The Scientific Reason Sleep Helps Us Make Better Decisions

When your life is jam-packed with activity, it's tempting to cut back on sleep. Sleep isn't just a passive activity, though. Your brain does a lot of processing of your daily experiences to help form memories. Sleep allows your brain to clear out toxins so you can start the next day fresh. If you don't get enough sleep, you might not be able to concentrate and make good decisions. Instead, you rely on cognitive shortcuts called heuristics, which can bias your decisions.

A 2024 study in the Journal of Experimental Psychology: General looked at how first impressions can cause people to make incorrect decisions. The researchers created a virtual garage sale with boxes of items that varied in value. Although each box had the same total value, some boxes had more valuable items placed on top.

When people were asked to assign value to the boxes, they tended to assign a higher value to the boxes that had valuable items on top. Their first impressions of the box biased their decisions, leading to incorrect judgments. When people were asked to "sleep on it" and decide the values of the boxes the next day, they made more correct valuations of the boxes. In other words, they made more rational decisions without the first impression bias.

Missing out on sleep affects certain neurons in your brain that help assess danger and react to threats, according to a 2023 article in NeuroSciences. You're also disrupting the release of neurotransmitters, making it harder for them to function properly. As a result, your thinking and decision-making become impaired. A lack of sleep can cause problems with memory, attention, and alertness. (Here's how your body says you're not sleeping enough.)

A lack of sleep can make you more impulsive. A 2011 study in Behavioral Brain Research found that one night of sleep loss can heighten your sensitivity towards negative events. As a result, you're more likely to make quick, incorrect decisions and less likely to hold back your response.

If you encounter an important moral judgment, you might want to sleep on it first. A 2007 study in Sleep had people face moral dilemmas after two nights of sleep deprivation. The lack of sleep caused people to take longer to decide on an emotion-evoking moral dilemma, and the researchers said this longer response time meant they had a harder time making the decision.

Most adults need between seven and nine hours of sleep every night to restore thinking and prevent chronic health issues. While an occasional sleepless night is normal, regularly getting fewer hours of sleep or too much sleep during midlife and beyond can affect your cognition, according to a 2014 study in the Journal of the American Geriatrics Society. Women who slept less than five hours or more than nine hours each night had worse cognitive function than women who slept seven hours. The cognitive decline was similar to aging two additional years.

Children need more sleep depending on their age. The National Heart, Lung, and Blood Institute recommends up to 14 hours of sleep every night for children 1 or 2 years old, but children between the ages of 6 and 12 need up to 12 hours. According to a 2018 study in Sleep Health, most children don't get the recommended amount of sleep, which can affect their IQ. Children tend to have better cognitive functioning when they sleep longer.