Sleep on it – in the morning you will know what to do:

We often wrestle with a problem or cannot make up our minds about a decision to be taken, then decide to sleep on it.  The next morning, we usually have clarity on what to do.   But how does it work?

What happens in the brain to help solve problems while you sleep?

The brain can be compared to an extremely powerful computer, consisting of an estimated 160 billion brain cells – probably equal to the number of stars in the Milky Way.  In addition, the human brain is the most sophisticated, complex system in the known universe.

While we sleep, the brain does maintenance, such as sorting and storing new information.  It seems as if the reorganizing and consolidation of information during sleep may facilitate problem-solving activities at the same time.  Sleep offers a period of isolation from external influences on the brain.  Theory has it that the brain replays ideas or problems it has encountered during the day, and as the brain is not bogged down with many other tasks while we sleep, the brain may come up with new solutions.  Misleading or unimportant information are being forgotten while we sleep, which may contribute to viewing a problem with a fresh mind in the morning.

Researchers have found that the sleep phase where dreaming occurs, called Rapid Eye Movement sleep (characterized by the rapid roving movements of the eyes) plays a crucial role in integrating previously encountered information, and creative problem solving.

Research into the brain’s problem-solving abilities during sleep:

The brain’s ability to deal with problems while we sleep has intrigued scientists in the fields of neuroscience and psychology, leading to various studies in this regard.  Without going into the details of these research projects, some of the findings makes interesting reading.

One of these studies (reported in Medical News Today) found that sleep can be manipulated to assist with finding solutions which were elusive while the participants were awake.  Participants in the study were exposed to unique sounds while trying to solve puzzles during the day.  These sounds were softly repeated during the night, in an effort to recall these puzzles to the attention of the sleeping mind.  In the morning, the participants showed a 55% improvement on solving more of the puzzles cued by sounds during sleep, compared to solving puzzles not being accompanied by the unique sounds during the night.

While pairing sounds with sleep may play a role in manipulating the brain’s problem-solving abilities while asleep, research has shown that pairing smell with sleep can also play a role.  Learning Scientists reports a study where participants were expected to come up with as many creative solutions to a problem as possible.  While playing a video clip introducing the problem to the participants one evening, a vanilla scent was sprayed into the room.  Participants were sent home, each with an envelope, with the instructions to open and read the contents (a reminder of the problem shown in the video) before going to bed.  Participants were divided into 3 groups – one group received a vanilla scent diffuser, the second group a diffuser with a different scent, while the third group did not receive a diffuser to be activated during the night.  The next day the participants who received the vanilla scent diffuser came up with more creative solutions than the other groups.

Participants in a study (also reported in Learning Scientists) played a difficult video game, in which they reach an impasse and could not proceed any further.  One half of the participants were allowed a 60-minute nap while the rest stayed awake.  Those who took a nap were twice as likely to solve the puzzle in the videogame than the participants who stayed awake.

Another study (reported in PubMed) found that a greater number of difficult problems could be solved after sleep, but sleep made no difference to the solving of easy problems.


The research results demonstrate that brain processing during sleep is conducive to daytime cognition and that creative solutions to problems may well be enhanced through sleep.  When you choose to sleep on a difficult decision or a nagging problem, the chances are that you will wake up with a clear view of the problem and be surprised with the solutions you can come up with.

Sleep on it – the brain already has all the information and sleep will help to put it together! 


The science of “sleeping on it”.  Published 24 October 2019.  Elemental.  (A publication from Medium about health and wellness.)  (

Researchers activate problem-solving during sleep.  Published 27 October 2019.  MedicalNewsToday.  (

What happens in the brain when we sleep?  Published 6 August 2020.  MedicalNewsToday.  (

Sleep on it, but only if it is difficult: effects of sleep on problem-solving.  Published February 2013.  PubMed.  National Center for Biotechnology Information.  US National Library for Medicine. National Institutes of Health.  (

Trying to solve a problem?  Sleep on it.  Published 12 January 2021.  The Learning Scientists.  (An organization of cognitive psychological scientists who make scientific research on learning more accessible.)  (

Sleep to solve a problem.  Published 24 May 2021.  Harvard Health Publishing.  Harvard Medical School.  (

Can we convince the sleeping brain to process our problems?  Published 26 December 2020.  Slate.  (A daily magazine on the Web.)  (


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