Forgetting, understood as a measurable reduction in memory accessibility over time, has been studied extensively in episodic memory for more than 130 years. However, this research has typically focused on voluntary memory—that is, information retrieved intentionally. Few studies have examined forgetting in relation to involuntary memories—that is, memories coming to mind spontaneously with no preceding attempt at retrieval. The purpose of the present studies was to investigate the effects of cue distinctiveness and the passage of time on the accessibility of involuntary and voluntary memories for pictures of scenes. For both types of retrieval, we examined the frequency of correct memories after a few minutes, one day, and seven days; in Study 2, we also examined frequency after three days. Across both studies and both types of retrieval, distinct cues yielded better memory access than nondistinct cues, and memory frequency dropped systematically with increased retention time. At the shortest retention interval, voluntary retrieval led to greater memory access than involuntary retrieval, but after one week, this advantage had disappeared. The findings suggest that memories for events become more cue-dependent over time, which limits the beneficial effects of strategic search associated with voluntary retrieval at longer delays.
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