This chapter explores how people “think together” in dyads, small groups, and larger collectives via mutual influence that organizes shared attention and intention, collectively constructs and validates meaning, and collaboratively develops and adjusts distributed networks of learning, memory, and forgetting. It weaves together a selective review of psychological literature on socially shared and situated cognition with applications to the shared and unshared memories of survivors and killers in post-genocide Rwanda. The process and content of convergent and divergent memories about a devastating collective experience helps illuminate the practical psychological functions served by socially shared cognition.