Memory is not precise. We infer our past from stored information plus what we later imagined, expected, saw, and heard. We don't just retrieve memories, we reweave them. Information acquired after an event alters memory of the event. We often construct memories as we encode them, and every time we relay a memory, we replace the original with a slightly modified version. (crash course video= https://www.youtube.com/watch?v=HVWbrNls-Kw)