While studies have shown that both repeated practice and sleep can help improve memory, there is little research investigating how repetition and sleep influence memory when they are combined. Mazza and colleagues hypothesized that sleeping in between study sessions might make the relearning process more efficient, reducing the effort needed to commit information to memory.
Researchers found that undertaking periods of sleep between periods of learning gives you two benefits. It reduces the time spent relearning and ensures better long-term retention than practice alone. The research was carried out by, Stephanie Mazza a psychological scientist at the University of Lyon.
The researchers studied 40 French adults who were randomly assigned to either a “sleep” group or a “wake” group. At the first session, all participants were presented with word in French and Swahili in random order. After studying a pair for 7 seconds, the Swahili word appeared and participants were prompted to type the French translation. Any words that were not correctly translated were presented again, until each word pair had been correctly translated.
Twelve hours after the first session, the participants completed the task again until all 16 words were correctly translated.
To test the impact of sleep on remembering some participants completed the first session in the morning and the second session in the evening of the same day (“wake” group); others completed the first session in the evening, slept, and completed the second session the following morning (“sleep” group).
In the first session, the two groups showed no difference in how many words they could recall or in the number of trials they needed to be able to remember all 16 word pairs.
But after sleep: Participants 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 3 trials to be able to recall all 16 words, while those who had stayed awake needed 6 trials.
Both groups were able to learn all 16 word pairs, but sleeping in between sessions seemed to allow participants to do so in less time and with less effort.
Mazza says that memories seem to have been transformed by sleep allowing participants to re-encode information faster and to save time during the relearning session.
And there is evidence that this benefit lasts. Follow-up data showed that participants in the sleep group outperformed their peers on the recall test one week later. The sleep group showed very little forgetting, recalling 15 word pairs, compared to the wake group, who were able to recall 11 word pairs. This benefit was still noticeable 6 months later.
The benefits of sleep could not be ascribed to participants’ sleep quality or their levels of tiredness or to their short-term or long-term memory capacity, as the two groups showed no differences on these measures.
The results 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.
In a work context this suggests that if you need to remember new information such as in a training course encouraging people to learn the information prior to going home to sleep is a good strategy. For example, we encourage clients on our leadership programmes to run the event form lunch time to lunchtime. We find people not only remember what they learnt the day before they tend to have more insights about the application of the new information to their role.
Original Research: Abstract for “Relearn Faster and Retain Longer: Along With Practice, Sleep Makes Perfect” by Stéphanie Mazza, Emilie Gerbier, Marie-Paule Gustin, Zumrut Kasikci, Olivier Koenig, Thomas C. Toppino, and Michel Magnin in Psychological Science. Published online August 16 2016 doi:10.1177/0956797616659930