Compositional structures in chimpanzee gestural communication

• Applicant: Professorin Dr. Katja Liebal
• Subject Area: Evolution, Anthropology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502020913

Compositionality is the ability to combine meaningful elements (i.e. morphemes and words) into new combinations with novel meanings, and it has long been considered one of the main hallmarks of human communication. To date, however, very few studies have addressed the compositional aspects of communication in species other than humans. In this project, we will trace back the evolutionary origins of human compositionality in primate gestural communication systems, by systematically studying whether non-human primates reliably combine meaningful elements to compositionally create novel combinations with different meanings. To answer this question, we will conduct behavioural observations on four groups of free-ranging and captive chimpanzees (N=98). Chimpanzees are an ideal model to study the evolution of compositionality, as they are our closest living relatives and have very complex communication systems. Our project has four main objectives. First, we will create a new theoretical framework for the study of compositionality in non-human species. To date, there is no consensus on how compositionality should be operationalized in species other than humans, and there are often important methodological differences across research areas. We will therefore conduct a systematic review of literature on compositionality, and critically build on previous work to set the basis for methodologically sounder comparative work on compositionality. Second, we will provide evidence that chimpanzees compositionally recombine gestures with facial expressions and/or vocalizations to create combinations with novel meanings. We will do that across modalities and different contexts, inferring the meaning of signals and combinations by the response they elicit. Third, we will study the specific characteristics of the combinations compositionally produced by chimpanzees, including their intentional use, the temporal distance between elements, and the multimodal aspects of these combinations. Fourth, by observing chimpanzees at different ages and by longitudinally following some individuals, we will understand how compositionality and its different properties emerge through development, and whether they follow the same developmental trajectories as in humans. Therefore, our study will provide the first systematic assessment of compositionality in the gestural communication system of a non-human species, shedding light into the evolutionary origins of one of the most crucial properties of human communication.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2392: Visual communication. Theoretical, empirical, and applied perspectives (ViCom)
• Co-Investigators: Dr. Federica Amici; Dr. Linda Oña