No. 7:  The Rule of Sleep

     Why is 'sleep' one of the seven eight rules?  Because sleep is essential (or nearly so) for most kinds of learning.  If you manage your sleep, you can manage your learning better.

     While it still isn't clear just why we need to sleep (or die), it is very clear that sleep helps to consolidate or 'improve' memory and performance.  In multiple studies on humans and other animals, if you provide a task, allow some training, and test again after sleep, people improve.  If you test again without sleep, people have not improved beyond where they were at the end of practice.  (This is just as true for skill memory, such as how to shoot a basketball, as it is for other learning tasks.)  If a person is in 'sleep debt' (suffering from lack of sleep), then only the most recent activities are likely to be consolidated into longer-term memory or improved during sleep (and often not very much).  The earlier material appears to be brushed aside and largely ignored.

    If you test performance after lack of sleep, problem solving skills are harmed most.  Recall of long-term memory is next most harmed.  Recall of short-term memory appears to be least affected.  In other words, cramming might work, as long as the test is simple facts and recall, and as long as you can cram in enough to make it through the exam.  Unfortunately, cramming without sleep is not likely to put what you've learned into long-term memory.  If your goal is to get smarter over time, cramming is a terrible strategy.

So this suggests a few things.
  1. Sleep after studying something and you'll remember more.
  2. If you are in sleep debt, sleep soon after you learn or practice. Don't allow any later activity displace the things you wanted to remember.
  3. If you need to solve complex problems on an exam, you'll need sleep. If you just need to recognize words or repeat simple memorized facts, cramming may be enough to earn you the grade.
  4. If you need to recall and make connections with information you learned weeks or months ago, you'll need more sleep than if you just need to recognize words or repeat simple memorized facts.
  5. As was pointed out by one of my students, "Yes, I know that I would test better if I had slept.  It's just that I find I do better if I've seen the material but not slept than if I've slept but haven't seen the material." Hmmm.

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Last updated  12/01/2009
College of William and Mary, Department of Biology

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