The primate roots of human language: Primate vocal behaviour and cognition in the wild

Our research describes the natural communication in different primates, as well as their underlying cognitive abilities. We are interested in the communication skills and social cognition of monkeys and apes in their natural habitats. For this purpose, we observe wild groups in Africa and Asia during their daily activities in order to understand what communication signals they are able to produce, under what circumstances they produce them, and what sorts of responses they elicit from listeners. Once we have gathered enough information to suspect a relationship between a particular call type, a set of events and a typical response, we conduct a field playback experiment to determine the call's meaning. During such an experiment we play back a recorded example of a particular call to a naïve receiver in order to study its response. For example, chimpanzees produce different types of food grunts depending on the type of food they find, such as apples or bread. We found that these calls were indeed meaningful to other chimpanzees. For instance, if we played back recordings of 'apple grunts' listeners were more likely to look for food in places where they previously found apples, but not bread, and vice versa. In another study, we found that some monkeys are able to combine some of their vocalizations in systematic ways to create different combinations with separate meanings. Our playback experiments showed that it was the combinations of calls, rather than the individual calls themselves, which carried the meaning, an example of simple primate 'grammar'.