A comparative study of the perception of species-specific communication sounds by Japanese macaques (Macaca fuscata) and other Old World monkeys

Abstract

An attempt is being made to psychophysically characterize the Japanese macaque's perception of sounds drawn from its vocal communication system. In the course of constructing a vocal ethogram for this species, Green (Primate Behavier 4, 1–101 (1975)] identified several distinct classes of vocalizations which differ in acoustic structure and form as well as the sociobehavioral context in which they are likely to occur. Six fuscata and three control (non-fuscata) monkeys have been operantly conditioned, via positive reinforcement techniques, to discriminate between two different types of vocal sounds from Green's classification scheme—the smooth early (SE) and smooth Late (SL) highs. While contacting a metal operandum with its hand an animal is presented a series of natural exemplars from the SL class. Occasionally, and randomly, an exemplar from the SL class is inserted into the series. If the animal correctly reports detection of the SE by breaking contact with the operandum it receives a food pellet. Results from several experiments employing this general procedure will be discussed including studies of perceptual constancy, selective attention, and the classification of synthetic versions of these communication signals. One important and consistent finding is that, although the fuscata and control animals have basically the same auditory capabilities, their perception of the communication sounds, at least during acquisition of the discrimination, differs: the fuscata seem to attend to the communication-relevant features of the sounds while the controls appear to attend predominantly to the communication-irrelevant aspects of the stimuli. [Supported by NSF Research Grants BMS 74-20050 and 5-27092, NINCDS Program Project Grant NS 5785, and NIGMS Training Grant GM-01789.]