“This study provides yet more evidence that brain processing during sleep is helpful to daytime cognition,” said senior author Mark Beeman of Northwestern's Department of Psychology.
Stimulating problem solving with sound cues
Beeman and his colleagues said that solving a difficult problem can be a matter of building new combinations of known elements to reveal a solution. Based on this premise, the researchers hypothesized that there could be a problem-solving strategy similar to the reorganization of memory during sleep.
“We know that people rehearse or ‘consolidate’ memories during sleep, strengthening and reorganizing them,” said corresponding author Kristin Sanders, a research associate at ?Northwestern.
To test their hypothesis, the researchers needed to direct the brains of sleeping participants toward specific problems without waking them. Based on previous studies, this could be achieved by playing sounds associated with the information being rehearsed in the brain.
With that in mind, the researchers enlisted 57 participants and presented them with various spatial and verbal brainteasers before bed. Each brainteaser was paired with a unique sound, and some of the puzzles remained unsolved. During the volunteers' slow-wave sleep – the period where dreaming and memory re-organization are thought to occur – the researchers replayed the sounds for half of each participant’s unsolved puzzles without waking them up. In the morning, the volunteers were asked to work out the remaining puzzles.
Over the course of two experimental sessions, the researchers found that the participants were 55 percent more likely to solve the remaining puzzles when the corresponding sound clips were secretly played while they slept. The team added that the effect was not dependent on the type of puzzle; solve rates for both verbal and spatial puzzles increased when cued during sleep. (Related: Sleep it off: Research explains why sleep is so important for your immune system.)
The study demonstrates that the mind can be manipulated during sleep to search of solutions that prove elusive while awake. However, the researchers noted that the technique will only work if one has the necessary information to solve the puzzle.
“For example, no matter how much sleep I get, I’m not going to suddenly figure out black holes or find a cure for a rare disease because I don’t have the necessary background knowledge,” explained Beeman.
Improving cognition through sleep
In another study, researchers from Lancaster University in the U.K. found that "sleeping on" a problem overnight can boost your problem-solving abilities. The researchers showed one group of volunteers a set of problems in the evening and asked them to solve them again the next morning. Meanwhile, another group saw the problems in the morning then reattempted them in the evening. While the latter solved the easy problems slightly more effectively, those who slept first did much better at solving the difficult problems.
Cognitive scientist Carolina Kuepper-Tetzel of the University of Glasgow, who was not part of the study, said that sleep improves problem-solving because it is one form of "incubation" – a stage in the creative thinking process where you spend time away from a puzzle. Incubation, according to Kuepper-Tetzel, is one way to facilitate insight and get you closer to finding a solution.
Read more fascinating studies about the science of sleep at Brain.news.
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