Focusing your attention brings something into your temporary working memory. But for that “something” to move from working memory to long-term memory, two things should happen: the idea should be memorable (there’s a gigantic flying mule braying f = ma on my couch!), and it must be repeated. Otherwise, your natural metabolic processes, like tiny vampires, simply suck away faint, newly forming patterns of connections. This vampiric removal of faint patterns is actually a good thing. Much of what goes on around you is basically trivial—if you remembered it all, you’d end up like a hoarder, trapped in an immense collection of useless memories.

If you don’t make a point of repeating what you want to remember, your “metabolic vampires” can suck away the neural pattern related to that memory before it can strengthen and solidify.

Repetition is important; even when you make something memorable, repetition helps get that memorable item firmly lodged in long-term memory. But how many times should you repeat? How long should you wait between repetitions? And is there anything you can do to make the repetition process more effective?

Research has given us helpful insight. Let’s take a practical example. Say you want to remember information related to the concept of density—namely that it is symbolized by a funny-looking symbol, ρ, which is pronounced “row,” and that it is measured in standard units of “kilograms per cubic meter.”

How can you conveniently and effectively cement this information into memory? (You know now that placing small chunks of information like this in your long term memory helps gradually build your big-picture understanding of a subject.)

You might take an index card and write “ρ” on one side and the remaining information on the other. Writing appears to help you to more deeply encode (that is, convert into neural memory structures) what you are trying to learn. While you are writing out “kilograms per cubic meter,” you might imagine a shadowy kilogram (just feel that mass!) lurking in an oversized piece of luggage that happens to be a meter on each side. The more you can turn what you are trying to remember into something memorable, the easier it will be to recall. You will want to say the word and its meaning aloud, to start setting auditory hooks to the material

Next, just look at the side of the card with the “ρ” on it and see whether you can remember what’s on the other side of the card. If you can’t, flip it over and remind yourself of what you are supposed to know. If you can remember, put the card away.

Now do something else—perhaps prepare another card and test yourself on it. Once you have several cards together, try running through them all to see if you can remember them. (This helps you interleave your learning.) Don’t be surprised if you struggle a bit. Once you’ve given your cards a good try, put them away. Wait and take them out again before you go to sleep. Remember that sleep is when your mind repeats patterns and pieces together solutions.

Briefly repeat what you want to remember over several days; perhaps for a few minutes each morning or each evening, change the order of your cards sometimes. Gradually extend the times between repetitions as the material firms itself into your mind. By increasing your spacing as you become more certain of mastery, you will lock the material more firmly into place. (Great flash card systems like Anki have built in algorithms that repeat on a scale ranging from days to months.)

Interestingly, one of the best ways to remember people’s names is to simply try to retrieve the people’s names from memory at increasing time intervals after first learning the name. Material that you do not review is more easily discounted or forgotten. Your metabolic vampires suck away the links to the memories. This is why it’s wise to be careful about what you decide to skip when reviewing for tests. Your memory for related but nonreviewed material can become impaired.