Spacing effects and their implications for theory and practice

There is considerable evidence, gathered in a variety of settings and across many different types of materials and procedures, that spaced repetitions—regardless of whether they are in the form of additional study opportunities or successful tests—are a highly effective means of promoting learning. Research on spacing effects is reviewed and its theoretical and educational implications are examined. It is concluded that spacing effects can best be understood in terms of the accessibility hypothesis, and that spaced repetitions have considerable potential for improving classroom learning.