Automatization and familiarity in repeated checking

Repeated checking paradoxically increases memory uncertainty. This study investigated the underlying mechanism of this effect. We hypothesized that as a result of repeated checking, familiarity with stimuli increases, and automatization of the checking procedure occurs, which should result in decreased memory confidence. We also hypothesized that defamiliarization of the stimuli background leads to de-automatization of checking procedures, and thereby attenuates the effects of repeated checking on memory.Eighty-nine healthy participants performed a computerized checking task, in which they had to activate, deactivate, and check threat-irrelevant stimuli. In a pre- and post-test, participants re-checked stimuli, after which they rated confidence in their memory about the last check. They also completed a reaction time task during the pre- and post-test, to assess automatization of the checking task, in which they responded to tones that were randomly presented. To test the effects of defamiliarization, the perceptual characteristics of the stimuli background were modified.Results showed that repeated checking led to reductions in memory confidence. Furthermore, re-checking led to automatization of checking procedures, but automatization did not mediate the relationship between repeated checking and memory confidence. Defamiliarization did not lead to de-automatization, nor did defamiliarization attenuate the detrimental effects of re-checking on memory confidence.