The experiment confirmed that to solve the problem, one must "sleep on it."

Previous studies have shown that the rapid eye movement (REM) phase of sleep enhances the ability to find unconventional solutions by strengthening connections between disparate memories. This stage, characterized by quick eye movements and increased brain activity, may assist in integrating and restructuring existing information.

A group of psychologists from Texas State University (USA) experimentally sought to examine whether participants could tackle tasks that initially stumped them after a brief daytime nap.

The study recruited 58 volunteers aged 18 to 29 from the university's student body. They were incentivized with either monetary compensation or course credits for their participation. The subjects were randomly divided into two groups: one for sleep and one for wakefulness.

Before the experiment, all participants completed a specialized questionnaire to assess the duration and quality of their sleep from the previous night, ensuring uniformity in this factor. Volunteers in the sleep group also filled out the Pittsburgh Sleep Quality Index, which evaluates sleep over the past month.

In the first phase, eight tasks were presented on a computer screen, one at a time. Example: "How can a gardener plant four trees at equal distances from each other?" Participants were given three minutes to think through the solution and write it down on paper. Afterward, the correct answer was displayed on the screen for one minute, which they were asked to memorize. To proceed, they needed to press the "space" key on the keyboard.

After displaying the first eight tasks, there was a five-minute break, followed by the second phase. Participants were presented with eight new questions, structurally similar to the previous ones. Example: "How can six matches be arranged to form four equilateral triangles?" Each task again had a three-minute time limit, but this time, the correct answer was not shown on the screen.

Next, volunteers from the rest group were allowed to leave the laboratory for a two-hour break, during which they were asked not to sleep or consume alcohol or other psychoactive substances. The sleep group, meanwhile, napped in a dark and quiet room within the laboratory. Their brain activity was monitored using electroencephalography.

After the break, participants from both groups returned to the tasks and attempted to solve those they had previously struggled with. They were also asked to take a test to assess their memory of the solutions presented in the first phase. Additionally, participants were requested to evaluate the similarity between the first and second sets of tasks.

Ultimately, researchers found that the sleep group successfully completed a significantly greater number of tasks than the participants who had not slept. The success was not attributed to differing skill levels among individuals, as there were no differences in group performance prior to the two-hour break. Psychologists also found no significant discrepancies between the groups in recalling the displayed solutions.

Notably, the sleeping volunteers rated the similarity between the first and second sets of tasks higher. This suggests that sleep may have helped them recognize hidden connections between the tasks that participants did not notice initially. Finally, researchers identified a positive correlation between the number of tasks solved and the duration of REM sleep among the sleepers.

Thus, the experiment demonstrated that brain processes during sleep can enhance understanding of the problem at hand. As a result, this can aid in resolving it after waking, explained one of the researchers in a comment to Psypost. The article about the research was published in the Journal of Sleep Research.