An electromyographic investigation of the impact of task relevance on facial mimicry

When viewing a face expressing emotion, the viewer's face mimics the same emotion. It is unknown whether such facial mimicry takes place when the viewed emotion is a task irrelevant property of the face. The present experiment addressed this question by asking participants to judge either the emotional expression or the colour of a series of happy and angry faces that were either blue or yellow. Electromyographical recordings showed that when emotion was ignored, there was a tendency for facial muscle activity to be suppressed. Nonetheless, participants' facial expressions mimicked target expressions, with the zygomaticus cheek muscle being more active when viewing a smiling face and the corrugator brow muscle more active when viewing an angry face. These data support the automatic encoding of irrelevant emotional information, as well as suppression of emotional information by selective attention.