9 10 not at very a l l much so 5. How important was your performance on the mental arithmetic task? 1 2 3 4 5 6 7 8 9 10 not at very a l l much so - 158 -APPENDIX 4 EXPERIMENTAL SCRIPT INTRODUCTION H i , I'm and I ' l l be your experimenter for today. As I mentioned on the phone, we are interested in the physiological events during a 20-minute waiting period, and the events during a mental arithmetic task which i s f a i r l y easy in nature. I w i l l be asking you to perform the task (CHOOSE APPROPRIATE ONE) CONDITION 1: 3 times for 3 minutes each, with periods of rest in between CONDITION 2: For one 3-minute period During the 20-minute waiting period, I'd l ike you to f i l l out some questionnaires for me. The task w i l l be accompanied by 90 db of noise which you w i l l hear over this set of headphones. 90 db is the maximum level allowed by the Worker's Compensation Board for an 8-hour working day, so a few minutes w i l l not be harmful. During the experiment, I w i l l be in the room next door. There i s a one-way mirror behind you, but my primary concern is not to watch you. There is also an intercom so I ' l l be able to hear you i f you have any questions. During the experiment, you w i l l be wearing this blood pressure cuff. I t ' s similar to the one used in a doctor's off ice . Have you had your blood pressure taken before? This cuff automatically expands once every minute. During expansion i t may be rather uncomfortable but that discomfort w i l l go away within 20 seconds or so. The procedure i s safe, so you needn't be concerned. "Now I ' l l put the cuff on. Which hand do you write with? I ' l l put this on your other arm then. It 's important that you keep this hand s t i l l during the measurement. When the cuff i s pumping up, some people have an urge to wiggle their fingers around, but the instrument won't function properly i f you do. Please try to remain s t i l l and breathe normally throughout the experiment. For the next 20 minutes, I would l ike you to f i l l these out while I record your blood pressure and heart rate. The time period w i l l begin with the f i r s t expansion of the cuff. I ' l l come in and let you know when i t i s over. I ' l l also t e l l you how your f i r s t reading is over the intercom." STRESS TASK "This i s the end of the 20-minute period. "Next we'l l be doing the Mental Arithmetic Task. As I mentioned ear l ier , I would l ike you to: (CHOOSE APPROPRIATE ONE) CONDITION 1: Do the task three times for 3 minutes each with three minute resting periods in between. CONDITION 2: Do the task for three minutes and then I ' l l ask you to s i t quietly for fifteen minutes afterward. - 159 -"The task w i l l be accompanied by 90 db noise over this set of headphones and I ' l l be asking you to consecutively subtract numbers. I ' l l give you specific instructions in a moment, but f i r s t we' l l start with two minutes of readings to re-establish a resting leve l , and then I ' l l give you the instructions for the task over the set of headphones." "Can you hear me OK? For the mental arithmetic task, I would l ike you to continuously subtract aloud, beginning with the number 1,000. For example, you would say "1,000, 993, 986, 979, etc." Please do this as quickly as you can, and i f you get lost or confused please begin again at the number 1,000. I would l ike you to continue trying for the f u l l three minutes. Although you may not be able to hear yourself speaking, I would l ike you to speak clearly because I w i l l be l istening to your answers and rating your performance. You can begin as soon as you hear noise through the headphones." "OK, that's the end of the task." (CHOOSE APPROPRIATE ONE) CONDITION 1: Please s i t quietly for three minutes. I ' l l let you know when the time i s up, and then I ' l l ask you to do a similar task. CONDITION 2: Please s i t quietly for another fifteen minutes. AFTER FINAL THREE MINUTE RESTING PERIOD: (OR FIFTEEN MINUTE RESTING PERIOD FOR CONDITION 2) GIVE SUBJECT "POST STRESSOR" QUESTIONNAIRE "OK, here's a questionnaire that I'd l ike you to f i l l out. I ' l l return in a minute and t e l l you your results and a l i t t l e about the experiment." - 160 -APPENDIX 5 Condition I: Heart Rate ANCOVA Term F J2 < groups (9) 30.5A .0000 heart rate baseline (hbl) 54.48 .0000 age/dbl 28.15 .0000 v i s i t (v) 39.34 .0000 V x g 10.96 .0026 hbl 29.25 .0000 t ( l i n ) 13.06 .0012 t ( l in ) x g 8.53 .0068 t(quad) 8.99 .0056 t r i a l (t) 34.75 .0000 t x g 12.31 .0000 v( l in) x t ( l in ) 10.32 .0033 v( l in) x t ( l in ) x g 11.25 .0023 v( l in) x t(quad) x g 10.40 .0032 V x t 12.47 .0000 v x t x g 11.16 .0001 m(lin) 68.27 .0000 m(lin) x g 10.94 .0025 m(quad) 8.95 .0056 minutes (m) 52.56 .0000 m x g 8.21 .0007 v( l in) x m(lin) 12.15 .0016 v x m 7.09 .0018 t ( l i n ) x m(lin) 27.94 .0000 t x m Term(s) t r i a l s , t x g v x t , v x t x g minutes, m x g v x m t x m 11.65 .0000 Epsilon Factors .699 .747 .710 .844 .730 Greenhouse-Geisser corrected probability .0003 .0002 .0004 .0000 .0032 -.161 -Term groups h b l age/dbl (v) V X g V X C X g h b l m ( l i n ) m ( l i n ) x g minutes m x g v ( l i n ) x m ( l i n ) v ( l i n ) x m ( l i n ) x g v x m Term(s) minutes, m x g v x m APPENDIX 6 Task I ; Heart Rate ANCOVA Greenhouse-Geisser F •E. < c o r r e c t e d p r o b a b i l i t y 52.18 27.90 15.44 .0000 .0000 .0000 56.04 18.12 4.39 34.39 .000001 .0001 .0406 .000001 97.66 7.63 .0000 .0077 66.35 7.40 .0000 .0010 .0000 .0022 14.21 11.25 .0004 .0499 7.97 .0006 .0011 E p s i l o n Factors .805 .857 - 162 -APPENDIX 7 V i s i t 2: Heart Rate ANCOVA Greenhouse-Geisser Term F £ < corrected pi condition (c) 4.57 .6369 groups 15.05 .0003 hbl 287.10 .0000 age 4.57 .0370 age/dbl 146.24 .0000 hbl (T) 49.52 .0000 T(quad) x g 6.07 .0169 hbl 5.20 .0264 T r i a l 12.52 .0000 .0001 hbl 21.96 .0000 m(lin) 74.19 .0000 m(lin) x g 9.71 .0029 minutes 61.53 .0000 .0000 m x g 7.65 .0007 T( l in) x m(lin) 11.46 .0013 T( l in) x m(lin) x c 4.36 .0413 T( l in) x m(quad) x g 5.49 .0227 T x M 4.39 .0019 .0055 T x m x c 2.57 .0385 .0500 T x m x c 3.08 .0169 .0296 Term Epsilon Factor t r i a l .782 minute, m x g .742 t x m , t x m x e , t x m x g .739 - 1 6 3 -APPENDIX 8 Newman-Keuls Tests of Heart Rate Data Comparison t r i a l 1 - t r i a l 3 t r i a l 1 - t r i a l 2 t r i a l 2 - t r i a l 3 minute 1 minute 1 minute 2 minute 3 minute 2 minute 3 Condition 1 Observed Difference Between Means  8.72 6.24 2.48 10.09 7.00 3.09 C r i t i c a l Value of Q 3.71 3.08 n.s. 4.32 3.59 n.s. Task 1 minute 1 minute 1 minute 2 t r i a l 1 t r i a l 2 t r i a l 1 minute 3 minute 2 minute 3 t r i a l 3 t r i a l 3 t r i a l 2 minute 1 - minute 3 minute 1 - minute 2 minute 2 - minute 3 11.26 7.70 3.56 V i s i t 2 11.26 7.70 3.56 7.35 6.44 0.91 1.99 1.67 1.67 1.99 1.67 1.67 2.01 1.67 n.s. - 164 -APPENDIX 9 Scheffe's Tests of Heart Rate Data Condition 1 Scheffe Contrast Input Means Value high vs low reactors 7 9 . 8 - 7 6 . 5 1.75 1st minute, f ina l task Task 1 high vs low reactors/ 83.8-78.7 2.02 2.05 n.s. cond. 1, 3rd minute f ina l task C r i t i c a l Value _p 2.05 n.s. V i s i t 2 high vs low reactors/ 80.6-75.0 3.116 2.05 n.s. cond. 1, 1st minute f ina l task - 165 -APPENDIX 10 Condition 1: Systolic Blood Pressure ANCOVA Greenhouse-Geisser Term F_ _p_ < corrected probability groups 21.31 .0001 Sbl 124.85 .0000 age/Sbl 85.17 .0000 v 44.44 .0000 v x g 7.29 .0110 Sbl 29.77 .0000 t ( l i n ) 18.43 .0002 t(quad) 4.97 .0330 t r i a l 18.63 .0000 .0000 Sbl 5.09 .0310 v x t 5.20 .0080 .0115 m(quad) 16.52 .0003 min 7.54 .0011 .0016 v( l in) x t ( l in ) x m(lin) 4.78 .0360 Term(s) Epsilon Factors v( l in) x t ( l i n ) x m(lin) .980 v x t .859 minutes .923 m x g .886 - 166 -APPENDIX 11 Task 1: Systolic Blood Pressure ANCOVA Term F Ii < group 70.60 .0000 hbl 112.63 .0000 age/abl 100.98 .0000 V x g 15.48 .0002 v i s i t 51.04 .0000 hbl 6.38 .0141 m(lin) 4.06 .0481 m(lin) x g 6.73 .0118 m(quad) 18.69 .0001 minutes 10.24 .0001 m x g 5.10 .0074 v( l in) x m(lin) 4.65 .0348 Greenhouse-Geisser corrected probability .0001 .0081 Term minute, m x g Epsilon Factor .964 - 167 -APPENDIX 12 V i s i t 2: Systolic Blood Pressure ANCOVA Greenhouse-Geisser Term F R < corrected probability group 30.69 .0000 sbl 161.29 .0000 age/sbl 104.23 .0000 t ( l i n ) x g sbl t ( l i n ) 22.41 .0000 T(quad) x c x g 5.41 .0232 T r i a l 3.71 .0271 .0317 T x c x g 4.05 .0000 .0238 sbl 13.49 .0004 m(quad) 16.81 .0001 min 7.35 .0010 .0011 Term Epsilon Factor t r i a l , t x c x g .898 minutes .975 - 168 -APPENDIX 13 Newman-Kuels Tests of Systolic Blood Pressure Data Condition 1 Comparison t r i a l 1 t r i a l 1 t r i a l 2 t r i a l 3 t r i a l 2 t r i a l 3 Observed Difference Between Means  8.50 4.75 3.75 C r i t i c a l Value of Q 3.19 2.65 2.65 < .05 < .05 < .05 minute 2 minute 2 minute 3 minute 1 minute 3 minute 1 2.25 1.50 3.01 2.50 2.50 n.s. n.s. n.s. Task 1 minute 2 minute 2 minute 1 minute 1 minute 3 minute 3 3.75 2.00 1.75 2.03 1.69 1.69 < .05 < .05 < .05 V i s i t 2 t r i a l 1 -t r i a l 2 -t r i a l 1 -minute 2 minute 1 minute 2 t r i a l 3 t r i a l 3 t r i a l 2 - minute 3 - minute 3 - minute 1 4.34 6.42 2.92 10.17 8.00 2.17 2.35 1.95 1.95 1.82 1.51 1.51 < .05 < < < < .05 .05 .05 .05 < .05 - 169 -APPENDIX 14 Scheffe's Tests of Systolic Blood Pressure Data Condition 1 Scheffe C r i t i c a l Contrast Input Means Value Value high vs low reactors, 112 .3-107 .7 2.42 2.03 f ina l minute, f ina l task Task 1 high vs low reactors, 119.0 - 113.7 2.68 2.032 cond. 2, f ina l minute f ina l task V i s i t 2 high vs low reactors/ 112 .8-108 .3 2.53 2.032 cond. 1, f ina l minute f ina l task - 170 -APPENDIX 15 Condition 1: Diastol ic Blood Pressure ANCOVA Greenhouse-Geisser Term F £ < corrected probability groups 12.47 .0013 Dbl 60.15 .0000 age/Dbl 44.97 .0000 v i s i t 31.53 .0000 V x g 11.03 .0023 Dbl 13.12 .0010 t ( l i n ) 9.37 .0044 t(quad) 7.10 .0120 t r i a l 27.67 .0000 .0000 v( l in) x t ( l in ) 6.60 .0151 v( l in) x t(quad) 9.79 .0037 v( l in) x t(quad) x g 5.96 .0203 v x t 5.76 .0050 .0065 m(quad) 11.33 .0019 minutes 5.87 .0045 .0057 t ( l i n ) x m(lin) 8.05 .0077 t ( l i n ) x m(lin) x g 10.80 .0024 t x m 3.11 .0174 t x m x g 3.98 .0044 Term Epsilon Factor t r i a l .960 v x t .912 minutes .923 t x m , t x m x g .816 - 171 -APPENDIX 16 Task 1: Diastolic Blood Pressure ANCOVA Term F 2. < conditions 6.76 .0116 groups 41.22 .0000 hbl 89.62 .0000 age/hbl 80.09 .0000 V 34.26 .0000 V x g 4.38 .0404 m(quad) 5.54 .0216 - 172 -APPENDIX 17 V i s i t 2: Diastol ic Blood Pressure ANCOVA Term F 2. < Greenhouse-Geisser corrected probability group dbl age/dbl 12.38 294.90 182.46 .0008 .0000 .0000 dbl (t l in ) dbl (t quad) 12.97 5.46 .0006 .0226 T r i a l 14.50 .0000 .0000 m(lin) x c x g m (quad) 5.19 4.00 .0260 .0497 m x c x g 3.83 .0243 .0279 t(quad) x m(lin) t(quad) x m(quad) 11.55 x c 4.43 .0012 .0393 T x m 6.77 .0000 .0001 Term Epsilon Factor t r i a l .977 m x c x g .916 t x m .880 - 173 -APPENDIX 18 Newman Kuels Tests of Diastol ic Blood Pressure Data Condition 1 Comparison t r i a l 1 - t r i a l 3 t r i a l 1 - t r i a l 2 t r i a l 2 - t r i a l 3 minute 2 - minute 1 minute 2 - minute 3 minute 1 - minute 3 Observed Difference Between Means  8.58 5.42 3.16 1.68 1.08 0.00 C r i t i c a l Value of Q 2.71 2.26 2.26 1.93 1.93 n.s. < .05 < .05 < .05 n.s. n.s. Not significant Task 1 V i s i t 2 t r i a l 1 - t r i a l 3 t r i a l 2 - t r i a l 3 t r i a l 1 - t r i a l 2 10.73 7.07 3.66 1.76 1.46 1.46 < .05 < .05 < .05 - 174 -APPENDIX 19 Scheffe's Tests of Diastol ic Blood Pressure Data Condition 1 Contrast high vs low reactors, f ina l minute, 2nd last task high vs low reactors, cond. 1, f inal 2 minutes f ina l stress task Input Means 67.49 - 65.10 Scheffe Value 1.35 Task 1 72.8 - 70.8 1.34 C r i t i c a l Value 2.03 2.03 2 n.s. n.s. V i s i t 2 high vs low reactors/ 6 8 . 1 - 6 5 . 9 1.39 2.03 n.s. cond. 1, f inal minute 2nd last task - 175 -APPENDIX 20 Condition 1: Mean Arter ia l Pressure ANCOVA Term F J2 < groups 11.57 .0019 mbl 50.82 .0000 mbl/age 32.30 .0000 V 29.08 .0000 V X g 9.81 .0037 mbl 8.04 .0079 t ( l i n ) 11.17 .0021 t(quad) 5.57 .0245 t r i a l 19.59 .0000 v( l in) x t ( l in ) 10.47 .0028 v( l in) x t(quad) 4.28 .0468 mbl 8.52 .0064 m(lin) 4.55 .0495 m(quad) 4.98 .0325 minutes 4.70 .0124 t ( l i n ) x m(quad) 5.12 .0303 v( l in) x t ( l i n ) x m(lin) 4.35 .0445 Greenhouse-Geisser corrected probability .0000 .0151 Term t r i a l minute Epsilon Factor .953 .909 - 176 -APPENDIX 21 Task 1: Mean Arter ia l Pressure ANCOVA Greenhouse-Geisser Term F R < corrected probability conditions 4.97 .0294 groups 39.88 .0000 mbl 44.64 .0000 V 37.07 .0000 V X g 9.12 .0037 mbl 4.72 .0336 m(lin) x c x g 6.50 .0114 m(quad) 12.50 .0008 / minutes 5.70 .0043 .0054 m x c x g 4.43 .0138 .0163 Term Epsilon Factor minute, m x c x g .920 - 177 -APPENDIX 22 V i s i t 2: Mean Arter ia l Pressure ANCOVA Term F J2 < groups 9.83 .0026 hbl 158.66 .0000 age/hbl 96.81 .0000 hbl x (t) ( l in) 15.17 .0002 hbl (t quad) 17.46 .0001 T r i a l 5.04 .0078 m(lin) x g 5.15 .0266 t ( l i n ) x m(lin) 7.53 .0079 t ( l i n ) x m(quad) 6.93 .0106 T x m 4.13 .0029 Greenhouse-Geisser corrected probability .0089 Term Epsilon Factor t r i a l .951 t x m .962 - 178 -APPENDIX 23 Newman Keuls Tests of Mean Arter ia l Pressure Data Comparison t r i a l 1 - t r i a l 3 t r i a l 1 - t r i a l 2 t r i a l 2 - t r i a l 3 minute 2 - minute 1 minute 1 - minute 3 minute 2 - minute 3 minute 2 - minute 1 minute 2 - minute 3 minute 3 - minute 1 Condition 1 Observed Difference Between Means  6.5 5.25 1.25 2.19 1.89 .30 Task 1 2.87 1.57 1.30 C r i t i c a l Value of Q 3.19 2.66 n.s. n.s. n.s. n.s. 1.98 1.64 1.64 < .05 < .05 < .05 < .05 n.s. n.s. V i s i t 2 t r i a l 1 - t r i a l 3 t r i a l 2 - t r i a l 3 t r i a l 1 - t r i a l 2 8.17 4.92 3.25 2.21 1.85 1.85 < .05 < .05 < .05 - 179 -APPENDIX 24 Scheffe's Tests of Mean Arter ia l Pressure Data Contrast high vs low reactors, f ina l minute, f ina l task Condition 1 Input Means 86.3 - 84.0 Scheffe Value 1.48 C r i t i c a l Value 2.03 n.s. high vs low reactors, cond. 1, f ina l minute f ina l task Task 1 89.8 - 84.4 2.42 2.032 < .05 high vs low reactors/ cond. 1, f ina l minute f ina l task V i s i t 2 84.8 - 83.5 1.19 2.03 n.s. 

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