Free time benefits working memory and long-term memory differently

Giving people more time between encoding information elements into working memory improves immediate (i.e., working memory) and delayed (i.e., long-term memory) retrieval. This free-time benefit is often assumed to arise from processes that counteract forgetting of the just encoded item in working memory, suggesting that time has a retroactive effect. Contrary to these predictions, a few studies showed that free time between two items in a serial recall task benefits only the subsequent (to-be-encoded) items, yielding a proactive benefit in working memory. Here, we investigate whether working memory and long-term memory benefit from free time in the same way. In three experiments, we show that free time benefits the to-be-encoded items in working memory (proactive effect) with only a local retroactive effect for recently encoded items, whereas it mainly benefits already encoded items in long-term memory (retroactive benefit). These results challenge a single explanation of the free-time benefit for memory retention across short and long intervals.