Concept
Spaced Repetition
4 studies
Spaced repetition distributes repeated learning opportunities over time instead of concentrating them into one session. The spacing interval is the gap between learning opportunities; the retention interval is the gap from the last opportunity to the test. These are different variables, and a useful schedule depends on what is learned and when it needs to be recalled.
The studies here cover delayed vocabulary recall, novice ECG interpretation, and medical-school examinations. They support a case for distributing learning while leaving the exact schedule, causal strength, and transfer to other outcomes open.
Does spaced repetition improve long-term recall?
Start with the findings and their cited studies, then compare the boundaries below.
Distributed sessions helped vocabulary recall here, with a selection caveat.
The spacing finding extends to a complex learning task, but not without design limits.
Before applying these findings
Separate practice spacing from the delay before testing. Check randomisation and attrition, and avoid treating a task-specific timing result as validation of a flashcard algorithm.
A tension to inspect
The studies use different intervals, materials and tests: word-pair recall over days and weeks, novice diagnostic interpretation, and course-end exams. They do not yield one optimal spacing interval or one pooled gain.
Use the Claims tab to inspect each claim and its supporting, challenging, or qualifying studies.
Inspect source passages
Do spaced sessions and feedback improve vocabulary recall?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
What was the main finding?
In support of H1, participants in which learning was distributed the most (four sessions) had the highest recall performance (M = 77.2, SD = 29).
What is the main limit on applying this result?
The levels of the variable Spacing (one, two, or four sessions) were equally distributed among the experimenters, but the participant allocation to the levels was not done entirely at random: the rigid scheduling of several sessions would have made it impossible for some to participate.
Inspect source passages
Can blocked practice outperform interleaving for novice ECG learners?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Who participated and how large was the analysed sample?
A further 19 students did not complete the delayed retention test.
What was the main finding?
The mean percent correct on the final test for blocked practice was 34% (95% CI 27–40%) and for interleaved practice 24% (95% CI 18–29%).
This is a selected set of studies, not an exhaustive literature review. A watch follows covered updates in PaperFren.
Studies
4
Findings
4
4 supporting · 0 challenging · 0 qualifying citations
Open tensions
1
Currently
What we know
- Distributed sessions helped vocabulary recall here, with a selection caveat.
- The spacing finding extends to a complex learning task, but not without design limits.
- A favourable interval in one experiment is not a universal review schedule.
- An app-use association cannot certify the app or its algorithm.
Largest unresolved question
The studies use different intervals, materials and tests: word-pair recall over days and weeks, novice diagnostic interpretation, and course-end exams. They do not yield one optimal spacing interval or one pooled gain.
Common misconceptions
The best spacing interval is always 12 hours.
The nominal 12-hour result came from one design, with variable timing and substantial four-week attrition. It is not a universal prescription.
Anki users scored higher, so the app caused their improvement.
Non-random use and other study differences remain plausible explanations despite MCAT adjustment.
Related
Claim ledger
What the evidence shows
Drawn from 4 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
Distributed sessions helped vocabulary recall here, with a selection caveat.
In a vocabulary web experiment, four spaced sessions produced higher delayed recall than one massed session with the same total study time. Spacing allocation was partly non-random, and initial performance differences weaken a pure causal interpretation.
The spacing finding extends to a complex learning task, but not without design limits.
Novice ECG learners scored higher after instruction distributed over consecutive weeks than after one massed session on a delayed test, but attrition, schedule switches and unequal delays limit the comparison.
A favourable interval in one experiment is not a universal review schedule.
In the vocabulary and visual-acuity experiment, the nominal 12-hour spacing group showed favourable longer-delay performance, but its actual mean gap was about 16 hours. The smaller four-week vocabulary analysis did not show a significant main spacing effect.
An app-use association cannot certify the app or its algorithm.
Anki users had higher medical-school exam scores after adjustment for MCAT, but use was self-selected. This association does not isolate spacing from retrieval, motivation, other resources, or time studying.
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
The studies use different intervals, materials and tests: word-pair recall over days and weeks, novice diagnostic interpretation, and course-end exams. They do not yield one optimal spacing interval or one pooled gain.
The studies use different intervals, materials and tests: word-pair recall over days and weeks, novice diagnostic interpretation, and course-end exams. They do not yield one optimal spacing interval or one pooled gain.
- Do spaced sessions and feedback improve vocabulary recall?
- Is there one best interval between study sessions?
- Can blocked practice outperform interleaving for novice ECG learners?
- Are Anki flashcards associated with higher medical-school exam scores?
Study Role Design N Population Outcome Do spaced sessions and feedback improve vocabulary recall? Supports Human experimentMixed factorial experiment; spacing allocation partly constrained by scheduling N=79 · 87 recruited; 79 analysed Native or advanced German speakers, ages 16–77, without prior Finnish knowledge Delayed cued recall of Finnish–German translations Is there one best interval between study sessions? Supports Human experimentRandom assignment to six spacing groups; repeated retention tests N=107 · 120 recruited; 107 in vocabulary analysis of first two final tests; 48 with all three tests Healthy university-area volunteers; vocabulary sample mean age about 23 years Cued vocabulary recall and visual-acuity performance across retention tests Can blocked practice outperform interleaving for novice ECG learners? Supports Human experiment2×2 factorial intervention; initially random allocation with four schedule switches N=51 · 80 enrolled; 70 completed all modules; 51 completed delayed test First-year medical students at McMaster University without prior ECG training Immediate module quizzes and delayed cumulative ECG interpretation quiz Are Anki flashcards associated with higher medical-school exam scores? Supports CohortNon-randomised cohort comparison; MCAT-adjusted exam-score analyses N=130 · 78 ever-users and 52 never-users; exam-specific Anki samples 48, 39, 23 and 10 First-year medical students at Boonshoft School of Medicine, class of 2025 Three course-end examinations and an end-of-year basic-science assessment
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
Concept page published
Spaced Repetition
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Coverage edits are distinct from reviewed research changes and corrections. Dates record PaperFren updates; study publication dates appear in the timeline.
- Coverage updated · Concept page published
Papers
4 studies in this library bear on Spaced Repetition, ordered by citations.
- Are Anki flashcards associated with higher medical-school exam scores?
Anki users had higher examination scores in one medical-school cohort after adjustment for MCAT scores, but self-selection prevents a causal conclusion.
- Can blocked practice outperform interleaving for novice ECG learners?
Novice medical students did better after distributed instruction, while blocked practice outperformed interleaving on a delayed ECG interpretation test.
- Is there one best interval between study sessions?
Vocabulary and visual-acuity practice showed different retention across spacing intervals, with the nominal 12-hour group doing well; the study does not establish a universal optimal schedule.
- Do spaced sessions and feedback improve vocabulary recall?
German-speaking learners recalled more Finnish vocabulary after distributed sessions, while retrieval trials benefited from corrective feedback; spacing groups were not fully randomised.
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Select 2–10 studies. Design and N are labels, not a ranking.
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Questions
What is still open
The studies use different intervals, materials and tests: word-pair recall over days and weeks, novice diagnostic interpretation, and course-end exams. They do not yield one optimal spacing interval or one pooled gain.
Ask PaperFren about Spaced Repetition
Study this conceptflashcards and short-answer questions
Does spaced repetition improve long-term recall?
The selected experiments support better delayed recall with distributed learning, particularly for vocabulary. Follow-up length and design matter: one study tested after roughly two to three days; another included one-, seven- and 28-day tests but had substantial four-week attrition. These results do not guarantee gains for every subject or app.
What spacing interval best supports retention?
There is no universal best interval established by this set. The nominal 12-hour condition performed favourably in one experiment, but actual timing varied and the four-week sample was small. Compare the material, number of repetitions and desired retention delay before applying a schedule.
Flashcards
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