Music Perception and Octave Generalization in Rhesus Monkeys - Wright Et Al 2000

8/3/2019 Music Perception and Octave Generalization in Rhesus Monkeys - Wright Et Al 2000

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Jota'nal of Experimental Psychology: General Copyright 2000 by the American Psychological Association, Inc.2000, Vol. 129, No. 3, 291-307 0096-3445/00/$5.00 IX) I: 10.10371/0096-3445.129.3.291

M usic Percept ion and Octave Genera l iza t ion in Rhesus M onkeysAnthony A. Wright and Jacquelyne J. Rivera

U n i v e r s i t y o f T e x a s M e d i c a l S c h o o l a t H o u s t o nStewart H. Hulse

J o h n s H o p k i n s U n i v e r s i t yMelissa ShyanB u f f e r U n i v e r s i t y J u l i e J . N e i w o r t hC a r l e t o n C o l l e g e

Tw o rhesus monkeys were tested for octave generalization in 8 experiments by Wansposing6- and 7-notemusical passages by an octave and requiting same or d i f f e r e n t judgments. The monkeys showed nooctave generalization to random-synthetic melodies, atonal melodies, or individual notes. They did showcomplete octave generalization to childhood songs (e.g., "Happy Birthday") and tonal melodies (from atonality algorithm). Octave generalization was equally strong for 2 -octave transpositions but not for 0.5-or 1.5-octave transpositions of childhood songs. These results com bine to show that tonal melodies formmusical gestalts for monkeys, as they do for humans, and retain their identity when transposed withwhole octaves so that chrom a (key) is preserved. This conclusion implicates similar transduction, storage,processing, and relational mem ory of musical passages in m onkeys and hum ans and has implications fornature-mLrm re origins of m usic perception.

M u s i c i s c o n s i d e r e d a m o n g c u l t u r e s ' h i g h e s t a c h i e v e m e n t s .N e v e r t h e l e s s , m u s i c f r o m d i f f e r e n t c u l t u r e s s h a r e s m a n y c h a r a c -t e r i s t i c s . A m o n g t h e s e c o m m o n c h a r a c t e r i s t i c s i s t h a t a l l m u s i cu s e s a l i m i t e d n u m b e r o f p o s s i b le n o t e s. A l i m i t e d n u m b e r o fp o s s i b l e n o t e s h e lp s t o m a k e s o n g s m e m o r a b l e a n d r e p r o d u c i bl e .O t h e r f a c t o r s c o n t r i b u t e t o t h e i r m e m o r a b i l i t y , r e p r o d u c i b i l i t y , a n dg e n e r a l a p p e a l. T a k e , f o r e x a m p l e , t h e f a m i l i a r t u n e " H a p p y B i r t h -d a y . " T h e r e i s n o d o u b t a b o u t i t s m e m o r a b i l it y . T h e f i r s t f o u r n o t e sr e a d i l y i d e n t i f y i t . F u r t h e r m o r e , d i f f e r e n t s e t s o f f o u r n o t e s s e p a -r a t e d b y w h o l e o c t a v e s s u f f i c e e q u a l l y w e l l t o i d e n t i f y " H a p p yB i r t h d a y . "

P r e v e r b a l i n f a n t s a s w e l l a s a d u l t s c a n i d e n t i f y a t r a n s p o s e dm e l o d y a s t h e s a m e m e l o d y w h i l e a t t h e s a m e t i m e r e c o g n i z i n gt h a t t h e n o t e s a r e d i f f e r e n t , t h a t i s , d i f f e r e n t p i t c h h e i g h t s ( e . g . ,D e m a n y & A r m a n d , 1 9 8 4 , P i c k & P a l m e r , 1 9 9 3 , p . 1 9 9 ; T r e h u b ,M o r r o n g i e l l o , & T h o r p e , 1 9 8 5) . T h u s , th e m e l o d y b e c o m e s aw h o l e o r g e s t a lt u n t o i t s e lf , s o m e w h a t i n d e p e n d e n t o f t h e n o t e su s e d t o p r o d u c e i t .

Antho ny A. Wright an d Jacquelyne J. Rivera, Department o f Neurobi-ology and Anatomy, University of Texas Medical School at Houston;Stewart H. Hulse, Department of Psychology, Johns Hopkins University;Melissa Shyan, Department of Psychology, Buffer University; Julie J.Neiworth, Department of Psychology, Carleton College.This research was partially supported by National Institutes of HealthGrants MH-35202 a nd DA-10715 an d National Science Foundation G rantIBN 9317868.We gratefully acknowledge the assistance of A nnie Takeuchi in analysisof the childhood song and synthetic melodies and supplying the tona l andatonal melodies for Experiments 7 and 8. We also thank Jim Bartlett andJeffrey Katz for their careful a nd thoughtful suggestions on earlier drafts ofthis article.Correspondence concerning this article should be addressed to Anthon yA. Wright, University of Texas Medical School at Houston, Department o fNeurobiology and Anatomy, PO Box 20708, Houston, Texas 77225. Elec-tronic mail may be sent to [email protected].

A m o n g c r i ti c a l v a r ia b l e s i n t h e r e c o g n i t i o n o f m e l o d i e s a r ec o n t o u r ( t he p a t t e r n o f u p a n d d o w n c h a n g e s i n p i t ch ) , i n t e r v a l( s e q u e n c e o f p i t c h d i s t a n c e s i n s e m i t o n e s ) , a n d c h r o m a ( k e y ; e . g .,D o w l i n g & H o l l o m b e , 1 9 7 7) . A l l t h r e e o f t h e s e v a r i a b le s c o n t r i b -u t e t o m e l o d y p e r c e p t i o n a n d c a n c h a n g e i t i n c o m p l e x w a y s .W h e n a l l t h r e e v a r i a b l e s a r e c o n t r o l l e d , t h e r e i s a l m o s t n o d e c r e -m e n t i n m e l o d y i d e n t i f i c a ti o n , e v e n n o v e l m e l o d i e s ( e .g . , M a s s a r o ,K a l l a m , & K e l l y , 1 9 8 0 ) . F o r e x a m p l e , a 2 - o c t a v e c h a n g e i n t h em e l o d y w h e r e a s t a r t in g n o t e o f C a t 2 6 2 H z i s c h a n g e d t o a Ca t 1 , 0 4 8 H z p r e s e r v e s t h e o r i g i n a l m e l o d y a l m o s t p e rf e c f fy . T h ei m p o r t a n c e o f t h i s " o c t av e " e f f e c t c a n b e d e m o n s t r a t e d b y c o m -p a r i n g c h a n g e s t h a t a r e o t h e r t h a n w h o l e o c t a v e s . F o r e x a m p i e ,c h a n g i n g t h e s t a rt i n g n o t e ( a n d m e l o d y ) f r o m a C a t 2 6 2 H z t o a nF # a t 3 7 0 H z i s a m u c h s m a l l e r f r e q u e n c y c h a n g e . H o w e v e r , t h i sm u c h s m a l l e r f r e q u e n c y c h a n g e h a s a m u c h g r e a t e r e f f ec t o nc h a n g i n g t h e m e l o d y f r o m i t s o r ig i n a l . T h e o c t a v e s c a l e i s b a s e d o nf r e q u e n c y d o u b l i n g a n d i s f u n d a m e n t a l to m u s i c p e r c e p t i o n a n dt h e a u d i t o r y s y s t e m g e n e r a l l y (e . g ., D o w l i n g & H a r w o o d , 1 9 8 6 ) .T h i s s p e c i a l s t a t u s o f t h e s i m i l a r i t y o f o c t a v e - t r a n s p o s e d n o t e s c a nb e m o d e l e d a s a t h r e e - d i m e n s i o n a l h e l i x o f a s c e n d i n g p i t c h w h e r en o t e s o f t h e s a m e k e y ( e . g . , C ) a r e v e r t i c a l l y a l i g n e d a n d a r e t h u si n c l o s e p r o x i m i t y ( S h e p a r d , 1 9 8 2 ) . I n t h e p r e s e n t a r t i c le , t e s ts w i t hf r e q u e n c i e s d o u b l e d , h a l v e d , o r h i g h e r m u l t i p l e s o f t w o a r e r e -f e r r e d t o a s o c t a v e - g e n e r a l i z a t i o n te s t s .O c t a v e g e n e r a l i z a t i o n i s a s p e c i a l c a s e o f c o n t o u r t r a n s p o s i t i o n ,w h e r e , i n a d d i t i o n t o c o n t o u r , i n t e r v a l s ( s e q u e n c e o f p i t c h d i s -t a n c e s ) a n d c h r o m a a r e a l s o p r e s e r v e d . A n o c t a v e - g e n e r a l i z e dm e l o d y c a n s o u n d s o s i m i l a r t o t h e o r i g i n a l , p a r t i c u l a r l y a f t e r at i m e d e l a y , t h a t t h e c h a n g e m a y n o t e v e n b e n o t i ce d . T h i s i s n o t t os a y t h a t n o t e s o f t h e s a m e k e y f r o m d i f f e r e n t o c t a v e s a r e i n d i s t i n -g u i s h a b le . N o t o n l y i s t h e p i t c h c h a n g e n o t i c e a b l e w h e n m e l o d i e sf r o m d i f f er e n t o c ta v e s a r e p l a y e d i n r a p i d s u c c e s si o n , b u t ( r a n d o m )n o t e s u b s t i t u t i o n s f r o m d i f f e r e n t o c t a v e s d e s t r o y t h e m e l o d y( D e u t s c h , 1 9 7 2 ; D o w l i n g & H o l l o m b e , 1 9 7 7 ) . T h u s , a m e l o d y c a nb e s h i f t e d a l l o v e r t h e m u s i c s c a l e a n d s t i l l r e t a i n i t s g e s t a l t

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29 2 WRIOHT, RIVERA, HULSE, SHYAN, AND NEIWORTH(melody) qualities. But substitutions from different octaves, evennotes with the same letter name (same chroma), tend to destroy thegestalt.

The purpose of the studies presented in this article was toexplore the possibility that some an imal species might perceivemusic in the same gestalt-preserving way that humans do. Whenthese studies began, there was little encouragement to be found forthis possibility. Most human researchers have tended to regardmusic perception as a human experience. The small amount ofanimal research on this topic has done little to dispel this notion.Monkeys failed octave-genera lization tests (e.g., D'Amato, 1988;D'Amato & Salmon, 1984), and so did songbirds (e.g., Cynx,1993; Dooling, Brown, Park, Okanoya, & So/i, 1987; Hulse &Cynx, 1985, 1986). In a review, D'Amato (1988) concluded that"monkeys can't hum a tu ne .. . Because they don't hear them" (p.478). And this deficiency "may be widespread among animals"(p. 453).

Furthermore, two widely referenced claims of octave generali-zation in animals do not stand scientific scrutiny. A claim of octavegeneralization in the white rat was based on one point for one testfrequency displaced from one generalization gradient for one train-ing frequency (Blackwell & Schlosberg, 1943). Many more testswith other training and test frequencies would be necessary for thisto be a definitive test of octave generalization today. A claim wasmade for octave generalization n the bottlenosed dolphin (Ralston,Herman, Will iams, Gory, & Jerger, 1988). It is difficult to tell thebasis for this cla im because it appeared only as a meet ing abstract.This laboratory had previously shown that dolphins would spon-taneously mimic computer generated sounds and would occasion-ally transpose their mimics by an octave (Richards, Wolz, &Herman, 1984). It is unclear how these two references are relatedwithout more information. Experimental control of such sponta-neous octave shifts undoubtedly would be difficult, and maybe thisis the reason why these intriguing preliminary results were notfollowed up. In any case, when the research of this article began,there were several failures, few positive indications, and no defin-itive evidence in support of octave generalization in nonhumananimals.

Dauntless, we reasoned that contour and octave generalizationshould depend on relat ing two musical passages. Relational learn-ing, in this case, means that the subject relates the two musicalpassages and has learned the same-di f f erent concept. Conceptlearning is assessed by testing with nove l stimuli. If the concepthas been learned, then accurate same-di f f erent judgments shouldbe made to any pair of sounds or music, whether they be familiaror novel. Furthermore, training and testing should be conducted ina musical context. A musical context means that judgments shouldbe based on a sequence of notes, that is, a melody, not individua lnotes or sine-wave tones. Simply training with melodies instead ofnotes does not always ensure that judgments will be based on thewhole melody. Individua l notes of a melody can come to controlthe behavior. Such a result becomes most likely when only a fewmelodies are used in training and when absolute identification of aparticular melody is required (e.g., go/no-go tasks) rather than arelationship between melodies. Go/no-go tasks typically have asingle S + stimulus in which responses are rewarded. In a study byD'Ama to and Salmon (1984), for example, only certain notes, notthe whole tune, were shown to control the go/no-go discriminationof monkeys.

With these requirements of relational concept learning and amusical context, two relations emerge. The fLrSt relation is amongthe notes the melody. The other relation is between melo die s--the same-di f f erent judgment . Therefore, the task might be thoughtof as a relation between relations or analogical-reasoning task(e.g., Gil lan, Premack, & Woodruff, 1981). Unfor tunately for theprognosis of these experiments, only language-trained chimpan-zees and humans are thought capable of learning analogical-reasoning tasks (Premack, 1983a, 1983b). Such a task might be-come simplified if the notes configure together as gestalts(melodies). Simplifying the analogical-reasoning ask by resolvingthe relationship among notes into a gestalt (melody) might allowspecies less sophisticated than language-trained chimpanzees tolearn such a task.

For a variety of reasons, rhesus monkeys were used in thesestudies, not the least of which was that rhesus monkeys learnrelationships among visual stimuli more readily than do someother species such as pigeons (Wright, Cook, & KendricL 1989;Wright, Santiago, Sands, & Urcuioli , 1984). Despite their relativepredisposition for learning visual relationships, researchers had nothad much success in tr aining rhesus monkeys in auditory relationaltasks (Mishkin, personal communicat ion; Thompson, 1980). Nev-ertheless, after several task modificat ions, including the require-ment that monkeys touch the speakers (sound sources), two rhesusmonkeys eventually did learn an auditory same-d i f f erent task.

In this auditory same-di f f erent task, the sample (first) soundwas presented from a center speaker. A second sound was thenpresented simultaneously from two side speakers. If this secondsound matched the In-st sound, then a touch to the fight-handspeaker was required to obtain reward. If the second sound wasdifferent from the first sound, then a touch to the left-hand speakerwas required to obtain reward. A fading procedure was used in theearly training stages of this task. Initially, the second sound cameonly from the correct side speaker. The intensity of second soundfrom the incorrect side speaker was gradually increased in inten-sity until both speakers were equal. Natural (e.g., coyote howl) andenvironmental (e.g., car crash) sounds were used in the orig inaltraining and testing and in maintaining accurate performance onthis task in the experiments of this article.

The monkeys' relational learning in this same-di f f erent taskwas shown by their abstract concept learning; they performed aswell with nove l stimuli as with t raining stimuli (Wright, Shyan, &Jitsumori, 1990). The experiments presented in this article capi-talized on the monkeys' auditory same-di f f erent concept learningas the basis for testing music perception and octave generalization.The order in which the experiments are presented is the order inwhich they were conducted.

Experiment 1The purpose of Experiment 1 was to test contour transpositions

of "synthetic" melodies in a same-di f f erent task with monkeys.These melodies were essentially a random collection of noteswithin a restricted frequency range. Music training began bygradually introducing music trials while maintain ing accurate per-formance with natural/environmental ound stimuli. Stable perfor-mance with natural sounds assured a stable baseline and main-tained the same-di f f erent concept. As was done in train ing withnatural sounds, melody training was conducted with a large hum-


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M O N K E Y O C T A V E G E N E R A I J7 . A TI O N A N D M U S I C P E R C E P T IO N 2 9 3h e r o f s y n t h e t i c m e l o d i e s p l a y e d b y d i f f e r e n t m u s i c a l i n s t r u m e n t s .L a r g e n u m b e r s o f s t im u l i , w h i c h c o n t i n u o u s l y v a r y , p r o m o t e re -l a t io n a l l e a r n i n g a n d c o n c e p t l e a r n i n g ( e . g ., H o m a , C r o s s , C o r n e l l ,G o l d m a n , & S h w a r t z , 1 9 7 3 ; H o m a & V o s b u r g h , 1 9 7 6 ; W r i g h t ,C o o k , R i v e r a , S a n d s , & D e l i u s , 1 9 8 8 ) .

M e t h o dS u b j e c t s

T h e s u b j e c t s w e r e t w o m a l e r h e s u s m o n k e y s (Macaca mulat ta) . B Ww a s 1 2 y e a rs o l d a n d F D w a s 1 3 y e a rs o l d a t t h e b e g i n n i n g o f t h ee x p e r i m e n t . T h e m o n k e y s h a d e x t e n s i v e tr a i n in g w i t h n a t u r a l/ e n v i ro n m e n -t a l so u n d s p r i o r t o t h e se e x p e r i m e n t s ( Wr i g h t e t a l . , 1 9 9 0 ),

T h e m o n k e y s w e r e m a i n t a i n e d i n s t a te a n d f e d e r al l y a p p r o v e d f a c i li t ie s .B o t h m o n k e y s w e r e g i v e n a m p l e a c c e s s t o f o o d a n d w a t e r a p p r o x im a t e l y 2h o u r s a f t e r th e i r e x p e r im e n t a l s e s s io n s . T e s ti n g w a s c o n d u c t e d 5 - 6 d a y sp e r w e e k . O n d a y s w h e n t h e y d i d n o t p a r t i c ip a t e i n e x p e r i m e n t a l s e s s i o n s,t h e y w e r e g i v e n u n r e s t r i c t e d a c c e s s t o f o o d a n d w a t e r , a n d t h e i r d i e t w a ss u p p l e m e n t e d w i t h f r e s h f r u it .

I 1

SAMP LE PRESENTATIONA p p a r a t u s

A s c h e m a t i c o f t h e a p p a r a tu s i s s h o w n i n F i g u r e 1 . A m o n k e y c a g e w a sm o d i f i e d , in c l u d i n g r e m o v i n g a b a r f r o m e a c h o f t h r e e w a l l s . S p e a k e r sw e r e p o s i t i o n e d o u t s i d e th e c a g e w h e r e t h e b a r s h a d b e e n r e m o v e d . T h em o n k e y s t o u c h e d c o p p e r s c r e e n s i n f r o n t o f e a c h s p e a k er . A c o m p u t e rm o n i t o r e d t o u c h e s ( v i a h i g h - i m p e d a n c e CIV I O S c i r c u i t s) , c o n t r o l l e d s e s -s i o n s , c o l l e c t e d d a t a , a n d se q u e n c e d s t i m u l i . T h e s t i m u l i t h e m se l v e s w e r ed i g i t i z e d a n d s t o r e d i n a s e c o n d c o m p u t e r ( s e e Wr i g h t e t a l ., 1 9 9 0 , f o ra d d i t i o n a l d e t a i l s ).

Ba n a n a p e l l e t s (1 g r a m ) w e r e d i sp e n se d i n t o a c u p i n s i d e t h e c a g e b e l o wt h e c e n t e r sp e a k e r . T a n g o r a n g e d r i n k ( 3 . 5 c c ) w a s d i sp e n se d a d j a c e n t t ot h e s i d e s p e a k e r s , o n t h e r i g h t s i d e o f t h e r i g h t s p e a k e r a n d o n t h e l e f t s id eo f t h e l e f t sp e a k e r .

P r o c e d u r eO n e a c h t r ia l , a f l a sh i n g l i g h t ( d i m g r e e n L E D w i t h a w h i t e p l a s t i c

a l l i g a t o r -c l i p c o v e r ) b e h i n d t h e c e n t e r - sp e a k e r c o p p e r s c r e e n i n d i c a t e d t h a ta t r ia l c o u l d b e g i n . A t o u c h t o t h e c e n t e r sp e a k e r ( c o p p e r s c r e e n ) p r o d u c e da b a n a n a p e l l e t a n d b e g a n p l a y i n g t h e f i r s t s o u n d o r s a m p l e . M o s t U i a l sc o n t a i n e d n a t u r a l o r e n v i r o n m e n t a l so u n d s l i k e t h o se u se d i n t h e o r i g i n a lt r a i n i n g a n d c o n c e p t t e s t i n g o f t h e m o n k e y s . O n se v e r a l t r i a l s i n t h ee x p e r i m e n t s r e p o r t e d i n t h i s a r t i c l e m u s i c s t i m u l i w e r e p r e se n t e d f o rt r a i n i n g o r t e s t i n g . T h e s t i m u l i a r e d e sc r i b e d m o r e t h o r o u g h l y i n t h e n e x tse c t i o n . Bo t h s t i m u l i o n a t r i a l w e r e e i t h e r n a t u r a l / e n v i r o n m e n t a l s t i m u l i o rm u s i c s t i m u l i, n e v e r a m i x t u r e o f t h e t w o t y p e s .

T h e s a m p l e s o u n d w a s p l a y e d f o r 3 s f r o m t h e c e n t e r s p e a k er . F o l l o w i n gt h e s a m p l e , th e r e w a s a 1 - s d e l a y a n d t h e n a s e c o n d o r t e s t s o u n d w a sp l a y e d . T h e t e s t s o u n d w a s p l a y e d s i m u l t a n e o u s l y f ro m b o t h s i d e s p e a k e r sf o r 2 - 6 s . C h o i c e r e s p o n s e s w e r e a c c e p te d a f te r 2 s o f t h e s e c o n d s o u n d .T h e t e s t s o u n d w a s a r e p e a t o f t h e s a m p l e s o u n d o n h a l f t h e tr ia l s, a n d t h em o n k e y w a s r e q u i r e d t o t o u c h t h e r i g h t -s i d e s p e a k e r to o b t a i n j u i c e r e w a r d .O n t h e o t h e r h a l f o f t h e t r ia l s, t h e r e w e r e t w o d i f f e re n t s o u n d s . O n t h e s et r i a l s , t h e t e s t s o u n d d i d n o t m a t c h t h e s a m p l e , a n d t h e m o n k e y w a sr e q u i r e d t o t o u c h t h e l e f t - s i d e sp e a k e r t o o b t a i n j u i c e r e w a r d . A s i d e -s p e a k e r ( c h o i c e ) r e s p o n s e w i t h i n t h e 2 - 6 - s r e s p o n s e i n t e rv a l t e r m i n a t e d t h et e s t s o u n d . I n c o r r e ct c h o i c e s o r a b o r t s ( n o t r e s p o n d i n g w i t h i n t h e 2 - 6 - si n t er v a l o f t e s t so u n d ) w e r e n o t r e w a r d e d a n d w e r e f o l l o w e d b y a 3 0 - st i m e - o u t . A 1 2 - s i n t e rt r i a l i n t e r v a l f o l l o w e d c o r r e c t c h o i c e s o r t i m e - o u t s .T h e r e w a s n o c o r r e c t i o n p r o c e d u r e ( e . g ., r e p e t i ti o n o f i n c o r r e c t tr i a ls ) .

T h e r e w e r e 3 0 t r i a l s i n a d a i l y s e s s i o n a n d 1 5 d a i l y s e s s i o n s i n t h ee x p e r i m e n t . I n a d a i l y s e s s i o n , t h e r e w e r e 2 4 t r a i n i n g t r i a l s w i t h n a t u r a l /

TEST PRESENTATION

F i gur e I . S c h e m a t i c o f t e s t p r o c e d u r e. U p p e r p a n e l s h o w s t o p v i e w o f am o n k e y w i t h s a m p l e s o u n d being p r e s e n t e d f r o m a c e n t e r s p ea k e r . L o w e rp a n e l s h o w s t o p v i e w o f a m o n k e y t o u c h i n g a f i g h t s i d e s p e a k e r w i t h a t e s ts o u n d b e i n g p r e s e n t e d f r o m b o t h s i d e s p e a k e r s . A t o u c h t o t h e r i g h ts i d e - s p e ak e r w a s c o r r e c t w h e n t h e t e s t s o u n d m a t c h e d t h e s a m p l e s o u n d ,a n d t o t h e l e f t w h e n i t d i d n o t m a t c h t h e s a m p l e s o u n d .

e n v i r o n m e n t a l so u n d s , t w o t r a i n i n g t r i a l s w i t h m e l o d i e s , a n d f o u r t e s t t r ia l sw i t h m e l o d i e s . Fo r t h e t w o t r a i n i n g t r i a l s w i t h m e l o d i e s , o n e w a s a s a m et r ia l w h e r e t h e s a m e m e l o d y w i t h t h e s a m e f r e q u e n c i e s w a s r e p e a t ed a n da s a m e r e s p o n s e w a s r e w a r d e d . T h e o t h e r m e l o d y t r a i n i n g t r i a l w a s adif ferent trial w h e r e d i f f e re n t m e l o d i e s w i t h d i f f e r e n t f r e q u e n c ie s w e r ep r e se n t e d , a n d a di f f erent r e s p o n s e w a s r e w a r d e d . I n o t h e r w o r d s , o n s a m et r i a l s t h e c o n t o u r s , i n t e r v a l s , a n d f r e q u e n c i e s o f t h e t w o m e l o d i e s w e r ei d e n t i c a l , w h e r e a s o n dif fere nt trials the c o n t o u r s , i n t e r v a l s , a n d f r e q u e n c i e sw e r e d i f f e r en t . T h e m e l o d i e s w e r e s e l e c te d q u a s i r a n d o m l y d a i l y a n d w e r ec o u n t e r b a la n c e d w i t h i n t h e l i m i ts o f t h e e x p e r i m e n t .


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294 WRIGHT, RIVER.A, HULSE, SHYAN, AND NEIWORTHThe four melody test trials differed from the two melody training trials

in that either the melody or frequency was different between the twomusical passages on a trial. On two test trials, the melody was the same butthe frequency was different. These trials are referred to as Same-Melody,Different-Frequency (SAME-TUNE DIFF-FREQ) and are the transposi-tion tests o f primary interest in this experiment.

On the other two test trials, the melodies were different but the frequen-cies were the same. These trials are referred to as Different-Melody,Same-Frequency (DIFF-TUNE SAME-FREQ) trials. These test trials arecontrol tests for frequency differences, as opposed to melody differences.In this experiment, the two melodies were the same six notes scrambled sothat the order of notes in the two musical passages was different on thesetrials.

Test trials in these experiments were perceptual tests. Therefore, noparticular response could be defined as correct and rewarded without"training" the behavior to be tested. Thus, on these test trials eitherresponse was rewarded. The alternative would have been to reward noresponse (extinction). The problem with extinction is that monkeys willlearn that test trials are a cue for extinction, and performance on these trialswill deteriorate. By rewarding either response, it is more likely that thesubjec t's initial response tendencies will continue to be maintained.St imul i . There were 520 natural/environmental sounds (ElektraRecords, NY, NY) used in these experiments (e.g., boat whistle, jackhammer, dive klaxun, owl hoots, turkey gobbles, pig grunts, free alarm,baby crying, woman laughs, cable car, squeaky door, busy signal, dentistdrill, bell buoy, sonar pings, stagecoach passing, water pouring, fog horn,man snoring, anchor chain, ping pong, coyote howls, etc.). From the 520pool of natural/environmental sounds, 36 sounds were used daily, and eachsound was presented on only one trial (trial unique). Representation of anyindividual sound was separated by several days of testing. Pairing ofsounds, sequences of s ame -d i f f e r e n t trials, and placement of test trialsvaried quasirandomiy from day to day.

The random-synthetic melodies were six note sequences generated froma computer linked to a Yamaha DX7 synthesizer. Notes and intemoteintervals were 80 ms. Melodies were repeated (with a 500-ms separation)to provide appropriate sample and test stimulus durations. The test duration(side speakers) depended on when in the 2- 6-s response time the subjectmade its choice response. Each melody used in the experiment wasrecorded by 10 different keyboard instruments (Flute, Accordion, Spanish

Guitar, Oboe, Electric Piano, Bag Pipe, Clarinet, Grand Piano, Honky-Tonk Piano, and Glockenspiel). All notes of a melody and both melodiesof a trial were played by the same insmunent. The six notes of each melodywere quasirandomly selected with the restriction that they be located withina 12-semitone range. There were 48 possible semitones that the notes couldrepresent, covering a four-octave range from 131 Hz (C) to 1,976 (B) Hz.Some melodies contained repeating notes. The particular renditions (wheninstrument and octave were considered) of the melodies were different onall melody trials of the experiment. Testing and training melodies weresimilarly constructed. There were 45 different melodies and renditions usedon training trials, 15 on same trials, and 30 on dif ferent trials. Therewere 60 different melodies and renditions used on melody-test trials, plusthe transposition changes according to the transposition test.

For transposition tests (SAME-TUNE DIFF-FREQ), melodies weretransposed as tittle as four semitones to as many as 40 semitones. Thefollowing sequence specifies distance (in semitones), transposition direc-tion ( + / - for higher/lower frequency changes, respectively), and testingorder of transposition tests: +32, +38, +40, +28, - 9, -5 , -2 7, -2 1,-19, -6, +10, +30, -10, +4, +9, -31, -6, +22, +9, -11, -8, -23,-1 9, -1 5, +40, - 22 , -3 2, -1 3. It should be noted that there were no12-semitone (octave) transpositions.

For the o ther tests (DIFF-TUNE SAME-FREQ), both melodies on eachtrial shared the same notes. The second melody was a scrambled version ofthe fwst. By chance, some melody pairs began or ended on the same note.No pair had both melodies beginning and ending on the same note.

R e s u l t s a n d D i s c u s s io nThe results are shown in Figure 2. Training-trial performance is

shown on the left. Performance was comparatively accurate withnatural sounds (BW = 75.5%, 76.5%; FD = 76.9%, 78.4% forDIFF & SAME, respectively) and somewhat less accurate withtraining melodies (BW = 80.0%, 73.3%; FD = 53.3%, 66.7% forDIFF & SAME, respectively).

Performance on the test trials is displayed as percent response.This is the response ( s a m e - d i f f e r e n O that would be exp ected if themonkeys were matching melodies irrespective of frequency. Thus,for the DIFF-TUNE SAME-FREQ test, the percent different

1 O 0

9 0on - 80n.-o 70I- -Z,. , 6 0tu 50O.

40

TRAINING TESTING1 O 0

9 0 " 't/1Z80 o

Transpos i t ionGenera l i za t ion 70 t~6 0 zW

m. . . . . . . . . 50 ,.,0.4 0DIFF-TUNEDIFF-FREO

DIFF SAME SAME-TUNE DIFF-TUNE SAME-TUNEN A T U R A L SOUNDS SAME-FREQ SAME-FREO DIFF-FREO

Figure 2. Mea n same~di f ferent (DIFF) training and testing performance of two monkeys with trials composedof natural/environmental sounds (left) and random-synthetic melodies (right). For DIFF-TUNE SAME-FREQ(frequency) testing trials, the percent dif ferent responses is plotted because the two melodies of a trial weredifferent. For SAME-TUNE DIFF-FREQ testing trials, the percent same response is plotted because the twomelodies of each trial were the same, even though their note frequencies were different. The dashed line ischance (50% correct) performance.


5/17

M O N K E Y O C T A V E G E N E R A I .r Z A T IO N A N D M U S I C P E R C EP T IO N 2 9 5( D I F F ) r e s p o n s e i s p l o tt e d b e c a u s e t h e t w o m e l o d i e s w e r e d i f f e r e n te v e n t h o u g h t h e i r n o t e s w e r e t h e s a m e . T h e s e m e l o d i e s w e r ej u d g e d t o b e d i f f e re n t 7 4 % o f t h e ti m e ( 7 3 . 3 % f o r B W a n d 7 5 . 9 %f o r F D ) e v e n t h o u g h t h e y s h a r e d t h e s a m e s i x n o t e s . T h i s r e s u l ts h o w s t h a t t h e m o n k e y s w e r e n o t u n d e r s t i m u l u s c o n t r o l o f i n d i-v i d u a l n o t e s , w h i c h a d d s t o t h e e v i d e n c e t h a t t h e i r re s p o n s e s w e r eb a s e d o n t h e r e l a t i o n sh i p a m o n g n o t e s , t h e m e l o d y .F o r t r a n s p o s i t i o n t e s t s ( S A M E - T U N E , D I F F - F R E Q ) , p e r c e n ts a m e r e s p o n s e w a s p l o t t e d b e c a u s e t h e m e l o d i e s w e r e t h e s a m ee v e n t h o u g h t h e f r e q u e n c i e s ( F R E Q ) o f t h e n o t e s w e r e d i f f e r e n t .T h e s e a r e t h e c r i t i c a l t r a n s p o s i t i o n t e s t s , a n d t h e r e f o r e t h i s h i s t o -g r a m i s f' f il e d i n t h e f i g u r e . T h e m o n k e y s d i d n o t g e n e r a l i z e t ot h e s e t ra n s p o s e d m e l o d i e s ( 4 6 . 7 % f o r B W , 6 0 % f o r F D ) . T h e yj u d g e d t h e m t o b e t h e s a m e m e l o d y o n l y 5 3 . 3 % o f t h e ti m e . T h i sp e r f o r m a n c e w a s n o t ( s i g n i f i c a n t l y ) d i f f e r e n t f r o m ( 5 0 % )c h a n c e - - - t ( 1 ) = 0 . 3 5 , p > . 5 , s i n g l e m e a n s t e s t : H a y s , 1 9 6 3 , p .3 1 I - - - a n d w a s ( s i g n i f i c a n t l y ) d i f f e r e n t f r o m t r a i n i n g - t ri a l ( S A M Ea n d D I F F ) p e r f o r m a n c e , F ( 1 , 4 ) f fi 3 1 . 7 , p < . 0 1 . I n c o n c l u s i o n ,t h e r e i s n o e v i d e n c e t h a t t h e s e m o n k e y s g e n e r a l i z e d t o t h e s et r a n s p o s e d s y n t h e t i c m e l o d i e s .

E x p e r i m e n t 2T h e l a c k o f g e n e r a l i z a t i o n t o t r a n s p o s e d m e l o d i e s i n E x p e r i -

m e n t 1 w a s p u z z l i n g . O n e p o s s i b i l it y w a s t h a t m o n k e y s d o n o th a v e t h i s a b i l i t y , a s D ' A m a t o ( 1 9 8 8 ) h a d c o n c l u d e d . A n o t h e rp o s s i b i l i t y w a s t h a t t h e s y n t h e t i c m e l o d i e s w e r e i n a d e q u a t e i ns o m a w a y f o r t e s ti n g o c t a v e g e n e r a l iz a t i o n . T h e i r r a n d o m c o m p o -s i t i o n d i d n o t r e s u l t i n w h a t m o s t l i s t e n e r s w o u l d r e f e r t o a s am e l o d i c t u n e . I n d e e d , 4 4 % o f t h e s e s y n th e t i c m e l o d i e s h a d n o t e so u t s i d e t h e a p p r o p r i a t e d i a t o n i c s c a l e , s i m i l a r t o w h a t T r e h u b( 1 9 9 3 ) a n d T r e h u b , T h o r p e , a n d T r a i n o r ( 1 9 9 0 ) r e f e r r e d t o a s"bad" m e l o d i e s . T u n e s t h a t a r e n o t m u s i c a l t e n d t o b e l e s s m e m -o r a b l e ( e . g ., F r a n c e s , 1 9 5 8 , E x p e r i m e n t 9 ; K r u m h a n s l , 1 9 7 9 , E x -p e r i m e n t 3 ; T r e h u b , C o h e n , T h o r p e , & M o r r o n g i e U o , 1 9 8 6 ). A n yd e t r i m e n t t o t h e m e m o r a b i l i t y o f a m e l o d y w o u l d , i n t u r n, b ee x p e c t e d t o a d v e r s e l y a f f e c t tr a n s po s i ti o n . H o w c o u l d a t r a n s p o s e dm e l o d y b e m a t c h e d t o o n e p r e v i o u s l y h e a r d , f f t h e p r e v i o u s o n ec a n n o t b e r e m e m b e r e d ?

I n E x p e r i m e n t 2 , w e e x p l o r e d t r a n s p o si t io n s o f m e l o d i e s t h a tw o u l d b e e x p e c t e d t o b e m o r e m u s i c a l , m o r e s c a l a r , m o r e t o n a l ,a n d m o r e m e m o r a b l e t h a n t h e s y n th e t i c m e l o d i e s o f E x p e r i m e n t 1 .T h e r a t i o n a l e w a s t h a t b y m a x i m i z i n g t h e s e q u a l i t i e s w e m i g h tm a x i m i z e t h e c h a n c e s o f f i n d i n g s a m e - m e l o d y r e c o g n i t i o n in t h e s em o n k e y s . A m o n g m e l o d i e s c o n s i d e r e d t o b e m o s t m u s i c a l a r ec h i l d h o o d s o n g s , s u c h a s " O l d M a c D o n a l d , " " Y a n k e e D o o d l e , "a n d " H a p p y B i r t h d a y " ( e . g ., D o w l i n g , 1 9 8 8 ; K a l l m a n & M a s s a r o ,1 9 7 9 ; U n y k , T r e h u b , T r a i n o r , & S c h e l l e n b e r g , 1 9 9 2 ) . M o s t p e o p l ef i n d s u c h c h i l d h o o d s o n g s m e m o r a b l e , o c c a s i o n a l l y t o t h e p o i n t o fa n n o y a n c e . I n a d d i t i o n , ( w h o l e ) o c t a v e t r a n s p o s i t i o n s w e r e t e s t e dr a t h e r t h a n p a r t i a l o c t a v e t ra n s p o s i t i o n s . T h e r a t i o n a l e w a s t h a tt h e s e t w o f a c t o r s , c h i l d h o o d s o n g s a n d o c t a v e t r a n s p o s i t i o n s ,m i g h t w o r k t o g e t h e r t o i n c r e a s e t h e c h a n c e s o f f i n d i n g o c t a v eg e n e r a l i z a t i o n a n d m e l o d y r e c o g n i t i o n i n m o n k e y s .

M e t h o dSub jec t s and Appara tus

The subjects and apparatus were identical to Experiment 1.

Procedure and S t imul iTh e procedure was similar to Experiment 1, exc ept that childhood songswere tes ted. These chi ldhood songs were the f i rst s ix notes of "Ro w Ro w

Row Your Boat , " "Oh Susanna," "London Bridge," "Old MacDonald,"" Yankee Dood le , " " R ing Around the R os ey , " " Sk ip T o M y L ou , " " T woBits , " "Camptown Races ," "Happy Bir thday," and "How Much Is ThatDoggie I n T he W indow. " For one melody , " Sk ip T o M y L un I I , " the l asts ix notes were used. They were played in their original rhythms by amusician on a Yam aha D X7 electronic keyboard with the same ins trumentsas in Experiment 1: Flute, Accordion, Spanish Guitar, Oboe, ElectricPiano, Bag Pipe, Clarinet, Grand Piano, Honky-Tonk Piano, and Glock-enspiel. Melodies were recorded in three different octaves spanning afrequency range of 131 I - Iz to 988 Hz. T here were 12 melodies , 10instnnnents, and three octaves for a total of 360 recordings. Test melodieswere n ovel rendi t ions when ins trument and octav e were taken into account .Selection was quasirandom and as many aspects as possible were coun-terbalanced within the l imits o f the exper iment .Training trials were similar to Experiment 1. The natural-sound stimuliwere selected quas irandomly f rom the same 520 s t imulus pool used inExperiment 1. The synthetic melodies used in training were the same asExper iment 1, except that the order o f f irs t versus second melod y ondifferent trials varied quasirandom ly. Ea ch training m elod y was unique toa particular trial during the entire experiment. T he sequence of trials wasdifferent from Experiment 1.

On two test trials, octave transpositions of two melodies (childhoodsong) were tested. On each of these test trials, there was an octavedifference in frequency between presentations of a melody. Thus, thesetr ials are referred to as Sam e-Melody, Dif ferent-Frequency (SAM E-TU NEDIFF-OCTAVE). These w ere the octave-general izat ion tes t t rials and w erethe trials of primary interest in this experiment. W ithin eac h test trial, bothpresentations o f the chi ldhood song we re played by the same ins trument .Selection of song, instrument, octave, and transposition direction (highervs. lower frequency) was quasirandom.

On the remaining two test trials, two different melodies (childhoodsongs) were presented f rom the same f requency range or octave. Thus ,these trials are referred to as Different-Melody, Same-Frequency trials(DIFF -TUN E SAME -FREQ ) and are essentially tes ts for control by f re-quency (as opposed to melody). Like the octave-generalizatiun test trials,both melodies we re played b y the same ins trument and selection o f song,insU'ument , and oc tave to b e tested w as quas irandom.

Reward on test trials was g iven for either response. R eward probabilitywas set equal to training-trial accuracy from the previous session fo r eac hsubject. This change in reinforcement probability was made so that testtrials wo uld be unlikely to be distinctive from training trials on the basis ofoutcome.

Resu l t s and Di scuss ionT h e r e s u l t s a r e s h o w n i n F i g u r e 3 . T r a i n i n g - t r i a l p e r f o r m a n c e i s

s h o w n o n t h e l e f t . T r a i n l n g - t r i a l a c c u r a c y w a s r e a s o n a b l y g o o dw i t h n a t u ra l s o u nd s ( B W = 7 8 . 7 % , 7 8 . 2 % ; F D = 7 5 . 3 % , 7 9 . 6 %f o r D I F F & S A M E , r e s p e c t iv e l y ) a n d w i t h s y n t h e t ic m e l o d i e s( B W = 8 0 . 0 % , 8 6 . 6 % ; F D = 8 6 . 7 % , 8 6 . 7 % f o r D I F F & S A M E ,r e s p e c t i v e l y ) .

T h e m o s t s t r i k i n g r e s u l t w a s t h e s u b s t a n t i a l g e n e r a l i z a t i o n t oo c t a v e - t ra n s p o s e d c h i l d h o o d s o n g s , c o m p a r e d w i t h t h e l a c k o f a n yg e n e r a l i za t i o n t o t r a n sp o s e d s y n t h e ti c m e l o d i e s o f E x p e r i m e n t 1 .O c t a v e g e n e r a l i z a t i o n w a s 7 6 . 7 % ( f o r b o t h m o n k e y s ) a n d i s s i g -n i f i c a n t l y d i f f e r e n t f r o m c h a n c e p e r f o r m a n c e , t (1 ) > 1 0 0 , p . 5, f o r D I F F & S A M E , r e s p e c t i v e l y . T h u s , i t c a n b e s a i d t h a tg e n e r a l i z a t i o n w a s c o m p l e t e b e c a u s e i t w a s e q u i v a l e n t t o t r a in i n g -t r ia l p e r f o r m a n c e .

T h i s i s t h e f i r s t d e f i n i t i v e e v i d e n c e ( i n o u r a s s e s s m e n t ) f o ro c t a v e g e n e r a l i z a t i o n f r o m a ( n o n h u m a n ) a n i m a l s p e c i e s a n d t h eI n ' s t e v i d e n c e f r o m a t a s k w h e r e a n i m a l s w e r e r e q u i r e d t o c o m p a r ep a i r s o f m u s i c a l p a s s a g e s . T h e g e n e r a l i z a t i o n w i t h c h i l d h o o d s o n g si s i n te r e s t i n g f r o m a h u m a n d e v e l o p m e n t a l p e r s p e c ti v e . I t m i g h t b er e a s o n a b l e t o a s s u m e t h a t h u m a n r e c o g n i t i o n o f s u c h o c t a v e t r a n s -p o s e d c h i l d h o o d s o n g s w o u l d d e p e n d o n a l if e t i m e o f e x p o s u r e t ot h e s e m e l o d i e s ( e l . D o w l i n g , 1 9 7 8 ). H o w e v e r , t h e m o n k e y ss h o w e d g o o d g e n e r a l i z a t i o n t o ( o c t a v e ) t r a n s p o s e d c h i l d h o o ds o n g s w i t h l i tt l e o r n o e x p e r i e n c e w i t h t h e m , l e t a l o n e a l if e t i m e o fe x p e r i e n c e . T h e m u c h g r e a t e r g e n e r a l i z a t io n t o c h i l d h o o d s o n g st h a n s y n t h e t i c m e l o d i e s m e a n s t h a t t h e c r i t i c a l d i f f e r e n c e i s t o b ef o u n d i n t h e m e l o d i e s t h e m s e l v e s .

B e f o r e c o n s i d e r i n g m a n i p u l a t i o n s t h a t m i g h t a f f e c t o c t a v e g e n -e r a l i z a ti o n , i t s h o u l d b e p o i n t e d o u t t h a t th e r e w a s s o m e i m p r o v e -m e n t o n t r a i n i n g t ri a l s w i t h s y n t h e t i c m e l o d i e s r e l a t i v e to E x p e r -i m e n t I . T h i s s l i g ht i m p r o v e m e n t c o u l d h a v e b e e n d u e t o t h eg r e a t e r e x p e r i e n c e w i t h th e m u s i c a l p a s s a g e s . T h e n e x t e x p e r i m e n tw a s c o n d u c t e d t o e v a l u a t e a n y e f f e c t t h i s g r e a te r e x p e r i e n c e m i g h th a v e o n g e n e r a l i z a t i o n to t h e t r a n s p o s e d s y n t h e t i c m e l o d i e s o fE x p e r i m e n t 1 .

E x p e r i m e n t 3W e c o n d u c t e d E x p e r i m e n t 3 t o t e s t t h e p o s s ib i l i ty t h a t g r e a te r

e x p e r i e n c e w i t h m u s i c s t i m u l i m i g h t h a v e i n f l u e n c e d t h e d i f f e r -e n c e i n g e n e r a l i z a t i o n b e t w e e n E x p e r i m e n t s 1 a n d 2 . T h u s , E x -p e r i m e n t 3 w a s e s s e n ti a l l y t h e t h ir d " l e g " o f a n A - B - A e x p e r i -

m e n t a l d e s i g n , w h e r e t h e f i r s t t e s t ( A ) i s r e p e a t e d t o c o n t r o l f o r t h ep o s s i b i l i t y t h a t e x p e r i e n c e h a s i n f l u e n c e d t h e r e s u l t s . S y n t h e t i cm e l o d i e s o f E x p e r i m e n t 1 w e r e r e t e s te d w i t h s o m e m i n o r m o d i f i -c a t i o n s to m a k e E x p e r i m e n t 3 m o r e s i m i l a r t o E x p e r i m e n t 2 t h a nw a s E x p e r i m e n t 1 .

M e t h o dS u b j e ct s a n d A p p a r a t u s

The subjects and apparatus were the same as in Experiments 1 and 2 .P r o c e d u r e

Tria ls and s t imul i in th is experiment were s imi lar to Experiment 1 ,except for a reduct ion in the to ta l number of melodies to be tested ont ransposi t ion tests . Train ing t r ia l s and t ra in ing s t imul i were s imi lar in termsof s t imulus se ts and com posi t ion . Pai rings (natural sounds), melody orderon m elody t ra in ing , and t r ia l sequences varied dai ly and were d i fferent thanthose of previous experiments .On t ransp osi t ion tests , 12 of the 30 synthet ic melodies tested in Exper-imen t 1 were re tested in th is experiment . The 12 melodies were m atched interms o f note repet i t ions to the 12 chi ldhood songs of Experime nt 2 . Thus,s ix melodies conta ined three d i fferent notes (p lus three repet i t ions), f ivemelodies conta ined four d i fferent notes , and one melody contained fivedi fferent notes . These 12 melodies were recorded by the same 10 inst ru-ments and were tested a t the same t ransposi t ions as in Experiment 1 . Theselect ion of inst ruments used to p lay the test melodies varied quasi ran-domly. W hen inst rum ent and octave are considered, these rendi t ions of theme l o d i e s h ad n o t b een p rev i o u s ly h ea rd b y t h e m o n k ey s . Th e n u m b er o fsemi tones t ransposed , d i reet iun of t ransposi t ion , and the order o f test ing fort h e f i r s t b l o ck o f th e 1 2 me l o d i e s w as 1 1 , 4 0 , -3 2 , 9 , -1 9 , -9 , -1 9 ,-1 3 , 3 2 , 28 , - 2 3 , 1 0 . O t h e r ran do mi zed b lo ck s o f t h e se same me l o d i esand same t ransposi t ions (but d i fferent synthet ic inst ruments) were a lsotested . A s in Experim ent 2 , the re inforcem ent probabi l i ty for e i ther re-sponse on test t r ia l s was equal to the re inforcem ent ra te from the previoussession . T he sam e num ber of test sessions (15), t ra in ing t r ia l s, and test ingt ria ls (2 per session) were conducted .


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M O N K E Y O C T A V E G E N E R A L I Z A T I O N A N D M U S I C P ER C E PT IO N 297R es u l t s

T h e r e s u l t s a r e s h o w n i n F i g u r e 4 . A s i n E x p e r i m e n t 1 , t r a i n i n gt r ia l a c c u r a c y w i t h s y n t h e t i c m e l o d i e s w a s s o m e w h a t l e s s a c c u r a t e( B W = 6 6 .7 % , 7 3 .3 % ; F D = 6 0 .0 % , 7 3 .3 % f o r D I F F & S A M E ,r e s p e c t i v e l y ) t h a n w i t h n a t u r a l s o u n d s ( B W = 8 1 . 2 % , 8 2 . 8 % ;F D = 8 2 . 0 % , 8 4 .6 % f o r D I F F & S A M E , r e sp e c t i v e ly ) .O n c e a g a i n , th e m o s t i m p o r t a n t r e s u l t w a s t h e l a c k o f g e n e r a l -i z a t io n ( 5 1 . 7 % ) t o t r a n sp o s e d m e l o d i e s ( 6 0 .0 % f o r B W , 4 3 . 3 % f o rF D ) , w h i c h w a s n o t s i g n i f i c a n t l y d i f f e r e n t f r o m c h a n c e p e r f o r -m a n c e , t ( 1 ) = 0 . 1 9 , p > . 5 , s i n g l e m e a n s t e s t .

A n A N O V A s h o w e d s i g n i fi c a n t e f f e c t a cr o s s tr a i n in g a n d t e s t-i n g c o n d i t i o n s , F ( 5 , 6 ) = 8 . 7 5 , p = . 0 1 1 . P l a n n e d c o m p a r i s o n t e s t s( u s i n g t h e M S E f r o m t h e A N O V A ) s h o w e d t h a t g e n e r a l i z a t i o n t ot r a n s p o s e d m e l o d i e s d i f f e r e d s i g n i f i c a n d y f r o m t r a i n i n g p e r f o r -m a n c e w i t h n a t u ra l s o u n d s , t s( 6 ) = 5 . 0 2 , 5 .3 7 , p > . 0 1 , f o r D I F F& S A M E , r e s p e c t i v e l y .

E x p e r i m e n t 3 e s s e n t i a l ly r e p l i c a te d E x p e r i m e n t 1 b u t w i t h as m a l l e r s e t o f 1 2 s y n t h et i c m e l o d i e s m a t c h e d i n t e r m s o f n o t er e p e t i t i o n s t o t h e c h i l d h o o d s o n g s o f E x p e r i m e n t 2 . T h e l a c k o fg e n e r a l i z a t i o n t o t h e t r a n s p o s e d m e l o d i e s w a s e s s e n t i a l l y s i m i l a r( 5 1 . 7 % v s . 5 3 . 4 % f r o m E x p e r i m e n t 1 ) a n d c o n t r a s t s w i t h t h ec o n s i d e r a b l e g e n e r a l i z a ti o n ( 7 6 . 7 % ) t o t r a n sp o s e d c h i l d h o o d s o n g so f E x p e r i m e n t 2 . T h u s , t h i s e x p e r i m e n t e s t a b l i s h e s t h a t g e n e r a l i -z a t i o n t o th e c h i l d h o o d s o n g s w a s n o t d u e t o g r e a t e r e x p e r i e n c e o nt h e p a r t o f t h e m o n k e y s .

E x p e r i m e n t 4E x p e r i m e n t 3 r e t e s t e d t h e s y n t h e ti c m e l o d i e s t e s te d i n E x p e r i -

m e n t 1 b u t w i t h t h e n u m b e r o f m e l o d i e s , n o t e r e pe t i ti o n s , a n dr e i n f o r c e m e n t c o n t i n g e n c i e s o f E x p e r i m e n t 2 . T h e r e w e r e , h o w -e v e r , t h r e e r e m a i n i n g d i f f e r e n c e s o t h e r t h a n t h e m e l o d i e s t h e m -s e l v e s ( c h i l d h o o d s o n g s v s . s y n t h e t i c m e l o d i e s ) . A m i n o r d i f f e r -e n c e w a s t h e f r e q u e n c y r a n g e . T h e s y n t h e t i c m e l o d i e s c o v e r e d af o u r - o c t a v e r a n g e , w h e r e a s t h e c h i l d h o o d s o n g s c o v e r e d o n l y t h r e eo c t a v e s , t h e l o w e r t h r e e o c t a v e s o f t h e s y n t h e ti c m e l o d i e s . A n o t h e rd i f f e r e n c e w a s t h e l a r g e r t r a n s p o s i t i o n d i s t a n c e f o r s o m e s y n t h e t i cm e l o d i e s . T h r e e s y n t h e ti c m e l o d i e s w e r e t r a n s p o s e d m o r e t h a n t w o

o c t a v e s a n d o n e m o r e t h a n t h r e e o c t a v e s . A t h i rd d i f f e r e n c e w a st h e p a r t i a l o c t a v e t r a n s p o s i t i o n s o f t h e s y n t h e t i c m e l o d i e s . P a r t i a lo c t a v e t r a n sp o s i ti o n s c h a n g e t h e k e y ( c h r o m a ) o f t h e m e l o d y .T h e s e d i f f e r e n c e s , p a r t i c u l a r l y t h e l a t t e r t w o , c o u l d h a v e i n f l u -e n c e d t h e l a c k o f g e n e r a l i z a ti o n t o t r a n s p o se d s y n t h e ti c m e l o d i e sa n d t h u s w e r e t e s t ed i n E x p e r i m e n t 4 .

T h e p u r p o s e o f E x p e r i m e n t 4 w a s t o t e s t th e s a m e s y n t h e ti cm e l o d i e s o f E x p e r i m e n t 3 b u t w i t h o n e o c t a v e ( 1 2 s e m i t o n e )t r a n sp o s i ti o n s a n d t h e s a m e t h r e e o c t a v e r a n g e a s u s e d w i t h t h ec h i l d h o o d s o n g s .

M e ~ o dS u b j e c t s a n d A p p a r a t u s

The subjects and apparatus we re the same as in previous exper iments .P r o c e d u r e

Training trials and training stimuli in this experiment were similar tothose of previous experiments. But the sequences, environmental-stimuluspairings, and order of presentation va ried quasirandomly and w ere differentfrom previous experiments. As in previous experiments, sessions con-tained 26 training trials and four testing trials, and the experiment wasconducted for 15 sessions.Transposition tests we re octave-generalization tests (SA ME -TU NEDIFF-OCTAVE). The same 12 synthetic melodies tested in Experiment 3were tested with one-octave transpositions. The 12 synthetic melodies wererecorded with the same 10 instruments , o ver the same three o ctave rangeas the chi ldhood songs in Exper iment 2. They w ere tes ted in randomizedblocks o f the 12 melodies with direction of transposition, particular octave,and instrument counterbalanced within the limits of the experiment. W ithinstrument and octave taken into account, the renditions tested in thisexperiment were novel.

Melodies on control tests (DIFF-T UN E SAM E-FRE Q) were also novelrenditions. These tests were similar to those of Experiment 2. The tw odifferent melodies presented o n a trial shared the same frequency range an dwere recorded with the same ins trument . Reward was given for ei therresponse on test trials with reward probability eq uiva lent to the accuracy ontraining trials from the previous session for each subject.

I--0IJJ0[.Y.0(JI-ZIJJ0[.laJO.

1 0 09 0

8 07 06 05 04 0

1 O 09 0 uJ

Z8 O oa.T r a n s p o s i t i o n nG e n e r a l i z o t i o n 7 0 ~

TRAINING TESTING

uJ3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 0

4 0

D I FF S A M E D I F F - T U N E S A M E -T U N E D I F F -T U N E S A M E -T U N EN A T U R A L S O U N D S D I F F - F R E Q S A M E -F R E Q S A M E- FR E Q D I F F - F R E Q

Figure 4. Results of a replication of Experiment 1 (Figure 2). Me an same~different DIFF) training and testingperformance of two monkeys w ith trials composed of natural/environmental sounds (left) and random-syntheticmelodies (right). FREQ = frequency.


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29 8 WRIGHT, RIVERA, HULSE, SHYAN, AND NEIWORTHR e s u l t s

T he r e s u l t s a r e show n i n F i gu r e 5 a n d a r e s hn i l a r t o t hos e o fE xpe r i m e n t s t a nd 3 . T r a i n i ng t ri a l a c c u r a c y w a s goo d w i t h na t u r a ls o u n d s (B W = 8 4 . 4 % , 8 2. 8 % ; F D = 8 4 . 4 % , 8 4. 9 % f o r D I F F &SA M E , r e s pe c t i ve l y ) a nd w i t h s yn t he t ic m e l od i e s ( B W = 86 . 7% ,8 0 . 0% ; F D = 9 3 . 3 % , 6 0 . 0% f o r D I F F & S A M E , re s p e c ti v e ly ) .A s i n p r e v i ous t e s t s w i t h s yn t he t i c m e l od i e s , t he m os t i m por t a n tr e s u l t w a s t he l a c k o f ge ne r a l i z a t ion ( 51 . 7% ) t o one - oc t a ve t r ans -p o s e d m e l o d i e s (4 6 . 7 % f o r B W , 5 6 . 7 % f o r F D ) , w h i ch w a s n o ts i gn i f i c a n t ly d i f f e r e n t f r om c h a nc e pe r f o r m a nc e , t ( 1 ) = 0 . 34 , p >.5 , s ingle means t e s t .

A n A N O V A s h ow e d s i gn i f i c a n t e f f e c t o f t r ai n i ng a nd t e st i ngc ond i t i ons , F ( 5 , 6) = 8 . 41 , p = . 012 . P l a nne d c om pa r i s on te s t s( u s i n g t h e A N O V A M S E t e r m ) s how e d s i gn i f i c a n t d i f f e r e nc e s fo rone - oc t a ve t r a ns pos i t i ons o f s yn t he t i c m e l od i e s r e l a t i ve t o na t u r a l -s ound pe r f o r m a n c e s - - t s ( 6 ) = 4 . 84 , 5 . 76 , p < . 01 , f o r SA M E a ndD I F F , r e s p e c t i v e l y - - a n d r e l a ti v e t o t r a in i n g - m e l o d y p e rf o r -m a nc e s , ta (6 ) = 2 . 71 , 5 . 67 , p < . 05 , fo r D I FF & SA M E ,r e s pe c t i ve l y .

T he s e r e s u l t s a r e c om pa r a b l e t o t he l a c k o f ge ne r a l i z a t i on t ot r a ns pos e d s yn t he t i c m e l od i e s f r om E xpe r i m e n t 1 ( 53 . 4% ) a ndE xpe r i m e n t 3 ( 51 . 7% ) a nd c on t r a s t w i th t he oc t a ve ge ne r a l i z a ti onf o r c h i l dhood s ongs f r om E xpe r i m e n t 2 ( 76 . 7% ) .

T he r e s u l t s f r om t h i s e xpe r i m e n t t oge t he r w i t h t hos e f r ompr e v i ous e xpe r i m e n t s s how a c ons i de r a b l e d i f f e re nc e i n ge ne r a l i -z a t i on t o t r a ns pos e d s yn t he t i c m e l od i e s a s oppos e d t o c h i l dhoods ongs . T he m uc h g r e a t e r ge ne r a l i z a t i on t o c h i l dhoo d s ongs t ha ns yn t he t i c m e l od i e s m e a ns t ha t t he c r i t i c a l d i f f e r e nc e l i e s i n t hes t r uc tu r e o f t he s e m e l o d i e s a nd s ongs . T h e l a s t f ou r e xpe r i m e n t s o ft h i s a r t i c l e f oc us on d i f f e r e nc e s t ha t m i gh t ha ve l e d t o oc t a vege ne r a l i z a t i on w i t h c h i l dh ood s ongs a nd no t w i t h s yn t he t i cm e l od i e s .

E x p e r i m e n t 5I f m o n k e y s p e r c e i v e d c h i l d h o o d s o n g s a s w e d o , t h e n t h e

t e nde nc y t o ge ne r a l i z e t he s e m e l od i e s m i gh t be s ub j e c t t o s om e o ft he s a m e m a n i pu l a t i ons t ha t a f f e c t ou r pe r c e p t i on o f m e l ody . I fge ne r a l i z a t i on w e r e a f unc t i on o f t he t r a ns pos i t i on be i ng e x a c t l y

one oc t a ve , f o r e xa m pl e , t he n t h i s ge ne r a l i z a ti on m i gh t d i m i n i s hf o r pa r t i a l - oc t a ve t ra ns pos i t i ons o f t he c h i l d h o o d s o n g s . W h o l eoc t a ve t r a ns pos i t i ons p r e s e r ve t he ke y o r c h r om a o f t he o r i g i na lm e l o dy a nd a dd t o t he i r s i m i l a r it y . T h i s s i m i l a r i t y i s e v i de n t byno t e s o f t he s a m e c h r om a i n e a c h oc t a ve be i ng de s i gna t e d by t hes a m e l e t t e r na m e ( e . g ., C ) . O t he r t r a ns pos i ti ons c ha nge t he ke y a ndr e duc e t he num be r o f s ha r e d no t e s , tha t i s , no t e s s ha r i ng t he s a m el e t t e r na m e . T r a ns pos i t i ons o f 5 o r 7 s e m i t one s , f o r e xa m pl e ,p r e s e r ve 6 ou t o f 7 no t e s o f t he s c a l e . Suc h t r a ns pos i t i ons a r ee qu i va l e n t to a c ha nge f r om C m a j o r t o F o r G m a j o r . B y c on t r as t ,t r a ns pos i ti ons o f 6 s e m i t one s ( t o t he t r i t one ) p r e s er ve on l y 2 o f t heo r i g i na l 7 no t e s . Fo r e xa m pl e , t he 7 no t e s o f C m a j o r C - D - E - F-G - A - B b e c o m e F # - G # - A # - B - C # - D # - F . S u c h 6 - s e m i t o n e tr a n s p o -s i t ions d i m i n i s h t he pe r c e p t i on o f s a m e m e l ody f o r hum a n s ( e . g . ,K r um ha ns l , B ha r uc ha , & C a s t e l l a no , 1982; M a s s a r o e t a l. , 1980 ;T h o m p s o n & C u d d y , 1 9 92 ).

E xpe r i m e n t 5 t e s t e d ha l f a s w e l l a s w ho l e o c t a ve t ra ns pos i t i onso f t he c h i l dhoo d s ongs t o de t e r m i ne w he t he r o r no t s uc h t r a ns po -s i t ions w ou l d d i m i n i s h s a m e - m e l od y pe r c e p t i on in m o nke y s a st he y do i n hum a ns . O ne - oc t a ve t r a ns pos i t i ons w e r e r e t e s t e d t op r ov i de a w i t h i n - t e s t c om p a r i s on a nd r e p l i c a t i on o f t he o c t a ve -ge ne r a l i z a ti on t e st o f E xpe r i m e n t 2 . T e s t s w e r e a l s o c onduc t e dw i t h t w o- oc t a ve t r a ns pos it i ons . T w o- o c t a ve t r a ns pos i t ions f u l f i l la l l t he c ond i t i ons , r e qu i r e m e n t s , a nd a t t ri bu t e s o f one - oc t a ve t r a ns -pos i t i ons , bu t t he i r g r e a t e r p i t c h c ha nge s m a k e t he m m or e e x t r e m et e s t s o f oc t a ve ge ne r a l i z a t i on . I f t he m onke ys r e s pond d i f fe ren tw he n e ve r t he r e i s a ny pe r c e i ve d d i f f e re nc e , t he n t h e r e s hou l d bel i t t le oc t a ve g e ne r a l i z a ti on a t t w o - oc t a ve t r a ns pos i ti ons . O n t heo t he r ha nd , f f t he y he a r t he t ra ns pos e d m e l od y a s t he s a m e m e l od ya nd r e s pon d s a m e t o s i m i l a r m e l od i e s , t he n the r e s hou l d be goodoc t a ve ge n e r a l i z a ti on e ve n t o t he s e t w o- oc t a ve t r a ns pos i ti ons . B yt e s t ing t w o- oc t a ve t r a ns pos i t i ons , a s e c on d h a l f - oc t a ve t e s t ( tr a ns -pos i t i on t o t he t r i tone ) w a s p os s i b l e a t 1 . 5 oc t ave s . T he s a m era t iona le tha t appl i e d to 0 .5 o c tave t e s t s appl i e s to 1 .5 oc tave t e s t sa nd p r ov i de s a no t he r i nde pe nde n t t e st a t a m or e d i s t a n t t r a ns pos i -t i on . T hus , t he pu r pos e o f E xp e r i m e n t 5 w a s t o t e s t m on ke ysw i t h 0 . 5 , 1 .0 , 1 .5 , a nd 2 . 0 oc t a ve t r a ns pos i t i ons o f t he c h i l dhoo ds ongs t e s t e d i n E xpe r i m e n t 2 .

1 O 0~_ 9 00uJn , 8 00o 7 0I- -Z,. , 6 0Un~' " 5 0n

4 0

T R A I N I N G T E S T I N G 1 O 09 0 t u

Z8 0 n o

O c t o v e mG e n e r o l i z o t i o n 7 0 a .

60 ~U

. . . . . . - - 5 0 , .,. . . . . i U .4 0

D I F F S A M E D I F F - T U N E S A M E - T U N E D I F F - T U N E S A M E - T U N EN A T U R AL S O U N D S D I F F - F R E O S A M E - F R E Q S A M E - F R E Q D I F F - O C T A V E

Figure 5. Results of a replication of Exp eriments 1 and 3 (Figures 2 & 4) w ith random-synthetic melodiestested with 1-octave transpositions. DI FF = different; FRE Q = frequency.


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M O N K E Y O C T A V E G E N E R A I J 'Z A T I O N A N D M U S I C P E R C E P T I O N 2 9 9Method

Subjects and ApparatusT h e s u b j e c t s a n d a p p a r a t u s w e r e t h e s a m e a s i n p r e v i o u s e x p e r i m e n t s .

ProcedureT h e p r o c e d u r e w a s s i m i l a r to t h a t o f p r e v i o u s e x p e r i m e n t s , e x c e p t t h a t

c h i l d h o o d s o n g s w e r e t e s t e d a t tr a n s p o s i t i o n s o f 0 . 5 , 1 . 0, 1 .5 , a n d 2 . 0o c t a v e s . T h e r e w e r e 2 8 t r a i n in g t r i a ls e a c h s e s s i o n , 2 6 n a t u r a l - s o u n dt r a i n i n g t r i a ls a n d 2 m e l o d y - t r a i n i n g t r i a ls . T h e m e l o d y - t r s i n i n g tr i a l s w e r et h e s a m e a s i n p r e v i o u s e x p e r i m e n t s s o t h a t d i f f e r e n c e in n ' a l n i n g r e g i m ew o u l d n o t i n t r o d u c e p o t e n ti a l c o n f o u n d s w h e n c o m p a r i n g e x p e r i m e n t s .F o r t y s e s s i o n s w e r e c o n d u c t e d i n t h i s e x p e r i m e n t .

I n e a c h s e s s i o n , t h er e w e r e 2 m e l o d y - g e n e r a l i z a t i o n te s t t ri a ls . T h em e l o d i e s , i n s t r u m e n t s , d i r ec t io n , a n d d e g r e e o f t r a n s p o s i ti o n w e r e d i f f e re n to n t h e s e t w o t e s t t r i a l s . O n o n e o f t h e s e t r i a l s , t h e t r a n s p o s i t i o n w a s aw h o l e - o c t a v e ( 1 . 0 o r 2 . 0 o c t a v e s ) a n d o n t h e o t h e r i t w a s a p a r t i a l - o c t a v e( 0 . 5 o r 1 . 5 o c t a v e s ) . M e l o d i e s w i t h i n a t r i a l w e r e p l a y e d b y t h e s a m e( s y n t h e t i c ) i n s t r u m e n t . T h e v a r i a b l e s o f m e l o d y , i n s t r u m e n t , a n d s c a l ep o s i t i o n ( f r e q u e n c y ) w e r e v a r i e d q u a s i r a n d o m l y a n d c o u n t e r b a l a n c e dw i t h i n t h e l i m i t s o f t h e e x p e r i m e n t .T h e m e l o d i e s w e r e t h e s a m e c h i l d h o o d s o n g s a s in E x p e r i m e n t 2 . E a c hc h i l d h t x x t s o n g w a s r e c o r d e d a t f i v e d i f f e r e n t f r e q u e n c i e s w i t h i n t h et h r e e - o c t a v e r a n g e u s e d i n p r e v i o u s e x p e r i m e n t s , r e s u l t i n g i n t h r e e f u l lo c t a v e a n d t w o h a l f o c t a v e r e n d it i o n s o f e a c h m e l o d y . T h e y w e r e r e c o r d e dw i t h t h e s a m e 1 0 s y n t h e t ic i n s m m a e n t s u s e d p r e v i o u s l y , y i e l d in g 6 0 0d i f f e r e n t m e l o d i e s a n d r e n d i ti o n s (1 2 m e l o d i e s 1 0 i n s t r u m e n t s x 5 s c a l ep o s i t io n s ) . T h e r e n d i ti o n s t e s t e d, w h e n c o n s i d e r i n g t h e a b o v e t h r e e v a r i -a b l e s , w e r e n o v e l i n t h i s a n d o t h e r e x p e r i m e n t s o f t h i s a r ti c le .

Results and DiscussionT he r e s u l t s a r e s how n i n F i gu r e 6 . T r a i n i ng - t r i a l pe r f o r m a nc e i s

s how n o n t he l e f t. T r a i n i ng t r i al a c c u r a c y w a s goo d w i t h na t u r a ls o u n d s ( B W = 8 3 . 7% , 8 0 . 7 % ; F D = 8 0 . 8% , 8 1 . 5 % f o r D I F F &SA M E , r e s pe c t i ve l y ) a nd w i t h s yn t he ti c m e l od i e s ( B W = 87 . 5% ,9 0 % ; F D = 8 7 . 5% , 8 2 . 5 % f o r D I F F & S A M E , r e sp e c t iv e l y ).

G e ne r a l i z a t i on t o t r a ns pos e d m e l od i e s i s s ho w n i n t he f 'f ll edh i s t og r a m s on t he r i gh t o f t he f i gu r e . T he r e w a s go od ge ne r a l i z a -t i on ( 77 . 5% ) t o one - oc t a ve tr a ns pos i t i ons ( 80% f o r B W , 75% f o rFD ) , a nd t h i s de g r e e o f ge ne r a l i z a ti on w a s s i m i l a r t o the on e -oc t a ve g e ne r a l i z a t ion ( 76 . 7% ) f r om E xpenm " e n t 2 . G e ne r a l i z a t ion

w a s e ve n 10% be t t e r ( 87 .5% ) t o t w o- oc t a ve t ra ns pos i t i ons (90%f or B W , 85% f o r FD ) a nd w a s e ve n s l i gh t l y be tt e r tha n t r a i n i ng -t r i a l a ccuracy.

A N O V A s how e d a s i gn i f i c a n t e f f e c t a c r o s s t ra i n i ng a nd t e s t ingc ond i t i ons , F ( 7 , 8 ) = 227 . 0 , p < . 0001 . P l a nne d c om pa r i s on te s t s( u s i n g t h e A N O V A MSE term) s how e d t ha t t he t w o- oc t a ve ge n -e r a l i z a ti on w a s m a r g i na l l y be t t e r t ha n t he na t u r a l - sound t r a in i ngpe r f o r m a nc e f o r SA M E , t s( 8 ) = 2 . 55 , p < . 05 , bu t no t fo r D I FF ,t s(8) = 1 .98, p > .05 . Th e one -oc tav e gene ra l i za t ion was marg in-a l l y w or s e t ha n na t u r a l - sound t r a i n i ng pe r f o r m a nc e , t ,( 8 ) = 2 . 97 ,2 . 40 , p < . 05 , f o r D I FF & SA M E , r es pe c t i ve l y .

B y c on t r a st , t he r e w a s no s i gn i f i c a n t ge ne r a l i z a t i on f o r e i -t he r 0 . 5 -oc t a ve t r ans pos i t i ons ( 35% f o r B W , 40 % f o r FD ) o r 1 . 5 -oc t a ve t r a ns pos i t i ons ( 40% f o r B W , 35% f o r FD ) . P l a nne d c om -pa r i s on t e s t s ( u s i ng t he A N O V A MSE term) s how e d t ha tge ne r a l i z a t i on w i t h 0 . 5 o r 1 .5 oc t a ve t r a ns pos i t ions d i f f e r e d s i g -ni f i cant ly f rom na tura l - so und t r a in ing pe r form ance , t s(8 ) = 22.8 ,22 . 2 , p > . 0001 , f o r D I F F & SA M E , re s pe c t i ve l y .

T he s ubs t a n t i a l pe r f o r m a nc e d i f f e r e nc e be t w e e n f u l l a nd ha l foc t a ve t r a ns pos i ti ons a dds t o t he e v i de nc e t ha t m onk e ys pe r c e i vet he s e c h i l dhood s ongs s i m i l a r t o t he w a y hu m a ns pe r c e i ve the m .T he 0 . 5 a nd 1 .5 t r a ns pos i t ions p r e s e r ve d c on t ou r a nd i n t e r va l o ft he m e l od i e s i n t he s a m e m a nne r a s t he 1 .0 a nd 2 . 0 t r a ns pos i t i ons .Y e t , t he r e i s no ge ne r a l i z a t ion t o t he s e ha l f - oc t a ve t r ans pos i t i ons .T h i s m e a ns t ha t m o nke ys u s e c h r om a o f t he s c a l e i n c on j unc t i onw i t h o t he r a s pe c ts s uc h a s m e l od i c c on t ou r in m a k i ng j udgm e n t s o fs a m e m e l ody , a s do hum a ns ( B a r t l e t t & D ow l i ng , 1980; I d s on &M a s s a r o , 1978 ; K a l l m a n & M a s s a r o , 1979 ; K r u r a ha ns l e t al . ,1982; M a s s a r o e t a l . , 1980 ; T hom ps on & C udd y , 1992) .

G o od o c t a ve ge ne r a l i z a t ion t o t w o- oc t a ve t r a ns pos i ti ons w a sr e a s s u r ing i n l i gh t o f e x t r a po l a t i ons f r om h um a n m us i c pe r c e p t i ona nd t he l a r ge p i t c h c ha nge s p r od uc e d by s uc h t r a ns pos i ti ons . Suc hp i t c h c ha nge s a r e ve r y n o t i c e a b l e f o r r he s us m on ke ys ( e . g . , S t e b -b i n s , 1973 ) a s t he y a r e f o r hum a ns ( e . g . , S t e ve ns & V o l km a nn ,1940) .

E x p e r i m e n t 6O ne p u r pos e o f E xp e r i m e n t 6 w a s t o t e s t t ra ns pos i t i ons o f

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F i g u r e 5 . T r a i n i n g a n d t e s ti n g p e r f o r m a n c e w i t h n a t a r a l /e n v i m m n c n t a l s o u n d s a n d c h il d h o o d s o n g s s uc h a s" H a p p y B i r t h d a y . " T h e c h i l d h o o d s o n g s w e r e te s t e d a t 0 . 5 , ] . 0 , ! . 5 , a n d 2 . 0 o c ta v e s o f tr a n s p o s i t i o n . T h e 1 . 0a n d 2 . 0 o c t a v e m m s p o s i f i o n s w e r e te s t s o f o c t a v e g e n e r a l i z a t i o n . D ] F I : = d i f f e r e n t .


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30 0 WR I GHT , R I VE R .A, I -I UL SE , SHYAN, AN D NE I WO R T Ht h e m s e l v e s . N o t e s w e r e t r a n s p o s e d a n d t e s t e d i n E x p e r i m e n t 6 ju s tl i k e th e m e l o d i e s i n t h e p r e v i o u s e x p e r i m e n t . I f t h e m o n k e y s ca ndiscriminate these pitch changes (and report them accordingly),then such a result would show that pitch changes of melodies werediscriminable despite the melodies being judged to be the same.A d d i t i o n a l l y , s u c h a r e s u l t w o u l d s h o w t h a t i n d i v i d u a l n o t e s a r ei n a d e q u a t e f o r t e s t s o f o c t a v e g e n e r a l i z a ti o n . I t w o u l d s h o w t h a tm e l o d i e s , a n d i n p a r ti c u l a r m u s i c a l l y s t r o n g m e l o d i e s , a r e n e c e s -s a r y f o r t e s t s o f o c t a v e g e n e r a l i z a t i o n . T h e m e l o d y p r o v i d e s t h em u s i c a l c o n t e x t f o r o c t a v e g e n e r a l i z a t i o n , a n d t h e m e l o d y i s e f -f e c t i v e l y r e m o v e d w h e n i n d i v i d u a l n o t e s a r e t e s te d . T h e t r a n sp o -s i t i o n t e s t o f m e l o d i e s ( E x p e r i m e n t 5 ) w a s r e p l i c a t e d i n t h i se x p e r i m e n t i n a m i x e d d e s i g n s o t h a t n o t e ( p i t c h ) a n d m e l o d yg e n e r a l i z a ti o n s c o u l d b e c o m p a r e d w i t h i n t h e s a m e s e s s i o n .

MethodSubjects and Apparatus

The subjects and apparatus were the same as in previous experiments.P r o c e d u r e

The procedure was similar to that of Experiment 5, except that transpo-sitions of individual n otes w ere tested in addition to the w hole melodies.N o t e s were tes ted in the same manner as the melodies . Because of theadditional pitch-testing trials, there were no melody-training trials. Therewere 26 natural-sound training trials, two pitch-testing trials, and twomelody-testing trials each session. For the two pitch-testing trials, noteswe re taken from th e childhood songs and tested individually. The particularnotes tested were not necessarily notes from the particular melodies testedin the same session. Selection of notes was quasirandom, counterbalancedfor the me lody f rom where they or iginated, pos i t ion in the s ix-note m elody,instrument, and octave within the limits of the experiment.

During sample (center speaker) presentations, notes were repeated to fillthe 3-s sample listening time, like the melodies. Each note was presentedfor 200 ms w ith 200 ms between presentat ions . Notes we re presented eighttimes during sample presentations and 5-15 times during test presentations(depending on w hen the cho ice response was made) . Notes were tes tedat 0.5, 1 .0, 1 .5, or 2.0 octave t ranspos i tions, as w ere melodies. Thereinforcement probability for either choice response on all test trials wasequivalen t to the reinforcement rate on the previous sess ion 's t raining t r ialsfor each subject .

The two melody-testing (transposition) tests were similar to those ofExperiment 5. Th e particular renditions of the childhood songs tested w erenovel (with respect to instrument and octave). Selection and counterbal-ancing of melodies was similar to the previous experiment.

Results and DiscussionT h e r e s u l t s f r o m t h e e x p e r i m e n t a r e s h o w n i n F i g u r e 7 . A c c u -

r a c y o n t h e n a t u r a l - s o u n d t r a i n i n g t r i a l s r e m a i n e d h i g h( B W = 8 6 . 0 % , 7 6 . 3 % ; F D = 7 5 . 8 % , 8 3 .7 % f o r D I F F & S A M E ,r e s p e c t i v e l y ) .

T e s t r e s u l t s f o r o c t a v e t r a n s p o s e d m e l o d i e s a r e s h o w n i n t h er i g h t - h a n d p o r t i o n o f t h e f i g u r e . A s i n t h e p r e v i o u s e x p e r i m e n t ,t h e r e w a s g o o d g e n e r a l i z a t i o n ( 7 7 . 5 % ) t o 1 - o c t a v e t ra n s p o s i t i o n s( 8 5 % f o r B W , 7 5 % f o r F D ) a n d e v e n b e t t e r g e n e r a li z a t io n ( 8 5 % )t o 2 - o c t a v e t ra n s p o s it i on s ( 8 0 % f o r B W , 9 0 % f o r F D ) . A l s o l i k eE x p e r i m e n t 5 , t h e r e w a s n o s i g n i f i c a n t g e n e r a l i z a t i o n ( 5 0 % )f o r 0 . 5 -o c t a v e t r a n sp o s i ti o n s ( 5 0 % f o r b o t h m o n k e y s ) a n d n og e n e r a l i z a t i o n ( 5 0 % ) f o r 1 . 5 - o c t a v e t r a n s p o s i t i o n s ( 4 5 % f o r B W ,5 5 % f o r F D ) .

A n A N O V A s h o w e d a s i g n i fi c a n t e f f e c t a c r o ss t r a in i n g a n dt e s t i n g c o n d i t i o n s , F ( 9 , 1 0 ) = 1 7 . 6, p < . 0 0 1 . P l a n n e d c o m p a r i s o nt e st s ( u si n g t h e A N O V A MSE term) s h o w e d n o s i g n i f i c a n t d i f f e r -e n c e r e l a t i v e t o n a t u r al - s ou n d p e r f o r m a n c e f o r 2 - o c t a v e g e n e r a l i-z a t i o n - - t s ( 1 0 ) = 0 . 9 , 0 . 7 , p > . 4 - - o r 1 - o c t a v e g e n e r a l i z a t i o n ,t s (1 0 ) = 0 . 1 6 , 0 . 0 , p > . 5 , f o r D I F F & S A M E , r e s p e c t i v e l y . B yc o n t r a s t, c o m p a r i s o n s s h o w e d s i g n i f i c a n t d i f f e r e n c e s r e l a t i v e t on a t u r a l- s o u n d p e r f o r m a n c e f o r 1 . 5 - oc t a v e g e n e r a l i z a t i o n mt s (1 0 ) = 5 . 6 , 5. 4 , p < . 0 0 1 - - - a n d f o r 0 . 5 - o c t a v e g e n e r a l i z a t i o n ,t s (1 0 ) = 5 . 6 , 5 . 4 , p < . 0 0 1 , f o r D I F F & S A M E , r e s p e c t i v e l y .

T h e t e s t r e s u l t s f r o m t h e p i t c h t e s t w i t h t r a n s p o s e d n o t e s a r es h o w n i n t h e m i d d l e p o r t i o n o f F i g u r e 7 . R e s u l t s f r o m t h e p i t c h t e sts h o w t h a t w i t h i n c r e a si n g d i s t a n c e ( p it c h ) b e t w e e n t h e s a m p l e a n dt e s t n o t e s, t h e p e r c e n t a g e o f s a m e r e s p o n s e s d e c r e a s e d ( 7 0 % , 5 5 % ,4 5 % , 4 5 % f o r B W ; 8 0 % , 6 0 % , 5 0 % , 4 5 % f o r F D ) . T h i s is am o n o t o n i c a l l y d e c r e a s i n g s i m i l a r i t y ( i n c r e a s i n g d i s c r i m i n a t i o n )e f f e c t . C o m p a r i s o n s t o n a t u r a l - s o u n d t r a i n i n g p e r f o r m a n c e ss h o w e d n o s i g n i f i c a n t d i f f e r e n c e a t 0 . 5 - o c t a v e p i t c h t r a n s p o s i ti o n s ,t ~( 10 ) = 1 .1 , 0 . 9 , p > . 3 , f o r D I F F & S A M E , r e s p e c t i v e l y . O t h e rp i t c h t ra n s p o s i t i o n s w e r e s i g n i f i c a n t l y ( p < . 0 1 ) d i f f e r e n t f r o m

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FigureZ Training performance with natural/environmental soun ds (left), testing performance w ith childhoodsongs (right), and testing performance for pitch o f individual notes taken fro m the childhood songs (middle). Thepercent "SA M E" response is the degree of general izat ion to chi ldhood songs or notes t ransposed 0.5, 1 .0, 1 .5,and 2.0 octaves. DIFF = different.


11/17

MONKEY OCTAVE GENERALIZATIONAND MUSIC PERCEPTION 301natural-sound training performances, ts(10) --- 4.2, 4.1 for 1.0-octave; ts(10) = 6.1, 5.9 for 1.5-octaves; ts(10) --- 6.5, 6.3 for 2.0-octaves, for DIFF & SAME, respectively.

The generalization trends were very different for childhoodsongs than for the individual notes from these songs. At transpo-sitions of six semitones (i.e., to the tritone), melodies were notjudged (50%) to be the same. Paradoxically (relative to individualnotes), increasing the distance, for example by doubling frequency,makes childhood songs more similar. Indeed, it makes them sosimilar that they are judged to be as similar as identical naturalsounds. The trend goes through another inflection as the distanceis further increased to 1.5 octaves. At 1.5-octave separations(transpositions), the melody is judged to be the same only 50% ofthe time. There is another recapitulation with a further separationto two octaves. Childhood songs with note frequency differencesas great as 1,110 Hz (370 to 1,480 Hz for a two-octave transpo-sition) are judged to be the same melody 85% of the time, even aslightly higher percentage than for one-octave transpositions oridentical natural sounds.

These results highlight some differences be tween psychophys-ical disc riminability and gestalt perception, and procedures thatcan influence octave generalization. One conclusion from thisexperiment is that notes, the subunits of a melody, do not result inoctave generalization. This is a conclusion similar to the one basedon octave transposition of notes with humans (e.g., Kallman, 1982)and raises additional concerns over studies claiming to showoctave generalization to pure tones (e.g., Blackwell & Schlosberg,1943). From a gestal t standpoint , these same notes when presentedas melodies configure to overshadow substant ial pitch differencesin the transpositions. Most interesting, on the basis of the evidencewe have presented, is that not all melodies result in octave gener-alization. Only the childhood songs produced octave generaliza-tion, not the random-note synthetic melodies. It now remains toidentify the properties of the melody that makes it a generalizablemelody for rhesus monkeys. This is the topic of the last twoexperiments.

Experiment 7The strong octave generalization for childhood songs of Exper-

iments 2, 5, and 6 contrasts with the lack of octave generalizationfor random synthetic melodies of Experiments 1, 3, and 4. Thechildhood songs were originally selected because they werethought to be musical and memorable by contrast to the syntheticmelodies (el. Trehub, 1993). Certainly one would not expectgeneralization of melodies that could not be remembered. Quan-tifying of musical tonality, however, is complicated. Two ap-proacbes may be relevant.

Key DistanceOne index of tonality is key distance on a scale of the circle of

fifths (e.g., Bartlett, 1993). Beginning with the note C, successivefifths (7 semitone steps) produces the series C, G, D, A, E, B, F#,C#, G-#, D#, A#, F, which is joined in a circle. Adjacent notes arestructurally, musically, and tonally related for infant s (Schellen-berg & Trehub, 1996) as well as adults (Bartlett, 1993; Takeuchi& Hulse, 1992). Take, for example, a melody in the key of Cmajor. The tonic , C, forms a point of departure and arrival. The

note, G, is a "perfect" fifth (3/2 frequency ratio) above the tonicand is the secondary point of arrival. The perfect fifth above thenote of G is D, and so on. Adjacent notes (e.g., C and G) are moststrongly tonal ly related. Notes on opposite sides of the circle (e.g.,B and F ~) are least related. The childhood songs and syntheticmelodies were analyzed for key distance with fewer steps (on thecircle of fifths) indicating stronger tonality. The mean intervalbetween notes (on the circle of fifths) was 2.71 steps for childhoodsongs and 3.06 steps for synthetic melodies. This difference, whilenot large, is in the same direction as the octave-generalizationresults. The smallest range (on the circle of fifths) is also related totonal ity (Bartlett, 1993; Bartlett & Dowling, 1988). The total rangewas 5.16 steps for childhood songs and 6.80 steps for syntheticmelodies, which is also in the same direction as the octave-generalization results. A more thorough evaluation of these circle-of-fifths measures as they relate to octave generalizat ion is pre-sented in the General Discussion section.

Maximum Key Profile Correlation (MKC)The ultimate goal of indexing tonality would seem to be an

algorithm whereby musical passages could be varied along acontinuum of tonality. At one extreme a melody would be atonal(like the random synthetic melodies) and at the other extreme amelody would be tonal (like the childhood songs). Takeuchi(1994) has supplied jus t such an algorithm. This algori thm useshuman judgments of the stability of indiv idual pitch classes in atonal context of a particular key (Krumhansl & Kessler, 1982). Inthe key of C major, for example, the perfect fifth, G, as well as thetonic, C, are judged highly stable and occur frequently. On theother hand, the tritone, F ~, is judged unstable in C major and istherefore unlikely to occur. Krumhansl (1990) presents the list ofstability ratings for scale values in the key o f C major.

The Takeuchi MKC index is based on the evidence that the moststable pitch classes (i.e., the tonic , the perfect fifth, etc.) occurmost often in the musical passage. The more frequently they occur,the more the key is established, and the more tonal is the musicalpassage. The MKC algorithm correlates the frequency of the 12pitch classes (scale values) with the stabil ity of the 24 possiblemajor and minor key profiles. The largest correlation identifies themost likely key and indexes tonality.

The mean MKC tonali ty values for the childhood songs and therandom-synthetic melodies of this article was 0.69 and 0.57, re-spectively. This difference in tonality values is in the same direc-tion as the difference in octave generalization for these melodies.The MKC tonality algorithm can also be used to select themelodies to be tested. The purpose of Experiment 7 was to testmelodies that were generated using the MKC tonality algorithm sothat tonal and atonal melodies would be related on the samecontinuum. A secondary purpose of Experiment 7 was to evaluatethe role of rhythm in octave generalization. Although rhythmicstructure has little or no effect on human octave generalization(Massaro et al., 1980), rhythm and rhythm differences werepresent in the childhood songs. Therefore, the tonal and atonalmelodies in Experiment 7 (and Experiment 8) were isochronouswith notes and inte rnote intervals of the same duration.


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3 0 2 W R I G H T , R I V E R A , H U L S E , S H Y AN , A N D N E I W O R T HM e t h o d

Sub jec t s and Appara tusThe subjects and apparatus were the same as in previous experiments .

S t imu l iTh ere w e re 2 4 t o n a l an d 2 4 a t o n a l me l o d ie s . Tw e l v e o f each t y p e w ere

used in t ra in ing and the o ther 12 in test ing . Each melody contained sevenn o t e s o f 2 5 0 m s each . A l l m e l o d i e s w e re reco rd ed w i t h t h e same k ey b o a rdinst rument . The a tonal melodies were se lected so that they contained twoo r t h ree p i t ch -co n t o u r ch an g es an d h ad M K C t o n a l it y v a l u es o f l e s sthan 0 .57 , re su l t ing in a range of 0 .57 to 0 .32 . Al tho ugh one canno t say thatan a t o n a l me l o d y i s t ru l y i n an y k ey , t h e K ru mh an s l an d K ess l e r (1 9 82 )key-finding a lgori thm does indicate the most l ikely key . The most l ikelyk ey o f t h e a t o n a l me l o d i e s w as i d en t i fi ed to m ak e t o n a l me l o d i e s f ro m t h eatonal melodies . Certa in notes were then modified , but the orig inal con-tours of the m elodies were preserved . In cases where the f 'wst or last notesw ere w h o l e t o n es o r semi t o n es remo v ed f ro m t h e t o n i c , t h e se n o te s w e rechanged to the tonic . Tri tones were changed to the perfect f i f th . There su l ti n g to n a l me l o d i e s h ad MK C v a l u es o f g rea t e r t h an 0 .7 5 w i t h a ran g eof 0 .75 to 0 .93 . The melodies were from the three-octave range usedpreviously .

P r o c e d u r eTh e t ra i n i n g p ro ced u re w as s i mi l a r t o t h a t o f p rev i o u s ex p e r i men t s .

There w ere 26 natural -s t im ulus t ra in ing t r ia l s and one tonal and one a tona lt ra in ing t r ia l per session . There were 12 d i fferent tonal and 12 d i fferenta tonal melodies used in t ra in ing . Melodies were presented once as samplefrom the center speaker and I- 3 t imes from side speakers , depending onwhe n the choice response occurred. Sam e and different re sp o n ses w e rerew ard ed acco rd i n g t o w h e t h e r t h e t w o s t i mu l i (n a t u ra l so un d s o r me l o -d ies) were ident ical or d i fferent , respect ively .

There were two test t r ia l s each session . There were 12 d i fferent a tonaland 12 d i fferent tonal melodies used in test ing . Test me lodies were d i ffer-en t i n co n t o u r f ro m t ra i n i n g me l o d i e s . T ran sp o s i ti o n s w e re o n e o c t av e . Th edi rect ion of t ransposi t ion (to h igher or lower frequencies) was d i fferent onthe two test t r ia l s each session . St imulus pai rings an d t r ia l sequences varieddai ly and were counterbalanced wi th in the l imi ts of the experiment . The

melodies were tested in two rando mized b locks for a to ta l of 24 sessions inthe experimenL

On test t r ia l s , e i ther response (same~different)w as rew ard ed w i t h t h ereward pro babi l i ty equal to the su bject ' s t ra in ing-t r ia l accuracy from theprevious session .

Resu l t s and D i scuss ionT h e r e s u l ts a r e s h o w n i n F i g u r e 8 . T r

Music Perception and Octave Generalization in Rhesus Monkeys - Wright Et Al 2000

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