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McG i l l Pa in Q ues t ionn a i re , based on ca tegory-sca le~: ve rb a l desc r ip tors , hasb e e n u se d t o q u a n t i f y c l in i ca l p a in a n d t o m e a su r e t h e r e la t i v e e f f i c a c y o fp a i n c o n t r ol m e t h o d s [ 1 7 ] . T h e q u e st i on n a ir e a l s o h a s s h o w n c o ns i d er a b lediagnostic po wer . Different profiles of categorical pain responses ha ve di s -t i n g u is h e d b e t w e e n d i f f e r e n t p a in s y n d r o m e s w i t h 7 7% r e i c h .T h e r e f o r e t h e M c G i lt P a in Q u e s t i o n n a i r e m a y b e a n i m p o r t a n t to 01 fo r t h eq u a n t i f i c a t i o n o f q u a l i t i e s u n i q u e t o sp e c i f i c c h r o n i c p a i n c o n d i t i o n s .H o w e v e r , t h e r e is a l so a n e e d f o r v e r b a l s ca le s w h i c h m e a s u r e d im e n s i o n sc o m m o n t o p ain s y n d ro m e s . S u c h v e rb a l s ca les w o u l d p e r m i t c o m p ~ m n sa m o n g a c u t e , c h r o n i c a n d e x p e r i m e n t a l p a i n r e s p o n s e s , i n f o r m a t i o n g a i n e d~ o m t h e s e c o m p a r i s o n s w o u l d i n c re a s e o u r u n d e r s t a n d i n g o f b o t h p h y s i o -l o g i ca l a n d p sy c h o l o g i c a l m e c h a n i sm s o f p a i n a n d a n a lg e s ia , a~ w e l l a s p r o v i d eu s e f u l m o d e l s f o r t h e e v a l u a t i o n o f n e w p a i n c o n t r o i m e t h o d s . I n a d d i t i o n ,c o m m o n s ca le s o f e x p e r i m e n t a l a n d c l in i ca l p a in a n d d i r e c t m a t c h e s b e t w e e nex pe r im en ta l and c l in i cal pa in can verff~V the c l in i ca l use o f such sca les .T h e m o s t c o m m o n l y u s e d d i m e n s i o n s o f p a i n ar e i ts s e n s o r y a n d af f ec f iv eo r u n p e a sa n t a sp e c t s , a d i s t i n c t i o n w h i c h h a s b e e n e x p r e s se d r e p e a t e d l y i ns t u d i e s o f h u m a n p a i n e x p e r i e n c e . T h e se n so r y a sp e c t s o f p a i n a r e s i m i l ar t ot h o s e o f o t h e r s e n so r y m o d a l i t ie s i n t h a t p a i n s e n sa t i o n s v a r y in i n t e n s i t y ,q u a l i t y , d u r a t i o n a n d l o c u s . T h e a f f e c t iv e a sp e c t s a r e p r e su m a b l y a f u n c t i o no f c o g n i t i v e a n d m o t i v a t i o n a l v a r i a b l e s i n f l u e n c e d b y a b r o a d sp e c t r u m o fp sy c h o l o ~c a l f a c t o r s . H u m a n s t u d i e s su g g e s t t h t i t a n a l g e s i c s a c t b y m o d i -f il in g e i t h e r t h e s e n s o r y o r a f f ec t iv e c o m p o n e n t s [ 2 - - 6 , 8 ] . O t h e r s t u d ie sh a v e s h o ~ n t h a t t h e s e t w o c o m p o n e n t s o f p a in e x p e r i e n c e m a y b e d i st in -g u i sh a b l e a t a p h y s i o l o g i c a l l ev e l. I t h a s b e e n h y p o t h e s i z e d t h a t n e r v e i m -p u l se s r e l a t e d t o p a i n a r e c o n v e y e d , i n p a r t , b y a n e o sp i n o t h a l a m i c sy s t e mc o n c e r n e d w i t h t h e s e n so r y d i sc r im i n a t i v e a sp e c t s o f s e n sa t i o n a n d , i n a d d i .t i o n , t h a t t h e s e n e r v e im p u l s e s c o n v er g e o n c e n t ra l p a t h w a y s k n o w n t o pa r-t i c i p a t e ~n t h e m o t i v a t i o n a l a n d a f f e c t iv e c o m p o n e n t s o f b e h a v i o r [ 1 8 ] .V e r b a l d e s c r i p to r s o f s e n s o r y i n t e n s i t y a n d a f f e c t h a v e b e e n s ca le d ~ yl ~ L a c k a n d T o r g e rs o n [ 1 9 ] a n d T u r s k y [ 2 8 ] . A l t h o u g h s e n s or y i n te n s it yh a s b e e n m e a s u r e d i n t e r m s o f s e n s o r y q u a l i t i e s , t h ~ t e r m is u s e d ~n t h e p r e s -e n t s t u d y t o i n di c a te o n l y m a g n i t u d e o f s e n s a t i o n e .g. , w e a k , r o o d ,s t r o n g ) . T h e ~ ' a f fe c t iv e " l a b e l h a s b e e n a p p l i ed t o e m o t i o n a l a n d m o t iv a 0t i o n a l v a r ia b l es . I t i s u se d h e r e i n a m o t i v a t i o n a l o r h e d o n i c s e n se :to r e f e rt o p a i n " u n p l e a sa n t n e s s " ( e .g . , u n c o m f o r t a b l e , d i s tr e s s in g , i n t o l e r a b l e ) . T h i su sa g e i s si m i la r t o t h e e v a l u a ti v e c a t e g o r y o f M e l z a ck a n d T o r g e r so n E 19 ]a n d t h e r e a c t io n c a t e g o r y o f T u r s k y E 2 8] .

A n a d d i t i o n a l a n d c r i ti c a l n e e d i n p a i n m e a su r e m e n t i s t h e a s se s sm e n t o fr e l i a b i li t y a n d o b j e c t i v i ~ . Re l i a b i li t y e x p r e s se s t h e s i m i l a r it y o r c o n s i s t e n c yo f d e sc r i p t o r u se e i t h e r b e t w e e n o r w i t h i n su b j e c ts . O b j e c t i v i t y i s t h e r e l a ti v ed e g r e e t o w h i c h i n d i v id u a l s u se v e r b a l d e sc r i p t o r s i n a si m i ]a r f a sh i o n . O b j e c -t i v it y is d e f i n e d m a t h e m a t i c a l l y b y c o m p a r i n g t h e r e l ia b iH t y o f - d e s c r i p t o ruse b e t w e e n i n di v id u al s t o t h e r e l i a b ~ W o f d e sc r i pt o r u se withi n individualst 4 ] o O b j e c t h d t y i n c r e a se s a s b e t w e e n r e l i a b i l i ty a p p r o a c h e s w i t h i n r e li a b iLi ty . P r e s e n t v e r b a l p a in m e a s u r e s w h i c h u s e g r o u p n o r m a t i v e s c al e v a l ue s t o

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quan?~ify ~he pain responses of an individual are appropria%e only wi%hA further requiremen% is %he production of valid pain measures by a bias-free scaling procedure. The category me~hods used in many pain measures

t h e sc re of cross-m matching produces relativelybias -free scales: u~ ~ain :~d e ~ t ~ r nr o ther, verbal stimu~. The basics of a. ~ ~ ~. ~ ~---- ~ --cros g procedure involve he adju of a response con-tinuum (e.g., hand grip force, time d~ af io n, loudness, numbers) in relationthe magnitude of a stimulus continuum. If the response is expressed bynumbers, the me~hod-is cal led 'magnitude es tim at ion '. In the simplest cross=modality matching procedure, subjects make an arbitrary response to thefirst stimulus and then respond proportionally to successive stimuli. Theresult of this and more compli cat ed procedures is ratio sthmulus scales(interval scales with a zero} which enable subjects to make meaningfuI ratiostatements about stimulus magnitudes such as, '%his stimulus feels twice asintense as tha t o n e .Although cross,modali~y ma+~chL~g procedures are co mmonly u~d to scalephysically measurable stimuli, the validity of their application to verbalstimuli can be demonstrated by specific functional relationships common tobo~.h types of stimuli. For example, cross-modality matches of two dimen-sions to a third predicts the relation between those two dimensions. ~n addi=~ion, scales derived from direc~ ra~io me~hods such as cross-modali~y match=ing are approximately logarithmically rela~ed %0 scales derived from indirec~;me~hods such as ranking, category rasing, or ~he me~hod of paired compari-sons [21--23].Wi~h these requirements in mind we conducted ~wo experiments in which:(1) subjects scaled sensory and affective verbal pain descriptors by cro~s=modali~y ma~chmg procedures designed %0 bo~h r~uce scaling biase~ and~ : ks of validlY: ~ 21 24 2 each of two groups scaledrovide m~ernal chec . ....y [ , .., ], ( )desc~p~rs in %wo sessions ~o permi~ the compu~a%ion of bo%h within-groupand be%ween-group correta%ions, and w~h'.m-individual and be~ween-individoual corre lations; (~) ~he verbal descrip%0r scales were examined for specificfunc%ional rela%ionships obs e~ ed for physically measurab le s%imu~i.

The da%a from ~he~ exp e~e n% s are per~inen~ ~o ~he following questions.( 1 ) ~s i t v a l i d t o u s e v e r b a l p a i n d e s c r i p ~ r s i n c r o s s o m o d a i i ~ y m a t c h i n g p r o -c e d u r e s c o m m o n l y u s e d t o r a % e p h y s i c ~ / l y m e a s u r a b l e s ~ i m u l i ? ( 2} A r e s c ~ e so f v e r b a l p ~ d e s c r i p t o r s r e l i a b l e ? ( 8 ) A r e Z h e s e s c a l e s o b j e c i v e ? ~ s ad e s c r i p t o r s c a l e d e r i v e d f r o m n i n d i v i d u a l b e t t e r p r e d i c t e d b y a n o % h e r s c a lef r o m ~ h a ~ i n d i v i d u a l o r b y a m e a n s c a l e d e r i v e d f r o m a g r o u p ?

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M E T H O S

x p e r i m e n tT h e s u ld i a n , 2 3 ) ,

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r e c o r d e d b y a d i g it al s a m p l e a n d h o l d c ~ c u i t w i t h a r e s o l u ~ o n o f 0 ~ 05 k g ,S ~ im u li w e r e r e a r p r o j e c t e d u p o n a 3 7 c m 3 8 c m t r a n s lu c e n s c re e n b y aK o d a k m o d e l 9 6 0 r a n d o m a cc es s p r o j e ct o r .T h e s u b j e c t s w e r e r a n d o m l y a s si gn e d ~ o g r o u p s A a n d B w ~ th 4 m e n a n d4 w o m e n i n e a c h g r o u p . T h e g r o u p s d~ d n o t d i f fe r in e x p e ~ e n ~ a l tr ea ~-men~s . E ach sub jec t pa r t i c ipa te d ~n ~w~ ~-h sess ions sep a ra te d by 1 week .T h e s u b j e c F s t a s k w a s t o e v a lu a te t h e l e n g t h s o f l in e s a n d t h e m ~ n R u d e so f s e n s o r y a n d a f f e c f i v e d e s c r i p t o r s b y m e a n s o f b o ~ h n u m e r i c ~ m ~ i ~ u d ee s t i m a t i o n a n d c r os s -m o d a l i~ y m a t c h i n g '~,o h a n d ~ p f o r c e , B o t h s f i m ~ u sa n d r e s p o n s e o r d e rs w e r e c o u n t e r b a l a n c e ~ ~ n a n e x p e r ~ e n t A s es sio n ~ hee x p e r i m e n t e r f i r st e x p l a i n e d ~h e d i s f i n c t i~n b e t w e e n a ff ec t~v e a n d se n so wc o m p o n e n t s o f p a n . T h e e x p er im e n t e r t h e n d e , A b e d ~he p r o c ~ u r e s f o rm a g n i t u d e e s t im a t i o n a n d c r o s s - m o d a l~ y m a ~ h h ~ g ~o h a n d ~ p f o rc e , T h esu b j e c t s m a d e a n u m e r i c a l o r h a n d g r i p r e sp o n se t o ~he firs~ s t i m u l u s , a n dt h e n r e s p o n d e d ~ o s u b s e q u e n t s t im u l i w ~ h n um be~ rs o r g a p s i n p r o p o r t i o nto ~he i r f i r s t r e sponse .

xper imen t HT h e s u bj ec ts w e r e 2 0 m e n a nd 2 0 w ~ m e n , 2 3 )~ T h e

7 l ine s o f v iab le 1 e r iCh . L ine s t imi wo d t in l i ere ch ged t oa r e s h o w n i n T a b l e I V . E a c h

s u re d o n a L a f a y e t t e m o d e l 6 3 3 1 4 d i ~ ; ~ r e a c t i o nu p o n a te le g r ap h k e y a c t u a t e d a m i n is e co n d ~ im er a n d : ~ a u d i ~ c u e ; I na s in g l e l h s e s s io n e a c h su b j e c t r a n k .o r ~e r e d t h e a f f e c t i v e : ~ d se n so r yd e s c r i p t o r s a n d s c al ed t h e 3 s t i m u l u s s e r ie s ( af f e ct iv e d e s c r i p t o r s , s e n s o ~d e s cA p t o rs ~ l in e s) b y c r o s s o m o d ~ i t y m a t c h i n g t o t i m e d u r a t i o n a n d :t o h a n d .g ri p f o r c e . E a c h s~ ;im ulu s s eA e s w ~ p r e s e n t e d s e p a r a t e ly , w i t h e a c h s t h n ~ u sp r e s e n t e d t w i c e ~n r a n d o m o r d e r . S ~ i m u lu s o r d e r a n d r e s p o n s e o r d e r w e r ec o u n t e r b a l a n c e d , a l~ h o u g h t i n e ~ fim u li c o n s i s t e n t ly p r e c e d e d v e r b ~ s ~ m u l iso th a ~ t h e i n e ~ p e f f e n c e d su b j e c t s c o u l d m a k e Sh e ~ne j u d g m e n t s b e f o r e ~ h em o r e d f f fi c ul ~ w o r d j u d g m e n t s

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R S U L T S

Ex pe r ime n I

r ~ p : T h e o f o n (r ) ~ n i n de x o f t hegoodne ss of fit of the po we r functions by sh ow /n g the proportion of va~:~oability m the log responses that is acc oun ted for b y the vEiabflity in the

s intensity. The se coefficients we re 0.9 9 a nd 0.98 for mag nitu deestimation and for h a n d ~ p force. Since verbal descriptors have no metrico f th o w n , p o w e r f u n c t i o n s c o u ld n o t b e d e t e r m i n ed f or t he m e a nresponses to each word. How eve r, the expo nen t for the po we r function relat-ing handgrip responses to m agn itu de estimation response s for each verbalstimulus wa s This e nt co nf ir me d the expected non-linear relationbe tw ee n these tw o response motilities. In order to co mp az e these response.measures, they were first -ran to a c o m m o n reference continuumLine length was chosen as the reference con ti nu um because judgme nts ofline length are roughly proporti ons/to actual line length [25,2 7] Th e geo-metric m e a n magni tude estimate and hm%dgr~p response to each verbed stim-ulus we re tran sfor med to relative ma gn it ud e (line lengthsl. ']'his as ac co mpu sh ed by relating the values of the descriptors det enn h~e d by the particularresponse (numerical estimate or ha nd g~ p squeeze) to the v~ ue s of the linesdetermined by the sam e response measure.Algebraically:

:ived from m~itude' derived ~om cros~oit~c mean m~itudeip force for word '~i';re =p ow er mnc~lon : or m~m~dde estimates of linefor cross-modality matches of h and ~ip

f o r c e in terms of line stimu h b y a response meas urei%e~ession b : ~" observed to occur inP s y o h o p h y s i c ~ r e ~ s ~ : o : b : ~ :~ a

p o w e r function exponents Theore%o: ~ ~ r y a : ~ s i o n s : o ~a n e: s a n d b r: et 'h es s, t h e n e a t p o w e r r e: a tm g A a s a r e s p o n ~ t ~ ~ a ss t : m U : ~ s s h o u l d e t h e ~ h e p o w e r f u n c h o n e x p o ~ n ~ r e :a ~ i :g ~

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' ~ ~ ~ i~ , ~ ~ ~ i ~ / ~ / ~ i ~/ i iili~ i~i~/~i~i~i:,~i~/:/i ~i~/i~i //~/~ i~ ~ ~i~i~ ~ ~i~i~ ~i~i~i~; ~i~ ~ ~i~ ii~a r e s p o n s e t o A ~ a s t ~ n u l u s ; ~ n p r aC t ic e, s u b j e c ts ~ e s t : ~ ~ / :t h e c o n t i n u u m t h e y s 0 t h a~ t h :e e b ~a ifi~n e n t ~ s l e s s t h a n t h e e x p e e ~ d e x p o n e n t : 5 n e w a y i n :w h i c h th i~ b ~ /r e d u c e d o r e l i m i n a t e d ~ s b y a d j u s t i n g a

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p r es ea ~ e x p e r i m e n t : i m d e :a~for b o~ h w o ~ d ~ d ::line: timulL T bt ~ nu u m a n d b y a d j u s t i n g a c o r nverbs] s~irnu]~ h e respons es ~ t]

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F~g. ~_. Comparison s o f sensory" de sc riptor re]af,~ve ma gnitude s derive d fro m cross-modalo~ty rna~ch~ng ~o hand.grip force and fro m magn~f, de esthnaL ]on proc edures . Log re a~Jvem a g n i t u d e d e r i v e d f r o m r n a g n ~ u d e e sL ~ m a ~o n ~ s r e a ~ iv em a g n i t u d e d e r i v e d f r o m c r o s s - m o d a ~ y m a ~ c h ~ n g ~ o ha~ dgr~ p fo rc~ ; ~spre~ nLed , : :on ~ heo r d i n a t e . E a c h p o i n t ~s ~ he g e o m e t r i c m e a n o f ; 2 8 r e s p 0 n ~ ~o:,a s :ng~e s ens o ry d P ito t . T he s ~ ra ]gh t ]ne ~ n ~ h~s an d s ub s eq uen t f igu res W ~ f i~ ~ o : th e i o~ s ~ "b y~ the mb th :~ do f l e a s ~ s q ~ a r e s , t h e m e a n o f ~ h e ~ w o r n a g n ~ L u d e s f o r e a c h d e s c r i ~ o r ~ s s h o w f i : o n : : ~ h er igh t ve r t i ca l &~So

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