Intentional gestural communication and discrimination of human attentional states in rhesus macaques (Macaca mulatta)
The present study tested intentionality of a learned begging gesture and attention-reading abilities in rhesus macaques (Macaca mulatta). Subjects were trained to produce a begging gesture towards a hidden food reward that could be delivered by a human experimenter. More specifically, we investigated which attentional cues—body, face and/or eyes orientation of a human partner—were taken into account by the macaques in order to communicate with her. Our results provide strong evidence of intentional communication: the monkeys adjusted their behaviour to that of the partner. The latter’s attentional state influenced the monkeys’ likelihood of performing begging gestures and showing gaze alternation between the partner and the hidden food. By contrast, we found no evidence of attention-getting behaviours, persistence or elaboration of new communicative behaviours. Our results also showed that rhesus macaques discriminated gross cues including the presence, body and face orientation of the human experimenter but not her eyes. However, the monkeys emitted more gaze alternation and monitored the human’s attentional state more closely when she also displayed gaze alternation, suggesting an important role of joint attention in gestural communication.
KeywordsSocial cognition Attention-reading abilities Non-human primates Intentionality Macaca mulatta
This study was funded mainly by the Primatology Centre of Strasbourg University. CC also received the “Tremplin” grant of the Francophone Society of Primatology (SFDP) for this work. The authors are sincerely grateful to Nicolas Herrenschmidt and his whole team for allowing them to conduct this study at the Primatology Centre of Strasbourg University in France. The authors are particularly thankful to the assistants Lucie Ligault, Sophie Le Ray, Ondine Walter and Clémence Simart for helping in training the subjects to point and in data collection during the experiments. Nicolas Poulin from CeStatS of Strasbourg University, Marie Bourjade from the Aix-Marseille University and Jonas Fizet from the Primatology Centre of Strasbourg University are greatly thanked for statistical assistance. Jim Anderson and Sarah Lux are warmly thanked for their proofreading and correction of the English manuscript. Authors also thank Nadège Krebs from Noldus for her valuable advice concerning the use of The Observer software and the Conservation Sauvage Internationale association for providing internship agreement to CC. The authors declare that they have no conflict of interest. All the experiments adhered to the current French laws concerning laboratory animal care and were approved by the French ethical committee CREMEAS (Number of agreement for conducting experiments on primates: AL/46/53/02/13).
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