Leitner system

[4][5] It is a simple implementation of the principle of spaced repetition, where cards are reviewed at increasing intervals.

In this method, flashcards are sorted into groups according to how well the learner knows each one in Leitner's learning box.

Each succeeding group has a longer period before the learner is required to revisit the cards.

Only when a partition became full was the learner to review some of the cards it contained, moving them forward or back depending on whether they remembered them.

The advantage of this method is that the learner can focus on the most difficult flashcards, which remain in the first few groups.

Ideas similar to these have been implemented into a number of computer-assisted language learning and flashcard software.