Effortless facial expression recognition without motor simulation.

Efficient recognition of facial expressions is often assumed to require covert and unconscious imitation of the observed facial movements - a "motor simulation". At odds with this hypothesis, some individuals with congenital facial paralysis can recognize facial expressions with typical speed and accuracy. However, efficiency also implies minimal cognitive effort. Motor simulation may reduce the need for effortful inferential processing. To explore this, we asked 16 individuals born with congenital facial paralysis and typically developed participants to categorize emotional sounds (e.g. anger vs. fear) while viewing congruent or incongruent facial expressions. The facial expressions were irrelevant to the task, but facial identity was important for a subsequent memory test. If motor simulation is necessary for effortless facial expression recognition, individuals born with congenital facial paralysis should not be influenced by the facial expressions. If motor simulation contributes to effortless facial expression recognition without being necessary, they could be less influenced than the typically developed participant. However, the results did not support either of these predictions. Effortless facial expression recognition can be achieved without motor simulation.