EXPRESS: Spontaneous mnemonic strategy use under proactive interference is related to better recall but does not protect from accumulating interference.

Proactive interference (PI) is a key mechanism in forgetting, making it important to examine factors that may alleviate its detrimental effects. In a preregistered online study with 207 English-speaking 18-60-year-old adults, we probed block-by-block spontaneous mnemonic strategy use in a categorized word list recall task with increasing PI, followed by release from PI. Based on the block-wise self-reports, participants were classified as no strategy users, maintenance strategy users (e.g., repetition), or manipulation strategy users (e.g., grouping, creating a story). Strategy users formed a majority and showed better recall than no strategy users, with highest recall rates in manipulation strategy users. The detrimental effects of PI on word recall were similar in the three subgroups. Self-reports suggested increased shifts of selected strategy when moving from the last PI block to release from PI. Altogether, the present results indicate that self-generated memory strategies are (1) common in adults, (2) flexibly used when faced with a qualitative change in task demands, (3) associated with better memory performance especially concerning more sophisticated strategies involving mental manipulation of the memoranda, but (4) do not prevent the buildup of PI as they may not provide enough differentiation between current and previous category members.