The Importance of Sleep for Memory and Cognition
By: Cindy Wooldridge
As noted in a recent weekly digest, sleep is vital for health. The risks of sleep deprivation include an increased chance of weight gain, and developing illnesses such as the common cold, heart disease, and diabetes, as well as the more readily experienced impairments to attention, problem-solving, and decision making (1). Importantly, these risks increase with even mild sleep deprivation of 1-2 hours per night (that’s about 6 hours of sleep). While you are hopefully convinced that sleep is important for many reasons, our focus as learning scientists is on cognition and the ability to learn and remember, so for this blog post I will describe one particular study demonstrating the effect of sleep on learning.
Evidence that sleep aids learning
In order to examine the effect of sleep on classroom learning, Scullin and colleagues (2) gave undergraduate students with no previous exposure to economics a lecture on supply and demand. Students were randomly assigned to one of two groups. The first group watched the lecture in the morning and came back in the evening to take a test. The second group watched the lecture in the evening and came back in the morning to take a test. In this way, the time from lecture to test was held constant, but only the second group slept in between the lecture and test. The test was divided into two parts. Half of the questions were very similar to the types of supply and demand questions that were used as examples during the lecture. The other half of the questions were called “integration” questions that required students to incorporate both supply and demand information to solve novel complex problems.
The results showed that students in the sleep group performed about 8% better on the problems that were similar to those from the lecture. But on the novel problems, students who had gotten sleep before taking the test performed 32% higher than those who had not slept! In other words, students retained more information after sleeping, but their ability to understand and apply that information received the biggest benefit with sleep.
Why does sleep aid learning?
One of the common misconceptions about sleep is that it is simply a restful time when nothing is happening, or in other words, that the brain is quiet. Quite to the contrary, the sleeping brain is very active, sometimes more so than during waking hours. The brain cycles through several different types of sleep throughout the night, sometimes with very fast activity and sometimes with what is called slow wave sleep. (For more information on the different stages of sleep, please visit helpguide.org.) It is during slow wave sleep that the brain appears to replay the information that was learned while awake, which leads to consolidation of memories – moving them into long-term storage (3). Because the brain cycles through the different stages of sleep throughout the night, losing sleep means losing time for consolidation.
So, bottom line...
Students: Sleep is the easiest way for you to study. Getting a good night’s sleep will help considerably with retaining information in class, understanding that information, and learning new information. In other words, you are much more likely to do well on ANY kind of test if you get a good night’s sleep every night (not just the night before the exam, although that night is important too).
Parents: Take sleep seriously. Bedtime is important at all stages of life and protecting your child’s health has become more difficult in the age of electronic devices and social media. Try to develop healthy habits in your children regarding bedtime. Good sleep hygiene tips include:
- Aim for 7.5-9 hours of sleep per night. The number of hours needed varies from person to person, but the vast majority of adults need somewhere between 7.5-9 hours in order to function optimally.
- Use the bed only for sleeping. If children (or adults) associate the bedroom with work, socializing, or other “awake” activities, they are less likely to feel relaxed in that space.
- Avoid caffeine late in the day. It takes about 8 hours for caffeine to get through your system. If your child (or you) is having a caffeinated soda with dinner, that will impede the ability to fall asleep at night.
- Set a sleep schedule and stick to it. Our bodies can use time of day to learn when to relax and get ready for sleep, essentially establishing a circadian rhythm. Some research indicates that a steady sleep schedule may be even more important than total sleep time for learning and cognition (4)!
(1) Smith, M., Robinson, L., & Segal, R. (2016, June). How much sleep do you need? Retrieved from http://www.helpguide.org/articles/sleep/how-much-sleep-do-you-need.htm
(2) Scullin, M., McDaniel, M., Howard, D., & Kudelka, C. (2011, June). Sleep and testing promote conceptual learning of classroom materials. Presented at the 25th Anniversary Meeting of the Associated Professional Sleep Societies LLC, Minneapolis, MN.
(3) Wilson, M.A., & McNaughton, B.L. (1994). Reactivation of hippocampal ensemble memories during sleep. Science, 265, 676–679.
(4) King, E., & Scullin, M. K. (March, 2016). Assessing sleep patterns in interior design students: A pilot study. Interior Design Educator’s Council Conference, Portland, OR.