Joint contributions of collaborative facilitation and social contagion to the development of shared memories in social groups.

Social interactions can shape our memories. Here, we examined two well-established effects of collaborative remembering on individual memory: collaborative facilitation for initially studied and social contagion with initially unstudied information. Participants were tested in groups of three. After an individual study phase, they completed a first interpolated test either alone or collaboratively with the other group members. Our goal was to explore how prior collaboration affected memory performance on a final critical test, which was taken individually by all participants. Experiments 1a and 1b used additive information as study materials, whereas Experiment 2 introduced contradictory information. All experiments provided evidence of collaborative facilitation and social contagion on the final critical test, which affected individual memory simultaneously. In addition, we also examined memory at the group level on this final critical test, by analyzing the overlap in identical remembered contents across group members. Here, the experiments showed that both collaborative facilitation for studied information and social contagion with unstudied information contributed to the development of shared memories across group members. The presence of contradictory information reduced rates of mnemonic overlap, confirming that changes in individual remembering have repercussions for the development of shared memories at the group level. We discuss what cognitive mechanisms may mediate the effects of social interactions on individual remembering and how they may serve social information transmission and the formation of socially shared memories.