Sleep consolidation of social memories and common ground.

Sleep consolidation effects are well established in the cognitive domains of memory and language learning, however very little is known regarding sleep effects in social contexts. Across three experiments, we investigated whether sleep enhances the accuracy of socially formed memories and communicative efficiency, including the use of partner-specific common ground between interlocutors in conversation. Participants completed a computerised (Experiment 1) or face-to-face (Experiment 2) matcher-director task with two other people before and after 12 h of sleep/wake. Both experiments showed more accurate item recognition and source memory after sleep vs. wake. The Sleep group also used fewer words to describe old vs. new items in Experiment 2, suggesting an influence of sleep on communicative behaviour based on prior discourse, but this effect was not partner specific. In Experiment 3, the retention of item/source memory and common ground was measured across a two-hour, polysomnographically recorded nap. Results revealed no significant relationships between consolidation-linked sleep electrophysiology (e.g., slow oscillation-spindle coupling) and memory/common ground retention. Together, these findings indicate that sleep plays a key role in stabilising the social-cognitive foundations of communication but cannot elucidate the mechanism(s) underpinning this support. Regardless, by preserving conversational memories and the efficiency of shared understanding, sleep may help sustain smooth coordination in everyday interaction and social relationships.