Macaques can predict social outcomes from facial expressions - PubMed (original) (raw)

Macaques can predict social outcomes from facial expressions

Bridget M Waller et al. Anim Cogn. 2016 Sep.

Abstract

There is widespread acceptance that facial expressions are useful in social interactions, but empirical demonstration of their adaptive function has remained elusive. Here, we investigated whether macaques can use the facial expressions of others to predict the future outcomes of social interaction. Crested macaques (Macaca nigra) were shown an approach between two unknown individuals on a touchscreen and were required to choose between one of two potential social outcomes. The facial expressions of the actors were manipulated in the last frame of the video. One subject reached the experimental stage and accurately predicted different social outcomes depending on which facial expressions the actors displayed. The bared-teeth display (homologue of the human smile) was most strongly associated with predicted friendly outcomes. Contrary to our predictions, screams and threat faces were not associated more with conflict outcomes. Overall, therefore, the presence of any facial expression (compared to neutral) caused the subject to choose friendly outcomes more than negative outcomes. Facial expression in general, therefore, indicated a reduced likelihood of social conflict. The findings dispute traditional theories that view expressions only as indicators of present emotion and instead suggest that expressions form part of complex social interactions where individuals think beyond the present.

Keywords: Communication; Emotion; Facial expression; Facial signals; Primates.

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Figures

Fig. 1

Fig. 1

Graphical representation of the experimental procedure. Subject was presented with a video sequence of one unknown individual approaching another (1). The final frame of the video remained on the touchscreen, and the image was manipulated to either display: (2a) a neutral face (N), (2b) an open-mouth threat (OM), (2c) a scream face (SC), or (2d) a bared-teeth face (BT). Once the subject touched this image, the individual was then presented with a choice of social outcomes, (3a) grooming, or (3b) injury. The percentage of choice for each facial expression is given on the right panel. The dotted line represents the expected values derived from the Chi-squared analysis. Photographs taken by Jérôme Micheletta

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