INFANTS’ PERCEPTION OF CONSONANCE AND DISSONANCE IN MUSIC Marcel R. Zentner’ Jerome Kagan Harvard The origins of the perception of consonance and dissonance in music are a matter of debate. The present study examined the hypothesis of an innate preferential bias favoring consonance over dissonance by exposing 4 month old infants to consonant and dissonant versions of two melodies. Infants looked signif- icantly longer at the source of sound and were less motorically active to consonant compared with disso- nant versions of each melody. Further, fretting and turning away from the music source occurred more frequently during the dissonant than the consonant versions. The results suggest that infants are biologi- cally prepared to treat consonance as perceptually more pleasing than dissonance. INTRODUCTION a combination of two or more frequencies occuring simultaneously. When the combina- The possibility of perceptual universals in tion is experienced as pleasant, the sound is music has been a question of interest for a long classified as consonant. When the combination time. After many centuries of speculative of frequencies is experienced as unpleasant, debate this question is now being empirically the sound is judged as dissonant. This can be addressed. The study of infants represents one illustrated with the simple example of the way to explore musical universals. This interval. An interval is a combination of two research investigates the hypothesis of an tones of different frequencies. The difference innate bias for consonance over dissonance. in frequencies between the two tones of an Consonance and dissonance refer to the interval, also refered to as interval size, is often subjective judgement of a listener, exposed to expressed as either semitones or multiples of l Marcel R. Zentner, Department of Psychology, University of Geneva, 9 Rte de Drize, CH-1227 Geneva-Carouge; e-mail: [email protected]. INFANT BEHAVIOR & DEVELOPMENT 21 (3), 1998, pp. 483-492 ISSN 0163-6383 Copyright 0 1998 Ablex Publishing Corporation All rights of reproduction in any form reserved. 484 INFANT BEHAVIOR & DEVELOPMENT Vol. 21, No. 3, 19%) semitones. The semitone is the smallest differ- dyadic intervals, put forward by Helmholtz ence in Western musical scales and corre- (,1954), is that tone pairs are judged consonant sponds to a frequency ratio of the two tones of when the maximum number of upper harmon- approximately 1 .06.2 ics match. Harmonics are the frequency values Although consonance and dissonance have of individual pure-tone components. These been described as refering to a subjective harmonics are usually integer multiples of the experience, adults asked to rank intervals in fundamental frequency. For example, a com- accord with their pleasantness, produce similar plex tone with a fundamental frequency of 100 results across varied studies. These studies Hz has of upper harmonics of 100, 200, 300, have been reviewed by Schellenberg and Tre- 400,500 Hz, and so on. To maximize the num- hub (1994). Adults judge as most consonant ber of matching harmonics, the frequency either the octave (difference of 12 semitones), ratios between the fundamentals should be the fifth (7 semitones), or the major third (4 expressible as a ratio of small whole numbers semitones). Adults judge as most dissonant the (2:1, 3:2, 4:3, 5:4, 65 etc.). Figure 1 presents minor second (difference of 1 semitone). the example of three intervals with decreasing These robust facts suggest a lawfulness to the degrees of consonance as a function of judgement of consonant or dissonant intervals. decreasing This regularity has motivated a search for the objective acoustic properties that character- Plomp and Levelt ize consonance and dissonance. A popular (1965) who defined a critical band for two explanation of consonance and dissonance of pure sinusoidal waves as the minimum fre- - 1 5 6 6 6 5 5 4 5 4 4 4 3 3 3 3 2 2 ‘t2 Pl - p1 I ‘f2 fifth major third minor! second highly consonant consonant highly dissonant Matches at: MatchI at: No match 3:2 5:4 6:4 FIGURE 1 The upper harmonics of representative musical intervals and their superposition. Matches of upper har- monics are bold. Consonance and Dissonance 485 quency separation between them that does not cross-cultural studies is scant and ambiguous. give rise to dissonant effects. The critical band Consonance judgements were invariant among is roughly a little lower than a minor third (3 Americans and Japanese (Butler & Daston, semitones). This means that, for pure sounds, 1968), but dissimilar among Canadians and any interval except a full tone (2 semitones) is Indians. Indians showed greater tolerance not dissonant. This generalization does not toward dissonant intervals (Maher, 1976). hold for more complex sounds because they Hence, the cross-cultural study of consonance may have pairs of upper harmonics that fall in preferences has not yet proved to be informa- the critical band. The theory implies that com- tive. Although additional evidence would be of plex tones related by complex frequency ratios interest, it is difficult, if not impossible, to find are more likely to give rise to dissonant effects cultures that are totally isolated from Western not because of the complexity of frequency music. ratios in itself but because of the greater num- A second strategy is to study the reactions ber of overlapping critical bands among adja- of animals to consonance and dissonance. cent harmonics that characterizes intervals Borchgrevink (1975) examined such conso- with complex frequency ratios. nance preferences in 34 albino rats. He con- Although Helmholtz and later physicists nected a tape recorder to a test chamber believed that consonance judgments were the containing a loudspeaker and two pedals. psychological result of physical-acoustical When the rat pressed one pedal a consonant laws operating on inborn properties of the chord was heard, pressing the other pedal was auditory system (Plomp & Levelt, 1965; Ter- followed by a dissonant chord (unfortunately, hardt, 1984), there is, at present, no proof of the chords were not specified in the article). this biological preparedness. One could argue The association between the consonant and that psychoacoustic laws, as posited by Helm- dissonant chords and the position of the pedals holtz and others, could reflect an acquired, was randomly distributed among animals. rather than an inborn, form of auditory pro- Each rat spent 15 min a day in the test chamber cessing. Indeed, some investigators have in a stipulated sequence for three weeks. A argued that consonance judgments are preference for each animal was defined as the acquired competences based on exposure to difference between the number of presses on the music of a particular culture (Frances, the two pedals. The results show that the rats 1988; Lundin, 1985). This view is popular developed a consonance preference. After an among modern music theorists and composers initial period of small and unreliable differ- who adopt a sceptical stance toward an abso- ences, the number of presses on the conso- lute notion of consonance (e.g. Boulez, 1971). nance producing pedal increased, and was at This “nurture” view can be traced to Schdn- the end almost twice the number of presses on berg’s declaration that the concept of conso- the dissonance producing pedal (Borchgre- nance has no useful meaning. Not only did vink, 1975). Although a generalization from Schiinberg proclaim the “emancipation of dis- rats to humans is speculative-and the prior sonance,” but he also proscribed an elimina- musical experience of the rats is not known- tion of consonances (Schonberg, 1984). this study provided support for a possible bio- Different strategies can be chosen to probe logical basis for consonance preference. the origins of our perception of consonance In a more recent study European Starlings and dissonance. One strategy is to compare (Sturnus Vulgaris) were trained to peck at one judgments of subjects from cultures with dif- key when a consonant chord was presented ferent musical systems. If consonance judg- and at another key when a dissonant chord was ments are primarily a function of exposure we presented. The birds generalized the response should find variability in judgments across cul- to a new pair of consonant and dissonant tures. Unfortunately, evidence from such chords (Hulse, Bernard & Braaten, 1995). This 486 INFANT BEHAVIOR & DEVELOPMENT Vol. 21, No. 3,1998 result suggests that consonance and disso- The present experiment was designed spe- nance may be an important cue for auditory cifically to test the hypothesis of an innate communication among songbirds. preferential bias favoring consonance over dis- The problems with conducting cross-cul- sonance. Unlike studies that used isolated pairs tural studies and the interpretation of animal of intervals, infants were presented with actual work motivate a search for other strategies. music. Two different, unfamiliar melodies The study of young infants provides an oppor- were composed with a synthesizer, and a con- tunity for the exploration of auditory predispo- sonant and dissonant version was created for sitions in humans. Although there is a body of each melody. Because our interest was in the literature on infants’ music perception, studies infants’ preference, and not in perceptual capa- typically focused on infants’ processing capa- bility, the dependent measures of visual fixa- tion of the music source, motor activity, bilities rather than preferences and/or affective vocalization, fretting and turning away from responses (Trehub & Trainor, 1993). More- the music source were all coded as relevant over, these studies of infants’ interval percep- indicators. It was expected that the infants tion have examined responses to melodic would be more attentive and show less fre- intervals where tones are presented succes- quent signs of distress to the consonant com- sively, rather than harmonic intervals where pared to the dissonant melodies. tones are presented simultaneously. One of the exceptions is a study by Crow- der, Reznick and Rosenkrantz (1991) origi- METHOD nally designed to test 6 month-old infants’ reactions to major and minor chords.