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Both repeated practice and sleep improve long-term retention of information. The assumed common mechanism underlying these effects is memory reactivation, either on-line and effortful or off-line and effortless. In the study reported here, we investigated whether sleep-dependent memory consolidation could help to save practice time during relearning. During two sessions occurring 12 hr apart, 40 participants practiced foreign vocabulary until they reached a perfect level of performance. Half of them learned in the morning and relearned in the evening of a single day. The other half learned in the evening of one day, slept, and then relearned in the morning of the next day. Their retention was assessed 1 week later and 6 months later. We found that interleaving sleep between learning sessions not only reduced the amount of practice needed by half but also ensured much better long-term retention. Sleeping after learning is definitely a good strategy, but sleeping between two learning sessions is a better strategy.

Few studies have investigated how scheduling repeated studies of the same material over several days influences its subsequent retention. The study-phase retrieval hypothesis predicts that, under these circumstances, expanding intervals between repetitions will promote the greatest likelihood that the participant will be reminded of previous occurrences of the item, thus leading to a benefit for subsequent recall. In the present article, participants studied vocabulary pairs that were repeated according to one of three schedules. In the expanding schedule, pairs were presented on days 1, 2 and 13; in the uniform schedule, on days 1, 7 and 13; and in the contracting schedule, on days 1, 12 and 13. Cued-recall was assessed after a retention interval (RI) of 2, 6 or 13 days. Consistent with predictions, the expanding schedule generally led to better performance than the other schedules. However, further analyses suggested that the benefit of an expanding schedule may be greater when the RI is longer. [ABSTRACT FROM AUTHOR]

Very few studies have examined the influence of schedules of repetitions across multiple days (e.g., Tsai, 1927). Three temporal schedules of four presentations of pseudoword/word pairs over a 7-day learning period were compared: a uniform (presentations on Days 1, 3, 5, and 7), an expanding (1, 2, 3, 7), and a contracting (1, 5, 6, 7) schedule. Schedule was a within-subjects variable. Experiment 1 was performed on the Internet and showed that cued recall on Day 9 led to higher scores for the stimuli of the expanding schedule. Experiment 2 was performed in the laboratory and showed that the expanding and the uniform schedules led to the highest scores on Day 9. A recognition task performed during the learning phase revealed that stimuli recognized at the time of their repetition were more likely to be retrieved later than the others. Our results are discussed within the framework of the study-phase retrieval and encoding variability theories. [ABSTRACT FROM AUTHOR]