Spaced repetition memory system

A spaced-repetition memory system combines the Testing effect and the Spacing effect to enable efficient memorization of many thousands of facts (Spaced repetition memory systems are extremely efficient). Some people also use them for a broader set of tasks (see below). Spaced repetition memory systems make memory a choice, but they’re not just for rote facts: Spaced repetition memory systems can be used to develop conceptual understanding.

The first consumer system of this kind was Supermemo, created by Piotr Wozniak. It adopted and popularized the term “spaced repetition”; prior literature had used a variety of terms (often referring to more specific facets of the underlying phenomenon).


Branwen, G. (2009). Spaced Repetition for Efficient Learning. Retrieved December 16, 2019, from

Who invented the name: spaced repetition? -

* I’ll summarize just the second experiment, since it’s more relevant to the kind of Spaced repetition memory system design I’m doing. Students who practiced via short-answer enhanced their recall the most relative to a control condition and a condition in which students simply read the correct answers. Short-answer-practicing students performed better than those who practiced via multiple-choice on a multiple choice post-test (d=0.41) but not significantly better than MC-practicers on a short-answer post-test.

  • [[Karpicke, J. D., & Smith, M. A. (2012). Separate mnemonic effects of retrieval practice and elaborative encoding. Journal of Memory and Language, 67(1), 17–29.]]
* Is the Testing effect produced by Elaborative encoding? When you review prompts in a Spaced repetition memory system, you give yourself an opportunity to form new connections based on your current context and the different thoughts you have during the review session.]]
* This paper attempts to produce a better scheduler for a Spaced repetition memory system by combining a model-based (per-student, per-item) estimator of student memory state, with a more holistic planning model which attempts to take students’ time constraints and test date into account.