In the previous parts of this series, we explored how premium slumber can make you perform better physically, stay emotionally stable, and help avoid illness and injury. For this final installment, let’s look at how getting long, high-quality sleep can also make you smarter, more focused, and mentally sharper.

Memory is one of the best measurements of cognitive impact. As philosopher Alan Watts once said, “A person who had total amnesia and lived in a split second only wouldn’t know he was there.” One of the ways that we put the world around us into context is to recall where we’ve been, what we’ve done, who we’ve done it with, and so on. Memory is also essential in acquiring new skills and developing existing ones.

A paper released via PLOS ONE concluded that when participants slept well, they could recall information 20.6 percent more effectively. This shows the connection between slumber and declarative memory – i.e., the capacity to recall facts.[1] Another study published in Physiological Reviews asserted that consistently getting high quality and sufficiently long sleeps can positively impact other forms of memory, including the episodic kind that reminds us what’s happened in our lives up until now: “During sleep, reactivation of the episodic memory originating from hippocampal networks results in the activation of the different memory parts also at the cortical level, thereby successively strengthening cortico-cortical connections and transforming the temporary representations into long-term memories,” the authors wrote.[2] They also stated that sleep improves semantic memory, which Psychology Today defines as “a form of long-term memory that comprises a person's knowledge about the world.”[3]

More Sleep = Better Mental Performance

Many studies that observe the impact of sleep on cognition do so with theoretical measures of brainpower. But a study led by two MIT professors concluded that there’s a very strong correlation between college students’ sleep habits and their grades. Publishing their results in Science of Learning, the researchers noted that when students consistently got good sleep, they performed better on tests than when they didn’t.[4] Commenting on the study for an MIT News article, study co-author Dr. Jeffrey Grossman said, “The night before [a test] doesn’t matter. We've heard the phrase ‘Get a good night’s sleep, you've got a big day tomorrow.’ It turns out this does not correlate at all with test performance. Instead, it’s the sleep you get during the days when learning is happening that matters most.”[5]

While college students aren’t exactly known for keeping early hours, the MIT trial found that they might not want to burn the midnight oil as much, at least not if they want to keep their GPAs up. Even if students got seven hours of sleep or more, if they went to bed after 2 AM, their academic performance still slipped.

“When you go to bed matters,” Grossman explained. “If you get a certain amount of sleep — let’s say seven hours — no matter when you get that sleep, as long as it’s before certain times, say you go to bed at 10, or at 12, or at 1, your performance is the same. But if you go to bed after 2, your performance starts to go down even if you get the same seven hours. So, quantity isn’t everything.”

Explaining Creative Breakthroughs

Have you ever wondered how you couldn’t solve a thorny problem despite thinking hard about it for weeks and then all of a sudden, one day the answer comes to you unbidden? In his book Why We Sleep, Dr. Matthew Walker explains that such a eureka moment is no accident:

“NREM sleep helps transfer and make safe newly learned information into long-term storage sites of the brain. But it is REM sleep that takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography. These mnemonic collisions during REM sleep spark new creative insights as novel links are forged between pieces of information. Sleep cycle by sleep cycle, REM sleep helps construct vast associative networks of information within the brain. REM sleep can even take a step back…and divine overarching insights and gists…”[6]

What if you can’t sleep well at night before your neighbor’s dog won’t stop barking, your baby gets you up over and over, or you just lie there ruminating? Don’t despair – just nap. A Chinese study found that when older folks got a little afternoon shuteye, they had “better cognitive function, including orientation, language, and memory.”[7]

Miss the previous parts of this series? Click the links below to catch up. And if you need help dialing in your sleep, hit us up.

The Mental Health Benefits of Getting Better Sleep

3 Physical Advantages of Sleeping Well

How to Solve Your Sleep Problems


[1] Katya Trudeau Potkin and William E Bunney Jr, “Sleep Improves Memory: The Effect of Sleep on Long Term Memory in Early Adolescence,” PLOS ONE, August 7, 2012, available online at

[2] Björn Rasch and Jan Born, “About Sleep's Role in Memory,” Physiological Reviews, April 2013, available online at

[3] “Semantic Memory,” Psychology Today, available online at

[4] Kano Okano et al, “Sleep Quality, Duration, and Consistency are Associated with Better Academic Performance in College Students,” Science of Learning, October 2019, available online at

[5] David L Chandler, “Study: Better Sleep Habits Lead to Better College Grades,” MIT News, October 1, 2019, available online at

[6] Matthew Walker, Why We Sleep (New York: Scribner, October 2017), 75.

[7] Han Cai et al, “Relationship Between Afternoon Napping and Cognitive Function in the Ageing Chinese Population,” General Psychiatry, January 25, 2021, available online at


Timothy DiFrancesco

Tim DiFrancesco, PT, DPT spent 6 seasons as the Head Strength & Conditioning Coach of the Los Angeles Lakers and is the founder of TD Athletes Edge. He is nationally renowned for his evidence-based and scientific approach to fitness, training, nutrition, and recovery for athletes and fitness enthusiasts.

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