Perception of sensory consonance of chords in Japanese monkeys

Akihiro Izumi

Kyoto University, Japan

Consonance/dissonance affects human perception of chords from early stages of development (e.g., Schellenberg & Trainor, 1996). In non-human animals, a songbird species were tentatively suggested to discriminate chords by the sensory consonance of stimuli (Hulse, Bernard & Braaten 1995). To systematically examine whether consonance have some role in audition of non-humans, three Japanese monkeys (Macaca fuscata) were trained to discriminate simultaneous two-tone complexes (chords). The task was serial discrimination (AX procedure) with repetitive presentation of background stimuli. Each tone in a chord comprised of six harmonics, and intervals with complex frequency ratios of fundamental frequency (e.g. frequency ratio of 8:15 in major seventh) resulted in sensory dissonant. The chords were transposed for each presentation to make monkeys attend cues other than the absolute frequency of a component tone. Monkeys were initially trained to detect changes from consonant (octave) to dissonant (major seventh). Following the successful acquisition of the task, transfer tests with novel intervals were conducted. In these transfer tests, the performances with detecting changes from consonant to dissonant (perfect fifth to major seventh; perfect fourth to major seventh) were higher than that with detecting reverse changes. These results suggested that the discriminations of monkeys depended chiefly on the consonance / dissonance of chords.

Hulse, S. H., Bernard, D. J., & Braaten, R. F. (1995). Journal of Experimental Psychology: General, 124, 409-423.

Schellenberg, E. G., & Trainor, L. J. (1996). Journal of the Acoustical Society of America, 100, 3321-3328.

Izumi, Akihiro

Section of Cognition and Learning, Primate Research Institute, Kyoto University

Inuyama, Aichi 484-8506, Japan

aizumi@pri.kyoto-u.ac.jp