Why do we sleep? That's one of the many mysteries of the human body. And while we can hypothesize about why we sleep through the lens of evolutionary psychology, we also have a substantial body of research on what happens if we don't get enough sleep.
You might be tempted to pull an all-nighter here and there. In fact, a fifth of students do so at least once a month. Yet, lack of quality sleep can be detrimental to your memory, cognitive abilities, and, therefore, your academic performance. What is the ability to recall information, and what does it have to do with sleep?
Let's explore why getting enough sleep is so important by taking a deep dive into the body of research from an archived article by Kelly Cappello, B.A., at the University of Pennsylvania.
3 Components of Learning
Your brain employs three distinct processes to learn new information through the sleep memory connection.
Acquisition
This is the process of receiving information from external sources (e.g., dates in a history textbook) or your attempts to complete a task (e.g., experimenting while painting). The acquired information is encoded and moved to the hippocampus for short-term storage.
Consolidation
Memory consolidation involves connecting the newly acquired knowledge with existing one and moving it to long-term storage. The more connections your brain makes, the easier it'll be to recall and use the learned information later on.
Recall
When you try to access the material you've learned, your brain is recalling it. If it's properly consolidated into the memory, recall is easy. The frequency of recall also impacts retention; in other words, if you don't use the learned information, you'll find it more difficult or impossible to remember.
How Does Sleep Affect Memory and Learning?
Ever found it hard to concentrate because of a poor night's sleep? That's because lack of quality sleep affects your cognitive capabilities, including the ability to focus and process information. That, in turn, gets in the way of effective information acquisition, the first part of any learning process.
On top of that, recall also requires concentration. So, you need to be well-rested to access your knowledge with ease.
That said, the impact of sleep goes deeper than the state of your cognitive abilities while you're awake. When you're asleep, your brain organizes and consolidates information for long-term storage. So, if you don't get enough sleep, especially slow-wave sleep, you're less likely to retain the acquired information, no matter how hard you try to memorize it.
Numerous studies demonstrate two facts: memory consolidation occurs only during sleep, and sleep deprivation substantially hinders memory formation. That applies to both semantic (knowing facts) and procedural (knowing how to complete certain tasks) memory.
What's more, if you don't get enough sleep after a productive study session, you can't compensate for it later on. The window of opportunity for your brain to consolidate memories will be closed.
How Sleep Impacts the Ability to Recall Information
While the role of sleep in memory consolidation is the most pronounced (and the most well-documented), sleep also plays a role in memory retention and recall.
What is the ability to recall information? It is the process of retrieving stored information from the past.
There's anecdotal evidence showing that we've known about the importance of sleep for recall for thousands of years. In the first century AD, rhetorician Quintilian was behind the earliest known record of it, stating that "[...] the interval of a single night will greatly increase the strength of the memory."
Modern research indicates that slow-wave sleep (a.k.a. Stage 3, or deep sleep) is the most essential one for improving retention and recall. Overall, different studies have shown that a good night of sleep can boost retention and recall by anywhere between 20% and 40%.
Note: Slow-wave sleep occurs after your body goes through the first two stages of the cycle, which takes 30 to 35 minutes, on average. The slow-wave stage itself lasts from 20 to 40 minutes per cycle.
How Sleep Affects Long-Term Memory
During sleep, your brain reexamines the information kept in the hippocampus (your short-term memory storage), organizes and consolidates it, and moves it to the cortex (long-term storage). That happens during slow-wave sleep.
Needless to say, if you don't give your brain the time to do all that work, the information won't be filed away in long-term storage. So, you'll probably forget it sooner rather than later, making it difficult to build on the knowledge later.
What's more, sleep also enables your brain to filter information, essentially choosing what'll be useful in the long run (and thus worth preserving in long-term memory). This happens before your brain enters the slow-wave stage, during stage 2 non-REM (NREM) sleep.
Filtering information is crucial overall, but it's even more so before exams. After all, exams don't test for everything; they only verify you've learned the most important material covered. The stage 2 non-REM sleep will help you separate the important from the not-so-important.
How Sleep Influences Critical Thinking & Problem-Solving
Yes, sleep is instrumental beyond improving your ability to memorize information. Recent studies indicate that proper sleep hygiene can also help you strengthen critical thinking and creative problem-solving skills.
These soft skills, in turn, are important in virtually every domain. Whether you're tasked with writing an essay or solving a math problem, you'll need them. They're enabled by your associative memory, which helps you put the pieces together.
Researchers hypothesize that the REM stage, the final one in the sleep cycle, impacts the ability to solve problems creatively the most. For example, one study tested the participants' problem-solving skills when woken up during NREM or REM sleep and during the day. The participants who were woken up during REM sleep solved 15% to 35% more anagram puzzles than in other cases.
Note: Most REM sleep occurs in the several final sleep cycles, which is why you need to get between seven and nine hours to get enough of it every night. Keep in mind that alcohol consumption completely blocks REM sleep.
Sleep Deprivation Is Detrimental to Memory & Attention
The fact that 20% of students pull all-nighters at least once a month is alarming because sleep deprivation comes with a wide variety of negative consequences. Even being one sleep cycle short of what you need can lead to:
- Lack of alertness
- Troubles concentrating
- Memory issues
- Agitation
- Moodiness
Overall, not getting enough quality sleep can make you feel tired and more irritable throughout the day. It can also cause poor coordination and make you more forgetful and prone to stress. Chronic lack of sleep can even weaken your immune system, promote weight gain, and increase the risk of cardiovascular disease.
Needless to say, all of these negative effects hinder your ability to learn, make daily tasks more difficult, and threaten your academic performance. Keep in mind that just clocking in 7 hours isn't enough; you need to go to bed early and get quality, uninterrupted sleep.
The Impact of Sleep on Academic Performance
Getting a good night of sleep boosts your ability to pay attention, concentrate, and absorb new information. That, in turn, helps you learn new things more easily. Sleep will also help consolidate that information, move it to long-term memory, and improve retention and recall.
All of that combined means it'll be easier for you to learn new things, remember them in the long run, and use them when the situation calls for it (e.g., during a test).
One study, conducted at MIT, showed a straight-line relationship between grades and the amount of sleep. The students who consistently went to bed before 2 AM and got enough sleep throughout the semester received better grades and test scores.
Interestingly, even naps between study sessions can boost your ability to learn. In one study, the participants who took naps between two sessions were learning as effectively at 6 PM as they did at noon. The other group that didn't take naps experienced a substantial decline in their ability to learn in the evening.
Note: Short naps can boost your alertness and ability to concentrate, but you need to enter the slow-wave stage for memory consolidation to occur. That can happen only during longer naps (60 to 90 minutes).
Can Lack of Sleep Cause Memory Loss?
As lack of sleep hinders the brain's ability to form memories and move them to long-term storage, poor sleep can effectively cause memory issues. Those can involve forgetfulness and memory lapses, meaning you'll find it hard to recall episodic and semantic memories.
It's not just the formation of new memories that's threatened by poor sleep or lack thereof. During sleep, your brain strengthens existing memories to improve their recall. Without a chance to do this kind of upkeep, you may find yourself struggling to remember the things you've already learned.
Perhaps most strikingly, sleep deprivation over a span of a couple of days makes memory loss irreversible. That is, even "catching up" on sleep won't magically help you recall the information that hasn't had a chance to be properly consolidated. So, you'd have to "re-learn" anything that may have gotten lost or fragmented due to poor sleep.
A long history of sleep deprivation makes the impact on your memory even worse. If you spend years not getting enough quality sleep, you may encounter long-term memory issues. Recovery from these issues is usually incomplete.
Sleep Recommendation for Students
Use these tips for improving sleep quality:
- Aim to get between seven and nine hours of sleep every night
- Establish a consistent sleep schedule; stick to it even during weekends and holidays
- Go to bed around the same time every day (ideally, between 10 PM and midnight)
- Limit screen time at least 30 minutes before bedtime
- Avoid coffee, energy drinks, and other stimulants after 3 PM
- Limit alcohol intake to preserve REM sleep
- Manage your academic workload appropriately to avoid having to choose between studying and sleep
- Keep your bedroom dark, silent, and comfy to facilitate falling and staying asleep
- Maintain a cool temperature in the bedroom
- Avoid exercising close to bedtime and napping after noon
In Closing
Sleep and memory go hand in hand. Sleep is the only opportunity your brain has to filter information and consolidate memories; it can't do it while you're awake. That's why sacrificing sleep can be counterproductive if you want to be an effective learner and get good grades.
Now that you know how sleep affects learning, treat sleep as an investment in your academic performance. It'll pay off tenfold as your mind stays sharp throughout the day, helping you absorb new information, solve problems faster, and build on knowledge in the long run.
Keep in mind that getting enough sleep only before a test isn't enough. Research shows that consistency is key in leveraging the benefits we've listed above: improved retention and recall, ability to concentrate, creative problem-solving, and so on.