Behavioral mechanisms underlying vocal communication in nonhuman primates

In the wild, nonhuman primate vocalizations signal the presence of different predators, provide information about the group’s location and movement, facilitate friendly interactions, and lead to reconciliation between individuals who have recently exchanged aggression. Current research examines the mechanisms that underlie such communication. Playback experiments demonstrate that subjects treat vocalizations as semantic signals, in the sense that they compare signals according to their referents and not just their acoustic properties. Results provide no evidence, however, that subjects recognize one another’s mental states. Calls that provide information about the group’s location or movement are given by baboons only when they themselves are lost; individuals at the group’s center apparently do not call to inform peripheral animals of their location. Calls that lead to reconciliation are best explained by assuming that callers and recipients have learned, through experience, that a vocalization is rarely followed by aggression and often followed by friendly behavior. The inability of animals to recognize what other individuals know, believe, or desire constitutes a fundamental difference between nonhuman primate vocal communication and human language.