Sleeping between study sessions improves memory

Better still, it shows that sleeping between revision sessions boosts students' ability to learn from non-written sources and absorb information, which is easier to reproduce up to six months later.

With the new academic year about to begin, 18 to 25-year-olds who tend to stay up late may find that improving their sleeping habits and going to bed between revision sessions increases their chances of succeeding in their studies.

A team of cognitive science researchers from the University of Lyon surveyed the performance of 40 students, randomly divided into two groups. One group was tested in the morning and then 12 hours later the same evening; the second group was tested in the evening and then 12 hours later the following morning.

In the course of the initial test sessions, the participants were told to study 16 bilingual word pairs in French and Swahili. Each word pair was presented for exactly seven seconds. They were then asked to type the French translation of the Swahili words as they appeared. Participants were also given the opportunity to re-examine word pairs that had failed to retain until they fully completed the exercise.

At the second test session, the same procedure was followed until all 16 words had been correctly translated.

Both groups performed identically in the initial test sessions, with no difference in the number of words they were able to retain and the number of tries needed to find all the right answers.

However, in the second test sessions 12 hours later, those who had slept remembered an average of 10 of the 16 word pairs, whereas those who had not slept only remembered 7.5 word pairs.

There was also a difference in the ability to learn rapidly: "the sleepers" were able to validate 16 word pairs in just three tries, while those who had not slept needed twice as many.

In conclusion, both groups were able to learn the 16 word pairs, but "the sleepers" learned faster and with less effort.

"It appears that memories which are not explicitly accessible at the outset of the learning process are to some degree transformed by a period of sleep,” remarked researcher Dr Stéphanie Mazza. "It is this transformation that enabled subjects to re-encode information more rapidly and to gain time in the second test session."

Not only does sleep enable students to learn better, but it also helps with the long-term consolidation of information.

A week later, the group who had slept was much better at remembering the word pairs, with an average score of 15 pairs as opposed to 11 for the non-sleepers. And this advantage was still evident six months later.

To effectively memorise course materials, researchers have five recommendations: first, avoid procrastination and start revising as early as possible.

Secondly, it is important to space out sessions of study on the same subject. Students who study a lesson once a week for four weeks retain more than those who study it four times in the same week.

Thirdly, they should regularly test their knowledge, and fourthly, be sure to study key lessons in the evening.