This concept is sometimes called the Forgetting Curve and is described by an formula. See http://en.wikipedia.org/wiki/Forgetting_curve http://en.wikipedia.org/

This concept is sometimes called the Forgetting Curve and is described by an formula. See http://en.wikipedia.org/wiki/Forgetting_curve http://en.wikipedia.org/wiki/Forgetting_curve Also see http://en.wikipedia.org/wiki/Spaced_repetition http://en.wikipedia.org/wiki/Spaced_repetition