Mixing different types of exercises rather than doing twenty of the same kind

Cost: No cost at all. Simply rearrange the order of exercises in your workbook so they’re not grouped by type. The downside is that mixing them often lowers your immediate accuracy, which can feel like a step backward.
In plain terms: Practicing one type of problem over and over makes it feel easy at the time, but later you might struggle to recall which method to apply. Mixing several types together yields better long‑term results — though the improvement is moderate. This technique works best with visual material such as drawings or categorization tasks; it has a smaller effect on math problems, and for vocabulary memorization it’s actually better to practice in blocks.
Benefit: This finding comes from a comprehensive meta‑analysis that included 59 studies, 238 effect sizes, and 158 samples. Overall, interleaved practice produces a moderate benefit compared with blocked practice (Hedges’ g = 0.42). When broken down by material, visual tasks benefit the most (g = 0.67), while math problems show a smaller effect (g = 0.34). No significant advantage was found for expository texts or taste‑related tasks; for vocabulary, blocked practice actually performed better (g = −0.39). Regression analysis indicates that the benefit grows when categories are more similar, when items within a category are less alike, and when the material itself is more complex.
Evidence grade: A
Sources: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
Notes: The review cited in item 16 — which warns against relying solely on highlighting — rated interleaved practice as having a moderate effect, noting that evidence at the time was limited. Taken together, these studies suggest that interleaving works well for material that requires you to recognize a category and pick the right method, such as different math problem types, medical cases, or legal statutes. In contrast, content meant for rote memorization — like vocabulary or definitions — is better learned through blocked practice.