Abstract: Following aggressive interactions, dominant female baboons, Papio cynocephalus ursinusoccasionally grunt to their victims. To examine the effect of these apparently reconciliatory grunts on victims' subsequent behaviour, a series of playback experiments was designed to mimic reconciliation. Victims were played their opponents' grunts in the minutes immediately following a fight and then observed for half an hour. After hearing these grunts, victims approached their former opponents and also tolerated their opponents' approaches at significantly higher rates than they did under control conditions. They were also supplanted by their opponents at significantly lower rates. By contrast, playbacks of control females' grunts did not influence victims' behaviour. Playbacks of reconciliatory grunts did not increase the rate at which opponents approached or initiated friendly interactions with their former victims. Playbacks of reconciliatory grunts, therefore, appeared to influence victims', but not opponents', perception of recent events.

Abstract: Historically, a dichotomy has been drawn between the semantic communication of human language and the apparently emotional calls of animals. Current research paints a more complicated picture. Just as scientists have identified elements of human speech that reflect a speaker's emotions, field experiments have shown that the calls of many animals provide listeners with information about objects and events in the environment. Like human speech, therefore, animal vocalizations simultaneously provide others with information that is both semantic and emotional. In support of this conclusion, we review the results of field experiments on the natural vocalizations of African vervet monkeys, diana monkeys, baboons, and suricates (a South African mongoose). Vervet and diana monkeys give acoustically distinct alarm calls in response to the presence of leopards, eagles, and snakes. Each alarm call type elicits a different, adaptive response from others nearby. Field experiments demonstrate that listeners compare these vocalizations not just according to their acoustic properties but also according to the information they convey. Like monkeys, suricates give acoustically distinct alarm calls in response to different predators. Within each predator class, the calls also differ acoustically according to the signaler's perception of urgency. Like speech, therefore, suricate alarm calls convey both semantic and emotional information. The vocalizations of baboons, like those of many birds and mammals, are individually distinctive. As a result, when one baboon hears a sequence of calls exchanged between two or more individuals, the listener acquires information about social events in its group. Baboons, moreover, are skilled “eavesdroppers:” their response to different call sequences provides evidence of the sophisticated information they acquire from other individuals' vocalizations. Baboon males give loud “wahoo” calls during competitive displays. Like other vocalizations, these highly emotional calls provide listeners with information about the caller's dominance rank, age, and competitive ability. Although animal vocalizations, like human speech, simultaneously encode both semantic and emotional information, they differ from language in at least one fundamental respect. Although listeners acquire rich information from a caller's vocalization, callers do not, in the human sense, intend to provide it. Listeners acquire information as an inadvertent consequence of signaler behavior.