Abstract
The aim of this study is to investigate spatial reference in captive chimpanzees (Pan troglodytes). Reference is the ability to communicate with others about events or objects in the environment. It is a fundamental component of human communication, playing a crucial role in social skills and language development. Spatial reference concerns more specifically the spatial location of objects being referred to. Individuals divide the space into different areas (most often, near versus far space), and consequently resort to appropriate linguistic and gestural signals, to efficiently and accurately locate a referent. This distance contrast (near/far), thereafter referred to as distance encoding, appears to be a robust feature of referential communication, present in all aspects of multimodal pointing. The distance of a referent is thus encoded at a lexical, high language processing, level, and at a motor, low language processing, level. In other words, individuals use distance-specific linguistic units (such as “here” versus “there”), but also distance-specific oral and manual gestures, to designate a close versus a distant referent. This suggests a close connection between linguistic structures and communicative gestures. We believe that looking for such distance encoding in our closest living relatives signaling could provide valuable information on the emergence of referential communication. We are thus investigating the ability of eight captive chimpanzees to adjust their communicative signals according to the spatial properties of a referent. For that purpose, we are using a food-requesting paradigm, where a piece of food is located either in the chimpanzees proximal space (‘near’ condition) or in their distal space (‘far’ condition). Besides, chimpanzees are tested for their requesting behavior in two conditions, either with a human interlocutor (‘with human’ condition) or alone (‘without human’ condition). This will allow us to assess the communicative nature of the observed behaviors. Intentional communicative signals, such as pointing gestures, attention-getting gestures, and vocalizations, will be categorized as visual, auditory, or audio-visual signals. The relative proportion of each signal, and some qualitative features of manual gestures (e.g. shape, orientation and position of the hand), as well as those of each signals combination, will be compared between the ‘near’ and the ‘far’ conditions. Distance encoding, that would be here a systematic variation of the signals depending on the distance of the food, could manifest itself in many ways, including for instance a multimodal strategy (i.e. combinations of unimodal signals and/or use of multimodal signals per se)to designate a distant referent.
