Home · C11
C11 weakened
Spacing practice out over time and interleaving different problem types lead to better results on delayed closed-book tests than massed or blocked practice, within realistic classroom time, but a lasting advantage over a whole school year is not established: in a year-long randomised trial in 62 grade-5 maths classrooms in Nigeria, mixing problems from earlier lessons into daily practice raised end-of-term tests, taken about a month after the material was taught, by about 0.28 standard deviations, yet left a cumulative end-of-year test essentially unchanged (0.03 standard deviations, not significant; gains concentrated among lower achievers, possible losses for the highest achievers; a working paper, not yet peer reviewed) (Kremer et al. 2026). Nor is a spacing advantage shown for practising a maths procedure: in a preregistered experiment, 235 university students who practised permutation problems on a computer in two sessions 1 or 11 days apart did no better one or five weeks later than students who did the same practice in one session (Ebersbach & Barzagar Nazari 2020).
- Status
- weakened
- Last change
- 2026-11-03
- Serves
- Q1 (How do humans actually learn, and what helps them learn best?)
- Ages
- overgripande (the project's evidence is reviews and meta-analyses spanning school, university and adult learners), grundskola-lag (one year-long randomised classroom trial in grade 5, Nigeria, Kremer et al. 2026), vuxen-livslangt (university students, Ebersbach & Barzagar Nazari 2020)
- Area
- Memory and practice
- Relates to
- C11 relates-to C0 (C0 is retrieval versus restudy; C11 is about when practice happens and how problem types are mixed, not about retrieval. Thematic, not a dependency). C11 relates-to C2 (both concern practice that feels harder but may work better later; tools that make practice feel easy can remove that difficulty. Thematic).
- Bounds
- This claim is about spacing (spreading practice over time instead of massing it in one session) and interleaving (mixing problem types instead of practising one type at a time), not about retrieval practice versus rereading (that is C0). Evidence in the project: Cepeda et al. 2006 (review of distributed practice); Dunlosky et al. 2013 (review of learning techniques); Brunmair & Richter 2019 (interleaving meta-analysis: interleaving helps overall, but blocking was better for words, and the effect depends on how similar the categories are); Weinstein, Madan & Sumeracki 2018 (review); Bjork, Dunlosky & Kornell 2013 (learners misjudge which practice works, so these techniques may need to be imposed rather than chosen). The comparison in realistic classroom time has not yet been checked study by study in this project. Durability bound (added 2026-10-15, nightly attack): Kremer, Gray-Lobe, de Laat & van der Haar 2026 (NBER Working Paper 31853, revised February 2026; working paper, not peer reviewed; full text read): 62 Bridge Nigeria schools randomised (one grade-5 classroom each, 687 students) to interleaved or blocked maths practice for a full school year, same number of problems, scripted lessons; interleaved sets mixed the topic of the day with problems from earlier lessons in the term (so spacing changed too). End-of-term posttests (material taught on average 29–39 days earlier): +0.28 SD; cumulative end-of-year test (material taught on average about 145 days earlier): +0.03 SD (95 % CI −0.28 to 0.34), significantly smaller than the posttest effect (p = 0.02); larger gains for lower achievers (+0.54 SD on posttests one SD below the mean), possible harm for the highest achievers (−0.33 SD at the 90th percentile on the cumulative test). The authors call the year-end result inconclusive (moderate effects either way cannot be ruled out) and note that frequent tests gave both arms spaced, mixed practice. So the advantage is shown at about a month in that classroom trial, not over a whole year. Procedural-skill bound (added 2026-10-16, extra run 4): Ebersbach & Barzagar Nazari 2020 (Frontiers in Psychology 11, 811; preregistered on OSF): 3 (gap between two practice sets: none, 1 day, 11 days) × 2 (test after 1 or 5 weeks) between-subjects, 235 university students (38–40 per cell), computer tutorial and practice on permutation tasks taken from Rohrer & Taylor (2007), same amount of practice; robust regression: spaced vs massed B = −0.02 (SE 0.18, p = .91), 11 vs 1 day B = 0.26 (p = .10), no interaction with test delay; only the longer delay lowered scores (5 weeks M = 1.63 vs 1 week M = 2.53). Not a classroom study; one procedure; the authors suggest spacing works less reliably for procedural than declarative knowledge. Contrasts with Rohrer & Taylor 2006, who found a spacing benefit on similar permutation tasks after four weeks (as summarised by Ebersbach & Barzagar Nazari). Kill-condition test survived 2026-10-17: Murray, Horner & Göbel 2025 (Educational Psychology Review 37, 75; preregistered meta-analysis; full text read in the accepted manuscript): in 17 course-embedded mathematics studies (26 effect sizes; exams two days to five weeks after the last practice), spaced practice beat massed practice by g = 0.24 (95% CI 0.155 to 0.324). All US, mostly university, nearly half the effects from theses or a conference paper; spacing and interleaving are mixed together in these course designs. Kill-condition test survived 2026-11-03 (nightly attack): Ruitenburg, Goos, Lambert, Kirschner, Jarodzka & Camp 2026 (Educational Psychology Review 38, 137, DOI 10.1007/s10648-026-10225-5; open access, full text read): three-level meta-analysis of experiments in authentic primary and secondary classrooms (typically developing pupils aged 6–18, curricular content, active comparison condition, practice and test in school, basic quality criteria; published 2006–2024). Distributed practice g = 0.20 (95% CI 0.03–0.36; 15 studies, 56 effect sizes, 2,010 pupils): against massed practice g = 0.39, against less-distributed practice not significant; retention interval 1 day–1 week g = 0.21 (p = .06), over 1 week g = 0.24; significant only when the gap between sessions was 10–100% of the retention interval (g = 0.31). Interleaved versus blocked g = 0.40 (95% CI 0.10–0.71; 10 studies, 57 effect sizes, 1,902 pupils): significant with no feedback (g = 0.25) or delayed feedback (g = 0.82, 5 effect sizes) but not with immediate feedback during practice (p = .75); the authors call their explanation conjecture. No sign of publication bias (Egger). Few interleaving studies, mostly procedural maths; sparse moderator cells.
- What would kill this
- A meta-analysis or large classroom trial in which massed or blocked practice matches or beats spacing and interleaving on a delayed closed-book test, within realistic classroom time. Narrowed on promotion from the bank's “lose to” to “matches or beats”, and the retrieval part dropped (it is C0) (approved by Jonatan 2026-10-14). Bank wording (Swedish, verbatim): “Meta där retrieval/spacing/interleaving förlorar mot reread/massed under ekologisk klassrumstid med delayed closed-book.”
- Tutor consequence
- none yet
Attack record
4 attacks: 2 survived, 2 narrowed
2026-10-15 narrowed
- Attack
- In a year-long randomised trial in 62 Nigerian grade-5 maths classrooms, interleaved practice (about half of each day's practice problems drawn from earlier lessons in the term) raised end-of-term posttests by 0.28 SD over blocked practice with the same number of problems, but its effect on a cumulative end-of-year test covering the same material was 0.03 SD (95 % CI −0.28 to 0.34), significantly smaller than the posttest effect, so blocked practice matched interleaving on that delayed closed-book test within realistic classroom time and C11's kill-condition is met for the year-long horizon.
- Target
- kill-condition
- Source
- Kremer, Gray-Lobe, de Laat & van der Haar 2026 (preprint) | NBER Working Paper 31853, DOI 10.3386/w31853
- Steelmans to
- C11 dies on "a meta-analysis or large classroom trial in which massed or blocked practice matches or beats spacing and interleaving on a delayed closed-book test, within realistic classroom time"; this is the first experimental evaluation of interleaving run over a full academic year, school-randomised, practitioner-delivered through scripted lessons in ordinary classrooms, with the problem count held equal; on the cumulative test (content taught on average about 145 days earlier) interleaving gave 0.03 SD, nearly ten times smaller than the 0.24 SD predicted from the posttest gains (surrogate analysis), and quantile estimates suggest harm at the top of the distribution (−0.33 SD at the 90th percentile).
- Why
- Nightly-attacks 2026-10-15 Europe/Stockholm. Full text read (NBER PDF, revised February 2026; not stored). Design: 63 Bridge Nigeria schools, one excluded, 62 randomised (one grade-5 classroom each; 28 interleaved, 34 blocked; strata with one school dropped, one interleaved school had no eligible students); 687 incumbent students, mean age 9.81. Two 45-minute maths periods a day; same "my turn" worked examples in both arms; in interleaved classrooms the "your turn" problems mixed the topic of the day with problems from earlier lessons in the same term (roughly half each, mostly from the preceding three lessons or the current 3–5-lesson unit), so the program changes spacing as well as interleaving (the authors say effects cannot be attributed to interleaving alone). Tests: 30 open-ended items, graded by another teacher. Termly posttests (retention intervals on average 39, 38 and 29 days): +0.28 SD (Table 3, Panel B), similar across terms (largest 0.31 SD on the third). Cumulative test, five days after the program ended, items mirroring the three posttests, content introduced on average 145 days earlier: +0.03 SD (95 % CI −0.28 to 0.34); test of equal effects p = 0.02. Students one SD below the mean: posttests +0.54 SD; on the cumulative test the 20th-percentile effect was 0.49 SD but the 90th-percentile effect −0.33 SD (p < .05). Follow-up: 97 % for the posttest index; about 78 % in comparison schools for the cumulative test, 4 points lower in interleaved schools (ns). Kill withheld: (1) the same trial shows interleaving beating blocked practice on tests taken about a month after the material was taught, which is a delayed closed-book test within classroom time, so the claim survives at that horizon; (2) the cumulative estimate is imprecise and the authors call the study inconclusive on cumulative performance and say moderate positive or negative effects cannot be ruled out; (3) one setting (low-cost private schools with scripted lessons, frequent tests that themselves give spaced, mixed practice to both arms), one subject, one grade; (4) working paper. Context, as reported by the authors: the longest earlier interleaving program in maths ran four months in Florida and found 0.83 SD after one month (Rohrer et al. 2020); a two-day intervention gave 0.34 SD ten weeks later (Ziegler & Stern 2014). Not a restatement: C11's Bounds name Brunmair & Richter 2019 (blocking better for words; similarity of categories) and say the comparison in realistic classroom time had not been checked study by study; nothing on the claim limited the horizon. First ledger entry on C11. Claim, Bounds and Ages rewritten same turn; brief and the practical rule rewritten.
- Rewrite
- claim-field+brief
2026-10-16 narrowed
- Attack
- In a preregistered experiment with 235 university students, practising a maths procedure (permutation problems) in two sessions 1 or 11 days apart gave no better scores one or five weeks later than the same practice in one session (spaced vs massed B = −0.02, p = .91), so C11's claim that spacing beats massed practice on delayed closed-book tests does not hold for this kind of procedural practice.
- Target
- claim-text
- Source
- Ebersbach & Barzagar Nazari 2020 | DOI 10.3389/fpsyg.2020.00811
- Steelmans to
- C11 states spacing beats massed practice on delayed tests in general; a preregistered, adequately sized between-subjects test of exactly that contrast, with two delays (1 and 5 weeks) and the same tasks that once showed a spacing benefit (Rohrer & Taylor 2006/2007), found no spacing effect and no lag effect.
- Why
- Extra run 2026-10-16 (extra 4) Europe/Stockholm, ordered by Jonatan. Reached under the targeting rules after C9 (3e), C4 and C7 were fruitless. Full text read (open access, Europe PMC PMC7201105; not stored). Design: 3 (inter-study interval 0, 1, 11 days) × 2 (retention interval 1 or 5 weeks), all between-subjects, preregistered (OSF); 273 recruited, 235 analysed (38–40 per cell; mean age 24; paid); computer tutorial on permutations, two practice sets of four tasks, final test of procedural knowledge. Robust regression (1,000 bootstrap samples): spaced (1 or 11 days) vs massed B = −0.02 (SE 0.18, p = .909); 11 vs 1 day B = 0.26 (p = .103); RI × spacing interactions p = .078 and .633; longer delay lowered scores (B = −0.47, p = .001; 5 weeks M = 1.63, 1 week M = 2.53). Kill withheld: not a meta-analysis or classroom trial; university students working individually on a computer; one procedure; Rohrer & Taylor 2006 found spacing helped on the same kind of task after four weeks. Not a restatement: C11's existing bound is about durability over a school year (Kremer et al. 2026) and its Bounds mention item similarity for interleaving (Brunmair & Richter 2019); nothing limited the spacing half to declarative content. Not a preprint. Claim, Bounds and Ages rewritten same turn; brief and the practical rule Limits updated. Status unchanged (weakened).
- Rewrite
- claim-field+brief
2026-10-17 survived
- Attack
- A preregistered meta-analysis of spaced versus massed practice in mathematics would meet C11's kill-condition if, in the studies embedded in real courses with delayed exams, massed practice matched spacing.
- Target
- kill-condition
- Source
- Murray, Horner & Göbel 2025 | Educational Psychology Review 37(3), 75, DOI 10.1007/s10648-025-10035-1
- Steelmans to
- C11 dies on "a meta-analysis... in which massed or blocked practice matches or beats spacing... on a delayed closed-book test, within realistic classroom time"; this meta-analysis analyses course-embedded studies separately, the closest test of "realistic classroom time", and the year-long trial already on C11 (Kremer et al. 2026) shows the classroom advantage can fade, so a null was plausible.
- Why
- Nightly-attacks 2026-10-17 Europe/Stockholm. Full text read (accepted manuscript, White Rose Research Online; stored privately). Course-embedded studies: 17 studies, 26 effect sizes, g = 0.24 (SE 0.038; 95% CI 0.155 to 0.324); removing any single study left the lower limit above zero; trim-and-fill corrected g = 0.27 (0.215 to 0.326); time from last practice to exam two days to five weeks, five weeks most common. Isolated-learning studies g = 0.43 (10 studies, 27 effect sizes); all spacing studies g = 0.28 (27 studies, 53 effect sizes); the difference between the subsets was not significant (p = .095). Kill-condition failed. Limits: all course-embedded studies recruited in the USA, 65% of their effects come from universities, 46% from theses or a conference paper, and in 53% of effects learners could look back at their work during practice; course-embedded spacing also mixes topics, so spacing and interleaving are not separated, and studies that only compared blocked with interleaved practice were excluded; exam delays reach five weeks, so the year-end bound from Kremer et al. 2026 stands. Its retrieval-versus-restudy result in mathematics (7 studies, 32 effect sizes, g = 0.18, 95% CI crossing zero) bears on C0, not C11; noted as a lead. Not a preprint.
2026-11-03 survived
- Attack
- In authentic primary and secondary classrooms (not labs, not university courses), spacing and interleaving may give no reliable advantage over massed and blocked practice on delayed tests within realistic classroom time.
- Target
- kill-condition
- Source
- Ruitenburg, Goos, Lambert, Kirschner, Jarodzka & Camp 2026 | Educational Psychology Review 38, 137, DOI 10.1007/s10648-026-10225-5 (open access, CC BY; full text read on the publisher page)
- Steelmans to
- The strongest version: earlier meta-analyses mixed lab and university studies, and Donoghue & Hattie 2021 found smaller or even negative effects in schools; a meta-analysis restricted to real school classrooms with active comparisons and quality criteria is exactly the test the kill line names.
- Why
- Nightly-attacks run of 2026-11-03 Europe/Stockholm. Distributed practice g = 0.20 (95% CI 0.03–0.36; 15 studies, 56 effect sizes, 2,010 pupils), g = 0.39 against massed practice; interleaved versus blocked g = 0.40 (0.10–0.71; 10 studies, 57 effect sizes, 1,902 pupils); no publication bias by Egger. Massed/blocked did not match or beat spacing/interleaving on average. Boundaries found, not kills: spacing against less-distributed practice not significant; spacing significant only for gap/retention-interval ratios of 0.10–1; interleaving not significant with immediate feedback during practice (p = .75; sparse cells, explanation called conjecture by the authors). Not a restatement of the Murray et al. 2025 survive (US maths, mostly university courses): new population (school pupils aged 6–18, several subjects) and both strategies.
- Rewrite
- none (bounds only)
Linked sources
11 linked sources (7 supports, 4 limits)
Supports (7)
| Source | Basis |
|---|
| MEM-007 · Self-Regulated Learning: Beliefs, Techniques, and Illusions (2013) | Review: learners often hold a faulty mental model of how they learn, and their judgments of learning are swayed by current performance and fluency, so they misassess and mismanage their learning (abstract). Inference: a reason the candidate's techniques may need to be imposed rather than chosen. |
| LEARN-003 · Distributed Practice in Verbal Recall Tasks: A Review and Quantitative Synthesis (2006) | Listed as relevant to this belief; no one-line summary has been written yet. |
| LEARN-001 · Improving Students' Learning With Effective Learning Techniques: Promising Directions From Cognitive and Educational Psychology (2013) | Listed as relevant to this belief; no one-line summary has been written yet. |
| LEARN-024 · A Meta-analytic Review of the Effectiveness of Spacing and Retrieval Practice for Mathematics Learning (2025) | Preregistered meta: course-embedded maths spacing beat massed, g = 0.24 (17 studies, exams 2 days–5 weeks later). C11 kill-condition test survived 2026-10-17. |
| LEARN-021 · A randomized controlled trial of interleaved mathematics practice (2020) | Preregistered cluster RCT in 54 US grade-7 maths classes: interleaved practice beat blocked on an unannounced test a month later (61 % vs 38 %, d = 0.83). Abstract only. |
| LEARN-027 · A Meta-Analysis of the Effectiveness and Boundary Conditions of Retrieval Practice, Distributed Practice, and Interleaved Practice in Authentic School Classrooms (2026) | Kill-condition test survived 2026-11-03: authentic primary/secondary classrooms, spacing g = 0.20 (vs massed 0.39; vs less-distributed ns), interleaving g = 0.40 (ns with immediate feedback, p = .75); no publication bias. |
| LEARN-005 · Teaching the science of learning (2018) | Listed as relevant to this belief; no one-line summary has been written yet. |
Limits (4)
Review state: first-pass draft, pending human review.