Spaced repetition is a learning technique that incorporates increasing intervals of
time between subsequent review of previously learned material in order to exploit the psychological
spacing effect. Alternative names include spaced rehearsal, expanding rehearsal, graduated
intervals, repetition spacing, repetition scheduling, spaced retrieval and expanded
retrieval. Although the principle is useful in many contexts,
spaced repetition is commonly applied in contexts in which a learner must acquire a large number
of 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, due to the size
of the target language's inventory of open-class words.
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. In 1939, H. F. Spitzer tested
the effects of a type of spaced repetition on sixth-grade students in Iowa 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. To enable the user to reach a target level
of achievement, 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 stages and an arbitrary
number of stages SM-family of algorithms: SM-0 to SM-15
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
is quite important; the experimental data 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
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. By timing a Pimsleur language program with
a stopwatch, it is possible to verify that the intervals are not followed exactly but
have upper and lower bounds. A similar principle is used in at least one open source software
project to schedule audio-only lessons. Software
Most spaced repetition software programs are modeled after the manual style of learning
with 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 how difficult answering was. The program schedules pairs based on spaced repetition
algorithms. Without a program, the user has to schedule 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, 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. Some implementations:
Anki Course Hero
Memorang Memrise
Mnemosyne SuperMemo
Duolingo Revisy
For a broader overview of flashcard software, see list of flashcard software.
Further reading Caple, C.. "The Effects of Spaced Practice
and Spaced Review on Recall and Retention Using Computer Assisted Instruction". Dissertation
for the degree of Doctor of Education, North Carolina State University.[1]
de Boer, V.. "Optimal Learning and the Spacing Effect: Theory, Application and Experiments
based on the Memory Chain Model". Artificial Intelligence Master's Thesis for Computational
Psychology, University of Amsterdam.[2] Dempster, F. N.. "The Spacing Effect: A Case
Study in the Failure to Apply the Results of Psychological Research". American Psychologist,
43(8), 627-634. Greene R. L.. Repetition and spacing effects.
In Roediger H. L. III, Learning and memory: A comprehensive reference. Vol. 2: Cognitive
psychology of memory. Oxford: Elsevier. Karpicke, J. D., & Roediger, H. L.. "Expanding
Retrieval Practice Promotes Short-Term Retention, but Equally Spaced Retrieval Enhances Long-Term
Retention". Journal of Experimental Psychology: Learning, * Memory, and Cognition, 33(4),
704-719.[3] Kerfoot, B. P.; Baker, H. E.; Koch, M. O.;
Connelly, D.; Joseph, D. B.; Ritchey, M. L.. "Randomized, Controlled Trial of Spaced Education
to Urology Residents in the United States and Canada". The Journal of Urology 177: 1481–1487.
doi:10.1016/j.juro.2006.11.074. PMID 17382760. Pavlik, P. I.. The Microeconomics of Learning:
Optimizing Paired-Associate Memory. PhD, Carnegie Mellon.
Pavlik, P. I.; Anderson, J. R.. "Using a model to compute the optimal schedule of practice".
Journal of Experimental Psychology 14: 101–117. doi:10.1037/1076-898X.14.2.101. PMID 18590367.
Dr Piotr Wozniak. "Effective learning: Twenty rules of formulating knowledge". — software-neutral
advice on making flashcards for spaced repetition. References