Facing social and non-social sounds: Sighted and blind individuals spontaneously and selectively activate facial muscles in response to emotional vocalizations

The present study investigated facial responses to emotional sounds that represent social (e.g., laughter, screams) and non-social domains (e.g., instrumental music). Such cross-channel responses allow for examination of mechanisms involved in spontaneous mimicry. In order to address the role of visual experience in facial response to sounds, we compared sighted and blind individuals. To measure spontaneous responding, participants freely listened to the sounds. We used facial electromyography to record the activity of the corrugator supercilii (frowning) and the zygomaticus major (smiling) muscles. Results showed that social, but not equally rated, non-social sounds selectively elicited congruent facial responses. This occurred in both sighted and blind individuals, suggesting that facial response to social emotional sounds might not depend on a previous association with visual input (connecting a happy sound with seeing a happy face). Finally, facial responses to happy vocalizations were especially pronounced. This suggests that spontaneous facial responses to emotional sounds also reflect affiliative social goals. Overall, the pattern of results is consistent with simulationist approaches to emotional mimicry. Additionally, despite no differences between the groups in average facial responses, we observed the difference in the dynamics of the zygomatic response to human affect vocalizations. The altered pattern of facial responses to affect vocalizations may influence social interactions of blind and sighted persons.