Genetic & Experiential Influences On Vocal Development

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This and a companion project (Z01 HD001123-13) investigate auditory communication in primates. The overall goal of these studies is to provide a comprehensive understanding of primate auditory communication in terms of development, neural mechanisms, endocrine factors, and social context. Two species, the squirrel monkey and the common marmoset, are the main subjects of study, with additional data collected from other species where appropriate. The present project studies primate communication from a bioacoustic and ethological perspective, focusing on the detailed acoustic structure of vocalizations produced in natural settings, and the relationship of structural differences to differences in age, gender, experience and response selectivity, as well as the broader factors of social context and genetic background. New findings focused on the perceptual side of auditory communication, using playback techniques to examine perceptual preferences as measured by vocally responding to the stimulus. A long-distance affiliative vocalization, the isolation peep, was tested for responsiveness to species-specific differences in the acoustic details. Isolation Peeps from 2 species of squirrel monkey (Saimiri sciureus and S. boliviensis) were digitized, then entered into a library for use as playback stimuli. Eight acoustic parameters of each call were measured, and these parameters entered into a discriminant function analysis to determine whether a given call represented a weak, typical or extreme variant of one or the other species' calls. A total of 432 calls were selected as playback stimuli. Four social groups, 2 groups of each of the 2 species, were chosen as subjects. Subjects were tested in an outdoor run and were presented with 12 stimulus trials and 4 control (no stimulus) trials per session. Sessions were run daily. Three of the 4 groups have been tested, to date. The two groups of S. sciureus called to playback stimuli of both species, hence did not show species selectivity. However, the group of S. boliviensis did show a statistically significantly greater tendency to vocally respond to their own species' calls, if the response measure was antiphonal isolation peeps from group members. Future work will attempt to resolve the underlying mechanism that appears to impart different sensory biases to the 2 closely-related species under study.