The optimal interstudy interval increases as the retention interval increases¶

Claim · All claims
Evidence · 1 study · quant-synthesis r2 · q2
Currency · newest study 2006 · checked against its sources 2026-10-19 (automated, 1 of 1 entry) · not reviewed by a person

Subclaims¶

q2 i? The difference-lag analyses found the optimal ISI difference grew with the retention interval, the absolute-ISI analyses found the optimal ISI bin grew with it, and a qualitative within-study analysis (subject to the authors' caveats about local maxima and coarse ISI sampling) pointed the same way. → Cepeda 2006

Evidence¶

Cepeda 2006¶

Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed Practice in Verbal Recall Tasks: A Review and Quantitative Synthesis. Psychological Bulletin, 132(3), 354-380. https://doi.org/10.1037/0033-2909.132.3.354

q2 · i? · quant-synthesis · r2

Meta-analytic lag analyses binning accuracy differences and absolute accuracy by ISI and retention interval (Figures 3 and 6, Tables 3 and 5). Within-study analyses of studies spanning sub- and supraday ISIs (e.g., Cepeda et al., 2005; Gordon, 1925) support the same pattern.

"the results show a tendency for the greatest increases in final-test recall to be found at longer ISI differences, the longer the retention interval. The qualitative pattern that optimal ISI difference increases as retention interval increases is supported by quantitative analyses of the bin data"

Studies bearing on this claim¶

How long should the gap between sessions be, given when the knowledge is needed? This table gathers the studies behind this claim and the 7 narrower claims that bear on it: 7 distinct studies (3 causal, 2 quant-synthesis, 2 review), q1–q3, 0 of 7 with an effect size coded. One row per study, codes as each entry records them; no effect is averaged and no verdict is drawn. Built by scripts/synthesize_claim.py from eval/synthesis/; a row that looks wrong is fixed on the claim it comes from.

Discussion¶

Related Claims¶

• Expanding interstudy intervals led to better recall than fixed intervals, but conclusions are tentative — related
• ISI effects on recall are nonmonotonic and depend jointly on retention interval — possibly the same claim (merge candidate)
• Spaced Repetition Improves Retention — related
• Relearning-to-criterion designs confound distribution of practice with amount of second-session practice — related
• The authors attribute the spaced-practice knowledge benefit to deeper learning or transfer, because quiz and final-test items were never repeated — related
• In continuous recognition memory, the lag function is inverted U-shaped after a short retention interval and monotonically increasing after a long retention interval — related
• Recent research identifies time intervals during which spaced study should occur to maximize memory retention — a broader claim this one bears on
• In paired-associate paradigms, the lag function is decreasing at very short retention intervals, inverted U-shaped at slightly longer intervals, and monotonically increasing at long intervals — related
• The testing effect is largest at a retention interval of 1–6 days (g = 0.82) and robust across all intervals — related
• Eight-day review improved a five-week science test versus one-day review in a simulated university classroom — a narrower finding that bears on this claim
• Distributed practice benefits L2 learning, and one review argues that spreading it over years can be worse than over months — related
• Proportional measurement of relearning intervals poses a scaling problem for mapping optimal relearning schedules — related
• Longer retention intervals between pre- and post-test weaken the effect of mental simulation — related
• Earlier studies reported that quicker recall accompanied better memory results, but with little supporting evidence — related
• The more the substitution practice was distributed over days, the larger the practice gains and the more pronounced the negative transfer effects — related