Automatic facial responses to near-threshold presented facial displays of emotion: imitation or evaluation?

Automatic facial reactions to near-threshold presented facial displays of emotion can be due to motor-mimicry or evaluation. To examine the mechanisms underlying such automatic facial responses we presented facial displays of joy, anger, and disgust for 16.67ms with a backwards masking technique and assessed electromyographic activity over the zygomaticus major, the levator labii, and the corrugator supercilii. As expected, we found that participants responded to displays of joy with contractions of the zygomaticus major and to expressions of anger with contractions of the corrugator supercilii. Critically, facial displays of disgust automatically activated the corrugator supercilii rather than the levator labii. This supports the notion that evaluative processes mediate facial responses to near-threshold presented facial displays of emotion rather than direct mimicry of emotional facial features.