ABSTRACT
Frequency modulation seems to be a common feature of sounds that are used in communication by most species. That is true for human language, for the coo contact calls uttered by Japanese macaques, and for the signals of rodents. In a series of experiments they describe in this chapter, Moody and Stebbins have set out to study the characteristics of frequency modulated stimuli when they must be discriminated from unmodulated stimuli near threshold. The experiments are designed to determine not just what monkeys do perceive about frequency modulated calls, but what they can perceive about such calls—especially when the calls are modified systematically. Only by analytic procedures of this type can we determine in a more general sense the factors that govern acoustic perception.
