Blurred Lines or Clear Boundaries? Synchrony and Social Dominance Shape Domain-Specific Self–Other Processing

Synchronous behaviour is widespread across social species and is a common feature of human social interaction. Prior research shows that synchrony can alter self–other processing, yet findings are inconsistent, potentially due to task differences and individual variability. In this preregistered study (54 dyads), we examined whether synchronous finger tapping influences self–other cognition across three domains: episodic memory, source memory, and emotion. Synchrony increased source memory performance but did not affect item memory. In contrast, synchrony heightened emotional egocentric bias, suggesting that synchrony can sharpen self–other differentiation in memory while increasing reliance on one’s own affective state when inferring others’ emotions. Social dominance moderated these effects. Dyads with higher combined dominance synchronized more strongly, and dominant individuals showed greater egocentric responding in memory tasks and retained egocentric bias in source memory even after synchrony. These findings highlight domain-specific consequences of synchrony and the importance of interpersonal traits in shaping synchrony outcomes.