How sounds can help you solve problems in your sleep

For centuries an old adage has suggested sleeping on a particularly confounding problem can miraculously result in a solution appearing in the morning. Albert Einstein was allegedly a huge advocate of sleep solutions, not only getting a big ten-hour stretch every night but also promoting the idea of short naps scattered throughout the day.

“It is a common experience that a problem difficult at night is resolved in the morning after the committee of sleep has worked on it,” the author John Steinbeck was famously quoted as saying.

Scientists know that sleep is important for maintaining optimum cognitive functioning. Alongside benefiting physical and brain health, sleep is thought to play an fundamental role in how we retain new information. This process is generally referred to as memory consolidation, where we essentially sort all the information gathered during our waking day and file it into higher cortical centers.

More specific research has tried to ascertain whether sleep does empirically improve problem solving performance, and the results have mostly confirmed the old adage. Incubating a problem during sleep can increase the chances of finding a solution, especially in the face of difficult problems.

“We know that people rehearse or ‘consolidate’ memories during sleep, strengthening and reorganizing them,” says Kristin Sanders, first author on the new research from Northwestern University. “It’s also known that this natural process can be boosted by playing sounds associated with the information being rehearsed.”

The researchers on the new study wondered whether certain sound cues could be used to improve our ability to solve problems while we sleep. To test the hypothesis a number of subjects were tasked with solving puzzles associated with individual sound cues. Once each subject failed to solve six puzzles they were sent home with a portable electroencephalogram sleep monitoring and cuing system.

The device was set to detect when the subject enters slow-wave sleep, and once in the desired sleep phase, three of the six unique cue sounds were played, corresponding with the puzzles the subject had failed to solve. The next day each participant returned to the lab to try and solve the six puzzles they failed to solve the prior evening.

The remarkable results revealed the subjects solving significantly more of the puzzles that had been sound cued overnight, compared to the puzzles without overnight cues. In fact, 55 percent more puzzles were solved if the subject had its corresponding sound played overnight while they slept.

“This study provides yet more evidence that brain processing during sleep is helpful to daytime cognition,” says Mark Beeman, senior author on the study. “In this case, if you want to solve problems or make the best decisions, better to sleep on it than to be on Twitter at 3 a.m.”

The study raises plenty of novel questions that will hopefully be resolved by future research. It is unclear, for example, whether slow wave sleep is the most effective sleep phase to administer these kinds of sound cues. It is hypothesized that spreading the timing of sound cues between slow wave and REM sleep phases may enhance creative problem solving results.

It is also unclear exactly what is occurring in the brain that leads to sleep delivering these kinds of problem solving results. Interestingly, the study found that the overnight sound cues did not specifically improve the subjects’ ability to recall puzzle details. So, while the overnight cues amplified some problem solving abilities, they didn’t directly enhance a memory imprint of certain puzzle details. Beeman suggests this means sleep is more about reorganizing knowledge than coming up with new or novel information.

“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,” says Beeman. “However, if you’ve studied a problem thoroughly and are still stuck, thinking about it during a good night’s sleep may be just the trick.”