The significant features of Japanese macaque coo sounds: a psychophysical study

Brad May, David B. Moody, William C. Stebbins

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Japanese macaques, Macaca fuscata, were trained with a positive reinforcement operant procedure to discriminate smooth early high and smooth late high coo sounds recorded during Green's (1975) field study of the speices' vocal repertoire. Subjects labelled the various tokens by maintaining contact with a response device for calls from one category and by breaking contact for those of the second call type. After the completion of discrimination training, the generalization of the operant behaviour to novel natural and synthetic vocalizations was measured. Initial generalization tests established that macaques would respond appropriately both to natural vocalizations and to computer-synthesized prototypes representing the smooth early high-smooth late high contrast. In subsequent tests, individual acoustic features were removed from the synthetic prototypes to determine the minimal elements of functional coo sounds. These tests suggested that those sounds are distinguished by the predominant direction of their frequency change which, in turn, is determined by the temporal position of their highest frequency.

Original languageEnglish (US)
Pages (from-to)1432-1444
Number of pages13
JournalAnimal Behaviour
Issue number5
StatePublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


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