I have been reading a bunch of articles on the SuperMemo site (including the original thesis of P. A. Wozniack, the creator of SuperMemo). I initially started off trying to understand the algorithms SM2,5 and 8 which org-drill implements, but reading the articles has given me a lot of general background and theory on how memory works, and why SuperMemo is as effective as it is (for those who stick with it). This blog post is an attempt to summarize and capture what I have read in all those articles, and not get lost in them. I would recommend reading the thesis and the suggested reading there, yourself, but if you really don’t want to – this blog post + the summary in here, and here would be a good alternative.