Communicative intentions are transmitted by many perceptual cues, including gaze direction, body gesture, and facial expressions. However, little is known about how these visual social cues are integrated over time in the brain and, notably, whether this binding occurs in the emotional or the motor system. By coupling magnetic resonance and electroencephalography imaging in humans, we were able to show that, 200 ms after stimulus onset, the premotor cortex integrated gaze, gesture, and emotion displayed by a congener. At earlier stages, emotional content was processed independently in the amygdala (170 ms), whereas directional cues (gaze direction with pointing gesture) were combined at ∼190 ms in the parietal and supplementary motor cortices. These results demonstrate that the early binding of visual social signals displayed by an agent engaged the dorsal pathway and the premotor cortex, possibly to facilitate the preparation of an adaptive response to another person's immediate intention.

Little is known about the spread of emotions beyond dyads. Yet, it is of importance for explaining the emergence of crowd behaviors. Here, we experimentally addressed whether emotional homogeneity within a crowd might result from a cascade of local emotional transmissions where the perception of another’s emotional expression produces, in the observer's face and body, sufficient information to allow for the transmission of the emotion to a third party. We reproduced a minimal element of a crowd situation and recorded the facial electromyographic activity and the skin conductance response of an individual C observing the face of an individual B watching an individual A displaying either joy or fear full body expressions. Critically, individual B did not know that she was being watched. We show that emotions of joy and fear displayed by A were spontaneously transmitted to C through B, even when the emotional information available in B’s faces could not be explicitly recognized. These findings demonstrate that one is tuned to react to others’ emotional signals and to unintentionally produce subtle but sufficient emotional cues to induce emotional states in others. This phenomenon could be the mark of a spontaneous cooperative behavior whose function is to communicate survival-value information to conspecifics.

People display facial reactions when exposed to others' emotional expressions, but exactly what mechanism mediates these facial reactions remains a debated issue. In this study, we manipulated two critical perceptual features that contribute to determining the significance of others' emotional expressions: the direction of attention (toward or away from the observer) and the intensity of the emotional display. Electromyographic activity over the corrugator muscle was recorded while participants observed videos of neutral to angry body expressions. Self-directed bodies induced greater corrugator activity than other-directed bodies; additionally corrugator activity was only influenced by the intensity of anger expresssed by self-directed bodies. These data support the hypothesis that rapid facial reactions are the outcome of self-relevant emotional processing.