Response of nonhuman animals to speech and to species-specific sounds.

Three questions relate to how nonhuman species respond to speech and species-specific sounds: (1) Do nonhuman species perceive human speech in a human-like fashion? (2) How do nonhuman species perceive their own vocalizatios? and (3) How does human perception of animal sounds differ from the animals' perception of those sounds? Four methodologies are available for studying an animal's perception of sounds: (1) discriminative conditioning; (2) habituation-dishabituation; (3) playbacks in captivity; and (4) playbacks in situ. Each of these techniques has a different degree of ecological validity and has different intrinsic biases toward the conclusions one might draw. Experiments using these methodologies for each of the three questions are reviewed and the methodological problems of each are discussed. A two-stage model of perceiving species-specific sounds is presented which accounts for both categorical perception of sounds and within category discrimination of sounds.