Social learning of a communicative signal in captive chimpanzees

Abstract

The acquisition of linguistic competency from more experienced social partners is a fundamental aspect of human language. However, there is little evidence that non-human primates learn to use their vocalizations from social partners. Captive chimpanzees (Pan troglodytes) produce idiosyncratic vocal signals that are used intentionally to capture the attention of a human experimenter. Interestingly, not all apes produce these sounds, and it is unclear what factors explain this difference. We tested the hypothesis that these attention-getting (AG) sounds are socially learned via transmission between mothers and their offspring. We assessed 158 chimpanzees to determine if they produced AG sounds. A significant association was found between mother and offspring sound production. This association was attributable to individuals who were raised by their biological mother-as opposed to those raised by humans in a nursery environment. These data support the hypothesis that social learning plays a role in the acquisition and use of communicative vocal signals in chimpanzees.

Figure 1.

Concordance between mother and offspring for AG sound production (*p = 0.012).

Figure 2.

AG sound types for mother-reared subjects whose mothers are also AG+ (n = 19). AG sounds are classified based on the descriptions in table 1. Note that two subjects (offspring) produced two types of AG during their vocal assessments, RS and EG. The mothers of both subjects produced RS. Both subjects were included in our analysis as concordant for vocal type with their mother. Light grey bars denote AG+ offspring with mothers that produce same AG sound type and dark grey bars denote total offspring (AG+) that produce each AG sound type.