Need to remember something? Try forgetting it!

A friend recently asked me why our lab is called the “Learning and Forgetting Lab.” He pointed out, “I know learning is important, but why would you study forgetting?”
That is an excellent question. Most people think of forgetting as a negative occurrence to prevent rather than an adaptive, beneficial function. In fact, forgetting something can help you remember it better later on! To see how this works (and learn how to put it into practice), let’s consider the new theory of disuse.

The new theory of disuse (Bjork & Bjork, 1992) modifies Thorndike’s (1914) original law of disuse. The original law proposed that without continued use, memory traces decay as a function of time. Later theorists showed that it is not the passage of time itself that causes forgetting, but rather the interference of other information. The new theory of disuse takes into account the effects of “disuse” as well as interference.

Jeff Bye’s post discussed the new theory of disuse in more detail, so I’m just going to briefly recap it here. Any item you encode into your memory can be described by two characteristics: storage strength and retrieval strength. Storage strength is a general measure of how well learned that item is, while retrieval strength measures how accessible the item is at that time. Storage strength increases monotonically—the more you are exposed to an item, the stronger the storage strength gets. One important thing to note is that storage strength does not have a direct effect on memory performance; the probability that you will be able to reproduce something from memory (e.g., a name or phone number) depends almost entirely on its retrieval strength.

Retrieval strength, unlike storage strength, varies with context and intervening information. This type of strength is what we need to increase if we want to be able to remember an item later. Fortunately, the new theory of disuse proposes a way to do just that: the very act of retrieving an item from memory has a potent effect on its retrieval strength! Note that retrieving is different than studying—in order for retrieval strength to be boosted the most, you need to come up with the item yourself. The real kicker—and where forgetting comes in—is that the more difficult the retrieval is, the more beneficial it will be when you finally do come up with the answer! Thus, the more you forget something, the better you can ultimately remember it. This is part of the idea behind interleaving (alternating topics to learn as in ABCABC instead of AABBCC) and spacing (spreading out study sessions instead of marathon studying)—you need to give yourself time (or, more accurately, some amount of interfering information) to aid forgetting so that you get the most benefit from a retrieval.

This might seem a little backwards, but I hope it will encourage you to structure your learning in a way that allows you to forget just enough information between studying so that you ultimately remember more.



Bjork, R. A., & Bjork, E. L. (1992). A new theory of disuse and an old theory of stimulus fluctuation. In A. Healy, S. Kosslyn, & R. Shiffrin (Eds.), From learning processes to cognitive processes: Essays in honor of William K. Estes. (Vol. 2, pp. 35– 67). Hillsdale, NJ: Erlbaum.

Thorndike, E. L. (1914). The psychology of learning. New York: Teacher’s College.