Many of our readers will certainly remember the times when they were at university preparing for an important exam. The evening before the exam, they went through the contents again and again, trying to remember as much of it as possible and then went to bed, hoping to be able of recalling it all the next day. Maybe this was not the worst strategy.
How well we retain information is impacted by the timing of our sleep. Jessica D. Payne from Notre Dame University in Indiana and her colleagues asked their study participants to memorise word pairs: related ones like sea and tide and unrelated ones like fire and clown. They had them recall the word pairs after 30 minutes, 12 hours, or 24 hours. After 12 hours, memory for the unrelated words was better when participants had slept between learning and recall than when they had not slept in between. There was no difference for the related words. 24 hours after the learning phase, all study participants had slept. Now it was the timing of the sleep that made the difference: Those who had gone to sleep shortly after learning the words were better at the recall task than those who had gone through a full day of wakefulness after the memorising phase.
The original article appeared in the Journal PLoS one.
There is an article and a podcast on the Scientific American.
The conclusion is that sleep is important for consolidating our memory, but only for unrelated word pair, that is, content that is not associated with each other easily. But the even more interesting finding is that the timing of our sleep matters: sleeping shortly after learning the contents seems to be beneficial for learning. As Christie Nicholson from the Scientific American puts it: if you need to remember something, try reviewing those notes just before bedtime instead of watching that rerun of Seinfeld you already have memorised.