Oral Presentation (5) February 20

I examined whether monkeys perceptually segregate tone sequences. Subjects were 5 Japanese macaques (Macaca fuscata) including two females (H, 9 years old; K, 8 years old) and three males (I, 8 years old; L and M, 5 years old). A go/no-go procedure was used with positive reinforcement operant conditioning. Monkeys were required to discriminate two sequences of tones (target sequences). The target sequences consisted of the same frequency component but were different in frequency contours. One of the sequences repeated continuously four times for each presentation of the stimulus. In some conditions, distracter sequences were presented simultaneously with the target sequences. Monkeys could discriminate the sequences when the frequency ranges of the target and distracter sequences did not overlap, but they could not when the ranges overlapped. In subsequent probe tests, the starting positions of the target sequences were altered to test whether the monkeys discriminated the sequences by the cues other than local pitch of the component tones. Monkeys discriminated the sequences with novel starting positions as well as the trained sequences. These results suggest that monkeys segregate tone sequences based on frequency proximity, and they perceive global characters of the segregated streams.

IZUMI, Akihiro
Cognition and Learning Section,
Primate Research Institute, Kyoto University
Inuyama, Aichi 484-8506, Japan
aizumi@pri.kyoto-u.ac.jp