Similarity Matters: A Meta-Analysis of Interleaved Learning and Its Moderators
Brunmair, M., & Richter, T. · 2019
grade Cmeta-analysisindependentunreplicatednumbers spot-checked
Sample
59 studies / 238 effect sizes
Population
Mostly university/lab; inductive category learning + math; artificial/aligned materials.
Design
Multilevel meta of interleaving vs blocking on inductive learning, with material-type moderators, publication-bias (trim-and-fill), and p-curve analyses.
Key findings
Interleaving is real but NARROW: strong for perceptual/inductive category learning (paintings 0.67), small for math (0.34), NULL for expository text, NEGATIVE for word learning (-0.39, blocking wins). Mechanism is discriminative contrast (learning WHICH category applies), not general deep processing — so it helps most when categories are confusable. Trim-and-fill drops the overall effect to 0.29.
Genetic confound
Domain discrimination-skill outcome; no g. Larger for younger/pure-student samples.
Replication notes
Numbers verified. The definitive statement that interleaving is narrow and material-dependent.
DOI / URL
10.1037/bul0000209
Effects
| Outcome | Metric | Value | Measure | Timing | Vs | Horizon | Class |
|---|---|---|---|---|---|---|---|
| Overall interleaving vs blocking | g | 0.42 (trim-and-fill 0.29) | researcher-designed | mixed; lab-dominated | active-alternative | unclear | domain-skill |
| Paintings / visual category learning (best case) | g | 0.67 | researcher-designed | lab | active-alternative | end-of-treatment | domain-skill |
| Mathematics | g | 0.34 (small) | researcher-designed | mixed lab/classroom | active-alternative | unclear | domain-skill |
| Word learning — BLOCKING wins (reversal) | g | -0.39 | researcher-designed | lab; short | active-alternative | end-of-treatment | domain-skill |
| Expository text and tastes | g | non-significant | researcher-designed | lab | active-alternative | end-of-treatment | domain-skill |
Cited by
- Interleaving (mixing problem types vs blocking)moderate supportconf: mediumgc: low