Visible skin disease symptoms of another person reduce automatic imitation of their hand movements.

Imitation is an important mechanism for social interaction and learning, and humans tend to imitate others automatically. While imitating others is often useful, it can backfire when imitation is incongruent with one's goals. For example, in forced-choice reaction time tasks, this tendency results in a reliable slowing of reactions if the observed and self-initiated actions are incompatible (compatibility effect). While imitation is commonly explained as a social phenomenon, previous results on the compatibility effect's dependence on social cues are inconsistent. However, in many previous studies, the associated social cues were easy to ignore by the participants. To make the social modifier more salient, the current study manipulated emotionally relevant aspects of the model hand itself in an imitation inhibition task by using models displaying skin disease symptoms which we expected to elicit (1) perceptions of dissimilarity and (2) disgust in participants. As predicted, participants' (n = 63) reaction times were influenced more by the incompatible actions of the symptom-free than the symptomatic model hand. However, both levels of self-reported disgust toward and self-other overlap with symptomatic hands were low and did not account for the observed effect on automatic imitation. Our findings show that automatic imitation depends on social factors if these are an integral part of the model and processed quickly, presumably due to their affective salience or the salience of the self-other distinction. Whether this effect is driven by emotional reactions to the model remains an open question.