Interference in simultaneously perceiving and producing facial expressions--evidence from electromyography.

The goal of the current studies was to examine perception-action interactions in a socially relevant domain. Social interactions are based on a mutual understanding of the emotions and actions of others. We assume that the perception of emotional actions also stimulates a parallel action preparation in the perceiver, underlining the common coding theory. We report two experiments aimed to examine whether the perception of socially relevant facial actions (e.g., happy vs. angry facial expressions) interact with the execution of such actions. More specifically, we use a stimulus-response compatibility paradigm, in which subjects responded to the gender of a face by either smiling or frowning while ignoring the fact that the presented face is also randomly either smiling or frowning. We measured reaction time (RT) as onset latency on the two large muscle groups used for smiling (zygomaticus major) and frowning (corrugator supercilii) using electromyography. Experiment 1 showed that on compatible trials, in which perceived facial expression and actually produced facial expression matched, RTs were shorter than on incompatible trials. Experiment 2 used pre-instructed (i.e., blocked) responses and replicated the compatibility effect, suggesting that the effect is functionally located not in response selection but in response initiation or execution. We discuss these results in relation to cognitive mechanisms of common coding of perception and action and to the human mirror neuron system.