Students often hear that they should get a good night’s sleep before a test. Even if you load up on coffee and Red Bull to study all night you’ll be wired and stressed, and that certainly isn’t going to help. 
Research has demonstrated that more than leaving you feeling rested, sleep actually improves your memory. Even better, a new study suggests that sleep actually helps you remember exactly what you need to remember.
Participants in the study learned word pairs, picture-location pairs (like the game Memory), or a particular series of button presses that they typed over and over. After learning the material they were tested to get a baseline memory score. Some people learned the material and then went to bed while others stayed awake. The twist was that after learning some found out there would be a test later on; for everyone else it would be a pop quiz. After sleeping, or an equivalent amount of time spent awake, participants were tested the same way as they were for the baseline test.
Participants who stayed awake did about as well as they did at baseline; waiting 8 hours didn’t cause much forgetting regardless of whether or not they knew they would have a test later. Participants who got to sleep and knew a test was coming actually remembered more than they did at baseline, which fits with previous research on the benefits of sleep on memory. More surprisingly, participants who slept but were not expecting a test did not remember any more than they did at baseline. Put another way, sleep boosts your memory but only when you expect to use it.
Not only did expecting a test lead to better memory for sleeping participants, it also changed how they slept. The participants who were sent to bed between learning and test also had electrical activity recorded from their brain while they slept. Their EEG activity showed that participants expecting a test spent more time in slow-wave sleep, which is the deepest kind of sleep and has been associated with improved memory in other studies. It seems that knowing that you’ll need to remember something causes you to sleep differently so that the memories you need become stronger.
This improvement in memory is especially important for students, but it really applies to anyone who needs to remember something. You can take advantage if you’re meeting new people and want to remember their names or even something minor like planning a shopping trip for the next day. Just get the information in, think about the fact that you’ll need to remember it later, and then get to bed. Not only will you have a better chance of remembering what you want, but you might even sleep a bit better too.
Wilhelm, I., Diekelmann, S., Molzow, I., Ayoub, A., Molle, M., & Born, J. (2011). Sleep Selectively Enhances Memory Expected to Be of Future Relevance Journal of Neuroscience, 31 (5), 1563-1569 DOI: 10.1523/JNEUROSCI.3575-10.2011