Anger and fearful expressions influence perceptions of physical strength: Testing the signalling functions of emotional facial expressions with a visual aftereffects paradigm

Facial expressions are important social communicators. In addition to communicating social information, the specific muscular movements of expressions may serve additional functional roles. For example, recalibration theory hypothesizes that the anger expression exaggerates facial cues of strength, an indicator of human fighting ability, to increase bargaining power in conflicts. Supporting this theory is evidence that faces displaying one element of an angry expression (e.g. lowered eyebrows) are perceived to be stronger than faces with opposite expression features (e.g. raised eyebrows for fear). The present study sought stronger evidence that more natural manipulations of facial anger also enhance perceived strength. We used expression aftereffects to bias perception of a neutral face towards anger and observed the effects on perceptions of strength. In addition, we tested the specificity of the strength-cue enhancing effect by examining whether two other expressions, fear and happy, also affected perceptions of strength. We found that, as predicted, a face biased to be perceived as angrier was rated as stronger compared to a baseline rating, whereas a face biased to be more fearful was rated as weaker, consistent with the purported function of fear as an act of submission. Interestingly, faces biased towards a happy expression were also perceived as stronger, though the effect was smaller than that for anger. Overall, the results supported the recalibration theory hypothesis that the anger expression enhances cues of strength to increase bargaining power in conflicts, but with some limitations regarding the specificity of the function to anger.