cardiac synchrony is a crucial component of shared experiences, considered as an objective measure of emotional processes accompanying empathic interactions. no study has investigated whether cardiac synchrony among people engaged in collective situations links to the individual emotional evaluation of the shared experience. We investigated theatrical live performances as collective experiences evoking strong emotional engagement in the audience. Cross Recurrence Quantification Analysis was applied to obtain the cardiac synchrony of twelve spectators' quartets attending to two live acting performances. this physiological measure was then correlated with spectators' emotional intensity ratings. Results showed an expected increment in synchrony among people belonging to the same quartet during both performances attendance and rest periods. furthermore, participants' cardiac synchrony was found to be correlated with audience's convergence in the explicit emotional evaluation of the performances they attended to. These findings demonstrate that the mere co-presence of other people sharing a common experience is enough for cardiac synchrony to occur spontaneously and that it increases in function of a shared and coherent explicit emotional experience. Collective experiences are ubiquitous aspects of human culture where emotional activity finds its breeding epicenter. Being involved in collective events, like religious rituals, parades or team sports, fosters prosociality 1 and contributes to the creation of emotional bonds among group members 2. Coherently, it has been shown that the presence of others modulates how individuals feel, express and perceive emotions 3. Amongst the various group experiences populating our social life, specific forms of "collective art" can be included. Indeed, even if some forms of art can be described as "individual", in the sense that usually people enjoy them alone, others are commonly appreciated together with other people. This is the case of several performative arts (e.g., theatre, dance, music) in which people share the artistic experience as part of a group. Studies show that people react differently to these forms of art if they enjoy them alone or with others, suggesting that the presence of others plays a role. For example, at the autonomic level, people react more to music when they are alone than when are in a group 4,5. Differently, watching an aggressive movie clip modulates spectator's subsequent behaviors, on the basis of the attitude of the co-spectators 6. Furthermore, how people react to the mere presence of others influences their parasympathetic response to shared filmic experience 7. One interesting component of collective experiences, that recently drew increasing attention, is the spontaneous synchronization among group members. Synchrony is a well-known phenomenon occurring at different levels (e.g., behavioral, physiological and neural), and it is related to the presence of similar reactions among group members within a short period of time. For example, people...