Forgetting the unforgettable through conversation: socially shared retrieval-induced forgetting of September 11 memories.

A speaker's selective recounting of memories shared with a listener will induce both the speaker and the listener to forget unmentioned, related material more than unmentioned, unrelated material. We extended this finding of within-individual and socially shared retrieval-induced forgetting to well-rehearsed, emotionally intense memories that are similar for the speaker and listener, but differ in specifics. A questionnaire probed participants' memory of the September 11 terrorist attacks. Questions and responses were grouped into category-exemplar structures. Then, participants selectively rehearsed their answers (using a structured interview in Experiment 1 and a joint recounting between pairs in Experiment 2). In subsequent recognition tests, response times yielded evidence of within-individual retrieval-induced forgetting and socially shared retrieval-induced forgetting. This result indicates that conversations can alter memories of speakers and listeners in similar ways, even when the memories differ. We discuss socially shared retrieval-induced forgetting as a mechanism for the formation of collective memories.