Physiological linkage to an interaction partner is negatively associated with stability in sympathetic nervous system responding.

Recent work has demonstrated that people can be influenced by the physiological states of their interaction partners, showing physiological linkage to them from one moment to the next. In a study of unacquainted dyads who interacted for 30 min (ndyads = 47), we examine the novel question: Are people who show physiological linkage to their partners in sympathetic nervous system responding also less stable in their own responses? Understanding this relationship has important implications for how social relationships impact affective functioning and health. Results using multilevel modeling demonstrated that the within-person correlation between linkage and stability was negative-the more dyad members were physiologically influenced by their interaction partners, the less stable they were in their own physiological responding. This work shows that physiological linkage can come at a cost to people's own stability, meaning our physiological states are more vulnerable to social influence than previously thought.