Humans are the only species on Earth known to use language. They do this by combining sounds into words and words into sentences, creating infinite meanings.

The study reveals four ways in which chimpanzees alter meanings when combining single calls into 16 different two-call combinations, analogous to the key linguistic principles in human language.

Chimpanzees used compositional combinations that added meaning (e.g., A = feeding, B = resting, AB = feeding + resting) and clarified meaning (e.g., A = feeding or traveling, B = aggression, AB = traveling). They also used non-compositional idiomatic combinations that created entirely new meanings (e.g., A = resting, B = affiliation, AB = nesting).