Are memorability judgements suggestible?

How do we determine whether something that we do not remember actually occurred? People rely partially on judging memorability: when non-remembered events seem memorable, we infer that they did not happen, but when those events seem unmemorable, we might infer instead that they were forgotten. In five online experiments (total N = 1544) we examined whether memorability judgements are susceptible to false suggestions. Participants encoded pictures, then completed a test containing old and new pictures. Some test pictures were accompanied by feedback specifying whether they were old or new; however, in a small number of cases, new pictures were falsely identified as "old". For each picture, participants rated familiarity, subjective memorability, and made judgements of learning. A mega-analysis of Experiments 1-4 showed that participants rated new pictures as less memorable after they received false "old" feedback, compared to no feedback. Moreover, this small feedback effect was stronger for those pictures that people on average found more memorable: a finding replicated in Experiment 5. These findings provide initial empirical evidence that false suggestions, in some circumstances, could subtly shift some people from reasoning "I'd remember this, if it had happened" toward reasoning "I don't remember this, so maybe it's forgettable".