Sequence organization of mother–infant interactions in chimpanzees ( Pan troglodytes schweinfurthii ) in the wild

Sequence organization is a fundamental feature of human communication, shaping our interactions. This organization underlies interactions with and without language, appears early in human development and is even hypothesized to precede language itself. However, remarkably little is known about the evolutionary origins of the sequence organization of interactions. Here, we investigated the sequence organization of mother–infant interactions in one of our closest living relatives, the chimpanzee ( Pan troglodytes ). We focused our study on two components of sequence organization: (i) adjacency pairs around turn transitions and (ii) flexibility on an interactional scale. In total, 361 communicative interactions containing 3647 signals and actions in 17 mother–infant dyads living in the Ngogo population, Uganda, were collected and analysed. The results showed that on a two-turn scale, a large proportion (42%) of turn transitions are non-randomly combined into potential adjacency pairs. Regarding flexibility, a conditional transition network revealed eight highly distinguished clusters of flexibly used units. With this consilience of methods, we show that, like humans, interactions of chimpanzees are sequentially organized, strengthening the hypothesis that sequence organization is indeed a fundamental feature of communication pre-dating the evolution of language.