BEHAVIORAL MECHANISMS UNDERLYING VOCAL COMMUNICATION IN NONHUMAN-PRIMATES

In the wild, nonhuman primate vocalizations signal the presence of dif ferent predators, provide information about the group's location and m ovement, facilitate friendly interactions, and lead to reconciliation between individuals who have recently exchanged aggression. Current re search examines the mechanisms that underlie such communication. Playb ack experiments demonstrate that subjects treat vocalizations as seman tic 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 movemen t are given by baboons only when they themselves are lost; individuals at the group's center apparently do not call to inform peripheral ani mals of their location. Calls that lead to reconciliation are best exp lained by assuming that callers and recipients have learned, through e xperience, that a vocalization is rarely followed by aggression and of ten followed by friendly behavior. The inability of animals to recogni ze what other individuals know, believe, or desire constitutes a funda mental difference between nonhuman primate vocal communication and hum an language.