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Journal of Experimental Psychology: General Copyright 1998 by the American PsychologicalAssociation, Inc.1998, Vol. 127, No. 3, 304-310 0096-3445/98/$3.00

C O M M E N T SO n D e m o n s t r a t in g U n c o n s c i o u s P e r ce p tio n :C o m m e n t on D r a in e a nd G r e e n w a l d ( 1 9 9 8 )

Philip M. M erikleUniversity of W aterloo Eyal M. ReingoldUniversity of TorontoS. C. Draine and A. G. Greenwald (1998) ha ve described a m ethodology based on regressionanalysis for demonstrating unconscious perception. They h ave suggested that their methodol-ogy represents a ma jor improve me nt ov er exist ing m ethodologies. An analysis o f theirmethodology reveals that it is closely related to the classic dissociation paradigm. As such,interpretation of their results is compromised by the sa me issues concerning the m easurementof awareness that have plagued all previous at tempts to use the dissociation paradigm todemonstrate unconscious perception in the complete absence of conscious perception.

T h e e x p e r i m e n t s d e s c r i b e d b y D r a i n e a n d G r e e n w a l d(1998) ad d res s one o f t h e o ld es t r esea rch que s t i ons i ne x p e r i m e n t a l p s y c h o l o g y . N a m e l y , i s m e a n i n g f u l i n f o r m a -t io n p e r c e i v e d e v e n w h e n t h e r e i s n o a w a r e n e s s o f p e r c e i v -i n g ? T h i s q u e s ti o n h a s b e e n t h e s u b j e c t o f h u n d r e d s o fe m p i r i c a l s t u di e s , d a t in g f r o m t h e v e r y b e g i n n i n g o f e x p e r i -m e n t a l p s y c h o l o g y i n N o r t h A m e r i c a ( e . g. , P e ir c e & J a s tr o w ,1884; S id i s , 1898) . O n t h e bas i s o f t h ese s t ud i es , t h e re i sn o w a g r o w i n g c o n s e n s u s t h a t p e r c e p t i o n i n t h e a b s e n c e o ft h e s u b j e c t iv e e x p e r i e n c e o f p e r c e i v i n g i s a g e n u in e p h e n o m -enon ( e .g . , H i r s t , 1995 ; K ih l s t rom, 1987 ; Mer ik l e , 1992) .H o w e v e r , d e s pi t e th i s g ro w i n g c o n s e n s u s , D r a i n e a n d G r e e n -wa ld ' s a r t i c l e is p ro of t h a t i t is s t i ll p os s ib l e t o q ues t i on t h ev e r y e x i s t e n c e o f u n c o n s c i o u s p e r c e p t i o n a s a v a l i d p s y c h o -l o g i c a l p h e n o m e n o n .

T h e p r i m a r y q u e s t io n t h a t w e a d d r e s s i n th i s c o m m e n t a r yi s d o e s t h e m e t h o d o l o g y d e s c r ib e d b y D r a i n e a n d G r e e n w a l d( 1 9 9 8 ) r e p r e s e n t a m a j o r i m p r o v e m e n t o v e r o t h e r m e t h o d o l o -g i e s u s e d t o s t u d y p e r c e p t i o n w i t h o u t a w a r e n e s s ? T h e i rm e t h o d o l o g y i s b a s e d o n a m i x t u r e o f id e a s t a k e n f r o m b o t ht h e c l a s s i c d i s soc i a t i on p a rad ig m and t h e r e l a t i ve sens i t i v i t ya p p r o a c h d e s c r i b e d p r e v i o u s l y b y R e i n g o l d a n d M e r i k l e( 1 9 8 8 ). D r a i n e a n d G r e e n w a l d s u g g e s t t h a t t h e ir m e t h o d o l -o g y i s b e t t e r t h a n e x i s t i n g m e t h o d o l o g i e s . W e d i s a g r e e .R a t h e r, w e s u g g e s t t h a t t h e ir m e t h o d o l o g y i s c l o s e l y r e l a te dt o t h e c l a ss i c d i s s o c ia t i o n p a r a d i g m . A s s u c h , i t h a s m a n y o ft h e w e a k n e s s e s o f t h e c l a ss i c d i s s o c ia t i o n p a r a d i g m a n dn o n e o f t h e a d v a n t a g e s o f t he r e l a t i v e s e n s i t iv i t y a p p r o a c h .

Philip M. Merikle, Department of Psychology, University ofWaterloo, Waterloo, Ontario, C anada; Ey al M. Reingold, Depart-ment of Psychology, University of Toronto, Toronto, Ontario,Canada.Preparation of this article w as supported by research grants fromthe Natural Sciences and Engineering R esearch Council o f Canada.Correspondence concerning this article should be addressed toPhilip M . Merikle, Department of Psychology, University o fWaterloo, Waterloo, Ontario, Canada N2L 3G1. Electronic mailma y be sent to pm erikle@uw aterloo.ca.

F o r t h e s e r e a s o n s , w e d o n o t b e l i e v e t h a t D r a i n e a n dG r e e n w a l d ' s m e t h o d o l o g y r e p r e s e n t s a si g n if i c an t a d v a n c eo v e r t h e o t h e r m e t h o d s t h a t a r e a v a i l a b l e f o r s t u d y i n gu n c o n s c i o u s p e r c e p t i o n . I n f a c t , w e s u g g e s t t h a t r i g o r o u sa p p l i c a ti o n o f D r a i n e a n d G r e e n w a l d ' s m e t h o d o l o g y c o u l dl e a d t o m i s l e a d in g c o n c l u s io n s .

T h e C l a s s ic D i s s o c i a ti o n P a r a d i g mT h e v a s t m a j o r i t y o f s t u d i e s d i r e c t e d a t d e m o n s t r a t i n gp e r c e p t i o n w i t h o u t a w a r e n e s s h a v e u s e d a v a r i a n t o f t h e

d i s s o c ia t i o n p a r a d i g m . T h e p r i m a r y g o a l o f e x p e r i m e n t s t h a ta r e b a s e d o n t h e d i s s o c i a t i o n p a r a d i g m h a s b e e n t o d e m o n -s t r a t e t h a t i t i s p os s ib l e t o p erce ive s t imul i i n t h e comp le t ea b s e n c e o f a n y c o n s c i o u s a w a r e n e s s o f t h e se s t im u l i . T od e m o n s t r a t e p e r c e p t i o n i n t h e a b s e n c e o f a w a r e n e s s , i t i sn e c e s s a r y t o ( a ) i d e n t i fy a m e a s u r e o f c o n s c i o u s p e r c e p t i o n ,(b ) sh ow t h a t t h is me asure o f p e rcep t i on i nd i ca t es t h a t t h es t im u l i w e r e n o t p e r c e i v e d , a n d ( c ) f in d a s e c o n d m e a s u r e o fp ercep t i on t h a t i nd i ca t es t h a t t h e s t imul i were p erce ivedu n d e r t h e s a m e c o n d i ti o n s t h a t th e m e a s u r e o f c o n s c i o u sp ercep t i on i nd i ca t es t h a t t h e s t imul i were no t p e rce ived .

O n e o f t h e b e s t k n o w n a p p l ic a t i o n s o f t h e d i s s o c ia t i o np a r a d i g m i s M a r c e l ' s ( 1 9 8 3 ) c l a s s i c e x p e r i m e n t i n w h i c h h ed e m o n s t r a t e d s e m a n t i c p r i m i n g i n t h e a b s e n c e o f s t i m u l u sd e t ec t i on . Marce l ' s exp er iment i l l us t r a t es t h e t h ree ma j orc o m p o n e n t s o f a n y d e m o n s t r a t i o n o f p e r c e p t i o n w i t h o u tawareness t h a t i s based on t h e d i s soc i a t i on p a rad ig m. F i r s t ,h e u s e d s t i m u l u s d e t e c t i o n a s th e m e a s u r e o f c o n s c i o u sp e r c e p t io n . S e c o n d , h e e s t a b l i s h e d t h e e x p e r i m e n t a l c o n d i -t i ons t h a t mad e i t imp oss ib l e f o r th e p a r t i c ip an t s t o d i sc r imi -n a t e a t a b e t t e r t h a n c h a n c e l e v e l o f a c c u r a c y b e t w e e n t h ep r e s e n c e o r a b s e n c e o f t h e s ti m u l i. T h i r d, h e u s e d a m e a s u r eo f s e m a n t i c p r i m i n g t h a t w a s b a s e d o n r e a c t i o n t i m e t o s h o wt h a t d esp i t e t h e p a r t i c ip an t s ' i nab i l i t y t o d e t ec t t h e s t imul i , i twas s t i l l p os s ib l e f o r t h e s t imul i t o p r ime subsequen td ec i s i ons r eg a rd ing o t h er s t imul i .F i n d i n g s s u c h a s t h o s e r e p o r t e d b y M a r c e l ( 1 9 8 3 ) h a v econs id erab l e i n t u i t i ve ap p ea l . Th e f ac t t h a t t h e p a r t i c ip an t s

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C OMMENTS 305c o u l d n o t d i s t i n gu i s h b e t w e e n t h e p r e s e n c e o r a b s e n c e o f t h es t imul i ce r ta in ly sugges t s tha t they were comple te ly un-aware o f these s t imul i . Giv en tha t the s ame s t imul i tha t thepa r t ic ipan t s were unab le to de tec t cou ld never the les s in f lu -e n c e h o w r a p i d l y t h e y c o u l d m a k e s u b s e q u e n t d e c i s i o n srega rd ing o the r s t imul i , i t i s no t surp r i s ing tha t Ma rce l andm a n y o t h e r i n v e s t i g a t o r s r e a c h e d t h e c o n c l u s i o n t h a t t h es t im u l i w e r e p e r c e i v e d w i t h o u t a w a r e n e s s .H o w e v e r , e v e n t h o u g h t h e l o g i c u n d e r l y i n g t h e d i ss o c i a-t ion pa rad igm i s s t r a igh t forward , in te rp re ta tion o f the r esu l t so f e x p e r i m e n t s t h a t a r e b a s e d o n t h e d i s s o c ia t i o n p a r a d ig mhas no t been s t r a igh t forward . There a r e two in te r r e la tedis sues tha t hav e c loude d in te rp re ta t ion . Bo th i s sues concernt h e m e a s u r e o f c o n s c i o u s p e r c e p t i o n , w h i c h m u s t b e a d -e q u a t e b e f o r e a n y d i s s o c i a t i o n b e t w e e n m e a s u r e s c a n b ec o n s i d e r e d a d e m o n s t r a t io n o f u n c o n s c i o u s p e r c e p t i o n .I s t he Me as ur e o f C ons c i ous Per cep t i on Va l i d?

I n a n y s t u d y o f u n c o n s c i o u s p e r c e p t i o n b a s ed o n t h ed is soc ia t ion pa rad igm, the mos t impor tan t i s sue concernsw h e t h e r t h e m e a s u r e o f c o n s c i o u s p e r c e p t i o n h a s a s s e s se da l l r e l e v a n t c o n s c i o u s l y p e r c e i v e d i n f o r m a t io n . B e f o r e t h ed is soc ia t ion pa rad igm can be used succes s fu l ly , a d i r ec tmeasure o f consc ious percep t ion tha t a s ses ses a l l r e levan tconsc ious percep tua l exper iences mus t be iden t i f ied . I s i tpos s ib le to f ind such a measure? We do no t th ink so . Theredoes no t s eem to be any bas i s to a s sume a p r io r i tha t anyp a r t i c u l a r d i r e c t m e a s u r e o f p e r c e p t i o n i s a n e x h a u s t i v em e a s u r e o f a l l r e l e v a n t c o n s c i o u s e x p e r i e n c e s . N o m a t t e rwha t d i r ec t measure o f percep t ion i s s e lec ted , the re i s now a y t o d e m o n s t r a t e c o n c l u s i v e l y t h a t t h i s m e a s u r e i s ac o m p l e t e l y s a t i s f a c to r y m e a s u r e o f a l l r e l e v a n t c o n s c i o u sexper ience . Al thou gh measures su ch a s s t imulus de tec t ionhave c ons iderab le in tu i t ive appea l , in the f ina l ana lys i s thea r g u m e n t f a v o r i n g a p a r t i c u la r d i r e c t m e a s u re a l w a y s c o m e sdow n to a p laus ib i l i ty a rgument . As ind ica ted by Dra ine andG r e e n w a l d ( 1 9 9 8 ) i n r e f e r e n c e to t h e d i r e c t m e a s u r e s t h a tthey used to a s ses s consc ious percep t ion , " a l though thea s s u m p t i o n o f e x h a u s t i v e s e n s it i v it y t o c o n s c i o u s p r o c e s s i n gis p laus ib ly va l id fo r the d i r ec t measures , our exper imentsp r o v i d e d n o e m p i r i c a l c o n f i r m a t i o n o f t h i s a s s u m p t i o n "(p . 301).D o e s t h e M e a s u r e o f C o n s c i o u s P e r c e p ti o n S h o wN u l l Sens i t iv i t y ?

A s e c o n d i s su e t h a t m u s t b e a d d r e ss e d w h e n e v e r t h ed i s s o c ia t i o n p a r a d i g m i s u s e d t o d e m o n s t r a t e u n c o n s c i o u sp e r c e p t io n c o n c e r n s w h e t h e r t h e p r o c e d u r e s w e r e a d e q u a t et o d e m o n s t r a t e t h a t t h e m e a s u r e o f c o n s c i o u s p e r c e p t i o nexh ib i t s a t r ue nu l l s ens i t iv i ty (c f . Macm i l lan , 1986) . Beforea n y d i s s o c i a t i o n b e t w e e n m e a s u r e s c a n b e c o n s i d e r e d a se v i d e n c e f o r u n c o n s c i o u s p e r c e p t i o n , t h e m e a s u r e o f c o n -sc ious percep t ion m us t ind ica te tha t the pa r t ic ipan t s d id no tperce ive the s t imul i . O therwise , i t i s a lways pos s ib le toa rgue tha t consc ious percep t ion , a lbe i t m in ima l consc iousp e r c e p ti o n , m a y h a v e c o n t r i b u te d t o t h e o b s e r v e d f i nd i n gs .B u t h o w i s i t p o s s i b l e t o p r o v e c o n c l u s i v e l y t h a t a n y

measure o f percep t ion exh ib i t s a t r ue nu l l s ens i t iv i ty?W h e n e v e r t h e r e s u l t s o f a n e x p e r i m e n t s u g g e s t s t h a t apa r t icu la r measure exh ib i t s no s ens i t iv i ty , i t i s a lwaysp o s s i b le t o a r g u e t h a t th e m e t h o d o l o g y m a y h a v e b e e ninadequa te to r evea l the t r ue s ens i t iv i ty o f the measure . I fnu l l e f fec t s a r e a lways open to such a l t e rna t ive in te rp re ta -t ions , then i t may be imposs ib le to ever demons t r a te in ac o m p l e t e l y c o n v i n c i n g m a n n e r t h a t a m e a s u r e o f c o n s c i o u spercep t ion e xh ib i t s a t r ue nu l l s ens i tiv i ty .

T h e R e l a t i v e S e n s i t i v i ty A p p r o a c hSevera l yea r s ago , we sugges ted an a l t e rna t ive to thed is soc ia t ion pa rad igm for demons t r a t ing unconsc ious in f lu -ences (e .g ., R e ingold & Mer ik le , 1988 , 1990) . Th is a l t e rna -t ive app roach i s based on compar i sons o f the r e la t ivesens i t iv i ty o f comparab le d i r ec t and ind i r ec t measures o fpercep t ion or memory . Our goa l in sugges t ing th i s a l t e rna -t ive app roach was to desc r ibe a method for demons t r a t ingunconsc ious p roces ses in percep t ion , l ea rn ing , and memorytha t d id no t r equ i r e e i the r (a ) a measure o f a l l r e levan tconsc iou s percep tua l exper iences o r (b ) a demo ns t r a t ion tha tt h e m e a s u r e o f c o n s c i o u s p e r c e p t i o n e x h i b i t e d a t r u e n u l lsens i t ivi ty.B e f o r e d e f i n in g w h a t i s m e a n t b y t h e p h r a se comparabledirect and indirect measures or d i s cus s ing the concep tua land methodolog ica l advan tages o f the r e la t ive s ens i t iv i tyapp roach , i t i s use fu l to desc r ibe an exper iment tha t i l lus -t r a tes the app roach . An ex ce l len t example i s the now -c las s ics tudy by Kuns t -Wi lson and Za jonc (1980) . In th i s s tudy ,pa r t ic ipan t s were in i t i a l ly shown 10 i r r egu la r geomet r icshapes . Each shape was p rese n ted f ive t imes fo r a 1 -msdura t ion , and no pa r t ic ipan t ever r epor ted s ee ing an y of the

shapes . Fo l lowing these in i t i a l p r esen ta t ions , memory forthe shapes was a s ses sed by bo th a r eco gni t ion t es t and ap re fe r enc e tes t . For bo th t es t s , the pa r tic ipan t s we re show n10 pa ir s o f shapes , wi th each pa i r cons i s t ing of 1 o ld and 1new shape . For the r ecogni t ion t es t , the pa r t ic ipan t s wereexp l ic i t ly ins t ruc ted to s e lec t the member o f each pa i r tha thad been p resen ted p rev ious ly . For the p re fe r ence t es t , thepa r t ic ipan t s were s imp ly to ld to s e lec t the shape tha t theyp re fe r r ed , wi th no r e fe r ence be ing m ade to the d i s t inc t ionbe tw een o ld ands new shapes . The r esu l t s o f the s tudy showtha t the pa r tic ipan t s s e lec ted the p rev ious ly p resen ted shapei n a p p r o x i m a t e l y 6 0 % o f t h e p a i rs w h e n t h e y s e l e c te d t h eshape tha t they p re fe r r ed , bu t w hen the y se lec ted the shapetha t they though t had been p resen ted p rev ious ly , the i rper form ance d id no t d i f fe r f rom ch ance ( i . e ., 50%) .T h e K u n s t - W i l s o n a n d Z a j o n c ( 1 9 8 0 ) s t u d y p r o v i d e sc o m p e l l i n g e v i d e n c e o f u n c o n s c i o u s m e m o r y f o r b r i e f l yp resen ted s t imul i . In fac t , the Kuns t -Wi lson and Za joncf i n di n g s s e e m t o b e a n i n t u i t iv e l y m o r e c o n v i n c i n g d e m o n -s t r a t ion o f an unconsc ious in f luence than a r e the r esu l t s o fm a n y o f t h e e x p e r i m e n t s b a s e d o n t h e d i s s o c i a t i o n p a r a -d igm. Wha t makes the i r f ind ings so compel l ing i s tha tK u n s t - W i l s o n a n d Z a j o n c u s e d c o m p a r a b l e d i r e c t ( r ec o g n i -t ion) and ind i r ec t (p r e fe r ence) measures . Both m easureswere based on (a ) the s ame s tudy cond i t ions , (b ) the s ametes t cond i t ions , (c ) the s ame pa i r s o f s t imul i , and (d ) the

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306 COM M E NT Ss a m e r e s p o n s e m e t r i c . I n f a c t , t h e o n l y d i f f e r e n c e b e t w e e nmeasur es was t he i ns t r uc t i ons . F or t he r ecogn i t i on t e s t , t hepa r t i c i pan t s we r e g i ven d i r ec t i ns t r uc t i ons and t o l d exp l i c i t l yt o s e l e c t t h e o n e s h a p e i n e a c h p a i r t h a t h a d b e e n p r e s e n t e dpr ev i ous l y . I n con t r a s t , f o r t he p r e f e r ence t e s t , t he pa r t i c i -pan t s wer e g i ven i nd i r ec t i ns t r uc t i ons and t o l d exp l i c i t l y t os e l e c t t h e s h a p e i n e a c h p a i r t h a t t h e y p r e f e r r e d , w i t h n or e f e r e n c e b e i n g m a d e i n t h e i n s t r u c t io n s t o t h e f a c t th a t o n es h a p e i n e a c h p a i r h a d b e e n p r e s e n t e d p r e v i o u s l y . D e s p i t et h e a b s e n c e o f a n y r e f e r e n c e i n t h e i n d i re c t i n s tr u c t io n s t ot h e o l d - n e w d i s c r i m i n a t i o n , t h e i n d i r e c t m e a s u r e ( i . e . ,p r e f e r e n c e ) w a s a m o r e s e n s i t i v e m e a s u r e o f t h e o l d - n e wd i s c r im i n a t i o n t h a n t h e d i r e c t m e a s u r e ( r e c o g n it i o n ).

C o m p a r i s o n s o f t h e r e l a t i v e s e n s i t i v i t y o f c o m p a r a b l ed i r e c t a n d i n d i r e c t m e a s u r e s h a v e a n i m p o r t a n t c o n c e p t u a la d v a n t a g e o v e r a p p r o a c h e s b a s e d o n t h e d i s s o c i a t i o n p a r a -d i g m . N a m e l y , a m u c h m o r e m i n i m a l a s s u m p t i o n i s r e q u i r e di n o r de r t o i n t e r p r e t g r ea t e r s ens i t i v i t y f o r an i nd i r ec t t han ad i r e c t m e a s u r e a s e v i d e n c e f o r u n c o n s c i o u s p e r c e p t i o n . A l lt h a t n e e d s t o b e a s s u m e d i s t h a t t h e s e n s i t iv i t y o f t h e d i r e c tm e a s u r e t o c o n s c i o u s l y - p e r c e i v e d , t a s k - r e l e v a n t i n f o r m a t i o ni s equa l t o o r g r ea t e r t han t he s ens i t i v i t y o f t he i nd i r ec tm e a s u r e t o t h e s a m e i n f o r m a t i o n ( R e i n g o l d & M e r i k l e ,1988 , 1990) . T he r a t i ona l e unde r l y i n g t h i s a s sum pt i on i s t ha tc o n s c i o u s l y p e r c e i v e d i n f o r m a t i o n r e l e v a n t t o a p a r t i c u l a rd i s c r im i n a t i o n ( e . g . , a n o l d - n e w j u d g m e n t ) , i f i t e x is t s ,s h o u l d b e u s e d e q u a l l y o r m o r e e f f i c ie n t l y w h e n p a r t i c i p a n tsa r e i ns t r uc t ed exp l i c i t l y t o make t he d i sc r i mi na t i on ( i . e . , ad i r e c t m e a s u r e ) t h a n w h e n p a r t i c i p a n t s a r e i n s t r u c t e d t oj u d g e t h e s t i m u l i o n s o m e o t h e r b a s i s ( i . e . , a n i n d i r e c tmeasure).

B a s e d o n t h i s m i n i m a l a s s u m p t i o n , a n u n c o n s c i o u s i n f lu -e n c e i s i m p l i c a t e d w h e n e v e r a n i n d i r e c t m e a s u r e i s m o r es e n s i t i v e t h a n a c o m p a r a b l e d i r e c t m e a s u r e t o t h e s a m ep e r c e p t u a l d i s c r i m i n a t i o n . T h i s i s t h e c a s e b e c a u s e t h eu n d e r l y i n g a s s u m p t i o n r u l e s o u t t h e p o s s i b i l i ty t h a t s u p e r i o rp e r f o r m a n c e o n t h e i n d i r e c t t a s k i s a t t r i b u t a b l e t o t h ep e r c e p t i o n o f c o n s c i o u s , t a s k - r e le v a n t i n f o r m a t i o n . T h e r e -f o r e , b y d e f a u l t , w h e n e v e r a n i n d i r e c t m e a s u r e i s m o r es e n s i t i v e t h a n a c o m p a r a b l e d i r e c t m e a s u r e , i t m u s t r e f l e c tt h e i n f lu e n c e o f u n c o n s c i o u s , t a s k - r e l e v a n t i n f o rm a t i o n . O fcour se , t h i s i n t e r p r e t a t i on i s on l y w ar r an t ed i f t he d i r ec t andi n d i r e c t m e a s u r e s a r e t r u l y c o m p a r a b l e e x c e p t f o r t h er e f e r en ce i n the d i r ec t - t a sk i ns t r uc t i ons t o t he d i sc r i mi na t i ono f i n te r e st . I f t h e m e a s u r e s a r e n o t c o m p a r a b l e , t h e n g r e a t e rs e n s i ti v i ty f o r a n i n d i r e c t th a n a d i r e c t m e a s u r e m a y s i m p l yr e f l e c t a m e t h o d o l o g i c a l d i f f e r e n c e b e t w e e n t h e d i r e c t a n di n d i r e ct m e a s u r e s r a t h e r t h a n a n u n c o n s c i o u s i n f lu e n c e .T h e m i n i m a l a s s u m p t i o n u n d e r l y i n g t h e r e l a t iv e s e n s i t iv -i t y a p p r o a c h g i v e s i t a n i m p o r t a n t m e t h o d o l o g i c a l a d v a n t a g eo v e r a p p r o a c h e s b a s e d o n t h e d i s s o c i a t i o n p a r a d i g m . G i v e nt h a t i n f e r e n c e s r e g a r d i n g t h e p r e s e n c e o r a b s e n c e o f a nu n c o n s c i o u s p r o c e s s a r e b a s e d o n c o m p a r i s o n s o f t h es e n s i ti v i ty o f c o m p a r a b l e d i r e c t a n d i n d i r e c t m e a s u r e s , t h e r ei s n o n e e d t o d e m o n s t r a t e t h a t a d i re c t m e a s u r e e x h i b i t s n u l ls e n s it i v it y , a s i s t h e c a s e f o r a n a p p r o a c h b a s e d o n t h ed i s s o c i a ti o n p a r a d i g m . T h e o n l y c r i ti c a l e x p e r i m e n t a l f i n d -i n g t h a t is n e c e s s a r y t o i n f e r t h e p r e s e n c e o f a n u n c o n s c i o u spr oces s i s g r ea t e r s ens i t i v i t y f o r an i nd i r ec t t han f o r a

c o m p a r a b l e d i r e c t m e a s u r e . T h u s , w i t h t h e r e l a t iv e s e n s i t i v -i t y a p p r o a c h , t h e p r e s e n c e o f a n u n c o n s c i o u s p r o c e s s i si m p l i e d w h e n e v e r t h e i n d i r e c t m e a s u r e i s m o r e s e n s i t i v et h a n a c o m p a r a b l e d i r e c t m e a s u r e , a n d t h i s i s t r u e e v e n i ns i tu a t io n s w h e r e t h e o v e r a l l a c c u r a c y f o r t h e d i r e c t m e a s u r em a y b e a b o v e c h a n c e .

T h e I n d i r e c t- W i t h o u t - D i r e c t D a t a P a t t e r nD r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) p r i m a r y g o a l w a s tod e m o n s t r a t e " . . . s e m a n t i c a c t i v a t i o n i n t h e a b s e n c e o fc o n s c i o u s c o g n i t i o n " ( p . 2 8 7 ) . T h e y e x p r e s s t h e b e l i e f t h a t

t h e " . . . e m p i r i c a l e v i d e n c e f o r u n c o n s c i o u s p e r c e p t i o nr e m a i n s c o n t r o v e r s i a l " ( D r a in e & G r e e n w a l d , 1 9 9 8 , p . 2 8 6 )b e c a u s e i t h a s b e e n d i f f i c u l t t o d e v e l o p c o n v i n c i n g e x p e r i -m e n t a l d e m o n s tr a t io n s " . . . s h o w i n g s ta t is ti c al ly s i gn i fi c an ti n d i r e c t e f f e c t s f o r s t i m u l i t h a t p r o d u c e n o e v i d e n c e f o rd i r ec t e f f ec t s " ( p . 286) . T hus , i n conduc t i ng t he i r s t ud i e s ,t h e i r p r i m a r y g o a l w a s t o s h o w t h a t a n i n d i r e c t m e a s u r e o fp e r c e p t i o n c a n i n d i c a t e t h a t a s t i m u l u s h a s b e e n p e r c e i v e de v e n w h e n a d i r e c t m e a s u r e o f p e r c e p t i o n s h o w s a b s o l u t e l yno sens i t i v i t y t o t he s ame s t i mul us . T h i s goa l has been t hegoa l o f a l l s t ud i e s based on t he c l a s s i c d i s soc i a t i on pa r a -d i g m . I t h a s n o t b e e n t h e g o a l o f s t u d i e s b a s e d o n t h e r e l a t i v es e n s i t i v i t y a p p r o a c h b e c a u s e s u c h s t u d i e s r e q u i r e o n l y a ni nd i r ec t - g r ea t e r - t han- d i r ec t r a t he r t han an i nd i r ec t - w i t hou t -d i r e c t d a ta p a t t e r n t o d e m o n s t r a t e u n c o n s c i o u s p e r c e p t io n .

D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) s t a t e t h a t i t h a s p r o v e nd i f f i c u l t t o d e v e l o p c o m p l e t e l y c o n v i n c i n g d e m o n s t r a t i o n sof t he i nd i r ec t - w i t hou t - d i r ec t da t a pa t t e r n . T h i s i s t rue on l y i ft h e i r a s s u m p t i o n r e g a r d i n g w h a t c o n s t i t u t e s a n a c c e p t a b l em e a s u r e o f a w a r e n e s s i s a c c e p t e d . D r a i n e a n d G r e e n w a l ds u g g e s t t h a t t h e o n l y c o m p l e t e l y a c c e p t a b l e w a y t o m e a s u r ea w a r e n e s s i s to u s e o b j e c t i v e m e a s u r e s o f p e r c e p t u a l d i s c r im i -n a t io n s . I f D r a i n e a n d G r e e n w a l d ' s p o s i t i o n i s a c c ep t e d , t h e nce r t a i n l y i t has been d i f f i cu l t t o demons t r a t e t he i nd i r ec t -w i t h o u t - d i re c t d a t a p a t t e rn . H o w e v e r , i f m e a s u r e s o f t h es u b j e c t i v e e x p e r i e n c e o f p e r c e iv i n g a r e a s s u m e d t o b ea p p r o p r i a t e d i r e c t m e a s u r e s o f a w a r e n e s s ( e .g . , C h a l m e r s ,1996 ; M er i k l e , 1992 ; W ei skr an t z , 1986) , t hen t he r e i s ac o n s i d e r a b l e b o d y o f e v i d e n c e t h a t h a s b e e n a c c u m u l a t i n gf o r m o r e t h a n 1 0 0 y e a r s t h a t d e m o n s t r a t e s t h e c r i t i c a li nd i r ec t - w i t hou t - d i r ec t da t a pa t t e r n ( s ee Ad am s , 1957; M i l le r ,1942, f o r r ev i ew s o f t he ea r l y s t ud i e s ) .

G i v e n D r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) b e l i e f t h a t ac o n v i n c i n g d e m o n s t r a t io n o f t h e i n d i r e c t- w i t h o u t - d ir e c t d a t ap a t t e r n m u s t b e b a s e d o n s t u d i e s i n v o l v i n g o b j e c t i v e , d i r e c tm e a s u r e s o f p e r c e p t u a l d i s c r im i n a t i o n s , t h e i r p r e f e r r e dm e t h o d f o r a s s e s s i n g t h e p r e s e n c e o r a b s e n c e o f a w a r e n e s si s a m e a s u r e o f p e r c e p t u a l s e n s i ti v i ty ( i .e . , d ' ) b a s e d o n at w o - a l t e r n a t i v e , f o r c e d - c h o i c e t a s k . T h e s t r o n g a s s u m p t i o ni m p l i e d b y t h e i r a p p r o a c h i s t h at t h e r e is a c o m p l e t e a b s e n c eo f a l l r e l e v a n t c o n s c i o u s p e r c e p t u a l e x p e r i e n c e s w h e n e v e rd ' = 0 . I t i s u n c l e a r w h e t h e r t h e y a l s o b e l i e v e t h a t a d 'g r e a t e r t h a n z e r o i s a n i n d i c a ti o n t h a t r e l e v a n t i n f o r m a t i o nw a s c o n s c i o u s l y p e r c e i v e d o r w h e t h e r t h e y b e l i e v e t h a t a d 'g r ea t e r t han ze r o can a t t i mes be an i nd i ca t i on t ha t t her e l e v a n t in f o r m a t i o n w a s u n c o n s c i o u s l y p e r c e i v e d .D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) r e c o g n i z e t h a t t w o i s s u e s

7/30/2019 Merikle & Reingold 1998 on Demonstrating Unconscious Perception - Comment on Draine and Greenwald (1998)

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COMMENTS 307m u s t b e a d d r e s s e d a n d r e s o l v e d b e f o r e i t i s p o s s i b l e t odem ons t ra te tha t an ind i rec t -wi thou t -d i rec t da ta pa t t e rnp r o v i d e s c o n v i n c i n g e v i d e n c e f o r p e r c e p t i o n i n t h e c o m p l e t eabsenc e o f awarenes s . F i r s t , the d i rec t and ind i rec t m easuresm u s t b e c o m p a r a b l e . S e c o n d , t h e r e m u s t b e a c o m p l e t ed i s soc ia t ion be twe en the d i rec t and ind i rec t m easures in tha tthe d i rec t m easures m us t have ze ro o r nu l l s ens i t iv i ty to thesam e pe rcep tua l d i s c r im ina t ion to which the ind i rec t m ea-sures a re s ens i t ive . In the fo l low ing sec t ions , we d i s cus s thes u c c e s s o f D r a i n e a n d G r e e n w a l d ' s e x p e r i m e n t s i n d e a l i n gwi th these i s sues.Are the Direct and Indirect Measures Comparable ?

I n j u s t i f y in g t h e c o m p a r a b i l i ty o f t h e i r d i r e c t a n d i n d i r e c tm e a s u r e s , D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) p a y c o n s i d e r a b l ea t t e n ti o n t o R e i n g o l d a n d M e f i k l e ' s ( 1 9 8 8 ) p r e v i o u s a n a l y s iso f d i r e c t a n d i n d i r e c t m e a s u r es . A c c o r d i n g t o R e i n g o l d a n dMer ik le , th ree c r i t e r i a m us t be s a t i s f i ed be fore e i the r theind i rec t -wi thou t -d i rec t da ta pa t t e rn o r the ind i rec t -g rea te r -t h a n - d i r e c t d a t a p a t t e r n c a n p r o v i d e s t r o n g e v i d e n c e f o runco nsc iou s pe rcep t ion . These c r i t e r i a a re tha t the d i rec t andt h e i n d i r e c t m e a s u r e s m u s t ( a ) b e b a s e d o n t h e s a m eresponse m e t r i c , (b ) index the s am e pe rcep tua l d i s c r im ina -t ion , and (c ) be adm in i s te red under the s am e s tudy and t e s tcondi t ions .I n E x p e r i m e n t s 1 , 2 , a n d 3 o f D r a i n e a n d G r e e n w a l d(1998) , the d i rec t and ind i rec t m easures s a t i s fy the f i r s tc r i t e r ion in tha t bo th m easures a re based on the s am eresponse m e t r i c ( i . e . , d ' ) . However , the m easures used inthe i r Exper im ents 1 , 2 , and 3 do no t s a t i s fy the s econd andth i rd c r i t e r i a . Wi th re fe rence to the s econd c r i t e r ion , thei n d i r e c t a n d d i r e c t m e a s u r e s i n d e x e d d i f f e r e n t p e r c e p t u a ld i s c r im ina t ions . The ind i rec t m easures indexed the pa r t i c i -pan t s ' ab i l i ty to d i s c r im ina te be tween sem ant ic ca tegor ie s( i . e . , m a l e - f e m a l e o r p l e a s a n t - u n p l e a s a n t ) , w h e r e a s t h ed i rec t m easures in dex ed the pa r t i c ipan t s ' ab i l i ty to d i s c r im i -na te be tween words and a s t r ing o f a l t e rna t ing Xs and Gs( i .e ., t h e X G v W d [ X G v e r s u s W o r d ] t a s k ) . W i t h r e f e r e n c e t othe th i rd c r i t e r ion , the ind i rec t and d i rec t m easures wereas ses sed under cons ide rab ly d i f fe ren t condi t ions . The ind i -r e c t m e a s u r e s i n v o l v e d t h e r e s p o n s e - w i n d o w p r o c e d u r e ,w h i c h r e q u i r e d t h e p a r t ic i p a n ts t o r e s p o n d w i t h i n a n e x p e r i -m ente r -de f ined , t em pora l in te rva l . In con t ra s t , wi th thed i rec t m easures , the pa r t i c ipan t s were m ore o r l e s s f ree tor e s p o n d a n y t i m e f o l l o w i n g t h e o n s e t o f t h e t a r g e t s t im u l u s .D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) r e c o g n i z e t h e i n t e r p r e ti v ep r o b l e m s t h a t a r i se w h e n e v e r t h e d i r e c t a n d i n d i r e c t m e a -s u r es a r e n o t c o m p a r a b l e . T h e y s u g g e s t t h a t " . . . s u b j ec t sm i g h t h a v e a p p r o a c h e d t h e X G v W d t a s k w i t h th e s t r a t eg y o fa t t en d i n g t o p h y s i c a l i n f o r m a t i o n o f t h e p r i m e s i n o r d e r t oi d e n t i f y X s o r G s ( r a t h e r t h a n t r y i n g t o r e a d w o r d s ) " ( D r a i n e& G reenw ald , 1998 , p . 295) . I f the pa r t i c ipan t s d id adopt th i ss t r at e g y w h e n p e r f o r m i n g t h e d i r e c t ta s k , t h e n " t h i s s t r a t e g yc o u l d h a v e r e d u c e d c o n s c i o u s p e r c e p t i o n o f s e m a n t i c i n f o r -m a t i o n d u r i n g t h e d i r e c t - m e a s u r e t a s k c o m p a r e d t o t h es t r at e g y r e q u i r e d b y t h e i n d i r e c t - m e a s u r e ta s k o f a t t e n d in g t ot h e m e a n i n g o f t h e t a rg e t s t i m u l i " ( D r a i n e & G r e e n w a l d ,1998 , p . 295) . In o the r words , g iven tha t the d i rec t and

ind i rec t ta sks used in the i r Exper im e nts 1 , 2 , and 3 were no tc o m p a r a b l e , D r a i n e a n d G r e e n w a l d s u g g e s t t h a t t h e re s u l tso f t h e s e e x p e r i m e n t s m a y n o t n e c e s s a r i l y p r o v i d e e v i d e n c ef o r u n c o n s c i o u s p e r c e p t io n .T o o v e r c o m e t h e in t e r p r e ti v e p r o b l e m s t h a t c o m p r o m i s e dthe re su l t s o f the i r Exper im ents 1 , 2 , and 3 , Dra ine andG r e e n w a l d ( 1 9 9 8 ) i n t r o d u c e d a s e c o n d d i r e c t m e a s u r e i nE x p e r i m e n t 4 . T h e i r g o a l w a s t o h a v e a d i r e c t m e a s u r e t h a tw a s m o r e s i m i la r t o t h e i n d i r e c t m e a s u re . T h i s s e c o n d d i r e c tm easure , the d i rec t s em ant ic -c la s s i f i ca t ion (DS C) t a sk , re -qu i red pa r t i c ipan t s to c la s s i fy the p r im es in t e rm s of the i rs em ant ic ca tegory ( i . e . , p leasan t vs . unp leasan t o r m a le vs .f e m a l e ) . G i v e n t h a t th e D S C t a s k i n d e x e d t h e s a m e p e r c e p -tua l d i s c r im ina t ion a s the ind i rec t ta sk (Cr i t e r ion 2 ) and w asb a s e d o n t h e s a m e r e s p o n s e m e t r i c a s t h e i n d i r e c t t a s k(Cr i t e r ion 1 ) , the DS C ta sk ce r ta in ly was be t t e r m a tched tot h e i n d i r e c t t a s k t h a n a n y o f t h e o t h e r d i r e c t m e a s u r e s u s e d i nt h e i r e x p e r i m e n t s .H o w e v e r , t h e r e a r e s t il l s o m e v e r y i m p o r t a n t d i f f e re n c e si n t h e t e s ti n g c o n d i t i o n s u s e d f o r t h e D S C a n d t h e i n d i r e c tt a sks (Cr i t e r ion 3 ) . Once aga in , the ind i rec t t a sk wasa d m i n i s t e re d u s i n g t h e r e s p o n s e - w i n d o w p r o c e d u r e , w h e r e a st h e D S C t a s k w a s a d m i n i s te r e d u n d e r c o n d i t i o n s t h a t d i d n o tr e q u i r e t h e p a r t ic i p a n ts t o r e s p o n d w i t h i n a n e x p e r i m e n t e r -de f ined , t em pora l in te rva l. In add i t ion , w i th the ind i rec t t a sk ,the pa r t i c ipan t s were requ i red to c la s s i fy c lea r ly v i s ib leta rge t words , whereas wi th the DS C ta sk , the pa r t i c ipan t swere req u i red to c la s s i fy d i f f i cu l t - to -pe rce ive p r im es in thepresence o f a c lea r ly v i s ib le , bu t i r re levan t , t a rge t words .D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) a s s u m e d t h a t t h e p a r t ic i p a n tsw e r e a b l e t o f o l l o w t h e D S C t a s k i n s tr u c t io n s t o i g n o r e t h ec lea r ly v i s ib le t a rge t words and to d i rec t a t t en t ion com -ple te ly to the t a sk o f t ry ing to c la s s i fy the p r im es .

T h e r e s u l ts o f D r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) E x p e r i m e n t4 s h o w t h a t t h e p a rt i ci p a n ts c o u l d n o t p e r f o r m t h e D S C t a sk .T h e i r p e r f o r m a n c e o n t h e t a s k d i d n o t d i f f e r f r o m c h a n c e( i .e . , d ' = 0 ) whe th e r the p r im es were p resen ted fo r 17 m s or33 m s ( s ee Dra ine & Green wald , 1998 , F igure 6 ) . I f th i sinab i l i ty o f the pa r t i c ipan t s to c la s s i fy the p r im es i s a s sum edt o i n d i c a t e a n a b s e n c e o f c o n s c i o u s p e r c e p t i o n , t h e n t h eo b s e r v e d p r i m i n g r e v e a l e d b y t h e i n d i r e c t m e a s u r e w o u l dre f lec t unconsc ious s em ant ic p r im ing . However , i t i s a l sop o s s i b le t h a t o t h e r f a c t o r s m a y h a v e m a d e i t i m p o s s i b l e f o rthe pa r t i c ipan t s to d i s c r im ina te the s em ant ic ca teg ory o f thep r i m e s w h e n t h e y p e r f o r m e d t h e D S C t a s k . F o r e x a m p l e ,g i v e n t h a t t h e p r e s e n t a t i o n o f e a c h p r i m e w a s f o l l o w e di m m e d i a t e l y b y t h e p r e s e n t a t io n o f a c l e a r l y v i s ib l e t a r g e tword , i t i s ve ry pos s ib le tha t the t a rge t word cap tureda t t en t ion so tha t i t was im poss ib le to a t t end to s em ant icca tegory o f the p r im es . In fac t , the expe r im enta l condi t ionsu s e d f o r t h e D S C t a s k a r e v e r y s i m i la r t o t h e e x p e r im e n t a lc o n d i t i o n s t h a t a r e k n o w n t o l e a d t o c o n c e p t u a l m a s k i n g(e . g . , In t raub , 1984; Lof tus , Hanna , & Les te r , 1988) . I fc o n c e p t u a l m a s k i n g d i d o c c u r , t h e n t h e p a r t ic i p a n ts w o u l dh a v e f o u n d i t d i f f i cu l t i f n o t i m p o s s i b l e t o a t t e n d t o t h e p r i m ec las s i f i ca t ion t a sk once the i r a t t en t ion was cap tured by ac lea r ly v i s ib le t a rge t word .A n o t h e r r e a s o n w h y t h e D S C t a s k m a y h a v e f a i l e d t or e v e a l a n y e v i d e n c e t h a t t h e p r i m e s w e r e p e r c e i v e d i s t h a t

7/30/2019 Merikle & Reingold 1998 on Demonstrating Unconscious Perception - Comment on Draine and Greenwald (1998)

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308 COMMENTSthe pr im es w er e ine f f ec t ive by the t im e tha t the pa r t ic ipan tsr e s p o n d e d . F r o m G r e e n w a l d , D r a in e , a n d A b r a m s ' s ( 1 9 9 6 )e x p e r i m e n t s , w e k n o w t h a t e v i d e n c e f o r s e m a n ti c p r i m i n g i sr e v e a l e d b y t h e r e s p o n s e - w i n d o w p r o c e d u r e o n l y w h e n t h etem por a l in te r va l s epa r a t ing the onse t s o f the p r im es andta r ge t s is l e s s than 100 m s . I f the e f f ec t ivenes s o f p r im esd is s ipa te s wi th in 100 m s , then i t i s no t su r pr i s ing tha t theD S C t a s k r e v e a l e d n o e v i d e n c e t h a t t h e p r i m e s w e r epe r ce ived . Given tha t the pa r t i c ipan ts wer e no t r equ i r ed tor e s p o n d w i t h i n a s h o r t r e s p o n s e w i n d o w w h e n t h e y p e r -f o r m ed th i s t a sk , the i r m or e l e i sur e ly r e sponses m ay haveb e e n m a d e b e y o n d t h e t e m p o r a l i n t e r v a l w h e n t h e p r i m e swer e e f f ec t ive .The f ac t tha t the r e a r e a l t e r na t ive in te r pr e ta t ions o f thepa r t i c ipan ts ' inab i l i ty to pe r f o r m the DS C ta sk i l lust r a te s thetypes o f in te r pr e t ive i s sues tha t can a r i s e whenever theexper im enta l condi t ions f o r adm in is te r ing d i r ec t and ind i -r ec t t a sks a r e no t com ple te ly m a tched . I f the d i r ec t andi n d i r e ct t as k s h a d b e e n c o m p l e t e l y m a t c h e d i n t e r m s o f a l lth r ee c r i t e r i a desc r ibed by Re ingold and Mer ik le ( 1988) ,then these in te r pr e t ive am bigu i t i e s would no t have a r i s enand any ind i r ec t - g r ea te r -than- d i r ec t da ta pa t t e r n wo uld hav eb e e n s t ro n g e v i d e n c e f o r u n c o n s c i o u s p e r c e p t io n . H o w e v e r ,g iven the in te r pr e t ive am bigu i t i e s , the r e su l t s o f a l l f oure x p e r i m e n t s re p o r t e d b y D r a i n e a n d G r e e n w a l d ( 1 9 9 8 ) s e e mcons i s ten t wi th an y of the f o l low ing in te r pre ta t ions :1 . Bo th the d i r ec t and the ind i r ec t m easur es a s sessunconsc ious pe r cep t ion . The d i f f e r en t ia l s ens i t iv i ty o f them easur es ind ica te s tha t each m e asur e i s m axim a l ly s ens i t iveto d i f f e r en t cha r ac te r is t i c s o f the p r im es .2 . Bo th the d i r ec t and the ind i r ec t m easur es a s ses sconsc ious pe r cep t ion . The d i f f e r en t ia l s ens i t iv i ty o f them easur es ind ica te s tha t each m e asur e i s m axim a l ly s ens i t iveto d i f f e r en t cha r ac te r i s t ic s o f the p r im es .3 . The d i r ec t and ind i r ec t m easur es a r e s ens i t ive to bo thc o n s c i o u s l y a n d u n c o n s c i o u s l y p e r c e i v e d i n f o rm a t i o n . T h edi f f e r en t ia l s ens i t iv i ty o f the m easur es ind ica te s tha t eachm easu r e i s m axim a l ly s ens i t ive to d i f f e r en t cha r ac te r i s ti c s o ft h e p r i m e s a n d t h a t e a c h m e a s u r e i n d e x e s a s o m e w h a td i f f e r e n t c o m b i n a t i o n o f c o n s c i o u s l y a n d u n c o n s c i o u s l yp e r c e i v e d i n f o rm a t i o n .4 . The d i r ec t m easur es index a l l r e levan t consc ious lyp e r c e i v e d i n f o r m a t i o n r e g a r d i n g t h e p r i m e s . T h e i n d i r e c tm e a s u r e s i n d e x u n c o n s c i o u s l y p e r c e i v e d i n f o r m a t i o n r e g a rd -ing the p r im es .G i v e n t h e m e t h o d o l o g y u s e d b y D r a i n e a n d G r e e n w a l d( 1998) , we do no t s ee any s t r a igh t f or war d way to d i s en-tang le these a l t e rna t ive in te r pr e ta t ions o f the ind i r ec t -wi thou t -d i r ec t da ta pa t t e rns f ou nd in the i r expe r im ents .Does the Regression Analysis Demonstrate Perceptionin the Complete Absence of Conscious Awareness?

To es tab l i sh the c r i t i ca l ind i r ec t - wi thou t - d i r ec t da ta pa t -t e r n , Dr a ine and Gr eenwald ( 1998) used a r egr es s iona n a l y s i s i n e a c h e x p e r i m e n t t o d e t e rm i n e i f t h e r e w a s as ta t i s t i ca l ly s ign i f i can t in te r cep t f o r the ind i r ec t m easur ewh en the d i r ec t m easur e w as used a s the p r ed ic to r va r iab le .I n e f f ec t , a s t a t i s t i ca l pa r t i c ipan t was c r ea ted by each

r egr es s ion ana lys i s f o r pur poses o f eva lua t ing the c r i t i ca lind i r ec t - wi thou t - d i r ec t da ta pa t t e r n . The log ic und er ly ingthe r egr es s ion s t r a tegy i s s t r a igh t f or war d ; a s ign i f i can tin te r cep t ind ica te s tha t the s ens i t iv i ty o f the ind i r ec t m ea sur ei s g r ea te r than ze r o when the s ens i t iv i ty f o r the d i r ec tm easu r e i s equa l to ze r o . Thus , a s ign i f i can t in te r cep t f o r theind i r ec t m easur e cons t i tu te s a dem ons t r a t ion of the c r i t i ca lind i r ec t - wi thou t - d i r ec t da ta pa t t e r n . As such , i t i s cons ide r edt o b e s t ro n g e v i d e n c e t h a t t h e s t i m u l i w e r e p e r c e i v e d i nt h e c o m p l e t e a b s e n c e o f a n y c o n s c i o u s a w a r e n e s s ( c f .Gr eenw ald , Kl inge r , & S chu h , 1995) . Howe ver , be f or e ther egr es s ion s t r a tegy can be in f or m a t ive , two con di t ions m us tb e m e t .F i r s t , a s f o r a l l o the r app l ica t ions o f the d i s soc ia t ionp a r a d i g m , t h e d i r e c t m e a s u r e s c h o s e n t o i n d e x c o n s c i o u sp e r c e p t i o n m u s t b e v a l i d m e a s u r e s o f a l l r e l e v a n t c o n -sc ious ly pe r ce ived in f or m a t ion . I f the d i r ec t m easur es a r eno t com ple te ly s a t i s f ac to r y , then the r egr es s ion s t r a tegy ,e v e n t h o u g h i t i s a r a t h e r c l e v e r m e t h o d f o r d e m o n s t r a t in gthe ind i r ec t - wi thou t - d i r ec t da ta pa t t e r n , i s no t any m or ei n f o r m a t i v e th a n a n y o t h e r a p p r o a c h b a s e d o n t h e d i s s o c ia -t i o n p a r a d i g m . W e h a v e a l r e a d y d i s c u s s e d a n u m b e r o fr e a s o n s w h y t h e d i r e c t t a sk s u s e d b y D r a i n e a n d G ~ e e n w a ld( 1 9 9 8 ) m a y n o t b e c o m p l e t e l y s a t i s f a c t o r y . G i v e n t h eques t ions tha t can be r a i s ed r ega r d ing these t a sks , we do no tb e l i e v e t h a t D r a i n e a n d G r e e n w a l d ' s e v i d e n c e f o r u n c o n -sc ious pe r cep t ion i s any m or e com pe l l ing than the f ind ingsf r om m any o the r s tud ies tha t have e s tab l i shed d i s soc ia t ionsb e t w e e n d i r e c t a n d i n d i r e c t m e a su r e s o f p e r c e p t i o nT h e s e c o n d c o n d i t i o n t h a t m u s t b e m e t b e f o r e t h er egr es s ion s t r a tegy can be in f or m a t ive i s tha t the r e m us t bes o m e d e g r e e o f a s s o c i a ti o n o r c o r r e l a t io n b e t w e e n t h e d i r e c tand ind i r ec t m easur es . I n f ac t , i f the d i r ec t and ind i r ec tm easur es a r e no t cor r e la ted to any gr ea t ex ten t , then the r e isr ea l ly no r eason to com pute a r egr es s ion ana lys i s . I n theabsence o f a cor r e la t ion be tween the d i r ec t and ind i r ec tm easur es , a r egr es s ion ana lys i s s im ply r evea l s tha t thein te r cep t f o r the ind i r ec t m easur e appr ox im a tes the ove r a l ls ens i t iv i ty o f the ind i r ec t m easur e .A r e v i e w o f D r a in e a n d G r e e n w a l d ' s ( 1 9 9 8 ) fi g u re s s h o w stha t in eve r y expe r im ent the ove r a l l s ens i t iv i ty o f theind i r ec t m easur e ( i . e . , the m ean in the upper l e f t o f eachf igur e ) i s appr ox im a te ly the s am e s ize a s the in te r cep t in ther egr es s ion equa t ion . Given tha t the s lopes in 17 of the 18r egr es s ion ana lyses shown in the f igur es wer e no t s ign i f i -can t , i t i s no t su r pr i s ing tha t the ove r a l l s ens i t iv i ty o f theind i r ec t m easur es i s an exce l len t p r ed ic to r o f the in te r cep t s .The sm a l l and m os t ly nons ign i f i can t s lopes f ound in ther egr es s ion ana lyses ind ica te tha t the cor r e la t ions be tweenthe d i r ec t and ind i r ec t m easur es a r e a l so sm a l l and m os tl ike ly nons ign i f i can t . Thus , in the absence o f s ign i f i can tcor r e la t ions be tween the d i r ec t and ind i r ec t m easur es , non e w i n f o r m a t i o n is a d d e d b y t h e r e g r e ss i o n a n a l y se s . U n d e rthese condi t ions , the ove r a l l s ens i t iv i ty o f an ind i r ec tm e a s u r e i s a g o o d p r e d i c t o r o f t h e i n t e r c e p t f o r t h e i n d i re c tm e a s u r e .A n o t h e r c o n s e q u e n c e o f t h e s m a l l a n d n o n s i g n i f i c a n tcor r e la t ions be tween the d i r ec t and ind i r ec t m easur es i s tha tthe s ta t i s t ica l pa r t i c ipan ts c r ea ted b y the r eg r es s ion ana lyses

7/30/2019 Merikle & Reingold 1998 on Demonstrating Unconscious Perception - Comment on Draine and Greenwald (1998)

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COMMENTS 309a r e n o t r e p r e s e n t a t i v e o f t h e m a j o r i t y o f t h e p a r t i c i p a n ts w h ow e r e t e s t ed i n e a c h e x p e r i m e n t . A r e v i e w o f t h e s c a t te r p l o tsp r e s e n t e d i n D r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) f i g u r e s r e v e a l stha t the re i s no cons i s ten t re la t ion ac ros s pa r t i c ipan t sb e t w e e n p e r f o r m a n c e o n t h e d i r e c t m e a s u r e s a n d p e r f o r -m a n c e o n t h e i n d i r e c t m e a s u r e s. I n f a c t , i n e a c h e x p e r i m e n t ,t h e r e w a s o n l y a s m a l l s u b g r o u p o f p a r t ic i p a n ts w h o s h o w e dthe c r i t i ca l ind i rec t -w i thou t -d i rec t da ta pa t t e rn . The re m a in-ing pa r t i c ipan t s showed e i the r a d i rec t -g rea te r - than- ind i rec td a t a p a t te r n o r r o u g h l y e q u i v a l e n t p e r f o r m a n c e o n t h e t w om easures . Thus , the m a jor i ty o f pa r t i c ipan t s in each expe r i -m ent d id no t show the c r i t i ca l ind i rec t -wi thou t -d i rec t da tapa t t e rn . In o the r words , the m a jor i ty o f pa r t i c ipan t s d id no ts h o w e v i d e n c e o f p e r c e p t i o n w h e n t h e d i r e c t m e a s u r e o fconsc ious pe rcep t ion exh ib i t ed nu l l s ens i t iv i ty . Ra the r , ine a c h e x p e r i m e n t , t h e m a j o r i t y o f t h e p a r t i c i p a n t s s h o w e dda ta pa t t e rns tha t a re inconc lus ive wi th rega rd to theq u e s t i o n o f w h e t h e r t h e p r i m e s w e r e p e r c e i v e d w i t h o rwi thou t awarenes s .

C o n c l u d in g C o m m e n t sD r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) e x p e r i m e n t s fo l l o w a l o n gt rad i t ion o f s tud ies tha t have a t t em pted to dem ons t ra tep e r c e p t i o n i n t he c o m p l e t e a b s e n c e o f a w a r e n e ss . D o D r a i n ea n d G r e e n w a l d ' s e x p e r i m e n t s p r o v i d e m o r e c o m p e l l i n ge v i d e n c e f o r u n c o n s c i o u s p e r c e p t i o n t h a n i s p r o v i d e d b ym a n y p r e v i o u s s t u d ie s ? W e d o n o t t h i n k s o . T h e i r r e g r e s si o ns t ra tegy i s sub jec t to the s am e c r i t i c ism s tha t can be d i rec teda t any expe r im ent based on the c la s s ic d i s soc ia t ion pa ra -d i g m . N a m e l y , q u e st i o n s c a n b e r a i s e d r e g a r d i n g ( a ) w h e t h e rthe m easures tha t they used to a s ses s consc ious pe rcep t iona r e a d e q u a t e m e a s u r e s o f a l l r e l e v a n t c o n s c io u s e x p e r i e n c e s

a n d ( b ) w h e t h e r t h e i r m e t h o d o l o g y w a s a d e q u a t e t o d e m o n -s t ra t e t h a t t h e m e a s u r e s o f c o n s c i o u s p e r c e p t i o n e x h i b i t e dnul l s ens i t iv i ty fo r the m a jor i ty o f the pa r t i c ipan t s . Giventhese questions, w e d o no t believe that their findings necessarilyprovide bet ter evidence for unconscious percept ion than isprovided b y results o f man y previous experiments.D r a i n e a n d G r e e n w a l d ' s ( 1 9 9 8 ) e x p e r i m e n t s r e p r e s e n tw h a t i s p r o b a b l y t h e m o s t r i g o r o u s a p p l i c a t i o n o f t h ed i s s o c ia t i o n p a r a d i g m t o t h e s t u d y o f u n c o n s c i o u s p e r c e p -t i o n t h a t h a s e v e r b e e n r e p o r t ed . T h r o u g h t h e i r e x p e r i m e n t s ,D r a i n e a n d G r e e n w a l d h a v e p u s h e d t h e d i s s o c i a t i o n p a r a -d igm to i t s l im i t s in t ry ing to e s tab l i sh tha t s e lec ted m easuresof consc ious pe rc ep t ion a s ses s a ll re levan t consc iou s expe r i -e n c e s . H o w e v e r , i n o u r v i e w , D r a i n e a n d G r e e n w a l d w e r eu n s u c c e s s f u l in p r o v i d i n g a c o m p l e t e l y c o n v i n c i n g d e m o n -s t ra t ion o f unconsc ious pe rcep t ion . Th i s ou tcom e i l lus t ra te show fu t i l e i t i s to use the d i s soc ia t ion pa rad igm to dem on-s t r a t e u n c o n s c i o u s p e r c e p t i o n i n t h e c o m p l e t e a b s e n c e o fc o n s c i o u s p e r c e p t io n . I t m a y j u s t b e i m p o s s i b l e t o d e s i g n a nexper im ent tha t s a t i s f i e s the log ica l requ i rem ents o f thed i s soc ia t ion pa rad igm . P e rhaps , a f t e r m ore than 100 yea rs o finconc lus iv e expe r im en ts , i t i s t im e to aban don the re sea rchs t ra tegy of a t t em pt ing to e s tab l i sh d i s soc ia t ions to dem on-s t ra te unconsc ious pe rcep t ion .A n o t h e r r e a s o n i t i s p r o b a b l y w i s e t o a b a n d o n t h ed i s s o c ia t i o n p a r a d i g m i n s t u d ie s o f u n c o n s c i o u s p e r c e p t i o n

i s tha t r igorous app l ica t ion o f the d i s soc ia t ion pa rad igm canr e s u l t i n m i s l e a d i n g c o n c l u s i o n s . A s n o t e d b y D r a i n e a n dG r e e n w a l d ( 1 9 9 8 ) , a n i m p o r t a n t r e q u i r e m e n t t h a t m u s t b esa t i s f i ed whenever the d i s soc ia t ion pa rad igm i s used tod e m o n s t r a t e u n c o n s c i o u s p e r c e p t i o n i s t h a t t h e s e l e c t e dm e a s u re o f c o n s c io u s p e r c e p ti o n m u s t b e " . . . m a x i m a l lysens i t ive to consc iou s s t im ulus e f fec t s " (F oo tno te 3 ) . I t i s fo rth i s reason tha t they a t t em pted to f ind the m os t s ens i t ived i r e c t m e a s u r e o f p e r c e p t i o n a n d t h e n t o e s t a b l i s h t h eexper im enta l condi t ions in which th i s d i rec t m easure exh ib-i t ed ze ro o r nu l l s ens i t iv i ty . How ever , th i s re sea rch s t ra tegyc a n b e s u c c e s sf u l o n l y i f t h e d i r e c t m e a s u r e o f p e r c e p t i o n i ss e n s i t i v e o n l y t o c o n s c i o u s l y p e r c e i v e d i n f o r m a t i o n ( c f .R e i n g o l d & M e r i k l e , 1 9 8 8 , 1 9 9 0 ) . I f t h e d i r e c t m e a s u r e o fp e r c e p t i o n h a p p e n s t o b e s e n s i ti v e t o b o t h c o n s c i o u s l y a n du n c o n s c i o u s l y p e r c e i v e d i n f o r m a t i o n , t h e n t h e s t r a t e g y o fes tab l i sh ing nu l l s ens i t iv i ty fo r the d i rec t m easure w i l l l eadt o a s e v e r e u n d e r e s ti m a t i o n o f u n c o n s c i o u s p e r c e p t io n .P rev ious ly , we sugges ted tha t a reasonab le a p r io r ie x p e c t a t i o n r e g a r d i n g a n y m e a s u r e o f p e r c e p t i o n , e i t h e rd i rec t o r ind i rec t , i s tha t i t i s po ten t i a l ly s ens i t ive to bo thc o n s c i o u s l y a n d u n c o n s c i o u s l y p e r c e i v e d i n f o r m a t i o n ( R e i n -go ld & Mer ik le , 1988 , 1990; s ee a l so Re ingold & Toth ,1996) . I f th i s sugges t ion has any m er i t , then wheneverexper im enta l condi t ions a re a r ranged so tha t the s ens i t iv i tyof the d i rec t m easu re i s s ign i f i can t ly reduced , the s ens i t iv i tyo f a n y m e a s u r e a s s u m e d t o a s se s s u n c o n s c i o u s p e r c e p t i o nwi l l a l so be reduced . S uch a s t a te o f a f fa i r s wi l l l ead to as e r i o u s u n d e r e s t i m a t i o n o f t h e i n f l u e n c e o f u n c o n s c i o u sp e r c e p t i o n . I n f a c t , i t m a y e v e n a c c o u n t f o r t h e f i n d i n g sr e p o r t e d b y G r e e n w a l d e t a l . ( 1 9 9 6 ) s h o w i n g t h a t u n c o n -s c i o u s ly p e r c e i v e d i n f o r m a t i o n l a s ts n o l o n g e r t h a n 1 0 0 m s .Given tha t Greenwald e t a l . used the regres s ion s t ra tegy toas ses s s em ant ic p r im ing under expe r im enta l condi t ions tha tm i n i m i z e d t h e s e n s i t iv i t y o f a d i r e c t m e a s u r e o f p e r c e p t i o n ,t h e i r f i n d i n g s a r e n o t u n e x p e c t e d i f t h e d i r e c t m e a s u r e o fp e r c e p t i o n w a s a s e n s i t i v e i n d ic a t o r o f b o t h c o n s c i o u s a n du n c o n s c i o u s p e r c e p t i o n . B y e s t a b l i s h i n g t h e e x p e r i m e n t a lc o n d i t i o n s i n w h i c h t h e d i r e c t m e a s u r e s h o w e d m i n i m a lsens i t iv i ty , they m ay have a l so e s tab l i shed expe r im enta lc o n d i t i o n s i n w h i c h t h e i n d i r e c t m e a s u r e s h o w e d m i n i m a lsens i t ivi ty.O n e o f t h e p r im a r y r e a s o n s t h a t t h e re h a s b e e n s o m u c hi n t er e s t o v e r t h e y e a r s i n d e m o n s t r a t i n g u n c o n s c i o u s p e r c e p -t i o n i n t h e c o m p l e t e a b s e n c e o f c o n s c i o u s p e r c e p t i o n i s t h a ts u c h a d e m o n s t r a t i o n w o u l d b e a c o m p e l l i n g p r o o f o f th ee x i s t e n c e o f u n c o n s c i o u s p e r c e p t i o n . W e d o u b t t h a t i t w i l l b ep o s s i b le e v e r t o p r o v e t h e e x i s t e n c e o f u n c o n s c i o u s p e r c e p -t i o n . T h e d i s t i n c t i o n b e t w e e n c o n s c i o u s a n d u n c o n s c i o u sp r o c e s s e s p r o v i d e s a w a y o f c a t e g o r iz i n g o r t h i n k in g a b o u tc o g n i t i v e p r o c e s s e s t h a t h a s b e e n p a r t o f o u r i n t e l l e c t u a lh i s t o r y f r o m a t l e a s t a t i m e s h o r t l y f o l l o w i n g D e s c a r t e s 'd i s t in c t i o n b e t w e e n t h e b o d y a n d t h e s o u l ( W h y t e , 1 9 6 0 ). I ti s n o t a t a ll c l e a r w h a t t y p e s o f e x p e r i m e n t s w o u l d e v e rprov e or d i sprove the va l id i ty o f th i s concep tua l d i s t inc tion .F or th i s reason , a be t t e r , m o re p rod uc t ive re sea rch s t ra tegy i st o a c c e p t t h e d i s t i n ct i o n b e t w e e n c o n s c i o u s a n d u n c o n s c i o u sc o g n i t i v e p r o c e s s e s a s a w o r k i n g a s s u m p t i o n a n d t h e n t odeve lo p re sea rch s t ra teg ie s based o n th i s a s sum pt ion . In th i s

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310 COM M E NT Sw a y , t h e u s e f u l n e s s o f t h e d i s t i n c t i o n f o r u n d e r s t a n d i n gh u m a n c o g n i t i o n c a n b e a s s e ss e d .

I n r ecen t yea r s , t h i s a l t e r na t i ve r e sea r ch s t r a t egy hasp r o v e n s u c c e s s f u l . F o r e x a m p l e , w e h a v e u s e d t h e r e l a t i v es e n s i ti v i ty a p p r o a c h t o i d e n t i f y s i t u a ti o n s i n w h i c h u n c o n -sc i ous i n f l uences p l ay a s i gn i f i can t r o l e ( M er i k l e & Re i n-g o l d , 1 9 9 1 ) , D e b n e r a n d J a c o b y ( 1 9 9 4 ) h a v e u s e d t h ep r o c e s s - d i s s o c i a t i o n p r o c e d u r e t o e s t i m a t e t h e s e p a r a t ec o n t r i b u t io n s o f c o n s c i o u s a n d u n c o n s c i o u s p e r c e p t u a l p r o -c e s s e s , a n d M e r i k l e , J o o r d e n s , a n d S t o l z ( 1 9 9 5 ) h a v e u s e de s t i m a t e s o f th e r e l a t iv e m a g n i t u d e o f u n c o n s c i o u s p e r c e p -t ua l p r oces ses t o p r ed i c t qua l i t a t i ve d i f f e r ences i n t hec o n s e q u e n c e s o f p e r c e i v e d s t i m u l i . A l t h o u g h n o n e o f th e s ee x p e r i m e n t s n e c e s s a r i ly p r o v e t h e e x i s t e n c e o f u n c o n s c i o u sp e r c e p t i o n , t h e r e s u l t s o f t h e s e e x p e r i m e n t s h a v e p r o v i d e dn e w i n s i g h t s a n d u n d e r s t a n d i n g s r e g a r d i n g h u m a n c o g n i -t io n . T h e s u c c e s s o f t h e s e e x p e r i m e n t s d e m o n s t r a t e s t h ev a l u e o f t h i n k i n g a b o u t c o g n i t i o n i n t e r m s o f t h e d i s t in c t i o nb e t w e e n c o n s c i o u s a n d u n c o n s c i o u s p r o c e s s e s .

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R e c e i v e d A p r i l 25 , 1 9 97R e v i s i o n r e c e i v e d A u g u s t 1 2 , 1 99 7A c c e p t e d A u g u s t 1 2, 1 99 7