Remembering to do something in the future is called prospective memory. For example, you might decide on the drive to work in the morning that you want to watch the latest episode of your favorite show when you get home at night. In doing so, you are setting an intention (“I want to watch the show”) and its context (“-when I get home tonight”). Prospective memory consists of two components, a retroactive and prospective component. The retroactive component is remembering what you need to do when the time comes, and the prospective component is simply remembering to do that thing when the time comes.
In a recent publication in the journal Memory & Cognition, three researchers from Heinrich-Heine-Universität Düsseldorf set out to study how sleep can help us remember what we need to do in the future. In their study, participants were asked to perform a prospective memory task, by pressing a key when shown a word they had learned a few hours ago. Half of the participants learned the words in the morning and were tested at night, while the other half learned the words at night, and were tested the next morning. The researchers hypothesized that the participants who were tested on the morning of the next day would be better at remembering to press the key on the correct word.
They found that participants did perform better when tested in the morning, but this was not strictly due to sleep. Both groups had actually performed the best when tested in the morning, and the researchers suggest that this effect was due to our attention being refreshed in the morning. Taken together, their findings demonstrate that we are better at remembering to do things in the morning, not because sleep helps us store memories, but because we are more refreshed after a good rest. Translated into practical advice, since our prospective memories are best in the morning, it might be useful to set some reminders for things you intend to do later in the day.