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UBC Theses and Dissertations

Interpersonal influences on pain expressions Prkachin, Kenneth Martin 1978

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INTERPERSONAL INFLUENCES ON PAIN EXPRESSIONS by KENNETH MARTIN PRKACHIN M.A., U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1976 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES THE DEPARTMENT OF PSYCHOLOGY 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 to t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA June, 1978 ( c ) Kenneth M a r t i n P r k a c h i n , 1978 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 representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Psychology The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 D a t e June 30, 1978. i i ABSTRACT I n c r e a s i n g e v i d e n c e s u g g e s t s t h a t s o c i a l e x p e r i e n c e s c r i t i c a l l y d e t e r m i n e the manner i n w h i c h i n d i v i d u a l s r e s p o n d t o p a i n f u l e v e n t s . Of the v a r i e t y o f s o c i a l d e t e r m i n a n t s o f p a i n r e s p o n s e s , s o c i a l m o d e l i n g has been among the most e x t e n s i v e l y s t u d i e d . C o n c l u s i v e e v i d e n c e i s a v a i l a b l e showing t h a t e x p o s u r e t o models who e x h i b i t t o l e r a n c e o r i n t o l e r a n c e f o r n o x i o u s e l e c t r i c a l s t i m u l a t i o n p r o d u c e s m a t c h i n g b e h a v i o u r on t h e p a r t o f s u b j e c t s . However, q u e s t i o n s r e l a t e d t o t h e b r e a d t h o f the changes i n -duced, and t h e a p p l i c a b i l i t y o f t h e s e f i n d i n g s t o n a t u r a l l y - o c c u r r i n g p a i n f u l e x p e r i e n c e s r e q u i r e f u r t h e r i n v e s t i g a t i o n . The p r e s e n t s e r i e s o f s t u d i e s examined some o f t h e s e i s s u e s . E x p e r i m e n t 1 r e - e v a l u a t e d t h e i m -p a c t o f s o c i a l m o d e l i n g on s e n s o r y - d e c i s i o n t h e o r y (SDT) i n d i c e s o f t h e r e s p o n s e t o p a i n . F o l l o w i n g a b a s e l i n e p r e - a s s e s s m e n t o f p a i n t h r e s h o l d and t o l e r a n c e , 30 female s u b j e c t s were exposed t o models d i s p l a y i n g t o l e r -ance o r i n t o l e r a n c e f o r the s t i m u l a t i o n , o r an i n a c t i v e companion. Under c o n d i t i o n s o f i n f l u e n c e , s u b j e c t s ' b e h a v i o u r a p p r o x i m a t e d t h a t o f t h e model. A f t e r t h e s e e f f e c t s had been i n d u c e d , s u b j e c t s underwent a SDT s e r i e s d u r -i n g w h i c h t h e y were exposed t o s t i m u l i from l o w , moderate, and h i g h l e v e l s o f c u r r e n t i n t e n s i t y . R e s u l t s i n d i c a t e d t h a t i n t o l e r a n t m o d e l i n g was a s s o c i a t e d w i t h i n c r e a s e d s e n s o r y s e n s i t i v i t y a t n o x i o u s l e v e l s o f s t i m u -l a t i o n . T o l e r a n t m o d e l i n g was n o t a s s o c i a t e d w i t h d i f f e r e n t i a l v a l u e s o f s e n s i t i v i t y - , s u g g e s t i n g t h a t p r e v i o u s p o s i t i v e f i n d i n g s be q u a l i f i e d . Ex-p e r i m e n t 2 was c o n c e r n e d w i t h t h e e f f e c t s o f t o l e r a n t and i n t o l e r a n t mod-e l i n g on o v e r t e x p r e s s i v e d i s p l a y s . V i d e o t a p e s t a k e n o f s u b j e c t s i n i i i Experiment 1 were presented to 15 female observers'who attempted to pre^ diet the levels of current that observed subjects were experiencing. SDT analyses of observers' judgments indicated that responses to intense stimuli were more readily discriminated than responses to less intense* stimuli. The behaviour of subjects exposed to a tolerant model was less discriminable than that of intolerant subjects. The behaviour of intol-erants was less discriminable than that of controls. It was argued that tolerant modeling produces reductions in overt^ nonvocal expressions of pain. Experiment 3 examined whether modeling effects could be obtained with naturally-occurring groups, and the relative power of pain tolerant and intolerant behaviour. 127 female undergraduates underwent a screen-ing for pain threshold levels. In a subsequent session, subjects partici-pated either individually, or in pairs comprised of a l l combinations of subjects having high and low thresholds. Unidirectional influence was observed, with low threshold subjects inducing high threshold subjects to report pain sooner, and accept fewer currents. These results indicated that pain intolerant behaviour may be a more powerful social influence than pain tolerant behaviour, probably as a result of its imperative nature. Since the modeling effect was observable among naturally-occurr-ing groups, the generalizability of laboratory to naturally-occurring pain phenomena was supported. Relationships between measures of pain based on psychophysical judgments and overt behaviour were examined within the context of a model that suggests that inducing alterations in pain be-haviour may modulate the experience of pain. i v TABLE OF CONTENTS ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i LIS T OF FIGURES v i i L I S T OF APPENDICES v i i i ACKNOWLEDGEMENTS "ix INTRODUCTION 1 RATIONALE 26 EXPERIMENT 1: SOCIAL MODELING INFLUENCES ON PAIN THRESHOLD, PAIN TOLERANCE, AND SENSORY-DECISION THEORY INDICES 28 I n t r o d u c t i o n 28 Method 33 R e s u l t s 43 D i s c u s s i o n 61 EXPERIMENT 2: A SENSORY-DECISION THEORY ANALYSIS OF SOCIAL MODELING INFLUENCES ON NONVOCAL PAIN EXPRESSIONS 70 I n t r o d u c t i o n 70 Method 74 R e s u l t s 78 D i s c u s s i o n 87 EXPERIMENT 3: AN INVESTIGATION OF VICARIOUS INFLUENCES ON PAIN COMMUNICATIONS EMPLOYING NATURALLY-OCCURRING GROUPS 95 I n t r o d u c t i o n 95 Method 98 R e s u l t s 102 D i s c u s s i o n 110 V GENERAL DISCUSSION 116 REFERENCE NOTES 121 REFERENCES 122 APPENDIX A 130 APPENDIX B 132 APPENCIX C 136 v i L I ST OF TABLES T a b l e 1:1. Mean d i s c r i m i n a b i l i t y i n d i c e s a t s t i m u l u s p a i r s . 3-4 t o 5-6 f o r T o l e r a n t , I n t o l e r a n t and C o n t r o l s u b j e c t s . 56 T a b l e 2:1. Means o f low, medium, and h i g h c u r r e n t i n t e n s i t i e s a d m i n i s t e r e d t o o b s e r v e d s u b j e c t s . 77 T a b l e 2:2. Mean d_' v a l u e s f o r t h e Squads X R e p l i c a t i o n s i n t e r a c t i o n . 81 T a b l e 2:3. Mean d_' v a l u e s f o r the Squads X D i s c r i m i n a t i o n s i n t e r a c t i o n . 83 T a b l e 2:4. Mean d_' v a l u e s f o r the Squads X M o d e l i n g Groups X D i s c r i m i n a t i o n s i n t e r a c t i o n . 84 T a b l e 2:5. Mean d i f f i c u l t y r a t i n g s a s s o c i a t e d w i t h each Squad when o b s e r v e r s made judgements o f s u b j e c t s f rom the t h r e e s o c i a l i n f l u e n c e c o n d i t i o n s o f Study 1. 86 T a b l e 3:1. R e s u l t s o f p l a n n e d o r t h o g o n a l c o mparisons f o r p a i n t h r e s h o l d d a t a . 104 v i i L I ST OF FIGURES F i g u r e 1:1. Mean i n t e n s i t y o f c u r r e n t p r o v o k i n g a r a t i n g o f "10" ( p a i n t h r e s h o l d ) under u n i n f l u e n c e d and i n f l u e n c e d c o n d i t i o n s f o r s u b j e c t s i n Groups T, C, and I . 46 F i g u r e 1:2. Mean i n t e n s i t y o f c u r r e n t p r o v o k i n g a " t e r m i n a t e " r a t i n g under u n i n f l u e n c e d and i n f l u e n c e d c o n d i t i o n s f o r s u b j e c t s i n Groups T, C, and I . 49 F i g u r e 1:3. Mean f r e q u e n c y o f c h o i c e of each r a t i n g s c a l e p o i n t a t h i g h , medium, and low shock i n t e n s i t i e s f o r s u b j e c t s i n Groups T, C, and I . 52 F i g u r e 3:1. Mean i n t e n s i t y o f c u r r e n t p r o v o k i n g a r a t i n g o f "10" ( p a i n t h r e s h o l d ) o v e r a l l shock s e r i e s i n S e s s i o n 1 and S e s s i o n 2 f o r s u b j e c t s i n a l l g r oups. 103 F i g u r e 3:2. Mean i n t e n s i t y o f c u r r e n t a t t h e p o i n t where s u b j e c t s t e r m i n a t e d each s h o c k s e r i e s ( p a i n t o l e r a n c e ) d u r i n g S e s s i o n 2 f o r a l l g r o u p s . 108 v i i i L I ST OF APPENDICES APPENDIX A. P s y c h o m e t r i c d a t a from E x p e r i m e n t 1. 130 APPENDIX B. Consent Forms. 132 APPENDIX C. Q u e s t i o n n a i r e s a d m i n i s t e r e d i n E x p e r i m e n t 1. 136 X X ACKNOWLEDGEMENTS A l a r g e number of p e o p l e have c o n t r i b u t e d s i g n i f i c a n t l y t o t h e development o f t h i s d i s s e r t a t i o n . A l l members of t h e d i s s e r t a t i o n committee have made d i r e c t , s i g n i f i c a n t , and i n d e p e n d e n t c o n t r i b u t i o n s . They a r e : D r s . Kenneth D. C r a i g , P a r k 0. D a v i d s o n , R o b e r t Knox, and Lawrence M. Ward. I owe D r i . Kenneth C r a i g s p e c i a l g r a t i t u d e f o r h i s c o n t i n u o u s s u p p o r t and a s s i s t a n c e t h r o u g h o u t my g r a d u a t e c a r e e r . S p e c i a l t hanks a l s o go t o my good f r i e n d , C i n d y G o s l i n e , f o r h e r a s s i s t a n c e i n a l l a s p e c t s o f t h e p r o j e c t ; i n p a r t i c u l a r f o r c o n d u c t i n g E x p e r i m e n t 2 under sometimes e x t r e m e l y a d v e r s e c i r c u m s t a n c e s . Luz P i e d r a h i t a , D i a n a P i e d r a h i t a and L i z Z i s c h k a s e r v e d as models i n E x p e r i m e n t 1. D a n i M c C u l l o u g h gave g e n e r o u s l y o f h e r t i m e t o a i d i n some of t h e more t e d i o u s and a v e r s i v e c h o r e s . Judy Hawkins, L. N a y l o r , and H. Boudreau t y p e d v a r i o u s p a r t s o f t h e m a n u s c r i p t . My v e r y dear f r i e n d , G e o r g i a Nemetz, came t o my r e s c u e d u r i n g one p a r t i c u l a r p e r i o d of emergency. F i n a l l y , I w o u l d l i k e t o thank G l e n d a M i d g l e y f o r h e r h e l p and encouragement d u r i n g a l l phases of t h i s d i s s e r t a t i o n . INTRODUCTION The c u r r e n t p r o l i f e r a t i o n o f r e s e a r c h i n t o t h e anatomy, n e u r o ^ p h y s i o l o g y , and p s y c h o l o g y o f p a i n has been a t t r i b u t e d , i n p a r t , t o a s h i f t f rom a d i s e a s e - m o d e l o r i e n t a t i o n t h a t c o n s i d e r e d p a i n t o be n o t e -w o r t h y o n l y as a symptom o f u n d e r l y i n g p a t h o l o g y , t o a p e r s p e c t i v e v i e w -i n g p a i n as a phenomenon w o r t h y o f s t u d y i n i t s own r i g h t , i n d e p e n d e n t o f , o r i n r e l a t i o n t o , p a t h o l o g i c a l p r o c e s s e s ( F o r d y c e , 1976b). C o u p l e d w i t h t h i s change i n p e r s p e c t i v e and e x p a n s i o n o f r e s e a r c h has been an i n c r e a s e d a p p r e c i a t i o n o f t h e c o m p l e x i t y o f t h e e x p e r i e n c e . To a l a r g e e x t e n t , such a p p r e c i a t i o n has d e r i v e d f r o m m o d u l a t i o n s t u d i e s w h i c h have demon-s t r a t e d t h a t r e s p o n s e s t o p a i n f u l e v e n t s can be i n f l u e n c e d by a w i d e v a r i e t y o f c h e m i c a l , s u r g i c a l , and e n v i r o n m e n t a l m a n i p u l a t i o n s . A l t h o u g h s e v e r a l t h e o r i e s a t t e m p t t o i n t e g r a t e t h e p r o c e s s e s t h r o u g h w h i c h modu-l a t i o n o c c u r s (Chapman, 1977; M e l z a c k & W a l l , 1965; M e l z a c k , 1973; Mayer, 1 9 7 4 ) , t h e v a r i a b l e s t h a t a r e c a p a b l e o f m o d u l a t i n g r e s p o n s e s t o p a i n a r e so d i v e r s e t h a t no c u r r e n t f o r m u l a t i o n seems e n t i r e l y s a t i s -f a c t o r y . The r e s e a r c h t o be r e p o r t e d h e r e i n d e a l t w i t h t h e e f f e c t s o f s o c i a l e n v i r o n m e n t m a n i p u l a t i o n s on human p a i n r e s p o n s e s . I n p a r t , t h i s r e s e a r c h r e p r e s e n t e d an a t t e m p t t o examine the b r e a d t h o f t h e changes i n d u c e d a c r o s s a v a r i e t y o f i n d i c e s o f r e s p o n s e t o n o x i o u s s t i m u l a t i o n . A f u r t h e r aim was t o c o l l e c t d a t a p e r t i n e n t t o s o c i o ^ b e h a v i o u r a l a c c o u n t s o f t h e o r i -g i 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 r e s p o n s e t o p a i n f u l e v e n t s . I n t h e f o l l o w i n g s e c t i o n , c u r r e n t f o r m u l a t i o n s o f p a i n w i l l be r e v i e w e d b r i e f l y . S u b s e q u e n t l y , a more d e t a i l e d e x p l i c a t i o n o f t h e r r o l e o f s o c i a l e v e n t s i n d e t e r m i n i n g r e s p o n s e s t o p a i n w i l l be o u t l i n e d . F i n a l l y , a t t e n t i o n w i l l be p a i d t o m e t h o d o l o g i c a l i s s u e s r e l e v a n t t o t h e studies to be reported in the sequel, 2 Pain Perspectives; Ah overview Traditional perspectives have characteristically employed a stimulus-response formulation in accounting for pain (Fordyce, 1976b). The basic model is as follows. Adequate stimulation activates peri-pheral nociceptors which convey nociceptive information centrally to lower and higher brain centers. Activity in these centers determines the perception of pain and the behavioural response to noxious stimu-lation. Research deriving from this perspective has focussed on the bio-physical characteristics of relevant peripheral structures, the anatomy and physiology of ascending sensory systems, the localization of pain-relevant structures in the brain, and the psychophysical characteristics and capacities of the molar system. This traditional perspective, most closely associated with the specificity theory of von Frey (reviewed in Melzack & Wall, 1970), has had major consequences for pain research such as the identification of peripheral and central structures and systems that are critically involved iii pain processes. Equally important, however, have been advances brought about through recognition of the empirical inadequacies of this position. As Melzack (1973) and others have pointed out, the traditional perspective fails to account for a variety of puzzling phenomena, such as phantom-limb pain, the unpredictable effects of surgical lesions of pain^-relevant neural pathways and structures, and the not infrequent observation of lack of correspondence between the occurrence of noxious events and evidence of pain. Further, i t has l i t t l e to say about central or 3 experiential factors involved in pain modulation. Since modulation of pain responses* can be brought about through a variety of physiological and psychological procedures (cv. Bonica & Albe-Fessard, 1976; Weisenberg, 1977), a complete account of pain must adequately deal with both sources of such modulation, employing principles appropriate to each. Currently, the most comprehensive and integrated formulation of pain processes derives from anatomical, biochemical, and neurophysiological work. Gate-Control Theory (GCT) (Melzack & Wall, 1965; Melzack, 1973) has been a critical impetus to the expansion of pain research (Liebeskind & Paul, 1977), and represents an attempt to account more fully for the paradoxes facing earlier formulations. As such i t involves an increase in complexity and a departure from the strict stimulus-response nature of earlier formulations. GCT rests upon a description of current know-ledge of the anatomical substrate of pain-related behaviour; however, its fundamentally novel contribution lies in its application of the principle of inhibitory control of sensory input. According to this position, pro-cesses producing modulation of nociceptive input can be activated either presynaptically, prior to the central evocation of pain perception, or via descending inhibitory activity resulting from the action of central regulatory mechanisms, Pain modulation is presumed to occur via activa-tion of a gating mechanism, the anatomical locus of which is to be found in the spinal cord substantia gelatinosa, In addition to the hypothetical spinal gating mechanism, GCT proposes that different ascending spinal tracts mediate different aspects of pain perception: a neospinothalamic tract-thalamus-somatosensory-cortex system subserving sensory-discriminative 4 a s p e c t s o f p a i n , and a paramedian, a s c e n d i n g s y s t e m ^ t h a l a m u s - l i m b i c s y s t e m p a t h s u b s e r v i n g a f f e c t i v e ^ p i o t i v a t i o n a l a s p e c t s , ( R e c e n t l y Dennis 1 and M e l z a c k ( 1 9 7 8 ) have r e v i e w e d . e v i d e n c e f o r a t l e a s t t h r e e . a s c e n d i n g p a i n - s i g n a l l i n g s y s t e m s . ) The GCT n o t i o n o f d e s c e n d i n g i n - ^ h i b i t o r y c o n t r o l has been r o b u s t and r e c e n t a c c o u n t s o f t h e mode o f a c t i o n o f v a r i o u s a n t i n o c i c e p t i v e p r o c e d u r e s s u c h as morphine a n a l g e s i a , s t i m u -l a t i o n - p r o d u c e d a n a l g e s i a , and a c u p u n c t u r e have r e l i e d h e a v i l y upon i t (Mayer & P r i c e , 1976; Mayer, P r i c e , R ' a f f i '&•; B'arher.L, 1 9 7 6 ) . F u r t h e r , s i n c e the p a i n systems i m p l i c a t e d i n GCT a l l p r o j e c t t o and r e c e i v e p r o j e c t i o n s f r o m h i g h e r b r a i n c e n t e r s , i t has been ar g u e d t h a t t h e s e s ystems may med-i a t e t h e p a i n - m o d u l a t o r y e f f e c t s o f v a r i o u s e x p e r i e n t i a l and " c o g n i t i v e " i n f l u e n c e s . H a l l ( 1 9 7 7 ) , f o r example, has argued t h a t h y p n o t i c o r w a k i n g , i m a g i n e d a n a l g e s i a i s p r o d u c e d t h r o u g h an i n h i b i t i o n o f a c t i v i t y a t t h e s p i n a l g a t i n g mechanism. The d e m o n s t r a t i o n t h a t e x p e r i e n t i a l v a r i a b l e s a r e c a p a b l e o f a f f e c t i n g p a i n r e s p o n s e s may be c o n s i s t e n t w i t h GCT. How-e v e r , s u c h d e m o n s t r a t i o n s do n o t r e p r e s e n t c o n f i r m a t o r y e v i d e n c e , n o r does t h e e x i s t e n c e o f a mechanism f o r c e n t r a l r e g u l a t i o n o f n o x i o u s i n p u t imply" 1, t h a t t h i s i s t h e sys t e m t h r o u g h w h i c h such i n f l u e n c e s e x e r t t h e i r e f f e c t . C o n c u r r e n t w i t h r e c e n t advances i n the u n d e r s t a n d i n g o f t h e anatom-i c a l , b i o c h e m i c a l , and n e u r o p h y s i o l o g i c a l f a c t o r s s u b s e r v i n g p a i n has been an i n c r e a s e i n a t t e n t i o n d i r e c t e d toward t h e r o l e p l a y e d by p s y c h o s o c i a l v a r i a b l e s i n t h e m o d u l a t i o n o f p a i n r e s p o n s e s . I t has l o n g been a c c e p t e d t h a t f a c t o r s i n v o l v e d i n an or g a n i s m ' s b e h a v i o u r a l h i s t o r y and c u r r e n t s o c i a l c o n d i t i o n s may i n f l u e n c e r e s p o n s e s t o n o x i o u s s t i m u l a t i o n o r t h e e m i s s i o n o f b e h a v i o u r i n d i c a t i v e o f p a i n . E v i d e n c e f o r t h i s p o i n t has come fro m many s o u r c e s , i n c l u d i n g c a s u a l and c l i n i c a l o b s e r v a t i o n , and a m u l t i t u d e 5 o f s y s t e m a t i c s t u d i e s o f s u c h d i v e r s e v a r i a b l e s as p e r s o n a l i t y t r a i t s , c o g n i t i v e s t y l e s , c o g n i t i v e s t r a t e g i e s , a f f e c t i v e s t a t e s , p r e p a r a t o r y i n " f o r m a t i o n , h y p n o s i s , and so on (see W e i s e n b e r g , 1977, f o r a r e v i e w ) . W h i l e t h e r e i s l i t t l e d i s a g r e e m e n t r e g a r d i n g t h e s u b s t a n c e o f t h i s r e s e a r c h , t h e r e i s e q u a l l y l i t t l e agreement w i t h r e g a r d t o t h e a c t i v e mechanisms i n v o l v e d , t h e i r l o c u s o f o p e r a t i o n , and t h e g e n e r a l i t y o f t h e f i n d i n g s . A d d i t i o n a l l y , t h e v e r y d i v e r s i t y o f t h e s e f a c t o r s d e f i e s t h e development o f a c o h e r e n t , s y s t e m a t i c t h e o r e t i c a l framework w i t h i n w h i c h t h e i r modes o f a c t i o n w o u l d be a d e q u a t e l y a c c o u n t e d f o r . S i n c e t h e r e s e a r c h t o be r e p o r t e d h e r e i n d e a l t w i t h t h e r o l e o f s o c i o - e n v i r o n m e n t a l v a r i a b l e s i n p a i n m o d u l a t i o n , i t w i l l be n e c e s s a r y t o d i s c u s s c u r r e n t u n d e r s t a n d i n g o f how such f a c t o r s a r e r e l e v a n t t o p a i n m o d u l a t i o n p r o c e s s e s . P a i n i s o r d i n a r i l y d e s c r i b e d as a p r i v a t e , s u b j e c t i v e e x p e r i e n c e . S c i e n t i f i c d i s c u s s i o n s o f the t o p i c t y p i c a l l y d e a l w i t h s e n s o r y mechanisms. I n r e c e n t y e a r s , however, i t has become i n c r e a s i n g l y a p p a r e n t t h a t a p r o -d u c t i v e approach t o the s t u d y o f p a i n - r e l a t e d p r o c e s s e s l i e s i n i n v e s t i -g a t i o n o f t h e i r b e h a v i o u r a l a s p e c t s . P a i n f u l e v e n t s have b e h a v i o u r a l c onsequences; i n f a c t , p a i n i s i n v a r i a b l y i n f e r r e d from b e h a v i o u r a l ob-s e r v a t i o n . S t e r n b a c h (1968, p.8) n o t e s : "... i t i s n e c e s s a r y f o r t h e p e r -son t o do s o m e t h i n g ... i n o r d e r f o r us t o d e t e r m i n e t h a t he i s e x p e r i e n c -i n g p a i n . " S i m i l a r l y , F o r d y c e (1976, p.153) has s t a t e d : C l i n i c a l l y , p a i n cannot become a p r o b l e m u n t i l someone communicates t h a t p a i n i s b e i n g e x p e r i e n c e d . The p a t i e n t g r i m a c e s o r moans, t a l k s about t h e q u a l i t y and l o c a t i o n o f t h e p a i n , l i m p s o r o t h e r w i s e moves i n a guarded manner, o r d i s p l a y s a u t o n o m i c a l l y m e d i a t e d i n d i c a t i o n s o f d i s t r e s s . O t h e r a u t h o r s have made s i m i l a r p o i n t s ( C r a i g , N o t e 1; S z a s z , 1968; 6 Zborowski, 1969) . Virtually a l l studies of pain in intact organisms employ behav^ iourally-based dependent measures-''-although some make use of concurrently^ recorded physiological responses as well (Craig-frrPrkachin, 1978). Since pain is a phenomenon that is intimately tied to behavioural express-ion, three related consequences follow. First, pain expressions are cap-able of exerting an influence upon the social environment in which they occur. Thus, pain expressions are likely to provoke characteristic changes in the behaviour of members of the social milieu (Craig, 1978b). The nature of the changes that occur will be dependent upon a variety of factors including the situational context in which they occur, behavioural characteristics of those present when they occur, and parametric character-istics of the displays themselves, including their intensity, frequency, and chronicity. Second, social consequences are likely to exert recipro-cal influence, provoking immediate and long term effects on the expressions themselves.. Third, expressions of pain are likely to be subject to modu-lation via other social processes effective in controlling behaviour. Social events, pain experience, and behaviour There are two major areas of interst when considering interrelation-ships between social events and pain expressions, The first concerns characteristic effects of pain expressions on the behaviour of other. The second deals with the question of what influence these events have upon current and subsequent pain experience and expression. Effects on the behaviour of others. It is a common observation that expressions of pain and suffering have a powerful impact on the 7 b e h a v i o u r o f o t h e r s . Episodes,, of acute p a i n provoke r a p i d and s a l i e n t s e q u e l a e i n t h e b e h a v i o u r o f o t h e r s : e x p r e s s i o n s o f sympathy, c o m f o r t i n g , d i f f u s e " e m o t i o n a l " r e s p o n s e s , and i n t e r v e n t i o n s t h a t a l l e v i a t e t h e s o u r c e o f d i s t r e s s , t o l i s t b u t a few. The power t h a t s u c h e x p r e s s i o n s have o v e r o t h e r s even d u r i n g p e r i o d s o f p r o t r a c t e d p a i n and among c a r e t a k e r s who have e x t e n d e d e x p e r i e n c e o f e x p o s u r e t o p a i n d i s p l a y s i s i l l u s t r a t e d by c l i n i c a l o b s e r v a t i o n s o f p a t i e n t - s t a f f i n t e r a c t i o n s on a b u r n - p a i n u n i t : S t a f f members a r e c o n s t a n t l y s a y i n g t o the p a t i e n t , " I t w i l l be o v e r s o o n . " " J u s t a b i t l o n g e r . " P a t i e n t s a r e c o n s t a n t l y c r y i n g out " F o r God's s a k e , h u r r y ."' (Fagerhaugh, 1974, p . 6 4 6 ) , When a p a i n p r o b l e m becomes c h r o n i c , t h e c o r r e s p o n d i n g i n c r e a s e i n t h e d u r a t i o n o f e x p o s u r e o f members o f t h e immediate s o c i a l m i l i e u i s l i k e l y t o p r o d u c e permanent a d j u s t m e n t s i n t h e i r b e h a v i o u r ( F o r d y c e , 1976b; S t e r n b a c h , 1974). U n f o r t u n a t e l y , the c u r r e n t s t a t e o f knowledge does n o t a l l o w an adequate amount o f p r e c i s i o n i n p r e d i c t i n g t h e s e changes. E a r l y l a b o r a t o r y r e s e a r c h i n v o l v i n g v i c a r i o u s e x p o s u r e o f s u b j e c t s t o the s u f f e r i n g o f o t h e r s d e m o n s t r a t e d t h e p r o v o c a t i v e a u t o n o m i c / e m o t i o n a l consequences o f p a i n d i s p l a y s ( B e r g e r , 1962; C r a i g & Lowery, 1968). Such i n v e s t i g a t i o n s n e g l e c t e d t h e o v e r t accompaniments o f a u t o n o m i c a l l y -m e d i a t e d e v e n t s t h a t a r e n e c e s s a r i l y c r i t i c a l i n t h e s o c i a l i n f l u e n c e p r o -c e s s . However, l a t e r r e s e a r c h has s u g g e s t e d t h a t t h e o c c u r r e n c e o f s u c h r e s p o n s e s i s p r e d i c t i v e o f o v e r t a t t e m p t s a t r e l i e f and c o m f o r t ( B l e d a , 1975; K r e b s , 1975). S o c i a l e v e n t s i m p l i c a t e d i n p a i n m o d u l a t i o n . S i n c e p a i n b e h a v i o u r s a r e p u b l i c l y o b s e r v a b l e and o c c u r i n a s o c i a l c o n t e x t t h e r e i s e v e r y r e a s o n t o b e l i e v e t h a t t h e y a r e s u s c e p t i b l e t o m o d i f i c a t i o n and m a i n t e n a n c e by any 8 of a host of variables shown to be pertinent to the modification and maintenance of other forms of behaviour. W h i l e this is clearly an area of great research potential, few large-scale, systematic studies have been attempted and, therefore, evidence bearing on the issue is largely the result of clinical observation. F o r d y c e (1976b) has provided a detailed analysis of historical and current environmental factors that predispose an individual toward the emission of high rates of pain behaviour, F i r s t of all, pain behaviour may, historically or currently, have been consequated by direct positive reinforcement in several forms, social attention, protection, and re-assurance from significant others, compensation, or iatrogenic reinforce-ment represent a few examples). P a r t i c u l a r l y interesting is the potential for mutual reinforcement in dyadic interaction. The person exhibiting pain may be reinforced for so doing by the behaviour of the other. R e c i p -rocally, the act of reinforcing pain behaviour may be Reinforced by re-ductions in the pain displays of the individual whose pain behaviour was re-inforced. S e c o n d l y , pain behaviour may acquire strength through processes of avoidance learning. F o r example, pain behaviour emitted in the context of personally aversive social situations may be successful in terminating or avoiding them. T h i r d l y , an elaborate repetoire of pain behaviours may occur among individuals lacking a history of sufficient reinforcement for "well behaviour^ '0 The numerous case examples and single-subject experiments reported by F o r d y c e and his co-workers provide ample illustrations of the modicication of pain behaviour occurring as the result of alterations in the response of the social environment to pain displays ( F o r d y c e , 1976a, 1976b; F o r d y c e , 9 F o w l e r , Lehmann, D e L a t e u r , Sand, & Tr i e s c h m a n n , 1973; F o r d y c e , F o w l e r , & D e L a t e u r , 1968). There a r e a l t e r n a t i v e s o u r c e s o f i n f o r m a t i o n s u g g e s t i n g t h a t t h e r e s p o n s e to p a i n i s l a r g e l y and s e n s i t i v e l y m odulated by s o c i a l e x p e r i e n c e s . S t u d i e s o f t h e r e s p o n s e o f v a r i o u s e t h n i c groups t o d i s e a s e - s t a t e s o r ex-p e r i m e n t a l p a i n a r e c o n s i s t e n t w i t h t h e c o n c l u s i o n t h a t members o f some c u l t u r e s e x h i b i t c h a r a c t e r i s t i c and s t e r e o t y p e d p a i n b e h a v i o u r t h a t i s d i f f e r e n t i a b l e from the r e s p o n s e o f o t h e r g r o u p s . S e v e r a l i n v e s t i g a t o r s ( S t e r n b a c h & T u r s k y , 1965; T u r s k y & S t e r n b a c h , 1967; We i s e n b e r g , 1975) have d e m o n s t r a t e d s o c i a l and e t h n i c d i f f e r e n c e s i n r e s p o n s e t o e x p e r i m e n t -a l l y i n d u c e d p a i n among v a r y i n g e t h n i c and s o c i a l g r oups. F u r t h e r , e t h n i c a l l y - d e f i n e d groups have been shown t o e x h i b i t c h a r a c t e r i s t i c changes i n p a i n b e h a v i o u r i n r e s p o n s e to t h e m a n i p u l a t i o n o f s o c i a l b a r i a b l e s d e s i g n e d t o p r o v o k e i n t e r g r o u p c o m p e t i t i v e n e s s (Lambert, Libman, & P o s e r , 1960). S u b j e c t s from J e w i s h and P r o t e s t a n t backgrounds who d i d n o t d i f f e r i n a p r e t e s t o f p a i n t o l e r a n c e , were t o l d t h a t t h e i r p a r t i c u l a r e t h n i c group c o u l d n o t t o l e r a t e p a i n as w e l l as t h e o t h e r g roups. J e w i s h s u b j e c t s exposed t o t h i s m a n i p u l a t i o n e x h i b i t e d a s u b j e q u e n t i n c r e a s e i n p a i n t o l e r a n c e w h i c h P r o t e s t a n t s d i d n o t . As C r a i g , ( 1 9 7 8 b ) has p o i n t e d o u t , t h e e x i s t e n c e o f s i m i l a r i t i e s i n the r e s p o n s e o f members o f a p a r t i c u l a r c u l t u r a l group t o p a i n f u l e v e n t s r e p r e s e n t s p r e s u m p t i v e e v i d e n c e f o r t h e o p e r a t i o n o f s o c i a l i z a t i o n e x p e r -i e n c e s i n d e t e r m i n i n g p a i n b e h a v i o u r . R e l e v a n t e x p e r i e n c e s a r e l i k e l y t o i n c l u d e e x p o s u r e t o group members d i s p l a y i n g c u l t u r a l l y - a c c e p t a b l e r e s -ponses i n c i r c u m s t a n c e s o f p a i n and d i s t r e s s . T h i s o b s e r v a t i o n i m p l i c a t e s a n o t h e r s o u r c e o f e n v i r o n m e n t a l i n f l u e n c e — s o c i a l m o d e l i n g — i n t h e 10 a c q u i s i t i o n o f s t y l e s o f response tQ pain. The u b i q u i t y and i m p o r t a n c e o f v i c a r i o u s e x p e r i e n c e i n t h e acquiT-s i t i o n o f complex r e p e r t o i r e s o f b e h a v i o u r have been c o m p r e h e n s i v e l y d o c u -mented o v e r t h e y e a r s by Bandura (Bandura & W a l t e r s , 1963; B a n d u r a , 1969, 1971, 1 9 7 6 ) , who n o t e s t h a t "... ' v i r t u a l l y a l l l e a r n i n g phenomena r e -s u l t i n g f r o m d i r e c t e x p e r i e n c e s can o c c u r on a v i c a r i o u s b a s i s t h r o u g h ob-s e r v a t i o n o f o t h e r p e r s o n s ' b e h a v i o u r and i t s consequences f o r them" (Bandura, 1969, p.118). M o d e l i n g p r o c e s s e s a r e i m p l i c a t e d n o t o n l y i n t h e a c q u i s i t i o n o f new forms of b e h a v i o u r v i a o b s e r v a t i o n a l l e a r n i n g , b u t a l s o i n the a l t e r a t i o n o f p r o b a b i l i t i e s o f o c c u r r e n c e o f p a t t e r n s o f b e h a v i o u r a l r e a d y i n the i n d i v i d u a l ' s r e p e r t o i r e . Of p a r t i c u l a r i n t e r e s t i n t h e p r e s e n t c o n t e x t i s t h e e f f i c a c y o f v i c a r i o u s e x p o s u r e i n the r e d u c t i o n o f a v o i d a n c e b e h a v i o u r s . R e s e a r c h a p p l y i n g m o d e l i n g p r o c e d u r e s t o s u b j e c t s e x h i b i t i n g p h o b i c a v o i d a n c e has d e m o n s t r a t e d t h a t modeled d i s p l a y s o f p r o g r e s s i v e l y more i n t e n s e i n t e r a c t i o n w i t h and approach t o p h o b i c o b j e c t s produce r e d u c t i o n s i n a v o i d a n c e behav-i o u r comparable t o o r g r e a t e r t h a n t h o s e o b s e r v e d as a consequence o f s y s t e m a t i c d e s e n s i t i z a t i o n (Rachman, 1972; Bandura, B l a n c h a r d , & R i t t e r , 1 969). The i m p l i c a t i o n s o f s u c h s t u d i e s f o r p a i n r e s e a r c h a r e c l e a r , s i n c e a v o i d a n c e c o m p r i s e s much o f what i s c h a r a c t e r i z e d as p a i n b e h a v i o u r . S i m i -l a r l y , t o t h e e x t e n t t h a t a v o i d a n c e b e h a v i o u r can be r e d u c e d v i a m o d e l i n g p r o c e d u r e s , i t may a l s o be enhanced by modeled d i s p l a y s o f a v o i d a n c e . R e s e a r c h on s o c i a l i n f l u e n c e v i a m o d e l i n g p r o c e d u r e s has had i m -p o r t a n t consequences i n t h r e e n o t u n r e l a t e d r e s p e c t s . F i r s t , s u c h r e s e a r c h has u n c o v e r e d a major s o u r c e o f v a r i a t i o n i n s o c i a l b e h a v i o u r . Second, m o d e l i n g r e s e a r c h has l e d d i r e c t l y t o t h e development o f p r o c e d u r e s 11 e f f e c t i v e i n a l t e r i n g p r o b l e m a t i c behaviours. ., p a r t i c u l a r l y t h o s e c h a r a -c t e r i z e d by' a v o i d a n c e , T h i r d , p r i n c i p l e s d e r i v e d f r o m m o d e l i n g s t u d i e s have been employed i n t h e o r e t i c a l a c c o u n t s o f t h e o r i g i n s o f v a r i o u s forms o f s o c i a l / e m o t i o n a l b e h a v i o u r . As one example o f t h e l a t t e r , t h e a c q u i s i - t i o n o f f e a r f u l a v o i d a n c e i n the n a t u r a l environment has been a t t r i b u t e d t o t h e m o d e l i n g o f f e a r f u l b e h a v i o u r o b s e r v e d i n the c o n t e x t o f c e r t a i n s t i m u l u s cues ' (Rachman, 1972; Bandura, 1969, 1976). More germane t o t h e p r e s e n t d i s c u s s i o n , F o r d y c e ( 1 9 7 6 a ) , C r a i g (.197.8b)- ., and o t h e r s have argued t h a t m o d e l i n g e f f e c t s a r e d i r e c t and s i g n i f i c a n t d e t e r m i n a n t s o f r e s p o n s e s t o p a i n . I n p a r t i c u l a r , r e l a t i v e t o l e r a n c e o r i n t o l e r a n c e o f n o x i o u s s t i m u l a t i o n may l a r g e l y be t h e p r o d u c t o f e x p o s u r e t o o t h e r s d i s -p l a y i n g r e l a t i v e t o l e r a n c e o r i n t o l e r a n c e o f s i m i l a r s t i m u l a t i o n . S t y l i s -t i c d i f f e r e n c e s i n t h e p a r t i c u l a r forms o f p a i n b e h a v i o u r e m i t t e d i n such c o n t e x t s a l s o a r e l i k e l y t o be m e d i a t e d by m o d e l i n g p r o c e s s e s . E v i d e n c e t h a t m o d e l i n g p r o c e s s e s a r e o p e r a t i v e i n t h e m o d u l a t i o n o f p a i n e x p r e s s i o n s i n n a t u r a l s e t t i n g s comes f r o m a v a r i e t y o f s o u r c e s . I t has been n o t e d c l i n i c a l l y ( F o r d y c e , 1976b), and i n an uncon-t r o l l e d q u e s t i o n n a i r e s t u d y ( G e n t r y , Schows, & Thomas, 1974) t h a t a d i s -p r o p o r t i o n a t e p e r c e n t a g e o f c h r o n i c low back p a i n p a t i e n t s r e p o r t the p r e s e n c e , i n t h e i r immediate f a m i l i e s , o f r e l a t i v e s who s u f f e r e d from low back p a i n or o t h e r p h y s i c a l d i s a b i l i t i e s , and who c o n c e i v a b l y c o u l d have s e r v e d as models f o r p a i n b e h a v i o u r . Fagerhaugh (1974) i n d i s c u s s i n g t h e management o f p a i n e x p r e s s i o n on a b u r n - p a i n u n i t n o t e s : The p a t i e n t s on a b u r n u n i t r e p r e s e n t a group who a r e i n v a r i o u s s t a g e s o f the b u r n and p a i n t r a j e c t o r i e s . These c o n d i t i o n s g i v e e v e r y p a t i e n t a chance t o r e h e a r s e and i n -t e r p r e t h i s own i l l n e s s and i t s p a i n t r a j e c t o r y and t o com-p a r e h i s s t a t e t o t h a t o f o t h e r s . Through t h e s e a c t i v i t i e s 12 he learns the norms and limits of pain expression and re-lie f associated w;ith various phases of the Illness; the probable duration .of the various phases; the various methods of tolerating pain; and.the complications that may alter his pain trajectory, (p.647) Several studies of children with abdominal pain provide further naturalistic evidence interpretable in terms of modeling effects. Apley and Naish (1958) contrasted 100 children exhibiting recurrent abdominal pains with comparable children not experiencing pain. The incidence of similar complaints among members of symptomatic children's immediate families was approximately six times greater than the incidence among control children. Oster (1972), in a questionnaire study, contrasted the family pain histories of children suffering frpmrabdominal, headache, and limb pains with those of children without pain. Twenty-four percent of parents of children with pain reported pain problems in childhood or at the time of investigation in con-trast with 14% among parents of children without pain. The conclusions reached in both of these studies were similar: recurrent pain problems in children may often represent a characteristic familial reaction mediated through imitative processes. Direct evidence that modeling processes are active sources of pain modulation comes from laboratory studies. Craig and Weiss (1971) exposed undergraduate volunteers to six series of electric shocks gradually in-creasing in intensity. Subjects rated each shock on a categorical judg-ment scale ranging from "undetectable" to "painful". A confederate peer model who was ostensibly another subject undergoing the same procedure either dissimulated greater or lesser tolerance than the actual subject by making lower.or higher ratings, or made ratings that were not contingent upon those of the subject. Subjects' behaviour matched that of the models 13 in the active modeling conditions? W/i,th thos.e subjected to a tolerant model accepting substantially greater current intensities before reporting pain than those exposed to an intolerant model. Subjects exposed to the noncontingent co-participant accepted intermediate levels. The robustness of this phenomenon was demonstrated in later studies that employed a differ-ent methodology (Craig & Weiss, 1972; Craig, Best, & Reith, 1974). A stan-dard current intensity, invariably described as non-noxious by uninfluenced subjects, was rated ,ay volunteers over a series of trials. Subjects ex-posed to an intolerant model rated the current as painful 77% of the time while control subjects only did so 3% of the time. Pain modulating effects of modeling were also demonstrated by Neufeld and Davidson (1971) , who employed radiant-heat stimulation for pain induction. Subjects who observed another person experiencing the stimulation without distress showed an amount of pain reduction equal to that induced when subjects listened to detailed descriptions of the heat-induction process. Chaves and Barber (1974), employing pressure-induced pain, reported that observing an experimenter modeling "cognitive control" strategies resulted in reductions in pain reports among subjects who had high pretest pain thresholds. Conceptual and Methodological Issues The evidence reviewed demonstrates that modeling procedures have an impressive impact on verbal pain expressions and suggests that such processes may be active determinants of pain behaviour in natural settings, It is relatively easy to produce changes in pain expressions through manipulation of 14 social conditions, However, simple demonstrations of such effects have raised more complex issues pertaining not only to the parameters governing them, but also to alternative and concurrent processes through which the effects may be mediated. Of particular concern in recent pain research, have been two issues: how dependent are pain modulation effects upon where the investigator chooses to look for them (i.e., how general are the effects across a variety of dependent measures), and are the effects superficial or fundamental (i.e., do the effects merely represent examples of the plasticity of be-haviour, or are they mediated by changes in basic perceptual systems?) These questions are of particular significance because the wide variety of procedures that can effectively yield alterations in indices of pain may govern changes in different indices or may yield their effects via differ-ent mechanisms. Owing to the presence of a comprehensive and perhaps paradigmatic formulation of pain processes •— Gate Control Theory — i t has become re-latively common to relate observed phenomena of pain modulation to its concepts, or to imply that they are accounted for in its terms, thus halting inquiry much in the manner of Skinner's concept of the "explanatory fiction" (Skinner, 1974). However, as Liebeskirid andPaul (1977) point out in their review of measurement issues in physiological studies of pain modulation in animals, studies often pay insufficient attention to the fact that the different pain indices measured are organized in different ways and at differ-ent levels in the nervous system. Treatments failing to affect spinal reflex manifestations of pain, for example, may affect pain measured by vocalization. The point is equally pertinent to studies of environmental or 15 psychological variables, Different indices, may exhibit differential re-activity to different treatments;. A, mapping of the variety of parameters that are influenced by a given procedure should give clues not only to the generality of the changes that i t produces, but is also likely to suggest further mechanisms that may mediate or modulate the effect, For this reason, i t has been advocated that studies of putative pain modulation pro-cedures evaluate their effects over a range of dependent measures. One manner in which this has been attempted in studies of modeling influences on human pain has been through the assessment of changes in autonomically-mediated responses, In an early study, Craig and Niedermayer (1974) monitored skin conductance and heart-rate activity among subjects exposed to •".differentially pain-tolerant models. Subjects were exposed to two series of incremental electric shocks, signalled by the onset, six seconds prior to shock administration, of a light, and rated each on a 5-point categorical judgment scale. The study replicated earlier ones in that subjects exposed to a tolerant model accepted higher current intensi-ties and those exposed to an intolerant model accepted lower•intensities before describing them as painful than did subjects in two control condi-tions. Interestingly, in spite of the fact that the groups differed sub-stantially in the amount of current accepted, they could not be differ-entiated on measures of the magnitude of skin-conductance or heart-rate change to the shocks. The authors took these findings as evidence that the modeling procedure had produced alterations in the biophysical processes subserving subjective experiences' of pain and discomfort. Three major difficulties with this study required cautious interpretation of the findings. First, the findings were essentially negative and the 16 conclusions were taken as evidence that the. null hypothesis Has correct. Second, the use .of a warning stimulus may-have'introduced alterations In the dependent measures that masked more directly interpretable effects. Third, the choice of skin conductance as a dependent measure may have been inappropriate. As Tursky (1974.) subsequently pointed out, skin-conductance tends to exhibit ceiling effects and may thus f a i l to differentiate higher from lower current intensities. As an alternative measure, Tursky advo-cated the use of skin potential recorded from forearm and abdominal sites. In an attempt to re-evaluate and extend this earlier study, Craig and Prkachin (197 8) monitored skin-conductance, heart-rate, forearm and ab-dominal skin-potential responses to electric shock among subjects exposed to either a tolerant or an inactive "co-participant". Subjects generated numerical magnitude estimates to shocks presented during a single ascend-ing series, and a series of randomly-presented shocks at five standard in-tensities. Subjects exposed to a tolerant model exhibited significantly lower degrees of heart-rate acceleration to the current, and, unlike con-trol subjects, the magnitude of their forearm skin-potential responses habituated over the course of the random series. Thus, this study provided positive evidence for the reduction of autonomically-mediated responses as a function of exposure to pain-tolerant social modeling. The question of whether pain modulation resulting from social in-fluence procedures may be mediated by fundamental alterations in sensory/ perceptual processes has been addressed ..in two different ways. The first has been to employ S.S, Stevens' power law (Stevens, 1975) and numerical magnitude estimation tasks. The power law states that the perceived magnitude of a sensation ( grows as a function of the physical magnitude of the stimulus ( <j> .) raised to some power ( U ). The critical parameter in this procedure is the exponent ( n ) which Is traditionally interpreted to reflect the operating characteristic of sensory receptors with separate sensory modalities possessing a "true" value (Craig, Note 1) While al-ternative interpretations are available, there seems to be agreement that the exponent is descriptive of rates of growth of perceptual magnitude. Craig, Best, and Ward (1975) employed the standard tolerant model-ing, intolerant modeling, and control conditions while requiring subjects to generate estimates of the magnitude of discomfort provoked by, and physical intensity of electric shocks presented in ascending series on 10-poiht scales. Power functions were fitted to the data of individual subjects via linear regression of the logarithms of numerical responses on the logarithms of the geometric mean of stimuli associated with each response category. No differences between the groups on the value of the exponent were found. However, since individual subjects' data were not well fitted by the standard procedure, an alternative method was employed to estimate ideal power functions. This method (Teghtsoonian, 1971) ex-presses the value of the exponent as a function of the ratio of the largest to the smallest response value divided by the ratio of the largest to the smallest stimulus value, and thus is range-corrected. Exponents derived by this technique were significantly lower in the tolerant group than in the two other conditions. This finding prompted the conclusion that the tolerant modeling strategy had altered fundamental qualities of the ex-perience of pain. Craig (1978) employed power function analysis in a study that manipulated communication channels across different groups. Five groups of subjects generated numerical estimates of the magnitude of electric 18 current applied in ascending series. Subjects employed an open-ended scale modified from Hilgard, Ruch, Lange, Lenox, Morgan, and Sachs (1974) that anchored their responses at r'0" for^uiadetectabley" ' "1" for "detect-ablei" "10" for the point at which they would ordinarily wish to stop accepting currents. Subjects were encouraged to continue accepting shocks and to make proportionate ratings after giving a rating of "10." In group 1, standard tolerant modeling procedures were employed, with both subject and model providing concurrent ratings. Other groups varied according to whose information was available to whom. In group 2, only the subject verbalized her responses, in group 3 only the model verbalized, in group 4, both were silent, and in group 5, only the subject underwent the task, while the confederate remained explicitly inactive. Conventional linear regression of response magnitudes on stimulus magnitudes was employed in order to derive parameters of the power function. Analyses of values of the exponent revealed that the group exposed to standard interactive tolerant modeling and the group in which information regarding the model's rating was available to the subject exhibited lower values of the exponent relative to the inactive model control group. Why the conventional mode of analysis failed to discriminate groups in the first study yet did in the second is unclear. The reason for this may have had to do with differences in the tasks employed across the two studies, In the Craig, Best, and Ward (1974) study, subjects employed a 10 point rating scale anchored at the upper end by the descriptors "high intensity" or "painful." A rating of 10 terminated each test series, By contrast., subjects in Craig (1978) employed an open-ended scale and were instructed to use a rating of "10" for the 19 point at which, they would ordinarily w/lsh to terminate the series, The nature of the subjects' task in the first study may h.ave art i f actually altered their rating behaviour. A further possible source of the dis-crepancy may have been due to differences in the subjects' behaviour in the two studies. The mean of terminal current levels accepted by a l l groups in Craig, Best, and Ward (1974) was 5.7 milliamperes (mA) while that in Craig (1978) was 10.8 mA. Finally, in Craig e_t al_. (1975) subjects only rated the currents up to their first report of pain ("threshold") while in Craig (1978) subjects rated currents beyond this point. The above-noted methodological issues aside, i t would seem that the exponent of the power function relating stimulus intensity to sensation magnitude may ex-hibit systematic alterations associated with variations in modeling con-ditions . A second approach to assessing the nature of the changes produced in verbal rating indices of pain behaviour as a function of exposure to social influence conditions has been the use of signal-detection, or sensory-decision theory (SDT) methods (Green & Swets, 1966; McNicol, 1972; Pastore & Scheirer, 1974.) Since the present research made extensive use of SDT methods, and since there is currently a great deal of activity and controversy with respect to the application of SDT methods to pain research, this approach will be reviewed in some detail. Signal Detection Theory and Experimental Studies of Pairi Modulation Traditionally, studies of pain modulation have employed verbal rating tasks, and have been concerned with determining the extent to which the independent variables of interest are associated with alterations in 20 p a i n t h r e s h o l d o r . p a i n t o l e r a n c e , The p o i n t has a l r e a d y been made t h a t a l a r g e number o f v a r i a b l e s a r e c a p a b l e o f p r o d u c i n g a l t e r a t i o n s i n t h e s e p a r a m e t e r s ; i n f a c t , t h e r e a c t i v i t y o f s u c h measures t o m u l t i p l e s o u r c e s o f i n f l u e n c e was p a r t i a l l y r e s p o n s i b l e f o r t h e development o f t h e d o u b l e -b l i n d e x p e r i m e n t a l d e s i g n ( B e e c h e r , 1959). C l a r k ( 1 9 6 9 ) , however, argued t h a t such measures p r o v i d e l i m i t e d i n f o r m a t i o n because t h e y u n a v o i d a b l y confound the s u b j e c t ' s p e r c e p t u a l c a p a b i l i t i e s w i t h i n d e p e n d e n t a s p e c t s o f h i s o r h e r t e s t - t a k i n g b e h a v i o u r . When a s u b j e c t ' s p e r f o r m a n c e i n a p a i n e x p e r i m e n t changes such t h a t a l e v e l o f s t i m u l a t i o n p r e v i o u s l y d e s c r i b e d as p a i n f u l i s no l o n g e r so d e s c r i b e d , t h i s change may r e f l e c t a t l e a s t two u n r e l a t e d changes: (1) s e n s o r y p r o c e s s e s may have been a l t e r e d s u c h t h a t the s u b j e c t no l o n g e r p e r c e i v e s the s t i m u l i i n the same way, o r (2) s e n s -o r y p r o c e s s e s may have remained u n a f f e c t e d and t h e s u b j e c t may s i m p l y e x-h i b i t a g e n e r a l i z e d tendency t o a l t e r t he f r e q u e n c y w i t h w h i c h he o r she e m i t s a p a r t i c u l a r r e s p o n s e ( e . g . , " t h a t i s p a i n f u l " ) . SDT p r o v i d e s a methodology b a s e d on p r o b a b i l i t y t h e o r y f o r a s s e s s i n g t h e s e two a s p e c t s o f p e r f o r m a n c e , r e s p e c t i v e l y termed d i s c r i m i n a b i l i t y and r e s p o n s e b i a s . The SDT c o n c e p t i o n s t a t e s t h a t a s u b j e c t ' s performance on p e r c e p t u a l t a s k s i s p a r t i a l l y d e t e r m i n e d by d e c i s i o n - m a k i n g p r o c e s s e s . G i v e n the t a s k o f d e c i d i n g t o w h i c h o f n c l a s s e s o f s t i m u l u s e v e n t a p a r t i c u l a r e xemplar b e l o n g s , the s u b j e c t ' s r e s p o n s e w i l l be d e t e r m i n e d by a number o f f a c t o r s , i n c l u d i n g t he p r i o r p r o b a b i l i t y o f o c c u r r e n c e o f a g i v e n c l a s s , the reward a s s o c i a t e d w i t h an e r r o r , and the magnitude o f the d i f f e r e n c e s between the p e r t i n e n t c l a s s e s o f e v e n t . O nly the l a t t e r r e f l e c t s s e n s o r y p e r f o r m a n c e . I n the s i m p l e s t t y p e o f s i g n a l ^ d e t e c t i o n t a s k , an i n d i v i d u a l i s p r e s e n t e d w i t h a s e r i e s o f t r i a l s d u r i n g w h i c h one o f two e v e n t s may o c c u r . 21 The s u b j e c t i s s i m p l y r e q u i r e d t o r e p o r t whether a p a r t i c u l a r e v e n t (a s i g n a l ) d i d o r d i d n o t o c c u r . Four p o s s i b l e outcomes a r e a s s o c i a t e d w i t h t h i s k i n d o f t a s k : (1) the i n d i v i d u a l may c o r r e c t l y r e p o r t t h e o c c u r r e n c e of t h e e v e n t on a g i v e n t r i a l (a " h i t " ) , (2) s/he may r e p o r t t h a t the event d i d n o t o c c u r (a " m i s s " ) , (3) s/he may r e p o r t t h a t t h e event o c c u r r e d i n s p i t e o f t h e f a c t t h a t i t d i d n o t (a " f a l s e a l a r m " ) , o r (4) s/he may c o r r -e c t l y r e p o r t t h a t the e v e n t d i d n o t o c c u r (a " c o r r e c t r e j e c t i o n " ) . I t i s assumed t h a t t h e s i g n a l and t h e n o n - s i g n a l ("noise") e v e n t s each p r o v o k e an e x p e r i e n c e on t h e p a r t of t h e s u b j e c t , and t h a t t h e magnitude o f each e v e n t - p r o v o k e d e x p e r i e n c e v a r i e s a c c o r d i n g t o some s p e c i f i a b l e d i s t r i b u t i o n ( t y p i c a l l y n o r m a l ) . Assuming n o r m a l d i s t r i b u t i o n s o f t h e e x p e r i e n c e p r o -voked by s i g n a l and n o i s e , t h e p o s i t i o n s of t h e c u r v e s d e s c r i p t i v e o f t h e e x p e r i e n c e s can be p l o t t e d i n r e l a t i o n t o one a n o t h e r by e x a m i n i n g t h e p r o b a b i l i t i e s o f making a h i t and a f a l s e a l a r m . T h i s f o l l o w s from t h e a s s u m p t i o n t h a t t h e o b s e r v e r adopts a f i x e d c r i t e r i o n , s e t , a t a p a r t i c u l a r v a l u e a l o n g t h e continuum of s e n s o r y e x p e r i e n c e , and adopts a d e c i s i o n - r u l e ; any s e n s o r y e x p e r i e n c e t h a t exceeds t h e c r i t e r i o n v a l u e w i l l be i d e n t i f i e d as a s i g n a l , any e x p e r i e n c e w h i c h does n o t exceed t h i s c r i t e r i o n v a l u e w i l l be i d e n t i f i e d as n o i s e . I f t h e s e a s s u m p t i o n s h o l d , t h e n t h e p r o b a b i l i t i e s o f o c c u r r e n c e o f f a l s e - a l a r m s and h i t s , r e s p e c t i v e l y , d e f i n e t h e a r e a under the c u r v e o f t h e n o i s e and s i g n a l d i s t r i b u t i o n s l y i n g t o t h e r i g h t of t h e c r i t e r i o n . S i n c e t h e two c u r v e s a r e f i x e d i n r e l a t i o n t o one a n o t h e r by t h e a r e a s c u t o f f by t h e c r i t e r i o n , i t i s p o s s i b l e t o e x p r e s s t h e i r d i s t a n c e from one a n o t h e r i n s t a n d a r d - s c o r e u n i t s o f t h e n o i s e d i s t r i -b u t i o n . T h i s d i s t a n c e , termed d_', i s a p u r e measure o f s e n s o r y s e n s i t i v i t y , 22 or the discriminability of the two events, The procedure also provides a second independent parametr descriptive of where the observer has placed his or her criterion,- thus indexing the subject's bias toward reporting or not reporting the event. This parameter may be expressed in terms of likelihood-ratio '— the ratio of the height of the ordinate of the signal distribution at the criterion to the height of the ordinate of the noise distribution at the criterion (L or g) — or as the value of the criterion in standard-—x — score units of the noise distribution. Individuals may adopt very lax or very strict criteria for reporting the occurrence of the event. If the criterion is very strict, false-alarm rates will be reduced, hut so will hits. Alternatively, i f the criterion is very lax, both hits and false-alarms will be increased. In the case of or jB_ , a value exceeding 1.00 indicates bias against reporting the event, while a value of less than 1.00 indicates bias in favour of reporting i t . This basic paradigm can be modi-fied to accommodate a variety of stimulus presentations and a variety of rating tasks and, therefore, is readily adaptable to pain research. The first application of SDT methods to pain research was performed by Clark (1969) who evaluated the effect of placebo administration on ratings of thermal pain via traditional (threshold) and SDT procedures. Since that time, pain modulation studies employing SDT procedures have expanded vigor-ously. There is no need to review the substantive findings from this overall field of research since comprehensive reviews are available elsewhere (Hall, 1977; Lloyd & Appel, 1976; Rpllman, 1977), Applications of SDT methods to the study of.social modeling influences on pain will be discussed presently. 23 C r i t i c i s m s o f SDT p a i n r e s e a r c h , The SDT a p proach has p r o v o k e d c o n s i d e r a b l e e x c i t e m e n t i n the f i e l d o f p a i n r e s e a r c h , owing t o i t s a b i l i t y t o e x t r a c t i n d e p e n d e n t p a r a m e t e r s d e s -c r i p t i v e o f s u b j e c t s ' s e n s o r y p e r f o r m a n c e ( d i s c r i m i n a b i l i t y ) and t e s t - t a k i n g s e t ( r e s p o n s e - b i a s ) . However, s e v e r a l r e c e n t p a p e r s have c r i t i c i z e d the a p p r o a c h on c o n c e p t u a l , m e t h o d o l o g i c a l , and s u b s t a n t i v e grounds (Hayes, B e n n e t t , & Mayer, 1975; McBurney,.1975, 1976; R o l l m a n , 1977). B o t h McBurney and R o l l m a n have c h a r g e d i n one way o r a n o t h e r t h a t p a i n i s a s u b j e c t i v e e x p e r i e n c e d e f i n e d by a f f e c t i v e r e s p o n s e s , and t h a t s i n c e t h e SDT a p p r o a c h does n o t d e a l d i r e c t l y w i t h a f f e c t i v e r e s p o n s e s , i t i s i n a p p r o p r i a t e as a method f o r t h e s t u d y o f p a i n . As Chapman (1976) has a r g u e d , however, t h i s c r i t i c i s m r e f l e c t s a l i m i t e d v i e w o f t h e phenemena o f p a i n . C u r r e n t a c c o u n t s emphasize i t s m u l t i - d i m e n s i o n a l n a t u r e ( M e l z a c k & Casey, 1968; C r o c k e t t , P r k a c h i n , & C r a i g , 1977). W h i l e a f f e c t i v e components a r e c r u c i a l l y i m p o r t a n t , t h i s does n o t mean t h a t i n f o r m a t i o n r e g a r d i n g i t s s e n s o r y - d i s c r i m i n a t i v e a s p e c t s i s t r i v i a l . Because p a i n i s a m u l t i -d i m e n s i o n a l e x p e r i e n c e , i n c l u d i n g b o t h s e n s o r y and a f f e c t i v e components, s t u d i e s t h a t examine b o t h a s p e c t s may p r o v i d e p a r t i c u l a r l y i m p o r t a n t i n f o r -m a t i o n . The s t u d y by C r a i g and P r k a c h i n ( 1 9 7 8 ) , c i t e d e a r l i e r , p r o v i d e d e v i d e n c e t h a t e x p o s u r e t o a p a i n - t o l e r a n t s o c i a l model i s a s s o c i a t e d w i t h r e d u c e d v a l u e s o f d_' and r e d u c t i o n s i n autonomic and s e l f - r e p o r t i n d i c e s o f d i s t r e s s . R o l l m a n (1977) has a t t a c k e d the SDT a p p r o a c h on a v a r i e t y o f grounds and t h e r e i s v i g o r o u s debate i n the l i t e r a t u r e on the l e g i t i m a c y o f t h e c r i t i c i s m s (Chapman, 1977; H a l l , 1977), Two m a j o r c o n c e p t u a l p o i n t s a r e 24 levelled. The first is that SDT pain researchers tend to equate the sensi-tivity parameter with physiological processes, and the bias parameter with emotional or psychological processes, While there are instances in which researchers have made such claims (Lloyd & Wagner, 1976), they are neither essential nor common in SDT pain research (Chapman, 1977). tollman's second major conceptual point is that a l l SDT pain research adheres to four assumptions: (1) a reduction in neural activity can produce a reduction in experienced pain, (2) a reduction in neural activity will produce a re-duction in d_' , (3) a reduction in d_' indicates a reduction in experienced pain, (4) a reduction in experienced pain will be reflected in a reduction in d_' . Examples are cited of instances in which any or a l l of these assumptions might be incorrect. Chapman (1977, p.300), however, has point-ed out that inferences about neural processes are both unnecessary for and irrelevant to SDT pain studies which employ the technique "... as a probabil-ity model for perception and decision making that has no particular physio-logical reality." A major methodological point is that SDT pain experiments measure discrimination, not detection. The measurement of detection requires the use of a "zero stimulus", which subjects rarely confuse with noxious stimuli. There are methodological alternatives to this problem (Chapman, 1977). How-ever, as Hall (1977) has pointed out, Rollman's suggestion may involve a confusion between zero stimulus units and zero units on the "sensory continuum." In any event, SDT pain studies that do not employ a zero stimulus s t i l l measure discrimination which is a fundamental aspect of the pain experience. Despite these methodological and interpretive controversies, i t 25 can s t i l l be asserted that SPX methodology- can be effectively employed in separating discriminative capabilities and decision processes in relation to painful experiences. 26 RATIONALE Developing an account of the role that social events play as deter^ minants of pain processes requires the collection of information pertinent to a series of issues. The clear lack of isomorphism among alternative measures of pain demands a careful analysis of the ways in which pain modulating effects may be organized. SDT research, which rests upon the recognition that personal reports of pain reflect both sensory and decision-making pro-cesses represents one particular example of this type of approach. Evalu-ation of social influences on pain, like evaluation of the effects of other potentially pain-modulating procedures, requires an analysis of effects on psychophysical parameters based upon the subject's vocal report. An issue of equal importance for models of social effects on pain derives from the point made earlier that pain is largely inferred from behavioural observa-tion. Since social influences operate in a milieu wherein evidence of pain is a critical determinant of the responses of others, i t is of substantial interest to evaluate the effects of socially-based pain modulation proced-ures on behaviours that control the responses of others. While vocal report represents one such datum, also of critical interest is the nonvocal ex-pressive behaviour of the subject. Finally, an account of the role that social events play in pain-modulation requires information regarding how such factors may operate in the natural environment. In light of the above considerations, the following studies addressed 3 major issues, First was the issue of whether changes in expressions of pain resulting from social modeling influence procedures are reflected in 27 c o n c o m i t a n t changes i n s e n s o r y - d i s c r i m i n a t i o n c a p a b i l i t i e s , b i a s e s i n f a v o u r o f o r a g a i n s t r e p o r t i n g the e x p e r i e n c e o f p a i n , .or".'-both. E x p e r i m e n t 1 e v a l -u a t e d the i n f l u e n c e o f e x p o s u r e t o t o l e r a n t and i n t o l e r a n t s o c i a l models on t r a d i t i o n a l and SDT measures o f p a i n p e r c e p t i o n . I n a d d i t i o n , E x p e r i m e n t 1 p r o v i d e d d a t a used i n an e v a l u a t i o n o f t h e second.major i s s u e : whether s o c i a l m o d e l i n g i n f l u e n c e s have a more g e n e r a l i n f l u e n c e , beyond t h e l e v e l o f t h e d i s c r e t e b e h a v i o u r e n a c t e d by t h e m o del, t o the o v e r t e x p r e s s i v e d i s p l a y s o f the a f f e c t e d i n d i v i d u a l . V i d e o t a p e s were t a k e n o f t h e b e h a v i o u r o f s u b j e c t s u n d e r g o i n g the SDT t a s k i n E x p e r i m e n t 1. I n E x p e r i m e n t 2 t h e s e were shown t o n a i v e o b s e r v e r s i n a SDT t a s k r e q u i r i n g them t o d i s c r i m i n a t e t h e l e v e l s o f c u r r e n t t h a t o b s e r v e d s u b j e c t s were b e i n g exposed t o . E x p e r i m e n t 3 was c o n c e r n e d w i t h d e v e l o p i n g an e x p e r i m e n t a l a n a l o g o f t h e manner i n w h i c h p a i n e x p r e s s i o n s m i g h t o p e r a t e i n t h e n a t u r a l e n v i r o n m e n t . S u b j e c t s d i s p l a y i n g n a t u r a l l y - o c c u r r i n g v a r i a t i o n s i n p a i n b e h a v i o u r were exposed t o one an-o t h e r i n an a d a p t a t i o n o f the s t a n d a r d m o d e l i n g paradigm. T h i s p r o c e d u r e a l l o w e d a p a r t i a l e v a l u a t i o n o f t h e r e l a t i v e power o f p a i n t o l e r a n t and i n t o l e r a n t b e h a v i o u r i n a s i t u a t i o n p r o v i d i n g f o r m u t u a l i n f l u e n c e . 28 E x p e r i m e n t 1. S o c i a l m o d e l i n g I n f l u e n c e s on p a i n t h r e s h o l d , p a i n t o l e r a n c e and s e n s o r y - d e c i s i o n t h e o r y i n d i c e s . The i m p a ct o f e x p o s u r e t o s o c i a l models e x h i b i t i n g r e l a t i v e t o l e r -ance o r i n t o l e r a n c e f o r p a i n f u l e l e c t r i c a l s t i m u l a t i o n on r e p o r t s o f i n -i t i a l p a i n s e n s a t i o n ( p a i n t h r e s h o l d ) has been amply documented i n a s e r i e s o f s t u d i e s ( C r a i g & W e i s s , 1971, 1972; C r a i g , B e s t & R e i t h , 1974; C r a i g , B e s t , & Ward, 1976; C r a i g , B e s t , & B e s t , 1978; C r a i g & N i e d e r m a y e r , 1974). These p r o c e d u r e s a l s o have an i m p act a t s u p r a - p a i n t h r e s h o l d l e v e l s . T h i s has been d e m o n s t r a t e d i n s t u d i e s where s u b j e c t s were r e q u e s t e d t o c o n t i n u e a c c e p t i n g c u r r e n t s up t o the p o i n t a t w h i c h t h e y p r e f e r r e d t o q u i t ( C r a i g , 1978; C r a i g & B e s t , 1977), N e u f e l d and D a v i d s o n (1971) and Chaves and B a r b e r (1974) have r e p o r t e d s i m i l a r e f f e c t s u s i n g d i f f e r e n t p a i n - i n d u c t i o n t e c h n i q u e s . The e f f e c t s o f s o c i a l m o d e l i n g p r o c e d u r e s on t h e r e s p o n s e t o n o x i o u s s t i m u l a t i o n have been s u b s t a n t i a l . C o n s i s t e n t w i t h c u r r e n t t r e n d s i n p a i n r e s e a r c h , however, r e c e n t i n t e r e s t has been f o c u s s e d upon e v a l u -a t i o n o f s o c i a l m o d e l i n g e f f e c t s v i a SDT methodology. I n 3 s t u d i e s t h a t have employed SDT methods, e v i d e n c e has been c o n -s i s t e n t w i t h the p o s i t i o n t h a t e x p o s u r e t o t o l e r a n t and i n t o l e r a n t s o c i a l models p r o d u c e s a l t e r a t i o n s i n s e n s o r y - d i s c r i m i n a t i v e a s p e c t s o f r e s p o n s e t o n o x i o u s s t i m u l a t i o n . C r a i g and C o r e n (1975) exposed male u n d e r g r a d u a t e s t o t o l e r a n t o r i n t o l e r a n t s o c i a l models w h i l e t h e y j u d g e d a s c e n d i n g s e r i e s o f e l e c t r i c c u r r e n t s w h i c h were t e r m i n a t e d a t f i r s t r e p o r t o f p a i n . F o l l o w -i n g t h i s , 5 s t i m u l i were s e l e c t e d f r o m the range o f c u r r e n t s a d m i n i s t e r e d t o each s u b j e c t d u r i n g t h e t r a i n i n g s e r i e s and were p r e s e n t e d 12 t i m e s e ach i n a random o r d e r . A n a l y s e s o f t h e r a t i n g s o b t a i n e d v i a SDT t e c h n i q u e s i n d i -c a t e d t h a t e x p o s u r e t o an i n t o l e r a n t model was a s s o c i a t e d w i t h enhanced 29 a b i l i t y t o d i s c r i m i n a t e b e t y e e n t h e v a r i o u s s t i m u l u s l e v e l s w h i l e t o l e r a n t m o d e l i n g had no impact on t h e d i ^ s c r i j n i n a b i l i t y measure employed, S t i m u l i a d m i n i s t e r e d t o s u b j e c t s i n t h i s s t u d y were b a s e d upon proport-i o n s o f the maximum c u r r e n t s a d m i n i s t e r e d d u r i n g t h e t r a i n i n g s e r i e s , and s u b j e c t s o n l y r a t e d c u r r e n t s up t o p a i n t h r e s h o l d d u r i n g t h e s e s e r i e s . C o n s e q u e n t l y , the impact o f the m o d e l i n g c o n d i t i o n s on SDT p a r a m e t e r s measured a t c l e a r l y n o x i o u s l e v e l s o f s t i m u l a t i o n c o u l d n o t be a s s e s s e d . A l a t e r s t u d y employed SDT methodology t o i n v e s t i g a t e r e s p o n s e s t o s u p r a -t h r e s h o l d l e v e l s o f s t i m u l a t i o n ( C r a i g & Ward, Note 2 ) . Male u n d e r g r a d u a t e s r a t e d e l e c t r i c c u r r e n t s i n a s c e n d i n g s e r i e s on a s c a l e a n c h o r e d a t "unde-t e c t a b l e " and " v e r y p a i n f u l " , i n 2 s e s s i o n s . D u r i n g the a s c e n d i n g s e r i e s , s u b j e c t s were exposed t o a c o - p a r t i c i p a n t who was e i t h e r i n a c t i v e ( i . e . , n e i t h e r r a t e d n o r r e c e i v e d s h o c k s ) o r a c t i v e and t o l e r a n t ( i . e . , o s t e n s i b l y b o t h r e c e i v e d and r a t e d s h o c k s ) . An SDT s e r i e s was the n a d m i n i s t e r e d , c o n -s i s t i n g o f 10 random p r e s e n t a t i o n s o f each o f 10 s t i m u l u s l e v e l s , s e l e c t e d from v a r i o u s p r o p o r t i o n s o f maximum c u r r e n t s a c c e p t e d d u r i n g t h e a s c e n d i n g s e r i e s . R e s u l t s i n d i c a t e d t h a t e x p o s u r e t o a t o l e r a n t model was a s s o c i a t e d w i t h r e d u c e d a b i l i t y t o d i s c r i m i n a t e between t h e v a r i o u s s t i m u l i employed. These s t u d i e s have been c r i t i c i z e d on s e v e r a l grounds. F i r s t , a l -though i t i s s t a n d a r d p r a c t i c e t o a d m i n i s t e r i n d i v i d u a l i z e d s t i m u l u s l e v e l s i n SDT p a i n s t u d i e s , t h e manner i n w h i c h s t i m u l i were i n d i v i d u a l i z e d i n t h e s e s t u d i e s confounded s t i m u l u s i n t e n s i t i e s w i t h groups ( H a l l , 1977). I n the s t u d y by C r a i g and Coren (1975) s u b j e c t s exposed t o an i n t o l e r a n t model accep'ted.Hower. c u r r e n t s and s u b j e c t s exposed t o a t o l e r a n t model a c c e p t e d h i g h e r c u r r e n t s t h a n d i d c o n t r o l s , Thus, s t i m u l u s l e v e l s employed d u r i n g t h e SDT s e r i e s were l o w e r i n a b s o l u t e v a l u e and d i f f e r e n c e s between 30 a d j a c e n t p a i r s were s m a l l e r f o r IntoXerants, t h a n c o n t r o l s , w h i l e a b s o l u t e v a l u e s and p a i r d i f f e r e n c e s were h i g h e r f o r t o l e r a n t s , The same p r o b l e m h e l d i n t h e C r a i g and Ward (Note 2) s t u d y . On t h e one hand, i t can be a rgued t h a t t h i s confound r e s u l t e d i n a c o n s e r v a t i v e t e s t o f the h y p o t h e s e s s i n c e i n t o l e r a n t s u b j e c t s i n the C r a i g and Coren s t u d y showed enhanced d i s c r i m i n a t i o n i n s p i t e o f t h e f a c t t h a t d i f f e r e n c e s between t h e s t i m u l i t h e y r e c e i v e d were s m a l l r e l a t i v e t o t h o s e i n t h e o t h e r g r o u p s . S i m i l a r l y , i n the C r a i g and Ward s t u d y , t o l e r a n t s u b j e c t s showed r e d u c e d a b i l i t y t o d i s -c r i m i n a t e t h e s t i m u l i , w h i l e t h e d i f f e r e n c e s between l e v e l s a d m i n i s t e r e d t o them were l a r g e , r e l a t i v e t o s u b j e c t s i n c o n t r o l c o n d i t i o n s . On t h e o t h e r hand, Weber's law w o u l d p r e d i c t enhanced d i s c r i m i n a t i o n between s t i m u l u s p a i r s a t low i n t e n s i t i e s and r e d u c e d d i s c r i m i n a t i o n a t h i g h e r i n t e n s i t i e s . I f Weber's law h o l d s f o r t h e l e v e l s o f s t i m u l a t i o n employed i n t h e s e s t u d i e s , the f i n d i n g s m i g h t be a c c o u n t e d f o r on t h i s b a s i s a l o n e . These s t u d i e s have a l s o been c r i t i c i z e d • on the ground t h a t too few s t i m u l i were p r e s e n t e d a t each i n t e n s i t y t o a l l o w r e l i a b l e e s t i m a t i o n o f the SDT p a r a m e t e r s ( R o l l m a n , 1977). L l o y d and A p p e l ( 1 9 7 6 ) , f o l l o w i n g M c N i c o l (1972) have argued t h a t SDT p a i n s t u d i e s s h o u l d i n c l u d e a t l e a s t 50 p r e s e n t a t i o n s o f each s t i m u l u s i n t e n s i t y . A t h i r d a r e a o f a m b i g u i t y i n t h e C r a i g and Ward s t u d y p e r t a i n s t o t h e a t t e m p t to.draw c o n c l u s i o n s about the i n f l u e n c e o f t o l e r a n t m o d e l i n g p r o -c e d ures on the d i s c r i m i n a b l l i t y o f s u p r a - p a i n - t h r e s h o l d s t i m u l u s l e v e l s . D e s p i t e t h e use o f s u p r a t h r e s h o l d s t i m u l u s l e v e l s , the mode o f d a t a -r e d u c t i o n employed i n t h i s s t u d y i n v o l v e d the c a l c u l a t i o n o f an o v e r a l l i n d e x by t a k i n g t h e mean o f a l l d i s c r i m i n a t i o n measures c a l c u l a t e d f o r each-s u b j e c t . I t c o u l d n o t be d e t e r m i n e d , t h e r e f o r e , whether the r e d u c e d 31 d i s c r i m i n a t i o n a b i l i t y o b s e r v e d among s u b j e c t s exposed t o a t o l e r a n t model r e f l e c t e d r e d u c e d d i s c r i m i n a b i l i t y o f t h e more i n t e n s e shock p a i r s , t he l e s s i n t e n s e p a i r s , o r b o t h . A s t u d y by C r a i g and P r k a c h i n (1978) overcame t h e g r o u p / s t i m u l u s l e v e l c o n f o u n d i n g by a d m i n i s t e r i n g s t a n d a r d c u r r e n t i n t e n s i t i e s t o a t o l e r -a n t m o d e l i n g group and a no m o d e l i n g c o n t r o l group. S u b j e c t s i n t h e t o l e r -a n t group e x h i b i t e d l o w e r o v e r a l l a b i l i t y t o d i s c r i m i n a t e t h e c u r r e n t s , as i n t h e C r a i g and Ward s t u d y . However, s i n c e s t a n d a r d s t i m u l u s i n t e n s i t i e s were employed, some o f the s t i m u l i may have been w e l l beyond n o x i o u s l e v e l s f o r some s u b j e c t s , b u t n o t f o r o t h e r s . I f v a l i d i n f e r e n c e s a r e t o be drawn about p a i n s e n s i t i v i t y , i t w o u l d seem p r e f e r a b l e t o en s u r e t h a t some o f t h e s t i m u l u s i n t e n s i t i e s employed have a t some t i m e been d e s c r i b e d by the sub-j e c t as n o x i o u s . O t h e r problems w i t h t h i s s t u d y i n c l u d e the f a c t t h a t no a t t e m p t was made t o d e t e r m i n e whether d_' was r e d u c e d a t a l l , o r o n l y some p a i r s o f s t i m u l u s i n t e n s i t i e s . Thus, i t i s unknown whether t h e f i n d i n g s r e f l e c t e d an o v e r a l l r e d u c t i o n i n t h e d i s c r i m i n a b i l i t y o f c u r r e n t s , o r o n l y a r e d u c t i o n a t n o x i o u s o r no n - n o x i o u s i n t e n s i t i e s . The p r e s e n t s t u d y was d e s i g n e d t o overcome some o f t h e c r i t i c i s m s • a p p l i e d t o p r e v i o u s SDT a n a l y s e s o f t h e e f f e c t s o f s o c i a l m o d e l i n g p r o c e d -u r e s on p a i n . To e n s u r e t h a t the d a t a o b t a i n e d w o u l d r e f l e c t r e s p o n s e s b o t h t o n o x i o u s and n o n - n o x i o u s i n t e n s i t i e s , s t i m u l i employed i n t h e SDT p r o c e d u r e were s e l e c t e d from 3 l e v e l s d e f i n e d by t h e s u b j e c t ' s b e h a v i o u r d u r i n g an u n i n f l u e n c e d p r e a s s e s s m e n t s e s s i o n . These were: (1) around d e t e c t i o n t h r e s -h o l d , (2) j u s t b e l o w p a i n t h r e s h o l d , and (3) midway between p a i n t h r e s h o l d and p a i n t o l e r a n c e . D e t e r m i n a t i o n o f t h e l o c u s , a l o n g t h e shock i n t e n s i t y d i m e n s i o n , o f any e f f e c t o f t h e s o c i a l i n f l u e n c e c o n d i t i o n on 32 discriminability was to be evaluated by comparing groups at each stimulus pair. Including an uninfluenced preassessment session also allowed random assignment of subjects to one of 3 social influence groups, thus avoiding the problem of group/stimulus intensity confounding. Further, Lloyd and Appel's (1976) recommendation that at least 50 presentations of each stim-ulus intensity be employed was adopted. The task employed in the SDT portion of the present study required subjects to rate each stimulus on a 7-point scale of pain intensity. A con-current forced-choice rating was also employed. At each overall level of intensity (detection threshold, sub-pain-threshold, supra-pain-threshold), 2 stimuli were presented, differing by 0.25 milliamperes (mA). The forced-choice task required subjects to identify whether the higher member of the pair was the first or the second to be presented. Previous research employ-ing thermal nociceptive stimulation has indicated that different SDT pro-cedures are not equivalent, in that indices of discriminability (d_') based on rating scale tasks are less reliable than those based on 2-alternative, binary decision tasks (Clark & Dillon, 1973; Clark & Mehl, 1973). The forced-choice procedure was included in this study as an alternative means of assessing stimulus discriminability. The design of the experiment called for an in i t i a l assessment of pain threshold and tolerance in the absence of social influence. In a subsequent influence session, subjects were exposed to tolerant modeling, intolerant modeling, or control procedures, followed by assessment of the impact of the procedures on SDT parameters. Various alternatives were available in the choice of rating tasks. Categorical judgment procedures are most appropriate in SDT tasks since subjects tend to use them consistently, and under 33 f a v o u r a b l e c o n d i t i o n s t h e y a l l o w t h e e s t i m a t i o n o f s e n s o r y s e n s i t i v i t y a t s e v e r a l p o i n t s ( c r i t e r i a ) a l o n g the r a t i n g s c a l e . However, a number o f c o n s i d e r a t i o n s s u g g e s t e d t h a t magnitude e s t i m a t i o n w o u l d be a more a p p r o -p r i a t e p r o c e d u r e t o employ d u r i n g the p r e s e n t a t i o n o f t h e a s c e n d i n g s e r i e s o c c u r r i n g p r i o r t o the SDT t a s k . F i r s t , magnitude e s t i m a t i o n p r o c e d u r e s p r o v i d e r e l i a b l e and s e n s i t i v e measures o f . c h a n g e s i n e x p e r i m e n t a l l y -i n d u c e d p a i n and a r e p a r t i c u l a r l y s u i t e d f o r paradigms t h a t i n v o l v e con-t i n u o u s i n c r e a s e s i n s t i m u l u s i n t e n s i t y ( G r o s s b e r g & G r a n t , 1976; H i l g a r d , 1967, 1969; C r a i g , B e s t , & Ward, 1975). Second, they can be a d a p t e d i n a manner t h a t a l l o w s the s u b j e c t t o r e p o r t the o c c u r r e n c e o f d i s c r e t e p o i n t s a l o n g t h e p a i n continuum w h i l e g e n e r a t i n g p r o p o r t i o n a t e r a t i n g s o f t h e magnitude o f i n d u c e d p a i n . F o r example, H i l g a r d , Ruch, Lange, Lenox, Morgan, and Sachs (1974) used an open-ended s c a l i n g p r o c e d u r e t h a t r e -q u i r e d s u b j e c t s t o c o n t i n u o u s l y a s s i g n n u m e r i c a l r a t i n g s t o t h e s e n s a t i o n s i n d u c e d by c o l d - p r e s s o r p a i n up t o the p o i n t a t w h i c h they t e r m i n a t e d the p r o c e d u r e . I n s t r u c t i o n s i n t h e use o f the s c a l e r e q u i r e d s u b j e c t s t o r e -s e r v e a r a t i n g o f "10" f o r t h a t p o i n t a t w h i c h they w o u l d l i k e t o s t o p the p r o c e d u r e ; however, t h e y were encouraged t o p e r s e r v e r e beyond t h i s p o i n t w h i l e c o n t i n u i n g t o make p r o p o r t i o n a t e r a t i n g s . T h i r d , r e c e n t e x p e r i e n c e i n t h i s l a b o r a t o r y has s u g g e s t e d t h a t magnitude e s t i m a t i o n p r o c e d u r e s a r e p a r -t i c u l a r l y s e n s i t i v e t o the e f f e c t s o f v a r i a t i o n s i n s o c i a l i n f l u e n c e p r o -c e d u r e s . ( C r a i g , 1978). Method S u b j e c t s . S u b j e c t s were 36 f e m a l e u n d e r g r a d u a t e v o l u n t e e r s r e c r u i t e d from i n t r o d u c t o r y P s y c h o l o g y c o u r s e s a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a (M age=18.6S.D. = l . . l . ) . S u b j e c t s were c o n t a c t e d by t e l e p h o n e and o f f e r e d $4.00 34 f o r p a r t i c i p a t i o n i n an e x p e r i m e n t on p e r c e p t i o n t h a t w o u l d i n v o l v e a t t e n d -i n g two s e s s i o n s . Of t h o s e who a r r i v e d a t t h e l a b o r a t o r y f o r S e s s i o n 1, f o u r r e f u s e d t o p a r t i c i p a t e when the, e x p e r i m e n t had been d e s c r i b e d t o them, w h i l e one was e x c u s e d on m e d i c a l grounds. Upon b e i n g c o n t a c t e d t o a r r a n g e S e s s i o n 2, 8 more i n d i c a t e d t h e i r u n w i l l i n g n e s s t o r e t u r n f o r a second s e s s i o n . F o l l o w i n g t h e i r p a r t i c i p a t i o n i n S e s s i o n 1, s u b j e c t s were random-l y a s s i g n e d t o one o f t h r e e e x p e r i m e n t a l c o n d i t i o n s f o r . S e s s i o n 2. A p p a r a t u s and E x p e r i m e n t a l Environment E l e c t r i c c u r r e n t s o f 0.5 s e c . d u r a t i o n were c o n t r o l l e d by a H u n t e r Decade I n t e r v a l t i m e r and d e l i v e r e d t h r o u g h c o n c e n t r i c a n n u l a r e l e c t r o d e s ( T u r s k y , Watson, and O ' C o n n e l l , 1965) v i a a 60 Hz c o n t r o l l e d - c u r r e n t e l -e c t r o s t i m u l a t o r ( L a f a y e t t e I n s t r u m e n t Co., Model A-6158). V i d e o t a p e r e -c o r d i n g s were made on h a l f - i n c h v i d e o t a p e , u s i n g a Sony Model AV-3400 v i d e o -c o r d e r and camera. The e x p e r i m e n t a l room c o n t a i n e d t h e s t i m u l a t i o n equipment, and two c h a i r s . S u b j e c t s were s e a t e d b e s i d e a wooden p a r t i t i o n w h i c h , i n S e s s i o n 2, v i s u a l l y i s o l a t e d the s u b j e c t and the model. A wooden p a r t i t i o n a l s o v i s -u a l l y i s o l a t e d the s u b j e c t from the e x p e r i m e n t e r and the c o n t r o l equipment. The v i d e o t a p e camera was s i t u a t e d a p p r o x i m a t e l y 2 meters i n f r o n t o f the s u b j e c t and i n f u l l v i e w . I n o r d e r t o i n d i c a t e s t i m u l u s o c c u r r e n c e s on the v i d e o t a p e s , a 1 cm. d i a m e t e r j e w e l l i g h t was l o c a t e d b e h i n d and s l i g h t -l y t o t h e l e f t o f t h e s u b j e c t ' s head and was c o n t r o l l e d by t h e t i m i n g equipment t o i l l u m i n a t e c o n c u r r e n t l y w i t h s t i m u l u s p r e s e n t a t i o n and r e m a i n on f o r a d u r a t i o n o f 5 s e c . A wooden p a r t i t i o n was l o c a t e d a t r i g h t a n g l e s t o t h e p a r t i t i o n i s o l a t i n g the s u b j e c t from the e x p e r i m e n t e r . To the r i g h t o f t h i s p a r t i t i o n , i s o l a t e d from t h e s u b j e c t ' s v i e w , was a 1 cm. j e w e l 35 l i g h t . D u r i n g b o t h s e s s i o n s , s h e e t s o f p a p e r t h a t d e p i c t e d t h e r a t i n g s c a l e s were a f f i x e d t o the p a r t i t i o n b l o c k i n g t he s u b j e c t ' s v i e w o f t h e e x p e r i m e n t e r . S u b j e c t s were s e a t e d i n t h e same c h a i r i n b o t h s e s s i o n s . I n -c l u d i n g a se c o n d p e r s o n , t h e model, i n S e s s i o n 2 r e q u i r e d t h a t she be s e a t e d t o t he s u b j e c t ' s r i g h t so t h a t t h e "dummy" e l e c t r o d e c o u l d be a t t a c h e d t o h e r . P r o c e d u r e . S e s s i o n 1 S u b j e c t s were g r e e t e d a t the l a b o r a t o r y by the e x p e r i m e n t e r , who i n -d i c a t e d t h a t a n o t h e r s u b j e c t w o u l d be coming and t h e n t h e e x p e r i m e n t w o u l d be under way. The pu r p o s e o f t h i s r u s e was t o a v o i d a r o u s i n g s u s p i c i o n s a t t he i n t r o d u c t i o n o f an o s t e n s i b l e c o - p a r t i c i p a n t i n S e s s i o n 2. A f t e r a few m i n u t e s ' c o n v e r s a t i o n w i t h t he s u b j e c t , t he e x p e r i m e n t e r s t a t e d , "As l o n g as we're w a i t i n g , I might as w e l l g et y o u s t a r t e d by g i v i n g y o u a c o u p l e o f q u e s t i o n n a i r e s t o work on." S u b j e c t s t h e n c o m p l e t e d t h e S-R I n v e n t o r y o f G e n e r a l T r a i t A n x i e t y ( E n d l e r and Okada, 1975) and t h e Sub-j e c t i v e S t r e s s S c a l e (SSS; N e u f e l d and D a v i d s o n , 1972). W h i l e s u b j e c t s were c o m p l e t i n g t he q u e s t i o n n a i r e s , t he e x p e r i m e n t e r c o m p l e t e d p r e p a r a t i o n , o f t he equipment, and made a c o u p l e o f f o r a y s t o t h e door t o l o o k f o r t h e " o t h e r s u b j e c t 1 . " When t h e s u b j e c t had com p l e t e d t h e q u e s t i o n n a i r e s , t h e e x p e r i m e n t e r s u g g e s t e d t h a t t h e e x p e r i m e n t s h o u l d p r o c e e d w i t h o u t t h e o t h e r s u b j e c t . The e x p e r i m e n t was t h e n d e s c r i b e d as a s t u d y i n " t h e p e r c e p t i o n o f d i s c o m f o r t r e s u l t i n g f r o m m i l d e l e c t r i c a l s t i m u l a t i o n . " The p r o c e d u r e s and s t i m u l a t i o n were d e s c r i b e d , and t h e s u b j e c t was g i v e n t h e o p p o r t u n i t y t o w i t h d r a w . When c o n s e n t had been o b t a i n e d , t h e s u b j e c t was s e a t e d i n the e x p e r i m e n t a l room and t h e f o l l o w i n g i n s t r u c t i o n s were r e a d : I'm g o i n g t o p r e s e n t y o u w i t h a s e r i e s o f low c u r r e n t s t h a t w i l l s t a r t a t u n d e t e c t a b l e l e v e l s and w i l l g r a d u a l l y i n c r e a s e i n i n t e n s i t y and d i s c o m f o r t . Y o u r t a s k w i l l be t o i n d i c a t e how 36 u n c o m f o r t a b l e each momentary c u r r e n t f e e l s by a s s i g n i n g i t a number r a n g i n g from z e r o up t o 10, and t h e n beyond. I n -i t i a l l y , t h e c u r r e n t w i l l be so low t h a t you w i l l p r o b a b l y f e e l n o t h i n g . I f t h i s i s t h e c a s e , t h e r a t i n g " z e r o " , f o r " u n d e t e c t a b l e " , i s a p p r o p r i a t e . T h e r e a f t e r , t h e y w i l l g r a d -u a l l y i n c r e a s e i n i n t e n s i t y and d i s c o m f o r t . We woul d l i k e y o u t o r a t e each subsequent shock i n p r o p o r t i o n t o t h e amount o f d i s c o m f o r t t h a t y ou f e e l , so t h a t , f o r example, i f on one c u r r e n t y o u g i v e a r a t i n g o f " 2 " , and t h e n a l a t e r one f e e l s t w i c e as u n c o m f o r t a b l e , y ou g i v e the l a t e r one a r a t i n g o f "4". (These r a t i o i n s t r u c t i o n s were based on t h o s e employed by C r a i g & P r k a c h i n , 1978, and C r a i g , 1978a). H i g h e r r a t -i n g s s h o u l d r e f l e c t i n c r e a s e s i n p h y s i c a l d i s c o m f o r t . You w i l l e v e n t u a l l y r e a c h a l e v e l o f c u r r e n t t h a t y ou w o u l d des-c r i b e as g i v i n g y o u a s e n s a t i o n o f " v e r y f a i n t p a i n . " We w o u l d l i k e y o u t o g i v e t h a t c u r r e n t a r a t i n g o f "10" and th e n we'd l i k e y o u t o c o n t i n u e a c c e p t i n g c u r r e n t s f o r as l o n g as p o s s i b l e a f t e r you've r e a c h e d t h i s l e v e l . When you r e a c h t h e p o i n t where you don't w i s h t o a c c e p t any f u r t h e r s t i m u l i , g i v e t h a t c u r r e n t y o u r f i n a l r a t i n g , c a l l o ut t h e word " t e r m i n a t e " and no more w i l l be g i v e n t o you. A f t e r t h e s u b j e c t had i n d i c a t e d h e r u n d e r s t a n d i n g o f t h e i n s t r u c t i o n s , t h e e x p e r i m e n t e r s t a t e d , "We l i k e t o v i d e o t a p e each s e s s i o n so t h a t I can check on the a c c u r a c y o f my r e c o r d i n g s , " and the v i d e o t a p e camera was t h e n f o c u s s e d on h e r . Redux p a s t e was t h e n a p p l i e d t o t h e s u b j e c t ' s l e f t f o r e a r m , and t h e e l e c t r o d e p o s i t i o n e d as n e c e s s a r y t o reduc e the r e s i s t a n c e i n the e l e c t r o d e -s k i n c i r c u i t t o 5000 ohms ( T u r s k y e_t a l . , 1965). S u b j e c t s t h e n underwent two a s c e n d i n g s e r i e s o f t h e p s y c h o p h y s i c a l method o f l i m i t s w i t h c u r r e n t l e v e l s s t a r t i n g a t 0.0 mA and i n c r e a s i n g i n 0.5 mA s t e p s u n t i l a " t e r m i n a t e " r a t i n g was g i v e n . I n t e r - s t i m u l u s i n t e r v a l s were 10 s e c . V i d e o r e c o r d i n g s were t a k e n c o n t i n u o u s l y t h r o u g h o u t b o t h s e r i e s . A t t h e end o f the se c o n d s e r i e s , s u b j e c t s c o m p l e t e d t h e SSS and t h e a d j e c t i v e c h e c k l i s t p o r t i o n o f the M c G i l l P a i n Q u e s t i o n n a i r e (MPQ; M e l z a c k & T o r g e r s o n , 1971) w i t h i n -s t r u c t i o n s t o r a t e t h e h i g h e s t s h o c k " a c c e p t e d . S u b j e c t s were t h e n d i s m i s s e d w i t h i n s t r u c t i o n s n o t t o t a l k about the e x p e r i m e n t . 37 Session 2 Subjects returned for Session 2 a mean of 15 .,3days (S.D.= 12. 4) after Session 1. The model typically arrived several minutes later than the subject. Four females, aged 20, 21, 21, and 28 served as models. The model was always treated as i f she were a naive subject. When both had arrived, subject and model were introduced and given the SSS to f i l l out. They were then escorted to the experimental room, seated in their appropriate chairs, and had the following instructions read to them: The first part of what we will do today is going to be identical to what occurred during the first session. Let me review things briefly to refresh your memory. I will again present you with a series of low currents starting at unde-tectable levels that will gradually increase in intensity. As before, I would like you to rate them on the 0 to 10 scale with 0 standing for undetectable, 10 standing for very faint pain, and so on. As before, make your ratings in proportion to the amount of discomfort that you feel. When you reach the point where you don't wish to accept any further stimuli, give that current your final rating, call out the word "terminate", and no more will be given to you. Electrodes were then attached to both subject and model. Immediately be-fore commencing shock administration, the experimenter instructed the sub-ject that she should give her rating first, followed by the model. Sub-jects then went through 3 series of electric shocks, each increasing in 0.5 mA steps from 0.0 mA until they gave their "terminate" rating, or until a maximum current of 18.0 mA had been accepted. During this session, subjects were exposed to one of 3 experimental treatments. Those assigned to the tolerant (T) group made their ratings concurrently with a model who consistently assigned ratings to the shocks that were 25% lower than those of the subject. When the subject had given her "terminate" rating, the experimenter informed her that no more shocks 38 would be given to her, but shocks would continue for the model. On the following t r i a l , the model gave the same rating she had given on the subject's "terminate" t r i a l . On the next two t r i a l s , the model gave ratings increasing by one rating-scale unit and then gave her "terminate" rating. These contingencies did not, of course, apply when subjects had taken currents up to the maximum of 18.0 mA. In the intolerant (I) condition, subjects were exposed to a model who consistently rated the shocks to be 25% higher than did the subject. Further contingencies for the role required that the model rate the f i r s t current at "0" and the second at "1). When the subject gave her f i r s t rating above "10", the model gave her corresponding rating, and then gave a "terminate" rating. The model was then informed that no more shocks would be given to her, and the series proceeded unt i l the subject gave a "terminate" rating. In the control (C) condition, following reading of the preliminary instructions, the experimenter stated that for the f i r s t part of the ex-periment, only the subject would be receiving shocks and should respond. Videotape recordings were made of subjects during a l l 3 ascending series in Session 2. SDT Series Following completion of the 3 ascending series, a second phase of the experiment, concerned with SDT analyses, began. In this phase, sub-jects were exposed to a series of pairs of shocks that had been selected on the basis of the subject's performance during the second ascending series of Session 1. The f i r s t pair consisted of that current f i r s t report-ed as detectable during the second ascending series of Session 1 (i.e., the f i r s t nonzero rating), and a current level 0.25 mA lower. The second pair 39 c o n s i s t e d o f t h e c u r r e n t l e v e l r a t e d as "8" and t h a t l e v e l minus 0.25 mA. When no "8" r a t i n g had o c c u r r e d , t h e c l o s e s t r a t i n g l o w e r t h a n "8" and t h a t l e v e l minus 0.25 mA were used. The t h i r d p a i r c o n s i s t e d o f the c u r r e n t l e v e l c o r r e s p o n d i n g t o t h e r a t i n g o c c u r r i n g h a l f w a y between "10" and " t e r m i n a t e " , and t h a t l e v e l minus 0.25 mA. P r i o r t o i n i t i a t i n g t h e SDT s e r i e s , t h e f o l l o w i n g s e t o f i n s t r u c -t i o n s was r e a d : The n e x t p a r t o f t h e e x p e r i m e n t i s g o i n g t o be q u i t e a b i t d i f f e r e n t . I n t h i s p a r t , I'm g o i n g t o p r e s e n t you w i t h a s e r i e s o f p a i r s o f c u r r e n t s t h a t w i l l o c c u r i n random o r d e r . Each p a i r w i l l o c c u r v e r y q u i c k l y . I n t h i s p a r t y o u r t a s k w i l l be a l i t t l e b i t more c o m p l i c a t e d . I n s t e a d o f r a t i n g t h e c u r r e n t s on t h e 0 t o 10 and above s c a l e t h a t you've been u s i n g , we w o u l d l i k e y ou t o r a t e each c u r r e n t u s i n g t h e c a t e g o r i e s t h a t I am g o i n g t o p u t up on t h e s e s h e e t s . The e x p e r i m e n t e r t h a n r e p l a c e d t h e s h e e t s c o n t a i n i n g t h e r e p r e s e n t a t i o n o f t h e 0 - 1 0 s c a l e w i t h s h e e t s t h a t d e p i c t e d a 7 - p o i n t c a t e g o r i c a l judgment s c a l e c o n s i s t i n g o f t h e f o l l o w i n g d e s c r i p t o r s and r a t i n g s c a l e numbers: 0 — U n d e t e c t a b l e , 1 — F a i n t S e n s a t i o n , 2 — P r e - P a i n S e n s a t i o n , 3 — V e r y F a i n t P a i n , 4 — M i l d P a i n , 5 — Moderate P a i n , 6 — S t r o n g P a i n . T h i s s c a l e was b a s e d on t h a t used by Chapman and h i s a s s o c i a t e s (Chapman, G e h r i g , & W i l s o n , 1 9 7 5 ) , b u t m o d i f i e d t o a l l o w f o r shock i n d u c e d s e n s a t i o n s below p a i n t h r e s h o l d . The i n s t r u c t i o n s t h e n c o n t i n u e d as f o l l o w s : I n d i c a t e y o u r c h o i c e by a s s i g n i n g each c u r r e n t a number c o r r e s p o n d i n g t o a c a t e g o r y on the s h e e t . Take a c l o s e l o o k a t t h e c a t e g o r i e s f o r we want you t o l e a r n w h i c h number goes w i t h w h i c h l a b e l as soon as you can. N o t i c e t h a t un-d e t e c t a b l e i s s t i l l g i v e n a r a t i n g o f 0 j u s t l i k e i t was on t h e o l d s c a l e . However, v e r y f a i n t p a i n , w h i c h was on t h e o l d s c a l e was 10, i s now t o be g i v e n a r a t i n g o f 3. One would, be used t o i n d i c a t e t h a t you can j u s _ t ~ d e t e c t t h e s h o c k , w h i l e 2 i n d i c a t e s t h a t you can d e f i n i t e l y f e e l t h e shock b u t i t i s n o t y e t p a i n f u l . 40 I w i l l a l s o ask y o u t o make a second t y p e o f r a t i n g . As I s a i d , I am g o i n g t o p r e s e n t t h e s t i m u l i t o y o u i n p a i r s . A f t e r y o u have r a t e d b o t h s t i m u l i on t h e 0 - 6 s c a l e , I w o u l d l i k e y o u t o t e l l me whether y o u t h i n k t h a t t h e h i g h e r , or t h e more i n t e n s e s t i m u l u s of t h e p a i r was t h e f i r s t one t o be p r e s e n t e d o r t h e second. I n d i c a t e y o u r c h o i c e by c a l l i n g out t h e words " f i r s t " o r " s e c o n d . " A t t h i s p o i n t , s u b j e c t s were a l s o i n f o r m e d t h a t none of t h e c u r r e n t s t o be a d m i n i s t e r e d w o u l d be any h i g h e r t h a n t h e y had a c c e p t e d i n t h e p a s t . The e x p e r i m e n t e r t h e n i n s u r e d t h a t t h e s u b j e c t u nder-s t o o d t h e t a s k . One hundred s i x t y - t w o s t i m u l u s p a i r s , b a l a n c e d e q u a l l y f o r low, medium, and h i g h p a i r s ( i . e . , t h e r e were 54 p r e s e n t a t i o n s of each p a i r ) were t h e n p r e s e n t e d i n a random o r d e r , s u b j e c t t o t h e c o n d i t i o n d e s c r i b e d below i n t h e g r o u p i n g o f t r i a l s i n t o b l o c k s . S t i m u l u s p a i r s were a l s o b a l a n c e d e q u a l l y i n terms of whether t h e f i r s t o r t h e second o f t h e p a i r was h i g h e r . Thus, t h e p r i o r p r o b a b i l i t i e s of o c c u r r e n c e o f low, medium, and h i g h p a i r s were e q u a l a t .33 as were p r i o r p r o b a b i l -i t i e s f o r the b i n a r y d i s c r i m i n a t i o n (.50). The e n t i r e SDT s e r i e s was b r o k e n down i n t o 3 b l o c k s of 54 s t i m u l u s p a i r s . W i t h i n each b l o c k was i n c l u d e d 3 s e r i e s o f 18 s t i m u l u s p a i r s , b a l a n c e d e q u a l l y f o r c u r r e n t m agnitude ( i . e . , 6 p r e s e n t a t i o n s each o f low, medium and h i g h p a i r s . ) and f o r whether t h e f i r s t o r second s t i m u l u s o f each p a i r was h i g h e r . W i t h i n each b l o c k , t h e o r d e r o f p r e s e n t a t i o n of each s e r i e s was r a n d o m i z e d on a s u b j e c t - b y - s u b j e c t b a s i s . V i d e o t a p i n g o f s u b j e c t s d u r i n g t h e SDT s e r i e s o c c u r r e d on the f i r s t s e r i e s of B l o c k 1, t h e second s e r i e s o f B l o c k 2, and t h e t h i r d s e r i e s of B l o c k 3. Thus, v i d e o t a p e s of 1/3 o f s t i m u l u s p r e s e n t a t i o n s i n t h e SDT s e r i e s o c c u r r e d , and c o r r e s p o n d e d t o t h e f i r s t , f i f t h , and n i n t h s e r i e s o f 18 s t i m u l u s p a i r s . Upon c o m p l e t i o n o f t h e f i r s t and s e c o n d b l o c k o f 54 t r i a l s , a One-minute r e s t p e r i o d o c c u r r e d . 41 To m a i n t a i n t h e m o d e l i n g i n f l u e n c e f o r e x p e r i m e n t a l groups d u r i n g t h e SDT s e r i e s , t he model remained a c t i v e t h r o u g h o u t . The model's r o l e d u r i n g t h i s s e r i e s d i f f e r e d s l i g h t l y f r o m t h a t i n the a s c e n d i n g s e r i e s . I n c o n d i t i o n s T and I , t h e model made d i s c r e p a n t r a t i n g s i n t h e a p p r o -p r i a t e d i r e c t i o n on 39 t r i a l s ( r o u g h l y 24% o f a l l t r i a l s ) . I n c o n d i t i o n T, t h e model made d i s c r e p a n t r a t i n g s one s c a l e p o i n t b e l o w t h e s u b j e c t ' s r a t i n g s on t h e s e t r i a l s , w h i l e i n c o n d i t i o n I , t h e model made d i s c r e p a n t r a t i n g s one s c a l e p o i n t h i g h e r . To enhance t h e c r e d i b i l i t y o f t h e model's b e h a v i o u r , she a l s o made d i s c r e p a n t f o r c e d - c h o i c e r a t i n g s on 30 ( r o u g h l y 19% o f ) a l l t r i a l s . D i s c r e p a n t c a t e g o r y s c a l e and b i n a r y - c h o i c e r a t i n g s were i n d e p e n d e n t o f one a n o t h e r . D i s c r e p a n t r a t i n g s o c c u r r e d randomly t h r o u g h o u t t h e S D T . s e r i e s . When t h e model was n o t s p e c i f i c a l l y s i g n a l l e d t o p e r f o r m a . d i s c r e p a n t r a t i n g , she gave r a t i n g s t h a t were i d e n t i c a l t o t h o s e o f "the s u b j e c t . I n circumstances" where g i v i n g a d i s c r e p a n t f o r c e d -c h o i c e r a t i n g was i l l o g i c a l ( e . g . , when the s u b j e c t had g i v e n a r a t i n g o f "3-4" and r a t e d t h e second s t i m u l u s as h i g h e r , w h i c h w o u l d o r d i n a r i l y have c a l l e d f o r the model t o em i t t h e i l l o g i c a l r a t i n g "3-4, f i r s t h i g h e r " ) t h e model gave r a t i n g s t h a t were i d e n t i c a l t o t h o s e o f the s u b j e c t . I n c o n d i t i o n C, t h e model's p r e s e n c e as an a c t i v e c o - p a r t i c i p a n t was b r o u g h t about by t h e e x p e r i m e n t e r i n f o r m i n g s u b j e c t and model t h a t , d u r i n g t he SDT s e r i e s , t he model w o u l d be r e c e i v i n g s h o c k s , b u t , u n l i k e t h e mod e l , s h o u l d w r i t e h e r r a t i n g s on a mimeographed s h e e t r a t h e r t h a n v e r b a l -i z i n g them a l o u d . The e x p e r i m e n t e r t h e n gave t h e model a c l i p b o a r d , s h e e t and p e n c i l and s p e n t some ti m e o s t e n s i b l y i n s t r u c t i n g h e r i n how t o w r i t e h e r r a t i n g s . P r i o r t o i n i t i a t i n g t h e SDT s e r i e s , t h e e x p e r i m e n t e r c a u t i o n e d the model t o r e a d the i n s t r u c t i o n s a t t h e top o f t h e s h e e t c a r e f u l l y and 42 u n d e r s t a n d them t h o r o u g h l y b e f o r e t h e s e r i e s s t a r t e d . I n t e r - p a i r i n t e r v a l s d u r i n g t h e SDT s e r i e s v a r i e d f r o m 10 - 20 s e c , w h i l e the s p a c i n g between s t i m u l i i n each p a i r was r o u g h l y 1 - 2 s e c . When the SDT s e r i e s had been c o m p l e t e d , s u b j e c t and model were e s -c o r t e d t o t h e a d j o i n i n g room where t h e y c o m p l e t e d t h e SSS and the MPQ. When s u b j e c t s had f i n i s h e d c o m p l e t i n g t h e q u e s t i o n n a i r e s , t h e n a t u r e o f the d e c e p t i o n was r e v e a l e d t o them, and th e y were f u l l y d e b r i e f e d as t o the b a c k g r o u n d and p u r p o s e s o f t h e e x p e r i m e n t . The i n t e n t t o use the v i d e o -t a p e s t a k e n o f them i n l a t e r r e s e a r c h was e x p l a i n e d , and they s i g n e d -consent forms i n d i c a t i n g t h a t t h e y were a g r e e a b l e t o t h i s . (The c o n s e n t form em-p l o y e d i s p r e s e n t e d i n A p p e n d i x B.) F o l l o w i n g t h i s , s u b j e c t s were p a i d , and r e q u e s t e d n o t t o t a l k t o anyone i n t h e i r c l a s s e s about t h e e x p e r i m e n t f o r a p e r i o d o f about a month. R e s u l t s 43 S u b j e c t a t t r i t i o n D u r i n g t h e c o u r s e o f t h e s t u d y , 8 o f t h e 44 s u b j e c t s who c o m p l e t e d S e s s i o n 1 i n d i c a t e d t h e i r u n w i l l i n g n e s s t o r e t u r n f o r a second S e s s i o n . Of the 38 s u b j e c t s who r e t u r n e d f o r S e s s i o n 2, 7 t e r m i n a t e d t h e s e s s i o n d u r i n g t h e s i g n a l d e t e c t i o n s e r i e s . Of t h e s e , 5 were i n group I , 1 was i n group T, and 1 was i n group C. A l l were s u b j e c t s who a c c e p t e d c u r r e n t s o f l o w e r i n t e n s i t y d u r i n g S e s s i o n 2 t h a n d u r i n g S e s s i o n 1. .- Y - ' i ! V e r b a l r e p o r t s o f p a i n t h r e s h o l d and p a i n t o l e r a n c e I t was o f c o n c e r n t o e v a l u a t e w h e t h e r t h e g r e a t e r r a t e o f a t t r i t i o n o f s u b j e c t s i n group I d u r i n g S e s s i o n 2 and t h e subsequent r e p l a c e m e n t o f t h e s e s u b j e c t s r e s u l t e d i n a t t r i t i o n o f s u b j e c t s e x h i b i t i n g d i f f e r e n t i n -i t i a l p a i n t h r e s h o l d ( f i r s t r a t i n g o f 10 o r g r e a t e r ) o r p a i n t o l e r a n c e (maximum c u r r e n t a c c e p t e d ) v a l u e s . A c c o r d i n g l y , a n a l y s e s o f v a r i a n c e (ANOVAs) were p e r f o r m e d on p r e t e s t t h r e s h o l d and t o l e r a n c e v a l u e s d u r i n g t h e two a s c e n d i n g s e r i e s o f S e s s i o n 1. The f i r s t p a i r o f a n a l y s e s i n c l u d e d d a t a from a l l s u b j e c t s who c o m p l e t e d t h e 3 a s c e n d i n g s e r i e s o f S e s s i o n 2 ( i . e . , i n c l u d i n g t h o s e who dropped out d u r i n g the SDT s e r i e s ) and i s b a s e d on sample s i z e s o f 11 i n group T, 15 i n group I , and 10 i n group C. The a n a l y s i s p e r f o r m e d on the c u r r e n t i n t e s i t y p r o v o k i n g an i n i t i a l r a t i n g o f 10 o r g r e a t e r ( i . e . , t h r e s h o l d ) r e v e a l e d no s i g n i f i c a n t between group d i f f -e r e n c e s , (2,33) = 0.94, p >.05. The a n a l y s i s on t h e c u r r e n t i n t e n s i t y f o r p a i n t o l e r a n c e r e v e a l e d no s i g n i f i c a n t between g r o u p s , F_ (2,33) = 2.12 p > ,05, o r S e r i e s , F (1,33) = 2.16, p > -.05, e f f e c t s . Thus, t h e r e 44 were no d i f f e r e n c e s between groups on these measures at the end of Session 1 that were s t a t i s t i c a l l y r e l i a b l e . The same analyses were performed excluding the data from those sub-j e c t s who dropped out during the s i g n a l d e t e c t i o n s e r i e s . The thr e s h o l d a n a l y s i s r e s u l t e d i n no s i g n i f i c a n t between-group e f f e c t s , F (2.27) = 1.65, p > .05. The a n a l y s i s of pa i n t o l e r a n c e w i t h dropouts excluded r e s u l t e d i n a between groups e f f e c t that approached, but d i d not a t t a i n , convention-a l l e v e l s of s t a t i s t i c a l r e l i a b i l i t y , F_ (2,27) = 2.79, p_=.08, and no other noteworthy terms. O v e r a l l , t h e r e f o r e , i t was reasonable to conclude that the groups were comparable i n terms of pa i n t h r e s h o l d and p a i n tolerance values p r i o r to undergoing the i n f l u e n c e c o n d i t i o n s o f Session 2. Threshold and tolerance data were examined f u r t h e r i n order to de-termine e f f e c t s of exposure to the s o c i a l i n f l u e n c e c o n d i t i o n s . The pl a n of a n a l y s i s proceeded as f o l l o w s . F i r s t , the data were analyzed i n a 3 (Groups) X 5 (Shock S e r i e s ) ANOVA design w i t h repeated measures on the Ser i e s f a c t o r . F o l l o w i n g t h i s , simple main e f f e c t s were evaluated f o r s t a t i s t i c a l r e l i a b i l i t y . F i n a l l y , a s e r i e s of planned orthogonal compari-sons was conducted w i t h i n each group, across the Se r i e s dimension. Between group comparisons were conducted using Dunnett's t e s t f o r comparing t r e a t e d groups w i t h a c o n t r o l group. Further a p o s t e r i o r i comparisons were con-ducted as necessary using Tukey.'s HSD procedure ( K i r k , 1968). In the o v e r a l l a n a l y s i s , l e v e l s 1 and 2 of the Series v a r i a b l e represented performance during-the ^pretestirig'isession, Tahd>levels- 3ife6 -5 represented performance under the s o c i a l i n f l u e n c e c o n d i t i o n s of Session 2. Data from a l l subjects who completed the ascending s e r i e s of Session 2 were i n c l u d e d . The ANOVA f o r t h r e s h o l d data r e s u l t e d i n s i g n i f i c a n t e f f e c t s f o r the S e r i e s v a r i a b l e , 45 F_, (4,132) = 3.76, p_ <.01, and f o r the S e r i e s X groups i n t e r a c t i o n , F_ (8,132) = 4.61, p_ <.01, F i g u r e l : l p o r t r a y s mean t h r e s h o l d v a l u e s f o r a l l t h r e e groups a c r o s s t h e 5 shock s e r i e s . A n a l y s e s o f s i m p l e e f f e c t s f o r d i f f e r e n c e s between groups a t each l e v e l o f the S e r i e s v a r i a b l e , employ-i n g the p o o l e d e r r o r term s u g g e s t e d by K i r k ( 1 9 6 8 ) , r e v e a l e d no s y s t e m -a t i c between group d i f f e r e n c e s ( a = .05) a t S e r i e s 1 and 2, F_ (2,165) = 1.41 and 0.17, r e s p e c t i v e l y -- whereas s i g n i f i c a n t between group e f f e c t s o c c u r r e d a t a l l s e r i e s d u r i n g t he i n f l u e n c e s e s s i o n , F_ (2,165) = 3.48, 5.14, 5.20 f o r S e r i e s 3 t h r o u g h 5, r e s p e c t i v e l y . F u r t h e r a n a l y s e s on t h e s e s i g n i f i c a n t e f f e c t s were p e r f o r m e d , em-p l o y i n g D u n n e t t ' s t e s t f o r comparisons o f e x p e r i m e n t a l groups w i t h a c o n -t r o l group. R e s u l t s o f t h i s a n a l y s i s showed t h a t s u b j e c t s ^ i n group I d i d n o t d i f f e r f rom c o n t r o l s u b j e c t s i n mean p a i n t h r e s h o l d a t any o f the shock s e r i e s d u r i n g t h e i n f l u e n c e s e s s i o n . S u b j e c t s exposed t o a t o l e r a n t m o d el, however, e x h i b i t e d s i g n i f i c a n t l y , e l e v a t e d mean p a i n t h r e s h o l d v a l u e s r e l a t i v e t o c o n t r o l s u b j e c t 7 s on^shock s e r i e s 4 and,5 (Dunnett's t e s t c r i t i c a l v a l u e = 2.29; d i f f e r e n c e s between group T means and group C means a t s e r i e s 4 and 5 = 2.75 and 2.55, r e s p e c t i v e l y ) . Mean p a i n t h r e s h -o l d v a l u e s f o r s u b j e c t s i n group T a t s e r i e s 4 and 5 were 7.95 mA (S.D. = 4.17) and 7.95 mA (S.D. = 3.97). F o r group C the c o r r e s p o n d i n g v a l u e s were 5.20 mA (S.D. = 1.58) and 5.40 mA (S.D, = 1.26). F u r t h e r p o s t - h o c a n a l y s e s w i t h Tukey's HSD p r o c e d u r e r e v e a l e d t h a t t he s i g n i f i c a n t b e -tween groups e f f e c t d u r i n g s e r i e s 3 o c c u r r e d between groups T and I (Tuke'yj'sHSD c r i t i c a l v a l u e (a = .05) = 2.53; group T group I d i f f e r e n c e = 2.58 mA). Means f o r groups T and I a t t h i s l e v e l were 7.68 mA (S.D. =3.60) and 5.10 (S.D. = 1.93), r e s p e c t i v e l y . P l a n n e d o r t h o g o n a l c o m p a r i s o n s were 46 Figure 1: 1. Mean i n t e n s i t y of current provoking a r a t i n g of "10" (pain threshold) under uninfluenced (Alone) and influenced (With Model) con-diti o n s f o r subjects i n Groups T, C, and I. 12 Alone «/> l O Q) i _ 0 a £ .2 8 c c CD - 4 c CD 1 With Mode l •— — • Tolerants • # Controls r • Intolerants 3 4 Shock Series 47 c o n d u c t e d a l o n g t h e S e r i e s v a r i a b l e a t each l e v e l o f the groups v a r i a b l e . The c r i t i c a l c o n t r a s t examined was t h a t between the f i r s t two ( p r e t e s t ) and t h e r e m a i n i n g t h r e e ( i n f l u e n c e s e s s i o n ) shock s e r i e s . These a n a l y s e s r e v e a l e d a s i g n i f i c a n t p r e t e s t t o i n f l u e n c e s e s s i o n change among s u b j e c t s i n group T o n l y ; j t (132) = 6.51, p_ <.01. P a i n t h r e s h o l d v a l u e s i n c r e a s e d among s u b j e c t s exposed t o a t o l e r a n t model from a mean o f 4.85 mA i n t h e p r e t e s t s e s s i o n (S.D. = 2.09) t o a mean o f 7.86 mA i n t h e i n f l u e n c e s e s s i o n (S.D. = 3.91). A s i m i l a r p i c t u r e emerges i f o n l y t h o s e s u b j e c t s who c o m p l e t e d t h e SDT s e r i e s a r e i n c l u d e d i n t h e a n a l y s i s . The o v e r a l l a n a l y s i s r e s u l t e d i n a s i g n i f i c a n t e f f e c t f o r Shock S e r i e s , F_ (4,108) = 6.02, p_ <.01. S i n c e i t was the S e r i e s X G r o u p s e f f e c t t h a t was o f c r i t i -c a l i n t e r e s t , f u r t h e r a n a l y s e s were c o n d u c t e d on the s i m p l e e f f e c t s con-t r i b u t i n g t o t h i s term. These a n a l y s e s r e v e a l e d s i g n i f i c a n t between-group d i f f e r e n c e s a t l e v e l s 3, 4, and 5 o f the s e r i e s v a r i a b l e , F s ( 2,135) = 4.26 (p_ < . 0 5 ) , 5.52 (p_ < . 0 1 ) , and 5.40 (p_ < .01). The between groups e f f e c t s r e f l e c t e d s i g n i f i c a n t d i f f e r e n c e s between groups T and I a t S e r i e s 3, 4, and 5, and between groups T and C a t S e r i e s 4 and 5 (Tukey's and D u n n e t t ' s t e s t s ) . W i t h i n group a n a l y s e s r e s u l t e d i n s i g n i f i c a n t e f f e c t s o n l y a c r o s s s e r i e s w i t h i n group T, F_ (4,108) = 13.12, p_< .01. The s i g -n i f i c a n t S e r i e s e f f e c t w i t h i n group T r e f l e c t e d an i n c r e a s e i n p a i n t h r e s h o l d between p r e t e s t and i n f l u e n c e s e s s i o n s , t_ (108)= -7.18, p_< .01. P a i n t o l e r a n c e Idata were s u b j e c t e d t o s i m i l a r a n a l y s e s . The o v e r a l l a n a l y s i s i n c l u d i n g a l l s u b j e c t s who c o m p l e t e d t h e a s c e n d i n g s e r i e s o f b o t h s e s s i o n s r e s u l t e d i n s i g n i f i c a n t e f f e c t s f o r Groups, F_(2,33) = 10.98, P_ < .01, S e r i e s , F_(4,132) = 3.65, p_ < .01, and the Groups X S e r i e s i n t e r -a c t i o n , F_(8,132) = 9.34, p_<.01. A n a l y s e s o f s i m p l e e f f e c t s r e v e a l e d 48 s i g n i f i c a n t between-groups d i f f e r e n c e s a t l e v e l s 3, 4, and 5 o f t h e S e r i e s v a r i a b l e , F s ( 2 , 1 6 5 ) = 16.09, 17.12, and 16.33, a l l p_s < .01. Comparisons o f e x p e r i m e n t a l groups w i t h the c o n t r o l group by D u n n e t t ' s t e s t r e v e a l e d t h a t on a l l 3 i n f l u e n c e s e s s i o n s e r i e s , group T d i f f e r e d s i g n i f i c a n t l y ( a = .05) from group C (D u n n e t t ' s c r i t i c a l v a l u e = 2.96; T-C d i f f e r e n c e s = 4.53, 4.53, and 4.40 mA f o r s e r i e s 3, 4 and 5 ) . Group I d i f f e r e d s i g n i f i -c a n t l y f r o m group C on s e r i e s 4 ( C - I d i f f e r e n c e = 2.97 mA) and t h e r e was a t r e n d i n t h e same d i r e c t i o n on t r i a l 5 ( d i f f e r e n c e = 2.92 mA). O r t h o -g o n a l t _ - t e s t s c o n t r a s t i n g p r e t e s t w i t h i n f l u e n c e s e s s i o n t o l e r a n c e v a l u e s f o r a l l 3 groups r e s u l t e d i n s i g n i f i c a n t e f f e c t s w i t h i n group T, _t(132) = 8.69, p_ < .01, and group I , _t(132) = 2.46, p_ < .05 ( b o t h t e s t s 2 - t a i l e d ) . These terms r e f l e c t e d s i g n i f i c a n t i n c r e a s e s i n t o l e r a n c e among group T s u b j e c t s (M s e s s i o n 1 = 9.69 mA, S.D. = 2.39; M s e s s i o n 2 = 14.64 mA, S.D. = 4,19) and d e c r e a s e s among group I s u b j e c t s (M s e s s i o n 1 = 8.48, S.D. = 2.92; M s e s s i o n 2 = 7.28 mA, S.D. = 2.99). The c o n t r o l group r e -mained s t a b l e (M s e s s i o n 1 = 10,43 mA, S.D. = 2 , 7 0 ; M s e s s i o n 2 = 10.15 mA, S.D. = 3.43). These d a t a a r e d e p i c t e d i n F i g u r e 1:2. The r e s u l t s f o r p a i n t o l e r a n c e d i f f e r e d somewhat i f o n l y t h o s e s u b -j e c t s c o m p l e t i n g t h e SDT s e r i e s were i n c l u d e d i n t h e a n a l y s i s . T h i s a n a l y -s i s r e s u l t e d i n the same s i g n i f i c a n t o v e r a l l e f f e c t s : Groups, F_(2,27) = 13.13, p < .01; S e r i e s , F (4,108) = 6.10, p_ < .01; and Groups X S e r i e s , F'.(8.;i08-> = 8.95, p <.01. Si m p l e e f f e c t s a l o n g the S e r i e s v a r i a b l e s u g g e s t e d s i g n i f i c a n t between groups d i f f e r e n c e s a t S e r i e s 3 t h r o u g h 5, Fs(2,135) = 20.02, 17.98, 16.07, a l l p s <.01. A t s e r i e s 3, 4, and 5, Group T e x h i b i t e d s i g n i f i c a n t e l e v a t i o n s i n t o l e r a n c e r e l a t i v e t o group C, a l l d i f f e r e n c e s e x c e e d i n g the c r i t i c a l v a l u e f o r Du n n e t t ' s t e s t ( a=.05) o f 4 9 Figure 1: 2. Mean intensity of current provoking a "terminate" (pain toler-ance rating under uninfluenced (Alone) and influenced (With Model) con-ditions for subjects in Groups T, C, and I. < < Group C 2 3 4 5 SHOCK SERIES 50 2.93. S u b j e c t s i n group 1 e x h i b i t e d r e d u c e d t o l e r a n c e t h a t a p p r o a c h e d , b u t d i d n o t a t t a i n s t a t i s t i c a l s i g n i f i c a n c e . M a i n e f f e c t s o f S e r i e s w i t h -i n groups were o n l y s i g n i f i c a n t f o r group T w h i c h e x h i b i t e d e l e v a t i o n s i n t o l e r a n c e f r o m S e s s i o n 1 (M = 10.00 mA., S.D. = 2.24) t o S e s s i o n 2 (M = 15.55 mA, S.D. = 3 .04, t_ (108) = 9.60, p_ < .01. I n g e n e r a l , the r e s u l t s o f a n a l y s e s o f the a s c e n d i n g s e r i e s may be summarized as f o l l o w s . On p a i n t h r e s h o l d , o n l y s u b j e c t s i n group T ex-h i b i t e d s i g n i f i c a n t changes from S e s s i o n 1 t o S e s s i o n 2. T h i s change a c c o u n t e d f o r s u b j e c t s i n group T e x h i b i t i n g s i g n i f i c a n t e l e v a t i o n s i n p a i n t h r e s h o l d d u r i n g t h e i n f l u e n c e s e s s i o n , r e l a t i v e t o s u b j e c t s i n group C. On p a i n t o l e r a n c e , when d a t a from a l l s u b j e c t s c o m p l e t i n g the a s c e n d i n g s e r i e s o f S e s s i o n 2 were i n c l u d e d , group T e x h i b i t e d a s i g n i f i -c a n t p r e t e s t t o i n f l u e n c e s e s s i o n i n c r e a s e , w h i l e t h o s e i n group I e x h i b i -t e d a s i g n i f i c a n t d e c r e a s e . T h i s change r e s u l t e d i n an o v e r a l l e l e v a t i o n i n p a i n t o l e r a n c e among s u b j e c t s i n group T, r e l a t i v e t o t h o s e i n group C, and a somewhat weaker r e d u c t i o n i n t o l e r a n c e among t h o s e i n group I . When o n l y t h o s e s u b j e c t s who co m p l e t e d t h e SDT s e r i e s were i n c l u d e d i n t h e a n a l y s i s , t h e r e s u l t s were i n t h e same d i r e c t i o n , b u t the e f f e c t s i n group I were n o t s t a t i s t i c a l l y r e l i a b l e . On b o t h p a i n t h r e s h o l d and t o l e r a n c e , s u b j e c t s i n group C m a i n t a i n e d s t a b l e v a l u e s f r o m S e s s i o n 1 t o S e s s i o n 2. SDT DATA; P r e l i m i n a r y a n a l y s e s I n o r d e r t o d e t e r m i n e whether t h e d i f f e r e n t i a l d r o p o u t r a t e among group I s u b j e c t s had i n f l u e n c e d t h e o v e r a l l c u r r e n t i n t e n s i t i e s a d m i n i s t e r -ed d u r i n g the SDT s e r i e s , and t o check on random a s s i g n m e n t , a 3 (g r o u p s ) x 6 ( S t i m u l u s L e v e l s ) ANOVA was p e r f o r m e d on t h e s e v a l u e s . T h i s a n a l y s i s 51 r e v e a l e d t h a t t h e r e were no s i g n i f i c a n t between-group d i f f e r e n c e s i n o v e r -a l l l e v e l s o f c u r r e n t a d m i n i s t e r e d , F_(2,25) = 0.19, p_< .05, n o r was t h e i n t e r a c t i o n between Groups and t h e 6 S t i m u l u s l e v e l s s i g n i f i c a n t , F_(10,140) = 0.85, p>.05. A s i g n i f i c a n t S t i m u l u s l e v e l s e f f e c t , F(5,140) = 220.10, p_<.01, m e r e l y r e f l e c t e d t h e i n c r e a s e i n c u r r e n t i n t e n s i t i e s from low t o h i g h s h o c k s . Thus, the groups were comparable w i t h r e g a r d t o the c u r r e n t i n t e n s i t i e s a d m i n i s t e r e d a t a l l l e v e l s . F o l l o w i n g t h i s , j u d g m e n t a l d a t a were a n a l y z e d a c c o r d i n g t o t h e f r e q u e n c i e s w i t h w h i c h s u b j e c t s employed each c a t e g o r y o f t h e r a t i n g s c a l e a t each o f t h e 6 s t i m u l u s i n t e n s i t i e s employed. The s e s s i o n was d i v i d e d i n t o t h r e e b l o c k s o f 18 t r i a l s a t each s t i m u l u s i n t e n s i t y and t h i s f a c t o r was i n c l u d e d i n t h e 3 (Groups) X 3 ( T r i a l B l o c k s ) X 6 ( C u r r e n t I n t e n s i t i e s ) X 7 ( R a t i n g C a t e g o r i e s ) ANOVA. Of s o l e i n t e r e s t i n t h i s a n a l y s i s was t h e p a t t e r n o f r a t i n g s e x h i b i t e d by t h e 3 groups. T h e r e f o r e , o n l y t h o s e i n t e r -a c t i o n terms i n v o l v i n g Groups and R a t i n g C a t e g o r i e s were examined f o l l o w -i n g t h e o r i g i n a l ANOVA. The o n l y s i g n i f i c a n t i n t e r a c t i o n term i n v o l v i n g b o t h t h e s e v a r i a b l e s was t h e Groups X C u r r e n t I n t e n s i t i e s X R a t i n g C a t e -g o r i e s e f f e c t , F (60,780) = 1.50, p <.01. T h i s e f f e c t i s d e p i c t e d i n F i g u r e 1:3 where t h e d i f f e r e n t i a l p a t t e r n o f c a t e g o r y c h o i c e a c r o s s groups can be o b s e r v e d . A l l 3 groups e x h i b i t e d t he same p a t t e r n o f c a t e g o r y c h o i c e t o t h e l o w e s t p a i r o f s t i m u l i . The modal r e s p o n s e was a t c a t e g o r y 0 ( u n d e t e c t a b l e ) and a l l g r o u p s ' f r e q u e n -c i e s o f c a t e g o r y c h o i c e d e c l i n e d r a p i d l y t h e r e a f t e r . None o f t h e between-group d i f f e r e n c e s a t t h i s p a i r o f s t i m u l u s i n t e n s i t i e s was s i g n i f i c a n t . F o r t h e m i d d l e s t i m u l u s p a i r ( c u r r e n t l e v e l s 3 and 4 ) , a l l groups f a v o u r e d c a t e g o r i e s 1 ( f a i n t s e n s a t i o n ) t o 3 ( v e r y f a i n t p a i n ) . The mode f o r groups T and I was a t c a t e g o r y 1, whereas t h e mode f o r group C was a t c a t e g o r y 2. 52 Figure 1: 3. Mean frequency of choice of each rating scale point at high, medium, and low shock intensities for subjects in Groups T, C, and I. Note: Rating scale point descriptors are Undetectable (0), Faint Sens-ation (1), Pre-Pain Sensation (2), Very Faint Pain (3), Mild Pain (4), Moderate Pain (5) , Strong Pain (6). 52a 0 1 2 3 4 5 6 RATING SCALE CATEGORY 53 F r e q u e n c y o f c h o i c e o f c a t e g o r y 1'was s i g n i f i c a n t l y g r e a t e r among s u b j e c t s i n group T t h a n among t h o s e i n groups 1 and C by Tukey's HSD p r o c e d u r e ( c r i t i c a l v a l u e , a = .05 = 2.52; means: group T = 7.87, group I = 4.83, group C = 4.19). S u b j e c t s i n group C e x h i b i t e d a s i g n i f i c a n t l y g r e a t e r f r e q u e n c y o f c h o i c e o f c a t e g o r y 3 t h a n d i d s u b j e c t s i n group T when j u d g -i n g c u r r e n t s from the m i d d l e s t i m u l u s p a i r (means: group C = 4.30, group T= 1.58). The d i f f e r e n c e between groups C and I a t t h i s c a t e g o r y and p a i r o f s t i m u l u s i n t e n s i t i e s was n o t s i g n i f i c a n t (mean: group I = 2.28). F o r th e h i g h p a i r o f s t i m u l u s i n t e n s i t i e s , group T's modal f r e q u e n c y o f c a t e -g o r y c h o i c e o c c u r r e d a t c a t e g o r y 3 / ( f a i n t - p a i i i ) ,whereas t h o s e f o r groups I and C f e l l a t c a t e g o r i e s fc ( s t r o n g p a i n ) and 5 (moderate p a i n ) , r e s p e c -t i v e l y , group T e x h i b i t e d an e l e v a t e d f r e q u e n c y o f c h o i c e o f c a t e g o r i e s 2 and ^3 a t t h i s p a i r o f i n t e n s i t i e s r e l a t i v e t o groups I and C, w h i c h d i d n o t d i f f e r (means a t c a t e g o r y group T = 4.50, group I = 1.37, group C = 1.52; a t c a t e g o r y 3;: group T = 5.63, group I = 1.37, group C = 1.65). A t c a t e g o r y 4-., group C's mean.,(4.80) was s i g n i f i c a n t l y g r e a t e r t h a n 1 group I's ( 1 . 7 5 ) , and a t c a t e g o r y 5/, group C's mean (7.69) was s i g n i f i c a n t l y g r e a t e r t h a n b o t h group I's (1.78) and group T's ( 1 . 7 5 ) . A t c a t e g o r y .6 , s u b j e c t s i n . g r o u p I e x h i b i t e d an e l e v a t e d mean (6.03) r e l a t i v e t o groups T (0.92) and C (1.50) w h i c h d i d n o t d i f f e r . O v e r a l l t h e n , t h e m a j o r d i f f e r -ences i n f r e q u e n c y o f c a t e g o r y c h o i c e o c c u r r e d a t the m i d d l e and h i g h s t i m u l u s p a i r s . A t b o t h s t i m u l u s i n t e n s i t y l e v e l s , s u b j e c t s i n group T s e l e c t e d r e s p o n s e c a t e g o r i e s i n d i c a t i n g l e s s p a i n t h a n d i d s u b j e c t s i n groups C and I . D i f f e r e n c e s between groups I and C o n l y emerged a t t h e h i g h e s t s t i m u l u s p a i r and t h e r e s p o n s e c a t e g o r y i n d i c a t i v e o f g r e a t e s t p a i n . S u b j e c t s i n group I employed t h i s c a t e g o r y more f r e q u e n t l y i n d e s c r i b i n g t h e i r response' t o t h e h i g h e s t s t i m u l u s p a i r t h a n d i d s u b j e c t s i n groups T„ and C. 54 To summarize, i t was a p p a r e n t from the t r a i n i n g s e r i e s , and from p r e l i m i n a r y a n a l y s e s o f d a t a from t h e SDT s e r i e s t h a t group d i f f e r e n c e s i n p a i n r e p o r t s r e s u l t e d f r o m e x p o s u r e t o t h e v a r i o u s t r e a t m e n t s . The e f f e c t s seemed most s u b s t a n t i a l i n group T. S u b j e c t s i n t h i s group ex-h i b i t e d the most d r a m a t i c changes d u r i n g the a s c e n d i n g s e r i e s , and e x -h i b i t e d a g r e a t e r d i s c r e p a n c y f r o m C o n t r o l s u b j e c t s i n t h e i r s e l e c t i o n o f r a t i n g - s c a l e c a t e g o r i e s t h a n d i d s u b j e c t s i n group I . SDT a n a l y s e s were p e r f o r m e d n e x t i n o r d e r t t o d e t e r m i n e whether between-group d i f f e r e n c e s i n d i s c r i m i n a b i l i t y o r r e s p o n s e - b i a s w o u l d emerge. SDT a n a l y s e s SDT a n a l y s e s were con d u c t e d on d a t a f r o m t h e f o r c e d - c h o i c e p r o -c e d u r e . S i n c e s e n s i t i v i t y i n d i c e s d e r i v e d from f o r c e d - c h o i c e t a s k s a r e l i k e l y t o be a f f e c t e d i f s u b j e c t s e x h i b i t p r e f e r e n c e s f o r i d e n t i f y i n g a g i v e n i n t e r v a l as the one c o n t a i n i n g " s i g n a l " ( M c N i c o l , 1 9 7 2 ) , t h e s e d a t a were f i r s t examined i n o r d e r t o d e t e r m i n e whether such i n t e r v a l b i a s e s o c c u r r e d and v a r i e d s y s t e m a t i c a l l y a c r o s s groups. An i n d e x o f i n t e r v a l b i a s was c a l c u l a t e d f o r e a c h s u b j e c t as the r a t i o o f the number o f i d e n t i -f i c a t i o n s o f i n t e r v a l 2 w i t h " s i g n a l " t o t h e number o f i d e n t i f i c a t i o n s o f i n t e r v a l 1 w i t h " s i g n a l " . T h i s i n d e x has a v a l u e o f 1.00 when no i n t e r v a l b i a s i s p r e s e n t , v a l u e s l e s s t h a n 1 when a p r e f e r e n c e i s e x h i b i t e d f o r t h e f i r s t i n t e r v a l and a v a l u e e x c e e d i n g 1 when a p r e f e r e n c e i s e x h i b i t e d f o r the second i n t e r v a l . S e p a r a t e a n a l y s e s o f v a r i a n c e were p e r f o r m e d on t h e s e d a t a a t each f o r c e d - c h o i c e p a i r ( i . e . , l o w , medium, arid h i g h ) , F o r the l o w , medium, and h i g h f o r c e d - c h o i c e p a i r s , t h e r e was no e v i d e n c e s u g g e s t i n g d i f f e r e n t i a l 55 p r e f e r e n c e f o r one i n t e r v a l a c r o s s g r o u p s , F_s (2,26) = 0.99, 0.37, and 2.64, r e s p e c t i v e l y (p_ >.05). E s t i m a t e s o f d_' c a l c u l a t e d on d a t a f r o m t h e f o r c e d - c h o i c e t a s k were e n t e r e d i n a 3 (Groups) X 3 ( P a i n I n t e n s i t y L e v e l s ) ANOVA d e s i g n . None o f the e f f e c t s i n t h i s a n a l y s i s approached s t a t i s t i c a l s i g n i f i c a n c e . F o r t h e major SDT a n a l y s e s , t h e c o n d i t i o n a l l p r o b a b i l i t i e s o f o c c u r r e n c e o f a p a r t i c u l a r r e s p o n s e c a t e g o r y g i v e n the p r e s e n t a t i o n o f a p a r t i c u l a r s t i m u l u s l e v e l were c a l c u l a t e d . These p r o b a b i l i t i e s were t h e n cumulated from t h e h i g h e s t t o t h e l o w e s t r e s p o n s e c a t e g o r y a t each s t i m u l u s l e v e l . The t a b l e s so d e r i v e d were employed t o e s t i m a t e the SDT p a r a m e t e r s . I n i t i a l l y , v a l u e s o f d-- and L^ between a d j a c e n t s t i m u l u s p a i r s were c a l c u -l a t e d a t a l l p o i n t s o f t h e r a t i n g s c a l e where t h e s e measures were d e f i n e d ( i . e . , where the p r o b a b i l i t y o f a h i t , p ( H i t ) , and the p r o b a b i l i t y o f a f a l s e a l a r m , P ( F A - ; ) , 4 0.00 o r 1.00). F o r d', the mean v a l u e a t each s t i m u l u s p a i r was t h e n c a l c u l a t e d . S i n c e a c t u a l s t i m u l s i n t e n s i t i e s ad-m i n i s t e r e d t o s u b j e c t s were i n d i v i d u a l i z e d , each o f the d e r i v e d mean d_' v a l u e s was e x p r e s s e d as an o v e r a l l d i s c r i m i n a b i l i t y i n d e x ( D I ) : DI = _ , where S„ and S., r e f e r t o t h e v a l u e s o f the h i g h e r and the b 2 - 1 . 1 l l o w e r s t i m u l i o f the p a i r ( c f . C r a i g & Coren, 1975). A t t h e l o w e s t 2 s t i m u l u s i n t e n s i t y p a i r s , t h e p a r a m e t e r s were i n -c a l c u l a b l e f o r 7 (23%) o f s u b j e c t s . C o n s e q u e n t l y , d i f f e r e n c e s i n mean DI were e v a l u a t e d o n l y a c r o s s t h o s e s t i m u l u s i n t e n s i t y p a i r s where complete d a t a were a v a i l a b l e ( p a i r s 3-4 t o 5-6). These d a t a were a n a l y z e d i n a 3 (Groups) X 3 ( S t i m u l u s P a i r s ) f a c t o r i a l d e s i g n . R e s u l t s o f t h i s a n a l y s i s i n d i c a t e d no s i g n i f i c a n t b etween-groups, F(2,27) = 0.65, p_>.05, o r S t i m u l u s I n t e n s i t y , - F (2,54) = 1.16; p_>.05, e f f e c t s . "However, t h e Groups X Stimulus;'-56 P a i r s i n t e r a c t i o n term was s t a t i s t i c a l l y s i g n i f i c a n t , F_(4,54) = 3 86,p_<.01. Mean D i s f o r t h e s e s t i m u l u s p a i r s a r e p r e s e n t e d i n T a b l e 1: 1. Between-group d i f f e r e n c e s w i t h i n each s t i m u l u s i n t e n s i t y p a i r were f u r t h e r e v a l u a t e d by D u n n e t t ' s p r o c e d u r e . T a b l e 1:1 Mean D i s c r i m i n a b i l i t y I n d i c e s a t S t i m u l u s P a i r s 3-4 t o 5-6 f o r T o l e r a n t , I n t o l e r a n t , and C o n t r o l S u b j e c t s S t i m u l u s 3-4 4-5 5-6 P a i r Group T o l e r a n t 1.36 0.77 1 .15 C o n t r o l 0.64 0.81 0.67 I n t o l e r a n t 0.39 1.71 0.84 Note: H i g h e r v a l u e s f o r t h e d i s c r i m i n a b i l i t y i n d e x i n d i c a t e g r e a t e r d i s c r i m i n a b i l i t y . This analysis indicated that DT values for both groups T and I were not significantly different from those for group C at stimulus pairs, 3-4 and 5-6. However, at stimulus pair 4-T'5 group 1 exhibited increased Dl values relative to group C (Dunnett's critical value, (,a=.05) = 0.80; group I -group C difference = .90). Group T's mean DI value did not differ from that for group C at any stimulus pair. Thus, at this stimulus pair, dis-criminability was increased among I subjects relative to those in groups C and T who exhibited comparable levels of discrimination. Values of the likelihood-ratio criterion, L , were examined in order —x to determine whether the social influence conditions were differentially associated with biases toward reporting greater or lesser pain. A variety of different strategies are available for examining bias effect. After Clark (1974) , mean values of were calculated across a l l stimulus levels at the "very faint pain" rating category (L^™ )• This value was then analyzed in a one-way analysis of variance. Results of this analysis re-vealed no significant between-group differences, F_(2,20) = 1.66,p> .05. However, data from 8 subjects (27%) had to be excluded because the para-meter was incalculable at this criterion. A second strategy was to cal-culate the overall mean L value across a l l rating scale categories at a l l —x pairs of stimulus intensities. Again, since many of these parameters were incalculable at the lowest 2 pairs of stimulus intensities, variation in mean L was assessed across stimulus levels 3-4, 4-5, and 5-6. Results of —x the analysis of variance again indicated no significant between-groups, F(2,27) = 0.64, p >.05, or Groups X Stimulus Pairs, F(4,54) = 0.74,p>.05 effects. The effect of stimulus-pair levels on mean L was significant —x F_(2,54) = 3.13, p_ = >.05, and indicated a trend for subjects to adopt 58 more s t r i n g e n t c r i t e r i a f o r r e p o r t i n g p a i n a t s t i m u l u s p a i r 4-5 t h a n a t p a i r s 3-4 and 5-6 (Ms = 1.01, 1.69, and 1.02 f o r l e v e l s 3-4, 4-5, and 5-6, r e s p e c -t i v e l y ) . T h i s t r e n d may s i m p l y be an a r t i f a c t o f t h e f a c t t h a t a t l e v e l 4-5 t h e r e were fewer p o i n t s a t w h i c h e s t i m a t e s o f L were c a l c u l a b l e . Because o f t h e problems p r e s e n t e d by i n c a l c u l a b l e p a r a m e t e r s i n t h e above s t a n d a r d a n a l y s e s , a second s e t o f a n a l y s e s was c o n d u c t e d , e m p l o y i n g n o n p a r a m e t r i c measures o f t h e SDT p a r a m e t e r s . The d i s c r i m i n a b i l i t y o f p a i r s o f s t i m u l u s i n t e n s i t i e s was i n v e s t i g a t e d by e s t i m a t i n g t h e a r e a under the r e c e i v e r - o p e r a t i n g - c h a r a c t e r i s t i c (ROC) c u r v e . I n i n s t a n c e s where o n l y one o r two p o i n t s were a v a i l a b l e f o r p l o t t i n g the p a t h o f the c u r v e , t h e measure P(A) ( M c N i c o l , 1972; P o l l a c k , Norman, & C a l a n t e r , 1964) was employed as the b e s t e s t i m a t e o f the a r e a under the c u r v e . T h i s measure i n v o l v e s p l o t t i n g the p o i n t ( p ( F A ) , p ( H i t ) ) , and p r o j e c t i n g two l i n e s t h r o u g h i t : one from the o r i g i n t h r o u g h the p o i n t and one fr o m the i n t e r s e c t i o n o f p(FA) = 1.0 and p ( H i t ) = 1.0 t h r o u g h t h e e s t i m a t e d p o i n t i n the o p p o s i t e d i r e c t i o n . When o n l y one p a i r o f h i t and f a l s e a l a r m c a t e g o r i e s i s a v a i l a b l e , t h i s p r o c e d u r e w i l l d i v i d e t h e ROC p l o t i n t o 4 s e p a r a t e a r e a s : 2 t r i a n g l e s formed by t h e l i n e s i n t e r s e c t i n g a t the p o i n t c o r r e s p o n d i n g t o the p l o t t e d h i t and f a l s e a l a r m p r o b a b i l i t i e s , an upper and a l o w e r q u a n d r a n g l e . Assuming i s o - s e n s i t i -v i t y a t a l l r e s p o n s e c r i t e r i a , t h e a r e a bounded by t h e l o w e r q u a d r a n g l e (W) r e p r e s e n t s p e r f o r m a n c e t h a t i s worse t h a n t h a t i n d i c a t e d by t h e o b t a i n e d h i t and f a l s e a l a r m p r o b a b i l i t i e s , w h i l e the a r e a bounded by the upper quad-r a n g l e (B) r e p r e s e n t s s u p e r i o r p e r f o r m a n c e . The 2 t r i a n g l e s (U^, U^) de-l i m i t an a r e a o f u n c e r t a i n t y w i t h i n w h i c h t h e s u b j e c t ' s p e r f o r m a n c e must f a l l . P(A) was o b t a i n e d by a d d i n g h a l f o f t h i s a r e a o f u n c e r t a i n t y t o the a r e a r e -p r e s e n t i n g i n f e r i o r p e r f o r m a n c e . The same p r o c e d u r e s were employed when more t h a n one p o i n t was a v a i l a b l e f o r p l o t t i n g the ROC c u r v e . When more t h a n 2 59 p o i n t s a r e a v a i l a b l e , t he a r e a o f u n c e r t a i n t y becomes e x c e e d i n g l y s m a l l , and the v a l u e o f P(A) c l o s e l y a p p r o x i m a t e s t h e v a l u e t h a t w o u l d be o b t a i n e d by d i r e c t l y m e a s u r i n g t h e a r e a under t h e c u r v e , P ( A ) . When 3 o r more p o i n t s were a v a i l a b l e f o r p l o t t i n g the ROC c u r v e , t h i s l a t t e r measure was employed. An i n i t i a l a n a l y s i s was c o n d u c t e d on t h e s e v a l u e s o f P(A) c o r r e c t e d f o r t he d i f f e r e n c e s i n s t i m u l u s i n t e n s i t y upon w h i c h t h e y were ba s e d by t h e f o l l o w i n g f o r m u l a : P(A) s t a n d a r d i z e d = P(A) . S 2 - V The o v e r a l l a n a l y s i s s u g g e s t e d t h a t t h e r e was no s i g n i f i c a n t between-groups e f f e c t , F_(2,27) = 0.18, p_> .10. The Groups x S t i m u l u s P a i r s i n t e r a c t i o n a p p r o a c h e d , b u t d i d n o t a t t a i n c o n v e n t i o n a l l e v e l s o f s t a t i s t i c a l s i g n i f i -c a nce, _F(8,108) = 1.74, p_> .10. I n t e r e s t i n g l y enough, however, the g r e a t e s t d i f f e r e n c e s between means i n the i n t e r a c t i o n t e r m o c c u r r e d a t l e v e l 4-5, t h e same s t i m u l u s p a i r where s i g n i f i c a n t between-group d i f f e r e n c e s emerged when t h e p a r a m e t r i c D l measure was employed. When e v a l u a t e d by Dunnett's t e s t e m p l o y i n g the c r i t i c a l v a l u e a s s o c i a t e d w i t h a o n e - t a i l e d a o f .05, the :. d i f f e r e n c e between groups I and C was s i g n i f i c a n t , w i t h group I s u b j e c t s e x h i b i t i n g enhanced d i s c r i m i n a b i l i t y r e l a t i v e t o group C s u b j e c t s . A n o n p a r a m e t r i c measure o f r e s p o n s e - b i a s — 13 ( M c N i c o l , 1972) — was c a l c u l a t e d f o r each s u b j e c t . T h i s p a r a m e t e r i s an e s t i m a t e o f t h e p o i n t a l o n g the r a t i n g s c a l e where a s u b j e c t i s e q u a l l y d i s p o s e d t o w a r d g i v i n g " s i g n a l " and " n o i s e " r e s p o n s e s . I t i s c a l c u l a t e d by d e t e r m i n i n g the r a t i n g s c a l e p o i n t a t w h i c h the sum o f p(FA) and p ( H i t ) i s e q u a l t o 1.0. I n i n -s t a n c e s where one r a t i n g s c a l e p o i n t i s a s s o c i a t e d w i t h a p(FA) + p ( H i t ) v a l u e e x c e e d i n g 1.0 and an a d j a c e n t s c a l e p o i n t i s a s s o c i a t e d w i t h a p(FA) + p ( H i t ) v a l u e o f l e s s t h a n 1.0, t h e v a l u e o f i s o b t a i n e d by e x t r a p o l a t i o n . 60 The values of ]3 so derived were subjected to analysis of variance with Groups as a between subjects factor, and Stimulus Pairs as a within-subjects factor. This analysis suggested that did not vary systematically as a function of groups, _F(2,27) = 0.67, p_ >.05. 6 1 DISCUSSION The r e s u l t s o f the p r e s e n t s t u d y s u p p o r t and e x t e n d some o f t h e f i n d i n g s o f p r e v i o u s a n a l y s e s o f s o c i a l m o d e l i n g i n f l u e n c e s on p a i n . Data from the a s c e n d i n g shock s e r i e s i n d i c a t e d a s u b s t a n t i a l impact o f e x p o s u r e t o a t o l e r -ant model upon v e r b a l r e p o r t s o f p a i n t h r e s h o l d and p a i n t o l e r a n c e . T h i s f i n d i n g e x a c t l y r e p l i c a t e s the s o l i d l y - e s t a b l i s h e d t o l e r a n t m o d e l i n g e f f e c t and i s o f r e l a t i v e l y m i n o r t h e o r e t i c a l and e m p i r i c a l i n t e r e s t e x c e p t i n s o f a r as i t e s t a b l i s h e s t h a t the e f f e c t i s o b s e r v a b l e even when s u b j e c t s have had p r i o r e x p o s u r e t o the s t i m u l a t i o n . T h i s l a t t e r f i n d i n g c o n f i r m s t h o s e o f C r a i g and Ward (Note 2) who were a b l e t o demonstrate a w i t h i n - s u b j e c t en-hancement o f p a i n t o l e r a n c e when s u b j e c t s were exposed i n an i n i t i a l s e s s i o n t o an i n a c t i v e c o - p a r t i c i p a n t who became a c t i v e and t o l e r a n t i n a second s e s s i o n . These a u t h o r s ' f i n d i n g s were more s u b s t a n t i a l , however, i n t h a t t h e y d e m o n s t r a t e d t h a t an i n i t i a l enhancement o f p a i n t o l e r a n c e r e s u l t i n g f rom e x p o s u r e t o a t o l e r a n t model was s u b s e q u e n t l y m a i n t a i n e d when t h e a c t i v e m o d e l i n g i n f l u e n c e was removed. Taken t o g e t h e r , t h e s e f i n d i n g s a r e t h e o r e t i c a l l y i n t e r e s t i n g i n t h a t they demonstrate t h e p l a s t i c i t y o f p a i n b e h a v i o u r s i n r e s p o n s e t o v a r i a t i o n s i n s o c i a l c o n d i t i o n s . F u r t h e r , t h e y c o n f i r m t h a t t h e m a n i p u l a t e d v a r i a b l e was p o w e r f u l enough t o provoke a l t e r a t i o n s i n p a i n r e s p o n s e s i n s p i t e o f p r i o r e x p o s u r e t o the s t i m u l a t i o n . T h i s f i n d i n g r e p r e s e n t s s o l i d e v i d e n c e t h a t p a i n b e h a v i o u r s a r e s e n s i t i v e l y r e s p o n s i v e t o and s u b s t a n t i a l l y c o n t r o l l e d by s o c i a l v a r i a b l e s . The d a t a from s u b j e c t s i n the i n t o l e r a n t group was s u f f i c i e n t l y u n u s u a l t o w a r r a n t s e p a r a t e c o n s i d e r a t i o n . The r e s u l t s from a n a l y s e s e m p l o y i n g a l l s u b j e c t s who c o m p l e t e d t h e a s c e n d i n g s e r i e s o f s e s s i o n 2 i n d i c a t e d t h a t e x-p o s u r e t o an i n t o l e r a n t model had no e f f e c t upon p a i n t h r e s h o l d , b u t p r o -62 duced a s i g n i f i c a n t r e d u c t i o n i n c u r r e n t l e v e l s a s s o c i a t e d w i t h a p a i n t o l e r a n c e r a t i n g . However, i f o n l y t h e d a t a from s u b j e c t s who c o m p l e t e d the SDT s e r i e s were i n c l u d e d i n the a n a l y s i s , n e i t h e r p a i n t h r e s h o l d n o r p a i n t o l e r a n c e l e v e l s d i f f e r e d from those o b s e r v e d d u r i n g b a s e l i n e c o n d i -t i o n s o r from t h o s e o b s e r v e d i n t h e c o n t r o l group. T h i s i n c o n s i s t e n c y be-tween the two a n a l y s e s s u g g e s t s t h a t the SDT s e r i e s was e n t i r e l y t o o s t r e s s -f u l f o r t h o s e s u b j e c t s e x h i b i t i n g maximal i n f l u e n c e as a f u n c t i o n o f e x p o s u r e t o the i n t o l e r a n t model. I t seems l i k e l y t h a t the outcome o f the l a r g e r a n a l y s i s r e p r e s e n t s a more a c c u r a t e c h a r a c t e r i z a t i o n o f the e f f e c t s o f i n t o l e r a n t m o d e l i n g . C e r t a i n l y , the d i f f e r e n t i a l s u b j e c t a t t r i t i o n r a t e i n group I s u g g e s t s t h a t the o v e r a l l e f f e c t o f e x p o s u r e t o an i n t o l e r a n t model made s u b j e c t s e s p e c i a l l y i n t o l e r a n t o f the s t i m u l a t i o n . W i t h r e g a r d t o th o s e s u b j e c t s i n group I who c o m p l e t e d t h e SDT s e r i e s , o t h e r d a t a s u g g e s t • t h a t t h e s e s u b j e c t s , t o o , e x h i b i t e d g r e a t e r i n t o l e r a n c e f o r the shocks t h a n d i d s u b j e c t s i n the o t h e r groups. The f i n d i n g s from t h e a n a l y s i s o f f r e q u e n c i e s o f c a t e g o r y c h o i c e ( F i g u r e 1:3) show t h a t s u b j e c t s i n group I more f r e q u e n t l y s e l e c t e d c a t e g o r y r a t i n g s f r o m t h e upper end o f t h e s c a l e when d e s c r i b i n g t h e i r r e a c t i o n s t o t h e h i g h e r i n t e n s i t y s h o c k s . These d a t a , t h e n , s u p p o r t the c o n c l u s i o n t h a t e x p o s u r e t o an i n t o l e r a n t model d i d , i n f a c t , make s u b j e c t s more i n t o l e r a n t o f t h e s t i m u l a t i o n . The f a c t t h a t s u b j e c t s i n group I d i d n o t d i f f e r f rom c o n t r o l s u b j e c t s i n p a i n t h r e s h o l d l e v e l s was i n t e r e s t i n g , p a r t i c u l a r l y s i n c e e a r l i e r s t u d i e s had found r e d u c t i o n s i n p a i n t h r e s h o l d as a consequence o f e x p o s u r e t o an i n t o l e r a n t model ( C r a i g & B e s t , 1977; C r a i g , B e s t , & Ward; C r a i g & Coren , 19 75; C r a i g & N i e d e r m a y e r , 1974; C r a i g & W e i s s , 19 71). I n o r d e r t o d e t e r m i n e whether the f a i l u r e t o o b s e r v e a d i f f e r e n c e i n p a i n t h r e s h o l d may have been a consequence o f h a v i n g t o r e c r u i t new s u b j e c t s i n o r d e r t o r e -63 p l a c e t h o s e who dropped o u t d u r i n g the SDT s e r i e s , the o v e r a l l ANOVA on p a i n t h r e s h o l d v a l u e s was r e - c o n d u c t e d , e m p l o y i n g o n l y t h e d a t a from t h e f i r s t 10 s u b j e c t s a s s i g n e d t o group I . T h i s a n a l y s i s r e v e a l e d t h a t p a i n t h r e s -h o l d v a l u e s s t i l l d i d n o t d i f f e r between groups I and C. I t must be p o i n t e d out t h a t the f i n d i n g o f a s i g n i f i c a n t d i f f e r e n c e i n t h i s r e - a n a l y s i s w o u l d have p r o v i d e d s u p p o r t f o r t h e p r o p o s e d a l t e r n a t i v e e x p l a n a t i o n ; however, the f i n d i n g o f no d i f f e r e n c e s c a n n o t be t a k e n as s u p p o r t i v e o r n o n - s u p p o r t t i v e . Comparison o f i n f l u e n c e s e s s i o n p a i n t h r e s h o l d v a l u e s f o r the 3 groups i n t h e p r e s e n t s t u d y w i t h t h o s e r e p o r t e d i n t h e p r e v i o u s s t u d i e s e m p l o y i n g t o l e r a n t , i n t o l e r a n t , and c o n t r o l groups r e v e a l e d t h a t t h e means f o r groups T and C f e l l w i t h i n the midrange o f the v a l u e s r e p o r t e d i n p r e v i o u s s t u d i e s . However, the mean f o r group I (5.00 mA) was s l i g h t l y h i g h e r t h a n the h i g h e s t mean r e p o r t e d f o r an i n t o l e r a n t group i n p r e v i o u s s t u d i e s (4.20 mA; C r a i g , B e s t , & Ward, 1975). I n t e r e s t i n g l y , i n a l l b u t one o f t h e p r e v i o u s s t u d i e s i n c o r p o r a t i n g a l l 3 g r o u p s , d i f f e r e n c e s i n c u r r e n t i n t e n s i t i e s p r o v o k i n g a p a i n t h r e s h o l d r a t i n g have been s u b s t a n t i a l l y g r e a t e r between t o l e r a n t and c o n t r o l t h a n between c o n t r o l and i n t o l e r a n t groups. Data t o be p r e s e n t e d i n t h e t h i r d e x p e r i m e n t i n t h i s s e r i e s s u g g e s t an e x p l a n a t i o n f o r t h i s o u t -come, and f u r t h e r d i s c u s s i o n o f i t w i l l be p o s t p o n e d u n t i l t h e g e n e r a l d i s -c u s s i o n . The a n a l y s i s o f c u r r e n t i n t e n s i t i e s a d m i n i s t e r e d d u r i n g the SDT s e r i e s c o n f i r m e d t h a t t h e r e were no d i f f e r e n c e s i n o v e r a l l l e v e l s o f c u r r e n t a d m i n i s t e r e d t o t h e 3 g roups. Thus, c u r r e n t i n t e n s i t i e s were n o t confounded w i t h groups and t h e r e f o r e , c r i t i c i s m s a p p l i e d t o p r e v i o u s SDT s t u d i e s o f m o d e l i n g i n f l u e n c e s do n o t a p p l y t o t h e p r e s e n t s t u d y . R e s u l t s o f the a n a l y s i s o f f r e q u e n c i e s of c a t e g o r y c h o i c e i n d i c a t e d t h a t the 3 groups were, 6 4 i n f a c t , d i f f e r e n t i a b l e i n terms o f t h e i r r e s p o n s e d i s t r i b u t i o n s , p a r t i -c u l a r l y a t the moderate and h i g h shock i n t e n s i t i e s . Thus, t h e e f f e c t s o f t h e m o d e l i n g i n f l u e n c e were m a i n t a i n e d d u r i n g the SDT s e r i e s . As can be seen i n F i g u r e 1:3, t h e e f f e c t s o f m o d e l i n g were c o n s i s t e n t w i t h t h o s e o b s e r v e d d u r i n g t h e a s c e n d i n g s e r i e s , w i t h s u b j e c t s i n group T l e s s f r e -q u e n t l y e m p l o y i n g r e s p o n s e c a t e g o r i e s i n d i c a t i v e o f g r e a t e r p a i n , and sub-j e c t s i n group I more f r e q u e n t l y e m p l o y i n g c a t e g o r i e s i n d i c a t i v e o f g r e a t e r p a i n . A n a l y s i s o f d a t a from the f o r c e d - c h o i c e SDT t a s k i n d i c a t e d t h a t t h e r e were no between-group d i f f e r e n c e s i n the d i s c r i m i n a b i l i t y o f p a i r s o f c u r r e n t s t h a t d i f f e r e d by a s t a n d a r d 0.25 mA a t l o w , medium, and h i g h s t i m u l u s i n t e n s i t y l e v e l s . The f i n d i n g s b a s e d on t h i s f o r c e d - c h o i c e t a s k measure o f d i s c r i m i n a t i o n p a r a l l e l e d t h o s e b a s e d on s t a n d a r d p a r a m e t r i c p r o -c e d u r e s (d.') and t h o s e b a s e d on n o n p a r a m e t r i c p r o c e d u r e s ( P ( A ) ) a t t h e same s t i m u l u s i n t e n s i t i e s . C l a r k and D i l l o n (1973) and C l a r k and Mehl (1973) s u g g e s t e d t h a t f o r c e d - c h o i c e t a s k s p r o v i d e more a c c u r a t e and r e l i a b l e d a t a i n p a i n s t u d i e s t h a n do r a t i n g - s c a l e t a s k s . S i n c e t h e outcome o f t h e f o r c e d -c h o i c e a n a l y s i s was s i m i l a r t o t h e outcome o f a n a l y s e s o f d a t a d e r i v e d from the r a t i n g - s c a l e t a s k a t the same s t i m u l u s i n t e n s i t i e s , i t w o u l d seem r e a s o n -a b l e t o c o n c l u d e t h a t i n t e r p r e t a t i o n o f t h e r a t i n g - s c a l e d a t a does n o t p r e -s e n t p a r t i c u l a r d i f f i c u l t i e s as a r e s u l t o f i n f e r i o r measurement. Of f u r t h e r i n t e r e s t i n the a n a l y s i s o f d a t a from t h e f o r c e d - c h o i c e t a s k was t h e f a c t t h a t the d i s c r i m i n a b i l i t y o f p a i r s o f s t i m u l i a t l o w , medium, and h i g h i n t e n s i t i e s d i d n o t d i f f e r . T h i s outcome i s i n c o n s i s t e n t w i t h what w o u l d be p r e d i c t e d on t h e b a s i s o f Weber's law. As m entioned p r e v i o u s l y , SDT s t u d i e s o f m o d e l i n g i n f l u e n c e s on p a i n have been c r i t i c i z e d on the grounds t h a t c u r r e n t i n t e n s i t i e s a d m i n i s t e r e d were confounded w i t h g r o u p s , and t h e 65 outcome o f t h e s t u d i e s c o u l d be f u l l y a c c o u n t e d f o r on t h e b a s i s o f Weber's law. S i n c e t h e d i s c r i m i n a b i l i t y o f s t i m u l u s p a i r s d i d n o t v a r y i n v e r s e l y w i t h o v e r a l l s t i m u l u s i n t e n s i t y i n t h e p r e s e n t s t u d y , t h i s c r i t i c i s m o f p r e v i o u s SDT a n a l y s e s o f m o d e l i n g i n f l u e n c e s on p a i n w o u l d seem t o be i n -a p p r o p r i a t e . The outcomes o f SDT a n a l y s e s o f t h e r a t i n g - s c a l e t a s k l e n t f u r t h e r s u p p o r t t o the h y p o t h e s i s t h a t the m o d e l i n g i n f l u e n c e p r o c e d u r e s a r e c a p a b l e o f p r o d u c i n g a l t e r a t i o n s i n s e n s o r y s e n s i t i v i t y t o n o x i o u s s t i m u l a t i o n . The a n a l y s i s o f d i s c r i m i n a b i l i t y i n d i c e s b a s e d on the p a r a m e t r i c measure, d/., i n d i c a t e d t h a t s u b j e c t s i n group I e x h i b i t e d enhanced d i s c r i m i n a t i o n when j u d g i n g t h e h i g h e s t o f t h e s t i m u l i s e l e c t e d from j u s t below t h e i r p r e t e s t p a i n t h r e s h o l d and t h e l o w e s t o f the s t i m u l i s e l e c t e d from c l e a r l y p a i n f u l l e v e l s . S i n c e i t was u n c l e a r w h e t h e r d a t a upon w h i c h c a l c u l a t i o n o f d.' was b a s e d met the s t r o n g G a u s s i a n a s s u m p t i o n s u n d e r l y i n g p a r a m e t r i c p r o c e -d u r e s , comparable a n a l y s e s were c o n d u c t e d on the n o n p a r a m e t r i c measure e s t i m a t i n g t h e a r e a under t h e ROC c u r v e . T h i s a n a l y s i s r e s u l t e d i n a s i m i l a r outcome; s u b j e c t s i n group I e x h i b i t e d enhanced d i s c r i m i n a t i o n o f the same shock p a i r s as i n t h e p a r a m e t r i c p r o c e d u r e r e l a t i v e t o s u b j e c t s i n group C. The f a c t t h a t t h i s f i n d i n g was b a s e d on a o n e - t a i l e d t e s t o f s i g n i f i c a n c e may p r e s e n t some d i f f i c u l t i e s i n f u l l y a c c e p t i n g i t ; however, t h e h y p o t h e s i s b e i n g t e s t e d was d i r e c t i o n a l , and t h e t e s t employed ( D u n n e t t ' s ) was more c o n s e r v a t i v e t h a n the o n e - t a i l e d o r t h o g o n a l _ t - t e s t s employed by C r a i g and Ward (Note 2 ) . T h i s f i n d i n g c l o s e l y r e p l i c a t e s t h a t o f C r a i g and Coren (1975) who ob-s e r v e d an enhancement o f d i s c r i m i n a b i l i t y a t c u r r e n t l e v e l s s l i g h t l y b e l o w p a i n t h r e s h o l d among s u b j e c t s exposed t o an i n t o l e r a n t model. 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 e x t e n d t h e f i n d i n g o f C r a i g and Coren i n t h a t enhanced d i s c r i m i n a b i l i t y o c c u r r e d a t c l e a r l y n o x i o u s s t i m u l u s i n t e n s i t i e s . 6 6 I n none o f t h e p r e v i o u s SDT s t u d i e s of m o d e l i n g i n f l u e n c e s on p a i n has t h e r e been a d e m o n s t r a b l e e f f e c t upon r e s p o n s e - b i a s . I n t h e p r e s e n t s t u d y , no between-group d i f f e r e n c e s were o b t a i n e d w i t h t h e p a r a m e t r i c measure, L^, i n terms o f the mean o f b i a s e x t i m a t e s c a l c u l a t e d a t a l l c r i t e r i a and s t i m u l u s p a i r s , o r a t t h e c r i t e r i o n f o r v e r y f a i n t p a i n . S i m i l a r l y , when th e n o n p a r a m e t r i c measure .B was employed, no between group d i f f e r e n c e s were o b s e r v e d . However, a l t e r n a t i v e e v i d e n c e i s c o n s i s t e n t w i t h a p r o p o s e d b i a s a g a i n s t r e p o r t i n g p a i n i n group T. O b s e r v a t i o n o f F i g u r e 1:3 r e v e a l s t h a t a t s t i m u l u s l e v e l s o f moderate and h i g h i n t e n s i t y , s u b j e c t s i n group T tended to d i s t r i b u t e t h e i r r e s p o n s e s more f r e q u e n t l y toward the end of t h e r a t i n g s c a l e i n d i c a t i n g m i n i m a l d i s c o m f o r t t h a n d i d s u b j e c t s i n t h e o t h e r g r o u p s . The l a c k o f f i n d i n g s w i t h r e g a r d t o d i s c r i m i n a b i l i t y i n group T i s p r o b l e m a t i c i n t h e l i g h t o f p r e v i o u s r e p o r t s t h a t t o l e r a n t m o d e l i n g i s a s s o c i a t e d w i t h r e d u c e d d i s c r i m i n a b i l i t y ( C r a i g & P r k a c h i n , 1978; C r a i g & Ward, Note 2 ) . A c o n s i d e r a t i o n o f m e t h o d o l -o g i c a l d i f f e r e n c e s among th e s t u d i e s s u g g e s t s some p o s s i b l e r e s o l u t i o n s o f t h i s p aradox. I n the p r e s e n t s t u d y , s t i m u l u s i n t e n s i t i e s p r e s e n t e d d u r i n g t h e SDT s e r i e s were s e l e c t e d from 3 l e v e l s based on s u b j e c t s ' p e r f o r m a n c e under u n i n f l u e n c e d c o n d i t i o n s . I n t h e s t u d y by C r a i g and P r k a c h i n , 5 s t a n d a r d s t i m u l u s i n t e n s i t i e s , d i f f e r i n g by 1.0 mA were p r e s e n t e d to a l l s u b j e c t s . I n t h e s t u d y o f C r a i g and Ward, 10 s t i m u l u s i n t e n s i t i e s were p r e s e n t e d i n t h e SDT s e r i e s . The i n t e n s i t y o f t h e maximum s t i m u l u s p r e -s e n t e d t o each s u b j e c t was 80% o f the mean t e r m i n a l c u r r e n t a c c e p t e d d u r i n g the p r e c e d i n g a s c e n d i n g s e r i e s , and t h e o t h e r 9 s t i m u l i d i f f e r e d i n e q u a l p r o p o r t i o n s ( 8 % o f t h i s maximum c u r r e n t ) . F o r the v a s t m a j o r i t y o f s u b j e c t s , t h i s w o u l d have meant t h a t a d j a c e n t s t i m u l u s p a i r s d i f f e r e d by 1.0 mA o r l e s s . I n the p r e s e n t s t u d y , i t was n o t u n u s u a l f o r d i f f e r e n c e s between s t i m u l i t o be g r e a t e r t h a n 2.0 mA. I f , f o r some r e a -s o n , r e d u c t i o n s i n d i s c r i m i n a b i l i t y r e s u l t i n g from e x p o s u r e t o a t o l e r a n t model o n l y o c c u r between s t i m u l i d i f f e r i n g by l e s s than the modal i n t e n s i t y d i f f e r e n c e employed i n the p r e s e n t s t u d y , o p p o r t u n i t y t o o b s e r v e a d i f f e r -ence w o u l d have been m i s s e d . A l s o , s i n c e the s t i m u l i i n the p r e s e n t s t u d y were s e l e c t e d from r e l a t i v e l y d i s c r e t e p o i n t s , the s a m p l i n g o f r e s p o n s e s a t v a r i o u s p o i n t s o f the p a i n i n t e n s i t y c o n t i n u u m may have been l e s s ade-q u a t e th a n i n p r e v i o u s s t u d i e s . I f d i s c r i m i n a b i l i t y d i f f e r e n c e s as a f u n c t i o n o f t o l e r a n t m o d e l i n g o n l y o c c u r a t s p e c i f i c p o i n t s a l o n g t h i s c ontinuum, t h o s e p o i n t s may have been m i s s e d i n t h e p r e s e n t s t u d y . Cer-t a i n l y , t h e r e i s p r e c e d e n t f o r o b s e r v i n g s u c h a phenomenon i n SDT p a i n r e -s e a r c h . I n the p r e s e n t s t u d y , d i f f e r e n c e s o n l y emerged i n the i n t o l e r a n t group between one s p e c i f i c p a i r o f s t i m u l i . Chapman, Murphy, and B u t l e r ( 1 9 7 3 ) , i n a s t u d y o f a n a l g e s i c e f f e c t s o f n i t r o u s o x i d e were o n l y a b l e t o demonstrate d i s c r i m i n a b i l i t y r e d u c t i o n s when d_' was c a l c u l a t e d between low, medium, ,and h i g h s t i m u l u s i n t e n s i t i e s and a b l a n k s t i m u l u s . Chapman, G e h r i g , and W i l s o n ( 1 9 7 5 ) , i n a s t u d y c omparing a n a l g e s i c e f f e c t s o f a c u -p u n c t u r e and n i t r o u s o x i d e , a r g u e d from t h e i r f i n d i n g s t h a t , u n l i k e a c u -p u n c t u r e , n i t r o u s o x i d e o n l y r e d u c e d _d' a t v e r y low s t i m u l u s i n t e n s i t i e s . L l o y d and Wagner (1976) r e p o r t e d t h a t a c u p u n c t u r e r e d u c e d d.' o n l y between a b l a n k and v e r y weak s t i m u l u s . An a l t e r n a t i v e e x p l a n a t i o n f o r the i n c o n s i s t e n c y between the p r e s e n t s t u d y and e a r l i e r s t u d i e s t h a t r e p o r t e d p o s i t i v e f i n d i n g s w i t h r e g a r d t o the 68 i n f l u e n c e o f t o l e r a n t m o d e l i n g on d i s c r i m i n a b i l i t y d e r i v e s from the f a c t t h a t c o n s i d e r a b l y more p r e s e n t a t i o n s o f each s t i m u l u s i n t e n s i t y were employed i n the p r e s e n t s t u d y . SDT t a s k s t y p i c a l l y employ v e r y l a r g e numbers o f t r i a l s . I t has been a r g u e d t h a t i n SDT p a i n s t u d i e s where few s t i m u l u s p r e s e n t a t i o n s a r e employed, s u b j e c t s r e s p o n d u n r e l i a b l y ( R o l l m a n , 1977; b u t see Chapman, 1977). The i m p l i c a t i o n i s t h a t when s u b j e c t s ' r a t i n g s do n o t a t t a i n an adequate degree o f r e l i a b i l i t y , s p u r i o u s f i n d i n g s may r e s u l t . A l s o , any c o n d i t i o n t h a t r e d u c e s r e l i a b i l i t y may compound the problem. S i n c e r a t i n g r e l i a b i l i t y i s p r o p o r t i o n a l t o t h e number o f s t i m u l u s p r e s e n t a t i o n s employed, the p r e s e n t s t u d y was l e s s s u b j e c t t o t h i s p r o b l e m t h a n were t h e p r e v i o u s s t u d i e s . However, s i m p l e r a t i n g u n r e l i a b i l i t y c annot a c c o u n t f o r p r e v i o u s t o l e r a n t m o d e l i n g e f f e c t s , u n l e s s i t i s p o s i t e d t h a t e x p o s u r e t o a t o l e r a n t model p r o d u c e d d i f f e r e n t i a l l y g r e a t e r u n r e l i a b i l i t y . I f t h e p r e s e n c e o f a t o l e r a n t model p r o d u c e d p a r t i c u l a r l y u n s t a b l e r e s p o n d i n g , a s p u r i o u s d i f f e r -ence c o u l d have r e s u l t e d . I f the s t u d i e s r e p o r t i n g p o s i t i v e f i n d i n g s had employed groups exposed t o an i n t o l e r a n t model, i t w o u l d be p o s s i b l e t o e v a l u a t e t h i s a l t e r n a t i v e , - s i n c e an i n t o l e r a n t model w o u l d l i k e l y have p r o -duced e q u a l l y u n s t a b l e r a t i n g s , b u t d i s c r i m i n a b i l i t y s h o u l d have i n c r e a s e d . A f i n a l p o i n t i s i n o r d e r c o n c e r n i n g t h e p a r a d i g m employed I n the p r e -s e n t s t u d y . Recent r e v i e w s o f a p p l i c a t i o n s o f SDT t o p a i n r e s e a r c h have p o i n t e d o u t t h a t i n t h e absence o f i n c l u s i o n o f a b l a n k s t i m u l u s , n o t h i n g can be c o n c l u d e d about t h e a b s o l u t e s e n s i t i v i t y o f s u b j e c t s t o t h e s t i m u l i p r e s e n t e d i n p a i n s t u d i e s ( L l o y d & A p p e l , 1976; R o l l m a n , 1977). There i s , however, some c o n f u s i o n r e g a r d i n g what i s meant by " b l a n k s t i m u l u s " . As H a l l (1977)has s t a t e d , t h e term may r e f e r t o " z e r o i n t e n s i t y " on the c o n t i n u u m o f n o x i o u s e x p e r i e n c e , o r i t may r e f e r t o " z e r o s t i m u l u s e n e rgy". The l a t t e r case r a i s e s the i n t e r e s t i n g p o s s i b i l i t y t h a t some s t i m u l i may 69 be c a p a b l e o f p r o v o k i n g e v e n t s on the continuum o f n o x i o u s e x p e r i e n c e t h a t t a k e on n e g a t i v e v a l u e s . I f by " b l a n k s t i m u l u s " i s meant " z e r o s t i m u l u s e n e r g y " , t h e n the measures i n the p r e s e n t s t u d y r e f l e c t r e l a t i v e s e n s i t i v i t y s i n c e no such s t i m u l u s was p r e s e n t e d . I t i s u n c l e a r t h a t i n c l u s i o n o f a z e r o energy s t i m u l u s w o u l d have p r o v i d e d more i n f o r m a t i o n , s i n c e , i n a r e c e n t SDT s t u d y i n t h i s l a b o r a t o r y t h a t d i d employ a b l a n k , s u b j e c t s e x h i b i t e d no c o n f u s i o n I n t h e i r r a t i n g s . A t any r a t e , even i f t h e measures r e p o r t e d i n the p r e s e n t s t u d y do n o t r e f l e c t a b s o l u t e s e n s i t i v i t y , the c o n c l u s i o n t h a t e x p o s u r e t o an i n t o l e r a n t model f u n d a m e n t a l l y a l t e r s s e n s o r y - d i s c r i m i n a t i v e a s p e c t s o f s u b j e c t s ' r e s p o n s e t o n o x i o u s l e v e l s o f s t i m u l a t i o n need not be a l t e r e d . 70 E x p e r i m e n t 2. A s e n s o r y - d e c i s i o n t h e o r y a n a l y s i s o f s o c i a l m o d e l i n g i n f l u e n c e s on n o n v o c a l p a i n e x p r e s s i o n s . The dependent v a r i a b l e i n most s t u d i e s o f p a i n i n humans i s most o f t e n t h e s u b j e c t ' s v e r b a l r e p o r t (Agnew & Merskey, 1976; C r o c k e t t , P r k a c h i n , & C r a i g , 1977; Hardy, W o l f f , & G o o d e l l , 1952; H i l g a r d , 1969). F o r many p u r p o s e s , s u c h measures a r e s e n s i t i v e , r e l i a b l e , and d i s c r i m i n a t i n g ( C r a i g & N i e d e r m a y e r , 1974; H i l g a r d , 1969). D a t a from t h e s e methods a r e o r d i n a r i l y used t o make i n f e r e n c e s w i t h r e g a r d t o t h e i n t e r n a l e x p e r i e n c e o f t h e s u b j e c t . M a g n itude e s t i m a t i o n p r o c e d u r e s , f o r example, a r e t a k e n t o p r o v i d e i n f o r m a t i o n r e g a r d i n g t h e r a t e o f growth o f n o x i o u s s e n s a t i o n a ; SDT p r o c e d u r e s p r o v i d e e v i d e n c e on s e n s o r y s e n s i t i v i t y and t e s t - t a k i n g s e t . Such d a t a a r e o f o b v i o u s i m p o r t a n c e i n a s s e s s i n g t h e e f f e c t s o f s o c i a l i n f l u e n c e p r o c e d u r e s . However, t h e i n f o r m a t i o n t h a t t h e y and o t h e r measures p r o v i d e i s n o t i n t e r c h a n g e a b l e , and d i f f e r e n t i n d i c e s can e x h i b i t u n c o r r e l a t e d v a r i a t i o n s ( C r a i g & P r k a c h i n , 1978). G i v e n t h e m u l t i d i m e n s i o n a l n a t u r e o f p a i n , a v a r i e t y o f dependent measures i s r e q u i r e d i n o r d e r t o a d e q u a t e l y map t h e e f f e c t s o f s o c i a l i n f l u e n c e p r o c e d u r e s . L a b o r a t o r y s t u d i e s o f s o c i a l i n f l u e n c e s on p a i n a r e d e s i g n e d t o c l a r i f y p r o c e s s e s t hought t o be o p e r a t i v e i n t h e n a t u r a l e n v i r o n -ment. I n t h e n a t u r a l s e t t i n g , o v e r t e x p r e s s i v e b e h a v i o u r i s of 71 c r i t i c a l i m p o r t a n c e s i n c e i t p r o v i d e s a b a s i s f o r d i f f e r e n t i a l r e s p o n s e s on t h e p a r t o f members o f t h e s o c i a l m i l i e u . W h i l e p r e v i o u s s t u d i e s i n v e s t i g a t i n g s o c i a l m o d e l i n g i n f l u e n c e s on p a i n have i n d i c a t e d t h a t such p r o c e d u r e s can have a s u b s t a n t i a l impact on p s y c h o p h y s i c a l measures t h o u g h t t o r e f l e c t s u b j e c t i v e e x p e r i e n c e , e v i d e n c e t h a t the p r o c e d u r e s a l t e r o v e r t , n o n v o c a l e x p r e s s i v e b e h a v i o u r w o u l d p r o v i d e a p o w e r f u l d e m o n s t r a t i o n o f t h e i m p o r t a n c e and e x t e r n a l v a l i d i t y o f t h e f i n d i n g s from s u c h r e s e a r c h . O b s e r v e r s employ n o n v o c a l e x p r e s s i o n s as s u p p l e m e n t a r y , o r sometimes f u n d a m e n t a l s o u r c e s o f i n f o r m a t i o n r e g a r d i n g t h e i n t e r n a l s t a t e , o r o t h e r c o n d i t i o n s c o n t r o l l i n g t h e o b s e r v e d i n d i v i d u a l ' s b e h a v i o u r ( F o r d y c e , 1978b; K r a u t , 1978; S t e r n b a c h , 1974). G r i m a c e s , o t h e r s i g n s o f d i s t r e s s , guarded p o s t u r e and t h e l i k e a r e c r i t i c a l cues f o r t h e d i a g n o s t i c i a n e v a l u a t i n g t h e s e v e r i t y o f a p a i n p r o b l e m , and t h e n o n p r o f e s s i o n a l r e s p o n d i n g t o e v i d e n c e o f p a i n . A s u b s t a n -t i a l l i t e r a t u r e has emerged s u g g e s t i n g t h a t a v a r i e t y of " a f f e c t i v e s t a t e s " may be a c c u r a t e l y i n f e r r e d from n o n v o c a l e x p r e s s i v e d i s p l a y s (Ekman & F r i e s e n , 1965, 1974a, 1974b; Waxer, 1974, 1977). Some a u t h o r s have f o r w a r d e d t h e p o s i t i o n t h a t n o n v o c a l e x p r e s s i o n s a r e l e s s s u b j e c t t o m o t i v a t e d d i s s i m u l a t i o n t h a n v e r b a l r e p o r t s , and may t h e r e f o r e be more a c c u r a t e i n d i c e s o f p r i v a t e s t a t e s ( c f . Ekman & F r i e s e n ' s , 1969, c o n c e p t of " n o n v e r b a l l e a k a g e " ) . D e s p i t e t h e i r i m p o r t a n c e , few s t u d i e s have examined t h e i n f l u e n c e o f s o c i a l v a r i a b l e s on n o n v o c a l p a i n e x p r e s s i o n s . L a n z e t t a , K l e c k , and t h e i r 72 c o l l e a g u e s have i n v e s t i g a t e d p a r a m e t e r s r e g u l a t i n g n o n v o c a l e x p r e s s i v e r e -sponses t o n o x i o u s s t i m u l a t i o n and the r e l a t i o n s h i p between e x p r e s s i v e r e -sponses and i n d i c e s o f s e l f - r e p o r t e d d i s t r e s s . L a n z e t t a , C a r t w r i g h t - S m i t h , and K l e c k (1976) r e p o r t e d p a r a l l e l changes i n autonomic and s e l f - r e p o r t i n d i c e s o f s t r e s s among s u b j e c t s i n s t r u c t e d t o i n t e n s i f y o r a t t e n u a t e f a c i a l r e s p o n s e s t o p a i n f u l s t i m u l i . K l e c k , Vaughan, C a r t w r i g h t - S m i t h , Vaughan, C o l b y , and L a n z e t t a (1976) examined r e l a t i o n s h i p s between e x p r e s s i v e be-h a v i o u r , e l e c t r o d e r m a l a c t i v i t y and s e l f - r e p o r t e d p a i n among s u b j e c t s b e i n g o b s e r v e d by someone e l s e , o r u n d e r g o i n g the e x p e r i m e n t a l o n e . S u b j e c t s b e i n g o b s e r v e d e x h i b i t e d d i m i n i s h e d e v i d e n c e o f d i s t r e s s as i n d i c a t e d by i n d e p e n d e n t r a t i n g s o f f a c i a l e x p r e s s i v e n e s s , d i m i n i s h e d e l e c t r o d e r m a l r e -s p o n s i v e n e s s , and l e s s s e l f - r e p o r t e d p a i n . I t was a r g u e d t h a t t h e s e f i n d i n g s s u p p o r t e d the t h e s i s t h a t m o d u l a t i o n s i n e x p r e s s i v e b e h a v i o u r i n s t i g a t e p a r a l l e l changes i n s u b j e c t i v e and autonomic components o f r e s p o n s e t o n o x i o u s s t i m u l i . I n s t u d i e s o f m o d e l i n g i n f l u e n c e s on p a i n , t h e a c t u a l b e h a v i o u r exem-p l i f i e d by models has been t o l e r a n t o r i n t o l e r a n t c h a r a c t e r i z a t i o n o f n o x i o u s s t i m u l i . The q u e s t i o n o f whether the m o d e l i n g i n f l u e n c e g e n e r a l i z e s t o o v e r t e x p r e s s i v e b e h a v i o u r , i m p o r t a n t i n a f f e c t i v e i n t e r p e r s o n a l s i t u a t i o n s , has n o t been a d d r e s s e d . The p r e s e n t s t u d y was d e s i g n e d t o i n v e s t i g a t e two i s s u e s . The f i r s t was whether o b s e r v e r s can d i s c r i m i n a t e e x p r e s s i v e b e h a v i o u r r e s u l t i n g from d i f f e r -e n t i n t e n s i t i e s o f n o x i o u s s t i m u l a t i o n . Assuming t h a t o b s e r v e r s c o u l d r e -l i a b l y d i s c r i m i n a t e t h e e x p r e s s i v e b e h a v i o u r a s s o c i a t e d w i t h d i f f e r e n t c u r r e n t i n t e n s i t i e s , t h e second q u e s t i o n a d d r e s s e d was whether o b s e r v e r s ' r a t i n g s o f t h e e x p r e s s i v e b e h a v i o u r o f s u b j e c t s exposed t o t o l e r a n t o r i n -t o l e r a n t m o d e l i n g o r c o n t r o l c o n d i t i o n s w o u l d e x h i b i t s y s t e m a t i c v a r i a t i o n s . 7 3 Sensory-de c i s i o n t h e o r y was employed as a t e c h n i q u e f o r e v a l u a t i n g t h e s e q u e s t i o n s . I f an i n d i v i d u a l i s g i v e n t h e t a s k o f o b s e r v i n g the b e h a v i o u r o f a n o t h e r and s p e c i f y i n g w h e t h e r , o r t o what e x t e n t a p a r t i c u l a r event has o c c u r r e d , t h e n the d a t a o b t a i n e d f r o m the o b s e r v e r can be a n a l y s e d w i t h SDT methods. The outcome o f such an a n a l y s i s w i l l p r o v i d e a measure o f t h e ob-s e r v e r ' s a b i l i t y t o d i f f e r e n t i a t e the c l a s s e s o f e v e n t s , and h i s o r h e r b i a s i n f a v o u r o f o r a g a i n s t r e p o r t i n g an e v e n t . I n the p r e s e n t s t u d y , r a t e r s o b s e r v e d t h e b e h a v i o u r o f s u b j e c t s exposed t o t h e 3 i n f l u e n c e c o n d i t i o n s o f E x p e r i m e n t 1, and made judgements as t o the l e v e l o f c u r r e n t a d m i n i s t e r e d on e a ch o f a s e r i e s o f t r i a l s . P r e v i o u s r e s e a r c h as i n d i c a t e d t h a t e x p o s u r e t o t o l e r a n t o r i n t o l e r a n t models, r e s p e c t i v e l y , d e c r e a s e s o r i n c r e a s e s p a i n r e p o r t s and p r o d u ces a l t e r a t i o n s i n a v o i d a n c e b e h a v i o u r c o n s i s t e n t w i t h a l t e r e d r e p o r t s . E v i d e n c e f r o m p s y c h o p h y s i o l o g i c a l s t u d i e s i n d i c a t e s as w e l l t h a t the t o l e r a n t m o d e l i n g m a n i p u l a t i o n p r o d u ces d i m i n i s h e d r e a c t i v i t y t o n o x i o u s s t i m u l a t i o n , w h i l e the i n t o l e r a n t c o n d i t i o n may be a s s o c i a t e d w i t h i n c r e a s e d r e a c t i v i t y . On t h e b a s i s o f t h i s e v i d e n c e , i n t h e c u r r e n t s t u d y i t was e x p e c t e d t h a t the t o l e r a n t m o d e l i n g c o n d i t i o n w o u l d i n f l u e n c e s u b j e c t s t o be l e s s r e a c t i v e t o the s t i m u l i . I t was h y p o t h e s i z e d , t h e r e f o r e , t h a t o b s e r v e r s r a t i n g s u b j e c t s i n t h e t o l e r a n t c o n d i t i o n w o u l d e x h i b i t p o o r e r d i s c r i m i n a t i o n w h i l e o b s e r v e r s r a t i n g s u b j e c t s i n the i n t o l e r a n t c o n d i t i o n w o u l d e x h i b i t enhanced d i s c r i m i n a t i o n . METHOD 74 S u b j e c t s . F i f t e e n p a i d female v o l u n t e e r s were r e c r u i t e d f r o m the u n d e r -g r a d u a t e p o p u l a t i o n o f t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a t o t a k e p a r t i n f o u r s e p a r a t e s e s s i o n s as o b s e r v i n g j u d g e s . S u b j e c t s were randomly a s s i g n e d t o t h r e e groups o f f i v e p e r s o n s each. A p p a r a t u s and M a t e r i a l s . V i d e o t a p e s t a k e n o f p a r t i c i p a n t s u n d e r g o i n g t h e s i g n a l d e t e c t i o n phase o f the second ( i n f l u e n c e d ) s e s s i o n o f the f i r s t s t u d y were shown t o s u b j e c t s on a 23 i n c h t e l e v i s i o n s e t v i a a Sony AV3400 v i d e o t a p e r e c o r d e r p l a y b a c k u n i t . Above the t e l e v i s i o n s c r e e n was mounted a s h e e t o f c a r d b o a r d d i s p l a y i n g the r a t i n g c a t e g o r i e s t h a t s u b j e c t s were t o employ. S u b j e c t s coded t h e i r r e s p o n s e s d i r e c t l y onto F o r t r a n c o d i n g forms. N i n e o f t h e 10 v i d e o t a p e s f r o m each o f the 3 groups o f s u b j e c t s i n t h e f i r s t s t u d y were s e l e c t e d f o r v i e w i n g . The v i d e o t a p e s o f one s u b j e c t f r o m each o f t h e T o l e r a n t and I n t o l e r a n t groups were randomly e x c l u d e d from p r e -s e n t a t i o n i n t h i s p a r t o f t h e s t u d y . E x c l u d e d as w e l l was the tape o f t h e one s u b j e c t i n t h e c o n t r o l group who d i d n o t complete t h e e n t i r e s i g n a l de-t e c t i o n s e r i e s . Each s e t o f n i n e t a p e s so formed was randomly d i v i d e d i n t o t h r e e groups o f t h r e e s u b j e c t s . P r o c e d u r e . When a l l f i v e o b s e r v i n g s u b j e c t s i n a group a r r i v e d a t t h e l a b o r a t o r y f o r the f i r s t s e s s i o n , t h e y were g r e e t e d by a female e x p e r i m e n t e r who r e a d a s t a n d a r d s e t o f i n s t r u c t i o n s . The e x p e r i m e n t was d e s c r i b e d as b e i n g c o n c e r n e d w i t h the way p e o p l e " . . . d i f f e r e n t i a t e t h e b e h a v i o u r . . . . o f o t h e r p e o p l e who a r e e x p e r i m e n t i n g v a r i o u s l e v e l s o f p a i n . " The c o n t e n t o f the v i d e o t a p e s was th e n e x p l a i n e d as f o l l o w s : The p e o p l e t h a t you w i l l be w a t c h i n g t o o k p a r t i n an e x p e r i m e n t on the p e r c e p t i o n o f p a i n . They were s e a t e d i n the l a b o r a t o r y and had an e l e c t r o d e a t t a c h e d t o t h e i r arm. Then t h e y were exposed t o 75 a s e r i e s o f e l e c t r i c s h o c k s , s t a r t i n g a t u n d e t e c -t a b l e l e v e l s , t h a t g r a d u a l l y i n c r e a s e d i n i n t e n s i t y u n t i l t h e y got p a i n f u l . The shocks i n c r e a s e d some more u n t i l t h e s u b j e c t s t o l d us t h e y were p a i n f u l enough t h a t t h e y w o u l d t o l e r a t e no more. A f t e r d o i n g t h i s a few t i m e s , t h r e e d i f f e r e n t p a i r s o f c u r r e n t s were d e t e r m i n e d . The f i r s t p a i r was a t an i n t e n s i t y t h a t the p e o p l e r e p o r t e d as j u s t b a r e l y d e t e c t a b l e . The second p a i r was a t a s t r o n g e r i n -t e n s i t y and the t h i r d p a i r was a t an i n t e n s i t y beyond what t h e y s a i d was p a i n f u l . So t h e r e were t h r e e l e v e l s o f p a i r s o f s h o c k s : l o w , medium, and h i g h . These t h r e e l e v e l s were t h e n p r e s e n t e d ... t o t h e s u b j e c t s many t i m e s . . . i n a random o r d e r , and each o c c u r r e d an e q u a l number of t i m e s . No m e n t i o n was made o f the i n f l u e n c e c o n d i t i o n s t h a t o b s e r v e d s u b j e c t s under-went. A f t e r t h i s d e s c r i p t i o n o f the t a s k , o b s e r v e r s were i n s t r u c t e d i n t h e i r t a s k . F o l l o w i n g e ach t r i a l o b s e r v e r s were t o i n d i c a t e w h e t h e r t h e y t h o u g h t t h a t the shock l e v e l e x p e r i e n c e d on t h e t r i a l was o f h i g h , moderate, o r low i n t e n s i t y . The i n s t r u c t i o n s t h e n c o n t i n u e d : . . . b e f o r e we s t a r t w i t h the e x p e r i m e n t i t s e l f , we u s u a l l y f i n d i t b e s t t o p r o v i d e you w i t h a l i t t l e b i t o f p r a c t i c e b e f o r e h a n d . So what I ' l l do i s show you a c o u p l e o f p r a c t i c e t a p e s . As we go t h r o u g h , pay c l o s e a t t e n t i o n t o t h e b e h a v i o u r o f t h e p e r s o n you a r e w a t c h i n g . Look f o r any s i g n s i n t h e i r b e h a v i o u r t h a t w i l l g i v e you a c l u e as t o t h e l e v e l o f shock t h e y ' r e r e c e i v i n g and how much p a i n t h e y ' r e f e e l i n g . B e f o r e the s e s s i o n began, o b s e r v e r s were a l s o i n s t r u c t e d t o d i s t r i b u t e t h e i r r e s p o n s e s w e l l , and make use o f a l l the c a t e g o r i e s . F o l l o w i n g i n s t r u c t i o n s , the p r a c t i c e t r i a l s began. D u r i n g t h e s e t r i a l s , s u b j e c t s o b s e r v e d two o f the t h r e e t a p e s w h i c h had been randomly e x c l u d e d f r o m p r e s e n t a t i o n i n t h e major p a r t o f t h e s t u d y . F o l l o w i n g each t r i a l i n t h e p r a c t i c e s e r i e s , t h e e x p e r i m e n t e r p r o v i d e d f e e d b a c k by t e l l i n g t h e r a t e r s w h i c h o f t h e t h r e e c u r r e n t l e v e l s t h e s u b j e c t had r e c e i v e d . 76 When th e p r a c t i c e t r i a l s had been c o m p l e t e d , t h e e x p e r i m e n t p r o p e r be-gan. Each sample o f f i v e o b s e r v e r s r a t e d a l l t a p e s i n one o f t h e t h r e e " s q u a d s " o f t h r e e r a n d o m l y - s e l e c t e d s u b j e c t s from each o f the i n f l u e n c e c o n d i t i o n s o f t h e f i r s t s t u d y . I n o r d e r t o a s s e s s r e p e a t e d measures r e l i -a b i l i t y , a l l o b s e r v e r s i n each sample r a t e d t h e same ta p e s f r o m t h e i r r e -s p e c t i v e "squad" t w i c e i n d i f f e r e n t s e s s i o n s . The tape o f each o b s e r v e d s u b j e c t was c o m p r i s e d o f 18 examples each o f b e h a v i o u r e l i c i t e d by low, medium, and h i g h c u r r e n t i n t e n s i t i e s . The mean c u r r e n t i n t e n s i t i e s f o r each group o f o b s e r v e d s u b j e c t s a r e p r e s e n t e d i n T a b l e 2:1. F o l l o w i n g t h e p r a c t i c e t r i a l s , o b s e r v e r s were n o t c o n t i n u o u s l y i n f o r m e d what sh o c k l e v e l t h e s u b j e c t r e c e i v e d . However, i n o r d e r t o g u a r d a g a i n s t t h e p o s s i b i l i t y o f p e r f o r m a nce d e t e r i o r a t i o n by the o b s e r v e r s , t h e e x p e r i -menter p r o v i d e d f e e d b a c k on a randomly s e l e c t e d 33% o f t r i a l s . When o b s e r -v e r s had c o m p l e t e l y f i n i s h e d t h e i r r a t i n g s o f each t a p e , t h e y c o m p l e t e d a • q u e s t i o n n a i r e c o n s i s t i n g o f two 7 - p o i n t L i k e r t s c a l e s a s k i n g them to r a t e t h e amount o f d i s t r e s s e x h i b i t e d by t h e s u b j e c t and t h e e a se o r d i f f i c u l t y o f r a t i n g the s u b j e c t . F o u r t e s t i n g s e s s i o n s o f a p p r o x i m a t e l y two h o u r s i n l e n g t h and s p a c e d a t one week i n t e r v a l s were r e q u i r e d t o complete d a t a c o l l e c t i o n . 77 T a b l e 2:1 Means o f Low, Medium, and Hi g h C u r r e n t I n t e n s i t i e s A d m i n i s t e r e d t o Observed S u b j e c t s . Group Low C u r r e n t I n t e n s i t y Medium H i g h T o l e r a n t 0.88 3.73 6.95 C o n t r o l 1.13 4.00 7.28 I n t o l e r a n t 1.19 3.97 6.33 Note: Means a r e i n m i l l i a m p e r e s and r e p r e s e n t the mean o f two i n t e n s i t i e s a t e a ch o f t h e l o w , medium, and h i g h l e v e l s . 78 RESULTS F o r the p u r p o s e s o f SDT a n a l y s e s , c o n d i t i o n a l p r o b a b i l i t i e s o f o c c u r r -ence o f each r e s p o n s e g i v e n the o c c u r r e n c e o f an example o f s u b j e c t b e h a v i o u r f o l l o w i n g p r e s e n t a t i o n o f each o f the t h r e e p a i r s o f shock i n t e n s i t i e s were c a l c u l a t e d . These p r o b a b i l i t i e s were t h e n cumulated from t h e low t o t h e h i g h r e s p o n s e c a t e g o r y f o r each s t i m u l u s i n t e n s i t y l e v e l i n t h e manner o u t l i n e d by C l a r k (1974). F o l l o w i n g t h e g e n e r a t i o n o f c u m u l a t i v e p r o b a b i l i t y t a b l e s e s t i m a t e s o f d.' and L^ were c a l c u l a t e d a t the "medium" and t h e " l o w " re s p o n s e c a t e g o r y f o r t h e h i g h v s . medium and medium v s . low d i s c r i m i n a t i o n s . The d a t a so d e r i v e d were i n v e s t i g a t e d by a n a l y s i s o f v a r i a n c e . Two p o t e n t i a l e f f e c t s were o f p r i n c i p a l i n t e r e s t i n t h e s e a n a l y s e s : (1) whether t h e SDT pa r a m e t e r s v a r i e d s y s t e m a t i c a l l y as a f u n c t i o n o f t h e d i s c r i m i n a t i o n t h a t o b s e r v e r s were r e q u i r e d t o p e r f o r m ( i . e . , d i d d' and/or L d i f f e r between — — x t h e medium v s . low (ML) and the h i g h v s . medium (HM) d i s c r i m i n a t i o n ) , and (2) w h e t h e r t h e p a r a m e t e r s v a r i e d s y s t e m a t i c a l l y as a f u n c t i o n o f t h e c o n d i -t i o n s t h a t o b s e r v e d s u b j e c t s had been exposed t o i n E x p e r i m e n t 1. I t was e x p e c t e d t h a t the HM d i s c r i m i n a t i o n w o u l d be a s s o c i a t e d w i t h g r e a t e r d' v a l u e s t h a n t h e ML d i s c r i m i n a t i o n . W i t h r e s p e c t t o s o c i a l i n f l u e n c e e f f e c t s , i t was e x p e c t e d t h a t o b s e r v e r s r a t i n g s u b j e c t s exposed t o t o l e r a n t models w o u l d e x h i b i t r e d u c t i o n s i n a b i l i t y t o d i s c r i m i n a t e b e h a v i o u r s r e s u l t i n g f r o m t h e t h r e e d i f f e r e n t s t i m u l u s i n t e n s i t i e s ( a r e d u c t i o n i n d.') r e l a t i v e t o the same o b s e r v e r s r a t i n g c o n t r o l s u b j e c t s . Cn t h e o t h e r hand, i t was ex-p e c t e d t h a t o b s e r v e r s r a t i n g s u b j e c t s exposed t o an i n t o l e r a n t model w o u l d e x h i b i t enhanced d i s c r i m i n a t i o n . F o r t h e ANOVAs v a l u e s o f d_' and L_^  a t each c r i t e r i o n a l o n g the r a t i n g s c a l e were a v e r a g e d . These average d.' and _L v a l u e s were t h e n a v e r a g e d 79 a c r o s s t h e t h r e e s u b j e c t s p e r i n f l u e n c e c o n d i t i o n t h a t were p r e s e n t e d t o each o b s e r v e r sample. I n o r d e r t o e x t r a c t the v a r i a n c e a s s o c i a t e d w i t h each o b s e r v e r s a m p l e - v i d e o t a p e squad p a i r i n g , v i d e o t a p e squads were i n c l u d e d as a between-groups f a c t o r i n t h e ANOVA. The o v e r a l l d e s i g n , t h e n , was a 3 (Squads) X 2 ( R e p l i c a t i o n s ) X 3 ( M o d e l i n g C o n d i t i o n s ) X 2 ( D i s c r i m i n a t i o n s ) ANOVA, w i t h r e p e a t e d measurements on t h e l a s t t h r e e f a c t o r s . R e s u l t s o f the a n a l y s i s o f v a l u e s o f L_x were l a r g e l y n e g a t i v e . The o n l y e f f e c t t h a t approached s i g n i f i c a n c e was t h a t f o r R e p l i c a t i o n s , _F(1,12) = 4.07, p_ = .067. T h i s r e f l e c t e d o b s e r v e r s ' tendency t o adopt more c o n s e r -v a t i v e c r i t e r i a f o r r e p o r t i n g the o c c u r r e n c e o f h i g h e r shock i n t e n s i t i e s the second t i m e t h a t t h e y v i e w e d each v i d e o - t a p e (M R e p l i c a t i o n 1 = 0.9 7; " R e p l i c a t i o n 2 = 1.18). A number o f s i g n i f i c a n t f i n d i n g s emerged f r o m the a n a l y s i s o f d_' v a l u e s . The most i m p o r t a n t were a s i g n i f i c a n t D i s c r i m i n a t i o n s e f f e c t , _F(1,12) = 49.60, p_ < -.01, and a s i g n i f i c a n t M o d e l i n g C o n d i t i o n s e f f e c t , _F(1,12) = 22.59, p_< .01. E x a m i n a t i o n o f means r e v e a l e d t h a t d.' v a l u e s f o r t h e HM d i s c r i m i n a t i o n were g r e a t e r t h a n t h o s e f o r t h e ML d i s c r i m i n a t i o n (M d' = 0.65 and 0.21, r e s p e c t i v e l y ) . Thus, the a b i l i t y t o d i s c r i m i n a t e s h o c k - e l i c i t e d e x p r e s s i v e r e s p o n s e s was c l o s e l y r e l a t e d t o t h e magnitude o f c u r r e n t t h e o b s e r v e d sub-j e c t was exposed t o . Mean d.' v a l u e s f o r t h e s i g n i f i c a n t M o d e l i n g groups main e f f e c t were 0.31 f o r group T, 0.42 f o r group I , and 0.5 7 f o r group C. The d i f f e r e n c e s between a l l t h r e e means exceeded t h e c r i t i c a l v a l u e f o r Dunn's m u l t i p l e c o m p a r i s o n p r o c e d u r e (_t* D .05/2;3,24 = 0.10). Thus o b s e r v e r s e x h i b i t e d r e l i a b l y l o w e r d_' v a l u e s when o b s e r v i n g t h e b e h a v i o u r o f s u b j e c t s exposed t o an i n t o l e r a n t model r e l a t i v e t o when t h e y were o b s e r v i n g the b e h a v i o u r o f " c o n t r o l s , and th e y e x h i b i t e d even l o w e r _d' v a l u e s when o b s e r v i n g the b e h a v i o u r o f s u b j e c t s e x-80 posed t o a t o l e r a n t model r e l a t i v e t o when t h e y o b s e r v e d e i t h e r i n t o l e r a n t o r c o n t r o l s u b j e c t s . O t h e r s i g n i f i c a n t e f f e c t s emerged f r o m the a n a l y s i s ; however, t h e y were l e s s r e a d i l y i n t e r p r e t a b l e s i n c e t h e y i n v o l v e d t he o b s e r v e r samples v a r i a b l e w h i c h was i n c l u d e d i n t h e a n a l y s i s s i m p l y t o e x t r a c t the v a r i a n c e r e s u l t i n g f r o m p a r t i c u l a r o b s e r v e r s a m p l e - v i d e o t a p e s squad p a i r i n g s . The o v e r a l l Squads e f f e c t was s i g n i f i c a n t , F ( l , 1 2 ) = 7.12, £ <: .01, i n d i c a t i n g t h a t the t h r e e o b s e r v e r s a m p l e - v i d e o t a p e squad p a i r i n g s were a s s o c i a t e d w i t h d i f f e r e n t o v e r a l l d_' v a l u e s (means: Sample 1 = 0.50; Sample 2 = 0.5 7; Sample 3 = 0.23). There was a s i g n i f i c a n t Squads x R e p l i c a t i o n s i n t e r a c t i o n , F_(2,12) = 5.85, p_ a;-t05, r e f l e c t i n g d i f f e r e n t i a l p a t t e r n s o f re s p o n s e a c r o s s b o t h r e p l i c a -t i o n s f o r a l l t h r e e samples. The means a r e p r e s e n t e d i n T a b l e 2:2 where i t can be seen t h a t o b s e r v e r s j u d g i n g s u b j e c t s i n Squad 1 e x h i b i t e d i mproved d i s c r i m i n a t i o n from R e p l i c a t i o n 1 t o R e p l i c a t i o n 2, Squad 2 was a s s o c i a t e d w i t h r e d u c e d d i s c r i m i n a t i o n from R e p l i c a t i o n 1 t o R e p l i c a t i o n 2, and Squad 3 e x h i b i t e d m i n i m a l change. A s i g n i f i c a n t e f f e c t was a l s o a t t r i b u t a b l e t o the Squads X D i s c r i m i n a -t i o n s i n t e r a c t i o n , F (2,12) = 10.79, p < .01. The means f o r t h i s e f f e c t a r e p r e s e n t e d i n T a b l e 2:3 where i t can be seen t h a t the magnitude o f r e d u c t i o n i n d.' between t h e HM and t h e ML d i s c r i m i n a t i o n s v a r i e d a c r o s s the t h r e e Squads. Squad 1 was a s s o c i a t e d w i t h t h e g r e a t e s t HM t o ML d e c r e a s e i n d.' , Squad 2 an i n t e r m e d i a t e d e c r e a s e , and Squad 3 t h e l e a s t d e c r e a s e . I n no c a s e , however, d i d t h e o v e r a l l d i r e c t i o n o f change i n d.' d i f f e r between squads. Two f u r t h e r s i g n i f i c a n t i n t e r a c t i o n e f f e c t s o c c u r r e d , b o t h i n v o l v i n g the m o d e l i n g v a r i a b l e : Squads X M o d e l i n g C o n d i t i o n s , F_ (2,24) = 10.39, p < .01; and Squads X M o d e l i n g C o n d i t i o n s X D i s c r i m i n a t i o n s , ]? (2,24) = 4.52, p- < 81 T a b l e 2:2 Mean d.' V a l u e s f o r the Squads x R e p l i c a t i o n s I n t e r a c t i o n R e p l i c a t i o n Squad 1 Squad 2 Squad 3 1 0.40 0.76 0.20 2 0.61 0.37 0.25 82 .01. Means f o r the 3 - f a c t o r i n t e r a c t i o n a r e p r e s e n t e d i n T a b l e 2:4 where i t can be seen t h a t w h i l e t h e r e was a g e n e r a l r e d u c t i o n i n d_' f r o m the HM t o t h e ML d i s c r i m i n a t i o n , o b s e r v e r s j u d g i n g s u b j e c t s i n Squad 3 e x h i b i t e d i n o r d i n -a t e l y low mean d_' v a l u e s a t t h e HM d i s c r i m i n a t i o n . The i n t e r a c t i o n i s n o t d i s o r d i n a l w i t h r e s p e c t t o t h e e f f e c t s o f M o d e l i n g C o n d i t i o n s . T h e r e f o r e , the d a t a do n o t s u g g e s t t h a t t h e o v e r a l l c o n c l u s i o n t h a t o b s e r v e r s r a t i n g s u b j e c t s e xposed t o a t o l e r a n t model e x h i b i t e d r e d u c e d a b i l i t y t o d i s c r i m i n -a t e needs t o be q u a l i f i e d s i g n i f i c a n t l y . G l o b a l r a t i n g s o f d i s t r e s s and d i f f i c u l t y . O b s e r v e r s ' r a t i n g s on t h e p o s t e x p e r i m e n t a l q u e s t i o n n a i r e e v a l u a t i n g the o v e r a l l l e v e l o f d i s t r e s s e x h i b i t e d by o b s e r v e d s u b j e c t s were e n t e r e d i n t o the same ANOVA d e s i g n . The M o d e l i n g C o n d i t i o n s term approached c o n v e n t i o n a l l e v e l s o f s t a t i s t i c a l r e l i a b i l i t y , F_(2,24) = 3.33, p_ = .05. However, m u l t i p l e c o m parisons w i t h Dunn's p r o c e d u r e f a i l e d t o demonstrate t h a t any p a i r o f m o d e l i n g c o n d i t i o n s d i f f e r e d r e l i a b l y (t_'D .05/2, 3, 24 = 0.68; Mean d i s t r e s s r a t i n g s : Group T = 2.96, Group I = 2.79, Group C = 3.44). The same model o f a n a l y s i s was employed i n e v a l u a t i n g o b s e r v e r s ' r a t i n g s o f how d i f f i c u l t each o b s e r v e d s u b j e c t was t o j u d g e . A r e l i a b l e M o d e l i n g C o n d i t i o n s e f f e c t emerged from t h i s a n a l y s i s , _F(2,24) = 11.75, £ < .01. M u l -t i p l e c omparisons by means o f Dunn's p r o c e d u r e i n d i c a t e d t h a t t h i s e f f e c t was e x c l u s i v e l y a c c o u n t e d f o r by the i n c r e a s e d d i f f i c u l t y t h a t o b s e r v e r s r e p o r t e d when j u d g i n g s u b j e c t s e xposed t o a t o l e r a n t model r e l a t i v e t o judgements o f i n t o l e r a n t and c o n t r o l s u b j e c t s . R a t i n g s o f t h e d i f f i c u l t y o f j u d g i n g i n -t o l e r a n t and c o n t r o l s u b j e c t s d i d n o t d i f f e r (_t' D. 05/2,3,24 = 0.29; Means: Group T = 5.28, Group I = 4.89, Group C = 4.74). 83 T a b l e 2:3 Mean d.' V a l u e s f o r t h e Squads x D i s c r i m i n a t i o n s I n t e r a c t i o n D i s c r i m i n a t i o n Squad 1 Squad 2 Squad 3 HM 0.92 0.72 0.31 ML 0.09 0.42 0.14 Note: HM = H i g h v s . Medium d i s c r i m i n a t i o n ML = Medium v s . Low d i s c r i m i n a t i o n 84 T a b l e 2:4 Mean _d' V a l u e s f o r t h e Squads x M o d e l i n g Groups x D i s c r i m i n a t i o n s I n t e r a c t i o n M o d e l i n g Group D i s c r i m i n a t i o n Squad 1 Squad 2 Squad 3 1 HM 0.65 0.78 -0.06 ML -0.19 0.44 0.23 2 HM 0.78 0.63 0.51 ML 0.20 0.42 -0.01 3 HM 1.33 0.75 0.48 ML 0.25 0.39 0.20 85 A s i g n i f i c a n t Squads x M o d e l i n g C o n d i t i o n s i n t e r a c t i o n was a l s o o b t a i n e d , J ? ( 2 , 2 4 ) = 1 7 . 7 0 , p_ <,.01. I n s p e c t i o n o f the means f o r t h i s i n t e r a c t i o n ( T a b l e 2 :5) i n d i c a t e d t h a t when o b s e r v e r s r a t e d s u b j e c t s f r o m Squads 1 and 3 the g e n e r a l t r e n d t o w a r d e l e v a t e d d i f f i c u l t y r a t i n g s a s s o c i a t e d w i t h s u b j e c t s i n group T r e l a t i v e t o t h o s e a s s o c i a t e d w i t h s u b j e c t s i n groups I and C h e l d . R a t i n g s o f s u b j e c t s from Squad 2 d i d n o t appear t o d i f f e r a c r o s s t h e 3 m o d e l i n g c o n d i t i o n s . 86 T a b l e 2:5 Mean D i f f i c u l t y R a t i n g s A s s o c i a t e d w i t h each Squad when O b s e r v e r s Made Judgements o f S u b j e c t s from the Three S o c i a l I n f l u e n c e C o n d i t i o n s o f Study 1 Squad T o l e r a n t M o d e l i n g C o n d i t i o n C o n t r o l I n t o l e r a n t 1 5.70 4.73 4.73 2 4.97 5.59 5.67 3 5.17 4.33 3.83 Note: Minimum r a t i n g = 1 ( v e r y e a s y ) ; Maximum r a t i n g = 7 ( v e r y d i f f i c u l t ) . 87 D i s c u s s i o n A number o f i n t e r e s t i n g f i n d i n g s emerged f r o m t h i s s t u d y . The r e s u l t s may be summarized as f o l l o w s . O b s e r v e r s , i n g e n e r a l adopted f a i r l y s t a b l e d e c i s i o n c r i t e r i a when making judgements o f t h e l e v e l o f c u r r e n t t h a t ob-s e r v e d s u b j e c t s were exposed t o . T h i s c o n c l u s i o n i s b a s e d on t h e f a c t t h a t the ANOVA p e r f o r m e d on v a l u e s o f L_x d i d n o t r e v e a l any s t a t i s t i c a l l y r e l i a b l e v a r i a t i o n as a f u n c t i o n o f the m a n i p u l a t e d v a r i a b l e s . O b s e r v e r s were c a p a b l e o f d i s c r i m i n a t i n g d i f f e r e n c e s i n the b e h a v i o u r e l i c i t e d by low, medium and h i g h shock l e v e l s as e v i d e n c e d by the f a c t t h a t d.' v a l u e s were g e n e r a l l y g r e a t e r t h a n z e r o . The d i s c r i m i n a b i l i t y o f o b s e r v e d s u b j e c t s ' b e h a v i o u r v a r i e d s y s t e m a t i c a l l y as a f u n c t i o n o f t h e t y p e o f d i s c r i m i n a t i o n t h a t ob-s e r v e r s were r e q u i r e d t o make. The d i f f e r e n c e between b e h a v i o u r c o n t r o l l e d by h i g h and medium c u r r e n t l e v e l s was more r e a d i l y d i s c r i m i n a t e d t h a n was the d i f f e r e n c e between b e h a v i o u r c o n t r o l l e d by medium and low c u r r e n t l e v e l s . The d i s c r i m i n a b i l i t y o f s h o c k - e l i c i t e d e x p r e s s i o n s v a r i e d s y s t e m a t i c a l l y as a f u n c t i o n o f t h e m o d e l i n g c o n d i t i o n o f t h e o b s e r v e d s u b j e c t , w i t h t h e be-h a v i o u r o f s u b j e c t s exposed t o a t o l e r a n t model a s s o c i a t e d w i t h t h e l o w e s t v a l u e s o f d_' , and t h e b e h a v i o u r o f s u b j e c t s exposed t o an i n a c t i v e c o -p a r t i c i p a n t a s s o c i a t e d w i t h the h i g h e s t d.' v a l u e s . V a r i a t i o n i n t h i s e f f e c t o c c u r r e d a c r o s s t h e 3 v i d e o t a p e squads, however, th e n a t u r e o f t h i s v a r i a t i o n was n o t such as t o c a l l i n t o q u e s t i o n the g e n e r a l a s s o c i a t i o n o f r e d u c e d d_' v a l u e s w i t h s u b j e c t s i n the t o l e r a n t m o d e l i n g c o n d i t i o n . O b s e r v e r s ' r a t i n g s o f the amount o f d i f f i c u l t y t h e y had i n making the d i s c r i m i n a t i o n s i n d i c a t e d t h a t t h e y found s u b j e c t s i n the t o l e r a n t group more d i f f i c u l t t o j u d g e t h a n s u b j e c t s i n t h e o t h e r groups. F i n a l l y , o b s e r v e r s ' p o s t o b s e r v a t i o n r a t i n g s o f t h e amount o f d i s t r e s s e x h i b i t e d by o b s e r v e d s u b j e c t s v a r i e d w i t h t h e m o d e l i n g c o n d i t i o n o f the o b s e r v e d s u b j e c t . 88 > . W h i l e t h e r e have been s e v e r a l a t t e m p t s t o a p p l y SDT methods t o s o c i a l p r o c e s s e s ( G r o s s b e r g & G r a n t , 1 9 7 6 ) , o n l y one o t h e r s t u d y has e x t e n d e d SDT p r o c e d u r e s t o t h e a n a l y s i s o f o v e r t s o c i a l b e h a v i o u r i n humans (Thompson, 1978). T h e r e f o r e , b o t h m e t h o d o l o g i c a l and s u b s t a n t i v e i s s u e s r e q u i r e d i s -c u s s i o n . The f a c t t h a t the HM d i s c r i m i n a t i o n was a s s o c i a t e d w i t h g r e a t e r v a l u e s o f _d' t h a n the ML d i s c r i m i n a t i o n s o l i d l y s u p p o r t s the u t i l i t y o f SDT p r o c e d u r e s i n i n v e s t i g a t i o n s o f p a i n - e l i c i t e d e x p r e s s i v e b e h a v i o u r . C l e a r l y , s u b s t a n t i a l q u a n t i t a t i v e and/or q u a l i t a t i v e d i f f e r e n c e s i n e x p r e s -s i v e b e h a v i o u r a r e pr o d u c e d by e l e c t r i c s h o c k s v a r y i n g a c r o s s g l o b a l i n t e n -s i t y l e v e l s . T h i s o c c u r r e d even i n a r e l a t i v e l y i m p o v e r i s h e d l a b o r a t o r y e n vironment where d i r e c t v i s u a l c o n t a c t between s u b j e c t , c o - p a r t i c i p a n t , and e x p e r i m e n t e r was e l i m i n a t e d . The f a c t t h a t the v i d e o t a p e camera was p r e s e n t and i n s u b j e c t s ' c l e a r v i e w i n t h e s e s s i o n d u r i n g w h i c h t h e i r b e h a v i o u r was t a p e d was o f some c o n c e r n , s i n c e p r e v i o u s i n v e s t i g a t o r s have i n t i m a t e d t h a t s u b j e c t s w i l l a c t i v e l y m o n i t o r and m i n i m i z e t h e i r e x p r e s s i v e b e h a v i o u r when t h e y know t h a t i t i s b e i n g r e c o r d e d ( L a n z e t t a e t a l . , 1976; K l e c k e t a l . , 1976). S i n c e p o s i t i v e n o n z e r o d_' v a l u e s were the r u l e i n t h i s s t u d y , and s i n c e v a l u e s o f d_' v a r i e d s y s t e m a t i c a l l y w i t h t h e t y p e o f d i s c r i m i n a t i o n t h a t o b s e r v e r s were r e q u i r e d t o make, i t appears t h a t s u c h a phenomenon e i t h e r d i d n o t o c c u r o r was o f m i n i m a l i m p o r t a n c e . O t h e r , u n s y s t e m a t i c d a t a s u p p o r t t h i s c o n t e n t i o n . D u r i n g the d e b r i e f -i n g t h a t f o l l o w e d Experiment. 1, most s u b j e c t s e x h i b i t e d c o n s i d e r a b l e s u r p r i s e when i n f o r m e d t h a t p a r t o f the purpose o f t h e s t u d y was t o a n a l y s e t h e r e -c o r d i n g s o f t h e i r e x p r e s s i v e b e h a v i o u r . A l m o s t a l l s u b j e c t s r e p o r t e d h a v i n g f o r g o t t e n t h a t t h e y were b e i n g r e c o r d e d . F u r t h e r m o r e , s i n c e t h e s e s u b j e c t s were t e s t e d and had t h e i r b e h a v i o u r r e c o r d e d o v e r an e x t e n d e d p e r i o d o f t i m e , i t seems u n l i k e l y t h a t t h e y w o u l d have m a i n t a i n e d s u c h a " c e n s o r s h i p " o f t h e i r e x p r e s s i v e b e h a v i o u r . 89 The meaning o f t h e measure, d.' as a p p l i e d t o the d a t a f r o m t h i s s t u d y r e q u i r e s f u r t h e r e l a b o r a t i o n . d/ p r o v i d e s an i n d e x o f t h e d i s c r i m i n a b i l i t y o f 2 o r more c l a s s e s o f e v e n t s . I n t h e p r e s e n t c a s e , t h e e v e n t s o f i n t e r e s t were th e o v e r t e x p r e s s i v e b e h a v i o u r s o f s u b j e c t s , e l i c i t e d by each o f t h e 3 s t i m u l u s l e v e l s t h a t t h e y were exposed t o . The c u r r e n t i n t e n s i t i e s p r e -s e n t e d t o o b s e r v e d s u b j e c t s were s e l e c t e d , p r i o r t o t h e i r u n d e r g o i n g p a i n -m o d u l a t i n g m a n i p u l a t i o n s , f r o m 3 g l o b a l l e v e l s : (1) the n o n a v e r s i v e s e n s a -t i o n t h r e s h o l d , (2) s l i g h t l y b e l o w p a i n t h r e s h o l d , (3) t h e c l e a r l y p a i n f u l m i d p o i n t between p a i n t h r e s h o l d and p a i n t o l e r a n c e . Only t h e l a t t e r s t i m u l u s l e v e l w o u l d be e x p e c t e d t o r e l i a b l y p r o v oke e x p r e s s i v e r e s p o n s e s c l e a r l y i n -d i c a t i v e o f " p a i n " . S i n c e d_' v a l u e s i n c r e a s e d m a r k e d l y from the ML t o t h e HM d i s c r i m i n a t i o n , i t i s r e a s o n a b l e t o i n f e r t h a t t h i s improvement i n ob-s e r v e r s ' p e r f o r m a n c e was c o n t i n g e n t upon the o c c u r r e n c e o f s a l i e n t b e h a v i o u r s on t h e p a r t of t h e o b s e r v e d s u b j e c t t h a t met a c o n s e n s u a l d e f i n i t i o n o f p a i n . Thus, i n t h e p r e s e n t c o n t e x t , i t appears t h a t o b s e r v e r s ' d i s c r i m i n a t i o n s were c o n t r o l l e d l a r g e l y by the o c c u r r e n c e o f b e h a v i o u r s i n d i c a t i v e o f p a i n , and i n t h i s s ense i t can be a r g u e d t h a t the g r e a t e r d_' f o r the HM d i s c r i m i n a t i o n r e s u l t e d f r o m e x p r e s s i v e b e h a v i o u r i n d i c a t i v e o f p a i n . T h i s i n t e r p r e t a t i o n o f d.' l e n d s f u r t h e r i m p o r t a n c e t o t h e f i n d i n g o f r e -l i a b l e d i f f e r e n c e s i n d i s c r i m i n a b i l i t y as a f u n c t i o n o f t h e m o d e l i n g c o n d i -t i o n o f the o b s e r v e d s u b j e c t . The p r e s e n c e o f any c o n c u r r e n t l y - v e r b a l i z i n g model, t o l e r a n t , o r i n t o l e r a n t , was a s s o c i a t e d w i t h a r e l i a b l e r e d u c t i o n i n the d i s c r i m i n a b i l i t y o f an o b s e r v e d s u b j e c t ' s b e h a v i o u r . F u r t h e r m o r e , i f t h e model was t o l e r a n t , t h e r e was a r e l i a b l y g r e a t e r decrement i n t h e d i s c r i m i n a b i l i t y o f the o b s e r v e d s u b j e c t ' s b e h a v i o u r . I t had been e x p e c t e d t h a t the i n t o l e r a n t m o d e l i n g c o n d i t i o n w o u l d be a s s o c i a t e d w i t h an i n c r e m e n t i n t h e d i s c r i m i n a b i l i t y o f t h e b e h a v i o u r o f s u b j e c t s i n t h i s c o n d i t i o n . 90 T h i s outcome p r e s e n t s some i n t e r p r e t i v e p r o b l e m s . W h i l e i n E x p e r i m e n t 1 t h e s e s u b j e c t s gave e v i d e n c e o f e x p e r i e n c i n g g r e a t e r amounts o f p a i n , t h e y d i d n o t m a n i f e s t n o n v o c a l e x p r e s s i v e b e h a v i o u r t h a t a l l o w e d o b s e r v e r s t o r e a d i l y d i s c r i m i n a t e t h e a c t u a l i n t e n s i t y o f n o x i o u s s t i m u l a t i o n t h e y e x p e r i -e n c e d o r the amount o f d i s t r e s s t h e y r e p o r t e d . One i m p l i c a t i o n o f t h i s f i n d i n g might be t h a t the i m p a c t o f s o c i a l m o d e l i n g i n f l u e n c e s on p a i n be-h a v i o u r was n o t c o n s i s t e n t a c r o s s measures. However, t h i s c o n c l u s i o n does n o t seem t o f u l l y c a p t u r e t h e o b s e r v e d outcomes o f the e x p e r i m e n t . The h y p o t h e s i z e d d i f f e r e n t i a l r e d u c t i o n i n d.' among s u b j e c t s exposed t o a t o l e r a n t model d i d o c c u r . F u r t h e r m o r e , t h e magnitude o f t h e e f f e c t was s u f f i c i e n t l y l a r g e t h a t d.' v a l u e s were l o w e r t h a n t h o s e o b s e r v e d among s u b j e c t s e xposed t o an i n t o l e r a n t model. T h e r e f o r e , a l t e r n a t i v e a c c o u n t s might be e q u a l l y p l a u s i b l e . Two f u r t h e r c o n s i d e r a t i o n s m i g h t account f o r the f i n d i n g . F i r s t , sub-j e c t s i n t h e i n t o l e r a n t group were exposed n o t o n l y to t h e f o r m a l c o n t e n t o f t h e c o n f e d e r a t e ' s r a t i n g s , b u t a l s o t o t h e model's e x p r e s s i v e s t y l e w h i l e making the r a t i n g s . W h i l e the a c t u a l r a t i n g s made by t h e model i n d i c a t e d the e x p e r i e n c e o f g r e a t e r amounts o f p a i n t h a n the s u b j e c t was r e p o r t i n g , t h e manner i n w h i c h t h e model made h e r r a t i n g s was, i n f a c t , q u i t e d i s -p a s s i o n a t e . As E p l e y (1974, p. 2 7 3 ) , i n a r e v i e w o f t h e e f f e c t s on r e a c t i o n s t o a v e r s i v e s t i m u l a t i o n o f t h e p r e s e n c e o f companions has n o t e d , "A companion t h a t e m i t s c alm r e s p o n s e s i n a t h r e a t e n i n g s i t u a t i o n may e l i c i t s i m i l a r be-h a v i o u r s from t h e o b s e r v i n g s u b j e c t . " I t seems l i k e l y t h a t t h e r e d u c e d d i s c r i m i n a b i l i t y o f t h e b e h a v i o u r o f s u b j e c t s exposed t o an i n t o l e r a n t model was c o n t r o l l e d by the r e l a t i v e l y c a lm e x p r e s s i v e s t y l e o f t h e model. Sub-j e c t s e xposed t o an i n a c t i v e c o - p a r t i c i p a n t were n o t exposed t o e x p r e s s i v e communication from t h e i r companion; hence, t h e i r own e x p r e s s i v e b e h a v i o u r was l i k e l y r e l a t i v e l y u n i n f l u e n c e d . The adequacy o f t h i s i n t e r p r e t a t i o n c o u l d r e a d i l y be. a s s e s s e d by d i r e c t m a n i p u l a t i o n o f f o r m a l and e x p r e s s i v e a s p e c t s o f the model's communications. An a l t e r n a t i v e e x p l a n a t i o n f o r r e d u c e d d i s c r i m i n a b i l i t y o f t h e b e h a v i o u r o f s u b j e c t s e xposed t o an i n t o l e r a n t model r e l a t e s t o the e x c e s s i v e d r o p o u t r a t e o f s u b j e c t s i n t h i s group i n E x p e r i m e n t 1. I t may have been t h a t t h o s e s u b j e c t s most l i k e l y t o e x h i b i t enhanced p a i n d i s p l a y s as a f u n c t i o n o f ex-p o s u r e t o an i n t o l e r a n t model were so d i s t r e s s e d by t h e p r o c e d u r e s t h a t they t e r m i n a t e d the e x p e r i m e n t . Thus, t h e f i n d i n g o f r e d u c e d d i s c r i m i n a b i l i t y i n t h i s group may have been an a r t i f a c t r e s u l t i n g from s e l e c t i o n f o r s u b j e c t s who w o u l d e x h i b i t m i n i m a l d i s t r e s s upon e x p o s u r e t o the p r o c e d u r e s . R e g a r d l e s s o f w h e t h e r e i t h e r o f t h e s e e x p l a n a t i o n s i s c o r r e c t , the f i n d i n g t h a t the b e h a v i o u r o f s u b j e c t s exposed t o a t o l e r a n t model was l e s s d i s c r i m i n a b l e t h a n t h e b e h a v i o u r o f s u b j e c t s i n b o t h o f t h e o t h e r groups was o f s u b s t a n t i a l i n t e r e s t and was c o n s i s t e n t w i t h t h e i r v e r b a l r e p o r t o f p a i n i n E x p e r i m e n t 1. I n a d d i t i o n t o r e d u c i n g r e p o r t s o f p a i n and a v o i d a n c e o f s t i m u l a t i o n a t g r e a t e r i n t e n s i t i e s , t o l e r a n t m o d e l i n g seemed t o q u i t e c l e a r l y r e d u c e . t h e e m i s s i o n o f n o n v o c a l b e h a v i o u r s i n d i c a t i v e o f the p r e s e n c e o f p a i n . T h i s f i n d i n g i s p a r t i c u l a r l y i m p o r t a n t f o r s o c i a l a c c o u n t s of t h e o r i g i n s o f v a r i a t i o n s i n s t y l e s o f r e s p o n s e t o p a i n f u l s t i m u l a t i o n f o r a t l e a s t two r e a -s ons. F i r s t , i t i d e n t i f i e s a s p e c i f i c s e t o f s o c i a l a n t e c e d e n t c o n d i t i o n s t h a t c o n t r o l o v e r t d i s p l a y s o f p a i n . Second, the e f f e c t o f t h i s s e t o f a n t e c e d e n t s — r e m o v a l o r r e d u c t i o n o f p a i n d i s p l a y s — c a n be c o n c e i v e d o f as m i n i m i z i n g the o c c u r r e n c e o f a s e t o f s o c i a l d i s c r i m i n a t i v e s t i m u l i t h a t may s e t the o c c a s i o n f o r b e h a v i o u r s on t h e p a r t o f o t h e r s t h a t a r e i m p l i c a t e d i n the s h a p i n g o r maintenance o f p a i n b e h a v i o u r . The v a r i o u s i n t e r a c t i o n terms w h i c h a t t a i n 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 92 i n the ANOVA o f d_' v a l u e s were o f l i t t l e i n t e r e s t , s i n c e i n no case was i t i n d i c a t e d t h a t the o v e r a l l c o n c l u s i o n s w i t h r e s p e c t t o t h e main e f f e c t o f m o d e l i n g c o n d i t i o n s needed t o be q u a l i f i e d . S i m i l a r o v e r a l l p a t t e r n s h e l d f o r the e f f e c t s o f m o d e l i n g c o n d i t i o n s a c r o s s t h e 3 o b s e r v e r s a m p l e - v i d e o -t a p e squad p a i r i n g s ; however, t h e magnitude o f th e s e e f f e c t s v a r i e d some-what. The i n t e r a c t i o n s seem q u i t e c l e a r l y t o r e s u l t from i d i o s y n c r a t i c r e s p o n s e s t y l e s o f t h e s p e c i f i c s u b j e c t s whose t a p e s were a s s i g n e d t o a g i v e n squad. R e s u l t s o f t h e s e v e r i t y o f d i s t r e s s and d i f f i c u l t y o f judgement r a t i n g s c o r r o b o r a t e t h e f i n d i n g s w i t h r e g a r d t o d i s c r i m i n a b i l i t y . There was a s i g n i f i c a n t m o d e l i n g groups e f f e c t i n the d i s t r e s s r a t i n g a n a l y s i s . M u l t i p l e c o m p a r i s o n s r e v e a l e d t h a t no p a i r o f groups d i f f e r e d f r o m each o t h e r . T h i s s u g g e s t s t h a t r a t i n g s were r e l a t i v e l y homogeneous w i t h i n some p a i r o f the g r o u p s , r e l a t i v e t o a t h i r d group. O b s e r v e r s ' r a t i n g s o f d i s t r e s s were l o w e r when j u d g i n g b o t h t o l e r a n t and i n t o l e r a n t s u b j e c t s r e l a t i v e t o c o n t r o l s , s u g g e s t i n g t h a t t h e s e groups combined a c c o u n t e d f o r the m a r g i n a l e f f e c t . S i n c e d' was r e d u c e d i n b o t h g r o u p s , t h i s m a r g i n a l f i n d i n g m i r r o r s the p a t t e r n o f d i f f e r e n c e s w i t h r e s p e c t t o d i s c r i m i n a b i l i t y , and f u r t h e r s u p p o r t s the i n t e r p r e t a t i o n o f d_' as a measure o f e x p r e s s e d p a i n . A n a l y s e s o f o b s e r v e r s ' d i f f i c u l t y r a t i n g s r e v e a l e d t h a t s u b j e c t s i n t h e t o l e r a n t group were r e l i a b l y more d i f f i c u l t t o j u d g e t h a n were s u b j e c t s i n t h e o t h e r groups. Assuming t h a t o b s e r v e r s r e l i e d upon t h e o c c u r r e n c e o f a p a r t i c u l a r s e t o f cues t o base t h e i r r a t i n g s upon, i t w o u l d seem t h a t t h e s e cues tended t o o c c u r l e s s f r e -q u e n t l y among t o l e r a n t s u b j e c t s . T h i s f i n d i n g may r e f l e c t a f u r t h e r absence o f p a i n cues among t o l e r a n t s u b j e c t s i n a d d i t i o n t o m i r r o r i n g the marked r e d u c t i o n s i n t h e d i s c r i m i n a b i l i t y o f t h e i r b e h a v i o u r . E x p e r i m e n t a l s t u d i e s o f t h e e f f e c t s o f p a i n m o d u l a t i o n p r o c e d u r e s on humans have r e l i e d a l m o s t e x c l u s i v e l y upon v e r b a l c h a r a c t e r i z a t i o n s 93 o f t h e e x p e r i e n c e o f p a i n as a dependent v a r i a b l e . T h i s t r e n d i n t h e r e s e a r c h r e f l e c t s H i l g a r d ' s (1969) c o n c l u s i o n t h a t s u c h measures a r e h i g h l y d i s c r i m i n -a t i n g , r e p l i c a b l e , and: l a w f u l . However, i n v e s t i g a t o r s i n t e r e s t e d i n s o c i a l p r o c e s s e s r e l a t e d t o p a i n r e q u i r e s o m e t h i n g more, i n t h a t t h e i r c o n c e r n i s w i t h the s o c i a l b e h a v i o u r s i n d i c a t i v e o f p a i n , and t h e s o c i a l m i l i e u i n w h i c h p a i n and i t s i n d i c a n t s o c c u r . The p r e s e n t s t u d y has d e m o n s t r a t e d t h e u t i l i t y o f a methodology t h a t i s b a s e d d i r e c t l y upon t h e o v e r t , s o c i a l l y -r e l e v a n t p a i n b e h a v i o u r o f the i n d i v i d u a l , and i s r e a d i l y a d a p t a b l e t o many e x p e r i m e n t a l s e t t i n g s . The i m p a ct o f t h e v a r i a b l e s m a n i p u l a t e d i n t h i s s t u d y was a l m o s t ex-c l u s i v e l y upon d i s c r i m i n a b i l i t y . I t i s o f i n t e r e s t t o s p e c u l a t e about t h e t y p e s o f v a r i a b l e t h a t might be a s s o c i a t e d w i t h a l t e r a t i o n s i n o b s e r v e r s -d e c i s i o n r u l e s ( c r i t e r i a ) i n t h e t y p e o f t a s k employed i n t h i s s t u d y . E v a l u a -t i o n s o f t h e amount o f p a i n an i n d i v i d u a l i s e x p e r i e n c i n g a r e commonplace i n c l i n i c a l s e t t i n g s . Such e v a l u a t i o n s a r e b a s e d n o t o n l y upon t h e p r e s e n c e o f d i r e c t e v i d e n c e t h a t p a i n i s b e i n g e x p e r i e n c e d , b u t a l s o upon a v a i l a b l e back-ground i n f o r m a t i o n w i t h r e g a r d t o t h e i n d i v i d u a l , and the p r i o r e x p e r i e n c e o f t h e d i a g n o s t i c i a n . C e r t a i n t y p e s o f b a c k g r o u n d i n f o r m a t i o n a r e v e r y l i k e l y t o i n f l u e n c e the d i a g n o s t i c i a n ' s c r i t e r i o n f o r a c c e p t i n g e v i d e n c e t h a t a s i g n i f i c a n t amount o f p a i n i s p r e s e n t . Some examples o f t h e ty p e s o f b a c k g r o u n d i n f o r m a t i o n l i k e l y t o i n f l u e n c e judgements o f p a i n i n c l u d e : t h e p a t i e n t ' s e t h n i c b a c k g r o u n d , t h e h i s t o r y and c h r o n i c i t y o f t h e p r o b l e m , th e e m o t i o n a l o r p s y c h i a t r i c s t a t u s o f the p a t i e n t ( e . g . , i s s/he " n e u r o t i c " o r " s t o i c a l " ? ) , " p a y o f f s " a s s o c i a t e d w i t h e v i d e n c e o f p a i n s u c h as compensa-t i o n , " s e c o n d a r y g a i n s " , e t c . O t h e r v a r i a b l e s l i k e t he o b s e r v e r ' s e x p e r i -ence w i t h p a i n e x p r e s s i o n s a r e l i k e l y t o c o n t r i b u t e t o t h i s p r o c e s s . I t i s c o n c e i v a b l e , f o r example, t h a t i n d i v i d u a l s who l i v e i n a f a m i l y where one 94 member has a chronic pain problem may come to exhibit different criteria for evaluating pain as a function of their increased exposure to evidence of its presence. Indeed, in the present study, the finding that observers tended to employ more conservative criteria for reporting higher magnitudes of shock during their second viewing of each subject suggests that greater ex-perience with expressions of pain alters evaluators' decision rules for reporting its presence in others. Determining the contribution of such vari-ables to decisions regarding the presence or magnitude of pain is a critical step in understanding the complex phenomena of clinical pain and its diag-nosis. The methodology employed in the present study seems a particularly appropriate one for examining these issues. 95 E x p e r i m e n t 3. An i n v e s t i g a t i o n o f v i c a r i o u s i n f l u e n c e s on p a i n communications e m p l o y i n g n a t u r a l l y - o c c u r r i n g g r oups. R e s e a r c h on s o c i a l i n f l u e n c e v i a m o d e l i n g p r o c e d u r e s has had i m p o r t a n t consequences i n t h r e e r e s p e c t s . F i r s t , s u c h r e s e a r c h has u n c o v e r e d a major s o u r c e of v a r i a t i o n i n s o c i a l b e h a v i o u r . Second, m o d e l i n g r e s e a r c h has l e d d i r e c t l y t o t h e development o f p r o c e d u r e s e f f e c t i v e i n a l t e r i n g p r o b l e m a t i c b e h a v i o u r s , p a r t i c u l a r l y t h o s e c h a r a c t e r i z e d by a v o i d a n c e . T h i r d , f i n d i n g s f r o m m o d e l i n g r e s e a r c h have been employed w i t h i n t h e c o n t e x t of t h e o r e t i c a l a c c o u n t s of the o r i g i n s o f v a r i o u s forms o f s o c i a l / e m o t i o n a l b e h a v i o u r . As one example o f t h e l a t t e r , t h e a c q u i s i t i o n : ~ o f f e a r f u l a v o i d a n c e i n t h e n a t u r a l e n v ironment has been a t t r i b u t e d i n p a r t t o t h e m o d e l i n g o f f e a r f u l b e h a v i o u r e x h i b i t e d by o t h e r s i n s p e c i f i c s i t u a t i o n a l c o n t e x t s (Rachman, 1972; Bandura, 1969,1976). More germane to t h e p r e s e n t d i s c u s s i o n , F o r d y c e (1976a), C r a i g (Note 1, 1978b), and o t h e r s have a r g u e d t h a t d i f f e r e n c e s i n p a i n - r e l a t e d b e h a v i o u r c a n , i n p a r t , r e f l e c t v a r i a t i o n s i n s o c i a l i z a t i o n e x p e r i e n c e s . I n p a r t i c u l a r , r e l a t i v e t o l e r a n c e o r i n t o l e r a n c e f o r n o x i o u s s t i m u l a t i o n may l a r g e l y be t h e p r o d u c t o f e x p o s u r e t o o t h e r s d i s p l a y i n g r e l a t i v e t o l e r a n c e o r i n t o l e r a n c e o f t h e same s t i m u l a t i o n . S i m i l a r l y , s t y l i s t i c d i f f e r e n c e s i n t h e p a r t i c u l a r forms of p a i n b e h a v i o u r e m i t t e d i n s u c h c o n t e x t s may be m e d i a t e d by t h e m o d e l i n g p r o c e s s . 96 P r e v i o u s l a b o r a t o r y i n v e s t i g a t i o n s have been co n c e r n e d w i t h d e m o n s t r a t i n g t h e o c c u r r e n c e o f a m o d e l i n g e f f e c t , e v a l u a t i n g t h e impact o f m o d e l i n g on a v a r i e t y o f d i m e n s i o n s o f t h e e x p e r i e n c e o f p a i n , and e x a m i n i n g o t h e r i n f l u e n c e s t h a t may m o d u l a t e t h e e f f e c t s o f m o d e l i n g . These i n v e s t i g a t i o n s and t h e p r e c e d i n g s t u d i e s i n the p r e s e n t s e r i e s have de m o n s t r a t e d t h a t the e f f e c t s a r e r o b u s t and o b s e r v a b l e a c r o s s a v a r i e t y o f p a r a m e t e r s o f r e s p o n s e t o p a i n f u l s t i m u l a t i o n . I t has been s u g g e s t e d t h a t t h e s e f i n d i n g s a r e d e s c r i p t i v e o f n a t u r a l l y o c c u r r i n g v a r i a t i o n s i n p a i n b e h a v i o u r . However, r e l a t i v e l y l e s s a t t e n t i o n has been p a i d t o e x a m i n i n g t h i s " e t i o l o g i c a l " i m p l i c a t i o n . There i s a number o f e m p i r i c a l l a c u n a e i n a c c o u n t s o f t h e o r i g i n s o f d i f f e r e n c e s i n s t y l e o f r e s p o n s e t o p a i n f u l e v e n t s t h a t a r e based on m o d e l i n g r e s e a r c h . L a b o r a t o r y r e s e a r c h a l l o w s s t r i n g e n t c o n t r o l o v e r v a r i a b l e s t h a t have p o t e n t i a l o r known e f f e c t s on p a i n . However, the c o n t r o l s can e l i m i n a t e s o u r c e s of i n f l u e n c e t h a t may be i m p o r t a n t i n t h e n a t u r a l e n v i r o n m e n t . S o c i a l i n t e r a c t i o n p r o v i d e s f o r r e c i p r o c a l i n f l u e n c e i n t h a t i n d i v i d u a l s r e s p o n d i n g i n t h e same s i t u a t i o n a l c o n t e x t may come t o a l t e r t h e b e h a v i o u r o f one a n o t h e r ( S k i n n e r , 1953; B e l l , 1968; K a n f e r and Grimm, 1976; Bandura, 1978). T r a d i t i o n a l l y , however, m o d e l i n g r e s e a r c h has been d i r e c t e d toward e x a m i n a t i o n s o f u n i d i r e c -t i o n a l i n f l u e n c e . The p o s s i b i l i t y e x i s t s t h a t t h i s e x p e r i m e n t a l c o n s t r a i n t may l i m i t the r a n g e o f phenomena o b s e r v e d . That i s , an e x p e r i m e n t a l p a r a d i g m i n w h i c h m u t u a l i n f l u e n c e i s p r o v i d e d f o r may r e v e a l n o v e l o r u n u s u a l phenomena. A second t h e o r e t i c a l l i m i t a t i o n o f m o d e l i n g r e s e a r c h w i t h t h e par a d i g m used p r e v i o u s l y i s t h a t i t f a i l s t o a d e q u a t e l y p r e d i c t t h e r e l a t i v e power of v a r y i n g s t y l e s o f p a i n b e h a v i o u r . LThat i s , g i v e n a s i t u a t i o n i n w h i c h two i n d i v i d u a l s e x h i b i t i n g d i f f e r i n g l e v e l s o f n a t u r a l l y - o c c u r r i n g p a i n t o l e r a n c e have t h e p o t e n t i a l t o i n f l u e n c e one a n o t h e r , t h e r e i s no e m p i r i c a l b a s i s f o r p r e d i c t i n g whose b e h a v i o u r w i l l change more. I n t h e p r e s e n t s t u d y , th e p r e v i o u s l y employed m o d e l i n g p a r a d i g m was m o d i f i e d by s e l e c t i n g groups of s u b j e c t s who d i f f e r e d i n s t y l e s o f p a i n b e h a v i o u r under u n i n f l u e n c e d c o n d i t i o n s . S u b j e c t s who e x h i b i t e d r e l a t i v e t o l e r a n c e o r r e l a t i v e i n t o l e r a n c e f o r p a i n were chosen. These s u b j e c t s t h e n p a r t i c i p a t e d i n a second s e s s i o n matched i n p a i r s i n o r d e r t o examine whether i n f l u e n c e w o u l d be r e c i p r o c a l . D u r i n g t h e i n f l u e n c e s e s s i o n , p a i r s o f s u b j e c t s were e i t h e r s i m i l a r o r d i f f e r e n t i n terms of t h e i r p r e v i o u s l y a s c e r t a i n e d p a i n b e h a v i o u r . I t was e x p e c t e d t h a t s i m i l a r p a i r s would e x h i b i t more pronounced t e n d e n c i e s i n t h e d i r e c t i o n o f t h e i r o r i g i n a l s t y l e o f r e s p o n s e ( i . e . , t h a t i n t o l e r a n t s u b j e c t s would become more i n t o l e r a n t , and t h a t t o l e r a n t s u b j e c t s w o u l d become more t o l e r a n t ) . I n c o n t r a s t , i t was h y p o t h e s i z e d t h a t i n d i s s i m i l a r p a i r s , s u b j e c t s from each group w o u l d become more l i k e s u b j e c t s f r o m t h e o t h e r group ( i . e . , i n t o l e r a n t s u b j e c t s w o u l d become more t o l e r a n t , and t o l e r a n t s u b j e c t s would become more i n t o l e r a n t ) . T h i s paradigm a l s o a l l o w e d an e x a m i n a t i o n o f t h e r e l a t i v e i n f l u e n c i n g power o f t h e two forms of b e h a v i o u r . 98 METHOD S u b j e c t s . One hundred t w e n t y - s e v e n f e m a l e s were r e c r u i t e d by t e l e p h o n e from u n d e r g r a d u a t e P s y c h o l o g y c l a s s e s a t the U n i v e r s i t y o f B r i t i s h C o l umbia and were p a i d f o r t h e i r p a r t i c i p a t i o n i n a t w o - p a r t e x p e r i m e n t "on t h e t o p i c o f p e r c e p t i o n " . Mean age o f the s u b j e c t s was 19.1 (SD = 1 . 7 ) . A p p a r a t u s . The equipment employed was s i m i l a r t o t h a t used i n the f i r s t s t u d y e x c e p t t h a t i t was m o d i f i e d t o p r o v i d e t h e c a p a c i t y t o a d m i n i s t e r c u r r e n t t o two s u b j e c t s s i m u l t a n e o u s l y . P r o c e d u r e . S e s s i o n 1. Upon h e r a r r i v a l a t the l a b o r a t o r y , t h e s u b j e c t was s e a t e d i n a room a d j a c e n t t o the e x p e r i m e n t a l chamber and the e x p e r i m e n t e r r e a d t o h e r a s t a n d a r d s e t o f i n s t r u c t i o n s d e s c r i b i n g the n a t u r e o f t h e e x p e r i m e n t and p r o v i d e d a s s u r a n c e r e g a r d i n g the s a f e t y o f t h e t e c h n i q u e s . A f t e r a s s u r i n g the s u b j e c t t h a t h e r p a r t i c i p a t i o n was e n t i r e l y v o l u n t a r y , and t h a t the s t u d y c o u l d be t e r m i n a t e d a t any t i m e , o p p o r t u n i t y t o w i t h d r a w was p r o v i d e d . Three s u b j e c t s i n d i c a t e d t h e i r u n w i l l i n g n e s s t o c o n t i n u e a t t h i s p o i n t . A f u r t h e r 4 s u b j e c t s were e x c l u d e d because t h e y had n o t h a d a p h y s i c a l e x a m i n a t i o n w i t h i n t h e p a s t y e a r . S u b j e c t s w i l l i n g t o t a k e p a r t gave w r i t t e n c o n s e n t a t t h i s p o i n t , and were t h e n e s c o r t e d t o t h e e x p e r i -m e n t a l chamber where t h e f o l l o w i n g i n s t r u c t i o n s were r e a d : I am g o i n g t o p r e s e n t you w i t h a s e r i e s o f c u r r e n t s t h a t w i l l s t a r t a t u n d e t e c t a b l e l e v e l s and w i l l g r a d u a l l y i n c r e a s e . Your t a s k w i l l be t o i n d i c a t e how u n c o m f o r t a b l e each one f e e l s by a s s i g n i n g i t a number r a n g i n g from z e r o up t o 10 o r above. I n i t i a l l y , t h e c u r r e n t s w i l l be so low t h a t you w i l l p r o b a b l y f e e l n o t h i n g . I f t h i s i s t h e c a s e , the r a t i n g "0" f o r " u n d e t e c t a b l e " i s a p p r o p r i a t e . 99 T h e r e a f t e r , t h e y w i l l g r a d u a l l y i n c r e a s e i n i n -t e n s i t y and d i s c o m f o r t . I want you t o a s s i g n each one a number t h a t c o r r e s p o n d s t o t h e amount o f d i s c o m f o r t t h a t you f e e l . F o r example, i f y ou g i v e one c u r r e n t a r a t i n g o f "2" and t h e n a l a t e r one f e e l s t w i c e as u n c o m f o r t a b l e , a s s i g n the l a t e r one a r a t i n g o f "4" .... The c u r r e n t w i l l e v e n t u a l l y r e a c h a l e v e l t h a t you w o u l d d e s c r i b e as g i v i n g you a s e n s a t i o n o f p a i n . We w o u l d l i k e y o u t o g i v e t h a t c u r r e n t a r a t i n g o f 10 o r above. When you judge a c u r r e n t t o be p a i n f u l , and g i v e a r a t i n g o f 10 o r above, no more w i l l be g i v e n you. S u b j e c t s were t h e n p r o v i d e d w i t h t h e o p p o r t u n i t y t o ask q u e s t i o n s . When i t was c l e a r t h a t t h e s u b j e c t u n d e r s t o o d the n a t u r e o f h e r t a s k , the e l e c t r o d e was a t t a c h e d t o h e r l e f t f o r e a r m and p o s i t i o n e d as n e c e s s a r y t o reduc e t h e r e s i s t a n c e i n t h e s k i n - e l e c t r o d e c i r c u i t t o 5,000 ohms i n o r d e r t o p r o v i d e u n i f o r m i t y o f s t i m u l u s s t r e n g t h . F o l l o w i n g t h i s , t h e e x p e r i m e n t e r r e t r e a t e d b e h i n d t h e p a r t i t i o n and commenced t h e e x p e r i m e n t . Two a s c e n d i n g shock s e r i e s were a d m i n i s t e r e d , s t a r t i n g a t 0.0 mA and i n c r e a s i n g i n 0.5 mA i n c r e m e n t s u n t i l t h e s u b j e c t gave a r a t i n g o f 10 o r g r e a t e r . A t t h e end o f t h e second s e r i e s , t h e e x p e r i m e n t e r removed the e l e c t r o d e and e s c o r t e d t he s u b j e c t to t h e a d j o i n i n g room. She was t h e n t h a n k e d f o r h e r p a r t i c i p a t i o n and i n f o r m e d t h a t she might be c o n t a c t e d f o r a s e c o n d s e s s i o n . The second s e s s i o n was d e s c r i b e d as b e i n g b a s i c a l l y s i m i l a r " e x c e p t t h a t w e ' l l be t a k i n g some p h y s i o l o g i c a l r e c o r d i n g s as w e l l " . P r i o r t o l e a v i n g , t he s u b j e c t was a s k e d n o t t o t a l k about t h e e x p e r i m e n t t o h e r c l a s s m a t e s . Between the f i r s t and t h e second s e s s i o n o f t h e e x p e r i m e n t , average p a i n t h r e s h o l d s c o r e s f o r the f i r s t s e s s i o n were d e t e r m i n e d and s u b j e c t s r a n k e d on t h i s measure. S u b j e c t s e x h i b i t i n g a range o f p a i n t h r e s h o l d s c o r e s o f g r e a t e r t h a n 3.0 mA between t h e f i r s t and second s e r i e s were e l i m i n a t e d from the s t u d y . Three s u b j e c t s were e l i m i n a t e d f o r t h i s r e a s o n . T h e r e a f t e r , the e n t i r e group was d i v i d e d i n t o h i g h and low t h r e s h o l d groups by t a k i n g 100 t h e t o p 42 and t h e b o t t o m 40 s u b j e c t s o f t h e d i s t r i b u t i o n " ' " . S e s s i o n 2. I n the second s e s s i o n , s u b j e c t s were e i t h e r r u n i n p a i r s c o n s i s t i n g o f c o m b i n a t i o n s o f s u b j e c t s e x h i b i t i n g h i g h o r low p r e t e s t t h r e s -h o l d s , o r p a r t i c i p a t e d i n d i v i d u a l l y . Three t y p e s o f dyad were formed: h i g h -h i g h (HH), c o n s i s t i n g o f 22 s u b j e c t s (11 p a i r s ) from the h i g h group; h i g h - l o w ( H L ) , c o n s i s t i n g o f 10 s u b j e c t s each f r o m the h i g h and low groups ( s u b j e c t s i n t h i s group who had h i g h p r e t e s t t h r e s h o l d s were g i v e n the d e s i g n a t i o n HL-H, t h o s e f r o m the low group were d e s i g n a t e d HL-L) ; and l o w - l o w ( L L ) , con-s i s t i n g o f 20 s u b j e c t s from the low group. I n the eve n t t h a t one s u b j e c t o f a p a i r d i d n o t r e t u r n f o r a s c h e d u l e d a p p o i n t m e n t , the c o r r e s p o n d i n g member o f the p a i r was a u t o m a t i c a l l y a s s i g n e d t o a h i g h (HC) o r low (LC) c o n t r o l group, and was r u n i n d i v i d u a l l y . These groups were c o n s i d e r e d e s p e c i a l l y i m p o r t a n t i n o r d e r t o e s t i m a t e r e g r e s s i o n - t o w a r d - t h e - m e a n . Upon t h e i r r e t u r n f o r the second s e s s i o n , s u b j e c t s were c a s u a l l y i n -formed t h a t t h e y were g o i n g t o be r u n i n p a i r s i n o r d e r t o f i n i s h t h e e x p e r i m e n t more q u i c k l y . They were s e a t e d i n t h e e x p e r i m e n t a l chamber and had t h e f o l l o w i n g i n s t r u c t i o n s r e a d t o them: Today's s e s s i o n w i l l be v e r y s i m i l a r t o t h e f i r s t s e s s i o n . I w i l l a g a i n p r e s e n t y ou w i t h a s e r i e s o f c u r r e n t s t h a t w i l l s t a r t a t u n d e t e c t a b l e l e v e l s and w i l l g r a d u a l l y i n c r e a s e . Once a g a i n , I w o u l d l i k e you t o make p r o p o r t i o n a t e r a t i n g s o f t h e amount o f d i s c o m f o r t t h a t y ou f e e l , s t a r t i n g a t " z e r o " f o r u n d e t e c t a b l e and i n c r e a s i n g t h e r e a f t e r . You w i l l e v e n t u a l l y r e a c h a l e v e l t h a t y ou w o u l d d e s c r i b e as g i v i n g y o u a s e n s a t i o n o f p a i n . A s s i g n t h a t c u r r e n t a r a t i n g o f 10 o r g r e a t e r . A f t e r you g i v e a r a t i n g o f 10 o r above, we w o u l d l i k e .you t o c o n t i n u e t a k i n g c u r r e n t f o r as l o n g as p o s s i b l e , b u t t h e d e c i s i o n i s y o u r s t o s t o p a t any t i m e . F o r thos e c u r r e n t s t h a t o c c u r a f t e r you g i v e a r a t i n g o f 10, c o n t i n u e to make p r o p o r t i o n a t e r a t i n g s u s i n g any whole numbers 1. Owing t o an i n a d v e r t e n t s c h e d u l i n g e r r o r on t h e p a r t o f t h e e x p e r i m e n t e r t h e r e were two e x t r a s u b j e c t s from the h i g h group. 101 t h a t y ou l i k e . When you r e a c h the p o i n t where you don't w i s h t o a c c e p t any f u r t h e r s t i m u l i , g i v e t h a t c u r r e n t y o u r f i n a l r a t i n g , p u l l t he s w i t c h i n f r o n t o f y ou t o t h e o f f p o s i t i o n and no more w i l l be g i v e n t o you. Each a s c e n d i n g s e r i e s i n the f i r s t s e s s i o n was t e r m i n a t e d when t h e s u b j e c t f i r s t r e p o r t e d p a i n . I n the second s e s s i o n s u b j e c t s were en c o u r a g e d t o a c c e p t c u r r e n t s beyond p a i n t h r e s h o l d up t o t h e p o i n t where t h e y were un-w i l l i n g t o c o n t i n u e . P r i o r t o t e s t i n g , t h e e x p e r i m e n t e r a s k e d one s u b j e c t t o make h e r r a t i n g f i r s t . F o r h a l f o f the dyads, the s u b j e c t h a v i n g the h i g h e r p r e t e s t t h r e s h o l d s c o r e gave h e r r a t i n g f i r s t , w h i l e f o r the o t h e r h a l f , the l o w e r member o f t h e p a i r gave h e r r a t i n g f i r s t . I n o r d e r t o m a i n t a i n t h e r u s e t h a t i n t h i s s e s s i o n t h e c o n c e r n was w i t h p h y s i o l o g i c a l measures, a "dummy" photoplet/hyjsmograph was a t t a c h e d ; ^ t o each s u b j e c t ' s r i g h t i n d e x i n d e x f i n g e r and i t s o p e r a t i o n was d e s c r i b e d . P r i o r t o commencing the shock s e r i e s , the e x p e r i m e n t e r e x c u s e d h i m s e l f t o " s e t a few t h i n g s up on the p o l y g r a p h " , and l e f t t h e room f o r a p p r o x i m a t e l y 30 s e c . Upon r e t u r n i n g , 4 s e r i e s o f e l e c t r i c s h o c k s were a d m i n i s t e r e d t o the s u b j e c t s . Each s t a r t e d a t 0.0 mA and i n c r e a s e d i n 0.'5 ( mA s t e p s u n t i l b o t h s u b j e c t s had r e q u e s t e d t e r m i n a t i o n o f the s e r i e s . A t the end o f the s e s s i o n , the e l e c t r o d e s and pleth'ys'niogfaphs -' wefeT removed, and s u b j e c t s were e s c o r t e d t o t h e a d j o i n i n g room where t h e y c o m p l e t e d p o s t - e x p e r i m e n t a l q u e s t i o n n a i r e s . When b o t h s u b j e c t s had f i n i s h e d t h e ques-t i o n n a i r e s , t h e y were f u l l y d e b r i e f e d and a l l q u e s t i o n s t h e y had about the s t u d y were answered. 102 RESULTS Pairi t h r e s h o l d . Pain t h r e s h o l d data were analysed according to a 6 (Groups) x 6 (Shock Series) ANOVA design w i t h repeated measurements on the Series v a r i a b l e . The f i r s t two l e v e l s of the Series f a c t o r represented per-formance during the p r e t e s t s e s s i o n , w h i l e the f o l l o w i n g 4 l e v e l s represented performance under i n f l u e n c e c o n d i t i o n s f o r subjects i n groups HH, HLH, HLL, and LL or during re-assessment f o r subjects i n groups HC and LC. Results of the ANOVA i n d i c a t e d a s i g n i f i c a n t o v e r a l l between groups main e f f e c t , _F(5,76) = 27.67, p_ < .01, and a s i g n i f i c a n t Groups x Series i n t e r a c t i o n , F(25,380) = 3.81, £ < .01. The main e f f e c t f o r Groups was of l i t t l e i n t e r e s t s i n c e group assignment had been conducted by s e l e c t i n g subjects from extremes of the d i s t r i b u t i o n . Of more i n t e r e s t was the pre-d i c t e d i n t e r a c t i o n (represented i n Figure 3:1) of Groups x Shock Series which was f u r t h e r i n v e s t i g a t e d v i a a s e r i e s of planned orthogonal j t - t e s t s . Sub-sequent analyses were performed i n order to determine which groups e x h i b i t e d changes from Session 1 to Session 2, and to compare t h r e s h o l d l e v e l s under i n f l u e n c e c o n d i t i o n s . These l a t t e r between-group analyses provided informa-t i o n on which groups e x h i b i t e d d i f f e r e n t i a l changes. The f i r s t set of comparisons examined change from S e r i e s 1 and 2 (preassessment session) to Series 3 through 6 ( i n f l u e n c e session) at each l e v e l of the groups v a r i a b l e . The o v e r a l l t> values f o r each of these com-parisons are presented i n Table 3:1. The r e s u l t s of these analyses confirm that the decrease i n pa i n t h r e s h o l d value observed i n groups HL-H from the preassessment to the i n f l u e n c e session and the increases observed i n groups HL-L, LL, and LC were s t a t i s t i c a l l y r e l i a b l e . 103 Figure 3: 1. Mean intensity of current provoking a rating of "10" (pain threshold) overall shock series in Session 1 (pretest) and Session 2 (tn<-fluence session) for subjects in a l l groups, 104 T a b l e 3:1 R e s u l t s o f P l a n n e d O r t h o g o n a l Comparisons f o r P a i n T h r e s h o l d Data E r r o r t - R a t i o Comparison E s t i m a t e Denominator t V a l u e S 1 ' S 2 " 1.25 Group 1 (HC) (SxS w i t h i n groups) 1.23 0.33 > .10 S 1 ' S 2 " S 3 ' S 4 ' S 5 ' S 6 a t Group 2 (HH) 1.25 0.83 1.35 > .10 V S 2 " S 3 ' S 4 ' S 5 ' S 6 a t Group 3 (HL-H) 1.25 1.23 6.52 < .01 V S 2 " S 3 ' S 4 ' S 5 ' S 6 a t Group 4 (HL-L) 1.25 1.23 -4.93 < .01 S 1 ' S 2 " S 3 ' W S 6 a t Group 5 (LL) 1.25 0.87 -3.66 < .01 S 1 ' S 2 " S 3 ' S 4 ! S 4 ' S 6 a t Group 6 (LC) 1.25 1.23 -2.12 < .05 HC, HH vs HL-H a t S e r i e s 3 2.62 1.20 2.35 < .05 (Ss w i t h i n G SxSs w i t h i n G, p o o l e d ) HC, HH vs HL-H a t S e r i e s 4 2.62 1.20 1.56 < .05 HC, HH vs HL-H a t S e r i e s 5 2.62 1.20 2.22 < .05 HC, HH vs HL-H a t S e r i e s 6 2.62 1.20 2.45 < .05 c o n t i n u e d 105 T a b l e 3:1 c o n t i n u e d E r r o r _ t - R a t i o Comparison E s t i m a t e Denominator t V a l u e HC vs HH a t S e r i e s 3 2.62 0.62 0.14 > .10 HC v s HH a t S e r i e s 4 2.62 0.62 0.05 > .10 HC v s HH a t S e r i e s 5 2.62 0.62 1.52 > .05 HC v HH a t S e r i e s 6 2.62 0.62 1.42 > .05 LC, LL vs HL-L a t S e r i e s 3 2.62 0.62 0.25 > .10 LC, LL vs HL-L a t S e r i e s 4 2.62 0.62 -1.16 > .10 LC, LL v s HL-L a t S e r i e s 5 2.62 0.62 -0.85 > .10 LC, LL vs HL-L a t S e r i e s 6 2.62 0.62 -0.62 > .10 LC vs LL a t S e r i e s 3 2.62 0.62 0.96 > • .10 LC vs LL a t S e r i e s 4 2.62 0.62 0.32 > .10 LC vs LL a t S e r i e s 5 2.62 0.62 0.04 > .10 LC vs. L L a t S e r i e s 6 2.62 0.62 0.24 > .10 N o te: HC = H i g h C o n t r o l , HH = H i g h - H i g h , HL-H = High-Low ( H i g h ) , HH-L = High-Low (Low), LL = Low-Low, LC = Low C o n t r o l . Denominators o f t - r a t i o s v a r y when comparisons a r e b a s e d upon d i f f e r e n t n's. F o r c o n s e r v a t i v e _ t - t e s t o f between group com-p a r i s o n s , t h e c r i t i c a l v a l u e o f t ' ,„ = 1.98. — a / 2 106 The second s e t o f comparisons was p e r f o r m e d a t each l e v e l o f t h e S e r i e s f a c t o r d u r i n g . t h e i n f l u e n c e s e s s i o n . F o u r c o n t r a s t s were examined a t each l e v e l : (1) Groups HC and HH vs Group HL-H, (2) Group HC vs Group HH, (3) groups LC and LL vs Group HL-L, (4) groups LC vs group LL. Denominators o f _ t - r a t i o s f o r each o f t h e s e c o n t r a s t s employed the p o o l e d between s u b j e c t -w i t h i n e r r o r t e r m recommended by K i r k ( 1 9 6 8 ) . Cochran and Cox's c o n s e r v a t i v e _t ( K i r k , 1968) was employed t o e v a l u a t e the r e l i a b i l i t y o f between-group d i f f e r e n c e s . E x a m i n a t i o n o f t h e r e s u l t s o f t h e s e a n a l y s e s ( T a b l e 3:1) i n d i -c a t e d t h a t o n l y s u b j e c t s i n group HL-H e x h i b i t e d s i g n i f i c a n t d i f f e r e n c e s f r o m s u b j e c t s i n groups HC and HH combined. These d i f f e r e n c e s o c c u r r e d a t S e r i e s 3, 5, and 6. None o f the o t h e r between-group comparisons approached s t a t i s -t i c a l r e l i a b i l i t y . I n sum, the f o l l o w i n g p a t t e r n was o b s e r v e d i n t h e a n a l y s e s of p a i n t h r e s h o l d d a t a . Among h i g h p a i n t h r e s h o l d g r o u p s , o n l y t h o s e s u b j e c t s exposed t o a s u b j e c t h a v i n g a low p r e a s s e s s m e n t t h r e s h o l d e x h i b i t e d change f r o m t h e p r e a s s e s s m e n t to t h e i n f l u e n c e s e s s i o n . T h i s change i n v o l v e d an o v e r a l l de-c r e a s e i n p a i n t h r e s h o l d . A l l groups o f s u b j e c t s who e x h i b i t e d low p r e a s s e s s -ment p a i n t h r e s h o l d v a l u e s e x h i b i t e d i n c r e a s e s i n r e p o r t e d p a i n t h r e s h o l d f rom t h e p r e a s s e s s m e n t t o the i n f l u e n c e s e s s i o n . Only t h e changes o b s e r v e d i n group HL-H r e s u l t e d i n s i g n i f i c a n t between-group d i f f e r e n c e s d u r i n g the i n f l u e n c e s e s s i o n . P a i n t o l e r a n c e . I n S e s s i o n 2, s u b j e c t s r a t e d s t i m u l i beyond p a i n t h r e s h o l d l e v e l s t o p a i n t o l e r a n c e . These d a t a were a n a l y z e d v i a a 6 (Groups) x 4 (Shock S e r i e s ) ANOVA w i t h r e p e a t e d measures on t h e Shock S e r i e s f a c t o r . The outcome o f t h i s a n a l y s i s i n d i c a t e d t h a t t h e r e was a s i g n i f i c a n t Groups e f f e c t , j?(5,76) = 7.75, p_ < .01, and a s i g n i f i c a n t Groups x Shock S e r i e s , F_(15,228) = 1.81, £ < .05. Mean p a i n t o l e r a n c e v a l u e s f o r each group 107 a t each l e v e l o f t h e Shock S e r i e s v a r i a b l e a r e shown i n F i g u r e 3:2. As w i t h p a i n t h r e s h o l d d a t a , t h e o v e r a l l Groups e f f e c t was o f l i t t l e i n t e r e s t , s i n c e i t w o u l d l a r g e l y have r e f l e c t e d the p r o c e s s o f s e l e c t i n g s u b j e c t s f r o m ex-tremes o f t h e d i s t r i b u t i o n o f p a i n t h r e s h o l d s c o r e s . Of more i n t e r e s t were comparisons w i t h i n t h e h i g h and low p a i n t h r e s h o l d groups. O r t h o g o n a l j t - t e s t s were c o n d u c t e d a t each l e v e l o f t h e Shock S e r i e s v a r i a b l e f o r t h e f o l l o w i n g between group c o m p a r i s o n s : (1) HC and HH vs HL-H, (2) HC vs HH, (3) LC and LL v s HL-L, (4) LC vs LL. As w i t h the p r e v i o u s a n a l y s e s , a p o o l e d between-s u b j e c t - w i t h i n - s u b j e c t e r r o r t e r m was employed and s t a t i s t i c a l r e l i a b i l i t y was a s s e s s e d a t a c o n s e r v a t i v e _t'.05/2 v a l u e o f 1.99. None o f t h e o r t h o g o n a l c omparisons exceeded t h i s c r i t i c a l _ t - v a l u e . I t was l i k e l y , t h e r e f o r e , t h a t the s i g n i f i c a n t i n t e r a c t i o n d e r i v e d from a c o n t r a s t n o t i n c l u d e d i n t h e o r i g i n a l s e t o f o r t h o g o n a l comparisons s e l e c t e d f o r a n a l y s i s . I n s p e c t i o n o f t h e means s u g g e s t e d t h a t d i f f e r e n c e s between groups HC and HL-H may have been p a r t i a l l y r e s p o n s i b l e f o r t h e s i g n i f i c a n t i n t e r a c t i o n e f f e c t . To e v a l u a t e t h i s , means f o r groups HC and HL-H were compared a t each l e v e l o f the s e r i e s v a r i a b l e u s i n g Tukey's p r o c e d u r e . The e r r o r t e r m f o r t h e s e con-t r a s t s p o o l e d b e t w e e n - s u b j e c t and w i t h i n s u b j e c t e r r o r v a r i a n c e , and s i g n i -f i c a n c e was e v a l u a t e d a t a c o n s e r v a t i v e v a l u e f o r Tukey's t e s t o f 2.82 ( K i r k , 1968). The o n l y d i f f e r e n c e between groups t h a t exceeded t h i s v a l u e o c c u r r e d a t Shock S e r i e s 6 (q_ = 3.10), where the mean f o r group HL-H (8.60 mA) was r e l i a b l y l o w e r t h a n t h a t f o r group HC (10.80 mA). I n s p e c t i o n o f t h e group means a l s o s u g g e s t e d t h a t a t Shock S e r i e s 4 t h e d i f f e r e n c e between group LC and group HL-L may have been r e l i a b l e . E v a l u a t i o n o f t h i s p o s s i b i l -i t y by Tukey's t e s t i n d i c a t e d . t h a t t h i s was n o t the case s i n c e t h e o b t a i n e d c[ v a l u e f o r t h i s c o m p a r i s o n ( 1.61) f a i l e d t o e x c e e d t h e c r i t i c a l v a l u e f o r r e j e c t i o n o f t h e n u l l h y p o t h e s i s . 108 Figure 3: 2, Mean intensity of current at the point where subjects terminated each shock series (pain tolerance) during Session 2 for a l l groups. 109 Results of pain tolerance analyses may be summarized as follows. No between group differences were obtained f o r any of the low pain threshold groups. Among high pain threshold groups, the only s i g n i f i c a n t e f f e c t appeared to derive from subjects i n group HL-H e x h i b i t i n g a progressive decline i n pain tolerance values over the 4 shock seri e s of the influence session. This resulted i n the mean pain threshold value for group HL-L being s i g n i f i c a n t l y lower than that f o r subjects i n group HC at the le a s t shock s e r i e s . However, subjects i n group HL-H could not be d i f f e r e n t i a t e d from subjects i n group HH on t h e i r pain tolerance values. Thus there was evidence that exposure to subjects having a low-preassessment threshold resulted i n a decrease i n pain tolerance f o r subjects e x h i b i t i n g i n i t i a l l y high pain threshold values. The e f f e c t , however, was not p a r t i c u l a r l y strong, i n that i t could only be observed during the l a s t shock s e r i e s . 110 DISCUSSION The major impact of the experimental group pairings was evident on the pain threshold measure that the groups were o r i g i n a l l y d i f f e r e n t i a t e d on. Low threshold subjects exhibited a general tendency f o r t h e i r pain threshold l e v e l s to increase, regardless of the threshold l e v e l of the subject that they were paired with, or whether, i n f a c t , they had a companion at a l l . High threshold subjects, however, exhibited d i f f e r e n t i a l changes depending on group assignment. When subjects with high pretest thresholds were run i n d i v i d u a l l y , or with a companion who also exhibited a high pretest thres-hold, t h e i r pain threshold l e v e l s remained stable. These two groups could not be d i f f e r e n t i a t e d from each other i n terms of pain threshold l e v e l s during session 2. However, when a subject e x h i b i t i n g a high pretest pain threshold p a r t i c i p a t e d concurrently with a subject having a low pretest threshold, high subjects showed marked and s i g n i f i c a n t reductions i n t h e i r pain thres-hold values. Low pretest pain threshold subjects i n t h i s group showed i n -creases i n pain threshold l e v e l s . However, the tendency f o r painthresholds of a l l subjects having a low pretest threshold to increase represents strong evidence that being exposed to a high threshold companion was not responsible for t h i s change. Conversely, the d i f f e r e n t i a l pattern of change among high pretest threshold subjects provides strong evidence that exposure of high threshold subjects to the behaviour of low threshold subjects was s p e c i f i -c a l l y responsible f o r the threshold reduction observed among high subjects. The o v e r a l l outcome of t h i s study was not consistent with the hypothesis of r e c i p r o c a l influence. Rather, s o c i a l influence i n th i s s e t t i n g seemed quite c l e a r l y to be u n i d i r e c t i o n a l . Low threshold subjects influenced high threshold subjects to report pain sooner than, i t seems, they o r d i n a r i l y I l l w o u l d have. The b e h a v i o u r o f h i g h t h r e s h o l d s u b j e c t s , on t h e o t h e r hand, had no d e m o n s t r a b l e impact on t h e b e h a v i o u r o f low t h r e s h o l d s u b j e c t s . Re-s u l t s o f t h e a n a l y s i s o f p a i n t o l e r a n c e d a t a were c o n s i s t e n t i n t h i s r e g a r d ; however, t h e e f f e c t was c o n s i d e r a b l y weaker and l e s s c l e a r c u t . The f a c t t h a t a c l e a r p a i n - t h r e s h o l d i n c r e m e n t r e s u l t i n g f r o m e x p o s u r e o f l o w - t h r e s h o l d s u b j e c t s t o h i g h t h r e s h o l d s u b j e c t s was n o t d e monstrated i s t r o u b l e s o m e , e s p e c i a l l y i n l i g h t o f the c o n s i s t e n t l y - r e p o r t e d e f f i c a c y o f m o d e l i n g p r o c e d u r e s i n the r e d u c t i o n o f a v o i d a n c e b e h a v i o u r (Bandura, B l a n c h a r d and R i t t e r , 1969; Bandura, Grusec and Menlove, 1967; Bandura and M enlove, 1968; Geer and T u r t l e t a u b , 1967; Bandura, J e f f r e y and W r i g h t , 1974; Rachman, 1972). T h i s d i s c r e p a n c y might be a c c o u n t e d f o r i n a number o f d i f f e r e n t ways. F o r one, i t i s i m p o r t a n t t o emphasize t h a t w h i l e a d i f f e r e n -t i a l i n c r e m e n t i n p a i n t h r e s h o l d among l o w - t h r e s h o l d s u b j e c t s e xposed t o h i g h - t h r e s h o l d s u b j e c t s was n o t o b s e r v e d , a g e n e r a l i n c r e m e n t among a l l low-t h r e s h o l d s u b j e c t s was. The p r o c e s s r e s p o n s i b l e f o r t h i s g e n e r a l change may s i m p l y have been more p o w e r f u l t h a n any p r o c e s s a c t i v a t e d by e x p o s u r e t o a h i g h t h r e s h o l d s u b j e c t and may have masked any e f f e c t o f the l a t t e r . Some s p e c u l a t i o n s r e g a r d i n g the p r o c e s s ( e s ) r e s p o n s i b l e f o r t h e g e n e r a l i n c r e m e n t among low t h r e s h o l d s u b j e c t s w i l l be e l a b o r a t e d below. W h i l e p l a u s i b l e , t h i s e x p l a n a t i o n h i g h l i g h t s a n o t h e r i s s u e . I n s p i t e o f t h e f a c t t h a t l o w - t h r e s h o l d s u b j e c t s e x h i b i t e d a g e n e r a l i n c r e m e n t i n p a i n t h r e s h o l d s the magnitude o f t h i s i n c r e m e n t was n o t so g r e a t as t o e l e v a t e the mean o f any o f t h e low-t h r e s h o l d groups t o t h e same l e v e l as any o f the h i g h - t h r e s h o l d groups. W h i l e many p r e v i o u s s t u d i e s have d e m o n s t r a t e d t h a t m o d e l i n g t r e a t m e n t s e f f e c -t i v e l y r educe a v e r s i v e l y - m o t i v a t e d b e h a v i o r , i t i s n o t always c l e a r t h a t the e f f e c t of t h e t r e a t m e n t s a r e s u f f i c i e n t l y p o w e r f u l t h a t the s u b j e c t s ' be-h a v i o u r s approach n o r m a t i v e l e v e l s . Thus, m o d e l i n g may be e f f e c t i v e i n 112 r e d u c i n g a v o i d a n c e b e h a v i o u r s , b u t i t may n o t e l i m i n a t e them. The p l a u s i b i l i t y o f t h e "masking" e x p l a n a t i o n o f the outcome o f the p r e s e n t s t u d y i s undermined by t h e r e p e a t e d d e m o n s t r a t i o n i n p r e v i o u s s t u d i e s o f m o d e l i n g e f f e c t s on p a i n o f t h e r e m a r k a b l y p o w e r f u l i n f l u e n c e o f e x p o s u r e t o a t o l e r a n t model among u n s e l e c t e d groups o f s u b j e c t s . The f a c t t h a t i n t h e p r e s e n t s t u d y s e l e c t e d groups were employed p o i n t s t o a n o t h e r p o t e n t i a l e x p l a n a t i o n o f the r e l a t i v e i n e f f e c t i v e n e s s o f e x p o s u r e t o h i g h t h r e s h o l d s u b j e c t s . I n d i v i d u a l s who a r e p a r t i c u l a r l y r e a c t i v e t o n o x i o u s s t i m u l a t i o n may s i m p l y have u n c h a r a c t e r i s t i c a l l y s t a b l e r e s p o n s e s t y l e s t h a t a r e c a p a b l e o f e x h i b i t i n g change w i t h i n r e l a t i v e l y n a r row bounds. M i s c h e l (1973) i n d i s c u s s i n g t r a i t c o n c e p t s p o i n t e d out t h a t the d e m o n s t r a b l e p l a s t i c i t y and s i t u a t i o n a l s p e c i f i t y o f human b e h a v i o u r c a l l s i n t o q u e s t i o n t h e g e n e r a l u t i l i t y and v a l i d i t y o f s u c h c o n c e p t s . However i n c e r t a i n extreme c a s e s , n o t a b l y t h o s e c h a r a c t e r i z e d as p a t h o l o g i c a l , e v i d e n c e f a v o r s the n o t i o n t h a t b e h a v i o r a l s t y l e s a r e r e l a t i v e l y s t a b l e and g e n e r a l ( M i s c h e l , 1 9 7 3 ) . T h i s e x t r e m e - c a s e s t a b i l i t y n o t i o n s u g g e s t s t h a t enhanced p a i n t h r e s h o l d s may have been o b s e r v e d had a midrange group, c o m p r i s e d o f s u b j e c t s e x h i b i t i n g n o r m a t i v e p a i n t h r e s h o l d l e v e l s , been i n c l u d e d i n t h e s t u d y . Y e t a n o t h e r p o s s i b l e e x p l a n a t i o n f o r the p r e s e n t f i n d i n g s p r i n g s d i r e c t l y f r o m the f a c t t h a t r e l a t i v e l y p a i n - i n t o l e r a n t b e h a v i o u r was c l e a r l y a more p o w e r f u l s o u r c e o f i n f l u e n c e t h a n r e l a t i v e t o l e r a n c e . H i g h t h r e s h o l d s u b j e c t s , upon b e i n g e xposed t o l o w - t h r e s h o l d s u b j e c t s , r a t h e r r a p i d l y came t o a p p r o x i -mate t h e i r b e h a v i o u r . Thus, b e h a v i o u r o f " h i g h s " became l e s s d i s c r e p a n t f r o m the b e h a v i o u r o f " l o w s " t h a n i t w o u l d have been had, f o r example, a t o l e r a n t model who adopted a f i x e d r o l e been employed. T h i s r e l a t i v e power a c c o u n t seems t o match the d a t a most c l o s e l y , and i s t h e r e f o r e f a v o r a b l e . 113 The p r o b l e m o f a c c o u n t i n g f o r the g e n e r a l i n c r e m e n t i n p a i n t h r e s h o l d v a l u e s among a l l l o w - t h r e s h o l d groups s t i l l r e m a i n s . As one p o s s i b i l i t y , a d i f f e r e n t i a l a n x i e t y - r e d u c t i o n h y p o t h e s i s c o u l d be advanced, s u g g e s t i n g t h a t low t h r e s h o l d s u b j e c t s e x p e r i e n c e d l e s s a n x i e t y d u r i n g S e s s i o n 2 t h a n d u r i n g S e s s i o n 1. A l a r g e number o f s t u d i e s have documented the p a i n e n h a n c i n g e f f e c t s o f a n x i e t y and t h e n o t i o n t h a t a n x i e t y - r e d u c t i o n m e d i a t e s many p a i n -r e d u c i n g i n t e r v e n t i o n s i s w e l l i n g r a i n e d i n t h e l i t e r a t u r e ( A v e r i l l , 1973; J o hnson, 1973; Johnson & L e v e n t h a l , 1973; M a r t i n e z - U r r u t i a , 1975; Staub & K e l l e t t , 1972; S t e r n b a c h , 1968, 1974). However, such an h y p o t h e s i s seems cumbersome. A l t e r n a t i v e l y , a p p e a l can be made t o Marks' (1975) a c c o u n t o f t h e c r i t i -c a l f a c t o r s i n v o l v e d i n f e a r - r e d u c t i o n t e c h n i q u e s . Marks has p r o v i d e d a f o r m u l a t i o n s u g g e s t i n g t h a t the c r i t i c a l v a r i a b l e common t o t h e w i d e : v a r i e t y o f t e c h n i q u e s e f f e c t i v e f o r f e a r - r e d u c t i o n i s s i m p l e e x p o s u r e t o the f e a r e d s i t u a t i o n . The s u b j e c t s i n t h e p r e s e n t s t u d y had the b e n e f i t o f p r i o r ex-p o s u r e t o t h e e x p e r i m e n t a l s i t u a t i o n when t h e y r e t u r n e d f o r S e s s i o n 2. I t seems p o s s i b l e t h a t t h i s s i m p l e p r e - e x p o s u r e may have a c c o u n t e d f o r t h e i n -c r e a s e i n p a i n t h r e s h o l d s i n S e s s i o n 2. S i n c e s u b j e c t s i n t h e h i g h t h r e s h o l d groups were a l r e a d y a t t h e upper extreme of t h e p a i n t h r e s h o l d d i s t r i b u t i o n , s u c h an e x p o s u r e e f f e c t may have been e l i m i n a t e d due t o t h e o p e r a t i o n o f a c e i l i n g e f f e c t . H i g h t h r e s h o l d s u b j e c t s who p a r t i c i p a t e d a l o n e i n t h e s econd s e s s i o n o r c o n c u r r e n t l y w i t h a n o t h e r h i g h t h r e s h o l d s u b j e c t , e x h i b i t e d no changes i n t h e i r p a i n t h r e s h o l d l e v e l s . I t i s i m p o r t a n t t o n o t e t h a t t h e s e a r e , i n f a c t , p o s i t i v e f i n d i n g s i n t h a t they r u l e out r e g r e s s i o n t o w a r d the mean as an e x p l a n a t i o n f o r o t h e r f i n d i n g s i n the s t u d y . The f a c t t h a t h i g h - h i g h p a i r s d i d n o t e x h i b i t an e l e v a t i o n i n p a i n t h r e s h o l d o r t o l e r a n c e i s l i k e l y a t t r i -114 b u t a b l e t o a c e i l i n g e f f e c t . The p r e s e n t f i n d i n g s have s i g n i f i c a n t t h e o r e t i c a l i m p l i c a t i o n s i n a t l e a s t two r e s p e c t s . F i r s t , t h e y e x t e n d t h e g e n e r a l i t y o f p r e v i o u s demonstra-t i o n s o f s o c i a l m o d e l i n g i n f l u e n c e s on p a i n b e h a v i o u r by showing t h a t n a t u r a l l y -o c c u r r i n g v a r i a t i o n s i n p a i n b e h a v i o u r can p r o v i d e s i g n i f i c a n t s o u r c e s o f i n f l u e n c e o v e r t h e p a i n b e h a v i o u r o f o t h e r s . W h i l e r i g o r o u s c o n t r o l o v e r t h e r o l e s e n a c t e d by models i n p r e v i o u s s t u d i e s was r e q u i r e d i n o r d e r t o demon-s t r a t e the p r e s e n c e o f an e f f e c t , i t c o u l d have been ar g u e d t h a t the p r o c e d u r e s were s u f f i c i e n t l y a r t i f i c i a l t o q u e s t i o n t h e a p p l i c a b i l i t y o f t h e f i n d i n g s t o s o c i a l i n f l u e n c e p r o c e s s e s i n t h e n a t u r a l e n v i r o n m e n t . S i n c e n a t u r a l l y - o c c u r r i n g p a i n b e h a v i o u r had' a " - s i g n i f i c a n t i n f l u e n c e ' o n t h e b e h a v i o u r of o t h e r s , ' i t \ seems r e a s o n a b l e t o s p e c u l a t e t h a t s i m i l a r p r o c e s s e s might ' o p e r a t e . i n " : ./s n a t u r a l s e t t i n g s . ',-. Second, t h e f i n d i n g o f a d i f f e r e n t i a l i m p a c t o f r e l a t i v e l y p a i n i n t o l e r a n t b e h a v i o r upon r e l a t i v e l y t o l e r a n t b e h a v i o u r p r o v i d e s p a r t i c u l a r s u p p o r t f o r s p e c u l a t i o n s t h a t s o c i a l m o d e l i n g i n f l u e n c e s p l a y a s i g n i f i c a n t r o l e i n the g e n e r a t i o n o f r e l a t i v e i n t o l e r a n c e f o r p a i n i n the n a t u r a l e n v i r o n m e n t , and q u i t e p o s s i b l y ^ i n t h e o r i g i n o f p a t h o l o g i c a l p a i n b e h a v i o u r ( C r a i g , 1975, 1978, F o r d y c e , 1976b). T h i s f i n d i n g i s a l s o c o n s i s t e n t w i t h s p e c u l a t i o n s t h a t m o d e l i n g v a r i a b l e s a r e c r i t i c a l a g e n t s i n t h e e t i o l o g y o f o t h e r d e v i a n t forms o f a v o i d a n c e b e h a v i o r . The f i n d i n g t h a t i n t o l e r a n t b e h a v i o u r i s d i f -f e r e n t i a l l y p o w e r f u l a l s o r a i s e s the i n t e r e s t i n g p r o s p e c t t h a t m o d e l i n g , l i k e o t h e r forms o f l e a r n i n g , i s c o n s t r a i n e d ( c f . Hinde and S t e v e n s o n - H i n d e , 1973). I n s p i t e o f the r e p o r t e d h i g h c o r r e l a t i o n between p a i n t h r e s h o l d and p a i n t o l e r a n c e v a l u e s u s i n g v i r t u a l l y i d e n t i c a l s t i m u l a t i o n t e c h n i q u e s t o t h o s e employed i n t h e p r e s e n t s t u d y ( P r i c e and T u r s k y , 1 9 7 5 ) , t h e outcome o f t h e p a i n t o l e r a n c e a n a l y s i s was n o t n e a r l y as i m p r e s s i v e as t h e outcome o f 115 the p a i n t h r e s h o l d a n a l y s i s . H i g h t h r e s h o l d s u b j e c t s exposed t o low t h r e s -h o l d s u b j e c t s e x h i b i t e d r e d u c e d p a i n t o l e r a n c e r e l a t i v e t o h i g h c o n t r o l sub-j e c t s , t h i s d i f f e r e n c e was o n l y e v i d e n t on the l a s t t r i a l o f t h e i n f l u e n c e s e s s i o n . W h i l e t h i s f i n d i n g i s c o n s i s t e n t w i t h t h e outcome o f t h e p a i n t h r e s h o l d a n a l y s i s , and s u g g e s t s t h a t the c o n c l u s i o n s d e r i v e d f r o m the l a t t e r a r e g e n e r a l i z a b l e t o p a i n t o l e r a n c e , the e f f e c t was e v i d e n t l y q u i t e weak. Two p o i n t s must be t a k e n i n t o a c c o u n t i n r e l a t i o n t o t h i s p r o blem. F i r s t , w h i l e P r i c e and Tu r s k y (1975) r e p o r t e d a s t r o n g r e l a t i o n s h i p between t h r e s h o l d and t o l e r a n c e measures, the r e l a t i o n s h i p was, o f c o u r s e , n o t p e r f e c t . I t might be e x p e c t e d t h a t the e r r o r i n v o l v e d i n t h e r e l a t i o n s h i p might be magni-f i e d when v a r i a b l e s a r e m a n i p u l a t e d i n o r d e r t o i n v e s t i g a t e m o d u l a t i o n o f the measures. Second measures o f t h e s t r e n g t h o f a r e l a t i o n s h i p t e n d t o t a k e on l o w e r v a l u e s when extreme groups a r e employed, as i n t h e p r e s e n t s t u d y . I t i s p o s s i b l e , t h a t the o b s e r v e d outcome r e f l e c t s , i n some way, t h e employment o f extreme groups. 116 GENERAL DISCUSSION The f o r e g o i n g s t u d i e s have a t t e m p t e d t o map more b r o a d l y t h e v a r i e t y o f r e s p o n s e s t o p a i n t h a t may be a l t e r e d as a f u n c t i o n o f s o c i a l m o d e l i n g i n -f l u e n c e s , and t o e x t e n d the g e n e r a l i t y o f a c c o u n t s o f p a i n phenomena b a s e d on knowledge and t h e o r y o f s o c i a l i n f l u e n c e p r o c e s s e s . E x p e r i m e n t 1 p r o v i d e d e v i d e n c e s u p p o r t i v e o f p r e v i o u s c l a i m s t h a t e x p o s u r e t o an i n t o l e r a n t s o c i a l model enhances s e n s o r y s e n s i t i v i t y t o p a i n f u l s t i m u l i , w h i l e a t the same ti m e s u g g e s t i n g t h a t p r e v i o u s c o n c l u s i o n s r e g a r d i n g the s e n s o r y e f f e c t s o f e x p o s u r e t o a t o l e r a n t model need t o be r e s t r i c t e d . I n E x p e r i m e n t 2, a n o v e l depend-e n t v a r i a b l e — o v e r t e x p r e s s i o n o f p a i n — was i n v e s t i g a t e d , and p r o v o c a t i v e e v i d e n c e was found s u g g e s t i n g t h a t s o c i a l i n f l u e n c e s a r e c a p a b l e o f p r o d u c i n g a l t e r a t i o n s i n b e h a v i o u r t h a t a r e c r i t i c a l s o c i a l d i s c r i m i n a t i v e s t i m u l i . E x p e r i m e n t 3 d e m o n s t r a t e d t h a t m o d e l i n g e f f e c t s a r e o b s e r v a b l e even when sub-j e c t s e x h i b i t i n g p r e d i s p o s i t i o n s t o w a r d p a r t i c u l a r k i n d s o f p a i n b e h a v i o u r , r a t h e r t h a n programmed c o n f e d e r a t e s , a r e employed as models. F u r t h e r , i t a p p e a r e d t h a t i n t h e impact o f c o n f l i c t i n g r e s p o n s e s t y l e s , i n t e r p e r s o n a l i n f l u e n c e , r a t h e r t h a n b e i n g r e c i p r o c a l , was u n i d i r e c t i o n a l , and t h a t i n t o l e r -ant b e h a v i o u r was c o n s i d e r a b l y more p o w e r f u l t h a n t o l e r a n t b e h a v i o u r . The s t u d i e s , t a k e n as a w h o l e , g i v e added impetus t o t h e c l a i m t h a t s o c i a l e v e n t s a r e c r i t i c a l l y i m p l i c a t e d i n f u n d a m e n t a l a s p e c t s o f p a i n . S i m u l t a n e o u s l y , t h e s t u d i e s h i g h l i g h t a number o f i s s u e s t h a t w a r r a n t f u r t h e r d i s c u s s i o n . E x p e r i m e n t a l p a i n r e s e a r c h has e x p e r i e n c e d an enormous growth w i t h i n t h e p a s t decade. I n t h e p r o c e s s o f t h i s e x p a n s i o n , two groups o f r e s e a r c h e r s have emerged t h a t can be d i f f e r e n t i a t e d on t h e b a s i s o f t h e t y p e s of s u b j e c t and the t y p e of dependent v a r i a b l e t h e y employ. R e s e a r c h e r s who employ nonhuman s u b j e c t s t e n d t o be i n t e r e s t e d i n t h e a n a t o m i c a l s t r u c t u r e s and p h y s i o l o g i c a l 117 p r o c e s s e s s u b s e r v i n g p a i n , and n a t u r a l l y base t h e i r c o n c l u s i o n s on the o v e r t b e h a v i o u r o f t h e o r g a n i s m . R e s e a r c h e r s who employ human s u b j e c t s examine a w i d e r range o f i n f l u e n c e s , b u t t h e y t e n d t o be i n t e r e s t e d i n exogenous i n -f l u e n c e s on p a i n . T h e i r dependent v a r i a b l e s a r e a l m o s t e x c l u s i v e l y d e r i v e d from s u b j e c t s ' r e p o r t s . B o t h groups make e q u i v a l e n t c l a i m s r e g a r d i n g t h e i r a b i l i t y t o draw i n f e r e n c e s about the p r o c e s s e s u n d e r l y i n g p a i n r e s p o n s e s and p a i n m o d u l a t i o n . The second e x p e r i m e n t i n the p r e s e n t s e r i e s was u n u s u a l among s t u d i e s o f p a i n i n humans i n t h a t i t was b a s e d upon o b s e r v a t i o n s o f s u b j e c t s ' o v e r t b e h a v i o u r . The t e c h n i q u e can r e a d i l y be a d a p t e d t o most p a i n s t u d i e s and a p p ears to o f f e r a g r e a t d e a l o f p r o m i s e f o r e v a l u a t i n g p a i n -m o d u l a t i o n p r o c e d u r e s . A n o t h e r i m p o r t a n t i s s u e r a i s e d by t h e p r e s e n t s t u d i e s i s t h a t o f the i n -c o n s i s t e n t i n t e r r e l a t i o n s h i p s e x h i b i t e d by d i f f e r e n t measures o f p a i n . The word " p a i n " subsumes a d i v e r s i t y o f e x c e e d i n g l y c o m p l i c a t e d s e n s o r y and be-h a v i o u r a l phenomena t h a t d e f y o v e r s i m p l i f i e d i n t e r p r e t a t i o n s . N a t u r e does n o t show an o verwhelming degree o f r e s p e c t f o r R o llman's (1977) c a r i c a t u r e o f the c l i n i c i a n who w i s h e s a s i m p l e d e f i n i t i v e answer t o the q u e s t i o n , "Has p a i n been r e d u c e d ? " I n the p r e s e n t s e r i e s o f i n v e s t i g a t i o n s , t h o s e t h a t em-p l o y e d t h e s u b j e c t ' s v e r b a l b e h a v i o u r as a s o u r c e of i n f o r m a t i o n about p a i n m o d u l a t i o n s u g g e s t e d t h a t e x p o s u r e t o an i n t o l e r a n t model was a p a r t i c u l a r l y p o w e r f u l s o u r c e o f i n f l u e n c e . At the same t i m e , d a t a d e r i v e d f r o m o b s e r v a t i o n s o f e x p r e s s i v e b e h a v i o u r s u g g e s t e d t h a t an impact o f g r e a t e r magnitude was a s s o c i a t e d w i t h e x p o s u r e t o a t o l e r a n t model. An i m p o r t a n t , r e l a t e d q u e s t i o n r a i s e d by the d a t a p r e s e n t e d i n t h i s r e -p o r t c o n c e r n s the n a t u r e o f t h e r e l a t i o n s h i p between t h e o b s e r v e d changes i n b e h a v i o u r and t h e s e n s o r y e v e n t s t h a t c o n t r i b u t e t o them. The common assump-t i o n t h a t v o c a l r e p o r t s p r o v i d e , under a p p r o p r i a t e c i r c u m s t a n c e s , f a i r l y d i r e c t 118 a c c e s s t o p r i v a t e e x p e r i e n c e s i s a p p a r e n t i n much p a i n r e s e a r c h . However, th e r e a s o n s why v o c a l b e h a v i o u r s h o u l d p r o v i d e any more adequate a c c e s s t o such e x p e r i e n c e s t h a n o t h e r t y p e s of b e h a v i o u r a r e n o t a p p a r e n t . There seems to be no p a r t i c u l a r r e a s o n t h a t , f o r example, e x p r e s s i v e b e h a v i o u r can n o t be assumed t o p r o v i d e e q u a l l y adequate a c c e s s t o p r i v a t e e x p e r i e n c e s . These q u e s t i o n s a r e o f s u b s t a n t i a l i m p o r t a n c e i n a t t e m p t i n g t o a c c o u n t f o r t h e o u t -comes o f E x p e r i m e n t s 1 and 2 i n the p r e s e n t s e r i e s . I n E x p e r i m e n t 1, the e v i d e n c e b a s e d on s u b j e c t s ' v o c a l r e p o r t s , i n d i c a t e d t h a t e x p o s u r e ^ t o an i n -t o l e r a n t model i n c r e a s e d s e n s o r y s e n s i t i v i t y t o p a i n f u l s t i m u l a t i o n , w h i l e e x p o s u r e t o a t o l e r a n t model had no apparent impact on s e n s i t i v i t y . I n E x p e r i m e n t 2, t h e e v i d e n c e , b a s e d on o b s e r v a t i o n of t h e e x p r e s s i v e b e h a v i o u r o f the s u b j e c t s i n E x p e r i m e n t 1 p r o v o k e d q u i t e d i f f e r e n t c o n c l u s i o n s . W h i l e f o r a number o f r e a s o n s i n f e r e n c e s about the i n f l u e n c e o f i n t o l e r a n t m o d e l i n g p r e s e n t i n t e r p r e t i v e d i f f i c u l t i e s , the i m p l i c a t i o n of E x p e r i m e n t 2 was t h a t t o l e r a n t m o d e l i n g was a s s o c i a t e d w i t h e x p r e s s i v e b e h a v i o u r i n d i c a t i v e o f r e d u c e d s e n s i t i v i t y t o the s t i m u l a t i o n . Which s o u r c e o f i n f o r m a t i o n — v o c a l r e p o r t o r e x p r e s s i v e b e h a v i o u r — p r o v i d e s the most a p p r o p r i a t e b a s i s f o r d r a w i n g i n f e r e n c e s about s e n s o r y s e n s i t i v i t y ? I t i s d i f f i c u l t t o a c c e p t t h e n o t i o n t h a t d a t a f r o m d i f f e r e n t measures t h a t a r e presumably m e d i a t e d by s i m i l a r p r o c e s s e s can under many c i r c u m s t a n c e s e x h i b i t such a l a c k o f c o r r e s p o n d e n c e . L a t e l y , some I n t e r e s t has been d i r e c -t e d toward e x a m i n i n g r e l a t i o n s h i p s among p r i v a t e e x p e r i e n c e s , e x p r e s s i v e and v o c a l b e h a v i o u r and p h y s i o l o g i c a l p r o c e s s e s ( C r a i g & P r k a c h i n , 1978") -K l e c k e t . al.. (1976) have p r o p o s e d an a c c o u n t , and m a r s h a l l e d some s u p p o r t i v e e v i -dence s u g g e s t i n g t h a t p r i v a t e e x p e r i e n c e s , o f p a i n may be m e d i a t e d by changes i n e x p r e s s i v e b e h a v i o u r . S i m i l a r l y , B a n d l e r , Madaras, and Bern (1968) have p r o v i d e d e v i d e n c e t h a t p a i n p e r c e p t i o n may l a r g e l y r e f l e c t the o p e r a t i o n o f 119 p r o c e s s e s t h a t f i r s t a f f e c t t he i n d i v i d u a l ' s o v e r t b e h a v i o u r . W h i l e t h e s p e c i f i c d e t a i l s o f t h e i r model need n o t be adhered t o , i t i s i n t e r e s t i n g t o s p e c u l a t e t h a t s o c i a l i n f l u e n c e p r o c e d u r e s e x e r t t h e i r f u n d a m e n t a l and most immediate impact on o v e r t s o c i a l b e h a v i o u r and t h a t changes i n s e n s o r y e x p e r i e n c e s may f o l l o w t h e s e p r i m a r y changes a t some d e l a y . T h i s w o u l d s u g -g e s t t h a t the t e m p o r a l c o n s t r a i n t s i n v o l v e d i n E x p e r i m e n t 1 and p r e v i o u s SDT a n a l y s e s o f m o d e l i n g e f f e c t s on p a i n , p r o v i d e d an i n s u f f i c i e n t o p p o r t u n i t y t o o b s e r v e t h e u l t i m a t e s e n s o r y e f f e c t s o f s o c i a l i n f l u e n c e s . T h i s p r o p o s a l w h i l e l a c k i n g e m p i r i c a l s u p p o r t , makes sense i n t h a t n a t u r a l s o c i a l i z a t i o n p r o c e s s e s i m p l i c a t e d i n p a i n m o d u l a t i o n o p e r a t e o v e r a l o n g term, and t h e i r e f f e c t s a r e q u i t e l i k e l y c u m u l a t i v e o v e r t i m e . O t h e r s u p p o r t f o r t h i s p r o -p o s a l d e r i v e s f r o m the a p p a r e n t s u c c e s s o f b e h a v i o u r a l l y - b a s e d programs f o r the r e m e d i a t i o n o f c h r o n i c p a i n problems w h i c h o p e r a t e o v e r e x t e n d e d p e r i o d s o f t i m e , and emphasize l o n g t e r m a l t e r a t i o n o f c o n t i n g e n c i e s o p e r a t i v e i n the n a t u r a l f a m i l i a l e n v i r o n m e n t s o f p a t i e n t s ( F o r d y c e , 1976b). T h i s p r o p o s a l i s a l s o c o n s i s t e n t w i t h some o f S k i n n e r ' s a t t e m p t s t o ex-p l a i n how e n v i r o n m e n t a l e v e n t s can come t o e x e r t an i n f l u e n c e upon p r i v a t e e x p e r i e n c e s ( S k i n n e r , 1945; 1957). The l a c k o f a s i g n i f i c a n t p a i n t h r e s h o l d decrement among s u b j e c t s exposed t o an i n t o l e r a n t model i n E x p e r i m e n t 1 might be a c c o u n t e d f o r by r e f e r e n c e t o t h e outcome o f E x p e r i m e n t 3. Both e x p e r i m e n t s i n v o l v e d assessment o f p a i n t h r e s h o l d s i n a p r e t e s t and an i n f l u e n c e s e s s i o n , and i n E x p e r i m e n t 3 i t was o b s e r v e d t h a t s u b j e c t s e x h i b i t i n g n a t u r a l l y low p a i n t h r e s h o l d s t e n d e d , upon r e a s s e s s m e n t t o show an e l e v a t i o n i n t h r e s h o l d s . W h i l e E x p e r i m e n t 1 employed u n s e l e c t e d g r o u p s , i t i s p o s s i b l e t h a t a s i g n i f i c a n t p r o p o r t i o n o f s u b j e c t s i n the i n t o l e r a n t group may have e x h i b i t e d t h e same tendency as t h a t o b s e r v e d among low t h r e s h o l d s u b j e c t s i n E x p e r i m e n t 3. T h i s outcome w o u l d , o f c o u r s e , 120 have masked any m o d u l a t i n g e f f e c t s a t t r i b u t a b l e t o t h e i n t o l e r a n t m o d e l i n g . T h i s outcome among i n t o l e r a n t group s u b j e c t s i n E x p e r i m e n t 1 may have been a by p r o d u c t o f t h e use o f a r e p e a t e d s e s s i o n s p r o c e d u r e . A f i n a l p o i n t i s i n o r d e r c o n c e r n i n g the a p p a r e n t u n i d i r e c t i o n a l i t y o f i n f l u e n c e i n E x p e r i m e n t 3. W h i l e i t was c l e a r t h a t , w i t h i n t h e c o n s t r a i n t s o f t h e e x p e r i m e n t a l p r o c e d u r e s , r e l a t i v e p a i n i n t o l e r a n c e was t h e more power-f u l s o u r c e o f i n f l u e n c e , i t i s l i k e l y t h a t an e x a c t a n a l o g o f n a t u r a l l y -o c c u r r i n g s o c i a l i n f l u e n c e p r o c e s s e s was n o t c r e a t e d . As was n o t e d e a r l i e r , c ommunications t o t h e e f f e c t t h a t p a i n i s b e i n g e x p e r i e n c e d r e p r e s e n t i m p e r a -t i v e s o c i a l s t i m u l i . T h e i r e f f e c t s on t h e b e h a v i o r o f o t h e r s q u i t e r e a s o n a b l y w o u l d be e x p e c t e d t o be r a p i d and p o w e r f u l . R e l a t i v e l y t o l e r a n t b e h a v i o u r , on t h e o t h e r hand, i s l i k e l y t o be more d e l a y e d i n i t s i m p a c t . The outcome o f t h i s e x p e r i m e n t , t h e n , may r e f l e c t t e m p o r a l c o n s t r a i n t s on t h e i n t e r p e r -s o n a l e f f e c t s o f t o l e r a n t and i n t o l e r a n t b e h a v i o u r . I t i s n o t u n r e a s o n a b l e , t h e n , t o s p e c u l a t e t h a t a more e x t e n d e d p e r i o d o f c o n c u r r e n t e x p o s u r e t o one a n o t h e r o f s u b j e c t s e x h i b i t i n g c o n f l i c t i n g r e s p o n s e s t y l e s m i ght have demon-s t r a t e d a g r e a t e r degree o f i n f l u e n c e r e s u l t i n g from e x p o s u r e t o r e l a t i v e l y p a i n t o l e r a n t b e h a v i o u r . 121 REFERENCE NOTES 1. Craig, K.D. Social modeling influences on pain experience and behaviour. Paper presented at the Symposium "Psychology and Pain Control", Annual Convention of the American Psychological Association, Washington, D.C, 1976. 2. Craig, K.D. and Ward, L.M. 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P e r s o n a l i t y and S o c i a l P s y c h o l o g y B u l l e t i n , 1978. T u r s k y , B. P h y s i c a l , p h y s i c a l and p s y c h o l o g i c a l f a c t o r s t h a t a f f e c t p a i n r e a c t i o n t o e l e c t r i c shock. P s y c h o p h y s i o l o g y , 1974, ]-l_, 95-112. T u r s k y , B., & S t e r n b a c h , R.A. F u r t h e r p h y s i o l o g i c a l c o r r e l a t e s o f e t h n i c d i f f e r e n c e s i n r e s p o n s e s t o shock. P s y c h o p h y s i o l o g y , 1967, 4_, 67-74. T u r s k y , B., Watson, P.O., & O ' C o n n e l l , D.M. A c o n c e n t r i c shock e l e c t r o d e f o r p a i n s t i m u l a t i o n . P s y c h o p h y s i o l o g y , 1965, 1_, 196-198. Waxer, P. N o n v e r b a l cues f o r d e p r e s s i o n . J o u r n a l o f Abnormal P s y c h o l o g y , 1974, 83, 319-322. Waxer, P.H. N o n v e r b a l cues f o r a n x i e t y : An e x a m i n a t i o n o f e m o t i o n a l l e a k -age. J o u r n a l o f Abnormal P s y c h o l o g y , 1977, 8j6, 306-314. W e i s e n b e r g , M. P a i n : C l i n i c a l and e x p e r i m e n t a l p e r s p e c t i v e s . S t . L o u i s : C V . Mosby, 1975. W e i s e n b e r g , M. P a i n and p a i n c o n t r o l . P s y c h o l o g i c a l B u l l e t i n , 1977, 84, 1008-1044 Z b o r o w s k i , M. P e o p l e i n p a i n . San F r a n c i s c o : J o s s e y - B a s s , 1969. 130 A p p e n d i x A: P s y c h o m e t r i c d a t a from E x p e r i m e n t 1. T h i s a p p e n d i x p r e s e n t s a n a l y s e s o f d a t a d e r i v e d from two q u e s t i o n n a i r e s a d m i n i s t e r e d t o s u b j e c t s i n E x p e r i m e n t 1: t h e S u b j e c t i v e S t r e s s S c a l e ( S S S ) , and the M c G i l l P a i n Q u e s t i o n n a i r e (MPQ). These q u e s t i o n n a i r e s a r e p r e s e n t e d i n A p p e n d i x C. The SSS was a d m i n i s t e r e d b o t h b e f o r e and a f t e r each s e s s i o n i n Study 1. S c a l e s c o r e v a l u e s f o r each a d m i n i s t r a t i o n were d e t e r m i n e d from N e u f e l d and D a v i d s o n ' s (197'2) t a b l e , and e n t e r e d i n t o a 3 (Groups) X 2 ( S e s s i o n s ) X 2 ( A d m i n i s t r a t i o n s : p r e - and p o s t ) ANOVA d e s i g n . The o n l y s i g n i f i c a n t e f f e c t t o emerge from t h i s a n a l y s i s was t h a t f o r S e s s i o n s , _F (1,32) = 15.45, p_ < .01. SSS s c a l e - s c o r e v a l u e s d e c l i n e d f r o m a mean o f 1.14 d u r i n g S e s s i o n 1 t o a mean o f 0.62 d u r i n g S e s s i o n 2. Thus, s u b j e c t s r e p o r t e d l o w e r l e v e l s o f s u b j e c t i v e l y a p p r a i s e d s t r e s s d u r i n g S e s s i o n 2 t h a n t h e y d i d d u r i n g S e s s i o n 1. The MPQ was a d m i n i s t e r e d a t t h e end o f each s e s s i o n i n E x p e r i m e n t 1. T h i s q u e s t i o n n a i r e has two components: (1) an a d j e c t i v e c h e c k l i s t p o r t i o n t h a t c o n t a i n s 20 c a t e g o r i e s o f 2 t o 6 words d e s c r i p t i v e o f v a r i o u s q u a l i t i e s o f p a i n , and (2) a P a i n I n t e n s i t y R a t i n g p o r t i o n t h a t r e q u i r e s the r e s p o n d e n t t o i n d i c a t e t h e i n t e n s i t y of h i s o r h e r p a i n on a 5 - p o i n t s c a l e r a n g i n g from m i l d t o e x c r u c i a t i n g . S u b j e c t s were i n s t r u c t e d t o use the h i g h e s t c u r r e n t they had a c c e p t e d as t h e i r r e f e r e n c e f o r r e s p o n d i n g t o each q u e s t i o n . M e l z a c k and T o r g e r s o n (1971) and M e l z a c k (1975) have r a t i o n a l l y s u b d i v i d -ed the a d j e c t i v e c h e c k l i s t p o r t i o n i n t o 3 d i m e n s i o n s : termed S e n s o r y , A f f e c -t i v e , and E v a l u a t i v e . C r o c k e t t , P r k a c h i n , and C r a i g (1977) c o n d u c t e d a f a c t o r a n a l y s i s o f t h e MPQ a d j e c t i v e s i n groups o f low back p a i n p a t i e n t s and v o l u n -t e e r s e xposed t o e x p e r i m e n t a l p a i n . They e x t r a c t e d 5 f a c t o r s from t h e i r a n a l y s i s , named: ( I ) Immediate A n x i e t y , ( I I ) P e r c e p t i o n o f Harm, ( I I I ) Somes-131 t h e t i c P r e s s u r e , (IV) Cutaneous. , S e n s i t i v i t y , and (V) Sensory I n f o r m a t i o n . A n a l y s e s were c o n d u c t e d on t h e s c a l e v a l u e o f the P a i n I n t e n s i t y R a t i n g , rank s c o r e s f o r M e l z a c k ' s r a t i o n a l l y - d e f i n e d d i m e n s i o n s , and f a c t o r s c o r e s f o r C r o c k e t t e t . a l . ' s e m p i r i c a l l y - d e r i v e d f a c t o r s . A l l a n a l y s e s used a 3 (Groups) X 2 ( S e s s i o n ) ANOVA. d e s i g n . No s i g n i f i c a n t d i f f e r e n c e s emerged on P a i n I n t e n s i t y r a t i n g s . A n a l y s e s o f the r a t i o n a l l y - d e r i v e d f a c t o r s r e v e a l e d no s i g n i f i c a n t a f f e c t s on the Sen-s o r y and A f f e c t i v e d i m e n s i o n s . On the E v a l u a t i v e d i m e n s i o n , a s i g n i f i c a n t S e s s i o n s e f f e c t emerged, F_ (1,32) = 10.63, p < .01. The mean rank s c o r e on t h i s measure i n c r e a s e d f r o m 1.06 i n S e s s i o n 1 t o 1.89 i n S e s s i o n 2. A c c o r d i n g t o M e l z a c k and T o r g e r s o n (19 71, p. 51) t h i s d i m e n s i o n i s d e s c r i p t i v e " o f t h e s u b j e c t i v e o v e r a l l e x p e r i e n c e o f the t o t a l e x p e r i e n c e o f p a i n . " I t i s n o t u n r e a s o n a b l e t h a t t h i s measure s h o u l d have i n c r e a s e d i n S e s s i o n 2, s i n c e t h e s e s s i o n was v e r y l o n g and i n v o l v e d e x t e n d e d e x p e r i e n c e w i t h h i g h i n t e n s i t y s h o c k s . I n t h e a n a l y s i s o f C r o c k e t t e_t. a l ' s (19 77) f a c t o r s a s i g n i f i c a n t S e s s i o n s e f f e c t o c c u r r e d on F a c t o r I I I ( S o m e s t h e t i c P r e s s u r e ) , F_ (1,32) = 7.29, p_ < .01. F a c t o r s c o r e s i n c r e a s e d f r o m a mean o f 1.36 i n S e s s i o n 1 t o 1.97 i n S e s s i o n 2. Appendix B: Consent forms. 133 CONSENT FORM: EXPERIMENT 1 Experimental P a r t i c i p a t i o n Consent Form Name of the Subject: I hereby consent to participate i n the study as described by to me at thi s time. I understand that the r i s k s to me as a subject are minimal. I further acknowledge that I have been advised that I can withdraw from pa r t i c i p a t i o n i n the project at any time. Signature: Date: Experimental P a r t i c i p a t i o n Consent Form, Name of the Subject: I hereby consent to participate i n the study as described by to me at thi s time. I understand that the r i s k s to me as a subject are minimal. I further acknowledge that I have been advised that I can withdraw from pa r t i c i p a t i o n i n the project at any time. Signature: Date: 134 VIDEOTAPE PLAYBACK CONSENT FORM I , , do hereby g i v e my c o n s e n t t o f o r t h e showing o f v i d e o t a p e s t a k e n o f m y s e l f d u r i n g my p a r t i c i p a t i o n i n t h e e x p e r i m e n t e n t i t l e d , " S o c i a l m o d e l i n g i n f l u e n c e s on e x p r e s s i v e and p s y c h o p h y s i c a l components o f p a i n r e s p o n s e , " t o : 1. o t h e r p e o p l e p a r t i c i p a t i n g as s u b j e c t s i n t h e a f o r e m e n t i o n e d e x p e r i m e n t , 2. p e o p l e i n v o l v e d i n the a n a l y s i s o f d a t a c o l l e c t e d d u r i n g t h e e x p e r i m e n t , 3. p r o f e s s i o n a l a u d i e n c e s i n t h e c o n t e x t o f r e s e a r c h c o l l o q u i a o r s i m i l a r s c i e n t i f i c p u r p o s e s . I u n d e r s t a n d t h a t t h e above t h r e e i t e m s a r e a l l t h a t I have g i v e n c o n s e n t t o , and t h a t , o u t s i d e o f t h e s e c o n s t r a i n t s , t h e r e c o r d s t a k e n o f me w i l l be k e p t s t r i c t l y c o n f i d e n t i a l . S i g n a t u r e o f p a r t i c i p a n t S i g n a t u r e o f e x p e r i m e n t e r Date 135 CONSENT FORM: EXPERIMENT 3 EXPERIMENTAL PARTICIPATION CONSENT FORM Name o f t h e s u b j e c t : I hereby c o n s e n t t o p a r t i c i p a t e i n t h e s t u d y as d e s c r i b e d by , t o me a t t h i s t i m e . I u n d e r s t a n d t h a t t h e r i s k s t o me as a s u b j e c t a r e m i n i m a l . I f u r t h e r acknowledge t h a t I have been a d v i s e d t h a t I can w i t h d r a w from p a r t i c i p a t i o n i n t h e p r o j e c t a t any t i m e . I a l s o acknowledge t h a t I have seen my p h y s i c i a n w i t h i n t h e p a s t y e a r . S i g n a t u r e : Date: 136 Appendix C: Questionnaires administered in Experiment 1. 1. Subjective Stress Scale 2. McGill Pain Questionnaire 137 SUBJECTIVE STRESS SCALE P i c k o n l y one word o f t h e f o l l o w i n g l i s t w h i c h b e s t d e s c r i b e s how y o u f e e l a t t h i s moment. W o n d e r f u l Steady C o m f o r t a b l e F i n e I n d i f f e r e n t D i d n ' t B o t h e r Me T i m i d Unsteady U n s a f e Nervous W o r r i e d F r i g h t e n e d P a n i c k y S c a r e d S t i f f ,1-38 MCGILL PAIN QUESTIONNAIRE Please answer the following two questions: 1. What did your pain feel like when you received the most intense shock? Some of the words below describe the pain you experienced. Circle ONLY those words that best describe i t . Leave out any category that i s not suitable. Use only a single word in each appropriate category — the one that applied best. Flickering Quivering Pulsing Throbbing Beating Pounding Jumping Flashing Shooting Pricking Boring D r i l l i n g Stabbing Lancinating Sharp Cutting Lacerating Pinching Pressing Gnawing Cramping Crushing Tugging Pulling Wrenching 11 Tiring Exhausting 16 Annoying Troublesome Miserable Intense Unbearable Hot Burning Scalding Searing 12 Sickening Suffocating 17 Spreading Radiating Penetrating Piercing 8 Tingling Itchy Smarting Stinging 13 Fearful Frightful Terrifying 18 Tight Numb Drawing Squeezing Tearing 9 Dull Sore Hurting Aching Heavy 14 Punishing Gruelling Cruel Vicious K i l l i n g 19 Cool Cold Freezing 10 Tender Taut Rasping Splitting 15 Wretched Blinding 20 Nagging Nauseating Agonizing Dreadful Torturing 2. How strong was the most intense pain? The following 5 words represent pain of increasing intensity. 1 2 3 4 5 Mild Discomforting Distressing Horrible Excruciating Write the number of the most appropriate word in the space beside the question. Which word describes the shock at i t s worst? 

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