This has real implications for when and how we ought to intervene to maximise best performance in educational settings as well as any place where complex decisions have to be made, and have to be made optimally.
Professor Padraic Monaghan
According to researchers at Lancaster University
, there may be substance to the old adage claiming that to sleep on a problem is to find the solution. The benefits of sleeping, the team concluded, are greatest when the problem being considered is difficult rather than relatively easy.
Research from Lancaster’s Department of Psychology compared the effects of sleeping with the effects of staying awake on people’s ability to problem solve. The study, which appeared today in the journal Memory & Cognition
, tested the response of the participants with verbal insight problems ranging from the easy to the downright difficult.
I asked Professor Padraic Monaghan, who carried out the work alongside colleagues Dr Ut Na Sio and Professor Tom Ormerod, also from the Centre for Research in Human Development and Learning, some questions about the paper. One previous study (Cai et al, 2009) has also tested the truth of the saying, but participants had a nap between their first and second attempt to solve a problem rather than a full night’s sleep. They were also given the answer to the problem in another, unrelated test before being exposed to it a second time.
"Our study is the first to show that you don't need that clue; you don't need the answer presented as you can discover it yourself with overnight sleep," Professor Monaghan explained. "Our study is also the first to probe the question of what type of problem is most affected by sleep. For easy problems, it might be best to just continue trying to find the answer without a break, and certainly without a sleep."
In the experiment, the researchers randomly assigned the 27 male and 34 female participants to a control group, a sleep group, or a wake group.
"For the control group, we presented them with the problems, then asked them immediately to try to resolve those problems," said Professor Monaghan of the methodology. "The sleep and wake groups were given the problems, then asked to return 12 hours later, after either sleeping overnight or staying awake through the day. Problems that the group as a whole found difficult were more easily solved after sleep, but 12 hours of waking time did not help any more than simply continuing with the problem."
I asked Professor Monaghan if he and his colleagues expected to find that overnight sleep – in contrast to napping – was sufficient to assist in solving problems, which is what the study was originally designed to find out.
"It was rather a lovely surprise to find that was the case but only for the more difficult problems," he replied. "This has real implications for when and how we ought to intervene to maximise best performance in educational settings as well as any place where complex decisions have to be made, and have to be made optimally."
For years it has been acknowledged that sleep can have a profound impact on memory, learning and creative thinking. Professor Monaghan supplied various examples.
"You’ll be better at tennis the day after having a tennis lesson (interestingly this is a stronger effect for learning more difficult physical routines), you'll remember more information if you study in the evening and then test yourself the next day rather than study and test the same day, and you'll be better at solving all sorts of problems if you leave them overnight. We've tested word finding problems, Rebus visual problems, and even sudokus."
The team have also been working on a computational cognitive model of problem solving processes to provide an explanation as to why the beneficial effects of sleep are more pronounced for harder problems.
"Harder problems require information to be activated in the mind that is rather distant from the information that is originally provided for in the problem, and sleep assists in this spreading of activation to more distantly connected information. For easier problems, the answer is more or less staring you in the face – the information occupies a close region to the answer in the mind – and sleep is not required to spread activation to that easier answer."