Bonobo Communication Shows Human-Like Linguistic Compositionality

Bonobos exhibit a communication style featuring compositionality, a linguistic trait previously considered unique to humans. A study published in *Science* indicates that bonobos combine calls in ways that mirror the complex structure of human language. Linguists categorize compositionality into simple and nontrivial forms. While some animals demonstrate simple compositionality (combining words with specific meanings), bonobos appear to engage in nontrivial compositionality, where certain elements modify others. This adds nuance and complexity to conveyed meaning, according to Simon Townsend from the University of Zurich. Mélissa Berthet, from Townsend's group, recorded bonobo calls in the Kokolopori Bonobo Reserve, Democratic Republic of the Congo, categorizing them as "peeps," "whistles," "grunts," and "yelps." She documented contextual details for 700 recordings, inferring call meanings based on context. "Peeps" coordinate activities, while "whistles" maintain group cohesion. Researchers mapped calls on a five-dimensional "map" of meaning, creating a "dictionary" of seven common calls. Analysis of call combinations revealed "peep-whistles," used in sensitive social interactions, exemplify nontrivial compositionality. Four combinations showed compositionality, with three exhibiting meaning beyond the sum of their parts. All seven call types appeared in combinations, indicating extensive compositionality. While the precise meaning of "bonobospeak" remains unclear, the method, derived from human linguistics, suggests nontrivial compositionality. Shane Steinert-Threlkeld from the University of Washington suggests combined calls could be idioms. Thom Scott-Phillips from Central European University questions the comparability of bonobo calls to language, citing similar signaling in bacteria. Townsend suggests nontrivial compositionality may be widespread. He hopes their observational approach will encourage testing in other species to determine if bonobos are unique in this capacity.