Spaced repetition is an evidence-based learning technique that is usually performed with flashcards. Newly introduced and more difficult flashcards are shown more frequently while older and less difficult flashcards are shown less frequently in order to exploit the psychological spacing effect. The use of spaced repetition has been shown to increase rate of learning.
Although the principle is useful in many contexts, spaced repetition is commonly applied in contexts in which a learner must acquire many items and retain them indefinitely in memory. It is, therefore, well suited for the problem of vocabulary acquisition in the course of second-language learning. A number of spaced repetition software programs have been developed to aid the learning process. Alternative names for spaced repetition include spaced rehearsal, expanding rehearsal, graduated intervals, repetition spacing, repetition scheduling, spaced retrieval and expanded retrieval.
Research and applications
The notion that spaced repetition could be used for improving learning was first proposed in the book Psychology of Study by Prof. C. A. Mace in 1932: "Perhaps the most important discoveries are those which relate to the appropriate distribution of the periods of study...Acts of revision should be spaced in gradually increasing intervals, roughly intervals of one day, two days, four days, eight days, and so on."
In 1939, H. F. Spitzer tested the effects of a type of spaced repetition on sixth-grade students in Iowa who were learning science facts. Spitzer tested over 3600 students in Iowa and showed that spaced repetition was effective. This early work went unnoticed, and the field was relatively quiet until the late 1960s when cognitive psychologists, including Melton and Landauer & Bjork, explored manipulation of repetition timing as a means to improve recall. Around the same time, Pimsleur language courses pioneered the practical application of spaced repetition theory to language learning, and in 1973 Sebastian Leitner devised his "Leitner system", an all-purpose spaced repetition learning system based on flashcards.
With the increase in access to personal computers in the 1980s, spaced repetition began to be implemented with computer-assisted language learning § Software-based solutions, enabling automated scheduling and statistic gathering, scaling to thousands of cards scheduled individually.[neutrality is disputed] To enable the user to reach a target level of achievement (e.g. 90% of all material correctly recalled at any given time point), the software adjusts the repetition spacing interval. Material that is hard appears more often and material that is easy less often, with difficulty defined according to the ease with which the user is able to produce a correct response.
There are several families of algorithms for scheduling spaced repetition:
- Neural networks based
- Leitner system: 5 levels and an arbitrary number of stages
- SM-family of algorithms (SuperMemo): SM-0 (a paper implementation) to SM-17 (in SuperMemo 17)
Some have theorized that the precise length of intervals does not have a great impact on algorithm effectiveness, although it has been suggested by others that the interval (expanded vs. fixed interval, etc.) is quite important. The experimental results regarding this point are mixed.
Pimsleur's graduated-interval recall
Graduated-interval recall is a type of spaced repetition published by Paul Pimsleur in 1967. It is used in the Pimsleur language learning system and is particularly suited to programmed audio instruction due to the very short times (measured in seconds or minutes) between the first few repetitions, as compared to other forms of spaced repetition which may not require such precise timings.
The intervals published in Pimsleur's paper were: 5 seconds, 25 seconds, 2 minutes, 10 minutes, 1 hour, 5 hours, 1 day, 5 days, 25 days, 4 months, and 2 years.
Most spaced repetition software (SRS) programs are modeled after the manual style of learning with physical flashcards: items to memorize are entered into the program as question-answer pairs. When a pair is due to be reviewed, the question is displayed on screen, and the user must attempt to answer. After answering, the user manually reveals the answer and then tells the program (subjectively) how difficult answering was. The program schedules pairs based on spaced repetition algorithms. Without a computer program, the user has to schedule physical flashcards; this is time-intensive and limits users to simple algorithms like the Leitner system.
Further refinements with regard to software:
- Questions and/or answers can be a sound-file to train recognition of spoken words.
- Automatic generation of pairs (e.g. for vocabulary, it is useful to generate three question-pairs: written foreign word, its pronunciation and its meaning, but data only has to be entered once.)
- Additional information retrieved automatically is available, such as example sentences containing a word.
- Opportunities to combine spaced repetition with online community functions, e.g. sharing courses.
List of spaced repetition software programs
- Course Hero
- Pimsleur Language Programs
- Pleco Software
- Smolen, Paul; Zhang, Yili; Byrne, John H. (January 25, 2016). "The right time to learn: mechanisms and optimization of spaced learning". Nature Reviews Neuroscience. 17 (2): 77–88. arXiv:1606.08370. Bibcode:2016arXiv160608370S. doi:10.1038/nrn.2015.18. PMC 5126970. PMID 26806627.
- "Human Memory: Theory and Practice", Alan D. Baddeley, 1997
- Mace, C. A. (1932). Psychology of Study. p. 39.
- Spitzer, H. F. (1939). Studies in retention. Journal of Educational Psychology, 30, 641–657.
- Melton, A. W. (1970). The situation with respect to the spacing of repetitions and memory. Journal of Verbal Learning and Verbal Behavior, 9, 596–606.
- Landauer, T. K., & Bjork, R. A. (1978). Optimum rehearsal patterns and name learning. In M. Gruneberg, P. E. Morris, & R. N. Sykes (Eds.), Practical aspects of memory (pp. 625–632). London: Academic Press.
- "Implementing a neural network for repetition spacing". www.supermemo.com. Retrieved July 15, 2017.
- Cull, W. L. (2000). Untangling the benefits of multiple study opportunities and repeated testing for cued recall. Applied Cognitive Psychology, 14, 215–235.
- Chapter 6:Is Expanded Retrieval Practice a Superior Form of Spaced Retrieval?, A Critical Review of the Extant Literature, DAVID A. BALOTA, JANET M DUCHEK, and JESSICA M. LOGAN
- Pimsleur, Paul (February 1967). "A Memory Schedule". The Modern Language Journal. Blackwell Publishing. 51 (2): 73–75. doi:10.2307/321812. JSTOR 321812.
- Gupta, James (January 23, 2016). "Spaced repetition: a hack to make your brain store information". The Guardian. ISSN 0261-3077. Retrieved January 30, 2019.
- Dr Piotr Wozniak (February 1999). "Effective learning: Twenty rules of formulating knowledge". — advice on making flashcards for spaced repetition.