Semiotic combinations in Pan: A comparison of communication in a chimpanzee and two bonobos

Communicative combinations of two bonobos (Pan paniscus) and a chimpanzee (Pan troglodytes) are compared. All three apes utilized ordering strategies for combining symbols (lexigrams) or a lexigram with a gesture to express semantic relations such as agent of action or object of action. Combinatorial strategies used by all three apes revealed commonalities with child language, spoken and signed, at the two-year-old level. However, many differences were also observed: e.g., combinations made up a much smaller proportion and single symbols a much larger proportion of ape production compared with child production at a similar age; and ape combinations rarely exceeded three semiotic elements. The commonalties and differences among three sibling species highlight candidate combinatorial capacities that may underlie the evolution of human language.