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The facial expression of pain in infants: developmental changes and individual differences 1995

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THE FACIAL EXPRESSION OF PAIN IN INFANTS: DEVELOPMENTAL CHANGES AND INDIVIDUAL DIFFERENCES by CHRISTINE MEGAN L I L L E Y B . A . ( H o n s . ) / M c G i l l U n i v e r s i t y , 1993 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n THE FACULTY OF GRADUATE STUDIES Department 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 the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A u g u s t , 1995 © C h r i s t i n e Megan L i l l e y , 1995 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT The purpose o f the s t u d y was t o examine the r o l e o f the n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament as a f a c t o r u n d e r l y 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 the f a c i a l e x p r e s s i o n o f p a i n i n i n f a n t s . I t was a l s o o f i n t e r e s t t o i d e n t i f y deve lopmenta l changes i n the f a c i a l e x p r e s s i o n o f p a i n d u r i n g the f i r s t two y e a r s o f l i f e , b o t h i n t h e o v e r a l l degree o f p a i n e x p r e s s e d and i n i n d i v i d u a l f a c i a l a c t i o n s . S u b j e c t s were i n f a n t s u n d e r g o i n g r o u t i n e i m m u n i z a t i o n i n j e c t i o n s , which a r e a d m i n i s t e r e d a t 2, 4, 6, 12, and 18 months o f age . C o n s e q u e n t l y , t h e f i v e age groups were compared. Temperament was a s s e s s e d v i a a p a r e n t r e p o r t q u e s t i o n n a i r e . A h a n d - h e l d v i d e o camera was used t o r e c o r d t h e r e a c t i o n s o f i n f a n t s u n d e r g o i n g i n o c u l a t i o n . The i n f a n t s ' f a c i a l r e a c t i o n s , as c a p t u r e d on v i d e o t a p e , were s c o r e d by t r a i n e d c o d e r s u s i n g two sys tems: (1) the N e o n a t a l F a c i a l C o d i n g System (NFCS) , a b r i e f measure l i m i t e d t o a c t i o n s r e l a t e d t o p a i n , and (2) Baby FACS, a comprehens ive system w i t h c a t e g o r i e s f o r a l l p o s s i b l e f a c i a l a c t i o n s . The c o d e r s s c o r e d t h r e e 10-second segments f o r each i n f a n t i n o r d e r t o c a p t u r e a b a s e l i n e , the i n f a n t ' s immediate r e a c t i o n , and a r e c o v e r y p e r i o d . The r e s u l t s o f the s t u d y d i d no t c o n f i r m a r e l a t i o n s h i p between temperament and a p a i n summary s c o r e d e r i v e d by p r i n c i p a l components a n a l y s i s . T h i s f i n d i n g was u n e x p e c t e d . The need f o r f u r t h e r i n v e s t i g a t i o n o f t h e 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 the p a i n response and t h e impact o f s i t u a t i o n a l f a c t o r s was d i s c u s s e d . i i The i n v e s t i g a t i o n o f deve lopmenta l changes r e v e a l e d some d i f f e r e n c e s i n the degree o f p a i n e x p r e s s e d by i n f a n t s i n d i f f e r e n t age g r o u p s . D u r i n g the b a s e l i n e and immediate r e a c t i o n t o i n j e c t i o n , 2-month o l d i n f a n t s d i s p l a y e d more d i s t r e s s t h a n 4- month o l d i n f a n t s and 6-month o l d i n f a n t s , but not more t h a n 12- o r 18-month o l d i n f a n t s . D u r i n g t h e r e c o v e r y p e r i o d , 6-month o l d i n f a n t s and 18-month o l d i n f a n t s d i s p l a y e d more d i s t r e s s t h a n 4- month o l d i n f a n t s . No o t h e r d i f f e r e n c e s were s i g n i f i c a n t . W h i l e these r e s u l t s r e q u i r e r e p l i c a t i o n , they a r e s u g g e s t i v e o f a drop i n the degree o f p a i n e x p r e s s e d around the age o f 4 months. P o s s i b l e reasons f o r such a p a t t e r n were d i s c u s s e d , w i t h a t t e n t i o n p a i d t o the development o f i n h i b i t o r y mechanisms and the impact o f o t h e r n e g a t i v e emotions such as anger and a n x i e t y . A g e - r e l a t e d changes i n t h e o c c u r r e n c e o f i n d i v i d u a l a c t i o n s were a l s o i d e n t i f i e d . The r e s u l t s o f t h e p r e s e n t s t u d y sugges t t h a t c l i n i c i a n s a s s e s s i n g p a i n i n i n f a n t s be aware o f deve lopmenta l changes such t h a t they compare t h e i r charges t o i n f a n t s o f t h e same age . i i i TABLE OF CONTENTS ABSTRACT TABLE OF CONTENTS LIST OF TABLES L I S T OF FIGURES ACKNOWLEDGMENTS INTRODUCTION LITERATURE REVIEW The C a p a c i t y o f the I n f a n t t o E x p e r i e n c e P a i n P h y s i o l o g i c a l and B e h a v i o u r a l Measures o f I n f a n t P a i n The C o n s t r u c t o f Temperament Deve lopmenta l Changes i n t h e E x p r e s s i o n o f P a i n Summary and Hypotheses METHOD S e t t i n g Sample R e f u s e r s and I n f a n t s E x c l u d e d From the Study A p p a r a t u s Procedure C o d i n g o f I n f a n t s ' F a c i a l A c t i o n s S e l e c t i o n o f t h e " b a s e l i n e " event S e l e c t i o n o f the " r e c o v e r y " event C o d i n g o f P a r e n t s ' S o o t h i n g I n t e r v e n t i o n s A n a l y s e s P r e l i m i n a r y a n a l y s e s The r e s e a r c h q u e s t i o n s RESULTS 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 the Sample 42 S o o t h i n g I n t e r v e n t i o n s 43 The Independent V a r i a b l e s 46 Age 46 Temperament 46 The r e l a t i o n s h i p between age and temperament 48 The Dependent V a r i a b l e s 48 C o l l a p s i n g o f Baby FACS a c t i o n s 48 Frequency o f o c c u r r e n c e o f f a c i a l v a r i a b l e s 49 M i s s i n g d a t a 49 C o n s t r u c t i o n o f the P a i n Summary Scores 50 Two measures o f p a i n 54 The R e l a t i o n s h i p between P a i n and Temperament 58 Deve lopmenta l Changes i n the F a c i a l E x p r e s s i o n o f 59 P a i n Deve lopmenta l Changes i n the I n t e n s i t y o f the P a i n 60 R e a c t i o n A n a l y s e s conducted on the t x b a s e l i n e " and 60 " i n j e c t i o n " events A n a l y s e s conducted on the " r e c o v e r y " event 65 Deve lopmenta l Changes i n the Nature o f the P a i n 67 E x p r e s s i o n A n a l y s e s conduc ted on the " b a s e l i n e " and 67 " i n j e c t i o n " events A n a l y s e s conducted on the " r e c o v e r y " e v e n t 77 DISCUSSION 82 F a c i a l A c t i o n s E x p r e s s i n g P a i n i n I n f a n t s 82 Temperament and the F a c i a l E x p r e s s i o n o f P a i n 84 Developmental Changes i n the F a c i a l E x p r e s s i o n o f 89 P a i n i n I n f a n t s The R e l a t i o n s h i p between NFCS and Baby FACS C o d i n g 99 D i f f e r e n c e s i n the Number o f P a i n S t i m u l i 101 C o n c l u s i o n s 102 REFERENCES 104 APPENDICES 112 A . Background C h a r a c t e r i s t i c s Q u e s t i o n n a i r e 112 B . Sample Items from the I n f a n t C h a r a c t e r i s t i c s 113 Q u e s t i o n n a i r e C . NFCS A c t i o n s 114 D. Baby FACS A c t i o n s 116 E . R e s u l t s o f P r e l i m i n a r y A n a l y s e s 120 F . Frequency o f F a c i a l A c t i o n s 122 v i L I S T OF TABLES T a b l e Page T a b l e 1. P e r c e n t o f P a r e n t s U s i n g Each S o o t h i n g 44 I n t e r v e n t i o n T a b l e 2. D e s c r i p t i o n o f Age Groups 46 T a b l e 3. D i s t r i b u t i o n o f Temperament Scores 47 T a b l e 4. F a c t o r L o a d i n g s f o r the NFCS F a c i a l 51 A c t i o n s T a b l e 5. F a c t o r L o a d i n g s f o r the Baby FACS F a c i a l 53 A c t i o n s T a b l e 6. C o r r e l a t i o n s between NFCS and Baby FACS 55 P a i n Summary Scores T a b l e 7. C o r r e l a t i o n s between NFCS A c t i o n s and 56 Baby FACS A c t i o n s : The Upper Face T a b l e 8. C o r r e l a t i o n s between NFCS A c t i o n s and 57 Baby FACS A c t i o n s : The Lower Face T a b l e 9. C o r r e l a t i o n s between P a i n Summary Scores 59 and Temperament Scores T a b l e 10. C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS 60 P a i n Summary S c o r e s by Age " B a s e l i n e " and " In j e c t i o n " events T a b l e 11. C e l l Means and S t a n d a r d D e v i a t i o n s : Baby 63 FACS P a i n Summary Scores by Age " B a s e l i n e " and " I n j e c t i o n " events T a b l e 12. C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS 65 P a i n Summary Scores by Age " R e c o v e r y " event T a b l e 13. C e l l Means and S t a n d a r d D e v i a t i o n s : Baby 67 FACS P a i n Summary Scores by Age " R e c o v e r y " event T a b l e 14. C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS 69 A c t i o n s by Age " B a s e l i n e " and " I n j e c t i o n " events T a b l e 15. C e l l Means and S t a n d a r d D e v i a t i o n s : Baby 71 FACS A c t i o n s by Age " B a s e l i n e " and " I n j e c t i o n " events T a b l e 16. U n i v a r i a t e R e s u l t s : Baby FACS A c t i o n s by 73 Age " B a s e l i n e " and " I n j e c t i o n " events v i 1 T a b l e 17. R e s u l t s : Baby FACS A c t i o n s by Event " B a s e l i n e " and " I n j e c t i o n " events 76 T a b l e 18. C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS 77 A c t i o n s by Age * *Recovery ' ' event T a b l e 19. U n i v a r i a t e R e s u l t s : NFCS A c t i o n s by Age 78 " R e c o v e r y " event T a b l e 20. C e l l Means and S t a n d a r d D e v i a t i o n s : Baby 80 FACS A c t i o n s by Age " R e c o v e r y " event v i i i L I S T OF FIGURES F i g u r e Page F i g u r e A Communication Model f o r U n d e r s t a n d i n g 11 1. C h i l d r e n ' s P a i n F i g u r e Number o f P a r e n t s U s i n g Each S o o t h i n g 45 2. I n t e r v e n t i o n F i g u r e NFCS P a i n Summary Scores by Age 62 3. Mean s c o r e s a c r o s s " b a s e l i n e " and " i n j e c t i o n " events F i g u r e Baby FACS P a i n Summary Scores by Age 64 4. Mean s c o r e s a c r o s s " b a s e l i n e " and " i n j e c t i o n " events F i g u r e NFCS P a i n Summary Scores by Age 66 5. * *Recovery ' ' event F i g u r e Baby FACS P a i n Summary Scores by Age 68 6. " R e c o v e r y " event F i g u r e I n d i v i d u a l Baby FACS A c t i o n s by Age 75 7. Mean s c o r e s a c r o s s " b a s e l i n e " and " i n j e c t i o n " events F i g u r e I n d i v i d u a l NFCS A c t i o n s by Age 79 8. " R e c o v e r y " event i x ACKNOWLEDGMENTS T h i s w o r k h a s d r a w n o n t h e t a l e n t s o f many p e o p l e . I n p a r t i c u l a r , I w o u l d l i k e t o a c k n o w l e d g e t h e a s s i s t a n c e a n d a d v i c e o f D r . K e n n e t h C r a i g , my r e s e a r c h s u p e r v i s o r , a n d t h e members o f my r e s e a r c h c o m m i t t e e , D r . C h a r l o t t e J o h n s t o n a n d D r . J a n e t W e r k e r . I w o u l d l i k e t o t h a n k t h e r e s e a r c h a s s i s t a n t s t h a t c o n t r i b u t e d t h e i r t i m e t o d a t a c o l l e c t i o n a n d c o d i n g : J u l i e E d g e , D a v e M a r k l a n d , T e r r i W i l m o n , a n d J o c e l y n W a t c h o r n . I w o u l d a l s o l i k e t o t h a n k t h e n u r s e s s t a f f i n g t h e i m m u n i z a t i o n c l i n i c s f o r t h e i r a s s i s t a n c e a n d g o o d c h e e r , a n d e x p r e s s my a d m i r a t i o n f o r t h e s e r v i c e s t h e y p r o v i d e t o t h e c o m m u n i t y . I n p a r t i c u l a r , I w o u l d l i k e t o m e n t i o n P a t A g o n - C h e n , P a t C h a d w i c k , J e n n i f e r G u i n n , C a r o l y n L a m b , E v e l y n P o e t h k o , a n d L o i s W i l l i a m s . I am a l s o i n d e b t e d t o t h e p a r e n t s who a g r e e d t o p a r t i c i p a t e i n t h e s t u d y , a n d o f c o u r s e , t o t h e b a b i e s . F i n a l l y , I w o u l d l i k e t o t h a n k M a r i l y n H i l l f o r t e c h n i c a l a d v i c e a n d m o r a l s u p p o r t ; a n d C a r m e n S t o s s e l a n d A n u r a d h a C h a w l a f o r c r i s i s i n t e r v e n t i o n a n d c o f f e e . x INTRODUCTION The l a s t decade has seen s u b s t a n t i a l changes i n the concept s o f p a i n i n i n f a n c y . Once c o n s i d e r e d n o n e x i s t e n t o r n e g l i g i b l e ( e . g . , S r o u f e , 1979) , p a i n i n the neonate i s g r a d u a l l y becoming r e c o g n i z e d as a widespread phenomenon and a p o t e n t i a l l y dangerous s t r e s s o r ( M c L a u g h l i n , H u l l , Edwards, Cramer & Dewey, 1993). These a l t e r a t i o n s i n a t t i t u d e r e f l e c t a growing body o f r e s e a r c h concerned w i t h the measurement and a l l e v i a t i o n o f p a i n i n t h e young c h i l d . T h i s r e s e a r c h has demonstrated t h a t i n f a n t s r e s p o n d t o i n v a s i v e s t i m u l i w i t h p h y s i o l o g i c a l , b e h a v i o u r a l , and m e t a b o l i c r e a c t i o n s p a r a l l e l i n g those o f a d u l t s e x p e r i e n c i n g acute p a i n ( e . g . , Anand & M c G r a t h , 1993) . F u r t h e r m o r e , the use o f b e t t e r a n e s t h e t i c s d u r i n g s u r g e r y has been shown t o have a d r a m a t i c e f f e c t on m o r b i d i t y and m o r t a l i t y , e s p e c i a l l y i n the p r e t e r m , whose m e t a b o l i c r e s o u r c e s a r e l i m i t e d (Anand & H i c k e y , 1992) . However, a g r e a t d e a l remains t o be u n d e r s t o o d . There i s a p r e s s i n g need f o r more r e s e a r c h t o c o n t r i b u t e t o b o t h b a s i c and a p p l i e d s c i e n c e . In c l i n i c a l s e t t i n g s , new methods o f c o n t r o l l i n g p a i n i n i n f a n t s a r e i n g r e a t demand. However, e f f e c t i v e p a i n p r e v e n t i o n and p a i n c o n t r o l w i l l r e q u i r e the development o f e f f i c i e n t , a c c u r a t e measures o f p a i n . Both assessment and t r e a t m e n t w i l l b e n e f i t from more b a s i c knowledge about f a c t o r s u n d e r l y i n g the e x p e r i e n c e and e x p r e s s i o n o f p a i n . A number o f p h y s i o l o g i c a l and b e h a v i o u r a l i n d i c e s a r e a v a i l a b l e f o r the assessment o f i n f a n t p a i n ( C r a i g & Grunau , 1993; F r a n c k , 1986; J o h n s t o n & 0 'Shaughnessy , 1988; M c G r a t h , 1990; P o r t e r , Porges & M a r s h a l l , 1988) . F o r example, r e s e a r c h e r s have m o n i t o r e d h e a r t r a t e , r e s p i r a t i o n r a t e , and oxygen 1 s a t u r a t i o n (Stevens & J o h n s t o n , 1991) and examined t e m p o r a l and s p e c t r o g r a p h i c c h a r a c t e r i s t i c s o f c r y (Johnston & 0 'Shaughnessy , 1988) . However, concerns about the s p e c i f i c i t y o f p h y s i o l o g i c a l measures (McGrath , 1990) and ambiguous r e s u l t s i n t h e c r y l i t e r a t u r e ( e . g . , Grunau , J o h n s t o n & C r a i g , 1990; J o h n s t o n & 0 'Shaughnessy , 1988) have l e d t o the a s s e r t i o n t h a t the e v i d e n c e d e r i v e d from f a c i a l e x p r e s s i o n i s "most c o n v i n c i n g t o d a t e " ( M c i n t o s h , Van Veen & Brameyer, 1993) . I n f a n t s ' f a c i a l e x p r e s s i o n s convey c o n s i d e r a b l e i n f o r m a t i o n , and a number o f c o d i n g systems have been d e v e l o p e d . O b j e c t i v e , a n a t o m i c a l l y - b a s e d s c a l e s , such as Baby FACS ( O s t e r & R o s e n s t e i n , 1993) and the N e o n a t a l F a c i a l C o d i n g System (NFCS; Grunau & C r a i g , 1987) seem e s p e c i a l l y u s e f u l . Baby FACS i s a comprehens ive measure, w i t h l i t t l e p u b l i s h e d m a t e r i a l on i t s use i n p a i n assessment per s e . NFCS was d e v e l o p e d w i t h p a i n assessment i n m i n d . However, w i t h the e x c e p t i o n o f one i n v e s t i g a t i o n ( J o h n s t o n , S t e v e n s , C r a i g & Grunau , 1993) , which examined the r e a c t i o n s o f neonates and 2- and 4-month o l d i n f a n t s , a l l s t u d i e s u s i n g NFCS t o examine p a i n have l o o k e d a t n e o n a t a l p a i n . D e s c r i p t i o n s o f the f a c i a l d i s p l a y i n o l d e r i n f a n t s , as measured by an o b j e c t i v e i n s t r u m e n t , a r e no t a v a i l a b l e . The e x i s t i n g s t u d i e s suggest t h a t t h e r e are s u b s t a n t i a l i n d i v i d u a l d i f f e r e n c e s i n i n f a n t s ' b e h a v i o u r a l re sponses t o p a i n f u l s t i m u l i ( e . g . , Grunau e t a l . , 1990) . R e l a t i v e l y l i t t l e i s known about the s t a b i l i t y o f such d i f f e r e n c e s , o r t h e i r c o r r e l a t e s . One c o n s t r u c t h y p o t h e s i z e d t o be i m p o r t a n t ( e . g . , H a m i l t o n & Z e l t z e r , 1994) i s temperament. Temperament r e f e r s t o 2 r e l a t i v e l y c o n s i s t e n t t r a i t s t h a t appear e a r l y i n l i f e and modulate e x p r e s s i o n s o f a c t i v i t y , r e a c t i v i t y , e m o t i o n a l i t y and s o c i a b i l i t y ( G o l d s m i t h e t a l . , 1987) . The d imens ions c o m p r i s i n g temperament and the measures used t o a s s e s s these d imens ions are the s u b j e c t o f e n e r g e t i c debate among v a r i o u s t h e o r i s t s . S e v e r a l r e s e a r c h e r s have sugges ted t h a t temperament i s r e l a t e d t o i n d i v i d u a l d i f f e r e n c e s i n p s y c h o b i o l o g i c a l re sponses t o s t r e s s (Boyce , B a r r & Z e l t z e r , 1992) . I t i s t h e r e f o r e p l a u s i b l e t h a t t h e e x p r e s s i o n o f p a i n would be r e l a t e d t o temperament, p a r t i c u l a r l y t h a t a s p e c t o f temperament m o d u l a t i n g t h e f r e q u e n c y and i n t e n s i t y o f n e g a t i v e e m o t i o n a l i t y . T h i s r e l a t i o n s h i p may shed l i g h t on the e t i o l o g 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 p a i n p e r c e p t i o n . Age , as an index o f b i o l o g i c a l m a t u r a t i o n , i s l i k e l y t o be a s s o c i a t e d w i t h the e x p r e s s i o n o f p a i n and the e x p e r i e n c e o f p a i n . The f i r s t 2 y e a r s o f l i f e w i t n e s s d r a m a t i c changes i n a lmost a l l areas o f f u n c t i o n i n g . P a i n e x p r e s s i o n i s l i k e l y t o change due t o m a t u r a t i o n , the development o f d i f f e r e n t communicat ion s k i l l s , and the g r e a t e r a b i l i t y t o remember p a i n f u l e x p e r i e n c e s . S t u d y i n g the deve lopmenta l c o u r s e o f p a i n e x p r e s s i o n may h e l p t o u n d e r s t a n d t h e p a i n e x p e r i e n c e as i n d i v i d u a l s ge t o l d e r . In a d d i t i o n , a c c o u n t i n g f o r deve lopmenta l l e v e l i s one o f the p r i m a r y concerns o f any k i n d o f assessment c a r r i e d out w i t h i n f a n t s and c h i l d r e n . The s t u d y o f deve lopmenta l changes i n the e x p r e s s i o n o f p a i n p r o v i d e s i n f o r m a t i o n r e l e v a n t t o a c c u r a t e assessment . S u r p r i s i n g l y , t h e r e have been r e l a t i v e l y few s t u d i e s o f deve lopmenta l changes i n p a i n e x p r e s s i o n d u r i n g i n f a n c y ( e . g . , C r a i g , McMahon, M o r i s o n , & 3 Zaskow, 1984; I z a r d , Hembree, & Huebner, 1987) , and none used o b j e c t i v e c o d i n g systems f o r c a p t u r i n g changes i n f a c i a l a c t i v i t y , d e s p i t e the importance o f the f a c e f o r communicat ing i n f a n t d i s t r e s s . The p r e s e n t s tudy i n v e s t i g a t e d deve lopmenta l changes i n the f a c i a l e x p r e s s i o n o f p a i n f o l l o w i n g r o u t i n e immuniza t ion a t ages 2, 4, 6, 12, and 18 months, u s i n g a c r o s s - s e c t i o n a l d e s i g n . In a d d i t i o n , the s t u d y examined the r e l a t i o n s h i p between f a c i a l a c t i v i t y i n response t o the i n j e c t i o n , and temperament as measured by a p a r e n t r e p o r t q u e s t i o n n a i r e . 4 LITERATURE REVIEW The C a p a c i t y o f the I n f a n t t o E x p e r i e n c e P a i n E a r l y r e s e a r c h e r s c o n c l u d e d t h a t newborn i n f a n t s d i d no t f e e l p a i n because t h e i r nervous system was no t s u f f i c i e n t l y d e v e l o p e d t o t r a n s m i t t h i s t y p e o f i n f o r m a t i o n ( e . g . , McGraw, 1943) . As w e l l , i t was reasoned t h a t a r e l a t i v e i n a b i l i t y t o p e r c e i v e p a i n would be a d a p t i v e d u r i n g the b i r t h p r o c e s s (Bondy, 1980) . Such n o t i o n s p r o b a b l y p e r s i s t e d because o f the m e t h o d o l o g i c a l d i f f i c u l t i e s i n h e r e n t i n s t u d y i n g a s u b j e c t i v e e x p e r i e n c e i n s u b j e c t s i n c a p a b l e o f v e r b a l communicat ion . A l s o , d o c t o r s f e a r e d t h a t the use o f a n a l g e s i c s might be damaging t o t h e n e o n a t e ' s d e l i c a t e p h y s i o l o g i c a l systems and cause c o m p l i c a t i o n s (Bauchner , May & C o a t e s , 1992; R o g e r s , 1992) . S i n c e t h e y were r e l u c t a n t t o g i v e d r u g s , i t was more a c c e p t a b l e t o b e l i e v e t h a t newborns c o u l d no t f e e l p a i n . These b e l i e f s have r e s u l t e d i n the use o f l i t t l e o r no a n a l g e s i c s d u r i n g p e d i a t r i c p r o c e d u r e s . S t u d i e s have shown a r e l u c t a n c e t o use a n a l g e s i c agents f o r b o t h major and minor s u r g e r y among p a e d i a t r i c a n e s t h e t i s t s ( P u r c e l l - J o n e s , Dormon, & Sumner, 1988) and d i r e c t o r s o f n e o n a t a l i n t e n s i v e c a r e u n i t s (NICUs) i n the U n i t e d S t a t e s and Canada (Bauchner e t a l . , 1992) . However, a t t i t u d e s may be c h a n g i n g . M c L a u g h l i n e t a l . (1993) s u r v e y e d d o c t o r s who were b o a r d c e r t i f i e d i n n e o n a t a l - p e r i n a t a l m e d i c i n e . Almost a l l o f the p h y s i c i a n s a f f i r m e d t h e n e o n a t e ' s a b i l i t y t o p e r c e i v e p a i n , and more than 75% r e p o r t e d t h a t i n t h e i r p r a c t i c e , a n e s t h e s i a was always used i n t r a o p e r a t i v e l y f o r major and minor s u r g i c a l p r o c e d u r e s , r e g a r d l e s s o f the p a t i e n t ' s age . P o s t - o p e r a t i v e a n a l g e s i a was somewhat l e s s common 5 ( M c L a u g h l i n e t a l . , 1993) . The m a j o r i t y o f p h y s i c i a n s (87%) r e p o r t e d t h a t a t t i t u d e s about p a i n and p a i n management i n newborns have changed r e c e n t l y ( M c L a u g h l i n e t a l . , 1993) . T h i s s h i f t r e f l e c t s e v i d e n c e t h a t newborn i n f a n t s do f e e l p a i n and t h a t a n e s t h e t i c t e c h n i q u e s can be used s a f e l y . Improvements i n t h e assessment o f p a i n w i l l f a c i l i t a t e the a d o p t i o n o f these t e c h n i q u e s and improve t h e i r e f f i c a c y . The chang ing a t t i t u d e s among p h y s i c i a n s r e f l e c t s e v e r a l developments i n r e s e a r c h . Anand and H i c k e y (1987) c a r e f u l l y rev iewed the e v i d e n c e and c o n c l u d e d t h a t the nervous system o f the neonate i s s u f f i c i e n t l y deve loped t o p e r m i t the p e r c e p t i o n and l o c a l i z a t i o n o f p a i n . A n a t o m i c a l and f u n c t i o n a l r e q u i r e m e n t s such as n o c i c e p t i v e nerve e n d i n g s , the l a m i n a r arrangement o f the d o r s a l h o r n , s y n a p t i c i n t e r c o n n e c t i o n s , s p e c i f i c n e u r o t r a n s m i t t e r v e s i c l e s , the t a c h y k i n i n system and the endogenous o p i a t e system a r e a l l p r e s e n t . A l t h o u g h m y e l i n a t i o n may not be complete i n n o c i c e p t i v e nerve t r a c t s , t h i s w i l l s low down t r a n s m i s s i o n , not p r e v e n t i t . The decrement i n speed i s o f f s e t by t h e f a c t t h a t impulses t r a v e l s h o r t e r d i s t a n c e s i n the i n f a n t . W h i l e i t i s p o s s i b l e t o argue t h a t some premature i n f a n t s may not have reached a s u f f i c i e n t l e v e l o f development t o e x p e r i e n c e p a i n , most r e s e a r c h conducted w i t h p r e t e r m s u b j e c t s i s c o n s i s t e n t w i t h the n o t i o n t h a t p a i n i s p a r t o f t h e i r e x p e r i e n c e . F o r example, another r e s e a r c h team has used the cutaneous f l e x o r r e f l e x , i n which a l i m b i s withdrawn from a t a c t i l e s t i m u l u s , as a measure o f p a i n p e r c e p t i o n i n p r e t e r m i n f a n t s ( F i t z g e r a l d , M i l l a r d & M c i n t o s h , 1989; F i t z g e r a l d , Shaw & M a c i n t o s h , 1988) . I t was found t h a t the t h r e s h o l d o f t h i s r e f l e x i n p r e t e r m 6 neonates i s v e r y low and g r a d u a l l y i n c r e a s e s w i t h p o s t - c o n c e p t i o n a l age , s u g g e s t i n g t h a t pre terms a r e a c t u a l l y h y p e r s e n s i t i v e t o p a i n , r e l a t i v e t o f u l l t e r m i n f a n t s and a d u l t s ( F i t z g e r a l d e t a l . , 1988) . As w e l l , i t was found t h a t r e p e a t e d s t i m u l a t i o n produced s e n s i t i z a t i o n r a t h e r t h a n the h a b i t u a t i o n seen i n a d u l t s . F u r t h e r s t u d i e s ( F i t z g e r a l d e t a l . , 1989) demonstrated t h a t the p r e t e r m i n f a n t ' s f l e x i o n r e f l e x was exaggerated f o l l o w i n g t i s s u e damage from h e e l s t i c k , p a r a l l e l i n g the t e n d e r n e s s f o l l o w i n g i n j u r y e x p e r i e n c e d by a d u l t s . P a i n f u l s t i m u l i have l o n g - t e r m e f f e c t s . Anand and H i c k e y (1987) rev iewed the m e t a b o l i c s t r e s s response i n i n f a n t s u n d e r g o i n g s u r g e r y . Over 24 h o u r s , i t was p o s s i b l e t o observe i n c r e a s e s i n v a r i o u s s t r e s s hormones and a decrease i n i n s u l i n . As a r e s u l t , f a t and c a r b o h y d r a t e s t o r e s were broken down, r e s u l t i n g i n h y p e r g l y c e m i a , the breakdown o f p r o t e i n s , and o t h e r m e t a b o l i c changes . In t h e case o f i n f a n t s who a r e i l l o r premature , the m e t a b o l i c b a l a n c e i s a l r e a d y p r e c a r i o u s . C o n s e q u e n t l y , the s t r e s s response d e s c r i b e d above can be dangerous . P a i n demands t o o many r e s o u r c e s ; the s t r e s s o f p a i n d e p l e t e s body s t o r e s , which i s d e t r i m e n t a l t o r e c o v e r y and growth . Anand, S i p p e l l and A y n s l e y - G r e e n (1987) s t u d i e d the a d d i t i o n o f f e n t a n y l , an o p i o i d , t o the min imal a n e s t h e s i a r o u t i n e l y a d m i n i s t e r e d t o i n f a n t s u n d e r g o i n g a s u r g i c a l procedure t o c l o s e a h e a r t v a l v e . F e n t a n y l was found t o reduce the major hormonal responses t o s u r g e r y . Anand and H i c k e y (1992) compared deep a n e s t h e s i a w i t h s u f e n t a n i l t o l i g h t a n e s t h e s i a w i t h h a l o t h a n e and morphine i n i n f a n t s s u b j e c t e d t o s u r g e r y . I t was found t h a t deep a n e s t h e s i a reduced 7 the s t r e s s r e s p o n s e , and a l s o had a s u b s t a n t i a l impact on m o r b i d i t y and m o r t a l i t y . I n f a n t s g i v e n s u f e n t a n i l had a s i g n i f i c a n t l y lower i n c i d e n c e o f i n f e c t i o n and o t h e r c o m p l i c a t i o n s . There were no p o s t - o p e r a t i v e deaths among the 30 neonates g i v e n s u f e n t a n i l , w h i l e 4 o f the 15 i n f a n t s g i v e n h a l o t h a n e p l u s morphine d i e d . The use o f a d r u g w i t h a s t r o n g e r a n e s t h e t i c e f f e c t produced a marked improvement i n the outcome o f s u r g e r y . These d a t a make a power fu l case f o r t h e use o f deep a n e s t h e s i a i n neonates d u r i n g major s u r g e r y t o a l l e v i a t e the damaging e f f e c t s o f p a i n . D o c t o r s have been urged t o "extend t o neonates t h e p r i n c i p l e t h a t complete i n t r a o p e r a t i v e a n e s t h e s i a improves the outcome o f s u r g e r y , a concept t h a t i s w i d e l y a c c e p t e d i n the c a r e o f a d u l t p a t i e n t s " (Rogers , 1992, p . 5 6 ) . I n f a n t s i n the NICU a r e r e p e a t e d l y s u b j e c t e d t o p r o c e d u r e s t h a t a r e l e s s i n v a s i v e t h a n major s u r g e r y , but s t i l l p a i n f u l . I n d i c e s o f p a i n observed d u r i n g such p r o c e d u r e s as h e e l s t i c k f o r b l o o d sampl ing purposes o r i n j e c t i o n o f v i t a m i n s o r v a c c i n e s r a i s e the p o s s i b i l i t y t h a t even these s t r e s s o r s may be d e t r i m e n t a l . Growth i s p a r t i c u l a r l y i m p o r t a n t i n premature i n f a n t s . I n f a n t s who are o t h e r w i s e s t a b l e a r e o f t e n kept i n t h e NICU u n t i l they g a i n w e i g h t . I n t e r v e n t i o n s which i n c r e a s e the amount o f energy a v a i l a b l e may f a c i l i t a t e growth ( D e i r i g g i , 1990) . S i n c e p a i n uses up m e t a b o l i c r e s o u r c e s , the r e d u c t i o n o f even m i l d p a i n may reduce energy e x p e n d i t u r e and i n c r e a s e growth . In a d d i t i o n t o the d e t r i m e n t a l p h y s i c a l s eque lae o f p a i n , r e c e n t r e s e a r c h sugges ts t h a t l o n g - t e r m e f f e c t s on b e h a v i o u r may 8 a l s o e x i s t . T a d d i o , G o l d b a c h , I p p , S t e v e n s , and Koren (1995) compared male i n f a n t s who had and had not undergone c i r c u m c i s i o n , and found t h a t c i r c u m c i s e d males r e a c t e d t o DPT i n j e c t i o n s w i t h g r e a t e r v i g o u r . S i m i l a r l y , Grunau and h e r c o l l e a g u e s (Grunau, W h i t f i e l d & P e t r i e , 1994; Grunau , W h i t f i e l d , P e t r i e & F r y e r , 1994) s t u d i e d t o d d l e r s who had been e x t r e m e l y low b i r t h w e i g h t (ELBW) i n f a n t s , and thus t y p i c a l l y exposed t o a number o f p a i n f u l m e d i c a l p r o c e d u r e s . The r e s u l t s sugges t t h a t the ELBW group d i f f e r e d from normal c h i l d r e n on measures o f p a i n s e n s i t i v i t y and s o m a t i z a t i o n . However, the d i r e c t i o n and t ime c o u r s e o f t h i s d i f f e r e n c e are not c l e a r , and the q u e s t i o n r e q u i r e s f u r t h e r s t u d y . A l l e v i a t i o n o f the i n t e n s e p a i n o f major and minor s u r g e r y , and the r e p e a t e d p a i n o f p r o c e d u r e s such as h e e l l a n c e i s becoming a p r i o r i t y i n n e o n a t a l wards . However, e f f o r t s a t p a i n r e d u c t i o n w i l l no t be s u c c e s s f u l w i t h o u t an a c c u r a t e means o f measur ing the p a i n e x p e r i e n c e d by newborns and o l d e r i n f a n t s . Assessment i s d i f f i c u l t , g i v e n t h a t we are f o r c e d t o i n f e r a s u b j e c t i v e s t a t e t h r o u g h n o n v e r b a l r e s p o n s e s . However, i n f a n t s d i s p l a y a number o f q u a n t i f i a b l e changes f o l l o w i n g p a i n f u l s t i m u l a t i o n . 9 P h y s i o l o g i c a l and B e h a v i o u r a l Measures o f I n f a n t P a i n C r a i g , L i l l e y , and G i l b e r t (1995) have p r e s e n t e d a model o f c h i l d r e n ' s p a i n b e h a v i o u r which emphasizes i t s f u n c t i o n as communicat ion , a l e r t i n g c a r e g i v e r s t o an i n f a n t ' s d i s t r e s s . F i g u r e 1 p r e s e n t s the mode l , which d e l i n e a t e s the r o l e o f the c h i l d ( e x p e r i e n c i n g and e x p r e s s i n g p a i n ) and the r o l e o f the a d u l t ( i n t e r p r e t i n g b e h a v i o u r and r e s p o n d i n g a p p r o p r i a t e l y ) . The model i s p r e s e n t e d here i n o r d e r t o draw a t t e n t i o n t o the f a c t t h a t the e x p e r i e n c e o f p a i n and i t s e x p r e s s i o n a r e d i s t i n c t , though r e l a t e d , phenomena. However, the r e s e a r c h e r o r c a r e g i v e r has d i r e c t acces s t o e x p r e s s i o n o n l y . I t i s d i f f i c u l t , i f no t i m p o s s i b l e , t o know how an i n f a n t e x p e r i e n c e s the w o r l d . I t i s i m p o r t a n t t o remain aware t h a t any e x t r a p o l a t i o n from an i n f a n t ' s e x p r e s s i o n t o h i s o r h e r e x p e r i e n c e i s an i n f e r e n c e . I t may be argued t h a t the a n a t o m i c a l s u b s t r a t e s and m e t a b o l i c re sponses d e s c r i b e d above i n d i c a t e n o c i c e p t i v e a c t i v i t y , t h a t i s , a c t i v i t y i n body systems s e n s i t i v e t o i n v a s i v e e v e n t s , r a t h e r t h a n s u b j e c t i v e d i s t r e s s . However, i n f a n t s do respond t o i n v a s i v e s t i m u l i w i t h t h e p h y s i o l o g i c a l and b e h a v i o u r a l re sponses t h a t accompany s u b j e c t i v e p a i n i n a d u l t s . J o h n s t o n and S t r a d a (1986) d e s c r i b e d the n e o n a t e ' s immediate re sponses t o v a c c i n a t i o n . The i n i t i a l re sponse c o n s i s t e d o f a drop i n h e a r t r a t e , f o l l o w e d by a l o n g , h i g h - p i t c h e d c r y , t h e n by a p e r i o d o f apnea, r i g i d i t y o f t h e t o r s o and l i m b s , and a f a c i a l e x p r e s s i o n o f p a i n . T h i s was f o l l o w e d by a s h a r p i n c r e a s e i n h e a r t r a t e , l o w e r - p i t c h e d but dysphonated c r i e s ( i n which more e f f o r t was e x e r t e d and the harmonies o f t h e c r y p a t t e r n were 10 T T ft  O  3 n 0 5 • C u CD  O ) c it  i a rV  >  o • w O O cr  ro  rr  c 3 t— 1 o Q>  na  ri - CU  H - H - O  3 3 2 o a x  0)  3 C 0)  o »-»  r r co  c cr  3 H- rr  r r rt>  a o c cr  3  M i 0)  3 rr CO 3 0)  « £) 3 a o G  3 a (0  C O r r C u 3 a o 3*  n 3*  C U ^ 3 P O 0) H- a ro  3 CO T3 CU M- 3 " if ! ? 8 S * I:  5 3 EL "8  S.  5'  3 o X g c r- H >  o s o b s c u r e d by o v e r l o a d i n g a t the l a r y n x ) , and l e s s body r i g i d i t y . The f a c i a l e x p r e s s i o n o f p a i n p e r s i s t e d . A f t e r 30 s econds , h e a r t r a t e remained e l e v a t e d , c r i e s were lower i n p i t c h , m o s t l y phonated , and more r h y t h m i c w i t h a r i s i n g and f a l l i n g p a t t e r n o f i n t o n a t i o n . Body p o s t u r e r e t u r n e d t o normal and f a c i a l e x p r e s s i o n r e t u r n e d t o the a t r e s t c o n f i g u r a t i o n . A number o f p h y s i o l o g i c a l i n d i c e s have been used t o a s s e s s p a i n . H e a r t r a t e i s a common measure, s i n c e i t i n c r e a s e s due t o a c t i v a t i o n o f the s y m p a t h e t i c nervous system ( C r a i g & G r u n a u , 1993) . R e s p i r a t i o n r a t e and t r a n s c u t a n e o u s oxygen l e v e l s decrease ( C r a i g , W h i t f i e l d , Grunau , L i n t o n & H a d j i s t a v r o p o u l o s , 1993) . Oxygen s a t u r a t i o n t y p i c a l l y d e c r e a s e s i n response t o p a i n f u l events and i n t r a c r a n i a l p r e s s u r e shows s u b s t a n t i a l f l u c t u a t i o n (Johnston & S t e v e n s , 1991; Stevens & J o h n s t o n , 1991) . C a r d i a c v a g a l t o n e , an i n d i c a t i o n o f p a r a s y m p a t h e t i c a c t i o n , d e c r e a s e s as the body devotes more r e s o u r c e s t o the s t r e s s response ( P o r t e r e t a l . , 1988) . V a r i a b i l i t y i n p h y s i o l o g i c a l i n d i c e s may c a r r y as much i n f o r m a t i o n as changes i n the mean v a l u e ( M c i n t o s h e t a l . , 1993) . The use o f p h y s i o l o g i c measures i s somewhat p r o b l e m a t i c as such responses are l i k e l y t o r e f l e c t s t r e s s i n a g e n e r a l sense r a t h e r t h a n p a i n (McGrath , 1990) . A c c o r d i n g l y , p h y s i o l o g i c a l measures are most u s e f u l when combined w i t h b e h a v i o u r a l s i g n s o f d i s t r e s s . The d r a m a t i c r e s u l t s o f p r e v e n t i n g p a i n w i t h a n a l g e s i c s suggest t h a t newborns s u f f e r from a l i m i t e d a b i l i t y t o communicate t h e i r p a i n t o c a r e g i v e r s r a t h e r than a l i m i t e d a b i l i t y t o p e r c e i v e p a i n ( C r a i g & Grunau , 1993) . However, i n f a n t s do have s e v e r a l means o f communicat ing t h e i r e x p e r i e n c e . 12 One o f the most s a l i e n t t o c a r e g i v e r s i s c r y , which has o b v i o u s a d a p t i v e v a l u e i n summoning a i d f o r the c h i l d . F o r t h i s r e a s o n , c r y has been r e f e r r e d t o as a " b i o l o g i c a l s i r e n " ( Z e s k i n d & M a r s h a l l , 1988) . C r y c o n t r i b u t e d t o a d u l t judgments o f s e n s o r y i n t e n s i t y and a f f e c t i v e d i s c o m f o r t i n neonates u n d e r g o i n g h e e l l a n c e ( C r a i g , Grunau & A q u a n - A s s e e , 1988) . V a r i o u s parameters o f c r y i n g change i n response t o p a i n . When the p a i n f u l s t i m u l u s o f i n j e c t i o n was c o n t r a s t e d w i t h n o n - p a i n f u l s t i m u l i , i n t h i s case head r e s t r a i n t and exposure t o a j a c k - i n - t h e - b o x , s p e c t r a l a n a l y s i s showed t h a t p a i n c r i e s were more i r r e g u l a r , h i g h e r p i t c h e d , and c o n t a i n e d more energy i n the h i g h e r s p e c t r a (Johns ton & 0 'Shaughnessy , 1988) . However, these r e s u l t s were not r e p l i c a t e d i n a s t u d y t h a t used d i f f e r e n t s t i m u l i as the n o n - i n v a s i v e c o n t r o l s : Grunau e t a l . (1990) compared i n t r a m u s c u l a r i n j e c t i o n w i t h two t a c t i l e s t i m u l i , the a p p l i c a t i o n o f dye t o the u m b i l i c u s and the a p p l i c a t i o n o f an a l c o h o l swab t o the t h i g h , and found t h a t the p a i n c r y d i f f e r e d o n l y i n h a v i n g s h o r t e r l a t e n c y and l o n g e r d u r a t i o n o f the f i r s t c r y c y c l e . R e c e n t l y , a s i n g l e parameter , the H - v a l u e , has been proposed as an i n d i c a t o r o f o v e r a l l l e v e l o f d i s t r e s s ( X i e , Ward, & L a s z l o , 1990) . T h i s i n d e x i s d e r i v e d from t h e " c r y phonemes" o f t r a i l i n g , doub le harmonic b r e a k , d y s p h o n a t i o n , h y p e r p h o n a t i o n , and i n h a l a t i o n , as w e l l as the t o t a l d u r a t i o n o f c r y . However, the H - v a l u e was d e v e l o p e d t o r e f l e c t p a r e n t s ' s u b j e c t i v e r a t i n g s o f d i s t r e s s and may not be s p e c i f i c t o p a i n . Body movements a l s o p r o v i d e i n f o r m a t i o n . The I n f a n t Body C o d i n g System (IBCS; C r a i g e t a l . , 1993) p r o v i d e d a framework f o r s c o r i n g motor a c t i v i t y r e l e v a n t t o p a i n . Movement was s c o r e d as 13 p r e s e n t o r a c t i v e f o r the hands , f e e t , arms, l e g s , head , and t o r s o o f 56 p r e t e r m and f u l l - t e r m newborns u n d e r g o i n g h e e l l a n c i n g . A c t i v i t y i n c r e a s e d d u r i n g a p r e p a r a t o r y swab p r o c e d u r e , s u g g e s t i n g t h a t the body movements s t u d i e d do not d i s c r i m i n a t e p a i n , a l t h o u g h they became s t i l l more v i g o u r o u s d u r i n g the l a n c e . I n c r e a s i n g l y , r e s e a r c h e r s are u s i n g s c a l e s based on f a c i a l e x p r e s s i o n t o a s se s s p a i n . T h i s m o d a l i t y has c o n s i d e r a b l e importance as a b e h a v i o u r a l measure, because r e s e a r c h has c o n s i s t e n t l y i d e n t i f i e d a number o f f a c i a l a c t i o n s a s s o c i a t e d w i t h p h y s i c a l d i s t r e s s , w h i l e t h e r e have been c o n t r a d i c t o r y f i n d i n g s i n r e g a r d s t o t h e f e a t u r e s o f c r y . S e v e r a l systems a l l o w the q u a n t i f i c a t i o n o f i n f a n t s ' f a c i a l a c t i v i t y d u r i n g p a i n f u l s t i m u l a t i o n . I z a r d , Hembree, Dougherty & S p i z z i r i (1983) o b s e r v e d 36 i n f a n t s between t h e ages o f 2 and 19 months d u r i n g an immuniza t ion p r o c e d u r e . V i d e o r e c o r d s were used t o s c o r e f a c i a l e x p r e s s i o n u s i n g the M a x i m a l l y D i s c r i m i n a t i v e F a c i a l Movement C o d i n g System (MAX; I z a r d , 1979) . MAX i s based upon judgments t h a t i n f a n t f a c i a l e x p r e s s i o n s conform t o p r e j u d g e d t e m p l a t e s o f s p e c i f i c emotions and p h y s i c a l d i s t r e s s , w i t h the brow, eye , and mouth r e g i o n s o f the f a c e examined s e p a r a t e l y . The MAX coded e x p r e s s i o n s were l a t e r examined u s i n g a system c a l l e d A f f e x , i n which t e m p l a t e s a r e a p p l i e d t o the e n t i r e f a c e . The e x p e r i m e n t e r s i d e n t i f i e d a r e l i a b l e * p h y s i c a l d i s t r e s s ' e x p r e s s i o n i n response t o the i n j e c t i o n . Other systems a v a i l a b l e f o r c o d i n g the f a c i a l e x p r e s s i o n o f p a i n were d e r i v e d from t h e F a c i a l A c t i o n C o d i n g System (FACS) deve loped by Ekman and F r i e s e n f o r use w i t h a d u l t s (1978) . FACS may be used t o s c o r e e i t h e r s t i l l photos o r v i d e o t a p e s u s i n g s t o p 14 a c t i o n and s low mot ion v i e w i n g . The system i s a n a t o m i c a l l y based and comprehens ive , and i n v o l v e s s c o r i n g the presence o r absence o f i n d i v i d u a l a c t i o n u n i t s r a t h e r than g l o b a l e x p r e s s i o n s . Baby FACS ( O s t e r & R o s e n s t e i n , 1993) was d e v e l o p e d d i r e c t l y from FACS. L i k e FACS, i t i s an e x h a u s t i v e s e t o f a n a t o m i c a l l y based a c t i o n u n i t s which a r e coded w i t h o u t r e f e r e n c e t o c o n f i g u r a t i o n s thought t o s p e c i f y c e r t a i n emot ions . Because Baby FACS i s comprehensive and c a p a b l e o f making v e r y s u b t l e d i s t i n c t i o n s , i t i s ex treme ly u s e f u l as a r e s e a r c h t o o l . However, these v i r t u e s make i t unwie ldy and i n a p p r o p r i a t e f o r c l i n i c a l a p p l i c a t i o n s . Baby FACS was used t o examine the p a i n re sponses o f 56 premature and f u l l t e r m i n f a n t s u n d e r g o i n g h e e l l a n c e f o r b l o o d s a m p l i n g purposes ( C r a i g , H a d j i s t a v r o p o u l o s , Grunau & W h i t f i e l d , 1994) . The f o l l o w i n g a c t i o n s were s i g n i f i c a n t l y more common d u r i n g h e e l l a n c e than d u r i n g a p r e l i m i n a r y swabbing: AU4-Brow Lower, AU6-Cheek R a i s e , A U 1 2 - L i p C o r n e r P u l l , and AU26-Jaw D r o p . The N e o n a t a l F a c i a l C o d i n g System (NFCS; Grunau & C r a i g , 1987) was adapted from a p p l i c a t i o n s o f FACS t o the s t u d y o f p a i n i n a d u l t s , i n o r d e r t o index p a i n i n i n f a n t s . NFCS i s not a n a t o m i c a l l y comprehens ive , but i s l i m i t e d t o f a c i a l a c t i o n s r e l e v a n t t o the e x p r e s s i o n o f p a i n . Ten a c t i o n s are s c o r e d : brow b u l g e , eye squeeze , deepened n a s o - l a b i a l f u r r o w , open l i p s , v e r t i c a l s t r e t c h mouth, h o r i z o n t a l . s t r e t c h mouth, l i p p u r s e , t a u t tongue , c h i n q u i v e r , and tongue p r o t r u s i o n . Grunau e t a l . (1990) v i d e o t a p e d neonates w h i l e an i n t r a m u s c u l a r i n j e c t i o n was a d m i n i s t e r e d i n the t h i g h , a l c o h o l was rubbed on t h e o p p o s i t e t h i g h , and dye was a p p l i e d t o the u m b i l i c a l s t u b . T r a i n e d c o d e r s 15 b l i n d t o the type o f s t i m u l u s used NFCS t o s c o r e the t a p e . I t was found t h a t NFCS a l l o w e d d i s c r i m i n a t i o n o f the i n j e c t i o n from the o t h e r two n o n - i n v a s i v e t a c t i l e e v e n t s . The p a i n f u l s t i m u l u s provoked s i g n i f i c a n t l y g r e a t e r t o t a l f a c i a l a c t i v i t y and a s h o r t e r l a t e n c y t o f a c i a l movement. The f a c i a l a c t i o n s most c o n s i s t e n t l y a s s o c i a t e d w i t h p a i n were brow b u l g e , eye squeeze , deepened n a s o l a b i a l f u r r o w , and open mouth. NFCS has a l s o been used s u c c e s s f u l l y w i t h premature i n f a n t s . F a c i a l a c t i v i t y was found t o be s i g n i f i c a n t l y g r e a t e r d u r i n g h e e l l a n c e t h a n d u r i n g b a s e l i n e , swab, o r r e c o v e r y i n t e r v a l s ( C r a i g e t a l . , 1993) . However, the premature i n f a n t s i n t h i s s t u d y d i s p l a y e d l e s s f a c i a l a c t i v i t y i n compar i son w i t h f u l l t e r m i n f a n t s . F a c i a l a c t i v i t y was found t o be more s p e c i f i c t o the h e e l l a n c e t h a n were measures o f b o d i l y a c t i v i t y ( the IBCS) and p h y s i o l o g i c a l r e s p o n s e s . In an e a r l i e r s tudy (Grunau & C r a i g , 1987) , i n f a n t s u n d e r g o i n g h e e l l a n c i n g f o r b l o o d s a m p l i n g purposes were observed i n o r d e r t o determine the e f f e c t o f s l eep /wake s t a t e s and sex . A w a k e / a l e r t i n f a n t s were found t o d i s p l a y more f a c i a l a c t i v i t y i n response t o the l a n c e t h a n i n f a n t s i n q u i e t s l e e p . Male i n f a n t s were f a s t e r t o re spond t h a n female i n f a n t s . Nurses have r e p o r t e d t h a t they i n c o r p o r a t e i n f o r m a t i o n about f a c i a l a c t i v i t y i n t o judgments o f i n f a n t p a i n ( P i g e o n , M c G r a t h , Lawrence & MacMurray, 1989) . When a d u l t s were asked t o v iew v i d e o t a p e s o f newborns u n d e r g o i n g h e e l l a n c e and judge the i n t e n s i t y o f t h e i r p a i n e x p e r i e n c e , the j u d g e s ' d e c i s i o n s were i n f l u e n c e d by f a c i a l e x p r e s s i o n ( C r a i g e t a l . , 1988; H a d j i s t a v r o p o u l o s , C r a i g , Grunau & J o h n s t o n , 1994) . Both c r y and 16 f a c i a l a c t i v i t y de termined the r a t i n g s they made, but s c o r e s d e r i v e d from NFCS were more i n f l u e n t i a l t h a n i n d i c e s o f c r y . The p r e s e n t s tudy used f a c i a l e x p r e s s i o n as an index o f p a i n , s i n c e a b e h a v i o u r a l measure w i t h a r e c o r d o f c o n s i s t e n t f i n d i n g s was d e s i r e d . Two c o d i n g systems were used: the Neonata l F a c i a l C o d i n g System (NFCS; Grunau & C r a i g , 1990) and Baby FACS ( O s t e r & R o s e n s t e i n , 1982, 1993) . Both systems were i n c l u d e d because each has d i f f e r e n t s t r e n g t h s . NFCS i s s i m p l e r and more a p p r o p r i a t e f o r c l i n i c a l use but Baby FACS i s more d e t a i l e d and b e t t e r a b l e t o c a p t u r e s u b t l e d i s t i n c t i o n s . The C o n s t r u c t o f Temperament Bab ie s v a r y w i d e l y i n b e h a v i o u r a l c h a r a c t e r i s t i c s , and these q u a l i t i e s a r e l i k e l y t o r e f l e c t and i n f l u e n c e an i n f a n t ' s s u b j e c t i v e e x p e r i e n c e and have an impact on the env ironment , e s p e c i a l l y the s o c i a l env ironment . F o r example, K o r n e r (1971) noted t h a t d i f f e r e n c e s i n c r y i n g , s o o t h a b i l i t y and s e l f - c o m f o r t i n g a r e l i k e l y t o a f f e c t t h e i n f a n t ' s e x p e r i e n c e o f p l e a s u r e and p a i n and the memory t r a c e s t h e s e may l e a v e . They a r e a l s o l i k e l y t o a f f e c t c a r e g i v e r s ' re sponses t o the c h i l d . D i f f e r e n t a u t h o r s o f f e r compet ing d e f i n i t i o n s o f temperament. M c C a l l ( i n G o l d s m i t h e t a l . , 1987) a t tempted t o i n t e g r a t e v a r y i n g v iews by d e f i n i n g temperament as r e l a t i v e l y c o n s i s t e n t , b a s i c d i s p o s i t i o n s i n h e r e n t i n the p e r s o n t h a t u n d e r l i e and modulate t h e e x p r e s s i o n o f a c t i v i t y , r e a c t i v i t y , e m o t i o n a l i t y and s o c i a b i l i t y . Most r e s e a r c h e r s f e e l t h a t e lements o f temperament a r e p r e s e n t i n i n f a n c y , and those e lements a r e l i k e l y t o be s t r o n g l y i n f l u e n c e d by b i o l o g i c a l f a c t o r s . As c h i l d r e n mature , the e x p r e s s i o n o f temperament i s 17 i n c r e a s i n g l y dependent on e x p e r i e n c e and c o n t e x t ( G o l d s m i t h e t a l . , 1987) . The t h e o r e t i c a l emphasis on b i o l o g y i s s u p p o r t e d by a growing body o f r e s e a r c h on i n d i v i d u a l d i f f e r e n c e s i n p s y c h o b i o l o g i c a l re sponses t o s t r e s s . I t i s hoped t h a t t h e temperament c o n s t r u c t w i l l e l u c i d a t e the r e l a t i o n s h i p between s t a b l e i n d i v i d u a l d i f f e r e n c e s a t the l e v e l o f the c e n t r a l nervous system and s t a b l e i n d i v i d u a l d i f f e r e n c e s a t the l e v e l o f b e h a v i o u r . T h i s i s p a r t i c u l a r l y t r u e o f a component o f temperament g i v e n v a r i o u s names i n d i f f e r e n t f o r m u l a t i o n s b u t c e n t e r i n g around the e x p e r i e n c e and e x p r e s s i o n o f n e g a t i v e emot ions . I n t e r e s t i n i n f a n t temperament o r i g i n a t e d w i t h the New York L o n g i t u d i n a l Study (NYLS) , c a r r i e d out by Thomas, C h e s s , B i r c h , H e r t z i g and Korn i n 1963. These r e s e a r c h e r s c o n c e i v e d o f temperament as b e h a v i o u r a l s t y l e , t h a t i s , the how o f b e h a v i o u r i n s t e a d o f the why o r the what ( G o l d s m i t h e t a l . , 1987) . The NYLS c o n s i s t e d o f p a r e n t i n t e r v i e w s which were then s u b j e c t e d t o an " i n d u c t i v e c o n t e n t a n a l y s i s " i n o r d e r t o d e r i v e n i n e c a t e g o r i e s o f temperament: A c t i v i t y L e v e l , A p p r o a c h / W i t h d r a w a l , R e g u l a r i t y , A d a p t a b i l i t y , T h r e s h o l d , I n t e n s i t y , Mood, D i s t r a c t a b i l i t y , and A t t e n t i o n S p a n / P e r s i s t e n c e (Thomas & C h e s s , 1977) . The r e s e a r c h i n t e r v i e w was l a t e r s i m p l i f i e d t o produce t h e I n f a n t Temperament Q u e s t i o n n a i r e ( ITQ; C a r e y , 1970) and the R e v i s e d I n f a n t Temperament Q u e s t i o n n a i r e (RITQ; C a r e y & M c D e v i t t , 1978) , u s i n g the same c a t e g o r i e s . These c a t e g o r i e s were a l s o combined t o c h a r a c t e r i z e t h r e e t y p e s o f i n f a n t : e a s y , d i f f i c u l t , and s low- to -warm-up . A d i f f i c u l t c h i l d , f o r example, was 18 i r r e g u l a r i n b i o l o g i c a l f u n c t i o n s , s low t o a d a p t , i n t e n s e i n mood, showed r e l a t i v e l y f r e q u e n t n e g a t i v e mood, and tended t o withdraw from n o v e l s t i m u l i (Thomas e t a l . , 1963) . The a u t h o r s endorsed an i n t e r a c t i v e v i e w p o i n t i n t h a t they emphasize the " g o o d n e s s - o f - f i t " between temperament and environment (Thomas & C h e s s , 1977) . T h a t i s , whether a g i v e n c h i l d i s " d i f f i c u l t " depends no t o n l y on c h a r a c t e r i s t i c s o f the c h i l d , but on t h e match between q u a l i t i e s i n the c h i l d and q u a l i t i e s i n the p a r e n t . The NYLS has been c r i t i c i z e d because i t o f f e r e d no g u i d e l i n e s f o r independent r e p l i c a t i o n o f the d e r i v a t i o n o f the n i n e c a t e g o r i e s and because t h e r e were problems o f o v e r l a p among t h e c a t e g o r i e s ( G o l d s m i t h & Campos, 1982) . A d i f f e r e n t approach came from Buss and P lomin (1984) , who were d i s s a t i s f i e d w i t h the b r o a d d e f i n i t i o n o f temperament used by Thomas and Chess and d i s a p p o i n t e d by the p s y c h o m e t r i c problems o f the NYLS and the RITQ. Buss and P lomin d e f i n e d temperament as a s e t o f i n h e r i t e d p e r s o n a l i t y t r a i t s t h a t appear e a r l y i n l i f e ( G o l d s m i t h e t a l . , 1987) , p l a c i n g a c o n s i d e r a b l e emphasis on b i o l o g y and g e n e t i c s . They d e s c r i b e d t h r e e e lements o f temperament. The f i r s t was l a b e l l e d E m o t i o n a l i t y , a l t h o u g h i t i s a c t u a l l y s p e c i f i c t o n e g a t i v e emotions o f f e a r , a n g e r , and d i s t r e s s . E m o t i o n a l i t y i s the tendency t o become upse t e a s i l y and i n t e n s e l y . I t i s b e l i e v e d t o stem from an i n h e r i t e d s y m p a t h e t i c r e a c t i v i t y . Buss and P lomin (1984) b e l i e v e t h a t e m o t i o n a l i t y i s l a r g e l y r e s p o n s i b l e f o r the e a s y / d i f f i c u l t d i m e n s i o n . The o t h e r e lements i n t h e i r t h e o r y o f temperament a r e A c t i v i t y , which r e f e r s t o the tempo and v i g o u r o f b e h a v i o u r , and S o c i a b i l i t y , a tendency t o respond warmly t o human c o n t a c t . 19 These d imens ions were measured w i t h a g e - a p p r o p r i a t e v e r s i o n s o f t h e EAS Temperament Survey f o r C h i l d r e n (Buss & P l o m i n , 1984) . Bates (1980) u t i l i z e d a d e f i n i t i o n o f temperament v e r y s i m i l a r t o Buss and P l o m i n , but p i c k e d up on the d imens ion o f i n f a n t d i f f i c u l t n e s s t h a t o r i g i n a t e d w i t h the NYLS. H y p o t h e s i z i n g t h a t i n f a n t d i f f i c u l t n e s s would be i m p o r t a n t f o r i n d i v i d u a l d i f f e r e n c e s i n p e r s o n a l i t y deve lopment , c h i l d r e n ' s e f f e c t on a d u l t s o c i a l i z a t i o n a g e n t s , and the e a r l y o r i g i n s o f c h i l d h o o d b e h a v i o u r p r o b l e m s , Bates drew q u e s t i o n s from v a r i o u s s o u r c e s , a d m i n i s t e r e d them t o t h e p a r e n t s o f 322 i n f a n t s and f a c t o r - a n a l y z e d the r e s u l t s t o produce the I n f a n t C h a r a c t e r i s t i c s Q u e s t i o n n a i r e ( ICQ; B a t e s , F r e e l a n d , & L o u n s b u r y , 1979) . The f i r s t f a c t o r o f the ICQ, l a b e l l e d F u s s y - D i f f i c u l t , concerned the f r e q u e n c y and i n t e n s i t y o f n e g a t i v e a f f e c t e x p r e s s i o n s . I t t h e r e f o r e c o r r e s p o n d e d t o the Mood and I n t e n s i t y c a t e g o r i e s o f t h e NYLS and RITQ, and the E m o t i o n a l i t y d imens ion o f the EASI ( B a t e s , 1980) . The F u s s y - D i f f i c u l t f a c t o r accounted f o r 59.8% o f t h e v a r i a n c e on the ICQ, and showed good r e l i a b i l i t y and v a l i d i t y (Bates e t a l . , 1979) . The o t h e r f a c t o r s were U n a d a p t a b l e , D u l l , and U n p r e d i c t a b l e , but these d imens ions were somewhat u n s a t i s f a c t o r y i n terms o f r e l i a b i l i t y and v a l i d i t y . Bates (1980) emphasized the f a c t t h a t d i f f i c u l t temperament, as measured by p a r e n t r e p o r t q u e s t i o n n a i r e s , i s a s o c i a l p e r c e p t i o n h a v i n g b o t h o b j e c t i v e and s u b j e c t i v e components, but noted t h a t even the s u b j e c t i v e a s p e c t s o f p a r e n t p e r c e p t i o n may have deve lopmenta l i m p o r t a n c e . R o t h b a r t c o n c e i v e d o f temperament as i n d i v i d u a l d i f f e r e n c e s i n the r e a c t i v i t y and s e l f - r e g u l a t i o n o f b e h a v i o u r a l , e n d o c r i n e , 20 autonomic , and c e n t r a l nervous system responses ( G o l d s m i t h e t a l . , 1987) . These c h a r a c t e r i s t i c s were b e l i e v e d t o show up as d i f f e r e n c e s i n t h r e s h o l d , l a t e n c y , i n t e n s i t y , r i s e t i m e , and r e c o v e r y t ime f o r the e lements o f n e g a t i v e r e a c t i v i t y , p o s i t i v e r e a c t i v i t y , b e h a v i o u r a l i n h i b i t i o n t o n o v e l o r i n t e n s e s t i m u l i , and c a p a c i t y thr ough e f f o r t t o focus and s h i f t a t t e n t i o n . G o l d s m i t h ' s f o r m u l a t i o n a l s o emphasized v a r i a b l e s such as l a t e n c y and d u r a t i o n but p r e d i c t e d the independence o f these parameters f o r each o f the p r i m a r y emotions ( G o l d s m i t h e t a l . , 1987) . Kagan (1992) s t u d i e d i n f a n t s ' b e h a v i o u r a l re sponses t o u n f a m i l i a r s t i m u l i and i d e n t i f i e d subgroups a t the extremes o f the p o p u l a t i o n d i s t r i b u t i o n . The x i n h i b i t e d ' group showed a p a t t e r n o f min imal motor a c t i v i t y and l i t t l e c r y i n g ; the 1 u n i n h i b i t e d ' group showed c o n s i s t e n t l y h i g h motor a c t i v i t y and v i g o u r o u s c r y i n g . These p r o f i l e s were p r e s e r v e d from age 2 t o age 8 and were a s s o c i a t e d w i t h p e r i p h e r a l 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 i m p l y i n g s t a b l e v a r i a t i o n s i n the t h r e s h o l d o f t h e l i m b i c system i n response t o n o v e l and c h a l l e n g i n g events (Kagan & Snidman, 1991) . S i m i l a r l y , M i c h a e l Lewis has i d e n t i f i e d s t a b l e i n d i v i d u a l d i f f e r e n c e s i n i n f a n t s ' r e a c t i v i t y t o s t r e s s f u l s t i m u l i (1992) . He found t h a t the i n t e n s i t y o f an i n f a n t ' s i n i t i a l v o c a l and f a c i a l response t o h e e l s t i c k as a newborn p r e d i c t e d the same i n f a n t ' s f a c i a l and v o c a l r e a c t i o n t o immuniza t ion a t 2 months o f age . An i n f a n t ' s l a t e n c y t o q u i e t f o l l o w i n g each p r o c e d u r e was a l s o s t a b l e a c r o s s t i m e . Lewis i n t e r p r e t e d the 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 b e h a v i o u r a l response as r e f l e c t i o n s 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 t h r e s h o l d and dampening a t the l e v e l o f 21 the nervous sys tem. He a l s o sugges ted t h a t such parameters u n d e r l i e the c o n s t r u c t o f temperament ( L e w i s , 1992) . I t s h o u l d be noted t h a t n e g a t i v e e m o t i o n a l i t y and the e x p r e s s i o n o f d i s t r e s s i s c e n t r a l i n a l l o f the above c o n c e p t i o n s . In Chess and Thomas' framework, a p p r o a c h , a d a p t a b i l i t y , mood, and i n t e n s i t y a l l t apped i n t o n e g a t i v e e m o t i o n a l i t y (1977) . Buss and P l o m i n ' s E m o t i o n a l i t y f a c t o r (1984) , B a t e s ' F u s s y / D i f f i c u l t f a c t o r (1979) , and R o t h b a r t ' s N e g a t i v e R e a c t i v i t y ( G o l d s m i t h e t a l . , 1987) seem t o be measur ing the same c o n s t r u c t . The s t u d i e s by Kagan (1992) and Lewis (1992) l i k e n i n g temperament t o p s y c h o b i o l o g i c a l re sponses have f o c u s e d on b e h a v i o u r a l e x p r e s s i o n s o f d i s t r e s s such as c r y , f a c i a l e x p r e s s i o n , and motor a c t i v i t y . N e g a t i v e e m o t i o n a l i t y i s a l s o o f c o n c e r n i n c l i n i c a l and t h e o r e t i c a l r e s e a r c h on a d u l t p o p u l a t i o n s . L a r s e n and D i e n e r (1987) rev iewed the l i t e r a t u r e and c o n c l u d e d t h a t a d u l t temperament has f o u r major d i m e n s i o n s : e m o t i o n a l i t y , a c t i v i t y l e v e l , s o c i a b i l i t y / e x t r a v e r s i o n , and sensory a r o u s a b i l i t y . C l i n i c a l l y , e m o t i o n a l s t a b i l i t y has been found t o p r e d i c t p s y c h o l o g i c a l d i s t r e s s and p s y c h o l o g i c a l w e l l - b e i n g i n a d u l t s u b j e c t s ( W i n d l e , 1989) . The Normat ive A g i n g Study o f Bos ton v e t e r a n s demonstrated t h a t e m o t i o n a l i t y accounted f o r a p p r o x i m a t e l y 23% o f the v a r i a n c e i n menta l h e a l t h s t a t u s 10 y e a r s l a t e r (Levenson , A l d w i n , Bosse & S p i r o , 1988) . Levenson and h i s c o l l e a g u e s used t h i s f i n d i n g t o argue f o r a g e n e r a l c o n s t r u c t o f n e g a t i v e a f f e c t i v i t y t h a t i s r e l a t i v e l y s t a b l e o v e r t i m e . 22 The s t r u c t u r e o f t h e o r i e s o f c h i l d and a d u l t temperament, and s t u d i e s 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 p h y s i o l o g i c a l r e a c t i v i t y converge on the f o l l o w i n g h y p o t h e s i s : i n d i v i d u a l d i f f e r e n c e s i n b e h a v i o u r a l responses t o s t r e s s a r e an i n t e g r a l p a r t o f the c o n s t r u c t o f temperament, and these d i f f e r e n c e s a r e b e h a v i o u r a l m a n i f e s t a t i o n s 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 p s y c h o b i o l o g i c a l re sponses t o s t r e s s . These r e l a t i o n s h i p s have been most s t u d i e d f o r the temperamental d imens ion o f e m o t i o n a l i t y . Assuming t h a t p a i n i s an example o f n e g a t i v e e m o t i o n a l i t y , i t was h y p o t h e s i z e d 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 an i n f a n t ' s response t o p a i n f u l s t i m u l i would be r e l a t e d t o the c h i l d ' s temperamental p r o f i l e . S p e c i f i c a l l y , i n f a n t s h i g h on n e g a t i v e e m o t i o n a l i t y were p r e d i c t e d t o show the most i n t e n s e p a i n r e s p o n s e . In the p r e s e n t s t u d y , temperament i s seen as a s e t o f i n d i v i d u a l d i f f e r e n c e f a c t o r s which appear e a r l y i n l i f e and are r e l a t i v e l y s t a b l e . These f a c t o r s r e s u l t i n c h a r a c t e r i s t i c s t y l e s o f e x p r e s s i o n r e l a t i n g t o a c t i v i t y , r e a c t i v i t y , e m o t i o n a l i t y , and s o c i a b i l i t y . These s t y l e s o f e x p r e s s i o n may r e f l e c t i n d i v i d u a l d i f f e r e n c e s i n p s y c h o b i o l o g i c a l r e a c t i o n s t o s t i m u l i , e s p e c i a l l y i n r e g a r d s t o s t i m u l i p r o v o k i n g n e g a t i v e e m o t i o n a l i t y . The f i n d i n g t h a t b e h a v i o u r a l e x p r e s s i o n s o f p a i n a r e p o s i t i v e l y r e l a t e d t o s c o r e s on a measure o f n e g a t i v e e m o t i o n a l i t y would suggest 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 the p a i n response a r e r e l a t e d t o a s t a b l e t r a i t apparent a c r o s s d i v e r s e s i t u a t i o n s . Temperament was measured u s i n g the I n f a n t C h a r a c t e r i s t i c s Q u e s t i o n n a i r e ( ICQ; Bates e t a l . , 1979) . The ICQ i s one o f the f i v e most p o p u l a r q u e s t i o n n a i r e s e r i e s used t o measure temperament i n the U n i t e d S t a t e s ( G o l d s m i t h & R i e s e r - D a n n e r , 23 1990) . I t has s e p a r a t e forms f o r i n f a n t s aged about 6, 13, and 24 months, and d a t a sugges t s t h a t the d i f f e r e n t v e r s i o n s a r e comparable ( B a t e s , 1992) . The ICQ was chosen because i t has good p s y c h o m e t r i c p r o p e r t i e s on the n e g a t i v e e m o t i o n a l i t y ( F u s s y / D i f f i c u l t ) f a c t o r , compared t o o t h e r temperament q u e s t i o n n a i r e s ( H u b e r t , Wachs, P e t e r s - M a r t i n & Gandour , 1982) . Reviewers have recommended u s i n g the ICQ i n s t u d i e s where the major g o a l i s c o r r e l a t e s o f d i f f i c u l t temperament (Hubert e t a l . , 1982) . In a d d i t i o n , i t i s b r i e f and r e l a t i v e l y a g e - a p p r o p r i a t e . The 6 month form i s recommended f o r use w i t h i n f a n t s aged aged 4-7 months. The d e c i s i o n t o use i t w i t h 2 month o l d i n f a n t s i n the p r e s e n t s t u d y was j u s t i f i e d based on e x a m i n a t i o n o f the i t e m s . The o n l y i t em t h a t may be i n a p p r o p r i a t e f o r v e r y young i n f a n t s concerns t h e i r r e a c t i o n t o s o l i d f o o d , and t h i s i t em does not c o n t r i b u t e t o the F u s s y / D i f f i c u l t f a c t o r . The ICQ has been used p r e v i o u s l y w i t h i n f a n t s i n t h i s age range ( e . g . , Anderson & C o l l , 1989; L e s t e r & B o u k y d i s , 1992) . The d e c i s i o n t o use t h e 13 month form f o r i n f a n t s aged 12 2 18 months was a l s o based on e x a m i n a t i o n o f the i t e m s . S e v e r a l i n v e s t i g a t o r s have examined the l i n k between temperament and p a i n i n o l d e r c h i l d r e n . D a v i s o n , F a u l l and N i c o l (1986) found t h a t i n a sample o f 6 y e a r o l d c h i l d r e n , boys who s u f f e r e d from r e c u r r e n t abdominal p a i n s c o r e d h i g h e r on a measure o f temperamental d i f f i c u l t y than boys who d i d not r e p o r t r e c u r r e n t p a i n . The r e l a t i o n s h i p was not s i g n i f i c a n t among g i r l s . Young and Fu (1988) s t u d i e d c h i l d r e n aged 4 t o 7 u n d e r g o i n g f i n g e r s t i c k o r v e n i p u n c t u r e . Scores on t h e R h y t h m i c i t y and Approach d imens ions o f a q u e s t i o n n a i r e d e v e l o p e d 24 by Thomas and Chess (1977) were r e l a t e d t o some f a c e t s o f s u b j e c t i v e and b e h a v i o u r a l response t o the m e d i c a l p r o c e d u r e s . However, the r e l a t i o n s h i p s , w h i l e s i g n i f i c a n t , were ex treme ly s m a l l . W a l l a c e (1989) l o o k e d a t c h i l d r e n between the ages o f 3 and 7 u n d e r g o i n g e l e c t i v e s u r g e r y i n v o l v i n g the u r i n a r y sys tem. C h i l d r e n r a t e d as h i g h on an e m o t i o n a l i n t e n s i t y f a c t o r r e c e i v e d a s i g n i f i c a n t l y g r e a t e r number o f p o s t o p e r a t i v e a n a l g e s i c m e d i c a t i o n s than c h i l d r e n r a t e d as low i n t e n s i t y . S c h e c h t e r , B e r n s t e i n , Beck , H a r t and S c h e r z e r (1991) found t h a t i n a sample o f 5 y e a r o l d s r e c e i v i n g i m m u n i z a t i o n s , c h i l d r e n r a t e d as t emperamenta l ly d i f f i c u l t had h i g h e r s c o r e s on o b s e r v e r r a t i n g s o f p a i n . The i n d i v i d u a l temperamental d imens ion o f a d a p t a b i l i t y was a l s o p r e d i c t i v e o f b e h a v i o u r a l d i s t r e s s . In summary, s t u d i e s w i t h o l d e r c h i l d r e n were c o n s i s t e n t w i t h the n o t i o n t h a t h i g h s c o r e s on temperament s c a l e s measur ing n e g a t i v e e m o t i o n a l i t y p r e d i c t g r e a t e r b e h a v i o u r a l re sponses t o p a i n . I t s h o u l d be noted t h a t temperament i s c o n s i d e r e d t o be more p r e d i c t i v e o f b e h a v i o u r i n i n f a n c y , because t h e e f f e c t s o f s o c i a l i z a t i o n a r e fewer . C o n s e q u e n t l y , the r e l a t i o n s h i p between temperament and p a i n re sponse i n i n f a n c y was h y p o t h e s i z e d t o be s t r o n g e r t h a n t h a t seen i n o l d e r c h i l d r e n . Deve lopmenta l Changes i n the E x p r e s s i o n o f P a i n Much o f the l i t e r a t u r e on i n f a n t p a i n concerns neonate s , and t h e r e i s a need t o extend t h e knowledge base t o o l d e r i n f a n t s . I f t h e r e a r e deve lopmenta l changes i n the e x p r e s s i o n o f p a i n , the i n c o r p o r a t i o n o f age i n t o n o r m a t i v e d a t a f o r measures c o u l d r e s u l t i n i n c r e a s e d a c c u r a c y . Some a g e - r e l a t e d changes i n p a i n response have been i d e n t i f i e d . U s i n g a compos i te measure o f 25 f a c i a l e x p r e s s i o n and c r y , Lewis and Thomas (1990) found t h a t 6- month o l d i n f a n t s q u i e t e d f a s t e r t h a n 2- o r 4-month o l d s f o l l o w i n g DPT i m m u n i z a t i o n . S i m i l a r l y , M a i k l e r (1991) found t h a t , f o l l o w i n g i n o c u l a t i o n , the d u r a t i o n o f p a i n e x p r e s s i o n (as measured by the MAX f a c i a l e x p r e s s i o n o f p h y s i c a l d i s t r e s s , c r y , and body movement) was l o n g e r i n i n f a n t s under 4 months t h a n i n i n f a n t s o v e r 4 months. C r a i g e t a l . (1984) noted deve lopmenta l changes i n b e h a v i o u r f o l l o w i n g an immuniza t ion i n j e c t i o n . I n f a n t s under 12 months o f age showed a d i f f u s e response w h i l e i n f a n t s aged 12 t o 24 months demonstrated more g o a l - d i r e c t e d b e h a v i o u r . However, i n the above s t u d i e s , f a c i a l e x p r e s s i o n s were no t s t u d i e d i n d e t a i l . I z a r d e t a l . (1983) used A f f e x t o code the f a c i a l re sponse t o immuniza t ion i n i n f a n t s aged 2 t o 19 months. I t was found t h a t o l d e r i n f a n t s d i s p l a y e d the * p h y s i c a l d i s t r e s s ' e x p r e s s i o n f o r a s m a l l e r p r o p o r t i o n o f t i m e , and d i s p l a y e d anger and b l e n d e d e x p r e s s i o n s f o r l o n g e r p r o p o r t i o n s . T h i s f i n d i n g was l a t e r r e p l i c a t e d w i t h a l o n g i t u d i n a l sample ( I z a r d e t a l . , 1987) . However, i n the A f f e x sys tem, c o d e r s compare observed appearance changes t o formulas o r t e m p l a t e s r e p r e s e n t i n g s p e c i f i c emot ions . A f f e x i s not s e n s i t i v e t o changes i n the i n d i v i d u a l a c t i o n s making up a g i v e n e x p r e s s i o n , and a more m o l e c u l a r c o d i n g sys tem, such as NFCS o r Baby F A C S , i s needed t o p r o v i d e a d e t a i l e d d e s c r i p t i o n o f deve lopmenta l changes . O s t e r , Heg ley and Nage l (1992) p o i n t e d out t h a t i n the A f f e x sys tem, the d i s t r e s s - p a i n and anger e x p r e s s i o n s a r e v e r y s i m i l a r . In f a c t , the o n l y d i f f e r e n c e between the two i s t h a t the eyes a r e c l o s e d f o r d i s t r e s s - p a i n and open f o r a n g e r . C o n s e q u e n t l y , t h e 26 r e s u l t s o f I z a r d e t a l . ' s (1987) s tudy i n d i c a t e d t h a t o l d e r i n f a n t s open t h e i r eyes immedia te ly a f t e r the s h o t , w h i l e younger i n f a n t s keep them c l o s e d . C r a i g and Grunau (1993) noted t h a t the o n l y major d i f f e r e n c e between the e x p r e s s i o n o f p a i n i n newborns and i n a d u l t s i s t h a t newborns c h a r a c t e r i s t i c a l l y squeeze t h e i r eyes s h u t . C r a i g went on t o argue t h a t t h i s may be an a d a p t i v e d i f f e r e n c e , r e f l e c t i n g the f a c t t h a t a d u l t s can use v i s u a l i n f o r m a t i o n t o p r o t e c t themse lves from t h e source o f p a i n , w h i l e i n f a n t s have no such r e c o u r s e . T h u s , the changes i n the a f f e c t i v e response i d e n t i f i e d by I z a r d e t a l . (1983) may a l s o be r e a s o n a b l y i n t e r p r e t e d as r e f l e c t i n g v a r i a t i o n i n the e x p r e s s i o n o f p a i n . O t h e r s have sugges ted t h a t these changes r e f l e c t d i f f e r e n t i n t e n s i t i e s o f d i s t r e s s r a t h e r t h a n d i s t i n c t emotions (Camras, S u l l i v a n , & M i c h e l , 1993) . Such debate i s not s u r p r i s i n g , g i v e n t h a t o p i n i o n s d i f f e r on whether i n f a n t s e x p e r i e n c e d i s t i n c t n e g a t i v e emotions o r u n d i f f e r e n t i a t e d d i s t r e s s (Camras e t a l . , 1993) . Grunau and C r a i g ' s c o d i n g system has uncovered some response d i f f e r e n c e s r e l a t e d t o age . Premature i n f a n t s u n d e r g o i n g h e e l l a n c e d i s p l a y e d l e s s t o t a l f a c i a l a c t i v i t y t h a n f u l l t e r m i n f a n t s exposed t o the same s t i m u l u s ( C r a i g e t a l . , 1993) . J o h n s t o n e t a l . , (1993) compared (1) premature i n f a n t s o f 32 t o 34 weeks g e s t a t i o n a l age u n d e r g o i n g h e e l l a n c e , (2) f u l l t e r m neonates u n d e r g o i n g i n t r a m u s c u l a r v i t a m i n K i n j e c t i o n , (3) 2- and 4-month- o l d i n f a n t s u n d e r g o i n g subcutaneous i n j e c t i o n o f the d i p h t h e r i a - p e r t u s s i s - t e t a n u s v a c c i n e . Pre term i n f a n t s were found t o d i s p l a y more h o r i z o n t a l mouth s t r e t c h than 2- and 4-month o l d i n f a n t s , but l e s s t a u t tongue than newborns. F u l l t e r m newborns showed 27 more h o r i z o n t a l mouth s t r e t c h than o l d e r i n f a n t s , and more t a u t tongue t h a n any o f the o t h e r g r o u p s . The 2- and 4- month o l d i n f a n t s showed s i m i l a r r e s p o n s e s , and t h e r e were no o t h e r f a c i a l d i f f e r e n c e s among g r o u p s . Deve lopmenta l changes deserve more a t t e n t i o n . Summary and Hypotheses The p r e s e n t s tudy examined the bases 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 i n f a n t s ' response t o p a i n . C r o s s - s e c t i o n a l samples o f i n f a n t s were observed u n d e r g o i n g immunizat ions a t 2, 4, 6, 12, and 18 months o f age . R a t i n g s o f p a i n based on f a c i a l e x p r e s s i o n were r e l a t e d t o age and p a r e n t r e p o r t o f temperament. F o r the most p a r t , t h e a n a l y s i s o f deve lopmenta l changes was d e s c r i p t i v e , s i n c e the deve lopmenta l c o u r s e o f the f a c i a l e x p r e s s i o n o f p a i n has g e n e r a l l y no t been s t u d i e d w i t h d e t a i l e d c o d i n g sys tems . However, i t was p r e d i c t e d t h a t a t o l d e r ages , i n f a n t s would keep t h e i r eyes open f o l l o w i n g the i n j e c t i o n . I t was a l s o h y p o t h e s i z e d t h a t compos i te p a i n r a t i n g s would be p o s i t i v e l y r e l a t e d t o s c o r e s on a measure o f the n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament as r e p o r t e d by p a r e n t s . 28 METHOD S e t t i n g The s tudy was conducted a t c h i l d h e a l t h c l i n i c s r u n by the West -Main and South U n i t s o f the Vancouver H e a l t h Department . The c l i n i c s f u n c t i o n as d r o p - i n c e n t r e s f o r p a r e n t s and young c h i l d r e n , where the c h i l d r e n can be weighed and measured, and p a r e n t s have an o p p o r t u n i t y t o speak t o community h e a l t h n u r s e s about any concerns they may have . P a r e n t s a l s o made appointments f o r immunizat ions on c e r t a i n d a y s . There were f o u r c l i n i c s i n a l l , s e r v i n g areas o f v a r i e d e t h n i c c o m p o s i t i o n and soc ioeconomic s t a t u s . Two o r t h r e e n u r s e s s t a f f e d each c l i n i c , w i t h a t o t a l o f 11 d i f f e r e n t nurse s who a d m i n i s t e r e d i m m u n i z a t i o n s . Sample A c c o r d i n g t o the g u i d e l i n e s o f the Canad ian M e d i c a l A s s o c i a t i o n (Canadian Immunizat ion G u i d e , 1989) , i n f a n t s s h o u l d r e c e i v e subcutaneous i n j e c t i o n s f o r immunizat ion a g a i n s t d i p h t h e r i a , p e r t u s s i s and t e t a n u s (DPT) , as w e l l as Haemophilus i n f l u e n z a e type b (Hib) a t 2, 4, 6, and 18 months o f age . P r i o r t o J u l y 1994, these v a c c i n e s were g i v e n as two s e p a r a t e i n j e c t i o n s , each 0.5 c c i n volume; one shot was a d m i n i s t e r e d i n each t h i g h . A f t e r J u l y 1994, these v a c c i n e s were combined i n t o a s i n g l e s h o t , 0.5 c c . i n volume, a d m i n i s t e r e d i n the t h i g h . A t 12 months o f age , the g u i d e l i n e s recommend t h a t i n f a n t s r e c e i v e an i n t r a m u s c u l a r i n j e c t i o n > 0.5 c c . i n volume, a d m i n i s t e r e d i n the upper arm, as p r o t e c t i o n a g a i n s t meas l e s , mumps and r u b e l l a (MMR). In the p r e s e n t s t u d y we examined i n f a n t s i n each o f the age groups s u b j e c t e d t o these p r o c e d u r e s . 29 A conven ience method o f sampl ing was u s e d . Between J a n u a r y 1994 and A p r i l 1995, i n f a n t s who met the i n c l u s i o n c r i t e r i a p a r t i c i p a t e d i n the s t u d y . Sampl ing c o n t i n u e d u n t i l d a t a from 15 i n f a n t s had been c o l l e c t e d f o r each age g r o u p . The i n c l u s i o n c r i t e r i a were as f o l l o w s : 1. I n f a n t s r e c e i v e d i n j e c t i o n s w i t h i n 31 days o f the median age f o r a g i v e n s h o t ; 2. A p a r e n t who spoke and r e a d E n g l i s h accompanied the i n f a n t . 3 . The p a r e n t accompanying the i n f a n t agreed t o have the c h i l d p a r t i c i p a t e i n the s t u d y . R e f u s e r s and i n f a n t s e x c l u d e d from the s t u d y Of the 102 p a r e n t s approached by a c l i n i c nurse t o p a r t i c i p a t e i n the s t u d y , 79 (77%) agreed t o take p a r t . A l t h o u g h the reasons f o r d e c l i n i n g were no t f o r m a l l y a s s e s s e d , s e v e r a l p a r e n t s s t a t e d t h a t they themse lves were a f r a i d o f need le s o r found the immuniza t ion s t r e s s f u l , and c o n s e q u e n t l y they " j u s t wanted t o ge t i t over w i t h . " O t h e r s e x p r e s s e d c o n c e r n t h a t q u e s t i o n n a i r e c o m p l e t i o n would t a k e too l o n g . Two i n f a n t s were e x c l u d e d because they were g i v e n t h e wrong q u e s t i o n n a i r e package ( i . e . 18 -month-o ld i n f a n t s were g i v e n the " 6 m o n t h " v e r s i o n o f the q u e s t i o n n a i r e ) , two i n f a n t s were e x c l u d e d because v e r y l i t t l e o f t h e i r f a c i a l e x p r e s s i o n was v i s i b l e on the v i d e o t a p e . I t i s no t p o s s i b l e t o r u l e out the h y p o t h e s i s t h a t p a r e n t s who knew t h a t t h e i r i n f a n t s r e a c t e d p a r t i c u l a r l y v i o l e n t l y t o i n j e c t i o n s d e c l i n e d t o p a r t i c i p a t e i n the s t u d y o r d e l a y e d i n b r i n g i n g the c h i l d r e n t o be immunized such t h a t they d i d not meet age c r i t e r i a . 30 A p p a r a t u s A h a n d - h e l d c o l o u r v i d e o camera was used t o r e c o r d t h e i n f a n t s ' f a c i a l b e h a v i o u r . Two cameras were used i n the c o u r s e o f the s t u d y , the f i r s t a Sony CCD-TR81 HandyCam, the second a M i n o l t a Mas ter S e r i e s V18R. A Panason ic WJ-810 t i m e - d a t e g e n e r a t o r was used t o superimpose a d i g i t a l t ime d i s p l a y on the v i d e o so t h a t s p e c i f i c t ime segments c o u l d be s e l e c t e d and c o d e d . A JVC 2 0 " c o l o u r m o n i t o r (AV-20CM4) and a P a n a s o n i c v i d e o c a s s e t t e r e c o r d e r (AG-1970P) w i t h remote c o n t r o l , s t o p a c t i o n and s low mot ion feedback were used d u r i n g v i d e o c o d i n g . Procedure Once in formed consent was o b t a i n e d , the immunizat ion p r o c e s s began. In each c l i n i c , i t was c a r r i e d out i n a s m a l l room a d j a c e n t t o the w a i t i n g room. I n f a n t s were s e a t e d on t h e i r p a r e n t ' s l a p w h i l e t h e nurse swabbed the s k i n w i t h a l c o h o l t o c l e a n s e i t , and a d m i n i s t e r e d the i n j e c t i o n . I n f a n t s i n t h e 2, 4, 6, and 18 month age groups r e c e i v e d the s h o t s i n the t h i g h . I n f a n t s i n the 12 month age group r e c e i v e d the s h o t i n the arm. I f the i n f a n t was r e c e i v i n g two i n j e c t i o n s ( i . e . the s t a n d a r d p r o t o c o l f o r DPT and H i b i n j e c t i o n s p r i o r t o J u l y , 1994) , t h e nurse q u i c k l y t u r n e d the i n f a n t a f t e r the f i r s t i n j e c t i o n and a d m i n i s t e r e d the second s h o t i n the c o n t r a l a t e r a l t h i g h . Throughout the e n t i r e p r o c e d u r e , v i d e o r e c o r d i n g was c a r r i e d out by a t e c h n i c i a n , who f o c u s s e d the camera on the i n f a n t ' s f a c e . The nurse i n d i c a t e d the moment when the need le p e n e t r a t e d the s k i n by s a y i n g "Now." F o l l o w i n g the i m m u n i z a t i o n , p a r e n t s were r e q u i r e d t o remain i n the w a i t i n g room f o r 15 minutes t o ensure t h e i r c h i l d d i d no t 31 e x p e r i e n c e an adverse r e a c t i o n t o the v a c c i n e . D u r i n g t h i s p e r i o d , t h e y were g i v e n a package c o n t a i n i n g (1) q u e s t i o n s about b a s i c demographic i n f o r m a t i o n and o t h e r f a c t o r s t h a t may have i n f l u e n c e d the i n f a n t ' s r e s p o n s e , such as t ime s i n c e waking and t ime s i n c e l a s t f e e d i n g , and (2) the I n f a n t C h a r a c t e r i s t i c s Q u e s t i o n n a i r e ( ICQ; B a t e s , 1992) . The p a r e n t s o f i n f a n t s aged 2- 6 months were g i v e n the "6 month" form; the p a r e n t s o f i n f a n t s aged 12-18 months were g i v e n the "13 month" f o r m . The package t y p i c a l l y took l e s s t h a n 15 minutes t o c o m p l e t e . See Append ice s A and B f o r c o p i e s o f the background c h a r a c t e r i s t i c s q u e s t i o n n a i r e and sample i tems from the ICQ. I t would have been p r e f e r a b l e t o have p a r e n t s complete the temperament q u e s t i o n n a i r e b e f o r e the immuniza t ion p r o c e d u r e , i n o r d e r t o a v o i d t h e p o s s i b i l i t y t h a t t h e i r re sponses were b i a s e d by t h e i r o b s e r v a t i o n s o f the c h i l d d u r i n g the i n j e c t i o n . However, the c l i n i c s t a f f found t h a t t h i s i n t e r f e r e d w i t h t h e n u r s e s ' d u t i e s , and asked t h a t the q u e s t i o n n a i r e be comple ted d u r i n g t h e 15 minute w a i t i n g p e r i o d . T h e . i n s t r u c t i o n s on t h e q u e s t i o n n a i r e s t a t e d "Please base your answers on how y o u r baby u s u a l l y r e a c t s , not on how your baby r e a c t e d t o t o d a y ' s s h o t . " Means on the temperament s c a l e were compared t o a v a i l a b l e norms i n o r d e r t o de termine whether w i t n e s s i n g the i n j e c t i o n a l t e r e d mothers ' p e r c e p t i o n s o f temperament. C o d i n g o f I n f a n t s ' F a c i a l A c t i o n s Two systems were used t o p r o v i d e d e t a i l e d d e s c r i p t i o n s o f f a c i a l a c t i v i t y : the N e o n a t a l F a c i a l C o d i n g System (NFCS; Grunau & C r a i g , 1990) and an a d a p t a t i o n o f the F a c i a l A c t i o n C o d i n g System (FACS; Ekman & F r i e s e n , 1978) i n t e n d e d f o r use w i t h 32 i n f a n t s (Baby FACS; O s t e r & R o s e n s t e i n , 1982, 1993) . See Appendices C 2 D f o r d e t a i l e d d e s c r i p t i o n s o f the c o d i n g sys tems . Each f a c i a l a c t i o n d e s c r i b e d f o r NFCS o r Baby FACS was s c o r e d as p r e s e n t o r absent d u r i n g f i v e s u c c e s s i v e 2 -second segments coded f o r each o f t h r e e events ( " b a s e l i n e , " " i n j e c t i o n , " and " r e c o v e r y " ) . Baby FACS c o d i n g a l s o a s s i g n s an i n t e n s i t y s c o r e (1-5) t o each o f t h e a c t i o n s p r e s e n t . In a d d i t i o n t o t h e f a c i a l a c t i o n u n i t s , the Baby FACS system i n c l u d e s the o p t i o n o f c o d i n g head and eye p o s i t i o n . T h i s was not done i n the p r e s e n t s t u d y as t h e r e i s no e m p i r i c a l o r i n t u i t i v e r e a s o n t h i s would be r e l a t e d t o p a i n , and as i t g r e a t l y i n c r e a s e s the t ime r e q u i r e d t o code an e v e n t . Coders were a b l e t o use s low mot ion and s t o p frame f eedback . The segments on each tape were coded i n random o r d e r . The c o d e r s were b l i n d t o the temperament s c o r e s and e x a c t age o f the i n f a n t s . NFCS c o d i n g was c a r r i e d out by two t r a i n e d c o d e r s who had demonstrated h i g h l e v e l s o f i n t e r - r a t e r r e l i a b i l i t y . Baby FACS c o d i n g was c a r r i e d out by a s i n g l e t r a i n e d c o d e r c e r t i f i e d a c c o r d i n g t o the FACS p r o f i c i e n c y t e s t (Ekman & F r i e s e n , 1978) . Scores f o r each a c t i o n u n i t were summed over f i v e 2 - second segments f o r each e v e n t . On ly those a c t i o n u n i t s observed i n more t h a n 10% o f 2 - second segments were a n a l y z e d . By c u r r e n t c o n v e n t i o n s (Ekman & F r i e s e n , 1992) , b o t h A d u l t FACS and Baby FACS a r e coded on an i n t e n s i t y d i m e n s i o n , a s c a l e which ranges from 0-5 . These s c o r e s were then summed over the 5-second segments o f each event i n o r d e r t o d e r i v e a s i n g l e v a l u e f o r each a c t i o n . T o t a l s c o r e s c o u l d range from 0 (no a c t i o n ) t o 25 ( a c t i o n o c c u r s a t the h i g h e s t l e v e l o f i n t e n s i t y i n e v e r y 33 segment) . As a r e s u l t , the Baby FACS s c o r e s i n the c u r r e n t a n a l y s i s a r e i n f l u e n c e d by the i n t e n s i t y o f a c t i o n s as w e l l as t h e i r f r e q u e n c y . T h i s w i l l s e r v e t o l e s s e n t h e c o m p a r a b i l i t y o f NFCS and Baby FACS; however, b o t h systems were i n c l u d e d i n the p r e s e n t s t u d y w i t h the i n t e n t t o o b t a i n d i f f e r e n t t y p e s o f i n f o r m a t i o n , r a t h e r t h a n t o compare the two d i r e c t l y . F o r each o f NFCS and FACS, a s econdary coder s c o r e d 25% o f the segments i n o r d e r t o de termine i n t e r r a t e r r e l i a b i l i t y . R e l i a b i l i t y was c a l c u l a t e d a c c o r d i n g t o t h e f o r m u l a g i v e n by Ekman and F r i e s e n (1978) which a s se s se s t h e p r o p o r t i o n o f agreement on a c t i o n s r e c o r d e d by two c o d e r s r e l a t i v e t o the t o t a l number o f a c t i o n s c o d e d . The r e s u l t i n g f i g u r e s were 0.89 f o r NFCS and 0.80 f o r Baby FACS. S i n c e , as e x p e c t e d , o n l y a s m a l l p r o p o r t i o n o f Baby FACS a c t i o n s met the c r i t e r i a f o r i n c l u s i o n i n the f i n a l a n a l y s i s , r e l i a b i l i t y was a l s o c a l c u l a t e d on these a c t i o n s a l o n e . A c c o r d i n g t o t h i s p r o c e d u r e , r e l i a b i l i t y r e a c h e d 0 .88 . I n t e n s i t y s c o r i n g f o r each o f the agreed upon Baby FACS AUs was c o r r e l a t e d , y i e l d i n g a Pearson product-moment c o e f f i c i e n t o f 0 .88 . The f o l l o w i n g 10 second segments were Coded whenever p o s s i b l e : (1) a b a s e l i n e p e r i o d b e g i n n i n g 30 seconds p r i o r t o the f i r s t i n j e c t i o n , (2) r e a c t i o n t o the f i r s t i n j e c t i o n , and (3) a r e c o v e r y p e r i o d b e g i n n i n g 20 seconds a f t e r the l a s t i n j e c t i o n . However, the f o l l o w i n g e x c e p t i o n s a r o s e : S e l e c t i o n o f the " b a s e l i n e " event The " b a s e l i n e " event was i n c l u d e d i n t h e a n a l y s i s as a c o n t r o l , showing the i n f a n t s ' f a c i a l a c t i o n s d u r i n g a p e r i o d when no i n v a s i v e events a r e t a k i n g p l a c e . I t s h o u l d be noted t h a t 34 i n f a n t s w i l l be s u b j e c t e d t o some n o n - i n v a s i v e t a c t i l e s t i m u l a t i o n d u r i n g t h i s p e r i o d as t h e y a r e t y p i c a l l y b e i n g undressed and p o s i t i o n e d f o r the i n j e c t i o n a t t h i s t i m e . A "true" b a s e l i n e p e r i o d was found t o s low down t h e . n u r s e s c o n s i d e r a b l y and i n t e r f e r e w i t h the p r i m a r y f u n c t i o n s o f t h e c l i n i c . Whenever p o s s i b l e , a s e c t i o n o f v i d e o t a p e from 30-20 seconds b e f o r e the f i r s t i n j e c t i o n was s e l e c t e d as a " b a s e l i n e " e v e n t . T h i s was p o s s i b l e f o r 51 (68%) i n f a n t s . However, f o r 24 (32%) i n f a n t s , t h e r e was l e s s t h a n 30 seconds o f v i d e o t a p e p r i o r t o the i n j e c t i o n . C o n s e q u e n t l y , f o r 8 (10.7%) i n f a n t s the " b a s e l i n e " event o c c u r r e d from 20-10 seconds b e f o r e the f i r s t i n j e c t i o n . F o r another 11 (14.7%) i n f a n t s the " b a s e l i n e " event o c c u r r e d from 10 seconds b e f o r e the f i r s t i n j e c t i o n up t o the i n j e c t i o n . The " n o b a s e l i n e " segment was m i s s i n g c o m p l e t e l y f o r 5 (6.7%) i n f a n t s (see " M i s s i n g D a t a " b e l o w ) . There i s no t h e o r e t i c a l r eason t h a t these events s h o u l d d i f f e r i n the f a c i a l a c t i o n s r e f l e c t i v e o f p a i n , as n o t h i n g p a i n f u l i s happening t o the i n f a n t s i n any c a s e . T h i s assumpt ion was t e s t e d by c o n d u c t i n g a one-way MANOVA f o r each o f the c o d i n g sys tems , w i t h the r e l e v a n t f a c i a l v a r i a b l e s as dependent measures and the t e m p o r a l l o c a t i o n o f the " b a s e l i n e " event as the independent v a r i a b l e . N e i t h e r MANOVA was s i g n i f i c a n t (p> .2 ) , and c o n s e q u e n t l y the events were t r e a t e d as e q u i v a l e n t . S e l e c t i o n o f the " r e c o v e r y " e v e n t . The r e c o v e r y event was i n c l u d e d i n o r d e r t o p r o v i d e some i n d i c a t i o n o f the i n f a n t ' s r e a c t i o n over t i m e . O r i g i n a l l y , i t was p l a n n e d t h a t t h i s event would t a k e p l a c e from 20-30 seconds 35 a f t e r the second i n j e c t i o n , i n the case o f i n f a n t s r e c e i v i n g the DPT and H i b v a c c i n e s , and 20-30 seconds a f t e r the f i r s t and o n l y i n j e c t i o n i n the case o f 12 m o n t h - o l d i n f a n t s r e c e i v i n g t h e MMR v a c c i n e . However, i n J u l y o f 1994, the Canadian immuniza t ion g u i d e l i n e s were changed such t h a t t h e DPT and H i b v a c c i n e s were g i v e n i n the same s y r i n g e , and a l l i n f a n t s r e c e i v e d a s i n g l e i n j e c t i o n . F o r these i n f a n t s , as i n the 12-month g r o u p , the " r e c o v e r y " segment was t a k e n from 20-30 seconds a f t e r t h e f i r s t and o n l y i n j e c t i o n . However, t h i s meant t h a t , w i t h i n the same c e l l , i n f a n t s d i f f e r e d i n the number o f i n j e c t i o n s t h e y had r e c e i v e d . Of the t o t a l sample , 49 i n f a n t s (65.3%) had r e c e i v e d one i n j e c t i o n , and 19 (25.3%) had r e c e i v e d two i n j e c t i o n s . The i n f a n t ' s f a c e was not v i s i b l e d u r i n g the " r e c o v e r y " event f o r 7 i n f a n t s (9.3%; see " M i s s i n g D a t a " b e l o w ) . As b e f o r e , the assumpt ion t h a t the two events ( r e c o v e r y a f t e r one shot v e r s u s r e c o v e r y a f t e r two s h o t s ) were e q u i v a l e n t was t e s t e d by c o n d u c t i n g a one-way MANOVA f o r each o f the c o d i n g sys tems , w i t h f a c i a l v a r i a b l e s as dependent measures and the number o f s h o t s as the independent v a r i a b l e . In t h i s c a s e , the MANOVA produced s i g n i f i c a n t r e s u l t s i n t h e case o f the NFCS v a r i a b l e s ( P i l l a i s F ( 5 , 6 2 ) =5.55618, p_<.001) and n e a r l y s i g n i f i c a n t r e s u l t s i n t h e case o f the Baby FACS v a r i a b l e s ( P i l l a i s F ( 1 0 , 4 3 ) = l . 8 2 6 9 7 , p< .10 ) . C o n s e q u e n t l y the two t y p e s o f segments were not t r e a t e d as e q u a l i n f u r t h e r a n a l y s e s . A l t h o u g h i n c o n v e n i e n t a t p r e s e n t , the f i n d i n g o f d i f f e r e n c e s due t o the number o f p a i n f u l s t i m u l i i s an i n t e r e s t i n g one . The t ime c o u r s e o f the p a i n r e a c t i o n has not been s t u d i e d i n g r e a t d e t a i l and t h e i n t e r a c t i o n between t ime and r e p e a t e d p a i n f u l 36 s t i m u l i i s unknown. F o l l o w - u p a n a l y s e s were conducted on the NFCS d a t a , i n the form o f u n i v a r i a t e ANOVAs f o r each o f the f a c i a l a c t i o n s . These a n a l y s e s r e v e a l e d t h a t the d i f f e r e n c e l a y i n t h r e e a c t i o n s : brow b u l g e ( F ( l , 6 6 ) = 1 0 . 8 8 9 1 ; p< .001) , deepened n a s o l a b i a l furrow ( F ( l , 6 6 ) = 5 . 5 8 2 5 ; p< .05) , and t a u t tongue ( F ( l , 6 6 ) = 6 . 4 2 7 4 ; p< .05) : i n f a n t s who had undergone a s i n g l e shot s c o r e d h i g h e r on brow b u l g e and deepened n a s o l a b i a l furrow t h a n d i d i n f a n t s who had undergone two i n j e c t i o n s . In c o n t r a s t , i n f a n t s who had undergone two s h o t s d i s p l a y e d more t a u t tongue t h a n those who had undergone a s i n g l e s h o t . C o d i n g o f P a r e n t s ' S o o t h i n g I n t e r v e n t i o n s In a d d i t i o n t o the c o d i n g o f f a c i a l a c t i o n s , some means o f d e s c r i b i n g p a r e n t s ' e f f o r t s t o soothe the c h i l d were d e s i r e d . The f o l l o w i n g 10 c a t e g o r i e s o f s o o t h i n g i n t e r v e n t i o n s were d e r i v e d from a r e a d i n g o f the l i t e r a t u r e ( B e l l & A i n s w o r t h , 1972; G u s t a f s o n & H a r r i s , 1990; Papousek & Papousek, 1990) and an e x a m i n a t i o n o f p i l o t d a t a . 1) H o l d i n g L a t e r a l l y : Baby i s c r a d l e d o r h e l d f a c e up i n c a r e g i v e r ' s arms o r hands . 2) H o l d i n g V e n t r a l l y : Baby i s h e l d a g a i n s t c a r e g i v e r ' s s h o u l d e r , i n an u p r i g h t p o s i t i o n , w i t h c h e s t toward c a r e g i v e r . 3) Arm R e s t r a i n t : Baby i s h e l d so t h a t n e i t h e r arm i s f r e e t o move, due t o the p o s i t i o n o f the c a r e g i v e r ' s hands , arms, o r t o r s o . 4) V e s t i b u l a r S t i m u l a t i o n : C a r e g i v e r moves baby i n a r h y t h m i c manner ( i n c l u d i n g b o u n c i n g , sway ing , r o c k i n g , o r j i g g l i n g ) . 5) T a c t i l e S t i m u l a t i o n : C a r e g i v e r p a t s , r u b s , t i c k l e s , o r k i s s e s baby , o r s t r o k e s b a b y ' s f a c e , head , hands , e t c . 37 6) B r e a s t F e e d i n g : C a r e g i v e r put s n i p p l e i n b a b y ' s mouth. 7) B o t t l e F e e d i n g : C a r e g i v e r put s n i p p l e i n b a b y ' s mouth. 8) G i v i n g P a c i f i e r : C a r e g i v e r put s p a c i f i e r i n b a b y ' s mouth. 9) D i s t r a c t i o n : C a r e g i v e r a t tempts t o d i v e r t b a b y ' s a t t e n t i o n v e r b a l l y ( e . g . , " L o o k a t t h a t " o r " W h a t ' s she d o i n g ? " ) , o r by p r e s e n t i n g a t o y . 10) S o o t h i n g V o c a l i z a t i o n : C a r e g i v e r speaks t o the baby w i t h a s o o t h i n g tone 2 message ( e . g . , " T h a t ' s O K " o r " A l l f i n i s h e d n o w " ) , o r makes s o o t h i n g sounds ( e . g . , " S h h h h h h " ) . The above a c t i o n s were coded as p r e s e n t o r absent over an i n t e r v a l s t r e t c h i n g from t h e i n i t i a l i n j e c t i o n t o 30 seconds f o l l o w i n g the l a s t i n j e c t i o n g i v e n . T h u s , the d u r a t i o n o f t h i s i n t e r v a l v a r i e d from i n f a n t t o i n f a n t . The p r i m a r y coder was an undergraduate r e s e a r c h a s s i s t a n t . T w e n t y - f i v e p e r c e n t o f the tapes were coded by a s econdary c o d e r i n o r d e r t o de termine r e l i a b i l i t y , which was 0.83 a c c o r d i n g t o Ekman and F r i e s e n ' s f o r m u l a (1978) . A n a l y s e s P r e l i m i n a r y a n a l y s e s . D e s c r i p t i v e s t a t i s t i c s were c o m p i l e d on background c h a r a c t e r i s t i c s o f the sample , and t h e r e l a t i o n s h i p s among background c h a r a c t e r i s t i c s and the independent v a r i a b l e s were examined u s i n g c h i - s q u a r e t e s t s , ANOVAs, and c o r r e l a t i o n c o e f f i c i e n t s , depending on the n a t u r e o f the v a r i a b l e s . S i m i l a r l y , the f r e q u e n c y o f the v a r i o u s s o o t h i n g i n t e r v e n t i o n s e x h i b i t e d by p a r e n t s were t a b u l a t e d , and c h i - s q u a r e t e s t s and ANOVA were used t o de termine whether p a r e n t s a l t e r e d t h e i r b e h a v i o u r a c c o r d i n g t o a c h i l d ' s age and temperament. Next , 38 d e s c r i p t i v e s t a t i s t i c s were c a l c u l a t e d f o r the independent v a r i a b l e s . The r e l a t i o n s h i p among the independent v a r i a b l e s was a s s e s s e d u s i n g a oneway ANOVA. The r e s e a r c h q u e s t i o n s . The d a t a were a n a l y z e d u s i n g SPSS/PC t o answer the r e s e a r c h q u e s t i o n s , w i t h some a d d i t i o n a l hand c a l c u l a t i o n s . A l l a n a l y s e s were conducted s e p a r a t e l y f o r NFCS and Baby FACS. In o r d e r t o d e r i v e a " p a i n summary s c o r e " f o r each c o d i n g sys tem, v a r i a b l e s o c c u r r i n g i n more t h a n 10% o f segments were e n t e r e d i n t o a p r i n c i p a l components a n a l y s i s . F a c t o r l o a d i n g s from t h i s a n a l y s i s were then used as we ights i n a l i n e a r c o m b i n a t i o n o f f a c i a l v a r i a b l e s . T h i s p r o c e d u r e i s c o n s i s t e n t w i t h p r e v i o u s s t u d i e s u s i n g NFCS and Baby FACS ( e . g . , C r a i g e t a l . , 1994) . In o r d e r t o address the r e l a t i o n s h i p between i n f a n t temperament and r e a c t i o n t o the i n j e c t i o n , c o r r e l a t i o n c o e f f i c i e n t s between the p a i n summary s c o r e s and s c o r e s on the f u s s y - d i f f i c u l t d imens ion were examined. As d e s c r i b e d above, r e s u l t s o f p r e l i m i n a r y a n a l y s e s i n d i c a t e d t h a t , f o r the r e c o v e r y e v e n t , i t was no t a p p r o p r i a t e t o t r e a t i n f a n t s r e c e i v i n g two i n j e c t i o n s as e q u i v a l e n t t o t h o s e r e c e i v i n g a s i n g l e i n j e c t i o n . C o n s e q u e n t l y , the a n a l y s i s was h a n d l e d d i f f e r e n t l y than o r i g i n a l l y p l a n n e d . Where i n f a n t s r e c e i v e d two i n j e c t i o n s , the i n t e r v a l between the i n j e c t i o n s was v a r i a b l e ' . In s i x cases t h i s i n t e r v a l was l o n g e r than 30 s econds , and i t was p o s s i b l e t o recode a " r e c o v e r y " event 20-30 seconds a f t e r the f i r s t i n j e c t i o n . However, i n 13 s u b j e c t s the i n t e r v a l was l e s s than 30 seconds and r e c o d i n g was no t p o s s i b l e . As a r e s u l t , the c o r r e l a t i o n c o e f f i c i e n t s c a l c u l a t e d between 39 temperament s c o r e s and the f a c i a l a c t i o n summary s c o r e s f o r the " r e c o v e r y " event were computed u s i n g o n l y 55 i n f a n t s . S i n c e no s i g n i f i c a n t r e l a t i o n s h i p s between temperament and p a i n s c o r e s were d i s c o v e r e d , temperament was no t i n c l u d e d as a f a c t o r i n f u r t h e r a n a l y s e s . In o r d e r t o examine deve lopmenta l changes i n the degree o f p a i n e x p r e s s e d i n response t o the s h o t , p a i n summary s c o r e s were e n t e r e d i n t o an ANOVA. A c c o r d i n g t o o r i g i n a l p l a n s , d a t a was t o be e n t e r e d i n t o a 5x3 b e t w e e n - w i t h i n ANOVA, w i t h age as a be tween- subjec t s f a c t o r h a v i n g f i v e l e v e l s (2 , 4, 6, 12, and 18 months o f a g e ) , and event as a w i t h i n - s u b j e c t s f a c t o r h a v i n g t h r e e l e v e l s ( " n o p a i n , " " i n j e c t i o n , " and " r e c o v e r y " ) . In o r d e r t o examine deve lopmenta l changes i n the i n d i v i d u a l f a c i a l a c t i o n s c o m p r i s i n g the p a i n e x p r e s s i o n , the b a s i c d e s i g n was then t o be r e p e a t e d u s i n g a MANOVA f o r m a t , w i t h the i n d i v i d u a l f a c i a l a c t i o n s e n t e r e d as dependent v a r i a b l e s , r a t h e r t h a n a s i n g l e summary s c o r e . However, as ment ioned p r e v i o u s l y , 13 i n f a n t s had r e c e i v e d two i n j e c t i o n s b e f o r e the " r e c o v e r y " event and i t was n e c e s s a r y t o e x c l u d e these s u b j e c t s from the a n a l y s i s . As a r e s u l t , two MANOVAs were conducted f o r each c o d i n g sys tem, r a t h e r t h a n t h e one o r i g i n a l l y p l a n n e d . The " b a s e l i n e " and " i n j e c t i o n " events were a n a l y z e d i n a 5x2 b e t w e e n - w i t h i n MANOVA w i t h age as the be tween- subjec t f a c t o r and event as the w i t h i n - s u b j e c t f a c t o r . The f u l l s e t o f 75 s u b j e c t s was i n c l u d e d i n t h i s a n a l y s i s . The " r e c o v e r y " event was a n a l y z e d i n a s e p a r a t e oneway MANOVA w i t h age as a be tween- subjec t f a c t o r . I n f a n t s f o r whom i t was not p o s s i b l e t o code a " r e c o v e r y " p e r i o d a f t e r a 40 s i n g l e shot were d e l e t e d . In a d d i t i o n , f i v e o t h e r i n f a n t s were randomly d e l e t e d such t h a t c e l l s i z e s remained e q u a l . T h i s was n e c e s s a r y i n o r d e r t h a t the r e s u l t s be r o b u s t t o v i o l a t i o n s o f the assumpt ion o f homogeneity o f v a r i a n c e - c o v a r i a n c e m a t r i c e s . In c o n s i d e r i n g the s i g n i f i c a n c e o f c o r r e l a t i o n s and o f main e f f e c t s d e r i v e d from ANOVAs and MANOVAs, an a l e v e l o f .05 was u s e d . In f o l l o w - u p a n a l y s e s , the v a l u e o f a was lowered a c c o r d i n g t o the number o f groups o r v a r i a b l e s i n v o l v e d . I t s h o u l d be noted t h a t , i n the 12 month g r o u p , age i s confounded w i t h s t i m u l u s p r o p e r t i e s as t h e s e i n f a n t s were immunized w i t h a d i f f e r e n t v a c c i n e a t a d i f f e r e n t s i t e on the body . T h i s confound i s u n a v o i d a b l e and was c o n s i d e r e d when the r e s u l t s were i n t e r p r e t e d . 41 R E S U L T S 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 the sample Of the 75 i n f a n t s i n c l u d e d i n the f i n a l a n a l y s i s , 36 (48%) were male and 39 (52%) were f emale . Male i n f a n t s made up 8 (53%) o f the 2-month g r o u p , 6 (40%) o f the 4-month g r o u p , 6 (40%) o f t h e 6-month g r o u p , 10 (67%) o f t h e 12-month g r o u p , and 6 (40%) o f the 18-month g r o u p . T w e n t y - e i g h t (37.3%) o f the i n f a n t s were f i r s t b o r n , 32 (42.7%) were second b o r n , 10 (13.3%) t h i r d b o r n , 3 (4.0%) f o u r t h b o r n , and 1 (1.3%) s i x t h b o r n . One p a r e n t d i d not answer the q u e s t i o n . E i g h t i n f a n t s had been premature (10.7%). A l l o f the i n f a n t s ' p a r e n t s answered yes t o the q u e s t i o n " I s your baby g e n e r a l l y h e a l t h y ? " but one i n f a n t s u f f e r e d from T u r n e r ' s Syndrome, a chromosomal a b n o r m a l i t y u s u a l l y a s s o c i a t e d w i t h i n t e l l i g e n c e i n the low normal r a n g e . As a l l s c o r e s on temperament, f a c i a l v a r i a b l e s , and p a i n summary s c o r e s were w i t h i n two s t a n d a r d d e v i a t i o n s o f the mean, the i n f a n t was r e t a i n e d f o r the a n a l y s i s . A n a l y s e s r u n w i t h o u t t h i s s u b j e c t i n d i c a t e d t h a t r e s u l t s were not d i f f e r e n t from those when the i n f a n t was r e t a i n e d . S i x t y - t h r e e i n f a n t s (84%) were h e l d by t h e i r mothers , and twe lve (16%) by t h e i r f a t h e r s . F o r t y - f i v e (56%) o f p a r e n t s had g i v e n t h e i r c h i l d acetominophen b e f o r e the s h o t . T h i s was recommended by t h e c l i n i c nurse s as p r e v e n t i o n f o r t h e f e v e r t h a t can r e s u l t from i m m u n i z a t i o n . I t i s not expec ted t o have any e f f e c t on the p a i n o f a need le s t i c k . The t ime s i n c e f e e d i n g ranged from h a l f an hour t o 7 h o u r s , w i t h a mean o f 2.03 h o u r s . The t ime s i n c e waking ranged from 0 t o 8 h o u r s , w i t h a mean o f 2.58 h o u r s . 42 R e l a t i o n s h i p s between these c h a r a c t e r i s t i c s and the independent v a r i a b l e s o f age and temperament were examined. Where background c h a r a c t e r i s t i c s were c a t e g o r i c a l ( c l i n i c , n u r s e , gender , b i r t h o r d e r , p r e m a t u r i t y , p a r e n t , and use o f m e d i c a t i o n ) , c h i - s q u a r e t e s t s were used t o examine the r e l a t i o n s h i p w i t h age and ANOVAs were used t o examine the r e l a t i o n s h i p w i t h temperament. Where background v a r i a b l e s were c o n t i n u o u s ( t ime s i n c e f e e d i n g and t ime s i n c e w a k i n g ) , ANOVAs were used t o examine the r e l a t i o n s h i p w i t h age and c o r r e l a t i o n c o e f f i c i e n t s were used t o examine the r e l a t i o n s h i p w i t h temperament. These a n a l y s e s are summarized i n Appendix E . None o f the a n a l y s e s were s i g n i f i c a n t (p_>.05) • S o o t h i n g I n t e r v e n t i o n s The p e r c e n t o c c u r r e n c e o f v a r i o u s i n t e r v e n t i o n s a r e g i v e n i n T a b l e 1. 43 T a b l e 1 P e r c e n t o f P a r e n t s U s i n g Each S o o t h i n g I n t e r v e n t i o n I n t e r v e n t i o n % o f P a r e n t s U s i n g the I n t e r v e n t i o n S o o t h i n g V o c a l i z a t i o n 93 Arm R e s t r a i n t 67 T a c t i l e S t i m u l a t i o n 64 H o l d i n g L a t e r a l l y 45 H o l d i n g V e n t r a l l y 25 V e s t i b u l a r S t i m u l a t i o n 24 D i s t r a c t i o n 19 G i v i n g P a c i f i e r 9 B r e a s t F e e d i n g 4 B o t t l e F e e d i n g 0 n=75 C h i - s q u a r e t e s t s were used t o examine whether the f r e q u e n c y o f each i n t e r v e n t i o n v a r i e d w i t h age . S i g n i f i c a n t r e s u l t s were o b t a i n e d f o r H o l d i n g L a t e r a l l y (x 2 4=25.50, p_<.0001), and H o l d i n g V e n t r a l l y (x 2 4=13.67, p_<.01). The f r e q u e n c i e s o f these a c t i o n s a r e shown g r a p h i c a l l y i n F i g u r e 2. E x a m i n a t i o n o f the graphs sugges t s t h a t p a r e n t s are more l i k e l y t o c o m f o r t young i n f a n t s by h o l d i n g them l a t e r a l l y ( i . e . c r a d l i n g them i n t h e i r a r m s ) . H o l d i n g v e n t r a l l y shows a s l i g h t d e c l i n e i n t e r r u p t e d by a s h a r p i n c r e a s e i n f r e q u e n c y a t the age o f 12 months. T h i s may be due t o the f a c t t h a t i n t h i s age g r o u p , the l o c u s o f i n j e c t i o n was the upper arm r a t h e r t h a n the t h i g h . H o l d i n g v e n t r a l l y may a l l o w 44 M  ft  3  (! ) hf  p j h j rh O  ^ f l)  o"1  3  £  2  the nurse access t o the arm w h i l e m a i n t a i n i n g c l o s e c o n t a c t between p a r e n t and c h i l d . The r e l a t i o n s h i p between c h i l d temperament and s o o t h i n g i n t e r v e n t i o n s was a s s e s s e d t h r o u g h a s e r i e s o f t - t e s t s , w i t h the presence o r absence o f each s o o t h i n g i n t e r v e n t i o n as the g r o u p i n g v a r i a b l e . None o f the s o o t h i n g v a r i a b l e s reached s i g n i f i c a n c e a t the .05 l e v e l . The Independent V a r i a b l e s Age . S i n c e i n f a n t s r e c e i v e d immunizat ions a t f i v e d i f f e r e n t ages , age was t r e a t e d as a c a t e g o r i c a l v a r i a b l e , w i t h 15 s u b j e c t s per g r o u p . The r e s u l t i n g groups a r e summarized i n T a b l e 2. T a b l e 2 D e s c r i p t i o n o f Age G r o u p s . Age Group Mean Age S t a n d a r d Minimum Maximum Age i n Days D e v i a t i o n Age i n Days i n Days 2 months 68 7.38 59 84 4 months 132 13.60 104 154 6 months 201 16.38 176 228 12 months 380 12.41 362 407 18 months 563 17.86 536 594 n=15 Temperament. Scores on the f u s s y / d i f f i c u l t f a c t o r were c a l c u l a t e d f o r each v e r s i o n o f t h e q u e s t i o n n a i r e . The means and s t a n d a r d d e v i a t i o n s a r e g i v e n i n T a b l e 3, a l o n g w i t h the means and s t a n d a r d d e v i a t i o n s from B a t e s ' (1992) s t a n d a r d i z a t i o n sample . 46 T a b l e 3 D i s t r i b u t i o n o f Temperament Scores C u r r e n t Sample: Q u e s t i o n n a i r e Mean S t a n d a r d Form d e v i a t i o n 4.54 5.71 S t a n d a r d i z a t i o n Sample: Q u e s t i o n n a i r e Mean S t a n d a r d Form d e v i a t i o n " 6 m o n t h s " 17.77 5.88 "12 m o n t h s " 28.64 7.43 P a r e n t s f a i l e d t o answer a q u e s t i o n c o n t r i b u t i n g t o temperament s c o r e i n two i n s t a n c e s , which r e p r e s e n t s 0.37% o f the q u e s t i o n n a i r e d a t a . The s c o r e s were r e p l a c e d w i t h mean v a l u e s f o r the i t em a c c o r d i n g t o B a t e s ' (1992) s t a n d a r d i z a t i o n d a t a . In o r d e r t o have the s c o r e s from the two forms comparab le , the observed s c o r e s were s t a n d a r d i z e d u s i n g the means and s t a n d a r d d e v i a t i o n s from B a t e s ' sample . The s t a n d a r d i z e d s c o r e s were used i n subsequent a n a l y s e s . " 6 m o n t h s " 17.29 "12 m o n t h s " 29.12 47 The r e l a t i o n s h i p between aae and temperament. The r e l a t i o n s h i p between age and temperament was examined w i t h a oneway ANOVA. There was no s i g n i f i c a n t r e l a t i o n s h i p between the two ( F ( 4 , 7 0 ) = 0 . 3 7 , p_>.5). The Dependent V a r i a b l e s C o l l a p s i n g o f Baby FACS a c t i o n s . P r e v i o u s s t u d i e s u s i n g FACS t o i n v e s t i g a t e the f a c i a l e x p r e s s i o n o f p a i n i n a d u l t s u b j e c t s have noted t h e d i f f i c u l t y i n d i s t i n g u i s h i n g between c e r t a i n a c t i o n u n i t s . F o r example, Ekman, F r i e s e n and Simons (1985) d i s r e g a r d e d the f i n e r d i s t i n c t i o n " between AU6 (cheek r a i s e ) and AU7 ( l i d s t i g h t ) i n t h e i r a n a l y s i s o f the s t a r t l e r e s p o n s e . O t h e r s have found i t d i f f i c u l t t o d i s t i n g u i s h between AU9 (nose w r i n k l e ) and AU10 (upper l i p r a i s e ) and sugges ted t h a t these a c t i o n s a r e p a r t o f the same b a s i c p r o c e s s ( P r k a c h i n & M e r c e r , 1989) . C o n s e q u e n t l y , P r k a c h i n (1992) has recommended t h a t a n a l y s e s be conducted on the compos i te v a r i a b l e s o f " o r b i t t i g h t e n i n g " (AU6/AU7) and " l e v a t o r c o n t r a c t i o n " (AU9/AU10) . O s t e r and R o s e n s t e i n (1993) note t h a t "the d i s t i n c t i o n between AUs 6 and 7 i s one o f the most d i f f i c u l t t o make i n i n f a n t s . . . . . i n many cases b o t h a r e p r o b a b l y a c t i n g " (pp. 18 -19 ) . S i m i l a r l y t h e y note t h a t " c o n f u s i o n between AU 9 and AU 10 i s even more f r e q u e n t i n i n f a n t s than i n a d u l t s . . . . I n many c a s e s , i t i s l i k e l y t h a t b o t h a r e a c t i n g . . . . i f i t i s no t c l e a r which are a c t i n g , i t may be b e s t t o acknowledge the a m b i g u i t y by c o d i n g "AU 9 a n d / o r 10" (p . 27 ) . In l i g h t o f these comments, P r k a c h i n # s recommendations seem s u i t a b l e f o r i n f a n t s as w e l l as a d u l t s , and the v a r i a b l e s were c o l l a p s e d a c c o r d i n g t o h i s i n s t r u c t i o n s . 48 Frequency o f o c c u r r e n c e o f f a c i a l v a r i a b l e s . Frequency and p e r c e n t o c c u r r e n c e were c a l c u l a t e d f o r the 10 NFCS a c t i o n u n i t s and the 45 Baby FACS a c t i o n u n i t s examined i n t h i s s t u d y . P e r c e n t o c c u r r e n c e s a r e g i v e n i n Appendix F . The f o l l o w i n g f i v e NFCS a c t i o n u n i t s were observed t o o c c u r i n more t h a n 10% o f coded segments: Brow b u l g e , Eye squeeze , Deepened n a s o l a b i a l f u r r o w , Open l i p s , and T a u t tongue . These a c t i o n s were r e t a i n e d f o r f u r t h e r a n a l y s e s . The o t h e r f i v e a c t i o n s ( V e r t i c a l mouth s t r e t c h , H o r i z o n t a l mouth s t r e t c h , L i p p u r s e , C h i n q u i v e r , and Tongue p r o t r u s i o n ) were o b s e r v e d t o o c c u r i n l e s s t h a n 10% o f coded 2-second segments, and thus were d i s c a r d e d from f u r t h e r a n a l y s e s . The f o l l o w i n g 10 Baby FACS a c t i o n u n i t s were r e c o r d e d i n more than 10% o f coded segments: AU 1-Inner Brow R a i s e , AU 3-Brow K n i t , AU 4-Brow Lower, AU6/AU7- O r b i t T i g h t e n i n g , A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n , A U 1 7 - C h i n R a i s e , AU26-Jaw D r o p , AU43-Eyes C l o s e d , A U 4 4 - S q u i n t , and AU75d-Tense , Concave Tongue. These a c t i o n s were r e t a i n e d f o r f u r t h e r a n a l y s e s , w h i l e the o t h e r Baby FACS a c t i o n s were d i s c a r d e d . M i s s i n g d a t a . Because p a r e n t s and nurses were t o l d t o " p r o c e e d as u s u a l , " t h e r e were i n e v i t a b l y segments i n which the i n f a n t ' s f a c e was o b s c u r e d . A c c o r d i n g t o NFCS c o d e r s , the e n t i r e f a c e was no t v i s i b l e i n 7.29% o f segments. In a d d i t i o n , i n d i v i d u a l a c t i o n s were not v i s i b l e i n the f o l l o w i n g percentage o f segments: brow b u l g e , 1.07%; eye squeeze , 0.44%; n a s o l a b i a l f u r r o w , 1.42%, and open l i p s , 1.69%. A c c o r d i n g t o the p r i m a r y FACS c o d e r , the e n t i r e f a c e was o b s c u r e d i n 7.29% o f segments; the upper f a c e was 49 not v i s i b l e i n 0.98% o f segments and the lower f a c e was no t v i s i b l e i n 2.13% o f segments. I f o n l y one o r two o f the f i v e segments from an " e v e n t " were m i s s i n g , they were r e p l a c e d w i t h the mean s c o r e t a k e n from t h e v i s i b l e segments f o r t h a t i n f a n t . I f more t h a n two o f the segments were m i s s i n g , t h a t event was o m i t t e d from c o r r e l a t i o n a l a n a l y s e s conducted t o examine the r o l e o f temperament. However, i n o r d e r t o r e t a i n e q u a l c e l l s i z e s i n the MANOVA conducted t o examine the r o l e o f age , the i n f a n t ' s s c o r e s f o r the e n t i r e event were r e p l a c e d w i t h the mean v a l u e s f o r t h a t c e l l , i . e . the mean v a l u e s observed i n i n f a n t s i n the same age group d u r i n g t h e same e v e n t . T h i s was n e c e s s a r y f o r n i n e events (4% o f the t o t a l ) . There i s precedence f o r such an approach i n p r e v i o u s s t u d i e s ( e . g . , C r a i g e t a l . , 1993) . C o n s t r u c t i o n o f the P a i n Summary S c o r e s . In o r d e r t o answer t h e r e s e a r c h q u e s t i o n s , a s i n g l e index o f the amount o f p a i n e x p r e s s e d by the i n f a n t was d e s i r e d . W i t h t h i s i n mind , the f a c i a l a c t i o n s o b s e r v e d w i t h i n each c o d i n g system d u r i n g the " i n j e c t i o n " event were s u b j e c t e d t o a p r i n c i p a l components a n a l y s i s . The r e s u l t s o f the p r i n c i p a l components a n a l y s i s conducted on the NFCS v a r i a b l e s w i l l be d i s c u s s e d f i r s t . The K a i s e r - M e y e r - O l k i n Measure o f Sampl ing Adequacy was . 7 1 , above the .6 r e q u i r e d t o conduct the a n a l y s i s ( T a b a c h n i c k & F i d e l l , 1989) . The B a r t l e t t T e s t o f S p h e r i c i t y was 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 were s u f f i c i e n t c o r r e l a t i o n s among the v a r i a b l e s t o w a r r a n t f a c t o r a n a l y s i s . A s i n g l e f a c t o r w i t h an e i g e n v a l u e o f 2.88 was i d e n t i f i e d , and i n s p e c t i o n o f the s c r e e p l o t c o n f i r m e d the 50 s u i t a b i l i t y o f the s i n g l e - f a c t o r s o l u t i o n ( C a t t e l l , 1966) . As w e l l , t h i s f a c t o r s t r u c t u r e i s comparable t o t h a t found i n p r e v i o u s r e s e a r c h ( C r a i g e t a l . , 1994) . T h i s f a c t o r accounted f o r 57.7% o f the v a r i a n c e i n NFCS a c t i o n s , a f i g u r e somewhat lower t h a n has been found i n p r e v i o u s r e s e a r c h ( C r a i g e t a l . , 1994) . A l l f i v e o f the NFCS a c t i o n s l o a d e d p o s i t i v e l y on the f a c t o r , which makes c o n c e p t u a l s ense . F a c t o r l o a d i n g s a r e p r e s e n t e d i n T a b l e 4. T a b l e 4 F a c t o r L o a d i n g s f o r the NFCS F a c i a l A c t i o n s F a c i a l A c t i o n F a c t o r L o a d i n g Brow b u l g e .82 Eye squeeze .80 Deepened n a s o l a b i a l furrow .91 Open l i p s .61 Taut tongue .62 The p r i n c i p a l components a n a l y s i s conducted on the Baby FACS a c t i o n u n i t s produced s i m i l a r r e s u l t s . The K a i s e r - M e y e r - O l k i n Measure o f Sampl ing Adequacy was .70 and the B a r t l e t t T e s t o f S p h e r i c i t y was s i g n i f i c a n t . The a n a l y s i s i d e n t i f i e d t h r e e f a c t o r s w i t h e i g e n v a l u e s g r e a t e r t h a n one . However, i n s p e c t i o n o f the s c r e e p l o t ( C a t t e l l , 1966) sugges ted t h a t the s i n g l e f a c t o r s o l u t i o n was more a p p r o p r i a t e . F u r t h e r m o r e , the second and and t h i r d f a c t o r s were no t e a s i l y i n t e r p r e t a b l e and somewhat u n s t a b l e as they were based on o n l y one o r two a c t i o n 51 u n i t s . As a r e s u l t , the s o l u t i o n was r e s t r i c t e d t o one f a c t o r . T h i s f a c t o r had an e i g e n v a l u e o f 4.29 and accounted f o r 42.9% o f the v a r i a n c e i n Baby FACS a c t i o n s . A l l o f the Baby FACS a c t i o n s l o a d e d p o s i t i v e l y on the f a c t o r , w i t h the e x c e p t i o n o f AU1, i n n e r brow r a i s e . F a c t o r l o a d i n g s a r e p r e s e n t e d i n T a b l e 5. 52 T a b l e 5 F a c t o r L o a d i n g s f o r the Baby FACS A c t i o n s F a c i a l A c t i o n F a c t o r L o a d i n g A U l - I n n e r brow r a i s e - . 3 2 AU3-Brow k n i t .74 AU4-Brow lower .76 A U 6 / 7 - O r b i t t i g h t e n i n g .89 A U 9 / 1 0 - L e v a t o r c o n t r a c t i o n .86 A U 1 7 - C h i n r a i s e .27 AU26-Jaw d r o p .75 AU43-Eyes c l o s e d .70 AU44-Squ in t .13 . AU75d-Tense , concave tongue .62 These f a c t o r l o a d i n g s were h i g h l y c o n s i s t e n t w i t h e x p e c t a t i o n s . W i t h i n each c o d i n g sys tem, the i n d i v i d u a l a c t i o n u n i t s p r e v i o u s l y o b s e r v e d t o be a s s o c i a t e d w i t h p a i n f u l s t i m u l i l oaded onto the f a c t o r . The f a c t o r l o a d i n g s a r e seen as r e p r e s e n t i n g the c o n t r i b u t i o n s o f i n d i v i d u a l a c t i o n s t o the g l o b a l p a i n e x p r e s s i o n . By examining the a c t i o n s t h a t l o a d h e a v i l y on each f a c t o r , i t i s p o s s i b l e t o d e r i v e a q u a l i t a t i v e d e s c r i p t i o n o f the " p a i n f a c e " a c c o r d i n g t o each c o d i n g sys tem. A c c o r d i n g t o NFCS, the f a c i a l e x p r e s s i o n o f p a i n i n i n f a n t s i s c r e a t e d by l o w e r i n g the eyebrows and drawing them t o g e t h e r , s q u e e z i n g the e y e l i d s t o g e t h e r , deepening the n a s o l a b i a l furrow and p u l l i n g i t upwards, open ing the l i p s , and d i s p l a y i n g a r a i s e d tongue w i t h s h a r p , t e n s e d edges . A c c o r d i n g t o Baby FACS, the 53 f a c i a l e x p r e s s i o n o f p a i n i s c r e a t e d by k n i t t i n g and l o w e r i n g the brows, t i g h t e n i n g the musc les s u r r o u n d i n g the eye , c l o s i n g the e y e s , w r i n k l i n g the nose and r a i s i n g the upper l i p , d r o p p i n g the jaw, and d i s p l a y i n g a t e n s e , concave tongue . A l t h o u g h t h e r e are some d i f f e r e n c e s , these r e s u l t s a r e g e n e r a l l y c o n s i s t e n t w i t h the r e s u l t s o f p r e v i o u s s t u d i e s ( C r a i g e t a l . , 1993; C r a i g e t a l . , 1994; Grunau e t a l . , 1990) . The f a c t o r l o a d i n g s were used t o d e r i v e p a i n summary s c o r e s : f o r each c o d i n g sys tem, the f a c t o r l o a d i n g s were used as we ights i n a l i n e a r c o m b i n a t i o n o f f a c i a l a c t i o n s . The same we ights were used t o c a l c u l a t e p a i n summary s c o r e s f o r each i n f a n t f o r each e v e n t . These p a i n summary s c o r e s were t h e n used as dependent measures i n f u r t h e r a n a l y s e s . Two measures o f p a i n . I f the summary s c o r e s d e r i v e d from t h e two c o d i n g systems were each measur ing p a i n , s i g n i f i c a n t c o r r e l a t i o n s between the two measures would be e x p e c t e d . Pearson product-moment c o r r e l a t i o n c o e f f i c i e n t s were c a l c u l a t e d between the NFCS p a i n summary and the Baby FACS p a i n summary f o r each o f the events expec ted t o be p a i n f u l i . e . " i n j e c t i o n " and " r e c o v e r y . " The r e s u l t s a r e g i v e n i n T a b l e 6. 54 T a b l e 6 C o r r e l a t i o n s between NFCS and Baby FACS p a i n summary s c o r e s Event n r E " i n j e c t i o n " 75 .79 <.001 X A r e c o v e r y " 55 .79 <.001 Both o f the above c o r r e l a t i o n s were s i g n i f i c a n t a t the .001 l e v e l , c o n s i s t e n t w i t h the p r o p o s i t i o n t h a t b o t h summary s c o r e s a r e measures o f p a i n . In o r d e r t o f u r t h e r examine concordance between the two measures , the c o r r e l a t i o n s between i n d i v i d u a l a c t i o n u n i t s were a l s o computed. Two c o r r e l a t i o n m a t r i c e s were c o n s t r u c t e d , one f o r a c t i o n s o f t h e upper f a c e ( T a b l e 7 ) , and one f o r a c t i o n s o f the lower f a c e ( T a b l e 8 ) . 55 T a b l e 7 C o r r e l a t i o n s between NFCS A c t i o n s and Baby FACS A c t i o n s : The Upper Face NFCS A c t i o n s Baby FACS A c t i o n s Brow Bulge Eye Squeeze Deepened N a s o l a b i a l Furrow A U l - I n n e r r = - . 1 6 r = - . 3 0 r = - . 1 3 Brow R a i s e p_<.10 p_<.001 p_<.015 AU3-Brow K n i t r= .49 r=.52 r=.45 p_<.ooi E<.001 p.<.001 AU4-Brow r= .50 r=.63 r=.43 Lower p_<.001 p<.ooi E<.001 A U 6 / A U 7 - 0 r b i t r= .55 r=.76 r = . 63 T i g h t e n i n g p_<.001 p_<.001 p_<.001 AU9/AU10- r=.58 r=.68 r=.65 L e v a t o r p_<.001 p_<.001 p.<.001 C o n t r a c t i o n AU43-Eyes r= .39 r= .66 r=40 C l o s e d p_<.001 p.<.001 E<.001 A U 4 4 - S q u i n t r=.22 r = . 25 r=.23 E<-015 p_<.005 E<.01 56 T a b l e 8 C o r r e l a t i o n s between NFCS A c t i o n s and Baby FACS A c t i o n s : The Lower Face NFCS A c t i o n s Baby FACS A c t i o n s Open L i p s T a u t Tongue AU17-Chin R a i s e r = . 10 r = . 13 p_<.25 p_<.15 AU26-Jaw Drop r = . 49 r = . 47 p_<.001 p_<.001 AU75d-Tense , r = . 22 r=.68 Concave Tongue p_<.05 E<-001 On t h e b a s i s o f c o n t e n t , the s t r o n g e s t c o r r e l a t i o n s would be p r e d i c t e d between a) NFCS Brow Bulge and Baby FACS AUs 3-Brow K n i t and 4-Brow Lower, b) NFCS Eye Squeeze and Baby FACS AU6/AU7- O r b i t T i g h t e n i n g , c ) NFCS Deepened N a s o l a b i a l Furrow and Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n , d) NFCS Open L i p s and Baby FACS AU26-Jaw D r o p , and e) NFCS T a u t Tongue and Baby FACS AU75d- T e n s e , Concave Tongue. A l l o f t h e s e c o r r e l a t i o n s were found t o be s i g n i f i c a n t . However, i n t e r p r e t a t i o n o f the m a t r i x i s complex . T h i s i s s u e w i l l be examined f u r t h e r i n the D i s c u s s i o n s e c t i o n . 57 The R e l a t i o n s h i p between P a i n and Temperament The f i r s t r e s e a r c h q u e s t i o n t o be addres sed f o c u s s e d on the r e l a t i o n s h i p between f a c i a l e x p r e s s i o n i n response t o a p a i n f u l s t i m u l u s and the n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament. I t was h y p o t h e s i z e d t h a t i n f a n t s who were r a t e d by t h e i r p a r e n t s as more f u s s y o r d i f f i c u l t would show the g r e a t e s t f a c i a l response t o the i n j e c t i o n . Pearson product-moment c o r r e l a t i o n c o e f f i c i e n t s were c a l c u l a t e d t o a s se s s the r e l a t i o n s h i p between p a i n summary s c o r e s and s c o r e s on the f u s s y - d i f f i c u l t f a c t o r f o r each e v e n t . The r e s u l t s a r e summarized i n T a b l e 9. 58 T a b l e 9 C o r r e l a t i o n s between P a i n Summary Scores and Temperament Scores A n a l y s e s based on NFCS a c t i o n s : Event n r E " b a s e l i n e " 70 - . 0 4 >.75 " i n j e c t i o n " 75 - . 1 4 >.20 " r e c o v e r y " 55 .00 >.90 A n a l y s e s based on Baby FACS a c t i o n s : Event n r E " b a s e l i n e " 70 - . 0 1 >.90 " i n j e c t i o n " 75 - . 0 9 >.40 " r e c o v e r y " 55 - . 1 3 >.30 S t a t i s t i c a l s i g n i f i c a n c e was no t observed i n any o f the r e l a t i o n s h i p s r e p o r t e d . I n f a n t s p e r c e i v e d by t h e i r p a r e n t s as f u s s i e r and more d i f f i c u l t d i d not r e a c t t o the i n j e c t i o n w i t h g r e a t e r i n t e n s i t y . S i n c e no r e l a t i o n s h i p was observed between temperament and p a i n s c o r e s , and p r e l i m i n a r y a n a l y s e s had not shown a r e l a t i o n s h i p between temperament and age g r o u p , temperament was not i n c l u d e d as a f a c t o r i n the MANOVAs conducted t o examine age d i f f e r e n c e s i n the p a i n r e s p o n s e . Deve lopmenta l Changes i n t h e F a c i a l E x p r e s s i o n o f P a i n The second r e s e a r c h q u e s t i o n t o be addres sed i n v o l v e d the i d e n t i f i c a t i o n o f deve lopmenta l change i n the f a c i a l e x p r e s s i o n o f p a i n , b o t h i n the o v e r a l l degree o f p a i n expres sed and the i n d i v i d u a l f a c i a l v a r i a b l e s . 59 Developmental Changes i n the I n t e n s i t y o f the P a i n R e a c t i o n To addres s t h i s q u e s t i o n , a s e r i e s o f ANOVAs were conducted u s i n g p a i n summary s c o r e s as the outcome measure. A n a l y s e s conducted on the " b a s e l i n e " and " i n i e c t i o n " e v e n t s . F o r each c o d i n g sys tem, a 5x2 b e t w e e n - w i t h i n ANOVA was c o n d u c t e d , w i t h age as t h e b e t w e e n - s u b j e c t s f a c t o r and event as the w i t h i n - s u b j e c t s f a c t o r . C e l l means and s t a n d a r d d e v i a t i o n s from the NFCS d a t a are p r e s e n t e d i n T a b l e 10. T a b l e 10 C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS P a i n Summary Scores by Age by Event Age Group: Event 2 Months 4 Months 6 Months 12 Months 18 Months " b a s e l i n e " M 8.74 3.39 4.01 3.35 5.69 SD 6.91 2.20 2.75 4.07 5.36 " i n j e c t i o n " M 14.74 12.06 14.58 14.37 13.43 SD 4.45 5.17 5.16 3.68 4.86 n=15 The i n t e r a c t i o n between age group and event was n o n - s i g n i f i c a n t (p_>.10). Both the main e f f e c t o f age group ( F ( 4 , 7 0 ) = 2 . 6 1 , E<.05) and the main e f f e c t o f event ( F ( l , 7 0 ) = 1 5 7 . 1 5 , p_<.001) were s i g n i f i c a n t . Wi th r e g a r d s t o the main e f f e c t o f e v e n t , e x a m i n a t i o n o f m a r g i n a l means r e v e a l e d t h a t t h e p a i n summary s c o r e s were , as e x p e c t e d , s i g n i f i c a n t l y h i g h e r d u r i n g the " i n j e c t i o n " event than d u r i n g the " b a s e l i n e " e v e n t . The o v e r a l l p a i n summary s c o r e f o r the " b a s e l i n e " event 60 was 5 .04; f o r the " i n j e c t i o n " e v e n t , i t was 13 .84 . F o l l o w - u p a n a l y s e s (Tukey) o f the age e f f e c t , w i t h a dropped t o the 0.01 l e v e l , r e v e a l e d t h a t 2 month o l d i n f a n t s had p a i n summary s c o r e s s i g n i f i c a n t l y h i g h e r than those o f 4 month o l d i n f a n t s . No o t h e r d i f f e r e n c e s were s i g n i f i c a n t . These r e s u l t s are d e p i c t e d g r a p h i c a l l y i n F i g u r e 3. 61  C e l l means and s t a n d a r d d e v i a t i o n s o b t a i n e d from the baby FACS d a t a are p r e s e n t e d i n T a b l e 11. T a b l e 11 C e l l Means and S t a n d a r d D e v i a t i o n s : Baby FACS P a i n Summary Scores by Age by Event Age Group: Event 2 Months 4 Months 6 Months 12 Months 18 Months " b a s e l i n e " M 30.94 SD 30.27 8.00 6.92 6.67 6.71 5.73 8.92 17.67 23.10 " i n j e c t i o n " M 74.28 SD 21.61 54.64 27.54 53.89 29.25 64.71 25.96 54.53 25.46 n=15 A g a i n , bo th the main e f f e c t o f age group ( F ( 4 , 7 0 ) = 4 . 3 7 , E<.005) and the main e f f e c t o f event (F( 1,70) =182.08, p_<.001) were s i g n i f i c a n t . E x a m i n a t i o n o f the m a r g i n a l means r e v e a l e d t h a t p a i n summary s c o r e s were s i g n i f i c a n t l y h i g h e r d u r i n g the " i n j e c t i o n " event t h a n d u r i n g the " b a s e l i n e " e v e n t . Tukey t e s t s per formed as f o l l o w - u p a n a l y s e s o f the main e f f e c t o f age w i t h a dropped t o the 0.01 l e v e l , r e v e a l e d t h a t 2-month o l d i n f a n t s had s i g n i f i c a n t l y h i g h e r p a i n summary s c o r e s than 4- month o l d i n f a n t s o r 6-month o l d i n f a n t s . No o t h e r d i f f e r e n c e s were s i g n i f i c a n t . F i g u r e 4 i s a graph o f these r e s u l t s . 63  A n a l y s e s conducted on the " r e c o v e r y " e v e n t . F o r each c o d i n g sys tem, a oneway ANOVA was conducted , w i t h age group as a b e t w e e n - s u b j e c t s f a c t o r . C e l l means and s t a n d a r d d e v i 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 12. T a b l e 12 C e l l Means and S t a n d a r d D e v i a t i o n s NFCS A c t i o n s : NFCS P a i n Summary Scores by Age Age Group: n=10 2 Months 4 Months 6 Months 12 Months 18 Months M 11.16 6.00 11.91 10.74 12.63 SD 6.14 4.70 4.03 3.15 2.06 The main e f f e c t o f age group ( F ( 4 , 50)=3.27, p_<.05) was s i g n i f i c a n t . F o l l o w - u p a n a l y s e s took the form o f Tukey t e s t s . When a was dropped t o 0 . 0 1 , none o f the d i f f e r e n c e s r e a c h e d s i g n i f i c a n c e . However, a t the 0.05 l e v e l , i t was apparent t h a t 4-month o l d i n f a n t s had p a i n summary s c o r e s t h a t were lower than e i t h e r 18-month o l d i n f a n t s o r 6-month o l d i n f a n t s . No o t h e r p a i r o f means d i f f e r e d s i g n i f i c a n t l y . The d i f f e r e n c e s , shown g r a p h i c a l l y i n F i g u r e 5, s h o u l d p r o p e r l y be r e g a r d e d as t r e n d s . 65  C e l l means and s t a n d a r d d e v i a t i o n s from the Baby FACS d a t a a r e p r e s e n t e d i n T a b l e 13. T a b l e 13 C e l l Means and S t a n d a r d D e v i a t i o n s : Baby FACS P a i n Summary Scores by Age 2 Months 4 Months 6 Months 12 Months 18 Months M 45.44 20.95 33.37 39.13 47.82 SD 28.67 18.26 21.12 16.22 24.30 n=10 The main e f f e c t o f age group on Baby FACS p a i n summary s c o r e d u r i n g the " r e c o v e r y " event d i d no t r e a c h s i g n i f i c a n c e (p_>.05). The d a t a are shown g r a p h i c a l l y i n F i g u r e 6. E x a m i n a t i o n o f the f i g u r e i n d i c a t e s c o n s i d e r a b l e v a r i a b i l i t y among the g r o u p s . Developmental Changes i n t h e Nature o f the P a i n E x p r e s s i o n To address t h i s q u e s t i o n , a s e r i e s o f MANOVAs were p e r f o r m e d , w i t h the i n d i v i d u a l f a c i a l v a r i a b l e s as dependent measures . Only t h o s e v a r i a b l e s o c c u r r i n g i n more t h a n 10% o f segments were i n c l u d e d i n the a n a l y s i s . A n a l y s e s conducted on the " b a s e l i n e " and " i n j e c t i o n " e v e n t s . The r e l a t i o n s h i p between age and the f a c i a l e x p r e s s i o n o f p a i n d u r i n g the " b a s e l i n e " and " i n j e c t i o n " events was examined thr ough a 5x2 b e t w e e n - w i t h i n MANOVA w i t h age as t h e between s u b j e c t s f a c t o r and event as the w i t h i n - s u b j e c t s f a c t o r . C e l l means and s t a n d a r d d e v i a t i o n s o b t a i n e d from t h i s a n a l y s i s f o r the NFCS d a t a a r e g i v e n i n T a b l e 14. 67  T a b l e 14 C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS A c t i o n s by Age " B a s e l i n e " event : Age g r o u p : n=15 A c t i o n U n i t 2 Months 4 Months 6 Months 12 Months 18 Months Brow bu lge M 2.80 SD 2.15 0.81 1.13 1.13 1.64 1.27 1.68 1.86 2.20 Eye squeeze M 1.67 SD 2.23 0.00 0.00 0.00 0.00 0.29 1.03 0.29 1.03 Deepened n a s o - l a b i a l furrow M 2.00 SD 2.33 0.56 1.17 0.87 1.36 0.68 1.30 1.50 2.13 Open l i p s M 4.20 SD 1.74 3.65 1.97 3.63 2.11 2.41 2.43 3.32 2.20 T a u t tongue M 1.20 SD 2.08 0.00 0.00 0.13 0.52 0.00 0.00 0.91 1.76 j e c t i o n " e v e n t : Age g r o u p : A c t i o n U n i t 2 Months 4 Months 6 Months 12 Months 18 Months Brow b u l g e M 4.43 SD 1.40 3.77 1.49 4.40 1.40 4.47 0.99 4.21 1.74 Eye squeeze M 3.93 SD 1.83 2.93 1.67 3.72 2.02 3.47 1.73 2.93 2.19 Deepened n a s o - l a b i a l furrow M 4.20 SD 1.74 3.39 1.61 4.20 1.61 4.42 0.91 4.33 1.76 Open l i p s M 4.67 SD 1.29 4.00 1.77 4.73 0.70 4.63 0.81 4.93 0.26 Taut tongue M 2.13 SD 2.36 1.82 2.06 2.13 2.23 1.80 2.04 1.13 2.07 n=15 N e i t h e r the i n t e r a c t i o n between age and event nor the main e f f e c t o f age was s i g n i f i c a n t (p_>.50 and p_>.10 r e s p e c t i v e l y ) . 69 However, as e x p e c t e d , the main e f f e c t o f event was s i g n i f i c a n t ( F ( 5 , 6 6 ) =105.44, p_<.001). F o l l o w - u p a n a l y s e s i n the form o f 5 p a i r e d t - t e s t s i n d i c a t e d t h a t means f o r a l l o f the NFCS a c t i o n s were g r e a t e r d u r i n g the " i n j e c t i o n " event than d u r i n g the " b a s e l i n e ' ' e v e n t . C e l l means and s t a n d a r d d e v i a t i o n s o b t a i n e d f o r the Baby FACS a c t i o n s are g i v e n i n T a b l e 15. 70 T a b l e 15 C e l l Means and S t a n d a r d D e v i a t i o n s : Baby FACS A c t i o n s by Age by Event x x b a s e l i n e " event : Age group: A c t i o n 2 4 6 12 18 U n i t Months Months Months Months Months 1 Inner Brow M 1.00 0.33 1.5.3 1.07 1.48 R a i s e SD 1.89 0.69 3.38 2.63 3.00 3 Brow M 5.60 0.17 0.82 0.70 3.20 K n i t SD 7.22 0.51 1.98 1.68 5.63 4 Brow Lower M 5.13 0.17 0.07 0.63 1.14 SD 6.74 0.51 0.26 1.69 4.12 6/7 O r b i t M 6.73 1.94 0.50 0.52 3.68 T i g h t e n - SD 8.03 4.76 1.94 1.55 6.45 i n g 9/10 L e v a t o r M 5.60 0.10 0.80 0.59 4.57 C o n t r a c t - SD 7.41 7.41 2.08 1.81 6.44 i o n 17 C h i n R a i s e M 2.73 0.00 0.13 0.26 2.21 SD 5.18 0.00 0.52 0.86 5.68 26 Jaw M 11.78 7.69 6.93 5.06 8.09 Drop SD 6.21 4.69 4.46 5.46 6.62 43 Eyes M 2.60 0.31 0.08 0.36 1.2.1 C l o s e d SD 4.60 0.69 0.32 1.29 4.38 44 S q u i n t M 3.93 0.42 0.00 0.00 1.50 SD 7.11 1.28 0.00 0.00 5.41 75d Tense , Concave M 0.80 0.00 0.13 0.00 0.00 Tongue SD 1.52 0.00 0.52 0.00 0.00 n=15 71 * I n j e c t i o n " event : Age g r o u p : A c t i o n 2 4 6 12 18 U n i t Months Months Months Months Months 1 Inner Brow M 0.33 1.60 1.13 0.53 0.67 R a i s e SD 1.05 3.60 2.70 0.99 1.29 3 Brow M 14.32 12.35 6.89 12.60 9.93 K n i t SD 6.88 6.31 5.43 7.77 7.60 4 Brow M 12.67 9.78 7.69 12.33 7.53 Lower SD 8.03 5.54 6.59 6.60 7.32 6/7 O r b i t T i g h t e n - M 15.78 11.85 12.20 13.60 12.13 i n g SD 5.22 7.38 7.32 6.02 7.31 9/10 L e v a t o r C o n t r a c t - M 17.30 12.38 12.20 15.56 13.78 i o n SD 5.50 5.01 8.38 6.61 7.32 17 C h i n M 4.57 2.67 2.33 3.33 1.78 R a i s e SD 5.38 5.64 6.14 5.04 4.30 26 Jaw M 17.79 11.98 16.47 16.05 15.77 Drop SD 4.92 6.34 4.93 4.72 5.45 43 Eyes M 12.52 9.12 11.05 8.93 8.33 C l o s e d SD 6.70 7.90 7.88 7.19 7.24 44 S q u i n t M 3.73 2.67 1.93 4.20 2.20 SD 8.77 4.19 6.24 5.16 6.47 75d T e n s e , Concave M 2.26 1.52 1.60 1.53 0.93 Tongue SD 2.09 1.82 2.10 1.96 1.34 In t h i s a n a l y s i s , b o t h t h e main e f f e c t o f age ( F ( 4 0 , 233)=1.80, p_<.005) and the main e f f e c t o f event ( F ( 1 0 , 61)=38.13, p_<.001) r e a c h e d s i g n i f i c a n c e . The i n t e r a c t i o n between age group and event was not s i g n i f i c a n t (p_>.10). F o l l o w - u p a n a l y s e s on the main e f f e c t o f age were conducted i n the form o f i n d i v i d u a l oneway ANOVAs f o r each o f the 10 f a c i a l v a r i a b l e s , w i t h a dropped t o t h e 0.005 l e v e l . The r e s u l t s are p r e s e n t e d i n T a b l e 16. T a b l e 16 U n i v a r i a t e R e s u l t s : Baby FACS A c t i o n s by Age A c t i o n U n i t F ( 4 , 7 0 ) E AU1-Inner Brow R a i s e 0.07 >.05 AU3-Brow K n i t 2.17 >.05 AU4-Brow Lower 3.11 <.025 A U 6 / A U 7 - O r b i t T i g h t e n i n g 2.46 >.05 A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n 6.86 <.001 AU17-Chin R a i s e 0.55 >.05 AU26-Jaw Drop 0.74 >.05 AU43-Eyes C l o s e d 0.54 >.05 AU44-Squ in t f 0.29 >.05 AU75d-Tense , Concave Tongue 0.09 >.05 The a n a l y s e s i n d i c a t e d a s i g n i f i c a n t e f f e c t o f age f o r A U 9 - L e v a t o r C o n t r a c t i o n . AU4-Brow Lower, approached s i g n i f i c a n c e . The o t h e r 8 ANOVAs were n o n - s i g n i f i c a n t . F o l l o w - u p s were performed on the mean s c o r e s f o r AU9, u s i n g 73 the Tukey method, w i t h a a g a i n s e t a t 0 .005 . These a n a l y s e s i n d i c a t e d t h a t 2 month o l d i n f a n t s d i s p l a y e d more l e v a t o r c o n t r a c t i o n than 4, 6 and 12 m o n t h - o l d i n f a n t s . The mean s c o r e s on L e v a t o r C o n t r a c t i o n and Brow Lower f o r a l l 5 age groups a r e d i s p l a y e d i n F i g u r e 7. F o l l o w - u p a n a l y s e s on t h e main e f f e c t o f event were conducted i n the form o f p a i r e d t - t e s t s f o r each o f the f a c i a l v a r i a b l e s , w i t h a dropped t o 0 .005 . The r e s u l t s a r e p r o v i d e d i n T a b l e 17. 74 CD  M  O  O  CO  P fl)  C D  g  T a b l e 17 R e s u l t s : Baby FACS A c t i o n s by Event A c t i o n U n i t t E AU1-Inner Brow R a i s e 0.75 >.40 AU3-Brow K n i t 10.32 <.001 AU4-Brow Lower 10.92 <.001 A U 6 / A U 7 - O r b i t T i g h t e n i n g 11.27 <.001 A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n 13.57 <.001 AU17-Chin R a i s e 2.48 <.02 AU26-Jaw Drop 9.68 <.001 AU43-Eyes C l o s e d 10.19 <.001 AU44-Squ in t 3.03 <.005 AU75d-Tense , Concave Tongue 6.96 <.001 The a n a l y s e s r e v e a l e d t h a t the f o l l o w i n g v a r i a b l e s o c c u r r e d more f r e q u e n t l y d u r i n g the " i n j e c t i o n " event than t h e " b a s e l i n e " e v e n t : AU3-Brow K n i t , AU4-Brow Lower, A U 6 / 7 - 0 r b i t T i g h t e n i n g , A U 9 / 1 0 - L e v a t o r C o n t r a c t i o n , AU26-Jaw D r o p , AU43-Eyes C l o s e d , A U 4 4 - S q u i n t , and AU75d-Tense , Concave Tongue. AU 1 7 - C h i n R a i s e was a l s o more f r e q u e n t d u r i n g the " i n j e c t i o n " event b u t t h i s f i n d i n g d i d not r e a c h s i g n i f i c a n c e . A U l - I n n e r Brow R a i s e d i d not d i s c r i m i n a t e between the two e v e n t s . 76 A n a l y s e s conducted on the " r e c o v e r y ' ' e v e n t . The r e l a t i o n s h i p between age and q u a l i t a t i v e changes i n the f a c i a l e x p r e s s i o n o f p a i n d u r i n g t h e " r e c o v e r y " event was examined by c o n d u c t i n g a oneway MANOVA w i t h the f i v e l e v e l s o f age as the independent v a r i a b l e and the v a r i o u s f a c i a l a c t i o n s as dependent v a r i a b l e s . Once a g a i n , t h i s was conducted s e p a r a t e l y f o r each o f the c o d i n g sys tems . C e l l means and s t a n d a r d d e v i a t i o n s o b t a i n e d from t h i s a n a l y s i s f o r the NFCS d a t a a r e g i v e n i n T a b l e 18. T a b l e 18 C e l l Means and S t a n d a r d D e v i a t i o n s : NFCS A c t i o n s by Age Age g r o u p : A c t i o n U n i t 2 Months 4 Months 6 Months 12 Months 18 Months Brow Bulge M SD 4.10 1.52 2.03 1.57 4.20 1.14 3.43 1.71 4.35 0.87 Eye Squeeze M SD 3.00 1.89 0.58 1.58 2.10 2.08 1.58 1.83 1.50 1.72 Deepened Naso- l a b i a l Furrow M SD 3.60 1.96 1.83 1.76 4.00 1.49 3.38 1.10 4.38 0.84 Open L i p s M SD 4.23 1.60 3.70 2.06 4.60 0.97 4.35 1.42 4.55 0.67 Taut Tongue M SD 1.70 2.06 0.22 0.46 0.60 1.08 0.95 1.17 0.00 0.00 n=10 The main e f f e c t o f age group ( F ( 2 0 , 137)=1.86, p_<.05) was s i g n i f i c a n t . F o l l o w - u p a n a l y s e s were conducted i n the form o f 5 J 77 oneway ANOVAs on the i n d i v i d u a l f a c i a l a c t i o n v a r i a b l e s , w i t h a a t the 0.005 l e v e l . The r e s u l t s a r e g i v e n i n T a b l e 19. T a b l e 19 U n i v a r i a t e R e s u l t s : NFCS A c t i o n s by Age A c t i o n U n i t F p_ Brow Bulge 4.72 <.005 Eye Squeeze 2.37 <.10 Deepened N a s o l a b i a l Furrow 4.30 <.005 Open L i p s 0.64 >.50 Taut Tongue 3.23 <.05 n=10 A c c o r d i n g t o the <x=0.005 c r i t e r i o n , s i g n i f i c a n t r e s u l t s were o b t a i n e d f o r Brow Bulge and Deepened N a s o l a b i a l F u r r o w . Trends were p r e s e n t f o r T a u t Tongue and Eye Squeeze . F o l l o w - u p a n a l y s e s (Tukey, a=0.005) on Brow Bulge and N a s o l a b i a l Furrow r e v e a l e d t h a t 18 month o l d i n f a n t s d i s p l a y e d more brow b u l g e and deepened n a s o l a b i a l furrow than 4-mpnth o l d i n f a n t s , and t h a t 6- month o l d i n f a n t s d i s p l a y e d more deepened n a s o l a b i a l furrow t h a n 4 month o l d i n f a n t s . F i g u r e 8 d e p i c t s the means f o r each age g r o u p . I n s p e c t i o n o f the means f o r Eye Squeeze and T a u t Tongue sugges ted t h a t 2-month o l d i n f a n t s d i s p l a y e d more eye squeeze than 4-month o l d i n f a n t s , and t h a t 2-month o l d i n f a n t s d i s p l a y e d more t a u t tongue t h a n 18-month o l d i n f a n t s . C e l l means and s t a n d a r d d e v i a t i o n s o b t a i n e d from the Baby FACS c o d i n g are g i v e n i n T a b l e 20. 78 61  (D  M  o  O  to  p c u f D ^  —̂  r o ro  co  co  bi b in  b  in  > (D Q O C ^ * in  u i o in  o in  o O  rt  i— * to  o rt  0 rt  ET  w  l l i i i ^ l l i l l l l l l l l CD  O  O  <J  CD  CD  < CD  rt  2 u CD  U l CD  o 0 •0  h- 1 CD  rjd  cr  CD  H - i— 1 iQ  r— 1 CD  Hi  0 3 H H - H - < H- CO  r— 1 I2J  o CO  >•  o rt H- 0 Hi  U l tr  > (D T a b l e 20 C e l l Means and S t a n d a r d D e v i a t i o n s : Baby FACS A c t i o n s by Age Age g r o u p : A c t i o n 2 4 6 12 18 U n i t Months Months Months Months Months 1 Inner M 0.10 0.48 1.73 0.60 0.48 Brow SD 0.32 0.84 2.69 1.35 0.50 R a i s e 3 Brow M 9.03 2.48 6.26 7.98 8.59 K n i t SD 7.12 2.31 4.71 5.25 5.48 4 Brow M 8.80 3.03 5.06 4.02 8.48 Lower SD 7.45 4.73 4.84 4.07 4.80 6/7 O r b i t M 10.90 3.17 7.85 8.22 8.65 T i g h t e n - SD 6.03 3.75 6.00 5.73 7.00 i n g 9/10 L e v a t o r M 10.50 4.23 7.85 10.67 10.90 C o n t r a c t SD 6.45 6.62 6.42 5.37 5.15 - i o n 17 C h i n M 3.20 1.22 2.30 3.35 3.00 R a i s e SD 6.25 3.46 3.83 5.21 5.49 26 Jaw M 15.90 12.25 13.70 12.27 14.45 Drop SD 7.28 3.97 3.36 4.68 3.81 43 Eyes M 6.10 1.79 5.48 3.43 4.08 C l o s e d SD 7.39 3.17 5.29 6.27 5.86 44 S q u i n t M 3.20 0.68 2.70 1.67 2.28 SD 6.48 1.62 5.46 3.33 4.03 75d Tense , M 1.20 0.03 0.73 1.27 0.55 Concave SD 0.08 1.35 1.64 0.93 Tongue 2.098 80 The main e f f e c t o f age group was not s i g n i f i c a n t f o r the Baby FACS a c t i o n s d u r i n g the " r e c o v e r y " event (F(40 ,138)=1.2 E<.20) . DISCUSSION F a c i a l A c t i o n s E x p r e s s i n g P a i n i n I n f a n t s The p r e s e n t s tudy i s c o n s i s t e n t w i t h the l i t e r a t u r e on p a i n i n neonates ( e . g . , C r a i g & Grunau , 1993; J o h n s t o n e t a l . , 1993) i n i d e n t i f y i n g a c o n s t e l l a t i o n o f f a c i a l a c t i o n s t h a t o c c u r i n response t o a p a i n f u l e v e n t . H i g h e r s c o r e s were o b t a i n e d immedia te ly f o l l o w i n g the i n j e c t i o n than d u r i n g the b a s e l i n e p e r i o d f o r these a c t i o n s : NFCS Brow B u l g e , NFCS Eye Squeeze , NFCS Deepened N a s o l a b i a l F u r r o w , NFCS Open L i p s , NFCS T a u t Tongue, Baby FACS AU3-Brow K n i t , Baby FACS AU4-Brow Lower, Baby FACS A U 6 / A U 7 - O r b i t T i g h t e n i n g , Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n , Baby FACS AU26-Jaw Drop , Baby FACS AU43-Eyes C l o s e d , and Baby FACS AU75d-Tense , Concave Tongue. Thus the i n f a n t s responded by l o w e r i n g and drawing t o g e t h e r t h e i r brows, t i g h t e n i n g the musc les around t h e i r e y e s , c l o s i n g t h e i r e y e s , deepening t h e i r n a s o l a b i a l f u r r o w s , open ing t h e i r mouths and d i s p l a y i n g a t e n s e , cupped tongue . P r i n c i p a l components a n a l y s e s de termined t h a t a s i n g l e f a c t o r s o l u t i o n was most a p p r o p r i a t e f o r each c o d i n g sys tem, which i s c o n s i s t e n t w i t h the v iew t h a t the d i f f e r e n t a c t i o n s r e f l e c t a s i n g l e u n d e r l y i n g c o n s t r u c t , t h a t o f p a i n . These f i n d i n g s are l a r g e l y c o n s i s t e n t w i t h o t h e r d e s c r i p t i o n s o f t h e i n f a n t p a i n e x p r e s s i o n . F o r example, the i n f a n t p a i n e x p r e s s i o n , as d e f i n e d i n I z a r d ' s MAX system (1979) c o n s i s t s o f s h a r p l y lowered and drawn t o g e t h e r brows w i t h b u l g e s between them, v e r t i c a l furrows oh the f o r e h e a d , a broadened b u l g i n g n a s a l r o o t , t i g h t l y c l o s e d eyes w i t h a h o r i z o n t a l furrow 82 o f the upper l i d , r a i s e d cheeks w i t h an i n c r e a s e i n t i s s u e mass, a deepening o f the n a s o l a b i a l f o l d , and an open, s q u a r i s h , a n g u l a r mouth. U s i n g NFCS, Grunau e t a l . , (1990) i d e n t i f i e d the c l u s t e r o f lowered brow, deepened n a s o - l a b i a l f u r r o w , eyes squeezed s h u t , open l i p s , and a t a u t , cupped tongue , which i s p e r f e c t l y c o n s i s t e n t w i t h the p r e s e n t s t u d y . S i m i l a r r e s u l t s were o b t a i n e d by Grunau and C r a i g (1987) and J o h n s t o n e t a l . (1993) . W h i l e the use o f Baby FACS i n the s t u d y o f n e o n a t a l p a i n has been i n f r e q u e n t , C r a i g e t a l . (1994) used an e a r l i e r v e r s i o n o f Baby FACS ( O s t e r & R o s e n s t e i n , 1982) i n c o d i n g the f a c i a l e x p r e s s i o n s o f p r e t e r m and f u l l t e r m i n f a n t s u n d e r g o i n g h e e l l a n c e . They found t h a t the f o l l o w i n g a c t i o n s were common immedia te ly f o l l o w i n g a p a i n f u l s t i m u l u s : AU4-Brow Lower, AU6-Cheek R a i s e , A U 1 2 - L i p C o r n e r P u l l , A U 2 5 - L i p s P a r t , AU26-Jaw D r o p , and AU43- Eyes C l o s e d . A l l but AUs 25 and 43 were s i g n i f i c a n t l y more f r e q u e n t f o l l o w i n g h e e l l a n c e t h a n d u r i n g a p r e l i m i n a r y swabbing. In the p r e s e n t s t u d y , seven f a c i a l a c t i o n s o c c u r r e d w i t h s u f f i c i e n t f r e q u e n c y t o be i n c l u d e d i n the a n a l y s i s , and showed a s i g n i f i c a n t d i f f e r e n c e between t h e " b a s e l i n e " and " i n j e c t i o n " e v e n t s . Three o f t h e s e , AUs 4, 6, and 26, were among those i d e n t i f i e d by C r a i g e t a l (1994) . However, i n c o n t r a s t t o the p r e v i o u s f i n d i n g s ( C r a i g e t a l . , 1994) , AUs 3, 9 /10 , 43, and 75d, d i d d i f f e r s i g n i f i c a n t l y between " b a s e l i n e " and " i n j e c t i o n " segments i n the p r e s e n t s t u d y . T h i s f i n d i n g may be due t o the a d d i t i o n o f i n t e n s i t y c o d i n g , which was no t done i n the e a r l i e r s t u d y . As w e l l , most o f the i n f a n t s s t u d i e d by C r a i g e t a l . were premature . C o n s e q u e n t l y , age 83 d i f f e r e n c e s may be r e s p o n s i b l e f o r d i s c r e p a n t f i n d i n g s . A U 9 / 1 0 - L e v a t o r C o n t r a c t i o n and AU43-Eyes C l o s e d have been o b s e r v e d i n s t u d i e s o f a d u l t f a c i a l e x p r e s s i o n s o f p a i n u s i n g the FACS system ( e . g . , H a d j i s t a v r o p o u l o s & C r a i g , 1994) . AUs 3-Brow K n i t and 75d-Tense , Concave Tongue a r e not s c o r e d i n a d u l t s , as t h e y a r e m o d i f i c a t i o n s added t o FACS t o make i t more s u i t a b l e f o r use w i t h i n f a n t s ( O s t e r & R o s e n s t e i n , 1982) . Temperament and the F a c i a l E x p r e s s i o n o f P a i n I n f a n t s show c o n s i d e r a b l e v a r i a b i l i t y i n t h e i r response t o p a i n f u l s t i m u l i (Grunau e t a l . , 1990) . C o n s e q u e n t l y , r e s e a r c h e r s have s p e c u l a t e d t h a t i n d i v i d u a l d i f f e r e n c e f a c t o r s such as temperament may p l a y a r o l e ( e . g . , Grunau & C r a i g , 1987; Grunau e t a l , 1990; H a m i l t o n & Z e l t z e r , 1994) . In the c u r r e n t s t u d y , i t was h y p o t h e s i z e d t h a t s c o r e s on a q u e s t i o n n a i r e measure o f the n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament would p r e d i c t the degree o f response t o a p a i n f u l s t i m u l u s . T h i s p r e d i c t i o n was not borne out by the r e s u l t s o f the s t u d y . When c o r r e l a t i o n s between p a i n summary s c o r e s and temperament s c o r e s were examined, the a b s o l u t e v a l u e o f r was v e r y s m a l l , r a n g i n g from .00 t o 0 .14 , and none o f the c o r r e l a t i o n s r e a c h e d s t a t i s t i c a l s i g n i f i c a n c e . T h i s f i n d i n g was unexpec ted . An a s s o c i a t i o n between n e g a t i v e e m o t i o n a l i t y and p a i n e x p r e s s i o n would seem ex treme ly l o g i c a l . The n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament r e f e r s t o i n d i v i d u a l d i f f e r e n c e s i n the f r e q u e n c y , i n t e n s i t y , and d u r a t i o n o f e x p r e s s i o n s o f n e g a t i v e a f f e c t . S i n c e p a i n i s a pr ime example o f n e g a t i v e a f f e c t i n the i n f a n t , i t would seem l i k e l y t h a t c h i l d r e n whose p a r e n t s r a t e d them as h i g h e r on n e g a t i v e e m o t i o n a l i t y ( i . e . " f u s s i e r " o r "more d i f f i c u l t " ) would 84 r e a c t t o immunizat ion w i t h g r e a t e r i n t e n s i t y ( s c o r i n g h i g h e r on p a i n summary s c o r e s ) . R e s e a r c h w i t h o l d e r c h i l d r e n has i d e n t i f i e d temperament as a p r e d i c t o r o f p a i n - r e l a t e d b e h a v i o u r s (Dav i son e t a l . , 1986; W a l l a c e , 1989; S c h e c h t e r e t a l . , 1991; Young & F u , 1988) . However, i t i s noteworthy t h a t a r e c e n t s tudy o f immuniza t ion p a i n i n i n f a n t s ( T a d d i o , Nulman, G o l d b a c h , I p p , & K o r e n , 1994) found no r e l a t i o n s h i p between temperament and p a i n s c o r e s . In l i g h t o f the n u l l f i n d i n g s , the power o f the p r e s e n t s t u d y was examined. I t was de termined t h a t the power t o d e t e c t a c o r r e l a t i o n o f medium magnitude (r=.30) d u r i n g the " i n j e c t i o n " event (n=75) was 0 .75 . A t the "recovery" e v e n t , where the sample s i z e dropped t o 55, power was 0 .62 . I t was c o n c l u d e d t h a t the s t u d y had moderate power t o d e t e c t a c o r r e l a t i o n i n the p o p u l a t i o n . However, the a c t u a l c o r r e l a t i o n s o b t a i n e d were v e r y s m a l l ( r = 0 . 1 4 ) , such t h a t even i f t h e s t u d y had s u f f i c i e n t power, and the r e s u l t s r eached s i g n i f i c a n c e , temperament would p r e d i c t 1.96% o f the v a r i a n c e i n p a i n r e s p o n s e , a p r o p o r t i o n o f l i t t l e p r a c t i c a l s i g n i f i c a n c e . I t i s u n l i k e l y t h a t the f a i l u r e t o f i n d the p r e d i c t e d r e l a t i o n s h i p was caused by low s t a t i s t i c a l power. There i s however, a second m e t h o d o l o g i c a l c o n c e r n i n t h a t t h e use o f p a r e n t r e p o r t q u e s t i o n n a i r e s i n the assessment o f temperament has been h e a v i l y c r i t i c i z e d . There i s c o n c e r n t h a t the i n s t r u m e n t s a r e t o o s u b j e c t i v e and r e f l e c t more about the p a r e n t t h a n the c h i l d . M a t e r n a l c h a r a c t e r i s t i c s , such as demographic and p e r s o n a l i t y v a r i a b l e s , have been found t o p r e d i c t q u e s t i o n n a i r e s c o r e s (Bates e t a l . , 1979; Vaughn, T a r a l d s o n , C r i c h t o n & E g e l a n d , 1981) . However, w h i l e i t i s n e c e s s a r y t o 85 acknowledge the s u b j e c t i v e component o f p a r e n t r e p o r t , t h e r e seems t o be an o b j e c t i v e component as w e l l . F o r example, p a r e n t r e p o r t s c o r r e l a t e w i t h home o b s e r v a t i o n measures (Bates e t a l . , 1979) , c h a r a c t e r i s t i c s o f c r y i n g i n c l u d i n g f r e q u e n c y , d u r a t i o n , and p e r c e i v e d a v e r s i v e n e s s ( B a r r , Kramer , P l e s s , B o i s j o l y , & L e d u c , 1989; Lounsbury & B a t e s , 1982) , and the a d r e n o c o r t i c a l re sponse t o l a b o r a t o r y t e s t s i n v o l v i n g m a t e r n a l s e p a r a t i o n (Gunnar, M a n g e l s d o r f , L a r s o n , & H e r t s g a a r d , 1989) . C o n s e q u e n t l y , Bates (1992) has argued t h a t p a r e n t r e p o r t measures d e l i v e r "the most meaning f o r t h e c o s t " and recommends t h e i r use as a f i r s t probe i n u n r e s e a r c h e d a r e a s . In a d d i t i o n t o c o n c e r n s about v a l i d i t y , Hubert e t a l . (1982) rev iewed the a v a i l a b l e i n s t r u m e n t s and c o n c l u d e d t h a t "no s i n g l e p s y c h o m e t r i c a l l y adequate i n s t r u m e n t i s a v a i l a b l e " (p . 571) . However, t h e " F u s s y / D i f f i c u l t " d imens ion o f the I n f a n t C h a r a c t e r i s t i c s Q u e s t i o n n a i r e used i n the p r e s e n t s tudy has shown h i g h t e s t - r e t e s t r e l i a b i l i t y and moderate t o h i g h s t a b i l i t y , prompt ing Hubert e t a l . (1982) t o recommend i t s use f o r the assessment o f d i f f i c u l t temperament. W h i l e the assessment o f temperament remains i m p e r f e c t , i t s shor tcomings p r o b a b l y do no t account f o r the h u l l f i n d i n g s d i s c u s s e d h e r e . A f i n a l m e t h o d o l o g i c a l c o n c e r n r e l a t e s t o the f a c t t h a t the dependent measures used i n the p r e s e n t s t u d y were summary s c o r e s . No at tempt was made t o t e a s e a p a r t the d imens ions o f f r e q u e n c y and i n t e n s i t y o f the e x p r e s s i o n o f p a i n . I t i s p o s s i b l e t h a t temperament p r e d i c t s one o f t h e s e , and t h a t such a r e l a t i o n s h i p was o b s c u r e d by the compos i te measure used i n t h e p r e s e n t s t u d y . 86 The q u e s t i o n t h a t prompted the c u r r e n t s tudy remains unanswered. S u b s t a n t i a l i n d i v i d u a l d i f f e r e n c e s i n the response t o p a i n f u l s t i m u l i were observed i n the p r e s e n t s t u d y and i n p r e v i o u s r e s e a r c h (Grunau e t a l . , 1990) . F u r t h e r m o r e , t h e r e i s e v i d e n c e o f moderate s t a b i l i t y i n the response t o p a i n . F o r example , Worobey and Lewis (1989) found t h a t r e a c t i v i t y t o h e e l s t i c k a t 2 days o f age c o r r e l a t e d w i t h r e a c t i v i t y t o DPT i n j e c t i o n a t 2 months o f age . I z a r d e t a l . (1987) found t h a t the amount o f t ime t h a t an i n f a n t d i s p l a y e d the f a c i a l e x p r e s s i o n o f "anger" r a t h e r t h a n "pa in" f o l l o w i n g immuniza t ion remained s t a b l e from 2 t o 19 months. I t s h o u l d be noted t h a t the l o n g - t e r m s t a b i l i t y o f the f a c i a l e x p r e s s i o n o f p a i n as indexed i n t h e p r e s e n t s tudy ( i . e . by NFCS o r Baby FACS) has not been f i r m l y e s t a b l i s h e d , a l t h o u g h the I z a r d e t a l . (1987) f i n d i n g i s s u g g e s t i v e . I f such s t a b i l i t y i n response t o p a i n f u l s t i m u l i e x i s t s , i t would suggest some d i s p o s i t i o n a l f a c t o r o r t r a i t . However, the r e s u l t s o f t h e p r e s e n t s tudy sugges t t h a t such a t r a i t i s independent o f the n e g a t i v e e m o t i o n a l i t y d imen s ion o f temperament. What might account f o r i n d i v i d u a l d i f f e r e n c e s i n response t o p a i n s t i m u l i ? One r e c e n t r e p o r t sugges t s t h a t p r e v i o u s p a i n e x p e r i e n c e s may p l a y an i m p o r t a n t r o l e . T a d d i o e t a l . (1995) found t h a t male i n f a n t s who had undergone c i r c u m c i s i o n r e c e i v e d h i g h e r p a i n s c o r e s f o l l o w i n g immunizat ion i n j e c t i o n s a t 4 and 6 months o f age , r e l a t i v e t o u n c i r c u m c i s e d i n f a n t s . C i r c u m c i s e d i n f a n t s c r i e d l o n g e r f o l l o w i n g the i n j e c t i o n and r e c e i v e d h i g h e r s c o r e s on a compos i te p a i n measure d e r i v e d from c r y , f a c i a l e x p r e s s i o n , and body movements. I t i s p o s s i b l e t h a t c h i l d r e n who 87 a r e s u b j e c t e d t o more p a i n f u l s t i m u l i become s e n s i t i z e d and respond t o p a i n w i t h g r e a t e r i n t e n s i t y . However, the a n a l y s i s conducted by T a d d i o e t a l . (1995) was p o s t - h o c i n n a t u r e and needs t o be r e p l i c a t e d . I t i s c o n s i s t e n t w i t h e v i d e n c e s u g g e s t i n g t h a t t o d d l e r s who e x p e r i e n c e d p r o l o n g e d h o s p i t a l i z a t i o n and m u l t i p l e p a i n f u l p r o c e d u r e s as i n f a n t s d i f f e r from normal c o n t r o l s on measures o f p a i n s e n s i t i v i t y and s o m a t i z a t i o n (Grunau, W h i t f i e l d & P e t r i e , 1994; G r u n a u , W h i t f i e l d , P e t r i e , & F r y e r , 1994) . The p r e s e n t s t u d y f a i l s t o c o n f i r m e x p e c t a t i o n s t h a t temperament mediates the response t o p a i n f u l s t i m u l i . In o r d e r t o e l u c i d a t e the f a c t o r s b e h i n d i n d i v i d u a l d i f f e r e n c e s i n response t o p a i n f u l s t i m u l i , i t w i l l be n e c e s s a r y t o f i r s t e s t a b l i s h whether t h e p a i n response remains s t a b l e a c r o s s age . L o n g i t u d i n a l s t u d i e s , though d i f f i c u l t t o e x e c u t e , a r e s o r e l y needed. I f s t a b i l i t y o f response i s d e t e r m i n e d , r e s e a r c h e r s s h o u l d f u r t h e r i n v e s t i g a t e the r o l e o f p r e v i o u s p a i n e x p e r i e n c e . A n a t o m i c a l v a r i a t i o n s may a l s o be o f i n t e r e s t . D u r i n g the p r e s e n t s t u d y , one o f the nurse s h y p o t h e s i z e d t h a t the m u s c u l a t u r e o f the i n f a n t may mediate the p a i n response ("I t ' s the s k i n n y ones t h a t s cream") . I f the p a i n response does no t prove t o be s t a b l e w i t h age , a t t e n t i o n s h o u l d be f o c u s s e d on v a r i a b i l i t y r e l a t i n g t o s i t u a t i o n a l f a c t o r s . Other f a c t o r s such as the e x p e r i e n c e o f the n u r s e , the a n x i e t y l e v e l o f the p a r e n t , o r the p h y s i o l o g i c a l s t a t e o f the i n f a n t p r i o r t o the i n j e c t i o n may a l s o p l a y a r o l e . I t i s l i k e l y t h a t b o t h d i s p o s i t i o n a l and s i t u a t i o n a l f a c t o r s have an e f f e c t . 88 Developmental Changes i n the F a c i a l E x p r e s s i o n o f P a i n i n I n f a n t s The p r e s e n t s tudy a l s o aimed t o p r e s e n t a d e s c r i p t i v e account o f a g e - r e l a t e d changes i n the f a c i a l re sponse t o a p a i n f u l s t i m u l u s . A g e - l i n k e d changes i n the degree o f p a i n expres sed w i l l be d i s c u s s e d f i r s t . The a n a l y s e s r e v e a l e d t h a t 2 month o l d i n f a n t s s c o r e d h i g h e r than 4 month o l d i n f a n t s on p a i n summary s c o r e s d e r i v e d from the NFCS c o d i n g . S i m i l a r l y , 2 month o l d i n f a n t s s c o r e d h i g h e r t h a n 4 and 6 month o l d i n f a n t s on summary s c o r e s d e r i v e d from the Baby FACS c o d i n g . In the "recovery" p e r i o d , b o t h 18-month o l d i n f a n t s and 6-month o l d i n f a n t s s c o r e d h i g h e r than 4-month o l d i n f a n t s on t h e p a i n summary s c o r e s d e r i v e d from NFCS c o d i n g . No o t h e r d i f f e r e n c e s were s i g n i f i c a n t . Of the f i v e s i g n i f i c a n t d i f f e r e n c e s , f o u r i n v o l v e d the 4-month age g r o u p , s u g g e s t i n g a d i p i n the i n t e n s i t y o f p a i n expres sed a t t h a t age . Such a decrease may r e f l e c t e i t h e r a change i n the i n t e n s i t y o f the p a i n e x p e r i e n c e d , o r a change i n e x p r e s s i o n independent o f what i s f e l t . I t was s u r p r i s i n g t h a t , i n the a n a l y s e s conducted on the " b a s e l i n e " and " i n j e c t i o n " e v e n t s , t h e i n t e r a c t i o n between age and event d i d no t r e a c h s i g n i f i c a n c e . T h i s i n d i c a t e s t h a t the 2- month o l d i n f a n t s r e c e i v e d h i g h e r p a i n s c o r e s t h a n o t h e r groups d u r i n g b o t h e v e n t s , i . e . even b e f o r e the p a i n s t i m u l u s was i n t r o d u c e d . I t i s thus p o s s i b l e t h a t the youngest i n f a n t s r e a c t e d t o the r e l a t i v e l y low l e v e l s t i m u l a t i o n o f the b a s e l i n e p e r i o d ( such as b e i n g undres sed and p o s i t i o n e d f o r the i n j e c t i o n ) w i t h d i s t r e s s , and c o n t i n u e d t o r e a c t t o t h e i n j e c t i o n w i t h g r e a t e r i n t e n s i t y . In f a c t , i n s p e c t i o n o f the means f o r each age 89 group f o r each event (see T a b l e 10 and 11) s u p p o r t t h i s h y p o t h e s i s , as the d i f f e r e n c e between the 2-month o l d i n f a n t s and o t h e r groups i s a c t u a l l y g r e a t e s t d u r i n g t h e " b a s e l i n e " e v e n t . P o s s i b l y , an a n a l y s i s o f c o v a r i a n c e would have been a p p r o p r i a t e . N e v e r t h e l e s s , the deve lopmenta l changes t h a t were uncovered i n i t h i s p e r i o d a r e c o n s i s t e n t w i t h p r e v i o u s r e s e a r c h , and i t i s b e l i e v e d t h a t they r e p r e s e n t c o n s i s t e n t d i f f e r e n c e s i n the p a i n e x p r e s s i o n . P r e v i o u s r e s e a r c h , w h i l e r a n g i n g w i d e l y i n the i n d i c e s o f p a i n u s e d , s u p p o r t s the n o t i o n o f a decrease i n t h e i n t e n s i t y o f p h y s i o l o g i c a l and b e h a v i o u r a l responses t o p a i n around the age o f 4 months. F o r example, Lewis and Thomas (1990) s t u d i e d the r i s e i n C o r t i s o l (a s t r e s s hormone) f o l l o w i n g DPT i n j e c t i o n , and found t h a t the i n c r e a s e was g r e a t e r i n 2-month o l d i n f a n t s than i n 4- month o l d i n f a n t s . In b e h a v i o u r a l a n a l y s e s ( the dependent v a r i a b l e combined f a c i a l e x p r e s s i o n and c r y ) , the 2- and 4- month o l d groups d i d no t d i f f e r , but 6-morith i n f a n t s q u i e t e d f a s t e r t h a n e i t h e r o f the two younger g r o u p s . Ramsay and jLewis (1994) found t h a t , f o r those i n f a n t s showing a r i s e i n C o r t i s o l , 2-month o l d i n f a n t s showed a more i n t e n s e p a i n r e a c t i o n and a g r e a t e r i n c r e a s e i n C o r t i s o l than 6-month o l d i n f a n t s . M a i k l e r (1991) , s t u d y i n g i n f a n t s aged 2-6 months, s p l i t h e r sample i n t o two g r o u p s , under 16 weeks and over 16 weeks ( a p p r o x i m a t e l y 4 months ) . She found t h a t t h e d u r a t i o n o f the p a i n e x p r e s s i o n , as measured by f a c i a l e x p r e s s i o n , c r y , and body movement, was l o n g e r f o r the younger g r o u p . She a l s o n o t e d t h a t " e x c e p t i o n a l l y d r a m a t i c b e h a v i o r [was] observed i n the younger i n f a n t s . T h e i r b e h a v i o r was g e n e r a l l y c h a r a c t e r i z e d by the r i g i d e x t e n s i o n o f 90 a l l e x t r e m i t i e s and i n t e n s e c r y i n g " (p . 402) . Taken as a whole , the a v a i l a b l e e v i d e n c e sugges t s a drop i n t h e degree o f response t o p a i n f u l s t i m u l i a t a p p r o x i m a t e l y 4 months o f age . However, the p r e s e n t s tudy found l i t t l e e v i d e n c e o f a l i n e a r decrease i n the p a i n response o v e r the f i r s t 2 y e a r s o f l i f e . The d a t a were a t l e a s t s u g g e s t i v e o f a l a t e r i n c r e a s e i n the degree o f p a i n r e s p o n s e , i n t h a t 18-month o l d i n f a n t s and 6-month o l d i n f a n t s s c o r e d h i g h e r t h a n the 4-month group on the NFCS p a i n summary s c o r e d u r i n g the "recovery" e v e n t . S i n c e these d i f f e r e n c e s were no t s i g n i f i c a n t immedia te ly a f t e r t h e i n j e c t i o n , i t seems l i k e l y t h a t o l d e r i n f a n t s do not i n i t i a l l y re spond w i t h g r e a t e r i n t e n s i t y t h a n t h e 4-month o l d s . I n s t e a d , i t h e y t a k e l o n g e r t o q u i e t , such t h a t 20 seconds a f t e r the i n j e c t i o n , they i a r e s t i l l a c h i e v i n g h i g h s c o r e s on the p a i n summary measure. Beyond the age o f 6 months, t h e r e i s a d e a r t h J o f i n f o r m a t i o n on deve lopmenta l changes i n the p a i n r e s p o n s e . I z a r d e t a l . (1983) found t h a t the d u r a t i o n o f the " p h y s i c a l d i s t r e s s " e x p r e s s i o n was s h o r t e r i n 19 month o l d i n f a n t s t h a n i n 2-month o l d i n f a n t s o r 6-month o l d i n f a n t s . These r e s u l t s iwere r e p l i c a t e d by I z a r d , Hembree, and Huebner i n 1987. However, the i d u r a t i o n o f the "anger" e x p r e s s i o n was found t o i n c r e a s e w i t h age . The " p h y s i c a l d i s t r e s s " and "anger" e x p r e s s i o n s a r e a c t u a l l y ex tremely s i m i l a r ( O s t e r e t a l . , 1992) , y e t t h e y were t r e a t e d as m u t u a l l y e x c l u s i v e i n I z a r d ' s s t u d i e s . C o n s e q u e n t l y , i f I z a r d ' s d a t a were coded w i t h NFCS o r Baby FACS a d i f f e r e n t c o n c l u s i o n may have been r e a c h e d , and i t i s d i f f i c u l t t o compare the r e s u l t s t o the p r e s e n t s t u d y . 91 I W h i l e p r o p e r t i e s o f the s t i m u l u s were confounded w i t h age ( i . e . the 12-month o l d i n f a n t s r e c e i v e d a d i f f e r e n t i n j e c t i o n , a d m i n i s t e r e d t o the arm r a t h e r t h a n the l e g ) i t i s u n l i k e l y t h a t t h i s a f f e c t e d the c o n c l u s i o n s s u b s t a n t i a l l y . In f a c t , the i n f a n t s i n the 12-month group were not found t o be s i g n i f i c a n t l y d i f f e r e n t from o t h e r age groups on any o f the v a r i a b l e s . However, i t remains p o s s i b l e t h a t d i f f e r e n c e s t h a t might o t h e r w i s e have been i d e n t i f i e d were o b s c u r e d by t h i s c o n f o u n d . A n a l y s e s o f the r e l a t i o n s h i p between age group and v a r i o u s background c h a r a c t e r i s t i c s d i d not i d e n t i f y any f a c t o r s confounded w i t h the age d i s t r i b u t i o n . However, i t was no ted t h a t t h e r e were d i f f e r e n c e s i n the i n t e r v e n t i o n s p a r e n t s chose t o soothe i n f a n t s o f d i f f e r e n t ages . There was a g e n e r a l d e c r e a s e w i t h age i n h o l d i n g l a t e r a l l y ( c r a d l i n g the i n f a n t f a c e u p ) . As w e l l , p a r e n t s were more l i k e l y t o h o l d t h e i r c h i l d v e n t r a l l y i (w i th t h e c h i l d ' s c h e s t towards t h e c a r e g i v e r ' s s h o u l d e r ) d u r i n g the 12-month MMR i n j e c t i o n . These d i f f e r e n c e s a r e l i k e l y mediated by p r a c t i c a l c o n c e r n s : i t i s c o n s i d e r a b l y more d i f f i c u l t t o c r a d l e a t o d d l e r than an i n f a n t . S i n c e the MMR immuniza t ion was the o n l y s h o t a d m i n i s t e r e d i n t h e arm, the v e n t r a l p o s i t i o n i p r o b a b l y a l l o w e d the n u r s e e a s i e r acces s t o the c h i l d and p r o t e c t e d the s o r e arm from i n a d v e r t a n t c o n t a c t w i t h the mother . I t remains p l a u s i b l e t h a t d i f f e r e n c e s i n p a r e n t a l s o o t h i n g s t y l e c o n t r i b u t e d t o d i f f e r e n c e s i n the p a i n r e s p o n s e , but they do not seem t o e x p l a i n the r e s u l t s . i I t i s p o s s i b l e t o s p e c u l a t e about t h e reasons f o r the observed deve lopmenta l changes . A number o f a l t e r n a t i v e s e x i s t , i n c l u d i n g p h y s i c a l m a t u r a t i o n , change i n c o g n i t i v e c a p a c i t i e s , i 92 I changes i n a f f e c t , and the e f f e c t s o f s o c i a l i z a t i o n . In a d d i t i o n , these f a c t o r s a r e l i k e l y t o i n t e r a c t . W h i l e the b a s i c p h y s i o l o g i c a l mechanisms n e c e s s a r y f o r the p e r c e p t i o n o f p a i n a r e i n p l a c e a t b i r t h (Anand & G a r r , 1989) , the nervous system c o n t i n u e s t o d e v e l o p as the c h i l d grows. T h i s development may be m a n i f e s t e d i n a g e - r e l a t e d d i f f e r e n c e s i n the p a i n r e s p o n s e . U s i n g the cutaneous f l e x o r r e f l e x as an index o f p a i n , F i t z g e r a l d , Shaw, and M c i n t o s h (1988) d e t e r m i n e d t h a t p r e t e r m neonates were h y p e r s e n s i t i v e t o n o c i c e p t i v e i n p u t ( the a p p l i c a t i o n o f graded von F r e y h a i r s ) i n compar i son w i t h f u l l t e r m i neonate s . I t was h y p o t h e s i z e d t h a t the a g e - r e l a t e d i n c r e a s e i n p a i n t h r e s h o l d s r e f l e c t e d the m a t u r a t i o n o f i n h i b i t o r y c o n t r o l s d e s c e n d i n g from the b r a i n t o the s p i n a l c o r d . I t was f u r t h e r noted t h a t the t h r e s h o l d i n f u l l t e r m i n f a n t s ( l e s s t h a n 2g) was s t i l l much lower than t h a t found i n a d u l t s , which i s 30g o r h i g h e r . T h u s , the t h r e s h o l d must c o n t i n u e t o i n c r e a s e d u r i n g the p o s t n a t a l p e r i o d . W h i l e F i t z g e r a l d and h e r c o l l e a g u e s s t u d i e d t h e p a i n t h r e s h o l d r a t h e r t h a n the i n t e n s i t y o f r e s p o n s e , a change i n i n h i b i t o r y mechanisms would l i k e l y a f f e c t b o t h . C o n s e q u e n t l y , the observed decrease i n p a i n response a t a p p r o x i m a t e l y 4 months o f age may r e f l e c t the same p r o c e s s o f change t h a t has been sugges ted t o o c c u r i n younger i n f a n t s : the m a t u r a t i o n o f mechanisms which i n h i b i t the t r a n s m i s s i o n o f p a i n . A t t h i s p o i n t , i t i s n e c e s s a r y t o r e t u r n t o t h e model o f p a i n b e h a v i o u r and communicat ion ( C r a i g e t a l . , i n j p r e s s ) , and r e c o g n i z e the d i s t i n c t i o n between e x p r e s s i o n and e x p e r i e n c e . In s p i t e o f e v i d e n c e r e g a r d i n g the cutaneous f l e x o r r e f l e x ( F i t z g e r a l d e t a l . , 1988) and the p h y s i o l o g i c a l and m e t a b o l i c 93 s t r e s s response mounted by the p r e t e r m i n f a n t (Anand & H i c k e y , 1 9 8 7 ) , which suggest h y p e r s e n s i t i v i t y , s t u d i e s o f t h e premature i n f a n t ' s f a c i a l response t o p a i n ( e . g . , C r a i g e t a l . , 1 9 9 3 ) have sugges ted t h a t , r e l a t i v e t o f u l l t e r m newborns, pre terms show l e s s a c t i v i t y i n response t o p a i n f u l s t i m u l i . I t was c o n c l u d e d t h a t premature i n f a n t s a r e l e s s c a p a b l e o f e x p r e s s i n g t h e i r p a i n , but not l e s s c a p a b l e o f e x p e r i e n c i n g i t ( C r a i g e t a l . , J 1 9 9 3 ) . i In compar i son w i t h premature i n f a n t s , i t i s l i k e l y t h a t the 4-month o l d does have a g r e a t e r c a p a c i t y t o express the p a i n t h a t she f e e l s , s i n c e 4-month o l d i n f a n t s d i s p l a y g r e a t e r b e h a v i o u r a l o r g a n i z a t i o n i n a number o f r e a l m s . However, the p o i n t t h a t e x p e r i e n c e and e x p r e s s i o n a r e d i s t i n c t , though d i f f i c u l t t o d i f f e r e n t i a t e e x p e r i m e n t a l l y , i s w e l l t a k e n . The p r e s e n t s t u d y i s not a b l e t o d i f f e r e n t i a t e among the two, and i t ;is p o s s i b l e t h a t the d i f f e r e n c e s o b s e r v e d i n the 4 month age group were d i f f e r e n c e s i n the way i n the degree t o which p a i n and d i s t r e s s were expres sed r a t h e r t h a n the degree t o which they were e x p e r i e n c e d by t h e i n f a n t . F o r example , t h e s e changes may r e f l e c t a g r e a t e r degree o f s e l f - m o d u l a t i o n o r s e l f - c o n t r o l , such t h a t t h e r e i s l e s s need o f a d u l t i n t e r v e n t i o n and l e s s need t o communicate o n e ' s p a i n . F a c t o r s t h a t may u n d e r l i e the o b s e r v e d i n c r e a s e i n p a i n response f o r the 6 - and 18 -month o l d i n f a n t s d u r i n g t h e "recovery" event a l s o d e s e r v e a t t e n t i o n . One p o s s i b l e e x p l a n a t i o n emphasizes the r o l e o f c o g n i t i v e deve lopment . The o l d e r i n f a n t i s more c a p a b l e o f a t t r i b u t i n g meaning t o the s i t u a t i o n . T h i s may r e s u l t i n a more complex e m o t i o n a l r e a c t i o n t h a t t a k e s l o n g e r t o d e c a y . A t 6 - 8 months, p a i n b e g i n s t o be 94 confounded w i t h a n t i c i p a t o r y and c o n c u r r e n t a n x i e t y ( C r a i g & Grunau , 1991) . As w e l l , o l d e r i n f a n t s may be more l i k e l y t o express anger f o l l o w i n g immuniza t ion ( I z a r d e t a l . ; 1983; I z a r d e t a l . , 1987) . The l i t e r a t u r e on p a i n i n a d u l t s emphasizes the i n t e r - r e l a t i o n s o f p a i n and n e g a t i v e emotions such as a n g e r , f e a r , and sadness ( e . g . , Me lzack & W a l l , 1988) . In the i n f a n t l i t e r a t u r e , i I z a r d e t a l . (1983) have sugges ted t h a t n e g a t i v e emotions such as a n g e r , f e a r , and sadness may " a m p l i f y and s u s t a i n the o v e r a l l n e g a t i v e a f f e c t i v e e x p e r i e n c e " (p . 419) . S i m i l a r l y , P e t e r s o n , Harbeck , Farmer and Z i n k (1991) have noted t h a t i t i s d i f f i c u l t t o s e p a r a t e anger and a n x i e t y from a c h i l d ' s p a i n e x p e r i e n c e , and t h a t these emotions can r e s u l t i n a " s p i r a l i n g i n c r e a s e i n e x p e r i e n c e d p a i n " ( p . 4 4 ) . There i s e m p i r i c a l s u p p o r t f o r t h i s p r o p o s i t i o n i n t h a t the t ime r e q u i r e d f o r an i n f a n t t o q u i e t a f t e r immuniza t ion i s p o s i t i v e l y a s s o c i a t e d w i t h t h e p r o p o r t i o n i o f t ime t h a t the f a c i a l e x p r e s s i o n o f " a n g e r ' ' i s e x p r e s s e d ( I z a r d e t a l . , 1983) . T h u s , o l d e r i n f a n t s ' a b i l i t y t o e x t r a c t i n f o r m a t i o n from the s i t u a t i o n ( f o r example, t o r e a l i z e t h a t someone they t r u s t e d h e l d them so t h a t another a d u l t c o u l d s t i c k something sharp i n t o t h e i r s k i n ) may have caused them t o r e a c t w i t h o u t r a g e and a n x i e t y , which t h e n p r o l o n g e d o r i n t e n s i f i e d t h e i r e x p r e s s i o n s o f d i s t r e s s . We must once a g a i n acknowledge t h a t the observed age d i f f e r e n c e s may e x i s t i n the p e r c e p t i o n o f p a i n , t h e communicat ion o f what i s f e l t , o r b o t h . O l d e r i n f a n t s may not i e x p e r i e n c e more p a i n , but s i m p l y be more e f f e c t i v e i n e x p r e s s i n g i d i s t r e s s . They may a l s o have a c q u i r e d s o c i a l i z e d d i s p l a y r u l e s . 95 I t i s i n t e r e s t i n g t o note t h a t , i n the second y e a r o f l i f e , speech becomes a p r o g r e s s i v e l y more v i a b l e and u s e f u l t o o l f o r the c h i l d . T h i s s t u d y d i d not examine d i f f e r e n c e s i n c r y o r language . D e s p i t e the i n c r e a s e d a v a i l a b i l i t y and use o f speech , the f a c i a l e x p r e s s i o n remained an i m p o r t a n t mode o f e x p r e s s i o n f o r i n f a n t s over a y e a r o f age . T u r n i n g t o i n d i v i d u a l a c t i o n u n i t s , a number o f a g e - r e l a t e d changes were i d e n t i f i e d . In the " b a s e l i n e " and " i n j e c t i o n " p e r i o d s , a s i g n i f i c a n t d i f f e r e n c e was i d e n t i f i e d i n Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n . I t was de termined t h a t 2-month o l d i n f a n t s d i s p l a y e d more l e v a t o r c o n t r a c t i o n t h a n t h e 4 - , 6 - , o r 12-month o l d g r o u p s . A t r e n d on Baby FACS AU4-Brow Lower approached s i g n i f i c a n c e , s u g g e s t i n g t h a t 2-month o l d i n f a n t s a c h i e v e d h i g h e r s c o r e s on brow l o w e r i n g t h a n d i d 6-month o l d i n f a n t s . D u r i n g the "recovery" p e r i o d , d i f f e r e n c e s were r e v e a l e d i i n NFCS Brow Bulge and Deepened N a s o l a b i a l Furrow. A n a l y s e s de termined t h a t 4-month o l d i n f a n t s s c o r e d lower t h a n 18-month o l d i n f a n t s on brow b u l g e , and lower t h a n 6-month o l d i n f a n t s on deepened n a s o l a b i a l f u r r o w . These d i f f e r e n c e s a r e r o u g h l y c o n s i s t e n t w i t h the r e s u l t s o f i the p r e v i o u s a n a l y s e s i n s u g g e s t i n g t h a t 2-month o l d i n f a n t s d i f f e r e d from o t h e r groups d u r i n g the " b a s e l i n e " and " i n j e c t i o n " e v e n t s , and 4-month o l d i n f a n t s d i f f e r e d from o t h e r groups d u r i n g the "recovery" p e r i o d . A n a l y s e s on i n d i v i d u a l a c t i o n u n i t s sugges ted t h a t t h e r e a r e deve lopmenta l changes i n the f a c i a l a c t i o n s which (1) lower t h e eyebrows and draw them [together and (2) r a i s e the upper l i p and deepen t h e n a s o l a b i a l f u r r o w . The NFCS a c t i o n o f Brow Bulge and Baby FACS AU4-Brow Lower a r e 96 r o u g h l y s i m i l a r , as are NFCS Deepened N a s o l a b i a l Furrow and Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n . D e s p i t e t h i s s i m i l a r i t y , o n l y a c t i o n s from a s i n g l e c o d i n g system a c h i e v e d s i g n i f i c a n c e d u r i n g a g i v e n event (NFCS d u r i n g t h e " b a s e l i n e " and " i n j e c t i o n " e v e n t s , Baby FACS d u r i n g the " r e c o v e r y " e v e n t ) , s u g g e s t i n g t h a t the d i f f e r e n c e s a r e f a i r l y s u b t l e . The t a s k o f i n t e r p r e t i n g the r e s u l t s o f the two c o d i n g systems w i l l be d i s c u s s e d i n a l a t e r s e c t i o n . The o n l y p r e v i o u s i n v e s t i g a t i o n o f a g e - r e l a t e d changes i n i n d i v i d u a l a c t i o n u n i t s was conducted by J o h n s t o n e t a l . (1993) , S who compared premature , f u l l - t e r m , 2- and 4-month o l d i n f a n t s u s i n g NFCS c o d i n g . The p a i n s t i m u l u s was DPT i n j e c t i o n i n b o t h the 2 and 4 month g r o u p s . The 2- and 4-month o l d i n f a n t s were no t found t o d i f f e r on any o f the NFCS a c t i o n s . In l i g h t o f these c o n f l i c t i n g f i n d i n g s , and because o f t h e d i f f i c u l t y o f i n t e r p r e t i n g the p a t t e r n o f f i n d i n g s i n the p r e s e n t s t u d y , deve lopmenta l changes i n i n d i v i d u a l a c t i o n u n i t s s h o u l d be r e p l i c a t e d b e f o r e c o n c l u s i o n s a r e drawn. The f i n a l i s s u e t o be addres sed i n terms o f deve lopmenta l change i s the i s s u e o f a g e - r e l a t e d changes i n eye c l o s u r e . I z a r d and h i s c o l l e a g u e s ( I z a r d e t a l . , 1983; I z a r d e t a l . , 1987) have noted t h a t w i t h i n c r e a s i n g age , t h e f a c i a l e x p r e s s i o n o f anger becomes more p r e v a l e n t . Because the f a c i a l e x p r e s s i o n o f anger as d e f i n e d by MAX i s s i m i l a r t o t h e f a c i a l e x p r e s s i o n o f p a i n i n e v e r y d e t a i l but t h a t the eyes a r e open i n s t e a d o f t i g h t l y c l o s e d , i t was h y p o t h e s i z e d t h a t i n f a n t s would show an age- r e l a t e d decrease i n Baby FACS AU43-Eyes C l o s e d . A l t h o u g h the i means showed a s l i g h t d e c r e a s e w i t h age (see T a b l e s 15 and 20 ) , 97 i t d i d no t r e a c h s i g n i f i c a n c e . F u r t h e r r e s e a r c h w i l l be needed t o e v a l u a t e the c o n f l i c t i n g f i n d i n g s . There has been a c a l l f o r a g e - a p p r o p r i a t e i n s t r u m e n t s i n the assessment o f p a i n i n young c h i l d r e n ( P e t e r s o n e t a l . , 1991) . From the c u r r e n t s t u d y , i t would seem our measur ing i n s t r u m e n t s a d e q u a t e l y c a p t u r e i n f a n t f a c i a l a c t i v i t y . The age v a r i a t i o n i appears p r i m a r i l y i n the magnitude o f r e s p o n s e . However, because o f t h e s e d i f f e r e n c e s i n t h e degree o f r e s p o n s e , c l i n i c i a n s a s s e s s i n g p a i n may b e n e f i t from the use o f a g e - s p e c i f i c norms. 98 The R e l a t i o n s h i p between NFCS and Baby FACS C o d i n g W h i l e b o t h o f the systems o f f a c i a l c o d i n g used i n t h i s s t u d y index c e r t a i n a c t i o n s r e f l e c t i v e o f p a i n , they a r e no t e q u i v a l e n t i n s t r u m e n t s . Baby FACS i s a comprehens ive sys tem, i n t e n d e d t o r e c o r d a l l o f the f a c i a l a c t i o n s i n s t i g a t e d by an e v e n t . NFCS i s l i m i t e d t o a c t i o n s b e a r i n g on the f a c i a l i e x p r e s s i o n o f p a i n . W h i l e NFCS a c t i o n u n i t s may be s i m i l a r t o Baby FACS AUs , the d e f i n i t i o n s a r e no t i d e n t i c a l . F a m i l i a r i t y w i t h b o t h systems o f c o d i n g sugges t s t h a t t h e f o l l o w i n g p a i r s o f a c t i o n s would be the most c l o s e l y r e l a t e d : NFCS Brow Bulge and Baby FACS AU3-Brow K n i t , NFCS Brow Bulge and Baby FACS AU4-Brow Lower, NFCS Eye Squeeze and Baby FACS AU6/AU7-Cheek R a i s e , NFCS Deepened N a s o l a b i a l Furrow and Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n , NFCS Open L i p s and Baby FACS AU26-Jaw D r o p , and NFCS T a u t Tongue and Baby FACS AU75d-Tense , Concave Tongue. The e x a m i n a t i o n o f c o r r e l a t i o n c o e f f i c i e n t s (see T a b l e s 7 and 8 i n the R e s u l t s s e c t i o n ) r e v e a l e d t h a t the s c o r 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 f o r each p a i r . The v a l u e s o f r ranged from 0.49 ( f o r Brow Bulge and AU3) t o 0.76 ( f o r Eye Squeeze and AU6/AU7) . However, i n e v a l u a t i n g t h e numbers, i t i s i m p o r t a n t t o note t h a t s i g n i f i c a n t c o r r e l a t i o n s would be expec ted among a c t i o n u n i t s i n d i c a t i v e o f p a i n , even i f the a c t i o n s were a n a t o m i c a l l y d i s s i m i l a r . F o r example, the c o r r e l a t i o n between NFCS Deepened N a s o l a b i a l Furrow and Baby FACS AU43-Eyes C l o s e d was 0 .40 . Not o n l y a r e the d e f i n i t i o n s o f i n d i v i d u a l a c t i o n u n i t s s l i g h t l y d i f f e r e n t i n NFCS and Baby FACS, they a r e s c o r e d i n a v e r y d i f f e r e n t f a s h i o n . NFCS a c t i o n a r e s c o r e d s o l e l y f o r presence o r absence . Thus each 2 -second segment r e c e i v e s e i t h e r 99 a 0 o r a 1, and s c o r e s f o r the event range from 0 t o 5. In c o n t r a s t , Baby FACS c o d i n g a s s i g n s an i n t e n s i t y s c o r e t o each a c t i o n i n each 2-second segment. T h i s s c o r e may range from 0 t o 5. Thus when Baby FACS s c o r e s a r e summed f o r the e v e n t , they may range from 0 t o 25. F u r t h e r m o r e , i f an i n f a n t were t o d i s p l a y an a c t i o n a t a v e r y low l e v e l t h r o u g h o u t the e n t i r e event ( f o r example, i f the l i p s were j u s t s l i g h t l y p a r t e d ) , the c h i l d would r e c e i v e a 5 out o f 5 i n NFCS, but o n l y a 5 out o f 25 i n Baby FACS. C o n s e q u e n t l y , i t makes sense t h a t the c o r r e l a t i o n between between s i m i l a r a c t i o n s i s l e s s t h a n p e r f e c t . T h i s d i s p a r i t y between the two systems i s l i k e l y r e s p o n s i b l e f o r a n a l y s e s where o n l y one t y p e o f c o d i n g showed a s i g n i f i c a n t d i f f e r e n c e . G i v e n the d i f f e r e n c e s between the two sys tems , i t was g r a t i f y i n g t h a t the p a i n summary s c o r e s c o n s t r u c t e d from each system c o r r e l a t e d h i g h l y ( r = . 7 9 ) . Such a f i n d i n g sugges t s t h a t t h e p a i n e x p r e s s i o n i s r o b u s t enough t o produce s i m i l a r s c o r e s on i n s t r u m e n t s t a k i n g d i f f e r e n t approaches t o measurement. W h i l e t h e p r e s e n t s t u d y was no t e x p l i c i t l y d e s i g n e d t o compare the two a p p r o a c h e s , i t does o f f e r some i n f o r m a t i o n t o i n v e s t i g a t o r s w i s h i n g t o choose a s i n g l e i n s t r u m e n t . W h i l e t h e two systems produce d i f f e r e n t r e s u l t s , t h e r e i s l i t t l e e v i d e n c e t h a t one i s b e t t e r t h a n t h e o t h e r f o r u n c o v e r i n g d i f f e r e n c e s i n t h e p a i n r e s p o n s e . I f a r e s e a r c h e r must l i m i t h e r s e l f t o a s i n g l e i n s t r u m e n t i n d e x i n g the degree o f p a i n e x p r e s s e d , we found l i t t l e r e a s o n t h a t i n v e s t i g a t o r s s h o u l d i n v e s t the t ime n e c e s s a r y f o r more c o m p l i c a t e d Baby FACS c o d i n g . However, the f a c t t h a t each c o d i n g system l e d t o d i f f e r e n t p a t t e r n s o f f i n d i n g s does sugges t t h a t some a d d i t i o n a l i n f o r m a t i o n may be d e r i v e d from the use o f 100 the Baby FACS sys tem, o r from the a d d i t i o n o f an i n t e n s i t y d imen s i on t o NFCS. The p r e s e n t s t u d y was the f i r s t t o use NFCS w i t h i n f a n t s up t o 18 months o f age , w h i l e Baby FACS was d e s i g n e d f o r x x i n f a n t s and young c h i l d r e n . " C o n s e q u e n t l y , we examined the r e s u l t s f o r any i n d i c a t i o n t h a t NFCS i s i n a p p r o p r i a t e f o r o l d e r i n f a n t s . F o r example, f i n d i n g s o f s i g n i f i c a n t age d i f f e r e n c e s i n Baby FACS a c t i o n u n i t s t h a t have no c o u n t e r p a r t i n NFCS would have been cause f o r c o n c e r n . The i n d i v i d u a l a c t i o n s t h a t showed age- r e l a t e d d i f f e r e n c e s i n t h e Baby FACS c o d i n g (AUs 4 and 9/10) are a c t i o n s t h a t have rough e q u i v a l e n t s i n NFCS c o d i n g . There i s no e v i d e n c e t h a t NFCS i s i n a p p r o p r i a t e f o r use w i t h o l d e r i n f a n t s and t o d d l e r s . D i f f e r e n c e s i n the Number o f P a i n S t i m u l i Data c o l l e c t e d f o r t h e p r e s e n t s tudy p r o v i d e d the o p p o r t u n i t y t o l o o k a t d i f f e r e n c e s i n the p a i n e x p r e s s i o n r e s u l t i n g from the number o f s t i m u l i t o which the i n f a n t was s u b j e c t e d . Due t o a change i n the immuniza t ion p r o t o c o l , some i n f a n t s r e c e i v e d two i n j e c t i o n s , the DPT v a c c i n e and the H i b v a c c i n e . O t h e r s r e c e i v e d b o t h v a c c i n e s i n a s i n g l e i n j e c t i o n . The two groups (one i n j e c t i o n v e r s u s two i n j e c t i o n s ) were i compared on s c o r e s f o r i n d i v i d u a l a c t i o n u n i t s i n the p e r i o d 20- 30 seconds f o l l o w i n g t h e l a s t i n v a s i v e s t i m u l u s . I t was found t h a t i n f a n t s who r e c e i v e d two i n j e c t i o n s d i s p l a y e d more t a u t tongue t h a n those who had r e c e i v e d a s i n g l e i n j e c t i o n . However, i n f a n t s who were g i v e n a s i n g l e i n j e c t i o n d i s p l a y e d more brow b u l g e and deepened n a s o l a b i a l f u r r o w than i n f a n t s s u b j e c t e d t o two i n j e c t i o n s . In c o m b i n a t i o n , these f i n d i n g s sugges t t h a t the 101 c u m u l a t i v e e f f e c t o f m u l t i p l e p a i n s t i m u l i i s complex , d e f y i n g a s i m p l e judgment about the r e l a t i v e i n t e n s i t y o f the p a i n e x p e r i e n c e i n the two g r o u p s . The e f f e c t o f m u l t i p l e s t i m u l i d e s e r v e s f u r t h e r s t u d y , as i t i s r e l e v a n t t o the number and f requency o f p a i n f u l m e d i c a l p r o c e d u r e s t h a t s h o u l d be performed on i n f a n t s as p a r t o f o p t i m a l m e d i c a l p r a c t i c e . C o n c l u s i o n s The p r e s e n t s t u d y was c o n s i s t e n t w i t h p r e v i o u s r e s e a r c h i n i d e n t i f y i n g a c o n f i g u r a t i o n o f f a c i a l a c t i o n s a s s o c i a t e d w i t h the p a i n f u l s t i m u l u s o f i m m u n i z a t i o n . The h y p o t h e s i s 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 t h i s response were mediated by the n e g a t i v e e m o t i o n a l i t y d imens ion o f temperament was no t c o n f i r m e d . Developmental changes i n the f a c i a l e x p r e s s i o n o f p a i n were i d e n t i f i e d . D u r i n g the " b a s e l i n e " and " i n j e c t i o n " e v e n t s , 2- month o l d i n f a n t s s c o r e d h i g h e r on p a i n summary s c o r e s than the 4-month o l d i n f a n t s ( a c c o r d i n g t o b o t h c o d i n g systems) and than 6-month o l d i n f a n t s ( a c c o r d i n g t o t h e Baby FACS c o d i n g s y s t e m ) . D u r i n g the "recovery" p e r i o d , 4-month o l d i n f a n t s s c o r e d lower on a p a i n summary s c o r e t h a n d i d 18-month o l d i n f a n t s o r 6-month o l d i n f a n t s ( a c c o r d i n g t o the NFCS c o d i n g s y s t e m ) . A g e - r e l a t e d i changes i n the i n d i v i d u a l a c t i o n u n i t s o f NFCS Brow B u l g e , NFCS Deepened N a s o l a b i a l Furrow, and Baby FACS A U 9 / A U 1 0 - L e v a t o r C o n t r a c t i o n were i d e n t i f i e d . These changes were r o u g h l y c o n s i s t e n t w i t h the changes i d e n t i f i e d i n p a i n summary s c o r e s . Such deve lopmenta l changes may have s i g n i f i c a n c e f o r the i assessment o f p a i n i n i n f a n t s . L i m i t a t i o n s o f the p r e s e n t s t u d y i n c l u d e the i n a b i l i t y t o s e p a r a t e the e x p e r i e n c e o f p a i n from i t s e x p r e s s i o n . T h i s 102 c o n f o u n d i s l i k e l y u n a v o i d a b l e . A s w e l l , o u r e f f o r t n o t t o i n t e r f e r e w i t h t h e r o u t i n e p r a c t i c e s o f t h e n u r s e s a n d p a r e n t s o b s e r v e d m e a n t t h a t t h e r e w a s v a r i a b i l i t y i n t h e p a i n s t i m u l u s a n d t h e c o n d i t i o n s s u r r o u n d i n g t h e i n j e c t i o n . I t w a s f e l t t h a t t h e l a c k o f e x p e r i m e n t a l c o n t r o l w a s w a r r a n t e d b y t h e i n c r e a s e i n e x t e r n a l v a l i d i t y . T h e s t u d y i s a l s o s u b j e c t t o t h e l i m i t a t i o n s o f p a r e n t r e p o r t a s s e s s m e n t s o f t e m p e r a m e n t . F i n a l l y , we d i d n o t a t t e m p t t o s e p a r a t e t h e d i m e n s i o n s o f t h e p a i n r e s p o n s e , s u c h a s l a t e n c y t o t h e p e a k r e a c t i o n , l a t e n c y t o q u i e t , a n d i n t e n s i t y o f f a c i a l a c t i o n s . F u t u r e s t u d i e s may b e n e f i t f r o m u n p a c k i n g t h e s e a s p e c t s a n d c o n s i d e r i n g t h e m s e p a r a t e l y . A n u m b e r o f q u e s t i o n s d e s e r v e f u r t h e r e x a m i n a t i o n . T h e s u r p r i s i n g f a i l u r e t o i d e n t i f y a r o l e f o r t e m p e r a m e n t s u g g e s t s t h a t f u r t h e r r e s e a r c h w i l l b e n e c e s s a r y t o d e l i n e a t e t h e f a c t o r s u n d e r l y 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 t h e e x p r e s s i o n o f p a i n . S u c h r e s e a r c h w o u l d b e n e f i t f r o m t h e a n i n v e s t i g a t i o n o f t h e s t a b i l i t y o f p a i n r e s p o n s e s o v e r t h e f i r s t 2 y e a r s o f l i f e , a s w e l l a s i n v e s t i g a t i o n o f a n u m b e r o f s i t u a t i o n a l c h a r a c t e r i s t i c s . T h e p r e s e n t f i n d i n g s o n a g e - r e l a t e d c h a n g e s i n f a c i a l e x p r e s s i o n s h o u l d b e r e p l i c a t e d a n d i n t e g r a t e d w i t h r e s e a r c h o n o t h e r c o m p o n e n t s o f t h e p a i n r e s p o n s e s u c h a s c r y a n d t h e u s e o f l a n g u a g e , p h y s i o l o g i c a l v a r i a b l e s , a n d t h e m e t a b o l i c s t r e s s r e s p o n s e . 103 REFERENCES Anand, K . J . S . , & C a r r , D . B . (1989) . The neuroanatomy, n e u r o p h y s i o l o g y , and n e u r o c h e m i s t r y o f p a i n , s t r e s s , and a n a l g e s i a i n newborns and c h i l d r e n . 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C h a r a c t e r i z a t i o n o f normal i n f a n t s ' l e v e l - o f - d i s t r e s s by a s i n g l e parameter d e r i v e d from c r y sounds . U n p u b l i s h e d m a n u s c r i p t . Young, M . R . . , & F u , V. .R. (1988) I n f l u e n c e o f p l a y and temperament on the young c h i l d ' s re sponse t o p a i n . C h i l d r e n ' s H e a l t h C a r e . 16 f 209-215. i Z e s k i n d , P . S . , & M a r s h a l l , T . R . (1988) . The r e l a t i o n between v a r i a t i o n s i n p i t c h and m a t e r n a l p e r c e p t i o n s o f i n f a n t c r y i n g . C h i l d Development, 59, 193-196. I l l APPENDIX A Background C h a r a c t e r i s t i c s Q u e s t i o n n a i r e INFANT QUESTIONNAIRE S u b j e c t number: T o d a y ' s d a t e : What i s your b a b y ' s b i r t h da te? , Was your baby premature? I f s o , how many weeks b e f o r e y o u r due date was he o r she born? • What was y o u r b a b y ' s weight a t b i r t h ? Is t h i s baby your f i r s t - b o r n c h i l d ? : I f n o t , how many o l d e r c h i l d r e n do you have? Is your baby g e n e r a l l y h e a l t h y ? I f n o t , what i l l n e s s o r c o n d i t i o n does he o r she have? Is your baby male o r female ? What i s your age? ; How many hours has i t been s i n c e y o u r baby was fed? How many hours has i t been s i n c e your baby woke up? D i d you g i v e your baby T y l e n o l o r another m e d i c a t i o n b e f o r e the shot? ' I f s o , what? T y l e n o l O t h e r : 112 APPENDIX B Sample Items from t h e I n f a n t C h a r a c t e r i s t i c s Q u e s t i o n n a i r e ( B a t e s , 1992) 1. How easy o r d i f f i c u l t i s i t f o r you t o ca lm o r soothe your baby when h e / s h e i s upse t? 1 2 3 4 5 . 6 7 v e r y easy about average d i f f i c u l t i 5. How many t imes p e r d a y , on the a v e r a g e , does your baby ge t f u s s y and i r r i t a b l e - f o r e i t h e r s h o r t o r l o n g p e r i o d s o f t ime? 1 2 3 4 5 6 7 never 1-2 3-4 5-6 7-9 10-14 more t imes t imes t imes t imes t imes than per day p e r day p e r day p e r day p e r day 15 13. When your baby g e t s upse t ( e . g . , b e f o r e f e e d i n g , d u r i n g d i a p e r i n g , e t c . ) , how v i g o r o u s l y o r l o u d l y does h e / s h e c r y and f u s s ? 1 2 3 4 5 6 7 v e r y m i l d moderate v e r y l o u d i n t e n s i t y i n t e n s i t y o r i n t e n s e , o r loudness o r loudness r e a l l y c u t s l o o s e 113 A c t i o n Brow Bulge APPENDIX C NFCS A c t i o n s ( from Grunau & C r a i g , 1990) D e s c r i p t i o n B u l g i n g , c r e a s i n g , and v e r t i c a l furrows above and between brows o c c u r r i n g as a r e s u l t o f the l o w e r i n g and drawing t o g e t h e r o f the eyebrows. Eye Squeeze The s q u e e z i n g o r b u l g i n g o f the e y e l i d s . B u l g i n g o f the f a t t y pads about the i n f a n t ' s eyes a r e pronounced . Deepened N a s o l a b i a l Furrow The p u l l i n g upwards and furrow deepening o f the n a s o l a b i a l furrow (a l i n e o r w r i n k l e t h a t b e g i n s a d j a c e n t t o the n o s t r i l wings and runs down and outward beyond the l i p c o r n e r s ) . Open l i p s Any s e p a r a t i o n o f the l i p s . S t r e t c h Mouth ( V e r t i c a l ) A t a u t n e s s a t t h e l i p c o r n e r s ( v e r t i c a l ) c o u p l e d w i t h a pronounced downward p u l l o f the jaw. O f t e n seen when an a l r e a d y wide open mouth i s opened a f r a c t i o n f u r t h e r by an e x t r a p u l l a t t h e jaw. 114 S t r e t c h mouth ( H o r i z o n t a l ) A d i s t i n c t h o r i z o n t a l p u l l a t the c o r n e r s o f t h e mouth. L i p purse The l i p s appear as i f an "oo" sound i s b e i n g pronounced . T a u t tongue A r a i s e d , cupped tongue w i t h s h a r p t e n s e d edges . The f i r s t o c c u r r e n c e o f t a u t tongue i s u s u a l l y easy t o see , o f t e n o c c u r r i n g w i t h a wide open mouth. A f t e r t h i s f i r s t o c c u r r e n c e , the mouth may c l o s e s l i g h t l y . T a u t tongue i s s t i l l s c o r e a b l e on the b a s i s o f the s t i l l - v i s i b l e tongue edges . C h i n q u i v e r An o b v i o u s h i g h - f r e q u e n c y , up-down mot ion o f the lower jaw. Tongue p r o t r u s i o n Tongue v i s i b l e between the l i p s e x t e n d i n g beyond the mouth. APPENDIX D Baby FACS A c t i o n s ( O s t e r & R o s e n s t e i n , 1993) A . Upper Face A c t i o n s Brow A c t i o n s : AU 1 - Inner Brow R a i s e r AU 2 - O u t e r Brow R a i s e r AU 3 - Brow K n i t t i n g A l o n e AU 4 - Brow K n i t t i n g and Lower ing Cheek and E y e l i d A c t i o n s : AU 5 - Upper L i d R a i s e r AU 6 - Cheek R a i s e r & L i d Compressor AU 7 - L i d T i g h t e n e r AU 40 - Eyes N o r m a l l y Open ( o p t i o n a l ) AU 41 - L i d Droop AU 42 - S l i t AU 43 - Eyes C l o s e d AU 44 - S q u i n t AU 45 - B l i n k AU 46 - Wink AU 49 - T e a r s i n Eyes Head and Eye P o s i t i o n s : AU 47 - L o o k i n g a t a D e s i g n a t e d P e r s o n , O b j e c t o r Event ( o p t i o n a l ) AU 48 - A v e r t i n g the Gaze from a D e s i g n a t e d P e r s o n , O b j e c t , o r Event ( o p t i o n a l ) AU 51 - Head T u r n L e f t AU 52 - Head T u r n R i g h t AU 53 - Head Up AU 54 - Head Down AU 55 - Head T i l t L e f t AU 56 - Head T i l t R i g h t AU 57 - Head Forward AU 58 - Head Back AU 59 - Head Shaking Up and Down AU 60 - Head Shak ing S i d e - t o - S i d e AU 61 - Eyes T u r n L e f t AU 62 - Eyes T u r n R i g h t AU 63 - Eyes Up AU 64 - Eyes Down AU 65 - C r o s s e y e AU 66 - W a l l e y e AU 67 - L o o k i n g E l s e w h e r e , S e a r c h i n g o r L o o k i n g Around ( o p t i o n a l ) AU 84 - Neck S t r e t c h e s Up B . Lower Face A c t i o n s Up-Down A c t i o n s : AU 9 - Nose W r i n k l i n g AU 10 - Upper L i p R a i s i n g AU 15 - Lowered L i p C o r n e r s AU 16 - Lower L i p P u l l e d Down AU 17 - C h i n R a i s i n g AU 25 - L i p s P a r t AU 26 - Jaw Drop AU 27 - Mouth S t r e t c h AU 80 - L i p s R e l a x e d and C l o s e d ( o p t i o n a l ) H o r i z o n t a l A c t i o n s : AU 14 - L i p C o r n e r s P u l l e d Inward: D impler AU 20 - L i p s S t r e t c h e d L a t e r a l l y O b l i q u e A c t i o n s : AU 11 - Upper L i p R a i s e d O b l i q u e l y and F l a t t e n e d AU 12 - L i p C o r n e r s R a i s e d O b l i q u e l y : S m i l i n g \ AU 13 - L i p C o r n e r s P u l l e d S h a r p l y Upward O r b i t a l A c t i o n s : AU 8 - L i p s Toward Each Other (seen w i t h AU 25, 26, o r 27) AU 18 - L i p Pucker AU 22 - L i p F u n n e l e r AU 23 - L i p s T i g h t AU 24 - L i p s P r e s s AU 28 - L i p Suck Tongue P o s i t i o n s and Shapes: AU 19 - Tongue P r o t r u s i o n AU 37 - L i p Wipe AU 73 - Tongue i n C o n t a c t Wi th L i p (not a w i p i n g movement) AU 74 - Tongue P o s i t i o n i n Mouth AU 75 - Tongue Shape C . R e f l e x e s and H i g h l y S t e r e o t y p e d F a c i a l Movements AU 76 - R o o t i n g AU 77 - Yawning AU 78 - O c c i p i t o - F r o n t a l i s R e f l e x AU 79 - S t a r t l e D . M i s c e l l a n e o u s A c t i o n s , P h y s i o l o g i c a l R e a c t i o n s AU 81 - C h i n Trembles AU 82 - Head/Face Trembles o r Shudders AU 84 - L o w - I n t e n s i t y , I n d e f i n i t e Mouth Movements: "Munchies" AU 85 - Sneezes AU 86 - Coughs AU 87 - Swallows AU 88 - Chokes AU 89 - Nose Runs AU 91 - D r o o l s o r S p i t s AU 92 - Throws Up E . O p t i o n a l C o d e s f o r F a c i a l S t i l l i n g a n d f o r S k i p p i n g S e g m e n t s o f a R e c o r d AU 90 - F a c i a l S t i l l i n g ( f a c i a l musc les r e l a x e d , absence f l e e t i n g , l o w - l e v e l f a c i a l a c t i v i t y ) AU 99 - Not Coded ( s k i p p i n g ) APPENDIX E R e s u l t s o f P r e l i m i n a r y A n a l y s e s A s s o c i a t i o n s Between Background C h a r a c t e r i s t i c s and Age Group E f f e c t T e s t s t a t i s t i c p v a l u e C l i n i c X 2 X 2 = 1 4 . 1 6 2 5 6 >.25 Nurse X 2 x 6 = 1 7 . 9 0 4 7 6 >.25 P a r e n t X 2 *=4.56349 >. 25 B i r t h Order X 2 1 6 = 1 8 . 2 2 2 7 1 >.25 Gender X%=3. 41880 >.25 M e d i c a t i o n X%=6.11111 >.15 P r e m a t u r i t y X%=3. 63806 >. 25 Time S i n c e F(4 ,70)=0 .5029 >.50 F e e d i n g 1 Time S i n c e F(4 ,70)=0.9395 >.2;5 Waking J A s s o c i a t i o n s Between Background C h a r a c t e r i s t i c s and Temperament E f f e c t T e s t s t a t i s t i c p v a l u e C l i n i c F(3 ,71)=2.0242 >.10 Nurse F(4 ,70)=1.2714 >.25 Parent F ( l , 7 3 ) = 1 . 6 0 9 6 >.20 B i r t h Order F(4 ,69)=0.2935 >.50 : Gender F ( l , 7 3 ) = 3 . 6 8 0 0 >.05 M e d i c a t i o n F ( l , 7 3 ) = 0 . 2 4 0 5 >.50 P r e m a t u r i t y F ( l , 7 3 ) = 0 . 0 6 8 7 >.50 : Time S i n c e r=- .1468 >.20 F e e d i n g Time S i n c e r=- .1239 >.25 Waking 121 APPENDIX F Frequency o f F a c i a l A c t i o n s NFCS A c t i o n s A c t i o n U n i t P e r c e n t o f Segments i n Which A c t i o n was Observed Brow Bulge 61 Eye Squeeze 36 N a s o l a b i a l Furrow 57 Open l i p s 83 V e r t i c a l Mouth 4 S t r e t c h H o r i z o n t a l Mouth 1 S t r e t c h L i p Purse 0 T a u t Tongue 20 C h i n Q u i v e r 0 Tongue P r o t r u s i o n 2 Baby FACS A c t i o n s A c t i o n U n i t P e r c e n t o f Segments i n Which A c t i o n was Observed AU1-Inner Brow 11 R a i s e AU2-Outer Brow 6 R a i s e AU3-Brow K n i t 53 AU4-Brow Lower 42 AU5-Upper L i d R a i s e 3 122 Frequency o f F a c i a l A c t i o n s ( c o n t . ) A c t i o n U n i t P e r c e n t o f Segments i n Which A c t i o n was Observed A U 6 / A U 7 - 0 r b i t 56 T i g h t e n i n g A U 9 / A U 1 0 - L e v a t o r 58 C o n t r a c t i o n A U 1 2 - L i p C o r n e r s 3 R a i s e d O b l i q u e l y AU14-Dimpler 1 AU15-Lowered L i p 0 C o r n e r s AU16-Lower L i p 2 P u l l e d Down AU17-Chin R a i s e 15 A U 1 8 - L i p Pucker 0 AU19-Tongue 8 P r o t r u s i o n A U 2 0 - L i p s S t r e t c h e d 6 L a t e r a l l y A U 2 2 - L i p F u n n e l e r 0 A U 2 3 - L i p s T i g h t 0 A U 2 4 - L i p P r e s s 0 AU26-Jaw Drop 81 A U 2 8 - L i p Suck 1 AU33-B10W 0 A U 4 1 - L i d Droop 0 A U 4 2 - S l i t 0 123 Frequency o f F a c i a l A c t i o n s ( c o n t ; ) A c t i o n U n i t P e r c e n t o f A c t i o n Segments i n Which was Observed AU43-Eyes C l o s e d 33 | AU44-Squ in t 11 A U 4 5 - B l i n k 9 AU49-Tears i n Eyes 8 AU74b-Tongue Hooked 0 Beh ind T e e t h o r Gums AU74c-Tongue R a i s e d AU75b-Tongue F l a t 0 AU75c-Tongue T i p 0 C u r l e d AU75c2-Tongue 0 Concave and R e l a x e d AU75d-Tongue 16 Concave and Tense AU76-Root ing 0 AU81-Chin Trembles 0 AU82-Head/Face 1 Shudders AU85-Sneezes 0 AU86-Coughs 0 AU89-Nose Runs o A U 9 1 - D r o o l s o r 2 S p i t s 124

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