Why mixing different topics leads to better learning than studying one thing at a time
Mixing different topics or types of problems during study sessions (interleaving) leads to better long-term retention than studying one topic at a time (blocking) - even though blocking feels more effective in the moment. This counterintuitive finding has been replicated across numerous studies.
Interleaving is a learning technique where you mix different topics, subjects, or types of problems during a single study session, rather than focusing on one topic until mastery before moving to the next.
While blocked practice creates the illusion of rapid improvement and feels more productive, interleaved practice forces your brain to constantly retrieve different strategies and discriminate between problem types - strengthening long-term retention and transfer of knowledge.
The chart above shows a striking finding from Rohrer & Taylor (2007). Students who used blocked practice performed better on immediate tests but showed dramatic decline after one week. Interleaved learners scored lower initially but retained far more knowledge over time.
Students learning different types of math problems (permutations, combinations, probability) showed 43% better performance on delayed tests when using interleaved practice versus blocked practice, despite feeling less confident during learning.
Following up after 9 months, interleaved learners retained 74% accuracy compared to only 20% for blocked learners. The effect became more pronounced over longer retention intervals, demonstrating that interleaving builds more durable memories.
Students who studied paintings by different artists in an interleaved fashion (mixing artists) performed 65% better at identifying new paintings by those artists compared to students who studied one artist at a time. Interleaving helped them learn to discriminate between styles.
Medical students learning to diagnose skin conditions showed 30% better diagnostic accuracy when conditions were presented in interleaved order versus blocked by condition type. The mixed practice better simulated real clinical environments.
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Interleaving forces you to identify which strategy or approach applies to each problem. This discrimination skill is crucial in real-world applications where problems don't come pre-sorted by type.
Each topic change requires you to retrieve different information from memory. This retrieval practice strengthens memory traces more than the automatic application you get with blocked practice.
The "interference" from mixing topics creates cognitive challenge that enhances encoding and retention. Your brain works harder to distinguish between similar concepts, creating stronger memories.
Blocked practice can lead to mindless repetition where you apply the same procedure without deep thought. Interleaving keeps you actively engaged and thinking critically about each problem.
When studying math, alternate between different types of problems (algebra, geometry, calculus) rather than completing all algebra problems first. This forces you to identify which approach each problem requires.
When using Quiz All, don't study questions organized by category in order. Mix categories together or use the shuffle feature to create interleaved practice sessions.
Instead of mastering Chapter 1 before starting Chapter 2, begin Chapter 2 while still reviewing Chapter 1. This creates natural interleaving across time periods.
For completely new material, some initial blocked practice helps establish basic understanding. After that, switch to interleaved practice for long-term retention.
Interleaving will feel harder and less effective than blocked practice during learning. You'll make more mistakes and feel less confident. This is normal and actually indicates the technique is working. Trust the research - the difficulty is "desirable" and leads to better long-term outcomes.
Create quizzes that mix different categories and topics. Use the shuffle feature to ensure true interleaving, and watch your long-term retention improve dramatically.