There is a science to consulting your pillow: sleep is a source of inspiration.

Leonardo da Vinci had a rather unusual sleep routine. It's speculated that the famous artist of the Mona Lisa used to sleep 20 minutes every four hours throughout the day, a habit as eccentric as his genius. The Catalan artist Salvador Dalí did something similar, resting through micro-naps during his day with a handful of pencils in his hands. Despite being separated by centuries, both seemed to sense something true: daytime naps represented one of their main sources of inspiration.

And they're not alone. You don't have to be a genius to experience a eureka moment —that sudden spark that solves a problem or uncovers an idea. A new study in the journal PLOS Biology suggests that reaching the first stage of deep sleep (or N2) during a nap could help someone who needs that epiphany or a moment of lucidity. To achieve a true aha! moment, sometimes the most effective thing is to close your eyes and disconnect for a moment. Neuroscience is beginning to confirm what some artists practiced almost ritually.

Anika Löwe and Maria Tzegka, researchers at the University of Hamburg (Germany), designed an experiment involving a group of 90 volunteers between the ages of 18 and 35. The seemingly simple task consisted of following a series of dots on a screen and responding by pressing a keyboard. What the participants didn't know was that, after completing 40% of the exercise, the scientists would introduce a trick that made the task easier. After four rounds of trials, some of the subjects were put to take a 20-minute nap, while their brains were monitored using an electroencephalogram (EEG) .

Upon awakening, all groups showed some improvement in their performance, but 70.6% of those who reached the N2 phase while asleep detected the hidden strategy. And only 55% of those who remained awake were able to uncover the trick. "The result is a brain that is more flexible and receptive to new ideas, which could explain why so many people discover the hidden trick behind the nap," Anika Löwe, lead author of the research published this Thursday, told EL PAÍS. In other words, a more attentive mind that can see what previously went unnoticed.

Most existing sleep studies focus on oscillatory activity—namely, sleep spindles and slow waves—which are rhythmic and show clear spikes on the EEG. In this case, however, scientists focused on aperiodic activity, which consists of electrical patterns in the brain that don't repeat regularly. This kind of neuronal "background noise" appears to play a key role in how our neurons fire, fire, and make new connections.

"We found that it provided additional predictive power, possibly because it reflects a more continuous dimension of sleep depth and brain flexibility, beyond traditional sleep phases," the scientist says.

Delphine Oudiette, a neuroscientist at the Paris Brain Institute (France) , believes that more studies are still needed to understand how these mechanisms work. “It’s a challenge for specialists to uncover the neural processes involved,” notes this expert, who was not involved in the analysis. The lack of clarity about cognitive processes, according to Oudiette, makes it difficult to know exactly “what part of the task or stage of sleep produces the effect.”

One of the major limitations of the new analysis is that the scientists did not monitor brain activity during the task, although they did monitor brain activity during the nap. “An interesting next step would be to examine whether some of the learned content is reactivated during sleep and how this relates to a moment of revelation,” the author says. The authors of the study hope that this discovery, which could be linked to the strength of EEG brain waves, will be a “good first clue.”

Reset the brain

During sleep, people go through a two-phase cycle: rapid eye movement (REM) sleep and non-REM sleep. During slow-wave sleep in particular, the brain reduces the strength of synaptic connections—which occur when neurons interact—by decreasing the intensity of less relevant connections and chemical signals. This helps maintain balance and prepares the brain to learn new information upon waking.

Anika Löwe explains that there are two theories. The first suggests that only irrelevant synapses are weakened, preserving important connections. The other proposes a widespread reduction of all synapses, which is a "reset" of the system. The cognitive and neural mechanisms underlying intuition, however, are still debated, which has attracted the interest of researchers for quite some time.

Odiette participated in a similar study in 2021 that argues that light sleep—which occurs just before we fall deeply asleep—can help with problem solving. The scientists were inspired by Dalí and Thomas Edison , who believed that creativity could be boosted by sitting comfortably in a chair with an object in their hand, which falls to the floor, waking them up as soon as they fall asleep. Although they found a significant effect for N1 sleep, this was not the case for N2 sleep when it came to solving the task. Other studies from 2018 and 2020 , on the contrary, found no benefits of sleep for eureka moments or reported no differences between sleep and waking rest.

In any case, for Odiette, there's one clear point on which both analyses agree: "If you want to use a micronap in your life, it can benefit at least two types of creative tasks, even if you don't know what stage [of sleep] you're in," she suggests. Perhaps that's why da Vinci slept in fragments. Or why Dalí fell right on the edge of sleep. They weren't escaping the world. Maybe they were busy dreaming and searching for another way to see it.