How Long-Term Memory Retention Works

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The question of memorization—or, couched in the terms of learning and memory theory, “long-term retention”—is essentially a battle with our tendency to forget.  Not only that, but because memorization is the absence of forgetting, it is painfully slow and unreliable by design.  Whereas it only takes a moment to forget a fact, remembering it is an arduous process that is never over.  As educators or learners, our work is cut out for us.

Making Long-Term Retention Work for You


Forgetting has been described as an adaptation that allows us to cope with the slew of demands on our attention by allowing irrelevant information to recede to the background1.  All organisms (with a few exceptions here and there) forget things rather quickly.  If we didn’t forget—the evolutionary argument goes—we would be burdened by irrelevant facts and helpless to go about our lives.

Forgetting happens extremely quickly after an initial presentation of a fact or number.  It takes just 10 minutes to forget a vocabulary word in a foreign language, and non-linguistic data—such as a seven-digit phone number—can be gone in the blink of an eye.  Psychologists as well as computer scientists talk about the “memory trace” of an activated fact; with time, the activation (corresponding to likelihood or speed of recall) dwindles to nothing.


The question, then, is what to do about it?  Studies have shown that the single best way to avoid forgetting information is exposure to it2.  In other words, rather than relying on newer, fancier ways to absorb it, simply absorb it more.  Moreover, the number of presentations of a fact is a better indicator of long-term retention than the cumulative time spent studying it—12 five-minute sessions are much better than an hour at once if your goal is to retain that fact for a long time3.

This is all well and good—we’ve been told this in school before in the guise of “Don’t cram” injunctions.  But technology has finally progressed to the point where, thanks to confidence-based repetition (CBR) systems such as Brainscape, there are ways to avoid reviewing entire swathes of material and instead to focus on only those facts that are in danger of being forgotten.

Confidence-based repetition

The reason CBR is so useful is that rather than reviewing, say, all the material for an upcoming test at once, it tracks each specific fact’s memory trace and, when that trace is getting dangerously low, targets that specific fact for presentation.  When you combine this time-saving innovation with CBR’s reliance on confidence, rather than true testing, the result is blisteringly fast rates of memorization compared to traditional flashcards or reviewing notes.


1. Altmann, E.M., & W.D. Gray (2002).  Forgetting to remember: The functional relationship of decay and interference.  Psychological Science, 13(1), 27-33.

2. Karpicke, J.D., & H.L. Roediger III, (2007).  Expanding retrieval practice promotes short-term retention, but equally spaced retrieval enhances long-term retention. Journal of Experimental Psychology: Learning, Memory, and Cognition. 33(4), 704-719.

3. Nelson, T.O., & R.J. Leonesio, (1988).  Allocation of self-paced study time and the “labor-in-vain” effect.  Journal of Experimental Psycology: Learning, Memory, and Cognition. 14(4), 676-686.

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1 comment

SoulFireMage 7 years ago

What about contextual reinforcement, otherwise known as integrated web of understanding.

For example, if you know how a scheme of naming works, and have memorised it's roots, you can remember by understanding or derivation.

E.g peri ventricular (surrounding ventricles). Anatomy using, I guess, location, path way origin and destination and function in a triad of meaning. Btw, I'm not a doctor so please forgive me if this is not quite right.

If you understand something, is it not more efficient than pure memorisation?

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