Many of us have had the experience of going to bed after struggling with a problem, only to have the answer pop into our minds when we wake up. As author John Steinbeck eloquently explained: “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.”
A paper published by Dr. Stuart Fogel and his team in the August 2021 issue of Cerebral Cortex takes a closer look at the impact of sleep on problem solving.
Fogel is a cognitive neuroscientist and the director of sleep neuroscience at The Royal’s Institute of Mental Health Research affiliated with the University of Ottawa. He is also a professor at the University of Ottawa School of Psychology and a member of the University of Ottawa Brain and Mind Research Institute. His research focuses on the function of sleep for learning, memory, and cognition.
According to Fogel, research suggests that sleep is critical to learning and memory and has a role in the consolidation of memory, an essential part of learning new information. When we learn something new, it is a fresh memory. Fresh memories are fragile and vulnerable to interference, in other words, easy to forget, until they are “strengthened” and integrated into long term memory. It is Fogel’s belief that “sleep may be an opportune time to actively facilitate the transfer of information to other brain areas for more permanent storage.”
Some of history’s biggest and most important ideas are said to have come after a good night’s sleep, including Albert Einstein’s theory of relativity, Dimitry Mendeleev’s inception of the periodic table, the discovery of insulin by Frederick Banting, Niels Bohr’s insight into the structure of the atom, and Larry Page’s inspiration for Google. So, is it true that when we have a problem it can help us to sleep on it?
To help answer this question, Fogel’s team recruited volunteers to solve a computerized version of a puzzle called the Tower of Hanoi (ToH).
This puzzle consists of three rods and five disks of descending size that are stacked on one of the rods, with the smallest disk at the top. The goal is to move the entire stack to the third rod, one disk at a time. Importantly, the constraints of the task require participants, through trial-and-error, to employ complex logic and strategy, which they are not explicitly aware of, to solve the problem (Watch this video to see the solution.)
The study volunteers were divided into three groups: Sleep, Nap, and Wake. Each group participated in a training session in which they had the opportunity to learn the strategy needed to solve the ToH while being scanned in the MRI.
This training session was followed by either a sleep session (eight hours, overnight), a 90-minute daytime nap during the day, or an eight-hour daytime wake period.
Participants’ brainwaves were measured while they slept. “Brainwaves during sleep are very distinct from wakefulness and there are certain events that occur that we can measure in those brainwave traces that we know are important for memory processes and problem solving,” explains Fogel. “So we can look for those, measure them, and identify whether they are key indicators of good memory processes.”
“Sleep is not just helpful, but it seems to be critical in solving problems,” says Dr. Stuart Fogel, a cognitive neuroscientist and the director of sleep neuroscience at The Royal’s Institute of Mental Health Research affiliated with the University of Ottawa.
Study participants in the sleep group were faster and more accurate when they were retested on the ToH puzzle as compared to individuals in the wake group, suggesting that sleep facilitates and enhances the process of memory consolidation. Importantly, brain scans from the MRI showed strengthening of the memory trace that was specific learning the solution to the problem. This strengthening was strongest in those that slept during the retention interval.
“Sleep is not just helpful, but it seems to be critical in solving problems,” says Fogel.
“When you're exposed to this problem through trial and error eventually you get there, but if you have a period of sleep, it'll result in this eureka moment where you're all of a sudden able to solve this problem that you weren't able to do before you slept.”
Napping was also seen to have positive benefits in some participants, but more research is needed.
The study suggests that sleep is an active participant in our formation of memories and supports good mental and cognitive health.
“Sleep represents a novel and quite powerful therapeutic potential target, and perhaps it’s even the fountain of youth,” says Fogel. “I hope that people make sleep a priority in their lives. It’s a really important aspect of a healthy lifestyle.”