Interleaving
Mix topics in one session — don’t block them.
What the Research Says
Most students revise by blocking — an hour on materials, an hour on maths, an hour on health and safety. It feels productive and the topic seems clear by the end. Interleaving is the opposite: you jump between topics inside a single session. It feels worse at the time, and you’ll make more mistakes. But when the real exam arrives, you will be dramatically better at knowing which technique to apply — and that is usually the hardest part of any exam question.
Evidence Base
| Study | Finding | Impact |
|---|---|---|
| Rohrer & Taylor (2007) | Students who interleaved maths topics scored 43% higher on delayed tests than blocked-practice students. | Same time spent — huge difference in exam performance. |
| Birnbaum et al. (2013) | Interleaved learners felt LESS confident during practice but performed BETTER in the test. | If revision feels too easy, interleave. |
| Bjork & Bjork (2011) | Desirable difficulties — including interleaving — create durable long-term learning at the cost of short-term performance. | Short-term struggle is the price of long-term gain. |
| Taylor & Rohrer (2010) | Benefit was largest when topics looked superficially similar — students learnt to DISTINGUISH them. | Most useful where students confuse similar techniques. |
Step-by-Step Method
- 1Pick 3–5 related topics — topics that share a paper, a theme, or a question type. Similar enough that students confuse them.
- 2Make a mixed problem set — 10–15 questions drawn randomly from all the topics. Don’t tell yourself which topic each question belongs to.
- 3Attempt each question cold — first step is identifying what’s being asked. That identification is the skill you’re training.
- 4Mark after every question — note which topic each one was. Pay attention to mis-identifications — those are the highest-value gaps.
- 5Rebuild a new mixed set tomorrow — same topics, different questions. Different order. Over time, misclassifications drop.
- 6Expect to feel worse than blocked practice — that’s the right feeling. Your exam self will thank you.
Instead of spending an entire session on materials science alone, interleave it with engineering mathematics. Write a set of questions that mixes material-selection problems (which metal is most suitable for a marine environment and why?), calculation problems (a gear with a load of 600 N and an effort of 150 N — calculate the mechanical advantage), and joining-process questions (which method — brazing, soldering, or welding — would you use to join two thin copper pipes?). Working through a mixed set trains you to read a question and identify what it is actually asking before reaching for an answer.
In the final weeks before your exam, interleave smart materials, composites, and traditional metals in a single flashcard run. The exam may give you a scenario — an aircraft wing bracket — and ask you to compare carbon fibre reinforced polymer (CFRP) with aluminium alloy. If you have always revised these categories separately, choosing between them under time pressure is harder than if you have practised making comparisons across all three in every session. Interleaving builds the discrimination skill the question is actually testing.
Common Pitfalls
- Random, not related. Interleaving Engineering with a completely different subject is just subject-switching. Interleave WITHIN Engineering — related topics that students confuse.
- Giving up when it feels hard. The discomfort is the signal that it’s working. Don’t revert to blocked practice because interleaving feels slow.
- Labelling the topic at the top of each question. Defeats the point — the identification IS the training.
- Using it too early in learning. You need baseline familiarity with each topic first. Interleaving is for consolidation, not first exposure.
When to Use This
Once you’ve covered a handful of related topics — usually partway through a term — start weaving them into mixed practice sessions. Very useful in the final 8–10 weeks before your exam when you’re moving from learning to applying. Full practice papers are the ultimate interleaving exercise, because they force you to identify question types cold.