Mix problem types instead of doing twenty of the same kind in a row
A long run of one problem type feels smooth, but may not teach you which method to choose later. Mixing types produces a moderate overall long-term benefit. Results depend on the material: visual recognition and classification benefit most, mathematics less, and vocabulary can work better with blocked practice.
What it takes
Nothing. Change the order of exercises. Mixed practice may feel like a setback because your immediate accuracy can be lower.
What you may gain
A multilevel meta-analysis included 59 studies, 238 effect sizes, and 158 samples. The overall advantage of interleaving over blocked practice was moderate, Hedges' g=0.42. Paintings showed the strongest effect, g=0.67, with other visual materials also benefiting. Mathematics had a smaller effect, g=0.34. Overall effects for expository text and taste materials were not significant. For words, blocked practice performed better, g=−0.39. Regression analysis suggested greater benefits when categories resembled one another more, examples within a category differed more, and materials were more complex.
Context & considerations
The review cited in entry 16 rated interleaving moderate utility partly because research was then limited. Taken together, the findings favor mixing material where you must recognize a category and choose a method, such as mathematics problem types, clinical cases, or applications of legal rules. Material requiring straightforward memorization, such as vocabulary or definitions, may suit blocked practice better.
Research & references
Brunmair M, Richter T (2019). Similarity matters: A meta-analysis of interleaved learning and its moderators. Psychological Bulletin, 145(11), 1029–1052. https://doi.org/10.1037/bul0000209