Beru Learning

When learning a new skill, our natural instinct is to use 'blocked practice.' We drill one concept or motion over and over until we feel we've mastered it, then move on to the next. For example, a math student might do 20 problems on topic A, then 20 on topic B. This approach feels effective because it leads to rapid improvement in the short term.

However, cognitive science shows there's a better way. Interleaving, or mixed practice, involves alternating between different but related topics or skills within a single study session. It feels slower and more difficult in the moment, but it leads to more durable, flexible learning and better long-term performance.

Blocked Practice vs. Interleaving: An Example

Imagine you're learning to identify the works of three different painters. A blocked practice approach would be to study 10 paintings by Picasso, then 10 by Van Gogh, then 10 by Monet. An interleaved approach would be to study a mixed set of 30 paintings, one after another in a random order.

Blocked Practice: AAA BBB CCC. You get good at recognizing 'A' when you're in the 'A' block, but you're not learning to differentiate it from B and C.
Interleaving: ABC BAC CAB. Each time you see a painting, you have to actively identify which artist it belongs to, forcing your brain to notice the subtle differences.

The blocked practice group will perform better during the practice session, but the interleaving group will perform significantly better on a test a week later.

Why Does Interleaving Work?

Interleaving leverages a concept called 'desirable difficulty.' It feels harder because it forces your brain to work harder, and this extra effort is what encodes the learning more deeply.

It Improves Discrimination: By placing different concepts side-by-side, interleaving forces your brain to constantly compare and contrast them. This helps you learn to distinguish between similar-looking problems or concepts, a critical skill for real-world application.
It Strengthens Retrieval: With blocked practice, the solution is often fresh in your short-term memory. With interleaving, each problem is a fresh challenge. You have to actively retrieve the correct strategy from your long-term memory, which strengthens that memory pathway, similar to how spaced repetition works.
It Simulates Real-World Conditions: Tests and real-life situations are rarely blocked. They require you to choose the right tool for the job from a mix of possibilities. Interleaving prepares you for this by simulating that mixed environment during practice.

How to Structure an Interleaved Practice Session

You can apply interleaving to almost any subject, from math and science to sports and music. Here’s how to set it up.

For Studying: If you're studying for a physics exam, don't do all the 'gravity' problems and then all the 'friction' problems. Instead, mix them up in your problem sets. Work on a few of each type, then shuffle them.
For Sports: A baseball player shouldn't just hit 50 fastballs in a row. A better practice involves the pitcher mixing in fastballs, curveballs, and sliders randomly. This forces the batter to identify the pitch and react accordingly.
For Music: Instead of practicing one scale for 20 minutes, then the next, practice three or four different scales, alternating between them every few minutes.

The key is to mix topics that are related but distinct. Interleaving chemistry and history won't help much. Interleaving different types of chemical reactions, however, will.

Frequently Asked Questions

When should I use blocked practice?

Blocked practice is useful when you are first learning a brand-new, complex skill. You may need a few repetitions just to get the basic idea down. But as soon as you have a basic grasp, you should switch to interleaved practice as soon as possible.

This feels really inefficient. Am I doing it wrong?

No, that feeling of difficulty is a sign that it's working. The short-term performance drop is the 'desirable difficulty' that leads to better long-term learning. You have to trust the process, even when it feels less productive than drilling.

Can I combine interleaving with other techniques?

Absolutely. Interleaving works extremely well with spaced repetition and active recall. A great study session would involve actively solving mixed-up problems (interleaving and active recall) from topics you learned at increasing intervals (spaced repetition).

Key Takeaways

Interleaving is the strategy of mixing related but distinct topics within a single practice session.
It is more effective for long-term retention and real-world application than 'blocked practice' (drilling one topic at a time).
The method works by forcing your brain to discriminate between concepts and actively retrieve strategies.
Interleaving feels harder and less productive in the short term, but this 'desirable difficulty' leads to superior learning.
Switch from blocked practice to interleaving as soon as you have a basic understanding of the individual concepts.

Interleaving: The Counterintuitive Way to Learn Better