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Spaced repetition is a memorization technique that works by reviewing question/answer pairs according to a schedule that depends on performance.

Be it software or paper flashcards, there are various techniques to calculate the review schedule. For instance: Leitner, SM0, SM2, ... new techniques appear from time to time. Each new scheduling technique is trying to surpass the others, the goal being to calculate the intervals smartly, for instance so that a question is shown just before the student forgets the fact.

Is there work comparing the "efficiency" of some of those scheduling techniques? (few reviews, well-memorized) Preferably research involving a reasonable number of human experiments.

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Here is a related question that might be of interest. – Artem Kaznatcheev Jun 8 '12 at 16:29
You may find the papers & fulltexts in to be of assistance. – gwern Jun 8 '12 at 18:37

A quick Pubmed search shows a couple of potential useful papers. The more promising:

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From the abstract of the first paper: >> However, there was no evidence that a particular relative spacing schedule (expanding, equal, or contracting) was inherently superior to another. Although expanding schedules afforded a pattern of increasing retrieval difficulty across repeated tests, this did not translate into gains in long-term retention. Repeated spaced retrieval had powerful effects on retention, but the relative schedule of repeated tests had no discernible impact. – William B Swift Jun 9 '12 at 19:59
+1 Could you please identify which part of the second paper (Toppino) is a comparizon of different spacing techniques (like Leitner, SM2, etc)? Thanks! – Nicolas Raoul May 1 '15 at 2:44

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