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Placebo effects on verbal and nonverbal expression of pain Swalm, Delphin M. 1987

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PLACEBO EFFECTS ON VERBAL AND NONVERBAL EXPRESSION OF PAIN by DELPHIN M. S W A L M B.A. (Hons), The U n i v e r s i t y o f A l b e r t a , 1980 A THESIS SUBMITTED IN P A R T I A L FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in THE FACULTY OF GRADUATE STUDIES P s y c h o l o g y We accept th i s t hes i s as c o n f o r m i n g to the requ i red s tandard THE UNIVERSITY OF BRITISH COLUMBIA O c t o b e r 1987 ® Delphin M. S w a l m , 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my writ ten permission. Department of Psychology The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date October 9, 1987 DE-6(3/81) ABSTRACT This i nves t i ga t i on examined the impact o f a po ten t source o f soc ia l in f luence—the p lacebo—on verbal and nonverba l pain e x p r e s s i o n . Placebos exert a p o w e r f u l in f luence on pain in bo th c l in ica l and l abo ra to ry s e t t i n g s ; never the less , the p lacebo remains a p o o r l y unders tood p h e n o m e n o n . In the present s tudy the p lacebo w a s e m p l o y e d as a soc ia l in f luence des igned t o al ter sub jec ts ' expec ta t ions or be l i e f s concern ing thei r response t o a nox ious event . Fur thermore, an a t tempt was made to c lass i ca l l y c o n d i t i o n a p lacebo response in accordance w i t h the c o n d i t i o n i n g t h e o r y o f p lacebo. The pain s t imu lus cons i s ted o f 5 0 0 - m i l l i s e c o n d e lec t r i ca l shocks . The p lacebo w a s an inert w h i t e c ream descr ibed as an e f f e c t i v e and q u i c k - a c t i n g local anaesthet ic . To gain a broad assessment o f verbal and nonverba l pain express ion , t w o s e l f - r e p o r t measures and an o b j e c t i v e behavioura l measure—fac ia l e x p r e s s i o n — w e r e used. S e l f - r e p o r t c o m p r i s e d the " S e n s o r y " and "Unp leasantness" ra t io scales (der ived f r o m Grace ly , McGra th , & Dubner, 1978). Facial express iveness was coded using the Facial A c t i o n Coding S y s t e m (FACS) deve loped by Ekman and Friesen (1978). Psycho log ica l in te rven t ions have been said to p r i m a r i l y al ter pa t i en ts ' a f f e c t i v e response to pa in , thus it was expected that the greatest impact o f the p lacebo w o u l d be re f l ec ted by the Unpleasantness Scale. The Sensory ra t ings and fac ia l a c t i v i t y w e r e expected to re f l ec t less o f a change. Sex d i f f e rences were analyzed but were not expec ted because the pain s t imu lus in tens i ty w a s ind iv idua l ized . A n x i e t y ra t ings taken be fo re the t r ia ls w i t h p lacebo were expected to be l ower than anx ie ty ra t ings be fo re the n o - p l a c e b o t r i a l s ; th is w a s expected to be p o s i t i v e l y re la ted t o a ii p lacebo response (def ined as lower pain express ion dur ing p lacebo t r ia ls than dur ing n o - p l a c e b o t r ia ls ) . In the basel ine phase, sub jec ts were tes ted w i t h and w i t h o u t the p lacebo. They rece ived the expec ta t ion man ipu la t i on that the analgesic c ream w o u l d act as a local anaesthet ic . Next, t o c o n d i t i o n a p lacebo response , in the p o s i t i v e c o n d i t i o n i n g group shocks admin i s te red w i t h p lacebo cream were su r rep t i t i ous l y dec reased ; in the negat ive c o n d i t i o n i n g group shocks were inc reased; and in the basel ine ( con t ro l ) group shocks remained at basel ine leve ls . A f ina l r e t u r n - t o - b a s e l i n e phase tes ted the c o n d i t i o n e d p lacebo response. A s ign i f i can t p lacebo response w a s f o u n d to be m o s t c lear ly represented by the s e l f - r e p o r t measures and less by the fac ia l a c t i v i t y . Con t ro l g roup sub jec ts , w h o were exposed on l y to the verbal d i rec t i ve that they were rece iv ing an analgesic c ream, d e m o n s t r a t e d a clear p lacebo response on bo th the Unpleasantness and Sensory s e l f - r e p o r t sca les . Thus bo th s e l f - r e p o r t measures r e f l e c t e d a subs tan t ia l p lacebo e f f e c t . Nonverba l express ion re f l ec ted an e f f e c t on l y w i t h hal f o f the con t ro l g roup— the m a l e s — w h o exh ib i ted s i g n i f i c a n t l y less fac ia l a c t i v i t y dur ing the p lacebo t r ia ls c o m p a r e d to the n o - p l a c e b o t r i a l s . H o w e v e r , nei ther o f the t w o groups exposed to man ipu la ted shock leve ls d e m o n s t r a t e d a s ign i f i can t c o n d i t i o n e d p lacebo e f f e c t on any dependent measure. There w a s a m o d e s t re la t ionsh ip b e t w e e n fac ia l a c t i v i t y and s e l f - r e p o r t . S e l f - r e p o r t e d anx ie ty w a s s o m e w h a t p red ic t i ve o f the degree to wh ich sub jec ts ra ted p lacebo t r ia ls as less pa in fu l than n o - p l a c e b o t r i a l s , but the d i rec t i on o f th is re la t ionsh ip was o p p o s i t e t o that h y p o t h e s i z e d . In b r ie f , sub jec ts led t o expect an analgesic c r e a m , but not exposed t o the c o n d i t i o n i n g m a n i p u l a t i o n , re l iab ly exh ib i ted a p lacebo response on bo th s e l f - r e p o r t sca les ; the males in th is group a lso exh ib i ted a p lacebo response as measured by fac ia l a c t i v i t y . No suppor t w a s f o u n d f o r the c o n d i t i o n i n g theory o f p lacebo e f f e c t s . iv TABLE OF CONTENTS A b s t r a c t ii Tab le o f Con ten ts v L is t o f Tables v i i L ist o f Figures v i i i A c k n o w l e d g e m e n t ix I n t roduc t i on 1 Rev iew o f the L i terature 3 The M u l t i p l e C o m p o n e n t s o f Pain 3 Placebo and Pain 7 B i o l o g i c a l Exp lanat ion 10 E x p e c t a n c y - A t t r i b u t i o n Theory 11 V icar ious Processes 13 S e n s o r y Dec is ion Theory 14 Persona l i t y Tra i ts as Explanat ions o f Placebo E f f e c t s 15 A n x i e t y , Pain, and Placebo Response 17 Learn ing Theory 17 A n i m a l Stud ies 18 Human Stud ies 19 The V o u d o u r i s , Peck, and Co leman S tudy 23 S ta tement o f the P r o b l e m ; Measurement Issures and Hypo theses 28 Measurement 28 Verbal Report 28 Nonverba l Measures 30 P lacebo 's Var iable E f f e c t s on Pain C o m p o n e n t s 34 Hypo thes ized E f fec ts o f Placebo in the Present S tudy 35 M e t h o d 38 O v e r v i e w o f Design 38 Sub jec ts 41 Appara tus and Mater ia ls 41 Procedure 42 A s c e n d i n g Series 43 Basel ine 45 C o n d i t i o n i n g 46 Return t o Basel ine 47 Facial A c t i o n Coding 47 Results 49 Der i va t ion o f Facial A c t i v i t y Score 49 In t roduc t i on t o A n a l y s e s 53 Unpleasantness Scale Results 54 v Sensory Scale Results 59 Facial A c t i v i t y Results 65 Facial A c t i v i t y and S e l f - R e p o r t 70 A n x i e t y and Placebo 72 Placebo Reactors 72 A n x i e t y and Placebo React ion 72 D iscuss ion 75 Facial A c t i v i t y and Pain 75 S e l f - R e p o r t and Pain 77 Placebo and Pain 78 A n x i e t y 81 S u m m a r y and Conc lus ions 81 References 84 A p p e n d i c e s 93 A . Grace ly Rating Scales 94 B. FACS A c t i o n Uni ts 95 C. Exper imenta l Par t i c ipa t ion 96 D. Med ica l Screening Form 97 E. Drug Checkl is t 98 F. P o s t - E x p e r i m e n t a l Quest ionna i re 99 G. Debr ie f i ng 100 H. A N O V A S u m m a r y Tables 101 I. Tables of Cell Means and Standard Dev ia t i ons 108 vi List of Tables 1. S t imu lus In tens i t y f o r Voudour i s et a l . S tudy 25 2. Des ign O v e r v i e w .40 3. A U s A f t e r Exc lus ion Cr i te r ia 51 4 . W e i g h t s Used t o Der ive Facial A c t i v i t y Score 52 5. Mu l t i p le Regress ion Resul ts f o r Facial A c t i v i t y & S e l f - R e p o r t 71 6. Mu l t i p l e Regress ion Results f o r A n x i e t y and Placebo React ion 74 7. Unp leasantness Scale A N O V A S u m m a r y Table 102 8. Sensory Scale A N O V A S u m m a r y Table 104 9. Facial A c t i v i t y A N O V A S u m m a r y Table 106 10. Unp leasantess Scale Cell Means f o r In tens i t y & Placebo 109 11 . Unp leasantess Scale Cell M e a n s : Group x Placebo 110 12. Unp leasantess Scale Cell M e a n s : Group x Placebo x In tens i t y 111 13. Sensory Scale Cell Means f o r In tens i t y 112 14. Sensory Scale Cell M e a n s : Group x Placebo 113 15. Sensory Scale Cell M e a n s ; Group x Placebo x In tens i t y 114 16. Sensory Scale Cell M e a n s : Group x Sex x Pre /Pos t x In tens i ty 115 17. Facial A c t i v i t y Cell Means f o r In tens i t y 116 18. Facial A c t i v i t y Cell M e a n s : Sex x Placebo 117 19. Facial A c t i v i t y Cell M e a n s : Group x Sex x Placebo 118 20. Facial A c t i v i t y Cell M e a n s : Pre /Pos t x Placebo x In tens i t y 119 v i i List of Figures 1. I n tens i t y Factor on the Three Dependent Measures 55 2. Unp leasantness Scale ; Group x Placebo 56 3. Unp leasantness Scale ; Group x P lacebo x In tens i t y 58 4. S e n s o r y Sca le : Group x Placebo 60 5. S e n s o r y Sca le ; Group x Placebo x In tens i t y 61 6. Sensory Sca le : Group x Sex x Pre /Pos t 64 7. Facial A c t i v i t y : Sex x Placebo 67 8. Facial A c t i v i t y : Group x Sex x Placebo 68 9. Facial A c t i v i t y : Pre /Post x P lacebo x In tens i ty 69 v i i i ACKNOWLEDGEMENT Pride in th is accomp l i shmen t w o u l d not have been p o s s i b l e w i t h o u t the cha l leng ing and s t imu la t i ng guidance p r o v i d e d by m y supe rv i so r , Dr. Kenneth D. Craig. M y apprec ia t ion a lso extends t o m y c o m m i t t e e m e m b e r s , Drs. S. Butt and W . L inden, w h o p r o v i d e d he lp fu l i ns t ruc t i on and adv ice . The f r e e d o m to fee l pr ide w a s ins t i l l ed by many years o f uncond i t iona l suppor t p r o v i d e d by m y lov ing pa ren ts ; they deserve a b ig t h a n k - y o u f o r teaching me t o en joy succeed ing in scho las t i c endeavors . F ina l ly , m y husband, Paul, deserves a specia l thanks f o r p r o v i d i n g a so l i d and secure sanctuary at h o m e . ix 1 In t roduc t i on Pain m a y best be v i e w e d as a m u l t i f a c e t e d exper ience modu la ted by the senso ry input , pr ior exper ience, a t t e n t i o n paid t o the pa in , personal c o n t r o l over the pa in , and personal consequences of the pa in . The main c o m p o n e n t s o f pain include the s e n s o r y , c o g n i t i v e , a f f e c t i v e f a c e t s , and c o m b i n a t i o n s o f these (Craig, in p ress ; Me lzack , 1984). One s t ra tegy f o r s t u d y i n g pain invo lves the i m p l e m e n t a t i o n o f soc ia l in f luence t o examine the changes upon var ious pain c o m p o n e n t s . A n exemp la ry socia l man ipu la t i on is the p lacebo d i rec t i ve that s o m e procedure w i l l reduce pa in fu lness (Craig, in p ress ; Melzack & W a l l , 1982). S p e c i f i c a t i o n o f wh ich c o m p o n e n t s o f pa in fu lness that are a f f e c t e d by soc ia l in f luence has i m p o r t a n t assessment and t rea tmen t i m p l i c a t i o n s . For ins tance, i f one c o m p o n e n t o f pain can be reduced th rough socia l i n f l uence , then part o f the t o t a l pain exper ience cou ld be r e m e d i e d . Just h o w p lacebos exert their e f f e c t s is s t i l l in ques t ion (Jospe, 1978), but a va r ie ty o f p rocesses have been p r o p o s e d . A t t e m p t s have been made to inves t iga te the f o l l o w i n g as de te rminan ts o f the p lacebo r e s p o n s e : the role o f endorph ins (Brody , 1980; Lev ine , G o r d o n , & Fie lds, 1978; Mayer & W a t k i n s , 1981 ; Melzack & W a l l , 1982), expec tancy and a t t r i bu t i ons (Gracely et al . , 1982; Pr ice, 1984; Price & Barber, 1987; Ross & O l s o n , 1981), soc ia l m o d e l i n g (Craig, 1978, 1983; Craig & Pat r ick , 1985; Craig & Prkachin, 1978, 1980), w i l l i n g n e s s t o report pain (Clark, 1969; Craig <& Coren , 1975; Feather, Chapman, & Fisher, 1972), pe rsona l i t y charac te r i s t i cs , inc lud ing anx ie ty (Jospe, 1978; Parker et al. , 1983; Parkhouse, 1963; Sh ipman et al . , 1974; S ternbach, 1974), and learning theo ry f a c t o r s , inc lud ing 2 s i tua t iona l var iab les and learning h i s t o r y (Gl iedman et al. , 1957; Gracely et al. , 1982; Gry l l & Katahn, 1978; Her rns te in , 1962; Parkhouse, 1963; Voudour is et al., 1985; W i c k r a m a s e k e r a , 1980). C lass ica l c o n d i t i o n i n g t h e o r y a f f o r d s a tenable mechan ism that may be i nvoked t o explain p lacebo e f f e c t s in bo th an imals and humans (Wick ramasekera , 1980). V o u d o u r i s , Peck, and Co leman (1985) a t t e m p t e d to c lass ica l l y c o n d i t i o n a p lacebo response in humans in a c o n t r o l l e d l abo ra to ry s e t t i n g . In b r ie f , the i r s t u d y d e m o n s t r a t e d a s o l i d c o n d i t i o n i n g e f f e c t in w h i c h subjects repea ted ly g iven more intense pain s t i m u l i a long w i t h a p lacebo came t o repor t m o r e pain whenever the p lacebo w a s a p p l i e d ; s i m i l a r l y , sub jec ts g i ven less intense pain s t imu l i w i t h p lacebo came t o repor t s o m e w h a t less pain wheneve r the p lacebo w a s app l ied . The present s tudy a t t e m p t e d to rep l i ca te and extend their f i n d i n g s us ing a d i f f e r e n t pa in s t imu lus , broader dependent measures , and an abbrev ia ted procedure . Be fo re descr ib ing th is in d e t a i l , a r e v i e w of the l i te ra ture w i l l h igh l ight the current concep tua l i za t ion o f pa in , p lacebos , and measurement issues. 3 Rev iew o f the Li terature The Mu l t i p le C o m p o n e n t s o f Pain Pain pe rcep t ion is not d i rec t l y p ropor t i ona l to the nature o f the pain s t imu lus and is m o r e c o m p l e x than pure sensory p e r c e p t i o n . There is no "pain c e n t r e " and "v i r tua l l y all o f the brain p lays a ro le in p a i n " (Melzack & W a l l , 1982, p. 162). Pain var ies cons iderab ly b e t w e e n ind iv idua ls and across cu l tures depend ing on such f a c t o r s as pr io r exper ience, a t t e n t i o n paid t o the pa in , fee l ings ' o f con t ro l over the pa in , and personal consequences as a resul t o f the pain (Craig, 1984; Melzack and W a l l , 1982). One source o f d i f f i c u l t y in de te rmin ing the impac t o f these var ious soc ia l and p s y c h o l o g i c a l events on pain has been that researchers , c l in i c ians , and persons exper ienc ing pain f i n d it d i f f i c u l t t o de f ine and quan t i f y . The In ternat iona l A s s o c i a t i o n f o r the S tudy o f Pain (1986) has de f i ned pain as " [a]n unpleasant sensory and e m o t i o n a l exper ience assoc ia ted w i t h actual or po ten t ia l t issue damage, or descr ibed in t e r m s o f such d a m a g e " (p. S217). This d e f i n i t i o n h igh l ights bo th the p s y c h o l o g i c a l and p h y s i o l o g i c a l ( t rauma, neural input , etc.) fea tures o f pain and concurs w i t h the Melzack and Wal l (1982) G a t e - C o n t r o l Theory o f pa in . G iven th is c o m p l e x i t y , it may be reasonable to pa r t i t i on express ive fea tures o f pain in to d i f f e r e n t c o m p o n e n t s and examine their imp l i ca t i ons f o r unders tand ing sub jec t i ve qua l i t ies . The h igh ly sub jec t i ve exper ience o f pain is i nd i rec t l y eva luated by measures wh ich purpor t t o q u a n t i f y p a i n - r e l a t e d t h o u g h t s , f e e l i n g s , behav iours , and /o r sensa t ions . Recent ly deve loped measures have a t t e m p t e d to quan t i f y mu l t ip le c o m p o n e n t s o f pa in , much l ike the ear ly behav iou r i s t s w h o measured mu l t ip le c o m p o n e n t s o f anx ie ty or fear in three 4 response s y s t e m s ; behav ioura l , p h y s i o l o g i c a l / a f f e c t i v e , and c o g n i t i v e / s e l f - r e p o r t (Lang, 1968). D i f f e r e n t measures y i e l d d i f f e r e n t in te rp re ta t ions as to h o w peop le th ink and f e e l , thus it is impor tan t to se lect measures wh ich b road ly assess the va r i ous e l e m e n t s o f the pain exper ience. Whi le many over lapp ing c o m p o n e n t s o f pain express ion have been p r o p o s e d , a general consensus regard ing the key c o m p o n e n t s is poss ib le i f broad enough ca tegor ies are re ta ined. Be fo re conc lud ing w h i c h broad ca tegor ies to re ta in , an examina t ion of p r o p o s e d pain subca tegor ies w i l l h ighl ight issues invo lved in d e f i n i n g the pain cons t ruc t . Drawing upon the theore t i ca l d e s c r i p t i o n o f pain d e v e l o p e d by Melzack and Casey (1968), Melzack 's (1975) f o r m u l a t i o n o f pain c o m p o n e n t s has been the mos t w i d e l y used g iven that he o f f e r e d an emp i r i ca l v a l i d a t i o n o f his t e r m s and a pain scale to measure the c o m p o n e n t s , the McGi l l Pain Quest ionna i re (MPQ). In de r i v ing the sca le , Melzack and To rge rson (1971) gathered 102 pain ad jec t i ves f r o m pat ien ts and a r t i c les . Subjec ts were asked t o c l a s s i f y these w o r d s in to subca tegor ies . What resu l ted were 3 major c lasses and 16 subc lasses o f w o r d s represen t ing pain c o m p o n e n t s . F ina l ly , w o r d s in each subc lass were ass igned in tens i t y values by d o c t o r s , pa t ien ts , and s tudents . The three ma jo r c lasses w e r e (1) w o r d s that descr ibe the sensory qualities o f the exper ience in t e r m s o f t e m p o r a l , spa t ia l , p ressure, t h e r m a l , and other p r o p e r t i e s ; (2) w o r d s that descr ibe affective qualities, in t e r m s o f t e n s i o n , fear , and au tonomic p roper t ies that are part o f the pain exper ience; and (3) evaluative w o r d s that descr ibe the sub jec t i ve overa l l in tens i ty o f the to ta l pain exper ience (Melzack, 1975, p. 278). Turk, Rudy, and Sa lovey (1985) suppor ted these three d i m e n s i o n s in f a c t o r ana ly t i c s tud ies , but there w a s cons iderab le over lap be tween the d i m e n s i o n s . 5 They conc luded that the ca tegor ies were not d is t inc t and that a to ta l score should be e m p l o y e d rather than subscores based on ove r lapp ing d i m e n s i o n s . Melzack (1985) counterargued that desp i te their modera te covar iance , the three d i m e n s i o n s are d i s t i n c t , as they have been s h o w n t o be d i f f e r e n t i a l l y respons ive t o t r e a t m e n t s and they d i f f e r ac ross separate k inds of pa in . Pr ie to and Geis inger (1983) r e v i e w e d f a c t o r - a n a l y t i c s tud ies o f the MPQ and sugges ted that an average o f f ou r f a c t o r s w e r e ex t rac ted . They po in ted out that no c o n f i r m a t o r y f a c t o r - a n a l y t i c s tud ies have been c o n d u c t e d ; thus , it may be premature to d i s m i s s the three subscores o f the MPQ. Crocke t t et al . (1986) uncovered f i v e f a c t o r s w h i c h accounted f o r 47% of the t o t a l var iance in l a b o r a t o r y pain sub jec ts . The f i r s t t w o f a c t o r s c o r r e s p o n d e d to an a f f e c t i v e and a sensory c o m p o n e n t , r e s p e c t i v e l y . Reading (1983) a lso f o u n d suppor t f o r the cons t ruc t v a l i d i t y o f the sensory and a f f e c t i v e subscores , but the eva lua t ive subscore w a s p r o b l e m a t i c in f a c t o r ana lyses and c luster ana lyses . Thus the MPQ might be v i e w e d as measur ing at least a f f e c t i v e and senso ry qua l i t ies o f pa in . Others have p r o p o s e d that pa in c o u l d be p a r t i t i o n e d in to va r ious b road ly d e f i n e d fea tu res . W o r k i n g f r o m the empi r i ca l c o n t r i b u t i o n s o f o the rs , Craig has examined var ious p s y c h o l o g i c a l c o m p o n e n t s o f pa in ; name ly s e n s o r y , a f f e c t i v e , c o g n i t i v e , and behav ioura l (Craig, I984a; Craig & Prkachin, 1980). Rol lman (1977) re fe rs t o a l te ra t ions in the pain response due to "sensory at tenuat ion. . .changes in anx ie ty , a t t i t ude , e m o t i o n , m o t i v a t i o n , and r e a c t i v i t y " (p. 208). F ina l l y , Grace ly (1979) argues that c l in ica l pain shou ld be assessed in t e r m s o f jus t senso ry and e m o t i o n a l qua l i t i es , c i t i ng f a c t o r ana ly t i c s tud ies o f the MPQ wh ich ex t rac ted 5 to 7 6 f a c t o r s that cou ld fur ther be ca tegor ized as (1) senso ry , (2) e m o t i o n a l , or (3) bo th senso ry and e m o t i o n a l . A t th is s tage in de f i n ing the c o m p o n e n t s o f pa in , the conse rva t i ve approach o f using rather g lobal ca tego r ies , as Gracely has done, seems m o s t d e f e n s i b l e . Categor ies such as " c o g n i t i v e " , " a f f e c t i v e " , " reac t i ve " or " e v a l u a t i v e " are men t ioned in the l i te ra ture o f t e n w i t h o u t clear d e f i n i t i o n s . Perhaps var ious c o m p o n e n t s should be g rouped toge ther unt i l they can be o p e r a t i o n a l l y de f i ned and quan t i f i ed . Even Melzack (1984) has a d m i t t e d that ana lyses o f "the language of p a i n " , w h i c h have rece ived "unan imous ag reemen t " , de l ineate pain in to the t w o c o m p o n e n t s o f "sensory and a f f e c t i v e " (p. 338). The re fo re , sensory and a f f e c t i v e qua l i t ies o f pain w e r e cons ide red t o be o f paramount impor tance in the assessment o f pain in the present i n v e s t i g a t i o n . Whi le sensory and a f f e c t i v e pain c o m p o n e n t s are c o m m o n l y assessed w i t h s e l f - r e p o r t , ob jec t i ve behavioura l measures can broaden the scope o f measuremen t . D i f f e r e n t measures are l i ke l y t o lead to d i f f e r e n t in fe rences about the nature o f the exper ience. Further, the use o f a l te rna t ive measurement modes ensures that pain can be quan t i f i ed in persons w h o are unable or u n w i l l i n g to g ive re l iable and accurate verbal repor ts o f pa in . Inc lus ion o f the behavioura l c o m p o n e n t is i n tu i t i ve l y appeal ing s ince such a large fea tu re o f the pain exper ience c lea r l y i nvo l ves such observab le m o t o r behav iours as immed ia te w i t h d r a w a l f r o m a pain s t i m u l u s , rubbing the a f f e c t e d b o d y par t , v o c a l i z i n g , and fac ia l g r imaces (Craig, in p ress) . Verbal and nonverba l behav iours p rov ide the means by wh ich sub jec t i ve qual i t ies are i n fe r red . Behav iour is ts such as Fordyce (1976a, 1976b; Fordyce , Fowle r , 7 & DeLateur, 1975) have measured chron ic pain s o l e l y in t e r m s of "pain behav iou rs " w i t h the assumpt ion that such express ive behav iours re f lec t the sub jec t i ve pain exper ience w i t h less d i s t o r t i o n than verbal repor t (Melzack & W a l l , 1982; S te rnbach, 1984; Turk, Me ichenbaum, & Genest , 1983; Un ike l , 1978). A t the ve ry least , express ive behav iours a f f o r d an add i t iona l mode o f measur ing pain that may i m p r o v e the measurement accuracy . This m u l t i d i m e n s i o n a l approach t o the d e f i n i t i o n and assessment o f pain has severa l i m p l i c a t i o n s . F i rs t , a t t e m p t s at exp la in ing the origins o f pain can address bo th p s y c h o l o g i c a l (e.g., expec ta t ions and b e l i e f s ) and p h y s i o l o g i c a l (e.g., t issue damage) p rocesses wh ich can be examined bo th separa te ly and as c o m p l e m e n t a r y p rocesses . For examp le , Melzack and Wal l (1982) have incorpora ted a c o g n i t i v e con t ro l c o m p o n e n t as a p s y c h o l o g i c a l face t that in teracts w i t h the p h y s i o l o g i c a l pain p rocess . S e c o n d l y , a t t e m p t s to quantify or measure pain s i m i l a r l y m a y invo lve a range o f i ns t rumen ts des igned t o assess the mu l t i p le f a c e t s o f the pa in exper ience. D i f f e r e n t t y p e s o f pain are re f l ec ted d i f f e r e n t i a l l y across the pain c o m p o n e n t s (Melzack, 1985). F ina l ly , treatment packages also emphas ize d i f f e ren t p s y c h o l o g i c a l qua l i t ies in add i t i on t o the a t t e m p t s to decrease or mask the p h y s i o l o g i c a l input o f the pain w i t h analges ics or e lec t r ica l s t i m u l a t i o n o f ne rves , fo r example (Melzack & W a l l , 1982). Placebo and Pain One research s t ra tegy f o r examin ing d i f f e r e n t express ive and exper ient ia l qua l i t ies o f pain i nvo l ves examin ing the impac t o f po tent f o r m s o f soc ia l i n f luence . Examin ing the p lacebo e f f e c t a l l o w s a f o r m a l i nves t i ga t i on o f the impact o f var ious p s y c h o l o g i c a l p rocesses (e.g., 8 c o n d i t i o n i n g , soc ia l i n f l uence , b e l i e f s , e x p e c t a t i o n s ) on the pain exper ience ; in th is w a y , the p lacebo e f f e c t a f f o r d s a psycho log i ca l pe rspec t i ve in unders tand ing the pain c o m p o n e n t s . H o p e f u l l y , fu ture research w i l l uncover the p rocess under ly ing the p lacebo e f f e c t w h i c h cou ld be e x p l o i t e d in p s y c h o l o g i c a l t rea tmen t o f pain as e x e m p l i f i e d by Engs t rom (1983) w h o s u c c e s s f u l l y t ra ined p lacebo responders to use internal ( c o g n i t i v e - b e h a v i o u r a l ) means o f pain c o n t r o l a f te r they were i n f o r m e d that they had responded to p lacebo m e d i c a t i o n s . The t e r m "p lacebo" has been b o r r o w e d f r o m med ic ine where it w a s d e f i n e d as a p h a r m a c o l o g i c a l l y inert substance w h o s e a d m i n i s t r a t i o n a l l ev ia ted p h y s i o l o g i c a l or p s y c h i a t r i c i m p a i r m e n t . In p s y c h o l o g y th is t e r m has been used in a v a r i e t y o f w a y s , but was usual ly de f i ned as an i n t e r v e n t i o n that was n o n s p e c i f i c , iner t , or not ac t ive in t rea t ing s o m e d y s f u n c t i o n — a p s e u d o t r e a t m e n t (Sued fe ld , I984). The t e r m s " n o n s p e c i f i c ' V ' s p e c i f i c " and " i n a c t i v e ' V ' a c t i v e " are imprec ise . " N o n s p e c i f i c " imp l ies that h o w the p lacebo a l lev ia tes i l lness or d y s f u n c t i o n is p resen t l y u n s p e c i f i e d , and that once we de f ine i ts mechan ism o f ac t ion it w i l l b e c o m e s p e c i f i c . Further, if the p lacebo is inert or not ac t i ve , h o w can it ac t i va te an e f f e c t ? W i t h i n the p s y c h o l o g i c a l f r a m e w o r k o f the present i n v e s t i g a t i o n , the " p l a c e b o " re fe rs to a substance or i n te rven t ion wh ich e f f e c t s a change in an o r g a n i s m ' s behav iour desp i te the fac t that no accep ted t h e o r y can pred ic t or expla in the genesis o f the change. The "change" c o n s t i t u t e s the "p lacebo e f f e c t " , wh ich cou ld inc lude such o u t c o m e s as the reduc t ion o f pain due t o the a d m i n i s t r a t i o n o f a sugar p i l l , or the l i f t i ng o f dep ress ion due t o be ing " t r e a t e d " in an 9 a t t e n t i o n - c o n t r o l therapy group. (Grunbaum, 1981 ; Cr i te l l i & Neumann, 1984; W i l k i n s , 1979, 1984). Placebo research in pain t rea tmen t w a s largely s t i m u l a t e d by Beecher (1955, 1959) w h o p o i n t e d out that in 15 s tudies i n v o l v i n g over 1000 sub jec ts , 35 + 2.2% o f sub jec ts responded f a v o r a b l y t o p lacebos in a "var ie ty o f c o n d i t i o n s , inc lud ing pa in , nausea, and m o o d changes" (1955, p. 1605). He suggested that p lacebos act upon the " reac t ion f a c e t " o f pa in , as o p p o s e d t o the sensory c o m p o n e n t as if there w e r e imag ined versus real pa in . Beecher (1961) dep ic ted a n o t e w o r t h y example o f a p lacebo e f f e c t . In the ear ly and m i d - 1 9 5 0 s , angina pec to r i s was t rea ted by surgical l i ga t ion o f the internal m a m m a r y ar te r ies . It w a s later d i s c o v e r e d that pa t ien ts g iven a sham opera t i on s h o w e d comparab le i m p r o v e m e n t s . Thus, the surgical procedure w a s qu ick ly d i s c r e d i t e d . In f a c t , s o m e authors have suggested that mos t medica l p rocedures pr ior t o the present cen tu ry w e r e p lacebo procedures (Jospe, 1978; Shap i ro , 1960), and argue that even present medica l procedures may include a large p lacebo c o m p o n e n t (Jospe, 1978). In med ic ine , a p lacebo c o m p o n e n t has been t rea ted h i s to r i ca l l y as a source o f a r t i fac t or measurement er ror . The p lacebo a lso appeared as a con t ro l p rocedure w i t h w h i c h " a c t i v e " t rea tmen t w a s c o m p a r e d . It has b e c o m e apparent that th is con t ro l procedure is i t se l f ac t i ve in e f f e c t i n g changes in i l lness behav iour (Brody , 1980; Cr i te l l i & Neumann, 1980; L iebesk ind & Paul, 1977; Shap i ro , 1960). The p rocess by w h i c h p lacebos achieve their e f f e c t s remains unclear, but several exp lana to ry hypo theses 10 have been advanced. These hypo theses are couched in a w i d e range of b i o l o g i c a l and p s y c h o l o g i c a l theor ies w h i c h have inc luded the f o l l o w i n g : b i o l o g i c a l mode ls emphas iz ing endorph ins ; p s y c h o l o g i c a l t heo r ies emphasiz ing expec tancy and a t t r i b u t i o n s ; soc ia l m o d e l i n g ; a l tered w i l l i n g n e s s to repor t pain p o s s i b l y due to a va r ie ty o f p e r s o n a l i t y charac te r i s t i cs inc luding a n x i e t y ; and f i n a l l y , learning theo ry w h i c h emphas ized s t i m u l u s and response f a c t o r s , as w e l l as o rgan ismic f a c t o r s such as one's learning h i s t o r y . B io log ica l Exp lanat ion. The current in terest in endogenous op ia te s y s t e m s has been extended to the s t u d y o f p lacebo e f f e c t s . W i t h regard to the p lacebo response in pa in , endorph in increase has been f o u n d to resul t f r o m p lacebos , and may be a b i o l o g i c a l mechan ism th rough wh ich the p lacebo response at tenuates pain (Brody , 1980; Lev ine , G o r d o n , and Fields, 1978; Mayer and W a t k i n s , 1981 ; Melzack and W a l l , 1982). Mayer and W a t k i n s (1981 ; Watk ins and Mayer , 1982) have examined endorphin responses in rats exposed to nox ious s t i m u l i and conc luded "that c lass ica l l y c o n d i t i o n e d analgesia is a l w a y s subserved by an op ia te p a t h w a y " regardless o f w h i c h ascending pain s y s t e m w a s a c t i v a t e d by pain or the cond i t i oned s t i m u l u s (exposure to the exper imenta l chamber w i t h o u t pa in ) (p. 80). A c r o s s - t o l e r a n c e b e t w e e n morph ine analgesia and f ron t paw f o o t - s h o c k - i n d u c e d analgesia w a s d e m o n s t r a t e d thereby suppor t ing the n o t i o n that bo th k inds o f analgesia w e r e o p i a t e - m e d i a t e d . These researchers summar ized fu r ther s tud ies d e m o n s t r a t i n g that rats ac t i va te thei r endogenous op ia tes w h e n env i ronmenta l cues are present w h i c h s ignal impend ing f o o t - s h o c k . One such cue w a s exposure to the n o n e l e c t r i f i e d gr id (CS) p rev ious l y pa i red w i t h hind p a w and /o r f ron t paw 11 shock. (See a lso Gaiardi et al. , 1983; Terman et a l . , 1984.) H o w e v e r , c lass ica l c o n d i t i o n i n g procedures have also been sugges ted t o ac t i va te n o n - o p i a t e analgesia s y s t e m s in rats (Hayes, Bennet t , N e w l o n , and Mayer , 1978) and in humans (Gracely et al . , 1983) so no f i r m conc lus ions can be d r a w n . If w e can sa fe ly general ize f r o m rats to humans, then there may be mu l t i p l e pain inh ib i to ry s y s t e m s in humans wh ich are d i f f e r e n t i a l l y ac t i va ted by a v a r i e t y o f env i ronmenta l and personal even ts . For examp le , it has been sugges ted that acupuncture and t ranscutaneous s t i m u l a t i o n seem t o ac t i va te bo th op ia te and nonop ia te s y s t e m s , whereas hypnos is seems t o opera te m a i n l y through the nonop ia te s y s t e m ( s ) (Terman et al. , 1984; Watk ins & Mayer , 1982). Placebo analgesia seems to i nvo l ve m a i n l y op ia te m e c h a n i s m s , p o s s i b l y c lass ica l l y c o n d i t i o n e d and, t h e r e f o r e , e l i c i t ed by past exper ience. But other exp lanat ions are equal ly c o m p e l l i n g and perhaps c o m p l e m e n t a r y to the b io log ica l approach. E x p e c t a n c y - A t t r i b u t i o n t h e o r y . Ross and O lson (1981) recen t l y p r o p o s e d a c o m p l e x p s y c h o l o g i c a l mode l that may account f o r the d i v e r s i t y o f p lacebo research f i n d i n g s . That is , s o m e t i m e s expectanc ies generate a s tandard p lacebo response and s o m e t i m e s expectanc ies generate a response o p p o s i t e to the purpor ted e f f e c t o f the p lacebo . They d is t ingu ish b e t w e e n t w o leve ls o f assessment , name ly p r imary assessment and secondary assessment . The f o r m e r measures the p lacebo rec ip ien t ' s s p e c i f i c expectanc ies about the p lacebo 's e f f e c t s (p lacebo e f f e c t s ) . Placebo e f f e c t s are assessed b y means o f s e l f - r e p o r t and behav ioura l or p h y s i o l o g i c a l o b s e r v a t i o n . Secondary assessment measures "the sub ject 's in ferences 12 about under ly ing d i s p o s i t i o n s [or m a n i f e s t • s ta tes ] that are not be l ieved t o be d i rec t l y a f f e c t e d by the p lacebo ( induct ive e f f e c t s ) " (p. 408). In th is case, the p lacebo may be d i rec ted at s y m p t o m s but the assessment f ocuses on whether the subject be l ieves that their under l y ing c o n d i t i o n has been a l te red . P lacebos are usual ly d i rec ted at s y m p t o m s but may be d i rec ted at under ly ing causes. If d i rec ted at s y m p t o m s , resu l tant changes "do no t necessar i l y i m p l y changes in the under ly ing cause" (p. 413) ; e.g., a p lacebo said to b lock pain sensa t ion migh t be v i e w e d as d i rec ted at the s y m p t o m o f pa in . If p lacebos are " targeted at the under ly ing cause, changes in s y m p t o m s may be in terpre ted as an ind ica t ion o f change in the under l y ing cause" (p. 413) ; e.g., a p lacebo said to be d i rec ted at heal ing an i n f l a m e d w o u n d may be v i e w e d as d i rec ted at the under ly ing cause o f pa in . Thus, i f the p lacebo is d i rec ted at an under ly ing cause, the p lacebo rec ip ien t makes in fe rences about s o m e under ly ing s ta te as a resul t o f the p lacebo 's impact on s y m p t o m s . The nature o f these in fe rences depends on whe the r the p lacebo increased or decreased s y m p t o m s e v e r i t y , and whether th is increase or decrease w a s expected or no t . One's expec ta t ions or b e l i e f s about the under ly ing cause o f the s y m p t o m s cou ld p resumab ly in f luence subsequent t rea tment e f f e c t i v e n e s s . Such be l i e f s may depend on learn ing, hence a learning perspec t i ve is c o m p l e m e n t a r y to th is m o d e l . Ross and Olson (1981) summar ized cur ren t ly hypo thes ized mechan isms by w h i c h p lacebos exert e f f e c t s th rough a l tered expec tanc ies . A n x i e t y about one 's s y m p t o m s may be reduced and thereby br ing about i m p r o v e m e n t (as in pain s ta tes , f o r example) . Ind iv idua ls may a t tend m o r e 13 c lose l y to p o s i t i v e changes in their c o n d i t i o n , or they m a y in terpret amb iguous " s o m a t i c s e n s a t i o n s " as s igns o f i m p r o v e m e n t . Sub jec ts may s i m p l y be c o m p l y i n g w i t h the "demands o f the s i t u a t i o n " . A n d f i n a l l y , p lacebo e f f e c t s "may s o m e t i m e s be c o n d i t i o n e d responses.. . . " (Ross and O lson , 1978, p. 427). A separate research g roup inves t iga ted a l tered expec tanc ies using labo ra to ry sub jec ts exposed to nox ious heat s t i m u l a t i o n (Price et al . , 1980). Warn ing the subjects that the next s t imu lus w o u l d be in tense resu l ted in reduced pain ra t ings on a scale measur ing a f f e c t i v e pain but not on a scale measur ing sensory pa in . Price (1984) suggested that a f f e c t i v e pain responses are more easi ly changed by s i tua t iona l f a c t o r s than are sensory pain r e s p o n s e s . Further, p s y c h o l o g i c a l i n te rven t ions such as hypno t i c sugges t ion f o r analgesia have been s h o w n t o result in a greater pain reduc t ion as measured b y an a f f e c t i v e rather than a s e n s o r y v isua l analogue scale (Price & Barber, 1987). Expectancy e f f e c t s a lso resu l ted in reduced a f f e c t i v e (unp leasantness) pain as o p p o s e d to senso ry pain in exper imenta l pain s tudies c o n d u c t e d by Grace ly et a l . (1979, 1982), t o be d iscussed in a subsequent s e c t i o n . Pr ice, Hark ins, and Baker (1987) have c o m e t o conc lude that aside f r o m expec tancy e f f e c t s , c o g n i t i o n s in general (such as the meaning o f pa in ) have a d i f f e r e n t i a l in f luence on sensory and a f f e c t i v e pa in . For example , back pa in , causa lg ia , and cancer pain pat ien ts gave s i g n i f i c a n t l y higher a f f e c t i v e than senso ry pain r a t i n g s ; exper imenta l pain sub jec ts gave higher ra t ings f o r sensory than f o r a f f e c t i v e pa in . 14 V icar ious Processes. Soc ia l i za t i on p rocesses exert p o w e r f u l in f luences over the express ion and exper ience o f pa in . Through soc ia l m o d e l i n g w e learn to exhibi t behaviours w h i c h c o m m u n i c a t e our d is t ress to those around us and enable us to unders tand the mean ing and s ign i f i cance o f b o d i l y exper iences. A s imi la r m o d e l i n g p rocess has been d e m o n s t r a t e d in the l a b o r a t o r y se t t i ng . To lerant and in to lerant m o d e l s have been s h o w n to in f luence sub jec ts ' s e l f - r e p o r t e d pain as w e l l as p s y c h o p h y s i o l o g i c a l measures o f pain (Craig, 1978, 1983; Craig & Pat r ick , 1985; Craig & Prkach in , 1978, 1980). Perhaps the p lacebo e f f e c t is par t l y a s o c i a l l y - m e d i a t e d process much l ike to le ran t m o d e l i n g in that the subject repor ts pain leve ls in accordance w i t h soc ia l cues. Sensory Dec is ion Theory . In a m o d e l that is p o s s i b l y re la ted to s o c i a l i z a t i o n , p lacebo was env is ioned as not a f f e c t i n g pain s e n s i t i v i t y but ins tead, s u b j e c t s ' w i l l i ngness to repor t pain to a soc ia l o ther . SDT has been used in psychophys ica l research to separate the response bias (or a f f e c t i v e c o m p o n e n t ) f r o m sensory pe rcep t i on o f s t i m u l i . The m o d e l on l y i nd i rec t l y t rans la tes in to a f f e c t i v e and s e n s o r y pa in , thus conc lus ions must be ca re fu l l y d rawn to prevent m is lead ing genera l i za t ions about a l tered sensory and a f f e c t i v e pain (Craig & Coren , 1975). Clark (1969) and Feather, Chapman, and Fisher (1972) examined the p lacebo e f f e c t using analyses der ived f r o m sensory dec i s ion theo ry and conc luded that p lacebo a l tered sub jec ts ' response bias but not their s e n s i t i v i t y to thermal s t i m u l a t i o n . These researchers d i s t i ngu ished b e t w e e n c o g n i t i v e and sensory c o m p o n e n t s as p r o p o s e d by Feather et al . (1972) w h o argued that p lacebos "have a t t i tud ina l but not s e n s o r y e f f e c t s " (p. 15 293). In con t ras t , the an imal m o d e l s o f op ia te i n v o l v e m e n t and Melzack and Wa l l ' s G a t e - C o n t r o l T h e o r y suggest that p lacebos have more w i d e - r e a c h i n g and in te rac t ive e f f e c t s that cannot be eas i l y separated in to a t t i tud ina l and sensory f a c e t s . A l l t o l d , there appear to be severa l pain p a t h w a y s that are d i f f e r e n t i a l l y a f f e c t e d by p lacebos (and other man ipu la t i ons ) and it is not clear w h i c h p a t h w a y s are a f f e c t e d nor if on l y sub jec ts ' w i l l i n g n e s s t o repor t pain is a f f e c t e d . H o w e v e r , if w i l l i n g n e s s t o repor t pain is all that is a f f e c t e d by p l a c e b o s , then exper imen ta l research must ensure that the pain s t imu lus i n tens i t y is a m b i g u o u s l y p resen ted so that sub jec ts are less l i ke l y to behave in accordance w i t h exper imenta l d e m a n d . Persona l i t y Tra i ts as Exp lanat ions of Placebo E f f e c t s . Recall Beecher 's (1955) f i nd ing o f 35 + 2.2% response to p lacebo . Beecher (1955; 1959) r e c o m m e n d e d that these p lacebo responders shou ld be c o n t r o l l e d f o r ; i.e., exc luded in drug or t r e a t m e n t s tud ies . Thus began an ex tens ive search fo r the "p lacebo r e a c t o r " — t h e p e r s o n a l i t y t ype that responds w e l l t o p lacebos . Jospe (1978) summar ized s tud ies o f the p lacebo responder and conc luded that they are "anx ious , f i e l d dependent , ta lka t i ve , . . .emot iona l l y lab i le " , and acquiescent (p. 90). This i m p l i e s that they w o u l d be w i l l i n g t o alter their pain repor t (in SDT t e r m i n o l o g y ) . In c o n t r a s t , Evans ' r e v i e w (1974) conc luded that sub jec t s ' levels o f s u g g e s t i b i l i t y or responses to hypnos i s have turned out to be p o o r l y co r re la ted w i t h p lacebo response but that anx ie ty may be p red i c t i ve o f p lacebo response . The added e lement o f s i tua t iona l s t imu l i was f o u n d to in teract w i t h pe rsona l i t y in one s tudy . Sh ipman , Greene, and Laskin (1974) a t t e m p t e d to 16 de f ine the p lacebo reactor in 120 m y o f a s c i a l p a i n - d y s f u n c t i o n (MPD) pa t ien ts . S i tua t iona l c o n d i t i o n s (i.e. s t r o n g v. o rd inary p lacebo s u g g e s t i o n ) were f o u n d t o in teract w i t h p e r s o n a l i t y t y p e s (as measured by the M M P I , In te rpersona l A d j e c t i v e Check l i s t , and a m o d i f i e d Corne l l Med ica l Index). People rated as " h y p o c h o n d r i a c a l l y o r ien ted depress ives and h y s t e r i c s " accord ing to their MMPI p r o f i l e s appeared t o respond f a v o r a b l y to p l a c e b o s , espec ia l l y if there w a s a s t rong p lacebo sugges t ion (p. 481) . Norma ls t e n d e d to respond more to an ord inary p lacebo s u g g e s t i o n . In c o n t r a s t , p s y c h o p a t h i c and sch izo id persona l i t i es genera l l y fa i l ed to respond to ei ther k ind o f p lacebo s u g g e s t i o n . S o m e o f the p e r s o n a l i t y f a c t o r s wh ich cor re la te w i t h p lacebo response a lso cor re la te w i t h s e l f - r e p o r t e d pain (Parker, Doer f l e r , T a t t e n , and H e w e t t , 1983). In par t icu lar , the MMPI PT (Psychasthenia or a n x i e t y - r e l a t e d ) subscale has been f o u n d to be p o s i t i v e l y re la ted to the MPQ d i m e n s i o n o f a f f e c t i v e pain qua l i t ies . The SC (Schizophrenia or s c h i z o i d - r e l a t e d ) subsca le w a s n e g a t i v e l y re la ted t o a f f e c t i v e qua l i t ies o f pa in . Chronic pain pa t ien ts have been descr ibed as exh ib i t i ng "neurot ic charac ter is t i cs [ that ] cons is t o f h y p o c h o n d r i a s i s and d e p r e s s i o n " (Sternbach, 1974, p. 17). When these conc lus ions are cons idered in l ight o f the impor tan t ro le that e m o t i o n a l p rocesses p layed in the Sh ipman et a l . s tudy (descr ibed in the p rev ious paragraph) , it appears that anx ie ty is p o s i t i v e l y re la ted to bo th the s e l f - r e p o r t o f pain and p lacebo e f f e c t i v e n e s s , wh i l e sch izo id qua l i t ies are nega t i ve l y re la ted to s e l f - r e p o r t e d pain and p lacebo e f f e c t i v e n e s s . Parkhouse (1963) emphas ized s i tua t iona l f a c t o r s by suggest ing that w e all m a y be p lacebo reac tors g i ven the r ight c i r cums tances . It seems that 17 pa t ien ts may be bet ter p lacebo responders than exper imenta l sub jec ts due to higher anx ie ty and higher pain leve ls (Beecher, 1955; Evans, 1974); thus the r ight c i rcumstances f o r a p lacebo response may depend on bo th the s i tua t ion and i ts personal mean ing . It may be argued that chron ic pain pa t i en ts , espec ia l l y neuro t i ca l l y anx ious or depressed ones, w o u l d best respond t o p lacebos . A n x i e t y . Pain, and Placebo Response. A n x i e t y seems to resul t f r o m the c l in ica l pain exper ience and m a y in turn exacerbate pain (Craig, in p ress ; McGlashan, Evans, and Orne, 1969). A n x i e t y has been concep tua l i zed as a part o f the pain response by such researchers as Melzack and To rge rson (1971) w h o inc luded anx ie ty in the a f f e c t i v e d i m e n s i o n o f pa in . Craig (in p ress) c i ted it as a c o m m o n e m o t i o n a l c o n c o m i t a n t o f pa in . Ro l lman (1977) inc luded anx ie ty in a l is t o f var iab les wh ich al ter one's pain response . A n x i e t y is again imp l i ca ted in s tud ies seek ing to de f ine the p lacebo reactor in w h i c h b o t h pain and p lacebo e f f e c t i v e n e s s w e r e re la ted to an anxious pe rsona l i t y . Bonica (1979) sugges ted that anx ie ty and s t ress m a y be re la ted to p lacebo e f f e c t i v e n e s s , espec ia l l y f o r l o w t o modera te levels o f pain. It cou ld be that the expec ta t ion o f re l ie f induced by p lacebo serves to reduce anx ie ty w h i c h thereby reduces pa in . Hence, w e may all be po ten t ia l p lacebo reac tors i f anx ie ty is e l i c i t ed by the pain or by the s i tua t ion assoc ia ted w i t h pa in . (Beecher, 1975; Cra ig , in p ress ; Evans, 1974; Gry l l and Katahn, 1978; Melzack and W a l l , 1982). Learning Theory . Learning t h e o r y o f f e r s a tes tab le and p a r s i m o n i o u s mode l that can be appl ied to bo th an ima ls and humans. It encompasses s i tua t iona l c o m p o n e n t s by re fe r r ing t o one's past learning h i s t o r y as a 18 source o f be l i e f s or expec ta t ions sur round ing pa in fu l exper ience. The basic p r e m i s e s are that th rough respondent and operant c o n d i t i o n i n g , the p lacebo c o m e s to act as a d i sc r im inan t s t imu lus . Repeated pa i r ings o f a t rea tment w i t h pain reduc t ion may resul t in that t rea tmen t tak ing on the f u n c t i o n o f a d i sc r im inan t s t imu lus . A s i m i l a r - a p p e a r i n g t r e a t m e n t , s e t t i n g or s i tua t ion w o u l d therea f te r e l ic i t pain reduc t i on . In a d d i t i o n , the e f f e c t s w o u l d be expec ted to gradual ly ex t ingu ish i f not re in fo rced o c c a s i o n a l l y w i t h e f f e c t i v e t rea tmen t (Wick ramasekera , 1980). A t t e m p t s have been made to unders tand w h i c h c o m p o n e n t s o f pain are changed by p lacebos and wh ich s i tua t iona l s t imu l i serve as the m o s t sa l ient d i s c r i m i n a t i v e s t i m u l i . It is not en t i re l y clear h o w p lacebos a f f e c t the var ious pain c o m p o n e n t s , wh ich is unders tandable since the pain c o m p o n e n t s are t h e m s e l v e s unclear and they l i ke ly interact w i t h one another . Never the less , the use o f mu l t ip le measures o f pain w i l l beg in t o address th is issue. S i m i l a r l y , the m o s t sa l ient s t imu lus charac ter is t i cs that e l i c i t a p lacebo response have yet to be adequate ly de l ineated . Suppor t f o r the c lass ica l c o n d i t i o n i n g approach has c o m e f r o m bo th animal and human s tud ies . The animal s tud ies do not i nvo l ve pa in , but rather f o c u s on cond i t i on ing t o the in jec t ion o f a drug. S i m i l a r l y , human s tud ies o f c o n d i t i o n i n g a p lacebo e f f e c t began w i t h c o n d i t i o n i n g responses t o d rugs , but recent s tud ies have f o c u s e d on the p lacebo e f f e c t in pa in . A n i m a l Stud ies. Herrnste in (1962) d r e w impor tan t analog ies be tween c lass ica l c o n d i t i o n i n g o f an an imal 's behav iour in a labora to ry and a pa t ien t ' s behav iour in a d o c t o r ' s o f f i c e . He suggested that c lass ical c o n d i t i o n i n g may expla in w h y a pa t ien t ' s s y m p t o m s s o m e t i m e s decrease at 19 the mere s ight o f a d o c t o r a n d / o r med ic ine . His an imal c o n d i t i o n i n g m o d e l w a s p r o p o s e d as a s i m p l i f i e d v e r s i o n o f what migh t occur in human pa t ien ts . S u p p o r t i v e s tud ies inc luded one w i t h rats w h o exh ib i ted a dep ress ion in b a r - p r e s s i n g w i t h s c o p o l a m i n e i n j e c t i o n s ; a s im i la r reduc t ion in rate subsequen t l y occur red w i t h sal ine i n jec t i ons . This e f f e c t ex t ingu ished over t i m e and genera l ly seemed to c o n f o r m t o the c lass ica l c o n d i t i o n i n g p a r a d i g m . S h o r t l y the rea f te r , d - A m p h e t a m i n e , w h i c h increases a c t i v i t y in ra ts , w a s s h o w n t o be e f f e c t i v e in c o n d i t i o n i n g an increase in a c t i v i t y w i t h sal ine i n jec t i ons (Ross and Schni tzer , 1963). More r e c e n t l y , Pihl and A l t m a n (1971) s tud ied c o n d i t i o n e d responses t o d - A m p h e t a m i n e and ch lo rp romaz ine , drugs that increase and decrease a c t i v i t y , r e s p e c t i v e l y . In a d d i t i o n , they examined the d i f f e r e n t i a l e f f e c t o f the number o f learning t r i a l s . A p lacebo e f f e c t w a s ob ta ined f o r d - A m p h e t a m i n e w i t h a greater number o f learning t r ia ls leading t o a greater res is tance t o e x t i n c t i o n . In c o n t r a s t , ch lo rp romaz ine resu l ted in an o p p o s i t i o n a l e f f e c t ; ins tead o f p o s t - d r u g t r ia ls e l i c i t i ng decreased a c t i v i t y , the a c t i v i t y increased or " rebounded" to levels above base l ine . The i nves t i ga to rs p r o p o s e d that "the a p p l i c a b i l i t y o f the c o n d i t i o n i n g mode l m a y be re la t i ve t o the nature o f the ac t i ve substance u t i l i z e d " (p. 94). Human S tud ies . In c o m p a r i s o n to animal s tud ies , the level o f c o m p l e x i t y increases s t i l l fu r ther w h e n human s tud ies are analyzed because, bes ides c o n d i t i o n i n g t o an "exper imenta l chamber " or d o c t o r ' s o f f i c e , there m a y be c o m p l e x expec tancy e f f e c t s generated by one's pr io r exper ience w i t h d o c t o r s and m e d i c i n e s , the dura t ion o f i l l ness , the present charac te r i s t i cs o f the therapeut ic s e t t i n g , and so on (G l iedman, Gant t , & 20 T i e t e l b a u m , 1957; Her rns te in , 1962; W i c k r a m a s e k e r a , 1980). In a s m a l l - s c a l e s t u d y , Lang and Rand (1969) d e m o n s t r a t e d a c o n d i t i o n e d p lacebo response to g l yce ry l t r i n i t ra te , an ant iangina l m e d i c a t i o n that increases heart ra te . On ly 3/8 o f their sub jec ts had a substant ia l increase in heart rate (15 beats or more per m i n u t e ) when g iven the actual m e d i c a t i o n . These three sub jec ts were then g iven the m e d i c a t i o n da i ly f o r about 25 sess ions , except that on t w o occas ions a s i m i l a r - a p p e a r i n g and - t a s t i n g p lacebo w a s g i v e n . D o u b l e - b l i n d procedures m i t i g a t e d the p o s s i b i l i t y o f subject or exper imenter b ias. Tachicard ia w a s d e m o n s t r a t e d in the p lacebo sess ions , but t o a lesser degree than the average m e d i c a t i o n response . These researchers c i ted another s tudy that ind ica ted that "the analgesic e f f e c t i v e n e s s of a p lacebo w a s s i g n i f i c a n t l y greater w h e n it w a s g i ven af ter a ve ry ac t ive analgesic than a f ter a less po ten t one or another p l a c e b o " (p. 914 ; Kantor , Sunshine, Laska, Me isner , and Hopper , 1966). Kantor et a l . (1966) s tud ied the d i f f e ren t i a l e f f e c t i v e n e s s o f three k inds o f analgesics and p lacebo in reduc ing pain in pat ien ts w i t h f rac tu res or pos tsu rge ry . The analgesic ( A s p i r i n , code ine , or pen tazoc ine ) or p lacebo w a s g iven in the m o r n i n g one day, and p lacebo w a s g iven at the same t i m e the next day . When p lacebo f o l l o w e d p lacebo , pain repor t w a s reduced by a lmos t the same amount on bo th days . When p lacebo f o l l o w e d an e f f e c t i v e analgesic , pain repor t was again reduced w i t h p lacebo , but to a greater degree compared t o the pain repor ts o f pa t ien ts g iven p lacebos on bo th days . The analgesics tended t o reduce pain repor ts m o s t subs tan t ia l l y . One p r o b l e m w i t h th is s tudy w a s that "many of the pa t ien ts 21 w i t h adverse reac t ions to the f i r s t drug rece ived p lacebo the f o l l o w i n g day and did no t exper ience adverse e f f e c t s " (p. 453) and so the pat ients may have deduced that they w e r e g i ven s o m e t h i n g weaker than the f i r s t m e d i c a t i o n . H o w e v e r , a separate research g roup reached d i f f e r e n t conc lus ions w i t h d i f f e r e n t m e d i c a t i o n s . R icke ls , L i p m a n , and Raab (1966) a lso a t tempted to de te rmine the c o n d i t i o n i n g e f f e c t s o f learning h i s to r ies but w i t h p s y c h o t r o p i c med ica t i ons . Pat ients w h o had exper ience w i t h several m e d i c a t i o n s over the past severa l y e a r s , or w i t h an ac t i ve med ica t i on in a c r o s s - o v e r drug s tudy , were bet ter able to d is t ingu ish that the p lacebo had l i t t l e e f f e c t i v e n e s s and the re fo re ended up w i t h lower i m p r o v e m e n t ra t ings a f ter the p lacebo m e d i c a t i o n . In con t ras t , pat ients w i t h l i t t le pr ior exper ience or w i t h an ear l ier inac t i ve m e d i c a t i o n s h o w e d bet ter i m p r o v e m e n t t o p lacebo. This runs counter to the c o n d i t i o n i n g hypo thes i s , p o s s i b l y because p s y c h o t r o p i c m e d i c a t i o n s t y p i c a l l y have ve ry percept ib le s ide e f f e c t s . Never the less , accord ing t o the c o n d i t i o n i n g hypo thes i s , s ide e f f e c t s shou ld a lso be c o n d i t i o n a b l e , a l thought maybe not in just one learning t r i a l . On the other hand, ana lges ics have less sal ient s ide e f f e c t s than p s y c h o t r o p i c s and the re fo re may not be d is t ingu ishab le f r o m p lacebos. These issues cou ld have been addressed in a p o s t - e x p e r i m e n t a l ques t ionna i re or a m e d i c a t i o n s ide e f f e c t s check l is t t o de termine if the sub jec ts guessed that they had rece ived a p lacebo. S o m e recent s tud ies have examined the e f f e c t s o f p lacebo and analges ics on the d i f f e r e n t c o m p o n e n t s o f pain w h i c h a f f o r d s a super ior unders tand ing o f bo th p lacebos and pain . Using the Sensory and 22 Unpleasantness Scales, denta l pa t ien ts ra ted the magn i tude o f pa in fu l e lec t r ica l s t i m u l a t i o n o f t o o t h pulp (Grace ly , McGra th , and Dubner, 1979, 1982). A n in jec t i on w a s g iven and sub jec ts w e r e i n f o r m e d that it cou ld be ei ther a seda t i ve (not an analges ic) or a p lacebo. The seda t i ve w a s actua l ly a narco t ic ( f en tany l ) wh ich s i g n i f i c a n t l y reduced pain as measured by the S e n s o r y Scale. Placebo had v i r t u a l l y no e f f e c t on the Sensory Scale ra t ings . On the Unpleasantness Sca le , the narco t ic resu l ted in no change wh i l e the p lacebo did resul t in a decrease o f pain (but th is w a s not s t a t i s t i c a l l y s ign i f i can t ) . The la t ter s tudy (Gracely et al . , 1982) c o n t r o l l e d f o r the poss ib le bias o f p lacebo not causing s ide e f f e c t s by g iv ing d iazepam to all sub jec ts be fo re the fen tany l or p lacebo i n j e c t i o n ; thus all sub jec ts p o t e n t i a l l y perce ived s ide e f f e c t s . In an a t tempt to de termine if c o m m o n l y c i ted s i tua t iona l f a c t o r s a f f e c t the degree o f p lacebo response, Gry l l and Katahn (1978) s tud ied 160 oral surgery pat ien ts w h o rece ived a p lacebo pi l l p r ior to an in jec t i on o f local anaesthet ic . Three o f the four independent var iab les s e e m e d large ly i n e f f e c t i v e in e f f e c t i n g a p lacebo response ; n a m e l y , the status o f c o m m u n i c a t o r o f drug e f f e c t s , a t t i tude o f den t i s t , [and] a t t i tude o f dental techn ic ian .... Enthusiast ic message o f drug e f f e c t s produced s t a t i s t i c a l l y and c l i n i ca l l y s ign i f i can t reduc t ions in p o s t p l a c e b o fear o f in jec t ion and s ta te anx ie ty and m a r k e d l y lower ra t ings o f pain exper ienced dur ing in jec t ion o f local anesthet ic (p. 253). This w a s a w e l l - d e s i g n e d and thorough s t u d y , but there w e r e so many var iab les that even the authors a d m i t t e d that some analyses were t o o c o m p l e x t o be mean ing fu l . Future research should f o l l o w Gry l l and Katahn's lead in address ing s i tua t iona l f a c t o r s a f f e c t i n g p lacebo response as w e l l as pos tp lacebo changes in fear and anx ie ty . 23 One area that is rece iv ing a t ten t i on i nvo lves sub jec t var iab les that m a y a f f e c t one's p lacebo response. The search f o r p e r s o n a l i t y t ra i ts has been abandoned, but n o w sub jec t var iab les such as learn ing h i s t o r y have b e c o m e a new f o c u s . In a c lever a t t e m p t t o s imu la te a learning h i s to ry in the l abo ra to ry , Voudour i s , Peck, and Co leman (1985) pa i red several t r ia ls o f a p lacebo cream w i t h a pain s t imu lus that w a s increased or decreased in i n tens i t y whenever the c ream w a s app l ied . Th is p r o v i d e d a learning h i s t o r y f o r the subjects in wh ich the p lacebo c ream and pain exper ience a f f e c t e d thei r subsequent repo r t s o f pain in tens i t y . In p rev ious s tud ies pain i n tens i t y w a s not man ipu la ted d i r e c t l y , but rather s u b j e c t s ' expec ta t ions o f a change in in tens i t y were man ipu la ted . Since the present s tudy a t t e m p t e d to rep l icate and ex tend their f i n d i n g s , the Voudour i s et a l . s tudy w i l l be descr ibed in de ta i l . The Voudour i s . Peck, and Co leman Study T h i r t y - t w o subjects w e r e ass igned to one o f f ou r g roups , t w o groups f o r positive conditioning ( resu l t ing in pain reduc t ion "congruent w i t h expec ta t ions o f r e l i e f " ) and t w o groups f o r negative conditioning ( resu l t ing in pain in v i o l a t i o n o f expec ta t ions o f re l i e f ) . The pain s t imu lus w a s an i o n t o p h o r e t i c pain generator . " I on tophores i s uses the repu ls ion o f the p o s i t i v e p o t a s s i u m (K) ions by the p o s i t i v e po le o f a d i rec t e lec t r ic current t o d r ive the ions in to the s k i n " (Benjamin and He lvey , 1963, p. 567). The apparatus appears s imi la r to a shock e lec t rode . S t imu l i w e r e rated on a scale o f 0 (no pain) t o 10 ( in to lerab le pa in) . On day one a range of pain s e n s i t i v i t y w a s de te rm ined f o r each sub jec t by admin is te r ing an ascending and descending ser ies o f pain s t imu l i 24 to the f o r e a r m . Next a pretest w a s a d m i n i s t e r e d . This c o n s i s t e d o f the repeated a d m i n i s t r a t i o n o f one level o f the nox ious s t imu lus f o r a t o t a l o f 20 t r ia l s (in b locks o f 5) , at the f o l l o w i n g in tens i t y l e v e l s : 1. Level 5 o f the sub jec t 's ra t ing scale f o r group I, 2. Level 8 o f the sub jec t 's ra t ing scale f o r group I I , 3. Level 2 o f the sub jec t ' s ra t ing scale f o r group I I I , and 4. Level 5 o f the sub jec t 's ra t ing scale f o r group IV. S ta r t i ng w i t h a n o - p l a c e b o b l o c k , the b locks o f t r ia ls a l te rna ted w i t h n o - p l a c e b o and p lacebo b l o c k s . The p lacebo cream w a s desc r ibed as a " p a i n - k i l l e r " and as an " e f f e c t i v e and conven ien t local anaes the t i c " (p. 50). The next day sub jec ts were again g iven s t imu l i w i t h and w i t h o u t the p lacebo c ream in b locks o f 5 t r i a l s each f o r a t o ta l o f 70 t r i a l s . H o w e v e r , in th is sess ion all t r ia ls g i ven w i t h the p lacebo cream w e r e g iven at a man ipu la ted in tens i t y (designed to c o n d i t i o n sub jec t s ) as f o l l o w s ; groups I and II rece ived nox ious in tens i t i es that had been ra ted p r io r to the p re tes t as 3 scale p o i n t s b e l o w thei r p re tes t leve l , w h i l e groups III and IV rece i ved in tens i t ies that w e r e 3 p o i n t s above their pre test level (see Table 1). Thus groups I and II w e r e p o s i t i v e l y c o n d i t i o n e d (the p lacebo w a s pa i red w i t h pain reduc t i on ) ; g roups III and IV w e r e nega t i ve l y c o n d i t i o n e d (the p lacebo had an adverse e f f e c t ) . In a th i rd and f ina l s e s s i o n , the pre tes t was repea ted . That is , 20 t r ia ls w e r e g i v e n , hal f w i t h and hal f w i t h o u t the p lacebo c r e a m , all at the one p re tes t level o f i n tens i t y . Table 1. S t imu lus In tens i t y Levels f o r the Voudour i s et a l . s tudy GROUP I II I I I IV PRETEST 5 8 2 5 CONDITIONING 2 5 5 8 POSTTEST 5 8 2 5 26 In genera l , the resu l ts w e r e in the p red ic ted d i r e c t i o n s . S ign i f i can t d i f f e r e n c e s were ob ta ined b e t w e e n groups II and IV (w i th respec t i ve pre test and manipu la ted levels in the high end o f the ra t ing sca le ; i.e., f o r Group II the p r e - and p o s t t e s t level w a s 8 and the man ipu la ted level w a s 5; f o r Group IV the p r e - and p o s t t e s t level w a s 5 and the man ipu la ted level was 8). These resu l ts i m p l y that sub jec ts c o n s i s t e n t l y d i f f e r e n t i a t e d be tween in tens i t ies on ly in the upper p o r t i o n o f the sca le . Thus a d i f f e rence o f 3 scale po in ts in the upper end o f the scale m a y have been m o r e percept ib le than a d i f f e r e n c e of 3 po in t s in the l ower end . A n o t h e r i n te res t ing f i nd ing w a s that s i m p l y app ly ing the p lacebo c ream e f f e c t e d a decrease in pain repor t pr ior t o c o n d i t i o n i n g , sugges t ing an expec tancy e f f e c t . The m e t h o d o l o g y w a s innova t i ve and seemed to s a t i s f a c t o r i l y tes t f o r c o n d i t i o n i n g e f f e c t s . H o w e v e r , a f e w i m p r o v e m e n t s cou ld have been made. There were o n l y 12 males in c o m p a r i s o n to 20 f e m a l e s , t he re fo re there were not enough o f e i ther sex to tes t or balance f o r sex d i f f e r e n c e s . It w a s not s ta ted whether sub jec ts were r a n d o m l y ass igned t o groups or i f g roups were balanced f o r sex. The lack o f a con t ro l group to assess sess ion e f f e c t s w a s remed ied by running a p i l o t s tudy (N = 6 ) wh ich s h o w e d that increas ing pain s t imu lus i n tens i t y resu l ted in a l inear f u n c t i o n (as measured by the 1 1 - p o i n t ra t ing sca le ) and there were no sess ion e f f e c t s . H o w e v e r , 6 sub jec ts were not enough to es tab l ish the measurement p r o p e r t i e s o f the ra t ing sca le , hence man ipu la t ing s t imu lus in tens i t ies by increas ing or decreas ing by a cons tant value of 3 scale po in ts may have caused d i f f e r e n t i a l e f f e c t s . A t t e m p t s to c o n d i t i o n p o s i t i v e or negat ive e f f e c t s m a y not have been comparab le . 27 Ratio sca les are ava i lab le ( for examp le , Grace ly , M c G r a t h , and Dubner, 1978, have va l i da ted and de te rm ined the re l i ab i l i t y o f ra t io pain sca les) . M u l t i p l e measures w o u l d have helped t o unders tand w h i c h c o m p o n e n t s o f pain w e r e be ing in f luenced by the c o n d i t i o n i n g p rocedures . Never the less , the use o f the sub jec t s ' o w n rat ings o f in tens i t y is to be c o m m e n d e d s ince the a l te rna t i ve o p t i o n — t h a t o f us ing the same s t imu lus in tens i t ies f o r al l s u b j e c t s — w o u l d have been inappropr ia te fo r pain s e n s i t i v i t y g iven i ts i d i o s y n c r a t i c nature. The use of one con t inuous level o f s t i m u l a t i o n in all tes t t r ia ls seems o v e r l y s i m p l i s t i c because sub jec ts w o u l d have been g iv ing the same pain ra t ing over and over again. Subjec ts may have guessed the h y p o t h e s i s i f th is were o b v i o u s desp i te the researchers ' unsuppor ted c la im that " [ s ]ub jec ts were unaware that s t i m u l a t i o n leve ls w e r e m a n i p u l a t e d " (p. 47). The i nves t i ga to rs sugges ted severa l in teres t ing i m p l i c a t i o n s o f a pa t ien t ' s learn ing h i s to ry on subsequent response to m e d i c a t i o n and the t r e a t m e n t s e t t i n g . The issue o f us ing an analogue p o p u l a t i o n w a s adep t l y de fended b y re fe rence to the p rev ious f i nd ing that analogue popu la t i ons t y p i c a l l y r e s p o n d /ess to p lacebos than c l in ica l pa t ien ts do . In a d d i t i o n , the authors encouraged rep l i ca t ion and ex tens ion o f thei r f i n d i n g s to c l in ica l p o p u l a t i o n s ; they sugges ted fu r ther quan t i f i ca t i on o f the mode l to de termine the number o f learning t r ia ls that are necessary and the maintenance o f the e f f e c t over t i m e . The present i nves t i ga t i on a t t e m p t e d t o rep l ica te and ex tend the f i n d i n g s us ing d i f f e r e n t dependent measures , a d i f f e r e n t pain s t i m u l u s , and an abbrev ia ted p rocedure . 28 S ta temen t o f the P r o b l e m : Measurement Issues and Hypo theses The cho ice o f dependent measures is c r i t i ca l in the fu l l assessment o f exper imenta l e f f e c t s . A recent t rend in behavioura l assessment is to ins is t upon mu l t i p le measures so that exper imenta l or t r e a t m e n t e f f e c t s are f a i r l y rep resen ted . Fur thermore , the use of mu l t ip le measures in pain research r e f l e c t s the v i e w that pain is m u l t i d i m e n s i o n a l and that the p lacebo m a y have d i f f e r e n t i a l e f f e c t s across the pain c o m p o n e n t s . Wh i le a fu l l assessment w o u l d include the sub jec t i ve ( s e l f - r e p o r t ) , behav iou ra l , and p h y s i o l o g i c a l aspects o f pain (Phi l ips, 1983), the f o c u s here has been on the f o r m e r t w o aspects o f pain w h i c h emphasize the c o m m u n i c a t i v e or express ive f a c e t s . The hypo thes ized e f f e c t s o f a p lacebo on the var ious c o m p o n e n t s o f pain express ion w i l l be d iscussed at the end o f th is s e c t i o n . Measurement Verbal Report . Verbal repor t remains the p redominan t c l in ica l assessment t o o l and severa l researchers have a t t e m p t e d t o dev ise s o p h i s t i c a t e d and conven ien t s e l f - r e p o r t quest ionna i res (Melzack, 1983). The McGi l l Pain Ques t ionna i re (MPQ, Melzack, 1975) is a major ques t ionna i re deve loped t o tap the s e n s o r y , a f f e c t i v e , and eva luat ive d i m e n s i o n s o f pa in . Wh i le it has been w e l l - v a l i d a t e d and seems re l iab le , it is t o o c u m b e r s o m e f o r l abora to ry use s ince the sub jec ts must rate thei r pain on 21 subca tegor ies w i t h each subca tegory requi r ing d i s c r i m i n a t i o n a m o n g a number o f ad jec t i ves . A less c u m b e r s o m e verbal measurement technique that is conven ien t f o r l abora to ry use w a s deve loped by Grace ly , McGra th , and Dubner (1978a). 29 T w o ra t io scales o f 15 w o r d s each measure the senso ry and a f f e c t i v e (or unp leasantness) d imens ions o f pa in . The subject s i m p l y scans each l ist and chooses one w o r d f r o m each that best descr ibes the present pa in . The verbal pain desc r ip to rs w e r e o r ig ina l l y sca led and va l ida ted by sub jec ts us ing "numer ica l magni tude e s t i m a t i o n and . . . c ross -moda l i t y [match ing ] to h a n d - g r i p f o r c e " (p. 5). The de r i ved ra t io sca les were then used s u c c e s s f u l l y in f o l l o w - u p s tud ies and w e r e found to d i f f e r e n t i a l l y re f l ec t pha rmaco log i ca l pain con t ro l agents . (Gracely et al . , 1978b, 1979; He f t , Grace ly , Dubner, and McGra th , 1980). (See Append ix A f o r the scales and the i r co r respond ing ra t io values.) Of re levance to the present i nves t i ga t i on was the f i nd ing (Gracely et al. , 1979, 1982) that these scales d i f f e r e n t i a t e d b e t w e e n p lacebo response and narco t ic ana lges ia ; p lacebo a l tered pain repor ts on the Unpleasantness Scale but not on the Sensory Scale. Fur thermore, p lacebo response and c o n d i t i o n i n g e f f e c t s were expected t o be bet ter i l lus t ra ted by the Unpleasantness Scale than by the Sensory Scale s ince the a f f e c t i v e c o m p o n e n t o f pain is more l i ke ly t o be a f f e c t e d by p s y c h o l o g i c a l man ipu la t ions (Gracely et al . , 1979, 1982; Pr ice, 1984). Whi le there have been s o m e quest ions about re l i ab i l i t y and other p s y c h o m e t r i c p roper t ies o f these scales (W. Hal l , 1981), they have been ably de fended (Gracely & Dubner, 1981). These scales have s i m i l a r l y p roven to be re l iable and va l id in Craig's l abora to ry and were the re fo re used in the present s tudy . The scales genera l ly re f lec t pain s t imu lus i n t e n s i t y , are p o s i t i v e l y re lated to each other and to other pain measures , and have resu l ted in high interrater re l iab i l i t i es (Craig & Patr ick , 1985; Hyde, 1986; Lee, 1985; Patr ick et al. , 30 1986). Verbal repor t appears t o have a number o f l i m i t a t i o n s in pain measuremen t . There are the c o m m o n p r o b l e m s o f any sub jec t i ve response (e.g., exper imen te r b ias , demand charac te r i s t i cs ) as w e l l as " s o c i a l , cul tural and e c o n o m i c f a c t o r s " that in f luence s e l f - r e p o r t e d pain ( B r o m m , 1984, p. 7; Craig and Prkachin, 1983). Fur thermore , pa t ien ts w h o are unable t o use language mus t be assessed by means o f nonverba l measures . Nonverba l Measures. Researchers are inc reas ing ly a i m i n g to o b j e c t i f y pa in repor t us ing nonverba l p h y s i o l o g i c a l approaches such as measur ing "per ipheral nerve a c t i v i t y , w i t h d r a w a l re f l exes , sk in res is tance reac t i ons , e v o k e d p o t e n t i a l s , and changes in the e l e c t r o e n c e p h a l o g r a m " ( B r o m m , 1984, p. 12). Nonverba l c o m m u n i c a t i o n o f pain has also been a f o c u s . Fordyce (1976a, 1976b, 1977; Fo rdyce , Fowler , and DeLateur, 1975) p r o p o s e d the measurement o f "pain b e h a v i o u r s " ; Craig and Prkachin (1978) p r o p o s e d the measurement o f fac ia l m o v e m e n t s . Each o f these w i l l be d iscussed b e f o r e examin ing the i m p l i c a t i o n s o f measurement o f p lacebo e f f e c t s . Fo rdyce (1977) suggested that one should "analyse the s y s t e m a t i c consequences t o pain and w e l l b e h a v i o r " o f any in te rven t ion t o d i scove r if " learn ing f a c t o r s " are ma in ta in ing pain behaviour (p. 278). A c t i v i t y levels and the use o f analgesics w e r e t w o pain behaviours advoca ted to assess o u t c o m e o f t r e a t m e n t . Fordyce took an ex t reme stance by measur ing over t behav iours and not e m o t i o n s or c o g n i t i o n s despi te his sugges t i on that his m o d e l is p r o p o s e d f o r " p s y c h o g e n i c " pain in wh ich Fordyce c la ims there are p s y c h o l o g i c a l rather than phys ica l causes. Never the less , his d i s t i n c t i o n 31 be tween operant pain and respondent pain h igh l igh ts his cogent exp lana t ion of h o w p s y c h o l o g i c a l f a c t o r s may b e c o m e i n v o l v e d in what began as a d is rup ted phys io log i ca l s ta te . In Fordyce 's f o r m u l a t i o n , pain behav iours (such as rubb ing the a f f e c t e d area, m o a n i n g , and tak ing t i m e o f f w o r k ) m a y receive r e i n f o r c e m e n t in the f o r m o f a t t e n t i o n , s y m p a t h y , or re lease f r o m u n s a t i s f y i n g w o r k du t ies . Pain behaviours then serve as c r i te r ia by wh ich to measure pain b e f o r e , dur ing , and a f te r t r e a t m e n t . T rea tment is f o c u s e d upon a l te r ing pain behav iours (such as c o m p l a i n t , a v o i d a n c e , and m e d i c a t i o n - u s e ) and increasing w e l l behav iours (such as w a l k i n g and exerc is ing) . Whi le these behav iours may be va l i d f o r measur ing the behavioura l aspect o f c l in ica l pain (Phi l ips, 1983), they are less appropr ia te fo r measur ing pain in the labora to ry sub jec t w h o usual ly is not f ree to get up and w a l k , rub the pa in fu l area, and so o n . Indeed, behav iou r i s t s are m o v i n g away f r o m the s t r i c t adherence to measur ing on l y observab le events t o w a r d s an acceptance o f unobservab le events w h e n " c o m m o n sense d ic ta tes that p r iva te internal events m a y act as impor tan t de te rm inan ts o f behav io r " (Strosahl and Linehan, 1986, p. 16). One subset o f read i ly observab le c o m m u n i c a t i v e behav iours that can be used in labora to ry or c l in ica l s tud ies is facial expression. In 1872, Darwin (1965) p roposed a concep tua l i za t ion o f fac ia l express ion that remains w i d e l y accepted (w i th one notab le excep t ion ) . He suggested that our fac ia l express ions are hab i tua l ly exh ib i ted dur ing psycho log i ca l s ta tes . The e m o t i o n s in par t icu lar were assoc ia ted w i t h s p e c i f i c , d i sc r im inab le fac ia l express ions that are not eas i ly masked . T ry ing to dece ive o thers m a y e l i c i t a te l l t a le express ive m o v e m e n t that can be in te rp re ted by o thers as 32 d e c e p t i o n . He p r o p o s e d that c o m m u n i c a t i v e fac ia l express ions may have e v o l v e d f r o m func t iona l m o v e m e n t s such as b i t ing an e n e m y ; f l a t t e n i n g the ears may prevent t hem f r o m g e t t i n g chewed or may brace the inner ear against damag ing loud sounds ( A n d r e w , 1965; Da rw in , 1965). Mak ing a b i t i ng m o t i o n may c o m m u n i c a t e in tended a g g r e s s i o n ; a subsequent e a r - f l a t t e n i n g m o v e m e n t in an opponen t m a y signal s u b m i s s i v e de fea t . The ent i re c o m m u n i c a t i v e exchange w o u l d lessen b loodshed and w o u l d thus be adapt ive in s u r v i v a l . Zajonc (1985) recen t l y cha l lenged the Darwin ian approach in a p r o v o c a t i v e r e f o r m u l a t i o n o f Waynbaum's (1906) t h e o r y . Perhaps c o n s t r i c t i o n o f fac ia l muscu la ture dampens venous b l o o d return thereby increas ing cranial tempera tu re w h i c h a l ters neuro t ransmi t te r re lease. This m a y then change e m o t i o n a l tone . This t heo ry is f a l s i f i a b l e w h i c h makes it p o t e n t i a l l y more usefu l than Darwin 's theo ry . H o w e v e r , one o b v i o u s s h o r t c o m i n g is that Za jonc imp l ies that cranial tempera tu re is eas i l y a l te red . In f a c t , cranial tempera tu re is a f u n d a m e n t a l l y h o m e o s t a t i c s y s t e m wh ich rece ives a ma jo r p o r t i o n o f the b o d y ' s b l o o d supp ly . It is d i f f i c u l t t o encorpora te Za jonc 's v i e w in th is regard . Wh i le th is debate remains unse t t l ed , s l o w - a c t i o n v i d e o t a p i n g has a l l o w e d sc ien t i s t s t o s tudy fac ia l m o v e m e n t s in a s y s t e m a t i c manner. Ekman and Friesen (1982) d e v e l o p e d a "descr ip t ive measurement s y s t e m " based upon the v i s i b le musc le m o v e m e n t s o f the face . Musc le m o v e m e n t s that cou ld be re l iab ly d i s t i ngu ished by observers were i den t i f i ed and re ta ined in a comprehens i ve s y s t e m . A to ta l o f 44 "ac t ion u n i t s " (AUs) w e r e d e f i n e d , m o s t o f t h e m based on s ingle m u s c l e s ; but where t w o or 33 three musc les appeared to m o v e as a s ing le uni t , t hey w e r e c l a s s i f i e d as one A U . This s y s t e m , ca l led the Facial Action Coding System (FACS), is o b j e c t i v e and has been s h o w n t o be a re l iab le and va l i d t o o l in the d i f f e r e n t i a t i o n o f e m o t i o n s (Ekman, Friesen and E l l s w o r t h , 1982). W i t h regard t o v a l i d i t y , Ekman and Friesen (1982) repo r ted that fac ia l ac t ion i n tens i t y w a s "highly co r re la ted w i t h EMG readings (Pearson R = .85)" and thus may be a va l id rep lacement f o r p h y s i o l o g i c a l assessment (p. 208). A t least f i v e e m o t i o n ca tegor ies have been re l iab ly i d e n t i f i e d c r o s s - c u l t u r a l l y on the basis o f fac ia l exp ress ion : happ iness , f e a r / s u r p r i s e , anger, d i s g u s t / c o n t e m p t , and sadness. Thus, hope has been generated that th is s y s t e m m a y be a universal and ob jec t i ve t o o l in i d e n t i f y i n g e m o t i o n s . FACS has p roven valuable in the measurement o f pain (Craig & Prkachin, 1983) and w a s used in the present i n v e s t i g a t i o n . LeResche (1982) descr ibed a p r o t o t y p i c pain express ion that appeared in newspapers and magaz ines as c o m p r i s i n g A U s 4 + (6 or 7 or 11) + 20 + (25 or 26 or 27) + 43. (See Append ix B f o r table o f A U desc r ip t i ons . ) S tud ies i n v o l v i n g l a b o r a t o r y - i n d u c e d pain have g rea t ly ex tended LeResche's p r e l i m i n a r y f i nd ings . Craig and Patr ick (1985) f o u n d the f o l l o w i n g A U s t o occur m o s t f requen t l y dur ing the c o l d - p r e s s o r pain exper ience : 6 / 7 , 10, 12, 25, 2 6 / 2 7 , and 43 /45 . A s t e p w i s e mu l t ip le regress ion ana lys is suggested that the f o l l o w i n g A U s best p red ic ted sub jec t i ve d is t ress at the onset o f an acute pain exper ience: 2 6 / 2 7 , 6 /7 , 12 and 5. S i m i l a r l y , in a s tudy us ing phasic e lec t r ic shock, Pat r ick , Craig and Prkachin (1986) f o u n d the f o l l o w i n g A U s to occur mos t f r e q u e n t l y dur ing pa in : 4 , 6, 10 and 45. These same A U s were entered in a s t e p w i s e mu l t i p l e regress ion ana lys is w h i c h 34 ind icated that these A U s accounted f o r about 55% o f the var iance in naive j udges ' ra t ings o f the pain that the v i d e o t a p e d sub jec ts w e r e exper ienc ing . In s u m m a r y , the f o l l o w i n g A U s were h igh ly co r re la ted w i t h the c o m m u n i c a t i o n o f pa in fu lness in at least t w o pain s tud ies : A U s 4 ( lowered b r o w ) , 6 or 7 (squint ing o f the l ower e y e l i d ) , 10 ( ra is ing the upper l ip ) , 25 or 26 or 27 (mouth g r imac ing ) , and 43 or 45 (eyes b l ink ing) . Hyde (1986) extended the i nves t i ga t i on o f fac ia l pain express ion to a c l in ica l p o p u l a t i o n . She v i d e o t a p e d b a c k - p a i n pa t ien ts w h o w e r e undergo ing a phys io the rapy examina t i on . Hyde 's f i n d i n g s suppor ted the labora to ry research ; the A U s that p red ic ted s e l f - r e p o r t e d pain were A U s 4, 6, 7, 10, 25, and 43. These c lear ly encompass the same fac ia l c o m p o n e n t s as summar ized in the p rev ious research and na r rows the gap b e t w e e n analogue and c l in ica l pain research. A s im i la r array o f A U s w a s expected t o be d isp layed by sub jec ts in the present i n v e s t i g a t i o n . Thus, t w o verbal pain measures (the Sensory and Unpleasantness Sca les) as w e l l as one nonverba l measure ( facia l a c t i v i t y ) were chosen . S o m e ev idence regard ing the d i f f e r e n t i a l e f f e c t s o f psycho log i ca l man ipu la t ions w i l l n o w be p resen ted . P lacebo 's Var iable E f f e c t s on Pain C o m p o n e n t s . A l l o f the s tud ies r e v i e w e d have r e l i e d . so le l y upon verbal repor t in measur ing p lacebo e f f e c t s in humans. Never the less , s o m e general conc lus ions can be d rawn regard ing sensory and a f f e c t i v e pain repo r t s . Price (1984), Price and Barber (1987), and Gracely et a l . (1979, 1982) agreed that p s y c h o l o g i c a l or s i tua t iona l f a c t o r s are more l i ke ly to al ter a f f e c t i v e rather than s e n s o r y pain repor t . Thus, the p lacebo d i rec t i ve that a c ream w i l l reduce pain should m a i n l y 35 a f f e c t the pain unp leasantness . Nonverba l express ion m a y be less suscept ib le to the b iases of soc ia l demands and w a s not expec ted t o change as subs tan t ia l l y as verbal repor t , espec ia l l y as subjects w e r e not aware that their fac ia l express ions were be ing measured . In p s y c h o p h y s i o l o g i c a l research it has been argued that verba l repor t o f p h y s i o l o g i c a l a c t i v i t y represents an " index o f a repor tab le s ta te that may or m a y no t be re la ted h igh ly t o the ta rge ted phys io log i ca l p r o c e s s " (Cac ioppo, M a r s h a l l - G o o d e l l , and Gormezano , 1983, p. 684). Others have no ted a desynch rony b e t w e e n pain behav iour and s e l f - r e p o r t (Fordyce et a l . , 1984; Hyde, 1986). Thus, it w a s not clear whe ther the phys io log i ca l pain response w o u l d be c o m m u n i c a t e d in a s im i la r manner across verbal and nonverba l measures . H y p o t h e s i z e d E f f e c t s o f P lacebo ]n the Present S tudy The i nves t i ga t i on began by d e t e r m i n i n g basel ine p lacebo e f f e c t s to s h o c k - i n d u c e d pain . This w a s f o l l o w e d by e f f o r t s to c o n d i t i o n a p lacebo e f f e c t e i ther positively (shock in tens i t y decreased w i t h p lacebo) , or negatively (shock in tens i t y increased w i t h p lacebo) , or no t at all ( con t ro l g roup) , based upon the ear l ier w o r k o f th is t ype by Voudour i s et al . (1985). A re turn to basel ine p r o v i d e d a con t ras t w i t h the in i t ia l basel ine assessmen t . S h o c k - i n d u c e d pain w a s chosen f o r an analogue representa t ion o f c l in ica l pain par t l y because shock re l i ab ly induces anx ie ty thereby r e s e m b l i n g the internal s ta te o f pain pa t ien ts (Sternbach, 1974). In a d d i t i o n , shock can be var ied in i n t e n s i t y , repeated over severa l t r ia ls w i t h o u t hab i t ua t i on , and has been s a f e l y admin i s te red in pr io r research (Tursky, 1974). 36 (1) . Pa in - re la ted A U s pred ic ted f r o m pr ior research w e r e 4 , 6 / 7 , 10, 1 1 , 12, 2 5 / 2 6 / 2 7 , and 4 3 / 4 5 . These were expected to occur under pa in fu l e lec t r i c shock and to pred ic t shock in tens i t y and s e l f - r e p o r t e d pa in . (2) . P lacebo t r ia ls were expected t o e l i c i t l ower verbal and nonverba l express ions o f pain c o m p a r e d to n o - p l a c e b o t r ia ls in all groups dur ing the basel ine phase and in the con t ro l g roup in bo th basel ine and r e t u r n - t o - b a s e l i n e phases. (3) . Bonica (1979) has sugges ted that l o w t o modera te pain o n l y w o u l d be a f f e c t e d by p lacebo , the re fo re shock i n tens i t y was expec ted to in teract w i t h p l a c e b o / n o - p l a c e b o t r ia ls . (4) . A f t e r the c o n d i t i o n i n g t r i a l s , a decrease in pain measures w a s pred ic ted f o r sub jec ts w h o underwent p o s i t i v e c o n d i t i o n i n g . No change w a s pred ic ted f o r the con t ro l g roup. A n increase in pain express ion w a s pred ic ted f o r the negat ive c o n d i t i o n i n g g roup . The p red ic ted changes w e r e assessed by examin ing the p re t rea tment and p o s t t r e a t m e n t scores w h i c h cons is ted o f averaged s e l f - r e p o r t pain ra t ings and fac ia l express ions f o r each o f the three shock in tens i t i es . (5) . The Unpleasantness Scale w a s expec ted t o s h o w the greatest e f f e c t , the Sensory Scale an in te rmed ia te e f f e c t , and fac ia l a c t i v i t y the least e f f e c t . Whi le the d i f f e r e n t scales and fac ia l a c t i v i t y were not d i r e c t l y con t ras ted w i t h each o ther , there w a s an expec ta t ion that on l y the Unpleasantness Scale w o u l d demons t ra te a s ign i f i can t p lacebo e f f e c t . (6) . No sex d i f f e r e n c e s were p red ic ted because the range o f shock in tens i t ies admin i s te red w a s ind iv idua l ized to include the sub jec t 's o w n th resho ld th rough supra thresho ld in tens i t ies . 37 (7). A n x i e t y level w a s expec ted to co r re la te p o s i t i v e l y w i t h p lacebo e f f e c t . If the reason that p lacebos are more e f f e c t i v e in c l in ica l popu la t i ons than in l abo ra to ry vo lun teers is because the f o r m e r have more anx ie ty sur round ing their pain exper ience, then it shou ld f o l l o w that high perce ived anx ie ty in l abora to ry sub jec ts p red ic ts greater p lacebo response (Bonica, 1979). Further, anx ie ty shou ld have been reduced pr io r t o the p lacebo t r i a l s . 38 M e t h o d In the present s t u d y , the e f f e c t s o f a p lacebo c ream were examined using bo th verba l and nonverbal measures o f pa in . The f o l l o w i n g pages w i l l ou t l ine the exper imenta l des ign , m e t h o d o l o g y , and resu l ts . O v e r v i e w o f Design A n ascending ser ies o f shocks es tab l i shed each sub ject 's pain s e n s i t i v i t y range (PSR), d e f i n e d by W o l f f (1978) as the range b e t w e e n pain to le rance and pain th resho ld (expressed in m A m p s and de r i ved by sub t rac t ing the th resho ld shock in tens i t y level f r o m the to le rance in tens i t y leve l ) . Thresho ld w a s de f ined as the f i r s t s t imu lus ra ted as " u n c o m f o r t a b l e " on the Gracely et a l . (1978a) Unpleasantness Scale . To lerance w a s that level p r io r t o w h i c h the subject said t o s top the ascending ser ies . Three leve ls o f current i n tens i t y were se lec ted f o r basel ine t r i a l s . The th resho ld level served as the " l o w " leve l , t h resho ld + .25 PSR w a s " m e d i u m " , and th resho ld + .50 PSR w a s "h igh " (Note that the "h igh" level w a s h a l f w a y b e t w e e n the th resho ld and to le rance leve ls ) . This procedure c o m p l i e d w i t h Harr is and Rol lman 's (1983) sugges t ion o f us ing bo th t h r e s h o l d and to le rance measures in l abo ra to ry i n v e s t i g a t i o n s . A f t e r the ascending ser ies , all sub jec ts underwent a basel ine phase that en ta i led the de l i ve ry o f t w o ser ies o f nine shocks each (three each of l o w , m e d i u m , and high shocks in random order ) , f o r a t o ta l o f 18 shocks . One ser ies o f nine was de l i ve red w i t h p lacebo c ream and one ser ies was de l i ve red w i t h o u t c ream, counterba lanced t o c o n t r o l f o r order e f f e c t s . (See Table 2 f o r des ign o v e r v i e w . ) 39 Next , in the c o n d i t i o n i n g phase, 3 ser ies o f 9 r a n d o m shocks each w e r e de l i ve red . The f i r s t and th i rd ser ies were w i t h p lacebo c r e a m , the second ser ies w a s w i t h o u t p lacebo c r e a m . Sub jec ts w e r e r a n d o m l y ass igned t o one o f three groups. The random shocks g i ven with placebo cream w e r e su r rep t i t i ous l y decreased by 0.25 PSR f o r sub jec ts in Group I, the positive conditioning group. Shocks w i t h the p lacebo c ream were increased by 0.25 PSR f o r Group I I , the negative conditioning g roup . A n d shocks remained at their basel ine i n tens i t y levels f o r sub jec ts in the th i rd or control g roup. The f ina l r e t u r n - t o - b a s e l i n e phase w a s ident ica l t o the basel ine phase. 40 Table 2. Des ign O v e r v i e w . TIME LINE: Ascending series . . Baseline trials with and without placebo . . Conditioning trials with, without, then with placebo . . Return-to-base!ine trials with and without placebo. Trea tmen t Basel ine C o n d i t i o n i n g Return t o B.L. Group I . .with p lacebo t r ia ls L / M / H L /M/H- .25PSR L / M / H ..no p lacebo t r ia ls L / M / H L / M / H L / M / H Group 11 . .with p lacebo t r ia ls L / M / H L / M / H + .25PSR L / M / H ..no p lacebo t r ia ls L / M / H L / M / H L / M / H Group III . .with p lacebo t r ia ls L / M / H L / M / H L / M / H ..no p lacebo t r ia ls L / M / H L / M / H L / M / H ( " L / M / H " re fe rs to l o w / m e d i u m / h i g h s t imu lus in tens i ty . ) 41 Sub jec ts 30 f e m a l e and 30 male UBC student vo lun teers w e r e paid $9.00 f o r 90 m inu tes pa r t i c i pa t i on . They w e r e recru i ted by pos te r a d v e r t i s e m e n t s t o pa r t i c ipa te as sub jec ts in a s t u d y des igned t o inves t iga te senso ry p e r c e p t i o n . A te lephone cal l c o n v e y e d fur ther i n f o r m a t i o n regard ing the nature o f the s tudy and the shock s t imu lus . A b o u t o n e - h a l f o f the f e m a l e s con tac ted and o n e - t h i r d o f the males re fused t o pa r t i c i pa te . Appara tus and Mater ia ls Redux paste was used t o prepare the sk in f o r the shock e lec t rode . The concent r i c shock e lec t rode c o n s i s t e d of a p las t ic cas ing w h i c h housed an inner disc and sur rounding s ta in less s teel annulus. The inner d isc and outer annulus w e r e coa ted w i t h Redux paste and then c o v e r e d w i t h sponges soaked in sal ine and coa ted w i t h Redux paste . The lat ter p r o v i d e d con tac t w i t h the sk in . A Tensor bandage s t rapped the e lec t rode to the prepared f o r e a r m . This w a s in accordance w i t h s tandard procedures f o r the de l i ve ry o f c o n t r o l l e d , nox ious e lec t r ic s h o c k s , as deve loped by Tu rsky (1974) and as app l ied by Craig and his assoc ia tes (Craig & W e i s s , 1971 ; Craig & Prkach in , 1978; Patr ick , Craig, & Prkachin, 1986). V ideo tape equ ipment concea led behind a o n e - w a y m i r ro r inc luded the f o l l o w i n g : a Panasonic AG6300 VHS recorder , an RCA JD975WV 19- inch c o l o r m o n i t o r , and an RCA CC007 co lo r camera . T w o 1 2 - p o i n t ra t ing scales w e r e adapted fo r use as dependent measures (Gracely et al. , 1978, see Append ix A. ) . The Grace ly "Unp leasan tness" scale inc luded an added lower ra t ing o f "no d i s c o m f o r t " . The uppermos t desc r ip to r remained "exc ruc ia t ing" . The " S e n s o r y " scale 42 inc luded an added lower ra t ing o f "no s e n s a t i o n " and i ts uppermos t desc r ip to r remained "ex t reme ly in tense" . Thus, the scales c o n s i s t e d of 13 desc r ip to rs each. Subjects were requested t o es t ima te thei r anx ie ty based on a 0 - t o - 1 0 0 "anxiety t h e r m o m e t e r " at the f o l l o w i n g t i m e s ; b e f o r e the ascending ser ies , be fo re each of the t w o basel ine ser ies , and b e f o r e each o f the t w o r e t u r n - t o - b a s e l i n e ser ies . The " 0 " level w a s descr ibed as ca lm and the "100" level w a s desc r ibed as the m o s t anx ie ty one cou ld imagine exper ienc ing . The p lacebo analgesic c ream c o n s i s t e d o f Glaxal Base, an inert w h i t e cream w i t h a fa in t chemica l odor wh ich is c o m m o n l y used as a base cream f o r med ica ted p repara t ions . It w a s app l ied f r o m a sma l l tube . Procedure The ent i re procedure t o o k about 90 minu tes t o c o m p l e t e . The subject w a s escor ted to a labora to ry r o o m and seated at a tab le fac ing a o n e - w a y m i r ro r . The subject w a s t o l d that the s tudy w a s suppor ted by a pharmaceut ica l supply c o m p a n y to tes t a n e w analgesic c ream (designed to act as a local anaes the t ic ) using r e l a t i v e l y m i l d e lec t r ic shocks . The p rocedure , expected du ra t i on , and rate o f pay were exp la ined . The sub jec t w a s i n f o r m e d o f the r ight to w i t h d r a w or to re fuse to answer any ques t i ons , and c o n f i d e n t i a l i t y was assured. A consent f o r m ou t l i n ing th is i n f o r m a t i o n w a s s igned. V i d e o t a p i n g w a s no t d i s c l o s e d unt i l the deb r ie f i ng at wh ich t i m e subjects w e r e o f f e r e d the o p t i o n o f d e s t r o y i n g the v i d e o t a p e . This procedure reduced the l i ke l i hood that sub jec ts w o u l d modu la te thei r fac ia l a c t i v i t y as a resul t o f be ing obse rved (Kleck, Vaughan, C a r t w r i g h t - S m i t h , Vaughan, C o l b y , and Lanzet ta , 1976) and had been used 43 s u c c e s s f u l l y in a pr ior s tudy (Craske and Cra ig , 1984). T w o sub jec ts op ted t o have the tape erased. Five sub jec ts d ropped out due to the avers ive nature o f the s t u d y ; three were t e r m i n a t e d by the exper imen te r due to the fac t that the i r pain s e n s i v i t y ranges w e r e t o o c o n s t r i c t e d at the l o w end o f the ra t ing scale to a l l o w fo r any man ipu la t ion o f shock in tens i t y leve l . The nature o f the p lacebo cream w a s not d i s c l o s e d unt i l deb r i e f i ng . Sub jec ts s igned a medica l screening f o r m wh ich adv ised peop le not t o take part if t hey had a h i s t o r y o f heart c o n d i t i o n s , h y p e r t e n s i o n , a l lerg ic sk in responses , w e r e cur ren t ly tak ing m e d i c a t i o n , or if t hey had any other reason w h y they should not accept the shocks . (Forms are inc luded in A p p e n d i c e s C and D.) The ra t ing scales w e r e s h o w n t o the subject and then he/she w a s ins t ruc ted t o l i s ten t o the t a p e - r e c o r d e d ins t ruc t ions regard ing the use o f the sca les . The sub ject 's nondominan t f o r e a r m w a s prepared w i t h Redux paste and the e lec t rode was held in place w i t h a Tensor bandage. A s c e n d i n g Ser ies . A n ascending ser ies o f 5 0 0 - m i l l i s e c o n d shocks p rog ressed upward f r o m zero in 0.5 m A s teps w i t h in tershock in terva ls ranging b e t w e e n 10 and 20 s e c o n d s ; th is es tab l ished the sub jec t 's range o f pain s e n s i t i v i t y . The subject was admin i s te red a set o f w r i t t e n ins t ruc t ions and the t a p e - r e c o r d i n g as f o l l o w s : Shocks w i l l be admin i s te red in increasing in tens i t i es , s ta r t ing w i t h levels so l o w that y o u may not fee l any th ing . A s l ight "buzz" sound w i l l s ignal the de l i ve ry o f each shock so that at the l o w e s t leve ls y o u w i l l k n o w it has taken place. A f t e r the shock , you are t o rate it using each o f the t w o scales that y o u see on the s tand in f r o n t o f y o u . The Sensory Scale on the le f t represents the pain in tens i t y or h o w s t rong the pain f e e l s . The Unpleasantness Scale on the r ight represents h o w unpleasant or d is tu rb ing the pain is f o r y o u . The d i s t i n c t i o n b e t w e e n these t w o aspects o f pain might be 44 made clearer if y o u th ink o f l i s ten ing t o a sound , such as a rad io . A s the v o l u m e o f the sound increases, I can ask y o u h o w loud it sounds or h o w unpleasant it is t o hear i t . The in tens i t y o f pain is l ike l oudness ; the unpleasantness of pain depends not on l y on in tens i t y but a lso on other f a c t o r s w h i c h may a f f e c t y o u . Please t r y t o judge these t w o aspects o f pain independent l y . A f t e r each shock , choose a w o r d f r o m the S e n s o r y Scale and then push the bu t ton on the panel w i t h the c o r r e s p o n d i n g le t ter f r o m A to M. Next, choose a w o r d f r o m the Unpleasantness Scale and push the b u t t o n on the panel w i t h the co r respond ing let ter . Shocks w i l l g radual ly increase in in tens i t y to a level b e y o n d wh ich y o u are not prepared to accept any fu r ther increases. A t that t i m e te l l the exper imen te r t o " s t o p " and no more shocks w i l l be g i v e n . A t no t i m e w i l l y o u be requ i red t o exper ience any greater shocks than y o u are prepared t o accept . Then we ' l l take a shor t break. In a d d i t i o n , I shal l ask y o u t o rate your anx ie ty level at va r i ous t i m e s t h r o u g h - o u t the exper iment . To rate your anx ie ty l e v e l , use a number f r o m 0 t o 100 on the anx ie ty t h e r m o m e t e r in f r o n t o f y o u . " 0 " w o u l d mean you ' re c a l m , "100" w o u l d mean the m o s t anx ie ty y o u can imagine exper ienc ing . What 's you r anx ie ty level n o w us ing th is scale? Do y o u have any quest ions? The d i s t i n c t i o n made b e t w e e n the s e n s o r y and unp leasantness aspects o f pain was taken f r o m Price et al . (1983). The exper imenter exp la ined that she w o u l d be in a r o o m on the other s ide o f the o n e - w a y mi r ro r and that they cou ld c o m m u n i c a t e th rough an in te rcom s y s t e m . The exper imenter then le f t the r o o m , es tab l i shed in te rcom c o m m m u n i c a t i o n by say ing "we ' l l beg in n o w " , and a d m i n i s t e r e d the f i r s t ser ies o f shocks . The exper imenter opera ted the v ideo equ ipment and shock generator f r o m the adjacent r o o m behind the o n e - w a y mi r ro r . V ideo tap ing cont inued th roughout al l shock a d m i n i s t r a t i o n s . The subject chose a desc r ip to r f r o m each o f the t w o ra t ing scales l i s ted on a panel . But tons on the panel were le t tered f r o m A to M ; these c o r r e s p o n d e d to the 13 d e s c r i p t o r s fo r each scale and the subject s i m p l y pushed the bu t ton co r respond ing t o the desc r ip to r . (Let ters were used t o a v o i d a choice 45 based upon numer ica l rank rather than w o r d meaning.) A f t e r the subject said " s t o p " , he /she w a s ins t ruc ted t o take a break f o r a b r ie f t i m e wh i le the exper imenter ca lcu la ted appropr ia te l o w , m e d i u m , and high values fo r the next phase o f the exper iment . Base l ine. Next , t o es tab l i sh base l ine r e a c t i v i t y t o the p lacebo c ream, t w o random ser ies o f 9 shocks each were a d m i n i s t e r e d , one w i t h and one w i t h o u t the p lacebo c r e a m . Each random ser ies cons i s ted o f three shocks at each o f the three leve ls ( l o w , m e d i u m , and high). Half o f the sub jec ts w e r e r a n d o m l y ass igned t o rece ive the random ser ies w i t h the p lacebo c ream f i r s t , the other half rece ived the ser ies w i t h o u t the p lacebo cream f i r s t , t o con t ro l f o r poss ib le order e f f e c t s . A l l groups w e r e balanced f o r sex. A n x i e t y rat ings were g iven b e f o r e th is basel ine phase, then the t w o sets o f 9 random shocks each p roceeded w i t h the subject ra t ing the shocks as b e f o r e using the Sensory and Unpleasantness Sca les . Sub jec ts w e r e t o l d The next ser ies o f shocks w i l l cons i s t o f a to ta l o f 9 shocks at va r ious i n tens i t y l eve ls , al l at l o w e r leve ls than the level at w h i c h y o u said to s t o p . You are to rate each o f these in the same manner as the f i r s t ser ies . On the anx ie ty t h e r m o m e t e r , wha t ' s your anx ie ty level now? Ins t ruc t ions regard ing the p lacebo cream were g iven when the cream w a s app l ied . Sub jec ts w e r e t o l d Next is a ser ies o f s t i m u l i w i t h th is analgesic c ream. We are engaged in a s tudy suppor ted by a pharmaceut ica l supp ly c o m p a n y to tes t th is n e w analgesic c r e a m . It is des igned to act as a local anaesthet ic . Recent t es t s have s h o w n it t o be e f f e c t i v e and q u i c k - a c t i n g . It takes about 2 minu tes to take e f f e c t . 46 A m e d i c a t i o n check l is t w a s c o m p l e t e d a f te r the app l i ca t ion o f the cream to fu r ther c o n v i n c e the sub jec ts that it w a s a po ten t p repara t ion . (See A p p e n d i x E.) A break occur red b e t w e e n the t w o random ser ies in order t o remove or add the p lacebo c r e a m , f o l l o w e d by a t w o - m i n u t e w a i t i n g per iod to a l l o w the c ream to " take e f f e c t " or t o "wear o f f " . The cream w a s r e m o v e d w i t h c o t t o n soaked in an a lcoho l s o l u t i o n . Subsequen t l y , be tween base l ine and c o n d i t i o n i n g , sub jec ts t o o k a 5 - m i n u t e break. C o n d i t i o n i n g . Sub jec ts w e r e r a n d o m l y ass igned t o groups w i t h i n the r e s t r i c t i o n o f ba lancing f o r sex. Sub jec ts were t o l d that they w o u l d rece ive m o r e sets o f r andom shocks as b e f o r e . These began w i t h a set w i t h p lacebo c ream, f o l l o w e d by a set w i t h o u t c r e a m , then a set w i t h c r e a m . Both ser ies w i t h c ream enta i led the c o n d i t i o n i n g man ipu la t ion in w h i c h shock in tens i t ies w e r e man ipu la ted as f o l l o w s : 1. f o r sub jec ts in the positive conditioning g roup , each o f the three i n t e n s i t y levels were decreased by .25 PSR; 2. in the negative conditioning g roup , i n tens i t y levels were increased by .25 PSR; 3. control sub jec ts rece ived the same in tens i t ies as in the basel ine phase. The second random ser ies , w h i c h occur red be tween the t w o sets o f c o n d i t i o n i n g t r i a l s , c o n s i s t e d o f 9 shocks at basel ine leve ls w i t h o u t p lacebo c ream t o serve as a basis o f c o m p a r i s o n to the man ipu la ted in tens i ty se r ies . A g a i n , sub jec ts ra ted anx ie ty levels be fo re each ser ies and they gave S e n s o r y and Unpleasantness ra t ings f o r each shock. However , the data 47 f r o m these rat ings were not ana lyzed. A 5 - m i n u t e break occur red pr io r to the f ina l phase. Return to Basel ine. T w o random ser ies o f 9 shocks each w e r e a d m i n i s t e r e d , one w i t h and one w i t h o u t the p lacebo c ream in the same order as in the f i r s t basel ine phase. Sub jec ts gave their anx ie ty e s t i m a t e s b e f o r e each ser ies , and rated the shocks as b e f o r e . A p o s t - e x p e r i m e n t a l quest ionna i re examined sub jec ts ' p r io r exper ience w i t h ana lges ics and p r o v i d e d the o p p o r t u n i t y to descr ibe f o r m u l a t e d hypo theses or susp ic ions about the nature o f the s tudy . F inal ly sub jec ts were f u l l y debr ie fed regard ing the t rue purpose and fund ing f o r the exper imen t . They were g iven the o p t i o n o f having their v i deo tape erased. T w o sub jec ts in th is i nves t i ga t i on requested erasure o f the tape. Subjec ts were reques ted to re f ra in f r o m d iscuss ing the s tudy w i t h anyone unt i l the s tudy w a s c o m p l e t e d in an a t t e m p t t o reduce the l i ke l ihood that po ten t ia l sub jec ts w o u l d k n o w the exper imenta l hypo theses pr ior t o p a r t i c i p a t i o n . Exper imenta l resul ts were made avai lable at their request . (Forms are in A p p e n d i c e s F and G.) Facial A c t i o n Coding A data coder , w h o had passed p r o f i c i e n c y tes ts as a FACS coder , sco red the fac ia l express ions (Ekman & Fr iesen, 1978a). She w a s b l ind to the group m e m b e r s h i p o f s t imu lus sub jec ts and t o current in tens i t ies that were be ing de l i ve red . This procedure has recen t l y been used and resu l ted in acceptab le i n t e r - c o d e r re l iab i l i t i es o f 0.85 fo r agreement o f the occur rence o f p a i n - r e l a t e d AUs and 0.71 f o r agreement o f all A U s scored (Craig & Pat r ick , 1985). S i m i l a r l y , Patr ick et a l . (1986) ca lcu la ted t w o 48 in te rcoder re l iab i l i t i es as f o l l o w s : 1) the ra t io o f t o ta l number o f agreements to t o ta l number o f A U s scored w a s .74, and 2) the ra t io f o r 13 p a i n - r e l a t e d A U s w a s .84. In a d d i t i o n , Hyde (1986) repo r ted in tercoder re l i ab i l i t y (based upon percent ag reemen t ) equal to .76. Sub jec ts ' fac ia l reac t ions to the r a n d o m ser ies shocks in the basel ine and r e t u r n - t o - b a s e l i n e phases were scored using FACS (Ekman & Fr iesen, 1978b). For 2 /3 o f the random ser ies shocks , a 3 - s e c o n d segment o f v i deo tape was scored c o n s i s t i n g o f the 0 .5 -second pe r iod preced ing the shock , the 0 .5 -second shock i t s e l f , and the 2 - s e c o n d pe r iod f o l l o w i n g the shock. This in terva l captures the apex o f the fac ia l m o v e m e n t s and ends pr ior to the onse t o f m o s t ext raneous m o v e m e n t s (in accordance w i t h p rocedures f o l l o w e d by Pat r ick , Cra ig , & Prkach in , 1986). In a d d i t i o n , a v ideo tape segmen t , captur ing a neutral express ion o f the subject w h i l e awa i t i ng the f i r s t random ser ies o f s h o c k s , served as a basel ine against w h i c h to compare fac ia l reac t ions to the pa in fu l shocks . A to ta l o f 24 3 - s e c o n d s e g m e n t s w e r e coded f o r each subject in the basel ine phases (12 p r e - and 12 p o s t - t r e a t m e n t ) . On ly 2 /3 o f the A U s were coded in order t o reduce the t i m e - c o n s u m i n g task o f cod ing (app rox ima te l y 90 m inu tes per sub jec t ) . The coded s e g m e n t s cons i s ted o f the f i r s t and th i rd shock at each i n tens i t y level (out o f each basel ine ser ies o f nine shocks) . Thus , in each basel ine c o n d i t i o n f o r each sub jec t , there w e r e 2 l o w , 2 m e d i u m , and 2 high in tens i t y shock t r ia l s coded in each o f the p lacebo and n o - p l a c e b o c o n d i t i o n s . AUs w e r e aggregated f o r each pair . 49 Results The p resen ta t ion o f resu l ts beg ins by exp la in ing h o w fac ia l express ion w a s t rans la ted in to a un id imens iona l number. Next , the analyses cover A N O V A s o f the Unpleasantness and Sensory Scales and fac ia l a c t i v i t y . The re la t ionsh ip b e t w e e n fac ia l a c t i v i t y and s e l f - r e p o r t is examined . F ina l ly , a d i scuss ion o f h o w s e l f - r e p o r t e d anx ie ty p red ic ted p lacebo response conc ludes the resu l ts s e c t i o n . De r i va t i on o f Facial A c t i v i t y Score To e l im ina te c o n s i d e r a t i o n o f rare ly occur r ing A U s , the t o p 25% o f al l A U s w h i c h occur red at least once across all o b s e r v a t i o n s f o r all sub jec ts w e r e reta ined f o r subsequent ana lyses . These occur red an average o f at least 1.15 t imes per sub jec t and cons t i t u ted the f o l l o w i n g nine A U s in descend ing order o f f r e q u e n c y : 45 , 25, 12, 04, 0 1 , 02, 06, 14, and 23. (See Table 3). To es tab l ish a quan t i ta t i ve index o f the fac ia l response to e lec t r ic shocks , a pr inc ip le c o m p o n e n t s ana lys is (PCA) w a s conduc ted on the co r re la t i on matr ix o f the f r e q u e n t l y occur r ing A U s . This p e r m i t t e d ana lyses o f a c o m p o s i t e score f o r fac ia l a c t i v i t y in con t ras t to analyses that w o u l d have focused on the separate e q u a l l y - w e i g h t e d 9 fac ia l A U s . PCA ex t rac ts a major f a c t o r t o account f o r the largest amount o f var iance b e f o r e ex t rac t ing subsequent (o r thogona l ) f a c t o r s . (The Scree tes t sugges ted that 2 or 3 f a c t o r s shou ld have been r e t a i n e d ; the K a i s e r - G u t t m a n rule sugges ted 3 f ac to rs . ) The 3 - f a c t o r s o l u t i o n y i e l d e d the m o s t in te rpre tab le loadings a f ter va r imax (o r thogona l ) r o t a t i o n . (22% o f the to ta l var iance w a s accounted f o r by the f i r s t f a c t o r ; 60% o f the var iance w a s accounted f o r by all th ree fac to rs . ) 50 There w a s a general co r respondence be tween the A U s that loaded m o s t heav i l y on th is f i r s t p r inc ip le c o m p o n e n t and A U s f o u n d to be act ive in earl ier s tud ies of acute pain (Craig & Pat r ick , 1985; Patr ick et al., 1986; Hyde, 1986). The f a c t o r score c o e f f i c i e n t s fo r the f i r s t p r inc ip le c o m p o n e n t de r i ved f r o m this s o l u t i o n w e r e used to w e i g h t the 9 f r equen t l y occur r ing A U s f o r ind iv idual sub jec ts in each o f the exper imenta l c o n d i t i o n s . A w e i g h t e d sum o f the 9 AUs f o r m e d the measure of fac ia l a c t i v i t y score f o r each o f the exper imenta l c o n d i t i o n s . These w e i g h t s are l i s ted in Table 4. 51 Table 3. A c t i o n Un i ts (AU) Remain ing A f t e r A p p l i c a t i o n o f Exc lus ion Cr i ter ia and Mean Frequency o f Their Occurrence A U DESCRIPTOR FREQUENCY 1 * Inner b r o w raise 1.9 2 * Outer b r o w raise 1.8 4 * B r o w lowerer 3.2 6* Cheek raiser 1.3 12* Lip corner pull 3.4 14 D imp le r 1.2 23 Lip t igh t 1.2 2 5 * Lips part 4.1 4 5 * Bl ink 20.0 •Cons is ten t w i t h Craig & Patr ick 's (1985), and /o r Hyde's (1986), and /o r Patr ick et al.'s (1986) f i n d i n g s 52 Table 4. We igh ts Used t o Der ive the Facial A c t i v i t y Score , L is ted in Descend ing Order o f Numer ica l Magn i tude A U WEIGHT DESCRIPTOR 6 .464148 Cheek raiser 4 .336734 B r o w lowerer 12 .332111 Lip corner pull 25 .205929 Lips part 45 .188334 Bl ink 14 - .028926 D imp le r 23 - .041333 Lip t igh t 1 - .065023 Inner b r o w raise 2 - .075434 Outer b r o w raise 53 I n t r o d u c t i o n t o Ana lyses The average shock level t o le ra ted w a s 8.8 m A ( ± 3 . 6 ) ; the average th resho ld level (rated as u n c o m f o r t a b l e ) w a s 4.9 m A ( ± 2 . 6 ) . These leve ls co r responded c l o s e l y t o those repor ted by Tursky and O'Connel l (1972): to le rance = 9.0 m A and u n c o m f o r t a b l e = 4.9 m A . The d i f f e r e n c e b e t w e e n to le rance and th resho ld c o n s t i t u t e d the pain s e n s i t i v i t y range (PSR), ca lcu la ted ind iv idua l l y f r o m each sub jec t ' s to le rance and th resho ld leve l . The average l o w in tens i t y level w a s 4.8; m e d i u m was l o w + .25 PSR = 5.8; and high was m e d i u m + .25 PSR = 6.8. These levels w e r e fur ther man ipu la ted by sub t rac t ing or adding .25 PSR f o r sub jec ts in the' p o s i t i v e or negat ive c o n d i t i o n i n g g roups , r e s p e c t i v e l y . 63% o f sub jec ts chose one or m o r e i tems f r o m the m e d i c a t i o n s ide e f f e c t s check l i s t ; those m o s t o f t e n endorsed were c o l d n e s s , w a r m t h , t i n g l i n g , and numbness . Thus, many o f the subjects appeared t o be l ieve that the cream was caus ing some a l tered s e n s a t i o n . Separate 5 - w a y repeated measures A N O V A s were conduc ted fo r the fac ia l a c t i v i t y score and fo r each o f the t w o s e l f - r e p o r t ra t ing scales (Unpleasantness and Sensory ) . The f i r s t t w o f a c t o r s represented the b e t w e e n - g r o u p f a c t o r s o f c o n d i t i o n i n g t r e a t m e n t and sex. The rema in ing f a c t o r s were the repeated measures p r e - / p o s t - t r e a t m e n t , p l a c e b o / n o - p l a c e b o t r i a l s , and shock in tens i t y ( l o w , m e d i u m , high). Because there w e r e o n l y three dependent measures , and one measure ( fac ia l a c t i v i t y ) be longed in a d i f f e r e n t doma in o f measurement (nonverba l pain express ion) , no M A N O V A w a s conduc ted and the a level o f s ign i f i cance w a s held at p < . 0 5 . ( A N O V A summary tab les are presented in Append ix H; cel l means and 54 s tandard dev ia t i ons f o r s ign i f i can t ma in e f f e c t s and in te rac t ions are p resented in Append ix I). Repeated measures ana lyses were based upon Greenhouse-Ge isse r ad justed dfs and p r o b a b i l i t y w h i c h resul ts in a more c o n s e r v a t i v e F tes t . Unp leasantness Scale Results Shock in tens i t y level w a s a ma in e f f e c t in the ana lys is o f the Unpleasantness Scale , F (2,108) = 55.84, /D<.001, w i t h all three levels ra ted s i g n i f i c a n t l y d i f f e r e n t when tes ted by the N e w m a n - K e u l s technique ( p < . 0 1 ) . Figure 1a shows an a lmos t l inear increase in the average ra t ings f r o m l o w th rough t o high in tens i t y . A second main e f f ec t ind ica ted that p lacebo t r ia ls w e r e rated as less unpleasant than n o - p l a c e b o t r i a l s , F (1,54) = 4.83, /?<.03. The p lacebo f a c t o r w a s fur ther i nvo l ved in a s i gn i f i can t in te rac t ion i n v o l v i n g g roup , F (2,54) = 3 .41, p < . 0 3 . The graph o f the in te rac t ion is po r t rayed in Figure 2. A n a l y s i s o f the s imple in te rac t ion e f f e c t s v e r i f i e d what is read i ly apparent f r o m the graph; the n o - p l a c e b o t r ia ls were rated as s i g n i f i c a n t l y more unpleasant than the p lacebo t r ia ls f o r Group III o n l y , F (1,54) = 11.58, p < . 0 0 1 . However , con t ra ry to wha t w o u l d be expec ted , there w a s no group e f f e c t w i t h i n the p lacebo c o n d i t i o n nor w i t h i n the n o - p l a c e b o c o n d i t i o n , F (2,54) = .12, p>.8 and F (2,54) = 1.6, p>.2, r e s p e c t i v e l y . figure 1 hteneity Factor on the Three Dependent Meesuree 5 5 3B-i ting 3 0 -to or 2 6 -<o to tne 2 0 -c (0 «-1 1 0 -6 -0 - -Figure 1a Low Medium High 76 70 66 «0 as 66 •I 6 0 H 46 4 0 36 30 H o 09 c <8 2 6 ^ 20 -| 16 o Figure 1b Low Medium High o.o-Low Medium High Figure 2 Group by Placebo/No-Placebo Interaction On the Unpleasantness Scale No Placebo 1 r 1 Group I Group II Group III 57 A t h r e e - w a y in te rac t ion i n v o l v e d g roup , p l a c e b o / n o - p l a c e b o t r ia l s , and i n t e n s i t y , F (4,108) = 2.77, p < . 0 5 (Greenhouse-Ge isser ad jus ted df and p r o b a b i l i t y ) . This w a s fu r ther examined by means o f s imp le in te rac t ion e f f e c t s ana lyses . Th is i n t e r a c t i o n , as represented by the bar graphs in Figure 3, is s im i la r t o the t w o - w a y in te rac t ion dep ic ted in Figure 2, except that i n tens i t y is p o r t r a y e d . A s may be seen f r o m Figure 3, Groups I and II are v e r y s im i la r ac ross p lacebo and n o - p l a c e b o t r ia ls at all levels o f i n tens i t y and there w e r e no s ign i f i can t in te rac t ions be tween the p l a c e b o / n o - p l a c e b o t r ia ls and in tens i t y f o r Group I or I I . A t Group III there w a s a s ign i f i can t p l a c e b o / n o - p l a c e b o by i n tens i t y i n te rac t i on , F (1.32,71.50) = 3.69, p < . 0 5 (Greenhouse-Ge isser p r o b a b i l i t y ) . The p lacebo t r ia l s were rated s i g n i f i c a n t l y lower than the n o - p l a c e b o t r ia l s at all three leve ls o f i n t e n s i t y ; at l o w : F (1,54) = 5.08, p < . 0 3 ; m e d i u m : F (1,54) = 7.70, / 7 < . 0 1 ; h igh : F (1,54) = 19.12, £ < . 0 0 0 1 . Cont rary to the h y p o t h e s e s , there was no s ign i f i can t in te rac t ion b e t w e e n p r e - / p o s t - c o n d i t i o n i n g by p lacebo t r ia ls by c o n d i t i o n i n g g roup . Never the less , sub jec ts re l iab ly rated p lacebo t r ia ls as less unpleasant than the n o - p l a c e b o t r i a l s . When analyzed fur ther , th is e f f e c t was not s i gn i f i can t in e i ther o f the exper imenta l g roups but w a s h igh ly s ign i f i can t in the con t ro l group in wh ich sub jec ts w e r e not exposed to p o s i t i v e or negat ive c o n d i t i o n i n g t r i a l s . 5 8 Figure 3 Group by Placebo/No-Placebo by Intensity Interaction On the Unpleasantness Scale 4 0 - 1 3 5 -3 0 -O) c ^ 2 5 -Ql V) CO CD £ 2 0 -c o 59 Sensory Scale Results I n tens i t y w a s again a s ign i f i can t main e f f e c t , F (2,108) = 74.94, p < . 0 0 1 , w i t h all three leve ls o f i n tens i t y ra ted s i g n i f i c a n t l y d i f f e r e n t as t es ted by the N e w m a n - K e u l s procedure ( p < . 0 1 ) . Figure 1b dep ic ts the a l m o s t l inear increase f r o m l o w in tens i t y to h igh. There w a s a s ign i f i can t t w o - w a y in te rac t ion i n v o l v i n g group and p l a c e b o / n o - p l a c e b o t r i a l s , F (2,54) = 3.46, /O<.04. (See Figure 4). Further ana lys is o f s i m p l e in te rac t ion e f f e c t s y i e l d e d resu l ts s im i la r t o those o f the Unp leasantness Scale . The n o - p l a c e b o t r ia ls w e r e rated as s i g n i f i c a n t l y more intense than the p lacebo t r ia ls f o r Group III o n l y , F (1,54) = 9.8, p < . 0 0 3 . There w a s no group e f f e c t w i t h i n the p lacebo c o n d i t i o n nor w i t h i n the n o - p l a c e b o c o n d i t i o n , F (2,54) = .33, p > . 7 and F (2,54) = 1.68, p > . 2 , r e s p e c t i v e l y . The a d d i t i o n o f the in tens i t y f a c t o r expanded the above in te rac t ion to a t h r e e - w a y in te rac t ion i n v o l v i n g g roup , p l a c e b o / n o - p l a c e b o t r i a l s , and i n t e n s i t y , F (2,108) = 2.64, p < . 0 5 (Greenhouse-Ge isser p r o b a b i l i t y ) . This resul t is graphed in Figure 5 wh ich is s im i la r to that o f the Unpleasantness Scale resul ts dep ic ted in Figure 3. A g a i n , there w e r e no s ign i f i can t in te rac t ions b e t w e e n the p l a c e b o / n o - p l a c e b o t r ia ls and in tens i t y f o r Group I or I I . On ly the p l a c e b o / n o - p l a c e b o con t ras ts in Group III we re s i g n i f i c a n t , and these w e r e f o r all three in tens i t y l eve l s , l o w : F (1,54) = 5.37, p < . 0 2 ; m e d i u m : F (1,54) = 4.74, /?< .03 ; h igh : F (1,54) = 17.81, p < . 0 0 0 1 . W i t h i n the p lacebo and n o - p l a c e b o c o n d i t i o n s , there w e r e no s ign i f i can t in te rac t ions b e t w e e n group and any one i n tens i t y leve l . Figure 4 Group by Placebo/No-Placebo Interaction On the Sensory Scale Placebo 1 1 1 — — Group I Group II Group III 61 Figure 5 Group by Placebo/No-Placebo by Intensity Interaction On the Sensory Scale 8 0 - . 7 0 -6 0 -O) 5 0 -62 F ina l ly , there w a s a s ign i f i can t f o u r - w a y in te rac t ion i n v o l v i n g g roup , sex, p r e - / p o s t - t r e a t m e n t , and in tens i t y l eve l , F (4,108) = 3.94, p < . 0 1 (Greenhouse-Ge isser p r o b a b i l i t y ) . Note that p l a c e b o / n o - p l a c e b o w a s not i nvo l ved in th is i n te rac t ion . These resu l ts are s h o w n in Figure 6. S i m p l e s i m p l e i n te rac t ion e f f e c t s w e r e examined f i r s t l y f o r each group c o n d i t i o n . W i t h i n each group c o n d i t i o n , there w a s no s ign i f i can t i n te rac t ion b e t w e e n the rema in ing three f a c t o r s (of sex, p r e - / p o s t - t r e a t m e n t , and i n tens i t y ) . S i m i l a r l y , w i t h i n each sex c o n d i t i o n there w a s no s i g n i f i c a n t i n te rac t ion be tween the remain ing three f a c t o r s . A l s o , w i t h i n each i n tens i t y c o n d i t i o n there w a s no s ign i f i can t in te rac t ion b e t w e e n the rema in ing three f a c t o r s . H o w e v e r , w i t h i n the p o s t - t r e a t m e n t c o n d i t i o n (but not p r e - t r e a t m e n t ) there w a s a s ign i f i can t in te rac t ion b e t w e e n g roup , sex, and i n t e n s i t y , F (2.41,64.97) = 3.89, p<.02 (Greenhouse-Geisser p r o b a b i l i t y ) . Further ana lys is o f i n tens i t y w i t h i n the p o s t - t r e a t m e n t c o n d i t i o n ind ica ted that at no i n tens i t y level w a s there a s ign i f i can t group by sex e f f e c t . None the less , when each group w a s analyzed w i t h i n the p o s t - t r e a t m e n t c o n d i t i o n , one group held a s ign i f i can t i n te rac t ion be tween sex and i n t e n s i t y : Group I I I , F (1.20, 64.97) = 8.56, p < . 0 0 3 (Greenhouse-Ge isser p r o b a b i l i t y ) . U n f o r t u n a t e l y , no s t r a i g h t f o r w a r d exp lanat ion o f th is e f f e c t is poss ib le because at no in tens i t y level w a s there a s ign i f i can t sex d i f f e r e n c e . H o w e v e r , there was a marg ina l l y s ign i f i can t in te rac t ion b e t w e e n the l o w and m e d i u m in tens i t i es , F (1,54) = 4.49, p < . 0 4 ; a s ign i f i can t in te rac t ion b e t w e e n the m e d i u m and high in tens i t ies , F (1,54) = 6 .71, p < . 0 2 ; and a h igh ly s i g n i f i c a n t in te rac t ion b e t w e e n the l o w and high in tens i t i es , F (1,54) =20.97, p < . 0 0 0 1 . In other w o r d s , males gave higher ra t ings than f e m a l e s at the high in tens i t y shocks , 63 but gave l o w e r ra t ings than f e m a l e s at the m e d i u m and l o w in tens i t y shocks . These d i f f e rences w e r e not s ign i f i can t except w h e n con t ras ted w i t h other i n tens i t y levels in i n te rac t ions . 65 Facial A c t i v i t y Results There w a s a s ign i f i can t main e f f e c t f o r i n t e n s i t y , F (2,108) = 11.21, p < . 0 0 0 1 . N e w m a n - K e u l s tes ts ind ica ted that fac ia l a c t i v i t y at the l o w v. m e d i u m and l o w v. high in tens i t i es were s i g n i f i c a n t l y d i f f e r e n t (p< .01 ) , but the m e d i u m and high in tens i t ies produced no s ign i f i can t d i f f e r e n c e in fac ia l a c t i v i t y . The curve in Figure 1c shows th is e f f e c t c lea r l y ; the curve r ises f r o m l o w to m e d i u m and then leve ls out f r o m m e d i u m t o h igh . A t w o - w a y in te rac t ion i n v o l v i n g sex and p l a c e b o / n o - p l a c e b o t r ia ls w a s s i g n i f i c a n t , F (1,54) = 4.72, p< . 0 3 ; th is was fu r ther analyzed f o r s i m p l e i n te rac t ion e f f e c t s . W i t h i n ei ther o f the f e m a l e and male c o n d i t i o n s , no s ign i f i can t e f f e c t was ob ta ined f o r the p l a c e b o / n o - p l a c e b o c o m p a r i s o n . S i m i l a r l y , w i t h i n the p lacebo c o n d i t i o n , sex w a s not a s i g n i f i c a n t f a c t o r . However , w i t h i n the n o - p l a c e b o c o n d i t i o n , sex became a s ign i f i can t e f f e c t , F (1,54) = 3.92, p< . 0 5 , in that ma les ' f ac ia l a c t i v i t y w a s s i g n i f i c a n t l y greater than f e m a l e s ' . This can be seen in Figure 7. No other p a i r - w i s e con t ras ts were s ign i f i can t . This t w o - w a y in te rac t ion was fu r ther i nvo lved in a t h r e e - w a y i n t e r a c t i o n i n v o l v i n g group in add i t i on to sex and p l a c e b o / n o - p l a c e b o t r i a l s . W i t h i n the f e m a l e c o n d i t i o n there w a s no s ign i f i can t group by p l a c e b o / n o - p l a c e b o i n t e r a c t i o n ; h o w e v e r , w i t h i n the male c o n d i t i o n the group by p l a c e b o / n o - p l a c e b o in te rac t ion was s i g n i f i c a n t , F (2,54) = 3.24, p< . 0 5 . W i t h i n each m a l e - g r o u p c o n d i t i o n , the o n l y group to ho ld a s ign i f i can t d i f f e r e n c e b e t w e e n p lacebo and n o - p l a c e b o t r ia ls .was Group I I I , F (1,54) = 9.67, p< . 0 0 3 . A s can be seen f r o m the curves in Figure 8, f o r males in Group III the n o - p l a c e b o t r ia ls resu l ted in s i g n i f i c a n t l y m o r e fac ia l a c t i v i t y 66 than the p lacebo t r ia ls . The d i f f e r e n c e f o r f e m a l e s in Group III w a s not s i g n i f i c a n t . A f ina l t h r e e - w a y in te rac t ion i n v o l v e d the three repeated measures o f p r e - / p o s t - t r e a t m e n t , p l a c e b o / n o - p l a c e b o t r i a l s , and i n t e n s i t y l eve l . (See Figure 9). W i t h i n the p r e - t r e a t m e n t c o n d i t i o n , there w a s no s ign i f i can t in te rac t ion b e t w e e n the other t w o f a c t o r s . H o w e v e r , w i t h i n the p o s t - t r e a t m e n t c o n d i t i o n there w a s a s ign i f i can t i n te rac t i on b e t w e e n p l a c e b o / n o - p l a c e b o and i n tens i t y . Con t ras ts o f p lacebo v . n o - p l a c e b o t r ia l s at each in tens i t y level were conduc ted by means o f s imp le e f f e c t s ana lyses and resu l ted in no s ign i f i can t e f f e c t s . Further s imp le in te rac t ion e f f e c t s w e r e analyzed and y i e l d e d the f o l l o w i n g r e s u l t s : there w a s a s ign i f i can t in te rac t ion b e t w e e n l o w and m e d i u m , F (1,54) = 5.29, p<.03 and b e t w e e n l o w and h igh, F (1,54) = 9.37, p < . 0 0 3 , but no s ign i f i can t in te rac t ion b e t w e e n m e d i u m and h igh , F (1,54) = .577, p > . 0 5 . Thus, in the p o s t - t r e a t m e n t c o n d i t i o n , fac ia l a c t i v i t y w a s s im i la r at the m e d i u m and high in tens i t i es . It w a s s i g n i f i c a n t l y greater than at the l o w i n tens i t y leve l . 67 Figure 7 Sex by Placebo/No-Placebo Interaction On the Facial Act iv i ty Score 0.9-, 0.3H 0.2H o.H 0.0-Plecebo No Placebo Figure 8 Group by Sex by Placebo/No-Placebo Interaction On the Facial Activity Score Males 0.8-No Placebo A « Placebo Group I Group II Group III Females 0.2-o J 1 1 1 Group I Group II Group III Figure 9 Pre-/P08t-treatment by Placebo/No-Placebo by Intensity Interaction On the Facial Activity Score o < Pre-treatment x - " — • Placebo A Low X Medium O High No Placebo Post-treatment A Low X Medium D High Placebo No Placebo 70 Facial A c t i v i t y and S e l f - R e p o r t To assess the re la t ionsh ip b e t w e e n fac ia l a c t i v i t y and s e l f - r e p o r t , t w o s t e p w i s e mu l t ip le regress ions were c o n d u c t e d . The nine f r e q u e n t l y - o c c u r r i n g A U s served as p red ic to r var iab les f o r bo th analyses and 1) the Unpleasantness Scale s e l f - r e p o r t se rved as one c r i t e r i on va r iab le , and 2) the Sensory Scale s e l f - r e p o r t served as the second c r i t e r i o n va r iab le . The F p r o b a b i l i t y f o r inc lus ion and exc lus ion at each s tep w a s set at p < . 3 0 ; th is ensured that var iab les w o u l d be se lec ted f o r i n c l u s i o n / e x c l u s i o n in the mu l t i p le regress ion equat ion even though the resu l tan t F p r o b a b i l i t y was larger than the s tandard .05 leve l . A s can be seen f r o m the resul ts in Table 5, seven A U s entered the equat ion to account f o r 18% o f the var iance in the s e l f - r e p o r t e d Unpleasantness. In descend ing order o f i m p o r t a n c e , these were A U s 25, .12, 45, .14, 02, 04, and 23. The S e n s o r y Scale resul ts were s im i la r but w i t h s o m e d i f f e r e n t A U s inc luded in the equat ion and less var iance accounted f o r : 14%. The A U s w e r e 25, 45 , 12, 02, .14, and 06. (AUs that w e r e c o m m o n to bo th equat ions are under l ined.) Table 5 Mu l t i p le Regression Results f o r Facial A c t i v i t y and S e l f - r e p o r t Unpleasantness Scale: VARIABLE MULT R RSQ RSQ CH B BETA FfEqnV A U 25 .3186 .1015 .1015 3.652 .271 81.109 A U 12 .3656 .1337 .0322 2.619 .156 55.308 A U 45 .3945 .1556 .0219 .622 .117 43.982 A U 14 .4035 .1628 .0072 -2 .307 - .108 34.771 A U 2 .4376 .1711 .0083 1.852 .090 29.486 A U 4 .4194 .1759 .0047 1.171 .081 25.364 A U 23 .4211 .1773 .0014 -1 .082 - .040 21.919 * * * A l l F va lues were s i g n i f i c a n t , p < . 0 0 1 . Sensory Scale: VARIABLE MULT R RSQ RSQ CH B BETA FfEqn)' A U 25 .2622 .0688 .0688 6.482 .221 53.025 A U 45 .3309 .1095 .0408 1.812 .156 44.095 A U 12 .3594 .1291 .0196 4.754 .129 35.391 A U 2 .3686 .1359 .0067 4.400 .097 28.106 A U 14 .3776 .1426 .0067 -3 .968 - .084 23.745 A U 6 .3802 .1445 .0019 2.506 .049 20.074 * * * A l l F va lues were s i g n i f i c a n t , p < . 0 0 1 . 72 A n x i e t y and Placebo Placebo Reactors . T o der ive a p l a c e b o - r e a c t i o n s c o r e , the basel ine Unpleasantness Scale ra t ings were used as f o l l o w s ; each sub jec t 's averaged ra t ing f o r the n o - p l a c e b o t r ia ls w a s subt racted f r o m the p l a c e b o - t r i a l ra t ing . The basel ine ra t ings were used t o capture s u b j e c t s ' r e a c t i v i t y to on ly the verba l d i rec t i ons that the c ream w o u l d reduce p a i n f u l n e s s . Thus, no c o n d i t i o n i n g e f f e c t s c o n f o u n d e d th is p l a c e b o - r e a c t i o n sco re . A p o s i t i v e p l a c e b o - r e a c t i o n score meant that the subject rated p lacebo t r ia ls as less pa in fu l than n o - p l a c e b o t r ia ls (in the f i r s t basel ine phase o f the s tudy , pr ior to c o n d i t i o n i n g t r ia ls ) . 67% o f the subjects w e r e p o s i t i v e p lacebo reac to rs , 33% w e r e nega t i ve . The reac t ion scores ranged f r o m -20 .81 to 16.97 on the Unpleasantness Scale . The average p lacebo reac t i on w a s 1.631 (±6 .804) . Inc lud ing bo th the p r e - and p o s t - t r e a t m e n t da ta , the cel l means f o r p lacebo and n o - p l a c e b o t r ia ls w e r e 9.19 and 10.36, r e s p e c t i v e l y . The d i f f e rence (or p lacebo reac t i on ) using these numbers w a s 1.17 and th is resul ted in a main e f f e c t as d iscussed ear l ier . The average l o w , m e d i u m , and high in tens i t i es (on the Unpleasantness Scale w i t h base l ine data o n l y ) were 7.04, 9.74, and 13.61 y i e l d i n g a range o f 6.57. The basel ine p lacebo react ion o f 1.63 represents 25% of the l o w - t o - h i g h range and, t h e r e f o r e , may be cons ide red c l i n i ca l l y s ign i f i can t . A n x i e t y and Placebo React ion. A s tepw ise mu l t i p le regress ion w a s conduc ted t o examine the re la t ionsh ip b e t w e e n anx ie ty ra t ings (entered as p red ic to r va r iab les ) and sub jec t s ' reac t ions t o p lacebo (entered as the c r i te r ion var iab le ) . The s ign i f i cance level f o r inc lus ion and exc lus ion at each step w a s set at p < . 3 0 . 73 A n x i e t y ra t ings inc luded the s e l f - r e p o r t e d anx ie ty ( f r o m 0 to 100 on the anx ie ty t h e r m o m e t e r ) at the f o l l o w i n g f i v e t i m e s : b e f o r e the ascending shock ser ies , and b e f o r e each of the w i t h - p l a c e b o and n o - p l a c e b o t r ia ls bo th in the basel ine and r e t u r n - t o - b a s e l i n e phases. Three p red ic to r var iab les produced s i g n i f i c a n t resu l t s : anx ie ty ra t ings b e f o r e the ascending ser ies (anxiety 1), b e f o r e the basel ine t r ia ls w i t h p lacebo (anxiety 2), and b e f o r e the basel ine t r ia ls w i t h o u t p lacebo (anxiety 3) en tered the equat ion to account f o r 15% o f the var iance o f the p lacebo reac t ion (mul t ip le R = .38, R squared = .15; F = 3.16, p < . 0 3 ; see Table 6 f o r de ta i l s ) . The fi w e i g h t s r e f l e c t the re la t i ve impor tance o f the p red ic to r var iab les . It can be seen that anx ie ty measured b e f o r e the basel ine ser ies w i t h and w i t h o u t p lacebo (Anx ie ty 2 & 3) w e r e the m o s t impor tan t in the p red ic t i on equat ion . The anx ie ty ra t ings p r io r t o the p lacebo t r ia ls (Anx 2) was p o s i t i v e l y and m o s t heav i l y co r re la ted w i t h the p lacebo response , w h i l e the other t w o anx ie ty ra t ings were n e g a t i v e l y re la ted to p lacebo response . Table 6. Mu l t i p le Regress ion Results fo r A n x i e t y and Placebo React ion VARIABLE MULT R RSQ RSQ CH B BETA F(Eqn) A n x 1 .1940 .0376 .0376 - .093 - .293 2.229 A n x 2 .2894 .0837 .0461 .2192 .625 2.559 A n x 3 .3834 .1471 .0634 - .161 - .478 3.162* * P < . 0 3 75 D iscuss ion The resu l ts o f the FACS ana lyses are d iscussed f i r s t , f o l l o w e d by the s e l f - r e p o r t f i n d i n g s . The p lacebo e f f e c t s are summar ized w i t h i n the c o n d i t i o n i n g theo ry m o d e l . A f ina l sec t i on presents a s u m m a r y and an ana lys is o f the imp l i ca t i ons f o r fu ture research. Facial A c t i v i t y and Pain P a i n - r e l a t e d A U s pred ic ted f r o m pr io r research us ing a v a r i e t y o f sources o f pa in fu l exper ience were 4 , 6 / 7 , 10, 1 1 , J_2, 2 5 / 2 6 / 2 7 , and 43 /45 . Of these , f i v e (under l ined) were f o u n d to occur as a coherent pat tern dur ing pa in fu l shock ; in t o t a l , p a i n - r e l a t e d A U s f o u n d in the present s tudy w e r e 1, 2, 4, 6, 12, 14, 23, 25, and 45. A U s 1, 2, 14, and 23 were inverse ly re la ted to painfu l shock. Facial a c t i v i t y co r re la ted m o d e s t l y w i t h s e l f - r e p o r t w h i c h p rov ides convergent v a l i d i t y f o r fac ia l a c t i v i t y as a pain measure . Several A U s were f o u n d t o p red ic t Unpleasantness and Sensory Scale ra t ings . In descend ing order o f re la t ionsh ip to ra t ing scale va lues , A U s 25, .12. 45, .14, 2, 4, and 23 p red i c ted Unpleasantness ra t ings (mul t ip le Ft = .42), w h i l e A U s 25, 45, V2, 2, 1 4 , and 6 pred ic ted Sensory ra t ings (mu l t ip le R = .38). It is o f note that o f the f i r s t f i v e A U s c o m m o n to bo th reg ress ion equat ions (under l ined) , the f i r s t three w e r e f o u n d t o be re la ted t o pain in pr ior research: A U s 25, 12, and 45 ; these may be charac ter ized as an o p e n - m o u t h e d g r imace w i t h eye b l ink . Pr ior research i n v o l v i n g c o l d - p r e s s o r pain uncovered a s im i la r pat tern in a regress ion a n a l y s i s : A U s 2 6 / 2 7 , 6 / 7 , 12 , and 5 c o n t r i b u t e d to the regress ion equat ion (Craig and Patr ick , 1985). These A U s represent a w i d e r o p e n - m o u t h e d g r imace w i t h a squ in t ing o f the l ower eye l i d and ra is ing o f the upper 76 e y e l i d . Craig and Patr ick (1985) had argued that ra is ing o f the upper eye l id (AU 5) represen ted an e lement o f su rp r i se / s ta r t l e express ion . This fa i l ed to occur in the present s tudy p o s s i b l y due t o use o f a sound w h i c h s ignal led the shocks and w a s perce ived by sub jec ts to occur pr ior to pain sensa t ion . A d i f f e r e n t me thod o f de te rm in ing the m o s t impor tan t p a i n - r e l a t e d A U s e m p l o y e d the PCA. In descend ing order o f c o n t r i b u t i o n to the f i r s t p r inc ip le c o m p o n e n t , A U s w e r e 6, 4 , 12, 25, 45 , 14, 23, 1, and 2. It is in te res t ing t o no te that the lat ter four A U s were w e i g h t e d nega t i ve l y on the pain f a c t o r wh ich imp l ies that they are inverse ly re la ted t o pa in . They may be character ized as a t i g h t - l i p p e d sm i le w i t h ra ised e y e b r o w s wh ich p o s s i b l y s ignals s ta r t le , appeasement , or g ree t ing . Thus, A U s 6 .and 4 were more impor tan t that the three A U s l i s ted above (25, 12, and 45) as re la ted t o s e l f - r e p o r t indexes of pa in . These are m o v e m e n t s around the upper f a c e ; n a m e l y , cheek raiser (a m o v e m e n t under the eyes that w o u l d exaggerate c r o w s f e e t ) and eye b r o w lowere r . One cou ld specula te that these t w o m o v e m e n t s represent an invo lun ta ry response t o pain s ince they were o b s e r v e d to occur under pa in fu l shock but were less re la ted t o s e l f - r e p o r t . Lee (1985) has a lso sugges ted that there may be greater v o l u n t a r y c o n t r o l over l ower face ac t ions compared to upper face ac t ions (such as A U s 4 and 6). A l l t o l d , the c o n s t e l l a t i o n o f p a i n - r e l a t e d AUs f o u n d in the present i nves t i ga t i on over lapped g rea t l y w i t h those o f pr ior research and were m o d e r a t e l y re la ted to s e l f - r e p o r t . A fu r ther general o b s e r v a t i o n regard ing fac ia l a c t i v i t y w a s that it increased f r o m l o w to m e d i u m in tens i t y shock and then reached a ce i l i ng . 77 Thus , fac ia l a c t i v i t y may be o f l i m i t e d u t i l i t y as a pain measure s ince it cannot d i f f e r e n t i a t e c lear ly b e t w e e n m e d i u m t o high pain leve ls . Prior research has d e m o n s t r a t e d s im i la r d i f f i c u l t y in es tab l i sh ing s ign i f i can t d i f f e r e n c e s be tween m e d i u m and high in tens i t y (Patrick et al. , 1986). F ina l l y , the f i n d i n g that ma les w e r e more f a c i a l l y express ive than f e m a l e s in one c o n d i t i o n ( n o - p l a c e b o t r i a l s ) is c o n t r a r y to p rev ious research (i.e., Buck, M i l l e r , and Caul , 1974; Schwar tz , B r o w n , and A h e r n , 1980). Th is may be an a r t i f ac t in that males t o l e r a t e d higher shock in tens i t i es than f e m a l e s . Thresho ld and to le rance leve ls w e r e 4.13 ( ± 1 . 7 2 ) and 7.70 ( ± 2 . 8 3 ) f o r f e m a l e s , and 5.62 ( ± 3 . 0 8 ) and 9.88 ( ± 4 . 0 7 ) fo r ma les . Future s tud ies should inc lude sub jec ts o f b o t h sexes t o fu r ther inves t iga te sex d i f f e r e n c e s in fac ia l a c t i v i t y dur ing pa in . S e l f - R e p o r t and Pain Subjec ts c lear ly d i f f e r e n t i a t e d b e t w e e n the three shock in tens i t y leve ls as e x e m p l i f i e d by the h igh ly s i g n i f i c a n t main e f f e c t s f o r in tens i t y on s e l f - r e p o r t A N O V A s . Further, on bo th ra t ing scales there w a s an a lmos t l inear re la t ionsh ip f r o m l o w through high in tens i t y (see Figure 1) w h i c h sugges ts that 1) the ra t io scale va lues that co r respond t o the verbal d e s c r i p t o r s accurate ly re f l ec t a l inear re la t ionsh ip to pain in tens i t y and unp leasantness , and 2) the l o w , m e d i u m , and high shock leve ls captured a rep resen ta t i ve segment o f the pain s e n s i t i v i t y range. A d d e d suppor t f o r the second conc lus ion c o m e s f r o m the f o l l o w i n g o b s e r v a t i o n s : the mean l o w and high rat ings w e r e 6.9 and 12.9 on the Unpleasantness Scale on w h i c h the highest poss ib le ra t ing is 38.7; the mean l o w and high ra t ings w e r e 14.1 and 30.7 on the Sensory Scale on wh ich the highest poss ib le 78 ra t ing is 77.5. The "h igh" shock level w a s in i t ia l l y chosen t o represent the m i d w a y po in t be tween pain th resho ld and to le rance . The mean s e l f - r e p o r t ra t ings f o r high shocks w e r e just less than h a l f - w a y up the respec t i ve ra t ing scales and the re fo re c o r r e s p o n d e d rough ly to the m i d w a y po in t o f the pain s e n s i t i v i t y range. In c o n c l u s i o n , the in tens i t y man ipu la t i on w a s ve ry s a t i s f a c t o r y . P lacebo and Pain Placebo t r ia ls were genera l ly rated as less unpleasant and in tense than n o - p l a c e b o t r ia l s . There w a s a s ign i f i can t main e f f e c t f o r the Unpleasantness ra t ings , but not f o r the Sensory ra t ings nor f o r fac ia l a c t i v i t y . Prev ious researchers have no ted that p s y c h o l o g i c a l man ipu la t ions w o u l d p r i m a r i l y a f f e c t the u n p l e a s a n t n e s s / a f f e c t i v e ra t ings and not sensory ra t ings (Gracely et al . , 1979 & 1982; Pr ice, 1984; Price & Barber, 1987; Pr ice , Bar re l l , & Grace ly , 1980; Pr ice, Hark ins , & Baker, 1987), and so the present s tudy suppor ts such a c o n c l u s i o n . However , there were many more s i m i l a r i t i e s than d i f f e r e n c e s b e t w e e n the resul ts f o r the t w o s e l f - r e p o r t sca les . Pr ice, Harkins, Raf i i , and Price (1986) recen t l y examined sub jec t s ' response t o fen tany l in a s tudy i n v o l v i n g noc i cep t i ve tempera tu re s t i m u l i . They n o t e d that v isual analogue scale resu l ts f o r sensory and a f f e c t i v e m o d a l i t i e s were qui te s im i la r in exper imenta l pain sub jec ts whereas a f f e c t i v e pain was m o r e m o d i f i a b l e than sensory pain in l o w back pain sub jec ts . Th is f i n d i n g suggests that the f o r m e r conc lus ion that a f f e c t i v e pain is m o s t eas i ly a l tered by p s y c h o l o g i c a l man ipu la t ions (and even m e d i c a t i o n ) may be more p r o f o u n d w i t h chron ic pain pa t i en t s , ye t it app l ied to labora to ry sub jec ts in the present s tudy . 79 I n t e r e s t i n g l y , the Con t ro l Group sub jec ts d e m o n s t r a t e d the. greatest (and s i g n i f i c a n t ) p lacebo e f f e c t s ; ra t ings on bo th s e n s o r y and a f f e c t i v e d i s c o m f o r t scales s h o w e d a s ign i f i can t p lacebo e f f e c t across all three in tens i t y leve ls . M o r e o v e r , c o n t r o l - g r o u p males exh ib i ted s i g n i f i c a n t l y greater fac ia l a c t i v i t y in the n o - p l a c e b o t r ia ls than in the p lacebo t r ia ls . (This e f f e c t f a i l ed t o reach s ign i f i cance w i t h i n the f e m a l e c o n t r o l - g r o u p cond i t i on . ) Thus, the hypo thes i s that p o s i t i v e c o n d i t i o n i n g w o u l d a m p l i f y p lacebo e f f e c t s in c o m p a r i s o n t o negat ive c o n d i t i o n i n g and c o n t r o l p rocedures w a s not borne out . Ins tead, the man ipu la t ions seemed t o obscure a p lacebo response , w h i l e the con t ro l p rocedure seemed to e l i c i t a re l iab le p lacebo response. Fur thermore , the p lacebo e f f e c t w a s d e m o n s t r a t e d across all three i n tens i t y l eve l s , but it should be no ted that the high in tens i t y was lower than sub jec t s ' to le rance level and m a y c o r r e s p o n d more to a m e d i u m in tens i t y l eve l . Thus, the d e m o n s t r a t e d p lacebo e f f e c t w a s cons is ten t w i t h Bonica 's (1979) c o n c l u s i o n that p lacebos a f f e c t l o w t o modera te pain on ly . Ethical cons ide ra t i ons necess i ta ted the use o f s u b - t o l e r a n c e pain leve ls ; h o w e v e r , c l in ica l research migh t bet ter address th is issue in fu ture using intense but n a t u r a l l y - o c c u r r i n g pa in . Several poss ib le exp lanat ions exist t o account f o r the fa i lure o f the c o n d i t i o n i n g man ipu la t i ons . The m o s t o p t i m i s t i c m a y be that the present i n v e s t i g a t i o n was m e t h o d o l o g i c a l l y more r igourous than the Voudour is et al . (1985) s tudy . For example , the subjects w e r e less able t o c o m p l y w i t h the demands o f the s i tua t ion because they were ra t ing three levels o f shock in tens i t y p resented in a random order , rather than one level over and over . 80 The Voudour i s et al . (1985) s tudy a lso fa i led to con t ro l f o r order or p rac t ice e f f e c t s since all sub jec ts rece ived the n o - p l a c e b o t r ia l s f i r s t . A cont ras t w h i c h favours the Voudour is et a l . (1985) s tudy is that the present s t u d y had fewer c o n d i t i o n i n g t r ia ls wh ich may have y i e l d e d unstable or h igh ly var iab le data . Fur thermore , since c o n d i t i o n i n g sub jec ts rece ived a w i d e r array o f shock i n tens i t y leve ls , perhaps their j udgment ab i l i t y i m p r o v e d , thereby render ing the p lacebo cream inconsequent ia l . In the f ina l r e t u r n - t o - b a s e l i n e ser ies , they were s t i l l able to judge the shock levels w i t h o u t regard fo r the p lacebo . Or perhaps c o n d i t i o n i n g cannot occur w i t h o u t subject awareness (Dawson & Furedy, 1976) and these sub jec ts may have been d i s t rac t i ng themse lves f r o m the s i t ua t i on . This seems un l i ke ly due to the s ign i f i can t p lacebo response in con t ro l group sub jec ts . A n unexpected sex e f f e c t w a s d i scove red . M a l e s ' fac ia l a c t i v i t y dur ing n o - p l a c e b o t r ia ls w a s s i g n i f i c a n t l y greater than the f e m a l e s ' . Both groups were equiva lent dur ing the p lacebo t r ia ls . For c o n t r o l - g r o u p males o n l y , fac ia l a c t i v i t y was s i g n i f i c a n t l y greater in the n o - p l a c e b o t r ia ls than in the p lacebo t r ia ls . Thus s o m e ev idence accrued f o r nonverba l l y d i sp layed p lacebo e f f e c t s . Sex e f f e c t s were not p red ic ted because shock in tens i t y w a s ind iv idua l l y de te rm ined . H o w e v e r , males t o l e r a t e d higher shock leve ls and it is not clear whether those levels w e r e t ru l y equal to the leve ls t o l e r a t e d by the f e m a l e s . Some research ev idence has suggested that males are more s to ic f a c i a l l y (but more react ive p h y s i o l o g i c a l l y ) than f e m a l e s (Buck, Mi l le r , & Caul, 1974). The present resu l ts con t rad ic t that f i n d i n g unless one presumes that ma les d rop their s t o i c i s m w h e n they are 81 unaware o f be ing o b s e r v e d . A n x i e t y Three anx ie ty ra t ings accounted f o r 15% o f the var iance o f p lacebo reac t ion w h i c h imp l ies that there w a s a s ign i f i can t re la t ionsh ip b e t w e e n anx ie ty ra t ings and p lacebo reac t i on . L o w anx ie ty ra t ings b e f o r e the ascending ser ies and n o - p l a c e b o t r ia ls coup led w i t h high anx ie ty ra t ings be fo re p lacebo t r ia ls p red ic ted a p o s i t i v e p lacebo response. This runs counter t o the general n o t i o n that an u p c o m i n g p lacebo reduces anx ie ty and thereby e l i c i t s reduced pain repor t . It should be caut ioned that these resu l ts are o n l y t e n t a t i v e l y held s ince f a i r l y l iberal inc lus ion and exc lus ion c r i te r ia were used in the mu l t i p le reg ress ion ana lys is . Thus fur ther research is necessary t o e luc idate the c o m p l e x re la t ionsh ip b e t w e e n pa in , anx ie ty , and p lacebo mechan isms . S u m m a r y and Conc lus ions The present i nves t i ga t i on s u p p o r t e d and extended pr ior research de f in ing the fac ia l express ion o f pa in . Those AUs w h i c h occur red f requen t l y dur ing pain p red ic ted s e l f - r e p o r t e d pain unpleasantness and in tens i t y . Expectancy e f f e c t s alone ( e x e m p l i f i e d in the con t ro l g r o u p ) accounted f o r a s ign i f i can t p lacebo response . A l t h o u g h the present i nves t i ga t i on fa i l ed to suppor t the c o n d i t i o n i n g m o d e l o f p lacebo e f f e c t s , the fac t that a p lacebo e f f e c t was d e m o n s t r a t e d at all is s i gn i f i can t g i ven the f o r m e r conc lus ions that on ly 16% o f l abo ra to ry sub jec ts respond t o p lacebos (Evans, 1974). Failure t o rep l i ca te the Voudour i s et a l . (1985) resu l ts imp l i es that e i ther the c o n d i t i o n i n g mode l is incor rect and /o r that the m e t h o d o l o g y o f the present s tudy w a s w e a k . One argument against 82 the lat ter conc lus ion is that c o n t r o l group sub jec ts s h o w e d a s ign i f i can t p lacebo e f f e c t w h i c h shou ld have been apparent in the t w o exper imenta l g roups if the m a n i p u l a t i o n had had no e f f e c t . H o w e v e r , it is poss ib le that the man ipu la t i on w a s t o o weak t o cause a drast ic departure f r o m the con t ro l c o n d i t i o n . The p lacebo e f f e c t w a s d e m o n s t r a t e d across a range of shock in tens i t y leve ls and w a s best i l lus t ra ted by the Unpleasantness Scale in wh ich the p lacebo response w a s a s ign i f i can t main e f f e c t . The S e n s o r y Scale resul ts w e r e ve ry s im i la r to the Unpleasantness Scale resu l t s , w i t h th is one e x c e p t i o n , thus the t w o s e l f - r e p o r t measures d e m o n s t r a t e d p lacebo e f f e c t s . Facial a c t i v i t y w a s genera l ly less a f f e c t e d by the p lacebo man ipu la t ion and w a s i n v o l v e d in an unexpected sex e f f e c t : c o n t r o l g roup males on l y s h o w e d m o r e fac ia l a c t i v i t y in the n o - p l a c e b o t r ia ls than in the p lacebo t r i a l s . Labora to ry s tud ies p rov ide c o n t r o l l e d se t t i ngs , but in p lacebo research th is is at the cos t o f reduced p lacebo response. Because about hal f as many labo ra to ry sub jec ts as c l in ica l sub jects t y p i c a l l y respond t o p lacebos (Evans, 1974), fu tu re s tud ies migh t y ie ld more d e f i n i t i v e resu l ts us ing a c l in ica l p o p u l a t i o n in a c o n t r o l l e d se t t i ng . A n x i e t y seems t o be i n v o l v e d in p lacebo r e s p o n s e , but i ts c o m p l e x ro le remains to be c l a r i f i e d . E luc idat ion o f the p lacebo p rocess awa i ts d i s c o v e r y and it deserves that s tudy as s o m e t h i n g greater than an inert nuisance var iab le . Imp l i ca t i ons of th is research are t w o f o l d . The p lacebo p h e n o m e n o n might be exp lo i t ed as a t rea tmen t fo r acute pain pa t ien ts . Further, n e w t rea tmen ts must be s h o w n to exceed the p o w e r f u l p lacebo e f f e c t . 83 Future research is needed to der ive a c o m p l e t e exp lana t ion o f h o w the p lacebo br ings about change. In a d d i t i o n , s i tua t iona l and pe rsona l i t y var iab les w h i c h in teract w i t h p lacebo e f f e c t s are u n k n o w n . The p lacebo is p resen t l y an e lusive cons t ruc t that is beg inn ing to gain w idesp read and deserved a t t e n t i o n . 84 References A n d r e w , R.J. (1965). 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Science, 228, 1 5 - 2 1 . 93 Append ices 94 A , Gracely Rating Scales SENSORY INTENSITY UNPLEASANTNESS Ex t remely Intense 77.5 Very In to lerab le 38.7 Very Intense 56.4 In to lerab le 26.8 Intense 41.7 Very D is t ress ing 26.7 S t rong 28.8 S l i gh t l y In to lerab le 25.1 S l i gh t l y Intense 24.6 Very A n n o y i n g 17.8 Bare ly S t rong 15.4 D is t ress ing 12.4 Modera te 13.1 Very Unpleasant 11.7 M i l d 5.4 S l i gh t l y D is t ress ing 6.1 Very M i l d 3.6 A n n o y i n g 4.7 Weak 3.4 Unpleasant 4.0 Very Weak 1.7 S l i g h t l y A n n o y i n g 3.8 Faint 1.6 S l i gh t l y Unpleasant 3.5 No Sensat ion 0 No D i s c o m f o r t 0 (Gracely , McGra th , & Dubner, 1978). EL FACS A c t i o n Uni ts A U FACS N A M E 1 Inner b r o w ra ise 2 Outer b r o w raise 4 B r o w lowere r 5 Upper l id raise 6 Cheek raiser 7 L id t igh tener 10 Upper l ip raiser 11 Naso lab ia l deepen 12 Lip corner pul l 14 D imp le r 20 Lip s t re tcher 23 Lip t i gh t 25 Lips part 26 J a w drops 27 M o u t h s t re tches 43 Eyes c lose 45 Bl ink 96 C, Exper imenta l Par t i c ipa t ion Consent Form The pr inc ipa l i nves t iga to r o f th is s tudy is Dr. Kenneth D. Craig o f the P s y c h o l o g y Depar tment , te lephone This s tudy is suppor ted by a pharmaceut ica l supp ly c o m p a n y to tes t a new analgesic c ream wh ich is des igned t o act as a local anaesthet ic . It w i l l be tes ted us ing re la t i ve l y m i l d e lect r ic shocks to be presented th rough a smal l e lec t rode on the f o r e a r m . The f i r s t ser ies o f shocks w i l l begin at current in tens i t ies that cannot be de tec ted and w i l l increase each t i m e in sma l l amoun ts , up to a level that is no longer to le rab le . A t any t i m e dur ing th is sequence of shocks , s i m p l y say ing " s t o p " w i l l end the ser ies o f shocks , and no fur ther increases w i l l be de l i ve red . F o l l o w i n g the ser ies o f increas ing shocks , seven ser ies o f 9 shocks each w i l l be admin i s te red . These w i l l be w i t h i n the to le rab le range and w i l l be de l i ve red in a random order o f in tens i t ies . During four o f these ser ies the analgesic c ream w i l l be app l ied . A f t e r each s t imu lus is p resen ted , t w o verbal repor ts o f the amount o f d i s c o m f o r t exper ienced w i l l be requested . Your anx ie ty level w i l l be m o n i t o r e d at var ious t i m e s th roughout the exper iment . A p o s t - e x p e r i m e n t a l quest ionna i re w i l l a lso be g iven wh ich asks y o u fo r your reac t ions to the s tudy . The ent i re procedure should take be tween 60 and 90 minutes f o r w h i c h you w i l l be paid $6.00 per hour f o r your pa r t i c i pa t i on . A l l o f your responses w i l l be kept c o n f i d e n t i a l . If y o u have any ques t ions at any t i m e , p lease fee l f ree to ask the exper imenter , Delphin S w a l m . I hereby consent to par t i c ipa te in the s tudy as descr ibed . I understand that the r isks t o me as a subject are m i n i m a l . I fu r ther acknow ledge that I am aware that I can w i t h d r a w f r o m par t i c ipa t ion in the s tudy at any t i m e and I m a y re fuse t o answer any quest ions w i t h o u t p re jud ice . Date Signature Pr in ted name 97 D, Med ica l Screening Form Whi le the medica l r isk to y o u as a subject is m i n i m a l , s o m e peop le may respond p o o r l y to the analges ic c ream or to anx ie ty . The re fo re , i f y o u have h y p e r t e n s i o n , a heart p r o b l e m , a l le rg ic sk in r e s p o n s e s , are cur rent ly tak ing p resc r ibed m e d i c a t i o n , or there is any other med ica l reason y o u may be aware o f , it is adv isab le no t to pa r t i c ipa te . Please ind icate by s ign ing b e l o w that y o u have read th is and that y o u do not have any reason that might p revent you f r o m pa r t i c i pa t i ng . S ignature 98 E, Drug Check l is t B e l o w are l i s ted s o m e s y m p t o m s that peop le have repor ted w h e n an analgesic c ream w a s app l ied t o the i r sk in . Please t i ck o f f any responses that y o u are n o w exper ienc ing : 1. numbness 2. t i n g l i n g 3. w a r m t h 4. co ldness 5. burn ing 6. i tch ing 7. l i g h t - h e a d e d n e s s 8. b lur red v i s i o n 9. nausea 10. shor tness o f breath 11. t r e m b l i n g 12. o ther (please l is t add i t i ona l s y m p t o m s ) : 99 P o s t - E x p e r i m e n t a l Ques t ionna i re Your answers to the f o l l o w i n g ques t ions w i l l help us t o eva luate th is s t u d y ; all answers w i l l be kept c o n f i d e n t i a l . Please answer each ques t ion ca re fu l l y and h o n e s t l y . Circ le the appropr ia te number or check o f f your answer f o r each ques t ion . (1) . In genera l , h o w w o u l d y o u descr ibe the pain level p r o v o k e d by the s t imu l i y o u rece ived w i t h the analgesic c ream in c o m p a r i s o n t o those g i ven w i t h o u t the cream? The s t imu l i w i t h the c ream were. . . Much weaker 1..2..3..4..5..6..7....Much s t ronger (2) . H o w did y o u expect the analgesic cream to a f f e c t your pain level? I expected the pain level to be... Much weaker 1 ..2..3..4..5..6..7....Much s t ronger (3) . Were your expec ta t ions c o n f i r m e d ? Yes... No... If s o , when? (4) .Would y o u r e c o m m e n d th is analgesic cream t o a f r iend? Yes... No... (5) . Have you ever used an analgesic cream before? Yes... No... If s o , h o w e f f e c t i v e w a s it? Very effective..1..2..3..4..5..6..7..Not e f f e c t i v e (6) . Have y o u ever used any other k inds o f m e d i c a t i o n fo r pain be fore? (e.g., A s p i r i n , 292s, code ine) . Yes... No... Overa l l , h o w e f f e c t i v e are pain med ica t ions f o r you? Very Ef fec t ive . ,1 ..2..3..4..5..6..7..Not E f f e c t i v e (7) . In your o w n w o r d s , p lease state what y o u th ink the purpose o f th is s tudy w a s . 100 G_, Debr ie f i ng S tudy : Facial Express ion in P lacebo-Reduced Pain Dr. Kenneth D. Craig and Delphin S w a l m Depar tment o f P s y c h o l o g y , UBC T h a n k - y o u very much f o r pa r t i c i pa t i ng in th is s tudy . Since a major part o f h o w people respond t o ana lges ics depends on their expec ta t i ons , we dec ided t o tes t h o w e f f e c t i v e those expecta t ions rea l ly can be. The analgesic c ream w a s rea l ly a c ream that was neutral c h e m i c a l l y , i.e., it shou ld have had no e f f e c t s (it w a s a " p l a c e b o " substance) . We a t t e m p t e d to change your expec ta t ions about i ts e f f e c t i v e n e s s by man ipu la t i ng the shock level y o u rece ived wh i le the cream w a s app l ied . In cons t ras t to the ear l iest shock t r i a l s , some sub jec ts rece ived higher shocks , s o m e rece ived lower shocks , and a con t ro l group rece ived the same shock leve ls . The f i r s t ser ies o f r a n d o m shocks w i t h the c ream w i l l s h o w us whether your ra t ings changed or not as a resul t o f you r be l i e f s about the e f f e c t i v e n e s s o f analges ics (pa in - re l i ev ing m e d i c a t i o n s ) . We are a lso in te res ted in your fac ia l exp ress ions . For that reason w e v ideo taped your fac ia l express ions as the exper iment w a s conduc ted . W i t h your p e r m i s s i o n , w e w i l l examine the v ideo tape to see if your fac ia l express ion r e f l e c t e d any change in pa in fu lness . You may request that the v ideo tape be erased s ince w e d id not ask your pr ior p e r m i s s i o n to v ideo tape y o u . O t h e r w i s e , the v ideo tape w i l l be erased in 5 years . It w i l l be seen o n l y b y Dr. K. Craig and the research ass is tan ts f o r th is p ro jec t . A n d f i n a l l y , we are in te res ted in anx ie ty levels o f our sub jec ts s ince a poss ib le reason that peop le 's e s t i m a t e o f pain in tens i t y changes may be due to changes in thei r anx ie ty leve l . Th is research, then , w a s not connec ted in any manner to a pharmaceut ica l supp ly c o m p a n y and w e w e r e funded by a federa l g rant ing agency , not by a drug c o m p a n y . Since w e w i l l be ask ing s o m e o f you r c lassmates or acquaintances to par t i c ipa te in th is s t u d y , it is impor tan t that y o u avo id d iscuss ing th is s tudy 's purpose w i t h po ten t ia l sub jec ts . T h a n k - y o u ve ry much f o r you r c o o p e r a t i o n . If y o u w i s h to k n o w the o u t c o m e o f the s tudy or any fu r ther de ta i l s , p lease fee l f ree t o v i s i t the s tudent exper imente r , Delphin S w a l m , at her o f f i c e number 2527 in th is bu i ld ing . Thanks again f o r your pa r t i c i pa t i on in th is s tudy . N o w that the real c o n d i t i o n s o f the s tudy have been revea led , please s ign b e l o w to ind icate your consent to pe rm i t our use o f your v ideo tape and other da ta . Signature H, A N O V A Summary Tab 102 Table 7. Unpleasantness Scale Source df MS F Between Subjects Group (G) 2 476.208 0.72 Sex (S) 1 80.200 0.12 G x S 2 610.027 0.92 hin Ss Placebo / N o - p l a c b o ( P ) 1 248.865 4.83 * P r e - / P o s t - C o n d (T) 1 89.959 0.86 In tens i t y (I) 2 2194.744 55.84 • * * P x T 1 37.767 0.45 P x I 2 2.003 0.37 T x I 2 18.326 1.77 P x T x I 2 2.535 0.36 G x P 2 175.695 3.41 * G x T 2 133.520 1.28 G x I 4 54.634 1.39 S x P 1 55.278 1.07 S x T 1 156.707 1.50 S x I 2 62.288 1.58 G x S x P 2 11.900 0.23 G x S x T 2 0.284 0.00 G x S x I G x P x T G x P x I G x T x I S x P x T S x P x I S x T x I G x S x P x T G x S x T x I G x S x P x I G x P x T x I S x P x T x I G x S x P x T x l 4 95.713 2.44 2 38.933 0.46 4 15.201 2.77 * 4 11.536 1.12 1 42.389 0.50 2 5.132 0.94 2 8.329 0.81 2 54.480 0.65 4 20.474 1.98 4 7.691 1.40 4 5.985 0.85 2 0.196 0.03 4 3.832 0.55 p < . 0 0 1 , * * p < . 0 1 , • p < . 0 5 Table 8. Sensory Scale Source Be tween Subjects Group (G) Sex (S) G x S W i t h i n Ss P l a c e b o / N o - p l a c b o ( P ) P r e - / P o s t - C o n d (T) In tens i t y (I) P x T P x I T x I P x T x I G x P G x T G x I S x P S x T S x I G x S x P G x S x T df MS F 2 2729.647 0.88 1 88.620 0.03 2 113.653 0.04 1 800.113 3.41 1 411.627 1.05 2 16764.368 74.94 • • • 1 224.004 0.62 2 45.053 2.21 2 56.625 1.51 2 38.029 1.41 2 811.014 3.46 * 2 1144.934 2.92 4 432.067 1.93 1 224.227 0.96 1 61.2507 0.16 2 88.545 0.40 2 242.966 1.04 2 160.008 0.41 105 G x S x I , 4 282.855 1.26 G x P x T 2 137.977 0.38 G x P x I 4 53.713 2.64 * G x T x I 4 71.958 1.92 S x P x T 1 90.171 0.25 S x P x I 2 35.486 1.74 S x T x I 2 27.679 0.74 G x S x P x T 2 106.391 0.29 G x S x T x I 4 147.516 3.94 * * G x S x P x I 4 45.505 2.24 G x P x T x I 4 17.751 0.66 S x P x T x I 2 3.409 0.13 G x S x P x T x l 4 33.564 1.25 p < . 0 0 1 , * * p < . 0 1 , * p < . 0 5 106 Table 9. Facial A c t i v i t y Source df MS F B e t w e e n Subjects Group (G) 2 2.599 1.05 Sex (S) 1 5.604 2.27 G x S 2 1.524 0.62 hin Ss P l a c e b o / N o - p l a c b o ( P ) 1 0.086 0.22 P r e - / P o s t - C o n d (T) 1 0.665 0.96 In tens i t y ( I ) 2 2.197 11.21 * * • P x T 1 0.122 0.38 P x I 2 0.091 0.69 T x I 2 0.053 0.34 P x T x I 2 0.455 3.50 * G x P 2 0.101 0.25 G x T 2 0.042 0.06 G x I 4 0.290 1.48 S x P 1 1.880 4.72 • S x T 1 1.515 2.18 S x I 2 0.248 1.26 G x S x P 2 1.745 4.39 • G x S x T 2 0.773 1.11 G x S x I G x P x T G x P x I G x T x I S x P x T S x P x I S x T x I G x S x P x T G x S x T x I G x S x P x I G x P x T x I S x P x T x I G x S x P x T x l 4 0.307 1.57 2 0.660 2.06 4 0.235 1.78 4 0.098 0.62 1 0.035 0.11 2 0.221 1.68 2 0.205 1.30 2 0.066 0.21 4 0.092 0.59 4 0.043 0.33 4 0.141 1.09 2 0.050 0.39 4 0.090 0.69 * • • p < . 0 0 1 , p < . 0 1 , • p < . 0 5 Tables o f Cell Means and Standard Dev ia t ions Table 10. Unp leasantness Scale INTENSITY C o n d i t i o n Mean (Std Dev) L o w 6.94 (7.62) M e d i u m 9.44 (8.97) High 12.95 ( 1 ° - 6 4 ) PLACEBO/NO-PLACEBO C o n d i t i o n Mean (Std Dev ) P lacebo 9.19 (8.97) No Placebo 10.36 (9.93) Table 11. GROUP X PLACEBO/NO-PLACEBO Placebo No Placebo Group I 9.08 (8.71) 9.29 (10.01) Group II 8.67 (7.77) 8.84 (8.20) Group Placebo 9.81 (9.14) No Placebo 12.96 (9.68) 111 Table 12. GROUP X PLACEBO/NO-PLACEBO X INTENSITY Group I Group II Placebo No Placebo Placebo No Placebo L o w 6.34 (6.93) 6.95 (8.59) 6.36 (6.68) 6.65 (7.59) M e d i u m 8.77 (8.73) 9.45 (10.46) 8.16 (7.21) 8.33 (7.80) High 12.15 (10.50) 11.50 (10.98) 11.50 (9.42) 11.55 (9.21) Group III Placebo No Placebo L o w 6.61 (8.01) 7.71 (7.86) M e d i u m 9.33 (8.77) 12.58 (9.79) High 13.48 (10.64) 17.58 (11.41) Table 13. Sensory Scale INTENSITY C o n d i t i o n Mean (Std D e v ) L o w 14.12 (15.49) M e d i u m 20.94 (19.00) High 30.74 (23.25) Table 14. GROUP X PLACEBO/NO-PLACEBO Group I Group II P lacebo 18.60 (17.15) 21.46 (18.50) No Placebo 19.67 (20.16) 61.56 (19.16) Group III P lacebo 22.58 (19.24) No Placebo 28.77 (21.08) 114 Table 15. GROUP X PLACEBO/NO-PLACEBO X INTENSITY Group I Group II Placebo No Placebo Placebo L o w M e d i u m High 11.86 (13.60) 17.76 (16.71) 26.17 (21.14) 12.60 (14.45) 19.93 (21.86) 26.47 (24.16) 15.67 (15.61) 19.51 (17.91) 29.20 (21.99) No Placebo 13.97 (15.55) 19.22 (18.55) 28.38 (23.25) Group III Placebo No Placebo L o w M e d i u m High 13.09 (16.02) 22.04 (19.17) 32.61 (22.52) 17.51 (18.20) 27.18 (20.54) 41.64 (24.51) 115 Table 16. GROUP X SEX X PRE/POST X INTENSITY Group I Male P r e - T r e a t m e n t : L o w M e d i u m High 10.69(11.56) 20.84 (19.40) 30.20 (25.72) Female 13.50 (12.22) 17.44 (15.86) 24.42 (16.09) Group 1I Male 17.35 (11.92) 20.94 (15.33) 32.36 (21.26) Female 16.07 (18.44) 23.43 (23.56) 34.42 (27.81) Group III Male Female L o w 13.88 (17.84) 14.91 (13.26) Med ium 23.20 (21.09) 24.21 (18.24) High 34.22 (22.98) 36.36 (23.89) P o s t - T r e a t m e n t : Group I Group II Male Female Male Female L o w 10.15 (13.17) 14.60 (18.96) 13.63 (14.29) 12.22 (17.67) M e d i u m 17.78 (19.95) 19.32 (21.94) 14.43 (13.66) 18.67 (20.37) High 26.02 (24.11) 24.65 (24.68) 20.42 (15.94) 27.96 (25.48) Group III Male Female L o w 14.27 (17.14) 18.15 (20.23) M e d i u m 24.82 (18.15) 26.21 (21.94) High 43.31 (20.96) 34.61 (26.24) Table 17. A c t i o n Un i ts INTENSITY Cond i t i on Mean (Std Dev ) L o w .482 (.488) M e d i u m .634 (.606) High .658 (.671) Table 18. SEX X PLACEBO/NO-PLACEBO Male Female P lacebo No Placebo .618 .742 (.575) (.797) .543 (.508) .463 (.475) 118 Table 19. GROUP X SEX X PLACEBO/NO-PLACEBO Group I Male P lacebo No Placebo .506 (.390) .561 ( , 5 0 2 ) Female Group 11 Male Female .428 (.399) .394 (.418) .836 (.803) .791 (.849) .448 (.441) .468 (.485) Placebo No Placebo Group III Male .511 (.533) .872 (1.039) Female .754 (.683) .527 (.521) 119 Table 20. PRE/POST X PLACEBO/NO-PLACEBO X INTENSITY Pre Placebo L o w M e d i u m High No Placebo .522 (.505) .647 (.598) .703 (.651) .474 .713 .672 (.483) (.671) (.661) Post Placebo .438 .626 .547 (.430) (.525) (.541) No Placebo .494 (.534) .551 (.630) .711 (.832) 

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