‘My face is listening to your smile’: Emotional contagion to vocal smile revealed by combined pupil reactivity and motor resonance

Interaction between the different components of emotional contagion (i.e. emotional state and facial motor resonance), whether during implicit or explicit appraisal of emotion remains controversial. The aim of this study was i) to separate between these components thanks to vocal smile processing and ii) to estimate how they reflect implicit processes and/or an explicit appraisal loop. Emotional contagion to discrete vocal emotions was studied in 25 adults, through motor resonance and Autonomic Nervous System (ANS) reactivity. Facial expressions (fEMG: facial electromyography) and pupil dilation were assessed during processing and judgement of artificially emotionally modified sentences. fEMG revealed that Zygomaticus major was reactive to perceived sounds valence while Corrugator supercilii activity rather reflected explicit judgement. Timing analysis of pupil dilation provided further insight into both the emotional state and the implicit and explicit processing of vocal emotion, showing an early activity for emotional stimuli compared to neutral ones, followed by variations based on sounds valence, and by a late additional increase of pupil diameter depending on judgement. This innovative combination of these electrophysiological measures shed new light on the debated central and peripherical views within the framework of emotional contagion.