Suppose a method let you remember things with a 95% success rate–in other words, whatever information you’ve put into a system, you’d have a 95% chance of recalling it–and this effect is permanent, as long you continue to use the method. That would be quite remarkable, wouldn’t it?

Well, there is such a method, called spaced repetition. This is the method used by such software as Supermemo, Anki, Mnemosyne, and Memrise.

The figure, 95%, is very impressive to me. I’ve been thinking about it lately, as I delve into the world (it is a whole world) of spaced repetition. Ordinarily, we require much less out of our metrics. 95% is practically a guarantee. With just 15 or 30 minutes a day, adding maybe 20 questions per day, you can virtually guarantee that you will remember the answers.

In particular, I am wondering why spaced repetition is not used more widely in education. Of course, I’m not the first to wonder why. The answer is fairly simple, I think.

The more I read from and interact with educationists and even homeschoolers, the more I am struck by the fact that many of them hold knowledge in contempt (q.v.). Of course, they will cry foul if you call them on this (q.v.), but that doesn’t change the fact (q.v.). So naturally I expect them to sneer at me when I express amazement at the 95% recall figure. I can hear the “arguments” already: this is “rote memorization” (not if you understand what you’re memorizing); education is not about amassing mere facts (not just that, no); it suffices that you can just look answers up (wrong); we should be teaching critical thinking, not mere memorization (why not both?).

I am not going to defend the value of declarative knowledge (again) here. I simply wanted to observe what teachers (including homeschooling parents) could do with spaced repetition, if they wanted to. They could spend a half hour (or less) every day adding questions to their students’ “stack” of questions; then assign them to review questions (both new and old) for a half hour.

Imagine that you did that, adding 20 questions per day, five days a week, 36 weeks per year (the usual U.S. school year), for six years. This is not impossible to manage, I gather, and would not take that long, per day. Yet by sixth grade, your students would have 21,600 facts in recall with about 95% accuracy. These would merely be the sorts of facts contained in regular textbooks.

Next, consider an exam that drills on a random selection of 100 of those facts. The students who used spaced repetition faithfully would probably get an A on the exam. That, I suspect, is much better than could be expected even from top students who used ordinary methods of study.

Would students who spent 30 minutes out of every class day on this sort of review benefit from it?

I think the answer is pretty obvious.