Is there any merit to the advice to ‘sleep on it?’ New research suggests our dreams may help problem-solve

LISTEN | Full interview with Karen Konkoly and Valentina Elce:

If you’ve ever struggled with making a decision, you may have been advised to “sleep on it.”

The idea is that a new insight might arrive when you wake up, because your subconscious mind works while you are at rest. 

A pair of recent studies suggest that age-old advice may in fact be grounded in science.

One of the studies found that what you think about during the day has a big influence on what you dream about at night.

“There are many hypotheses about why we dream … dreams might help us to process the experiences and the emotional charge that we have during the day,” Valentina Elce, a cognitive neuroscientist at the University of Freiburg, told Bob McDonald, host of Quirks & Quarks.

Elce’s recent study, published in the journal Communications Psychology in April, suggested that our daily activities are represented in our dreams, though they are reinterpreted in highly metaphorical ways. 

The study ran from 2020 to 2024 and detailed the daily lives and nightly dreams of more than 3,000 participants aged 18 to 70.

Elce’s study also suggested that attention span affects how you dream. For example, those who tend to daydream or let their minds wander more during waking hours have shorter, more fragmented nighttime dreams.

By contrast, people who give importance to their nighttime dreams — by doing things like talking about them, and trying to remember them — tend to have more vivid, complex dreams.

It’s not clear, however, whether it’s the interest in dreams that drives the dream experience, or if having vivid, colourful dreams makes you more interested in them, says Elce.

Either way, if you want more from your dreams — including potential answers to your problems — it helps to optimize your chances of remembering them. Elce says she recommends developing the habit of logging what was going through your mind every day as soon as you wake up, even if it’s simply to say you don’t remember what you dreamt. 

“Doing this every day will make you remember more dreams,” said Elce. “It worked on more than 200 people. I had no participants who didn’t remember.”

Optimizing sleep for creativity

The second study reported on experiments with “dream engineering,” a subfield of dream research that involves manipulating people’s dreams to learn more about them.

Researchers from Northwestern University tried to verify if dreams can help provide solutions to creative problems.

How we spend the minutes before we go to sleep sets the stage for what we dream about.– Karen Konkoly, cognitive neuroscientist, University of Cambridge.

Published in the journal Neuroscience of Consciousness earlier this year, the research was led by cognitive neuroscientist Karen Konkoly, now a post-doctoral research fellow at the University of Cambridge. She says sleep may in fact help some people solve the problems they’re working on. 

“One reason is because it allows your fixation on the wrong solution to fade … and it allows your networks in your brain to be more loosely activated,” Konkoly said.

Konkoly recruited participants who were lucid dreamers, so they could interact with them during the dream. Lucid dreamers are aware that they are dreaming and can control the dream to some extent, while remaining asleep. 

In Konkoly’s study, participants were given brain teaser riddles to solve before going to sleep. For example, in one puzzle, they were given 11 matchsticks and asked to make nine. (The answer is to spell out NINE with the matchsticks.)

The researchers found that “if somebody dreamt of a puzzle, they were more likely to solve it. So puzzles that weren’t dreamt of were solved less than 20 per cent of the time, and puzzles that were dreamt of were solved more than 40 per cent of the time,” she said.

However, they didn’t solve the puzzles while they slept. The solutions usually came to participants in the following days. 

Music and other sound effects were played while they worked, which the researchers used as auditory cues later in the experiment. The participants slept for six hours. Then during a lucid dreaming training session, the same music was played to encourage the dreamer to think of the puzzle. 

“We found that presenting the sound cues during sleep did indeed cause people to dream more about those puzzles,” Konkoly said. 

Tore Neilsen, director of the Dream and Nightmare Laboratory at the Universite de Montreal, who was not involved with this study, said it supported the notion that dreaming serves a role in “offline problem-solving.”

But it didn’t rule out the possibility that some “REM sleep process critical for problem solving” might also be involved. REM, or rapid eye movement, is the period of sleep when dreaming occurs, and a person’s brain waves are similar to when they’re awake.”

If you want to influence your own dreams, there are ways to do so, says Konkoly.

“How we spend the minutes before we go to sleep sets the stage for what we dream about. So if you read a really good book or if you watch a scary movie or scroll or listen to a beautiful song. All those are already ways that you can engineer your dreams.”