Do Tonkean macaques (Macaca tonkeana) tailor their gestural and visual signals to fit the attentional states of a human partner?

We tested here whether Tonkean macaques (Macaca tonkeana), trained to produce a pointing gesture, modify their behaviour in response to different human's attentional states. More specifically, we investigated the macaque's ability to communicate intentionally about the location of an unreachable hidden food reward in several contexts which differ by the human partner's attentional state. The experimenter displayed seven attentional states differing on the basis of body, head and gaze orientation. Our study validates several criteria of an intentional communication. We showed that macaques produce more pointing gestures when an audience, i.e. the human partner, is present than absent. We also revealed an adjustment of gaze alternation between the face of the experimenter and the hidden food reward according to several experimental conditions. However, in our study, macaques did not produce auditory attention-getting behaviours when the human partner was inattentive. Finally, only rough cues, i.e. presence, body and face orientation of the observer, seem to be taken into account by macaques. However, our results also supposed the importance of joint attention for macaques since they display more gaze alternation when the head and/or eyes of the human partner are mobile.