When information is repeatedly learned, it is more effectively remembered when spaced over longer periods of time than shorter periods of time. This effect has been shown to be powerful and very broadly applicable, from animals learning to complete a maze to students scoring higher on tests. The two main theoretical explanations of the spacing effect relate to consolidation and encoding. The consolidation theory argues that information encoded from the first presentation of information is consolidated in the second, while encoding theory argues that encoding is more effective in the second presentation of information. The spacing effect has obvious and important implications in the field of education. However, it still lacks widespread and consistent school usage, so it may be a way to improve education outcomes.
In a study by Bahrick et al., English-speaking subjects learned 300 words in a language other than English. They were given a certain amount of training sessions, spaced over a certain number of days. Having thirteen training sessions across 56 days was equivalent to having 26 training sessions across 14 days, a powerful result.