Intergroup dissimilarity predicts physiological synchrony and affiliation in intergroup interaction

Interpersonal similarity attracts. In intergroup contexts, however, similarity between groups potentiates bias. The current study examined whether intergroup similarity versus dissimilarity engenders cross-group friendship formation. We used an essay-writing paradigm to manipulate perceived intergroup similarity or dissimilarity between the ethnic groups of participants prior to a dyadic interaction that involved a competitive party game. During the interaction, we continuously recorded physiological and behavioral responses from both participants. We used the physiological responses to derive a measure of physiological synchrony: the mutual activation of partners' sympathetic nervous systems. People primed with dissimilarity, not similarity, experienced physiological synchrony with their partner. Moreover, the partners of people primed with dissimilarity acted more affiliative than the partners of people primed with similarity, which in turn predicted friendship initiation by participants. We discuss the seemingly counter-intuitive value of emphasizing differences between groups to foster positive intergroup relations.