Macaques can predict social outcomes from facial expressions.

Bridget M. Waller,Jamie Whitehouse,Jérôme Micheletta

doi:10.1007/s10071-016-0992-3

Bridget M. Waller, Jamie Whitehouse + Show 1 more

Open Access

https://doi.org/10.1007/s10071-016-0992-3

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Journal: Animal cognition	Publication Date: May 7, 2016
Citations: 58	License type: CC BY 4.0

Affiliation: University of Portsmouth

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 (Macacanigra) 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.Electronic supplementary materialThe online version of this article (doi:10.1007/s10071-016-0992-3) contains supplementary material, which is available to authorized users.

Highlights

When Darwin first described the expressions of emotion of humans and other animals, he proposed that facial expressions may not always be functional communicative signals (Darwin 1872) and set the scene for approaching facial expressions more as by-products of feeling states
In order to understand why facial expressions abound in the animal world, it is vital to establish what advantage is gained from using facial expressions within social interactions
The findings show that macaques can use the information provided by conspecifics’ facial expressions to predict how social interactions might progress

Summary

Introduction

When Darwin first described the expressions of emotion of humans and other animals, he proposed that facial expressions may not always be functional communicative signals (Darwin 1872) and set the scene for approaching facial expressions more as by-products of feeling states. Using a novel experimental design, we tested whether the type of facial expression observed in others causes subjects to predict whether a neutral approach will end in one of two categories of behaviour: a peaceful outcome (grooming) or a conflict outcome (injury). We chose these two outcomes as they are mutually exclusive and represent plausible (and very different) outcomes from an approach. We predicted that subjects would choose the two outcomes when the approach ended with a neutral face (control condition)

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Compliance with ethical standards