London: letting your children take a quick nap during study hours could help them recall faster what they studied and make relearning easy, leading them to remember the exercises even six months later, researchers say. They hypothesised that sleeping in between study sessions might make the relearning process more efficient, reducing the effort needed to commit information to memory. "Our results suggest that interleaving sleep between practice sessions leads to a two-fold advantage, reducing the time spent relearning and ensuring a much better long-term retention than practice alone," explained psychological scientist Stephanie Mazza from University of Lyon in France. Previous research suggested that sleeping after learning is definitely a good strategy but "now we show that sleeping between two learning sessions greatly improves such a strategy," Mazza added. To reach this conclusion, 40 French adults were randomly assigned to either a "sleep" group or a "wake" group. At the first session, all participants were presented with 16 French-Swahili word pairs in random order. After studying a pair for seven seconds, the Swahili word appeared and participants were prompted to type the French translation. The correct word pair was then shown for four seconds. Any words that were not correctly translated were presented again, until each word pair had been correctly translated. Twelve hours after the initial session, the participants completed the recall task again, practicing the whole list of words until all 16 words were correctly translated. In the first session, the two groups showed no difference in how many words they could initially recall or in the number of trials they needed to be able to remember all 16 word pairs. But after 12 hours, the data told another story: Participants who had slept between sessions recalled about 10 of the 16 words, on average, while those who hadn't slept recalled only about 7.5 words. And when it came to relearning, those who had slept needed only about 3 trials to be able to recall all 16 words, while those who had stayed awake needed about 6 trials. "Memories that were not explicitly accessible at the beginning of relearning appeared to have been transformed by sleep in some way," Mazza noted. The memory boost that participants got from sleeping between sessions seemed to last over time. Follow-up data showed that participants in the sleep group outperformed their peers on the recall test one week later. This benefit was still noticeable six months later. The results, published in Psychological Science, a journal of the Association for Psychological Science, suggest that alternating study sessions with sleep might be an easy and effective way to remember information over longer periods of time with less study.