Chapter 9 Exercises: Interleaving

The exercises in this chapter are designed to let you experience interleaving directly — because reading about it and experiencing it are quite different. Your immediate feeling of productivity is going to be misleading. Try to suspend judgment until you test yourself.

Exercise 1: The Preference vs. Performance Audit (10 minutes)

Before doing any of the other exercises, answer these questions honestly:

1. When you study multiple subjects in one sitting, do you tend to study one fully before switching, or do you rotate between them?

2. When you have a problem set or exercise set, do you typically work straight through it from beginning to end, or do you skip around?

3. If given the choice, would you prefer to: (a) spend two hours on chemistry, then two hours on history, or (b) alternate between chemistry and history in 30-minute blocks? Why?

4. Think back to a subject where you felt you understood the material during class or study sessions but then performed worse on the exam than you expected. What might interleaving have looked like for that subject?

Write your answers. Keep them — you'll revisit them after doing the remaining exercises to see whether your preferences have shifted.

Exercise 2: Design a Mixed Problem Set (30–45 minutes)

Requirements: A subject you're currently studying that has at least three distinct topic areas, each with practice problems or exercises available.

This works best with math, science, or a foreign language, but can be adapted for almost any structured academic subject.

Step 1: Identify three topic areas.

Choose three topics you've covered recently (or are currently covering) that require different approaches or techniques. They should be related enough that they could appear on the same exam, but distinct enough that they require different problem-solving approaches.

Examples: - Algebra: linear equations, quadratic equations, systems of equations - Chemistry: stoichiometry, limiting reagents, percent yield - Spanish: past tense, future tense, subjunctive mood - Statistics: hypothesis testing, confidence intervals, correlation

Step 2: Gather six to eight practice problems from each topic. Shuffle them randomly (number them and use a random number generator, or physically shuffle printed problems). Don't label them by topic — remove any contextual cues that tell you which category each problem belongs to.

Step 3: Complete the mixed set. Time yourself. Note when you find yourself needing to figure out what approach to use before applying it.

Step 4: Score the set. Note your accuracy overall and per topic.

Step 5: Compare to your usual experience. How did your performance compare to working through a blocked set of the same problems? Did some topics reveal weaker understanding than others? (This is valuable — those topics need more work.)

Reflection: - How many times did you have to pause to identify the problem type before solving? - Was any topic harder to identify than others? Why? - How did it feel compared to blocked practice?

Exercise 3: The Blocked vs. Interleaved Experiment (4–7 days)

This is the most rigorous exercise in this chapter. Run it on yourself.

Requirements: Two sets of related material you haven't yet studied, from the same subject area. They should be similar in difficulty and scope.

Week 1, Day 1: Blocked study session.

Study Material Set A using completely blocked practice: study all of one subtopic fully, then all of the next, then all of the next. Take a brief quiz immediately after (write down everything you can recall, or answer the practice questions from each subtopic). Record your performance.

The same day (or Day 2): Interleaved study session.

Study Material Set B using interleaved practice: mix the subtopics together, switching between them every 10-15 minutes. Don't complete any one subtopic before switching. Take a brief quiz immediately after. Record your performance.

Compare immediate quiz scores. Which set did you score higher on immediately? Most people score slightly higher on the blocked material — it was just reviewed in a focused way. Note this.

5-7 days later: Delayed test.

Without any review of either material set, test yourself on both. Same format: write down everything you can recall, or answer fresh practice questions.

Compare: - Blocked set recall at delay: ___ - Interleaved set recall at delay: ___

The research prediction: the interleaved set should show better retention at delay, even if it showed worse performance immediately after study.

Note your results. Did the interleaved set outperform at delay? If so, by how much? If not, examine why — were the sets genuinely equivalent in difficulty?

Exercise 4: Variable Practice Redesign (For Skills Learners) (20–30 minutes planning, then implement)

This exercise is for learners working on a skill — athletic training, musical performance, a craft, or any procedural domain.

Step 1: Map your current practice structure.

Write out what a typical practice session looks like for you. Be specific: what do you do first, for how long, in what order?

Example (competitive swimming): "15 min freestyle warmup → 20 min backstroke drill (same drill x 6 sets) → 20 min freestyle technique (same drill x 6 sets) → 10 min butterfly kick → cool down"

Step 2: Identify the blocking.

Circle the parts where you're doing the same thing repeatedly in one extended block.

Step 3: Design a variable version.

Redesign the same total practice time as a variable session. Mix drills and techniques. Alternate between different skills. Vary the conditions, speeds, or targets.

Example redesign: "10 min warmup (mix strokes) → 5 min backstroke drill → 5 min freestyle drill → 5 min race-pace simulation → 5 min butterfly technique → 5 min backstroke drill (different variant) → 5 min freestyle at varied pace → 5 min turns practice (mixed strokes) → 5 min sprint → cool down"

Step 4: Implement and notice.

Use the variable design for your next three practice sessions.

After each session, note: - Did it feel harder or easier to maintain quality? - Were there moments where you had to think about which technique to apply, rather than just executing automatically? - What felt most uncomfortable?

After three sessions: - Has anything improved that surprised you? - Has your performance in any area gotten worse? (Some regression during transition to variable practice is normal.)

Exercise 5: Interleaved Reading (Ongoing Strategy)

This exercise transforms how you approach reading multiple books or sources simultaneously — a common situation for students and professional learners.

Most readers finish one book completely before starting another. This is blocked.

Try: read multiple related sources simultaneously, rotating between them.

How to do it: - Select two or three books, articles, or course chapters on the same broad topic (e.g., two books on learning science, or three articles on machine learning algorithms) - Allocate time to each in your reading sessions, switching before you finish each - The connections and contrasts you notice between the sources are themselves a form of elaborative encoding

This isn't the same as never finishing books — you will finish each one. But by reading them in parallel, you create natural opportunities for comparison, contrast, and integration.

Try it: With your current learning goal, identify two sources you could read in parallel. Start this week. After two weeks, note whether reading them together revealed insights that reading each separately might have missed.

Reflection Questions

1. After completing at least two of the exercises: has your feeling about interleaving changed from when you answered Exercise 1? If so, what changed it?

2. Think about a subject you studied in school where you feel you learned the material at the time but can't recall much of it now. With what you know about interleaving and spaced repetition, what do you think happened?

3. What's the hardest part about implementing interleaving in your specific learning context? Is it structural (your textbook forces blocked study)? Psychological (you prefer the feeling of blocked study)? Practical (hard to find mixed practice problems)?

4. Where in your life do you experience "practice" that is naturally interleaved — where you're always having to identify what situation you're facing before responding? How does performance in that area compare to areas where you practice in a more blocked way?