The spacing effect in list learning: effects of intertrial processing demands

Journal article

Why does spacing of repeated trials improve learning and memory performance? The present work examined whether the benefits of spacing depend not only on the temporal separation between repetitions but also on the processing demands imposed during the intertrial interval (ITI). Across four free-recall experiments, participants studied lists in which each word was presented three times under different repetition schedules and ITI conditions. Experiment 1 showed superior recall in interleaved relative to massed word presentation, providing a benchmark against which subsequent ITI manipulations could be evaluated. In Experiments 2 and 3, we varied ITI content, embedding passive visual stimuli or requiring participants to actively solve arithmetic problems. Whereas passive conditions preserved and even strengthened the recall advantage of spacing, high-load active tasks sharply reduced it. As these conclusions depended on between-experiment comparisons, Experiment 4 replicated these effects in a single experiment. These findings indicate that the effects of separating repetitions depend not only on the duration of the interval, but also on the processing demands during the intervening interval. Passive intervals may preserve opportunities for resource recovery, maintenance, consolidation, or improved subsequent encoding, whereas sustained, attention-demanding processing may restrict these opportunities.

Authors: Pogosyan, D; Jiang, D; Arnob, R; Witnauer, JE; Murphy, RA

• Publication status: Accepted
• Peer review status: Peer reviewed
• Publisher: Springer Nature
• Journal: Memory and Cognition More from this journal
• Acceptance date: 2026-10-17
• EISSN: 1532-5946
• ISSN: 0090-502X
• Language: English
• Keywords: list learning; trial spacing; cognitive load; working memory