Spaced retrieval
This article is about a review technique or category/paradigm of review techniques. Review techniques involve doing some form of recall or retrieval for material previously learned. The testing effect is a key observed effect that can be used to understand the effectiveness of review techniques.
View list of review techniques | View summary table of methods of recall
Definition
Spaced retrieval, colloquially called spaced repetition, and also potentially called spaced recall or spaced review, is an approach where material is reviewed at strategic time intervals so as to increase the strength of recall as much as possible. It has two aspects:
- Spacing, where there is a spacing between retrieval attempts; this is based on the testing effect.
- Retrieval, where there is an attempt to recall the information. In general, more active forms of recall work better for retrieval; this is based on the related phenomena of the testing effect, pretesting effect, and generation effect.
The logic for spacing is based on the forgetting curve, where retention decays over time, but the rate of decay gets slower and slower at each successive retrieval. The gap between successive retrievals may vary based on the precise system used; in most systems, the gap is shorter in case of failed retrievals than in the case of successful retrievals. Generally, constant gaps (not growing) are used for failed retrievals, whereas the gaps for successful retrievals may be either constant or grow (with the growth rate anywhere between linear and exponential).
Relation with mode of review
Spaced repetition is a general idea that can be combined with any mode of review. For instance, spaced repetition may be done using a quiz and recall strategy: a list of questions and answers is generated during the original study (or obtained from elsewhere) and the learner quizzes himself or herself using that list of questions after the appropriately spaced intervals. Spaced repetition may also use more active forms of recall (i.e., free recall, such as recursive recall) or more passive forms of recall (such as reading through the learning material again).
The most typical use of spaced repetition is in conjunction with a quiz and recall strategy. Spaced repetition software such as Anki implements flashcards, that are ideally suited for this strategy. The reason for a quiz and recall strategy is that the attempt to actively recall material based on cues can do a better job both of testing one's memory and of increasing its strength. More active forms of recall run the risk of being too difficult for people who have not completely internalized the material, whereas more passive forms of recall run the risk of not strengthening the memory at all because there is no attempt at retrieval.
Systems of spaced repetition
- Leitner system is a simple system that can be implemented relatively easily without computer assistance.
- The Pimsleur language learning system uses a version of spaced repetition.
- Anki is a popular computer software that implements spaced repetition with digital flashcards.