A heavily investigated topic in the ostracismliterature is the manner inwhich being ostracized impacts immediate psychophysiological reactivity. Despite the prevalence of this research, it is still unclear which psychological mechanismunderlies the immediate reaction to cues of ostracism. According to the social-physical pain overlap theory, cues to ostracisminduce a social painresponse akintophysical pain due to shared neurological substrates between social and physical pain. Alternatively, it is possible that the immediate reaction to ostracismreflects a conflict detectionmechanismresponding to a violation of the expectation that one should be socially included. In the present studies,we used pupillometry to distinguish the immediate reaction to ostracismin terms of it primarily representing a pain-oriented response or a conflict-detection response. We continuously measured the pupillary reaction during games of Cyberball,which contained social inclusion events (a ball thrown to the participant) and exclusionevents (a ball thrown to another player).Wefindthatparticipants showa diminished pupillary reaction to cues of exclusion but not to cues of inclusion, consistentwith the social-physical pain overlap theory.