Spaced repetition

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In the Leitner system, correctly answered cards are advanced to the next, less frequent box, while incorrectly answered cards return to the first box for more aggressive review and repetition. Leitner system alternative.svg
In the Leitner system, correctly answered cards are advanced to the next, less frequent box, while incorrectly answered cards return to the first box for more aggressive review and repetition.

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 proven to increase the rate of learning. [1]

Contents

Spaced repetition with forgetting curves ForgettingCurve.svg
Spaced repetition with forgetting curves

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. [2] A number of spaced repetition software programs have been developed to aid the learning process. It is also possible to perform spaced repetition with physical flashcards using the Leitner system. The testing effect and spaced repetition can be combined to improve long-term memory. Therefore, memorization can be easier to do.

History

The method of spaced repetition was first conceived of in the 1880s by German scientist Hermann Ebbinghaus. Ebbinghaus created the 'forgetting curve' - a graph portraying the loss of learned information over time - and postulated that it can be curbed by reviewing such information at several intervals over a period of time. [3]

It was also tested by Landauer and Bjork in 1978; they gathered a group of psychology students, showing the students pictures of a certain individual followed by that individual's name. This is also known as a face-name association. With the repetition of seeing the person's name and face they were able to associate the name and face of that individual shown with the expansion of time due to the spaced repetition. [4]

Schacter, Rich, and Stampp in 1985 expanded the research to include people who have amnesia and other memory disorders. The findings showed that using spaced repetition can not only help students with name face association but patients dealing with memory impairments. [5]

In 1989, C. J. Camp decided that using this technique with Alzheimer's patients may increase their duration of remembering particular things. [4] These results show that the expansion of the time interval shows the strongest benefits for memory. [5]

Spaced repetition is a method where the subject is asked to remember a certain fact with the time intervals increasing each time the fact is presented or said. If the subject is able to recall the information correctly the time is doubled to further help them keep the information fresh in their mind to recall in the future. With this method, the patient is able to place the information in their long-term memory. If they are unable to remember the information they go back to the previous step and continue to practice to help make the technique lasting (Vance & Farr, 2007).[ full citation needed ]

The expansion is done to ensure a high success level of recalling the information on the first time and increasing the time interval to make the information long-lasting to help keep the information always accessible in their mind. [6] Throughout the development of spaced repetition, they have found that patients using this technique with dementia are able to recall the information weeks—even months—later. The technique has been successful in helping dementia patients remember particular objects' names, daily tasks, name face association, information about themselves, and many other facts and behaviors (Small, 2012). [7] Sufficient test evidence shows that spaced repetition is valuable in learning new information and recalling information from the past. [5]

Small combines the works and findings of quite a few scientists to come up with five reasons why spaced repetition works: it helps show the relationship of routine memories, it shows the benefits of learning things with an expansion of time, it helps the patient with Alzheimer's dementia keep their brain active, it has a high success level with little to no errors, and the technique is meaningful for the patient to do and remember more thing) [7] Joltin et al. (2003),[ full citation needed ] had a caregiver train a woman with Alzheimer's by giving her the name of her grandchild over the phone while asking her to associate with the picture of the grandchild posted on the refrigerator. After training, the woman was able to recall the name of her grandchild five days later. [5]

Research and application

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." [8]

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. [9] 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 [10] and Landauer and Bjork, [11] 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 (see § Software), 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.

The data behind this initial research indicated that an increasing space between rehearsals (expanding) would yield a greater percentage of accuracy at test points. [12] Spaced repetition with expanding intervals is believed to be so effective because with each expanded interval of repetition it becomes more difficult to retrieve the information because of the time elapsed between test periods; this creates a deeper level of processing of the learned information in long-term memory at each point. Another reason that the expanding repetition model is believed to work so effectively is that the first test happens early on in the rehearsal process. [13] The purpose of this is to increase repetition success. By having a first test that followed initial learning with a successful repetition, people are more likely to remember this successful repetition on the following tests. [14] Although expanding retrieval is commonly associated with spaced repetition, a uniform retrieval schedule is also a form of spaced repetition procedure. [13]

Spaced repetition is typically studied through the use of memorizing facts. Traditionally speaking, it has not been applied to fields that required some manipulation or thought beyond simple factual/semantic information. A more recent study has shown that spaced repetition can benefit tasks such as solving math problems. In a study conducted by Pashler, Rohrer, Cepeda, and Carpenter, [15] participants had to learn a simple math principle in either a spaced or massed retrieval schedule. The participants given the spaced repetition learning tasks showed higher scores on a final test distributed after their final practice session. [15]

This is unique in the sense that it shows spaced repetition can be used to not only remember simple facts or contextual data but it can also be used in fields, such as math, where manipulation and the use of particular principles or formulas (e.g. y = mx + b) is necessary. These researchers also found that it is beneficial for feedback to be applied when administering the tests. When a participant gave a wrong response, they were likely to get it correct on the following tests if the researcher gave them the correct answer after a delayed period. Spaced repetition is a useful tool for learning that is relevant to many domains such as fact learning or mathematics, and many different tasks (expanding or uniform retrieval). [15] Many studies over the years have contributed to the use and implementation of spaced repetition, and it still remains a subject of interest for many researchers. [16]

Over the years, techniques and tests have been formed to better patients with memory difficulties. Spaced repetition is one of these solutions to help better the patients' minds. Spaced repetition is used in many different areas of memory from remembering facts to remembering how to ride a bike to remembering past events from childhood. [4] Recovery practice is used to see if an individual is able to recall something immediately after they have seen or studied it. Increasing recovery practice is frequently used as a technique in improving long-term memory, essentially for young children trying to learn and older individuals with memory diseases. [6]

Algorithms

There are several families of algorithms for scheduling spaced repetition:

Some have theorized that the precise length of intervals does not have a great impact on algorithm effectiveness, [22] although it has been suggested by others that the interval (expanded interval vs. fixed interval, etc.) is quite important. The experimental results regarding this point are mixed. [23]

Implementations

Software

Anki being used for memorizing Russian vocabulary Anki 2.0.22 KDE4.en.story-ru-en.smallwindow.png
Anki being used for memorizing Russian vocabulary

Most spaced repetition software (SRS) is 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 a 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. [24]

Further refinements with regard to software:

Paper flash cards

Animation of three sessions Leitner system animation.gif
Animation of three sessions

The Leitner system is a widely used method of efficiently using flashcards that was proposed by the German science journalist Sebastian Leitner in the 1970s. It is a simple implementation of the principle of spaced repetition, where cards are reviewed at increasing intervals.

In this method, flashcards are sorted into groups according to how well the learner knows each one in Leitner's learning box. The learners try to recall the solution written on a flashcard. If they succeed, they send the card to the next group. If they fail, they send it back to the first group. Each succeeding group has a longer period of time before the learner is required to revisit the cards. In Leitner's original method, published in his book So lernt man Lernen (How To Learn To Learn), the schedule of repetition was governed by the size of the partitions in the learning box. These were 1, 2, 5, 8 and 14 cm. Only when a partition became full was the learner to review some of the cards it contained, moving them forward or back, depending on whether they remembered them.

Audio instruction

Graduated-interval recall is a type of spaced repetition published by Paul Pimsleur in 1967. [27] 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.

Criticism

Spaced repetition with expanding intervals has long been argued to be the most beneficial version of this learning procedure, but research, which compared repetition procedures, has shown the difference between expanding repetition and uniform retrieval is either very little to nonexistent. A paper authored by John L Dobson has found cases where uniform retrieval is better than expanding. [28] The main speculation for this range of results is that prior research has not accounted for the possibility of their results being affected by either the spacing condition or the number of successful repetitions during study periods. [13]

There are two forms of implementing spacing in spaced repetition. The first form is absolute spacing. Absolute spacing is the measurement of all the trials within the learning and testing periods. An example of this would be that participants would study for a total of thirty trial periods, but the spacing of these trials can either be expanding or uniform. The second form is called relative spacing. Relative spacing measures the spacing of trials between each test. An example of this would be if the absolute spacing was thirty, participants would either have expanding intervals (1–5–10–14) or uniform intervals (5–5–5–5–5–5). This is important in measuring whether or not one type of repetition schedule is more beneficial than the other. [13]

A common criticism of repetition research has argued that many of the tests involved have simply measured retention on a short-term scale. A study conducted by Karpicke and Bauernschmidt [13] used this principle to determine the major differences between the different types of repetition. The two focused on studying long-term retention by testing participants over the course of one week. The participants were either assigned to a uniform schedule or an expanding schedule. No matter what type of spacing was assigned to the ninety-six participants, each completed three repeated tests at the end of their rehearsal intervals. Once those tests were completed, participants came back one week later to complete a final retention test. The researchers concluded that it did not matter what kind of repetition schedule was used. The biggest contribution to effective long-term learning was the spacing between the repeated tests (absolute spacing). [13]

Related Research Articles

<span class="mw-page-title-main">Forgetting curve</span> Decline of memory retention in time

The forgetting curve hypothesizes the decline of memory retention in time. This curve shows how information is lost over time when there is no attempt to retain it. A related concept is the strength of memory that refers to the durability that memory traces in the brain. The stronger the memory, the longer period of time that a person is able to recall it. A typical graph of the forgetting curve purports to show that humans tend to halve their memory of newly learned knowledge in a matter of days or weeks unless they consciously review the learned material.

<span class="mw-page-title-main">Incremental reading</span> Software-assisted learning technique

Incremental reading is a software-assisted method for learning and retaining information from reading, which involves the creation of flashcards out of electronic articles. "Incremental reading" means "reading in portions". Instead of a linear reading of articles one at a time, the method works by keeping a large list of electronic articles or books and reading parts of several articles in each session. The user prioritizes articles in the reading list. During reading, key points of articles are broken up into flashcards, which are then learned and reviewed over an extended period with the help of a spaced repetition algorithm.

<span class="mw-page-title-main">SuperMemo</span> Spaced repetition memorization/learning software

SuperMemo is a learning method and software package developed by SuperMemo World and SuperMemo R&D with Piotr Woźniak in Poland from 1985 to the present. It is based on research into long-term memory, and is a practical application of the spaced repetition learning method that has been proposed for efficient instruction by a number of psychologists as early as in the 1930s.

Recall in memory refers to the mental process of retrieval of information from the past. Along with encoding and storage, it is one of the three core processes of memory. There are three main types of recall: free recall, cued recall and serial recall. Psychologists test these forms of recall as a way to study the memory processes of humans and animals. Two main theories of the process of recall are the two-stage theory and the theory of encoding specificity.

Memorization is the process of committing something to memory. It is a mental process undertaken in order to store in memory for later recall visual, auditory, or tactical information.

<span class="mw-page-title-main">Flashcard</span> Tool for systematic learning

A flashcard or flash card is a card bearing information on both sides, which is intended to be used as an aid in memorization. Each flashcard typically bears a question or definition on one side and an answer or target term on the other. Flashcards are often used to memorize vocabulary, historical dates, formulae or any subject matter that can be learned via a question-and-answer format. Flashcards can be virtual, or physical.

The interference theory is a theory regarding human memory. Interference occurs in learning. The notion is that memories encoded in long-term memory (LTM) are forgotten and cannot be retrieved into short-term memory (STM) because either memory could interfere with the other. There is an immense number of encoded memories within the storage of LTM. The challenge for memory retrieval is recalling the specific memory and working in the temporary workspace provided in STM. Retaining information regarding the relevant time of encoding memories into LTM influences interference strength. There are two types of interference effects: proactive and retroactive interference.

The spacing effect demonstrates that learning is more effective when study sessions are spaced out. This effect shows that more information is encoded into long-term memory by spaced study sessions, also known as spaced repetition or spaced presentation, than by massed presentation ("cramming").

<span class="mw-page-title-main">Testing effect</span> Memory effect in educational psychology

The testing effect suggests long-term memory is increased when part of the learning period is devoted to retrieving information from memory. It is different from the more general practice effect, defined in the APA Dictionary of Psychology as "any change or improvement that results from practice or repetition of task items or activities."

Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst. The term was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that recall accuracy varies as a function of an item's position within a study list. When asked to recall a list of items in any order, people tend to begin recall with the end of the list, recalling those items best. Among earlier list items, the first few items are recalled more frequently than the middle items.

<span class="mw-page-title-main">Study skills</span> Approaches applied to learning

Study skills or study strategies are approaches applied to learning. Study skills are an array of skills which tackle the process of organizing and taking in new information, retaining information, or dealing with assessments. They are discrete techniques that can be learned, usually in a short time, and applied to all or most fields of study. More broadly, any skill which boosts a person's ability to study, retain and recall information which assists in and passing exams can be termed a study skill, and this could include time management and motivational techniques.

Memory has the ability to encode, store and recall information. Memories give an organism the capability to learn and adapt from previous experiences as well as build relationships. Encoding allows a perceived item of use or interest to be converted into a construct that can be stored within the brain and recalled later from long-term memory. Working memory stores information for immediate use or manipulation, which is aided through hooking onto previously archived items already present in the long-term memory of an individual.

Studying in an educational context refers to the process of gaining mastery of a certain area of information. Study software then is any program which allows students to improve the time they spend thinking about, learning and studying that information.

<span class="mw-page-title-main">Mnemosyne (software)</span>

Mnemosyne is a line of spaced repetition software developed since 2003. Spaced repetition is an evidence-based learning technique that has been shown to increase the rate of memorization.

<span class="mw-page-title-main">Anki (software)</span> Spaced repetition software

Anki is a free and open-source flashcard program. It uses techniques from cognitive science such as active recall testing and spaced repetition to aid the user in memorization. The name comes from the Japanese word for "memorization".

<span class="mw-page-title-main">Memory improvement</span> Act of improving ones memory

Memory improvement is the act of enhancing one's memory. Research on improving memory is driven by amnesia, age-related memory loss, and people’s desire to enhance their memory. Research involved in memory improvement has also worked to determine what factors influence memory and cognition. There are many different techniques to improve memory some of which include cognitive training, psychopharmacology, diet, stress management, and exercise. Each technique can improve memory in different ways.

Memory gaps and errors refer to the incorrect recall, or complete loss, of information in the memory system for a specific detail and/or event. Memory errors may include remembering events that never occurred, or remembering them differently from the way they actually happened. These errors or gaps can occur due to a number of different reasons, including the emotional involvement in the situation, expectations and environmental changes. As the retention interval between encoding and retrieval of the memory lengthens, there is an increase in both the amount that is forgotten, and the likelihood of a memory error occurring.

Distributed practice is a learning strategy, where practice is broken up into a number of short sessions over a longer period of time. Humans and other animals learn items in a list more effectively when they are studied in several sessions spread out over a long period of time, rather than studied repeatedly in a short period of time, a phenomenon called the spacing effect. The opposite, massed practice, consists of fewer, longer training sessions and is generally a less effective method of learning. For example, when studying for an exam, dispersing your studying more frequently over a larger period of time will result in more effective learning than intense study the night before.

Elaborative encoding is a mnemonic system which uses some form of elaboration, such as an emotional cue, to assist in the retention of memories and knowledge. In this system one attaches an additional piece of information to a memory task which makes it easier to recall. For instance, one may recognize a face easier if character traits are also imparted about the person at the same time.

A desirable difficulty is a learning task that requires a considerable but desirable amount of effort, thereby improving long-term performance. It is also described as a learning level achieved through a sequence of learning tasks and feedback that lead to enhanced learning and transfer.

References

  1. ↑ 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.
  2. ↑ "Learn Languages with Spaced Repetition & Anki Flashcards". Adros Verse Education. Retrieved February 5, 2024.
  3. ↑ EditorialTeam. "Why We Can't Remember What We Learn and What To Do About It". Wharton Interactive. Wharton. Retrieved December 3, 2023.
  4. 1 2 3 Oren, Shiri; Willerton, Charlene; Small, Jeff (February 2014). "Effects of Spaced Retrieval Training on Semantic Memory in Alzheimer's Disease: A Systematic Review". Journal of Speech, Language, and Hearing Research. 57 (1): 247–270. doi:10.1044/1092-4388(2013/12-0352). ISSN   1092-4388. PMID   24023380.
  5. 1 2 3 4 Hawley, K. S., Cherry, K. E., Boudreaux, E. O., & Jackson, E. M. (2008). A comparison of adjusted spaced repetition versus a uniform expanded repetition schedule for learning a name-face association in older adults with probable Alzheimer's disease. Journal of Clinical & Experimental Neuropsychology, 30(6), 639–649. doi : 10.1080/13803390701595495.
  6. 1 2 Karpicke, J. D., & Roediger, H. (2007). Expanding repetition practice promotes short-term retention, but equally spaced repetition enhances long-term retention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(4), 704–719. doi : 10.1037/0278-7393.33.4.704.
  7. 1 2 Small, Jeff A. (June 2012). "A new frontier in spaced retrieval memory training for persons with Alzheimer's disease". Neuropsychological Rehabilitation. 22 (3): 329–361. doi:10.1080/09602011.2011.640468. PMID   22272562. S2CID   13147220.
  8. ↑ Mace, C. A. (1932). Psychology of Study. p. 39.
  9. ↑ Spitzer, H. F. (1939). "Studies in retention". Journal of Educational Psychology. 30 (9): 641–657. doi:10.1037/h0063404.
  10. ↑ Melton, A. W. (1970). "The situation with respect to the spacing of repetitions and memory". Journal of Verbal Learning and Verbal Behavior. 9 (5): 596–606. doi:10.1016/S0022-5371(70)80107-4. hdl: 2027.42/32694 .
  11. ↑ Landauer, T. K.; Bjork, R. A. (1978). "Optimum rehearsal patterns and name learning". In Gruneberg, M.; Morris, P. E.; Sykes, R. N. (eds.). Practical aspects of memory. Academic Press. pp. 625–632. ISBN   0123050502.
  12. ↑ Landauer, T., & Bjork, R. (1978). Optimum rehearsal patterns and name learning. Practical Aspects of Memory, 625–632. Retrieved October 15, 2014. "Archived copy" (PDF). Archived from the original (PDF) on February 11, 2015. Retrieved December 10, 2014.{{cite web}}: CS1 maint: archived copy as title (link)
  13. 1 2 3 4 5 6 Karpicke, Jeffrey D.; Bauernschmidt, Althea (2011). "Spaced retrieval: absolute spacing enhances learning regardless of relative spacing". Journal of Experimental Psychology: Learning, Memory, and Cognition. 37 (5): 1250–1257. doi:10.1037/a0023436. PMID   21574747. S2CID   16580641.
  14. ↑ Karpicke, J., & Roediger, H. (2010). Is expanding retrieval a superior method for learning text materials? Memory & Cognition, 38(1), 116–124. doi : 10.3758/MC.38.1.116.
  15. 1 2 3 Pashler, H., Rohrer, D., Cepeda, N., & Carpenter, S. (2007). Enhancing learning and retarding forgetting: Choices and consequences. Psychonomic Bulletin & Review, 14(2), 187–193.
  16. ↑ Brush, J., & Camp, C. (2008). Using Spaced Retrieval as an Intervention During Speech-Language Therapy. Clinical Gerontologist, 19(1), 51–64.
  17. ↑ "Implementing a neural network for repetition spacing". www.supermemo.com. Archived from the original on August 21, 2022. Retrieved July 15, 2017.
  18. ↑ Ye, Junyao (November 6, 2023). "fsrs4anki". GitHub . Archived from the original on June 19, 2023. Retrieved November 14, 2023.
  19. ↑ Damien, Elmes (October 31, 2023). "Anki Release 23.10". GitHub . Archived from the original on November 3, 2023. Retrieved November 14, 2023.
  20. ↑ Ye, Junyao (November 13, 2023). "Spaced Repetition Algorithm: A Three-Day Journey from Novice to Expert". GitHub . Archived from the original on November 13, 2023. Retrieved November 14, 2023.
  21. ↑ Ye, Junyao; Su, Jingyong; Cao, Yilong (August 14, 2022). "A Stochastic Shortest Path Algorithm for Optimizing Spaced Repetition Scheduling". Proceedings of the 28th ACM SIGKDD Conference on Knowledge Discovery and Data Mining. KDD '22. New York, NY, USA: Association for Computing Machinery. pp. 4381–4390. doi:10.1145/3534678.3539081. ISBN   978-1-4503-9385-0. S2CID   251518206.
  22. ↑ Cull, W. L. (2000). "Untangling the benefits of multiple study opportunities and repeated testing for cued recall". Applied Cognitive Psychology. 14 (3): 215–235. doi:10.1002/(SICI)1099-0720(200005/06)14:3<215::AID-ACP640>3.0.CO;2-1.
  23. ↑ Balota, David A.; Duchek, Janet M.; Logan, Jessica M. (2011). "6. Is Expanded Retrieval Practice a Superior Form of Spaced Retrieval? A Critical Review of the Extant Literature" (PDF). In Nairne, James S. (ed.). The Foundations of Remembering: Essays in Honor of Henry L. Roediger, III. Psychology Press. pp. 83–106. ISBN   978-1-136-87221-1.
  24. ↑ Gupta, James (January 23, 2016). "Spaced repetition: a hack to make your brain store information". The Guardian. ISSN   0261-3077 . Retrieved January 30, 2019.
  25. ↑ Cohen, Andrew S. (May 12, 2015) [2010]. "Confidence-Based Repetition (CBR)". Brainscape.com. Archived from the original on November 29, 2020.
  26. ↑ Cohen, Andrew S. (July 15, 2008). "Brainscape's 'Confidence-Based Repetition' Methodology" (PDF). Brainscape.com. Archived from the original (PDF) on November 4, 2020.
  27. ↑ Pimsleur, Paul (February 1967). "A Memory Schedule". The Modern Language Journal. 51 (2). Blackwell Publishing: 73–75. doi:10.2307/321812. JSTOR   321812.
  28. ↑ https://www.researchgate.net/publication/221882038_Effect_of_uniform_versus_expanding_retrieval_practice_on_the_recall_of_physiology_information

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