Chapter 9 Quiz: Interleaving

Answer from memory before checking the guide.

1. Define interleaved practice and blocked practice. Use the notation AABBCC vs. ABCABC to illustrate the difference.

2. In research studies comparing interleaved and blocked math practice, which group typically performs better (a) during practice, and (b) on delayed tests? What is surprising about the disconnect between these two results?

3. What is the discrimination hypothesis? Explain in your own words why interleaving produces the learning benefit that it does.

4. What specific skill does blocked practice fail to train that interleaved practice does train? Why does this matter for real-world performance?

5. True or false: interleaving is always better than blocking for learning. Explain the nuances — when is blocking more appropriate?

6. What is the "blocking → interleaving progression," and why might it be better than going straight to interleaving for a complete beginner?

7. In sports and motor skill learning, what is the term used for the equivalent of interleaving? Describe what it looks like in practice.

8. Why do students typically prefer blocked practice even when interleaved practice produces better outcomes? What does this tell us about using subjective feelings of learning as a guide?

9. A student studying Spanish spends one week only practicing present-tense conjugations, then one week only practicing past tense, then one week only practicing future tense. Redesign this schedule using interleaving principles.

10. What is the "contextual interference effect," and in which domain of learning was it originally documented?

11. You're studying for a statistics exam that covers hypothesis testing, confidence intervals, and regression. Your textbook has separate problem sets for each topic. How would you redesign your practice to incorporate interleaving?

12. Describe what Kornell & Bjork (2008) found about interleaving and artistic style recognition. Why is this study important for understanding the breadth of the interleaving effect?

Answer Guide

1. Blocked practice (AABBCC): All problems or material of Type A are completed before moving to Type B, then all of Type B before Type C. Interleaved practice (ABCABC): Types A, B, and C are alternated throughout the session — you switch before completing any one type. Example: AABBCC = do all calculus problems, then all statistics problems, then all algebra problems. ABCABC = alternate between all three throughout the session.

2. (a) The blocked group typically performs better during practice. (b) The interleaved group typically performs significantly better on delayed tests. The surprise: students in the interleaved condition often feel like they're learning less and predict the blocked approach would produce better exam scores — but the evidence contradicts their predictions. Performance during practice and long-term learning are different things.

3. The discrimination hypothesis proposes that interleaving benefits learning because it requires you to identify which technique or approach applies to each problem before applying it. In blocked practice, the approach is already "loaded" — you've been doing the same type of problem for twenty minutes. You only practice execution. In interleaved practice, each new problem requires you to identify what type it is before solving it. This identification skill is exactly what real tests and real-world applications require.

4. Blocked practice fails to train the selection skill — the ability to identify which technique or approach is appropriate given the problem at hand. Interleaved practice trains the full sequence: perceive a problem, identify its type, select the appropriate approach, execute it. In real tests and real work, problems don't come labeled by type; selection is always required. Blocked practice leaves this skill completely untrained.

5. False — interleaving is not always better. At the very beginning of learning a new skill or concept (complete beginner stage), some blocking may be necessary to build basic functional understanding before mixing topics. If you don't have any familiarity with Topic A, you can't benefit from the discrimination practice of mixing A with B and C. The appropriate approach: block initially to build basic competence, then transition to interleaving once you can execute each approach at a basic level.

6. The blocking → interleaving progression: (1) introduce each new concept or technique through brief blocked practice to build basic understanding and functional competence; (2) once you can execute each approach reasonably well, switch to interleaved practice mixing all the concepts you've introduced. This works better than immediate interleaving for complete beginners because you need some basic level of competence with each component before you can productively practice discriminating between them. If you have no idea what any of the approaches are, mixed practice is just confusion.

7. In motor skill and sports learning, the equivalent is called variable practice (or the "contextual interference effect" in the research literature). It looks like: mixing different drills, exercises, and conditions within a practice session rather than blocking by skill. A swimmer doing variable practice would mix backstroke drills, freestyle drills, and race simulations rather than completing all of one before moving to the next. A tennis player would mix forehand, backhand, and serve practice rather than drilling each in a block.

8. Students prefer blocked practice because it produces better immediate performance — they're in a rhythm, getting problems right, feeling competent. Interleaved practice feels rougher, more uncertain, and less satisfying. The takeaway: feelings of productivity during a study session are unreliable guides to actual learning. Smooth, flowing practice often indicates shallow encoding within a narrow context. The research consistently shows that the less satisfying but harder interleaved practice produces better transfer and retention.

9. Instead of spending one full week on each tense: Mix all three tenses within each study session from the start. A session might include: five present-tense exercises, five past-tense exercises, five future-tense exercises — then rotate again. Or: a single conversation/writing prompt that requires all three tenses. The key: don't complete one tense entirely before introducing the next. Once each tense is introduced, mix them. This trains the selection skill — deciding which tense is appropriate — which is what real speaking requires.

10. The contextual interference effect is the finding that practicing multiple variations or types of a task in a mixed (interleaved) order produces lower performance during practice but better retention and transfer than practicing each variation in a block. It was originally documented in motor learning research in the 1970s-80s, in studies of movement sequences and physical skills. Battig (1979) first named and described the contextual interference effect in motor learning; it was subsequently found to apply to cognitive learning as well.

11. Redesign: Instead of completing the hypothesis testing problem set, then the confidence interval problem set, then the regression problem set, mix problems from all three in each practice session. Methods: (a) Create a combined document or spreadsheet with problems from all three topics and shuffle them. (b) Work on 5 problems from each set, rotating — don't finish any one set before switching. (c) Use practice exams, which are naturally interleaved. (d) When reviewing for the exam, always use mixed review rather than topic-by-topic review.

12. Kornell & Bjork (2008) had participants view paintings and try to learn which artists created them. The interleaved group (seeing multiple artists' works mixed together) dramatically outperformed the blocked group (seeing all of one artist's work, then all of another's) on a subsequent artist identification test. This is important because it extends interleaving beyond mathematics — where "different problem types" is a clear concept — to a naturalistic perceptual discrimination task. It suggests the interleaving benefit is broad, applying whenever learners need to discriminate between complex patterns or stimuli rather than just execute a specific technique.