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C23 weakened

For teenage and adult second-language learners, spreading vocabulary practice out instead of massing it gives clearly better results on tests a day or more later (g = 1.15 in a meta-analysis of controlled studies); for grammar this delayed advantage has not been shown (g = 0.11, not significant). Longer gaps have beaten shorter ones on delayed tests when the gaps fall within one session and in adults, but between separate sessions longer gaps have not been shown to add a reliable benefit (Kim & Webb 2022).

Status: weakened
Last change: 2026-11-05
Serves: Q1 (How do humans actually learn, and what helps them learn best?)
Ages: gymnasium, vuxen-livslangt
Area: Language learning
Relates to: C11 relates-to C23 (spacing in general vs in second-language learning)
Bounds: Second-language vocabulary, grammar and pronunciation practice in controlled studies, with delayed tests; not classroom-wide year-long durability (see C11 for spacing in general). Evidence on file: Kim & Webb 2022 (Language Learning 72(1), 269–319, DOI 10.1111/lang.12479; full text supplied by Jonatan 2026-11-04, read 2026-11-05): 48 experiments from 37 studies, 98 effect sizes, N = 3,411. Spaced vs massed: immediate g = 0.58 (95% CI 0.16 to 1.00; k = 11); delayed g = 0.80 (0.44 to 1.17; k = 15; I² = 82%; prediction interval −0.64 to 2.24). On delayed tests by learning target: vocabulary g = 1.15 (0.81 to 1.49; k = 10), grammar g = 0.11 (−0.32 to 0.54; k = 5), difference Q = 13.78, p < .001; adults 0.77 (k = 12), school-age learners (grades 1–12) 0.97 (k = 3). Longer vs shorter spacing: immediate g = −0.15 (ns; k = 17); delayed g = 0.40 (0.16 to 0.64; k = 32). On delayed tests: adults (university students or older) 0.54 (0.27 to 0.81; k = 24) vs school-age learners −0.04 (−0.52 to 0.44; k = 8), Q = 4.35, p = .04; spacing within one session 0.76 (0.42 to 1.11; k = 11) vs between separate sessions 0.18 (−0.10 to 0.45; k = 21), Q = 6.83, p = .01; grammar 0.56 (0.06 to 1.06; k = 8), vocabulary 0.34 (0.04 to 0.64; k = 22). Equal vs expanding spacing: no reliable difference. Publication bias: apparent in the delayed spaced-vs-massed subset; p-uniform judged it negligible, but the authors could not rule bias out and say true effects may be smaller. Few studies with school-age learners (3 spaced-vs-massed, 8 longer-vs-shorter effects); the claim says 'teenage' because the meta-analysis pools all school ages. Nakata 2015 (Studies in Second Language Acquisition, DOI 10.1017/S0272263114000825; abstract only): 128 Japanese college students, 20 word pairs; the amount of spacing had large effects; expanding spacing a small edge over equal spacing. Between-session gaps for grammar: open question 20 (Suzuki 2017; Suzuki & DeKeyser 2017).
What would kill this: A meta-analysis or large preregistered study of controlled L2 experiments finds no delayed-test advantage of spaced over massed practice for vocabulary, or an advantage smaller than about 0.2 standard deviations (sharpened 2026-11-05 with the weaken: Kim & Webb 2022's full text shows no established delayed advantage for grammar, g = 0.11 from 5 comparisons). Promoted from K53 on 2026-10-29 in the bold expansion Jonatan approved after four empty attack nights (26–29 Oct): new sharp claims in thin areas, each naming a comparison, a rough size or direction and a population.
Tutor consequence: none yet

Attack record

1 attack: 1 narrowed

2026-11-05 narrowed

Attack: The full text of the meta-analysis C23 rests on shows that the delayed spaced-over-massed advantage is carried by vocabulary (g = 1.15) while grammar shows none to speak of (g = 0.11, 95% CI −0.32 to 0.54), and that the longer-gap advantage on delayed tests comes from spacing within one session and from adults, not from longer gaps between separate sessions (g = 0.18, ns) or from school-age learners (g = −0.04), so C23's general statements for "second-language learners" and "longer gaps between sessions" overreach.
Target: claim-text
Source: Kim & Webb 2022 | Language Learning 72(1), 269–319, DOI 10.1111/lang.12479 (full text supplied by Jonatan 2026-11-04, read 2026-11-05; Crossref-checked 2026-10-27)
Steelmans to: C23 was written from this paper's abstract alone; its own moderator tables split the result. On delayed tests, vocabulary 1.15 (0.81 to 1.49; k = 10) vs grammar 0.11 (k = 5), Q = 13.78, p < .001 (Table 2). Longer vs shorter spacing on delayed tests: within one session 0.76 (0.42 to 1.11; k = 11) vs between separate sessions 0.18 (−0.10 to 0.45; k = 21), Q = 6.83, p = .01; adults 0.54 (k = 24) vs grades 1–12 −0.04 (k = 8), Q = 4.35, p = .04. The grammar estimate sits below C23's own 0.2 kill threshold, and "between sessions" is exactly the clause where longer gaps were not shown to help.
Why: Nightly-attacks 2026-11-05 Europe/Stockholm. Full text, Tables 1–2 and pp. 287–302: 48 experiments, 98 effect sizes, N = 3,411; spaced vs massed delayed g = 0.80 (0.44 to 1.17; k = 15); longer vs shorter delayed 0.40 (0.16 to 0.64; k = 32); grammar longer-vs-shorter 0.56 (0.06 to 1.06; k = 8). Publication bias apparent in the delayed spaced-vs-massed subset (p-uniform: negligible; authors cannot rule it out). Kill withheld: the vocabulary advantage is large and the overall delayed advantage is 0.80; grammar rests on 5 comparisons with a wide interval, so "not shown", not "no effect". Not a duplicate (empty ledger); not a restatement (Bounds held only the abstract and said "exact pooled size has not been read"). Not a preprint. Status alive → weakened. Claim field, Bounds and kill line rewritten in the same turn; brief and diagram core rewritten (C23 has no front-page rule). Also answers part of open question 20 (note added there).
Rewrite: claim-field+brief

Linked sources

5 linked sources (1 supports, 4 limits)

Supports (1)

Source	Basis
LANG-002 · Effects of Expanding and Equal Spacing on Second Language Vocabulary Learning (2015)	Abstract: large effect of amount of spacing on L2 vocabulary (college students).

Limits (4)

Source	Basis
LANG-009 · On the Effects of Spaced Versus Massed Practice on Deliberate Learning of English Idioms across L2 Proficiency Levels (2026 (online 5 Aug 2026))	Full text (2026-11-10): classroom quasi-experiment, 199 Iranian EFL young adults, opaque idioms, same 100 minutes spaced or massed: spaced beat massed about 100 days later for mid- and high-proficiency learners but not for low-proficiency learners (cued-form 67.4 vs 71.5 %, ns). Held as open question 26.
LANG-001 · The Effects of Spaced Practice on Second Language Learning: A Meta-Analysis (2022)	Full text (2026-11-05): spaced beat massed on delayed tests, g = 0.80 (vocabulary 1.15, grammar 0.11 ns); longer beat shorter spacing on delayed tests 0.40, but within one session 0.76 vs between sessions 0.18 ns, adults 0.54 vs school-age −0.04. Supports the vocabulary core; weakened C23 2026-11-05.
LANG-005 · The Optimal Distribution of Practice for the Acquisition of L2 Morphology: A Conceptual Replication and Extension (2017)	Randomised, 60 university students (54 analysed), novel-language vocabulary and grammar in oral production: sessions 3.3 days apart beat 7 days apart on 7- and 28-day delayed tests (d ≈ 0.5). Held as open question 20.
LANG-006 · Effects of distributed practice on the proceduralization of morphology (2017)	Randomised, 40 university learners of Japanese: two sessions 1 day apart matched 7 days apart on accuracy 28 days later. Small; held as open question 20.

Review state: first-pass draft, pending human review.