Music perception and octave generalization in rhesus monkeys

Anthony A. Wright*, Jacquelyne J. Rivera*, Stewart H. Hulse‡, Melissa Shyan§, Julie J. Neiworth&

J Exp Psychol Gen, 2000 Sep, Vol 129 No 3, 291-307

*Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, PO Box 20708, Texas 77225
‡Department of Psychology, Johns Hopkins University; §Department of Psychology, Butler University; &Department of Psychology, Carleton College


Two rhesus monkeys were tested for octave generalization in 8 experiments by transposing 6- and 7-note musical passages by an octave and requiring same or different judgments. The monkeys showed no octave generalization to random-synthetic melodies, atonal melodies, or individual notes. They did show complete octave generalization to childhood songs (e.g., "Happy Birthday") and tonal melodies (from a tonality 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 combine to show that tonal melodies form musical gestalts for monkeys, as they do for humans, and retain their identity when transposed with whole octaves so that chroma (key) is preserved. This conclusion implicates similar transduction, storage, processing, and relational memory of musical passages in monkeys and humans and has implications for nature-nurture origins of music perception.
(Bold text emphasis by Martin Braun)


The results of this comprehensive and carefully conducted study must be called groundbreaking in two respects. They show for the first time that members of a non-human species perceive music in a very similar way as humans. The similarity concerns chroma repetition (also called octave equivalence) and harmonicity of melodies (the particular quality of melodies in which the main intervals are consonant ones, as in almost all songs). The implications of these findings are that the auditory brain in humans, and in other species, is genetically determined to develop the abilities to perceive these musical qualities of sound. The new indication that chroma repetition apparently is innate agrees with its universal occurrence across music cultures. Further, anatomical and physiological data suggest that the origin of the octave effect lies in a particular frequency map of the mammalian auditory thalamus that is organized in octave layers (see references below). The fact that the monkeys recognized octave-transposed childhood songs and other, mathematically generated, harmonic melodies - but not inharmonic ones - is even more remarkable. It implies that the human preference for harmonic (low-order ratio) intervals in melodies apparently has a strong biological component.
(Comment Martin Braun)


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Morel, A., 1980. Codage de sons dans le corps génouille médian du chat: évaluation de l'organisation tonotopique de ses différents noyaux. Thèse de l'Université de Lausanne, Faculté des Sciences, Janis Druck und Verlag, Zürich, pp. 1-154.

Imig, T.J., Morel, A., 1985. Tonotopic organization in ventral nucleus of medial geniculate body in the cat. J Neurophysiol 53, 309-340. (Note data series from electrode penetration P1 in their Figs. 6 and 7 showing stepwise frequency representation with discrete clusters around 0.6, 1.2, and 2.4 kHz)

Cetas, J.S., Velenovsky, D.S., Price, R.O., Sinex, D.G., McMullen, N.T., 2001. Frequency organization and cellular lamination in the medial geniculate body of the rabbit. Hear. Res. 155, 113-123.

Cetas, J.S., Price, R.O., Velenovsky, D.S., Crowe, J.J., Sinex, D.G., McMullen, N.T., 2002. Cell types and response properties of neurons in the ventral division of the medial geniculate body of the rabbit. J. Comp. Neurol. 445, 78-96.

Cetas, J.S., Price, R.O., Crowe, J.J., Velenovsky, D.S., McMullen, N.T., 2003. Dendritic orientation and laminar architecture in the rabbit auditory thalamus. J. Comp. Neurol. 458, 307-317.

Physiolgical evidence of hard-wired octaves in humans

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