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
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.
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
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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.
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