A patient's account of a past event turns out to be inaccurate. Before revealing the answer, decide what distinguishes a false memory from retrospective falsification.

Ask whether a real event underlies the account at all, and if so, whether the distortion is a general mood-driven colouring of it. A false memory may have no real underlying event whatsoever — the whole thing can be fabricated, held with full conviction despite having no basis in fact. Retrospective falsification, by contrast, involves a real event that is genuinely recalled but coloured by mood as it is retrieved, a general distortion of an event that did happen rather than a wholesale invention. Establishing whether any of the underlying event actually occurred is the key discriminating question, not how confidently the account is held, since both can be held with real conviction.