Do you ever think about all those college class you took, made good grades on the tests, and now can barely remember what the class was about? Today I came across a fascinating article on memory retention in Wired. A lot of psychological studies show that repetitions over variable intervals are required for retention. Which falls under the maxim "use it or lose it". According to the article the key is to trigger the memory recall at the point just before the memory is forgotten.
The article is about Piotr Wozniak who's worked for decades on an application called SuperMemo which attempts to remind you of these nuggets of information at that point right before it's been forgotten.
The SuperMemo site has a ton of information on factors that affect learning, including one of the most in depth articles on how sleep affects learning I've read.
One poignant quote from the article, "By graphing the acquisition of knowledge in SuperMemo, [Wozniak] has realized that in a single lifetime one can acquire only a few million new items. This is the absolute limit on intellectual achievement defined by death."
