Evidence for unintentional emotional contagion beyond dyads

Abstract

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.

Figure 1. The experimental apparatus.

Participant B (on the right of the picture) is isolated from participant C (in the middle) by means of a large black folding screen. On the left of the picture is the recording device, concealed to C. Stimuli were presented to B using a screen located in front of her; a webcam was placed on top of the screen so as to display B's face on C's screen.

Figure 2. The experimental protocol timeline for participants B and C.

Specific instructions are inserted between asterisks. The subject of the photograph has given written informed consent, as outlined in the PLOS consent form, to publication of her photograph.

Figure 3. Electromyographic (zygomaticus major [ZM] and corrugator supercilii [CS]) and skin conductance (SCR) responses in participant C relative to the emotional content perceived by participant B.

(A) EMG response of ZM in C relative to the emotional content perceived by B. (B) EMG response of CS in C relative to the emotional content perceived by B. (C) SCR responses in C relative to the emotional content perceived by B. Black lines indicate significant effects at *P<0.05; **P<0.01; ***P<0.001. Error bars indicate SEM.