I’ve been immersed in the science of learning lately, and one theme has been present in nearly everything I’ve read: most of us just don’t know how to learn efficiently.
Scientists know why, too. We gravitate toward learning techniques (like re-reading) that feel effective as we’re using them yet are surprisingly inefficient when it comes to building long-term knowledge. In the moment, of course, that’s not obvious to us.
Unfortunately, the inverse is also true: the most efficient learning techniques don’t feel effective (and frankly, often don’t seem to make a whole lot of sense). The topic of this article, interleaving, is a perfect example. Interleaving sounds a little bonkers and feels jarring, but it delivers results.
What is interleaving?
Interleaving is simply studying or practicing two or more problem types or skills during a single session. Once we have a basic grasp on a concept, most of us tend to review it over and over until we understand it perfectly. But we’re better served to study it in conjunction with other, related ideas.
Interleaving is a simple concept, but it runs counter to both conventional wisdom and our own intuition. Doesn’t it feel like we should master one thing at a time? That’s certainly what my gut tells me.
Barbara Oakley, author of A Mind For Numbers: How to Excel at Math and Science (Even If You Flunked Algebra), explains the problem with the conventional approach:
When you are learning a new problem-solving approach, either from your teacher or from a book, you tend to learn the new technique and then practice it over and over again during the same study session. Continuing the study or practice after it is well understood is called overlearning. Overlearning can have its place—it can help produce an automaticity that is important when you are executing a serve in tennis or playing a perfect piano concerto. But be wary of repetitive overlearning during a single session in math and science learning—research has shown it can be a waste of valuable learning time.
As with many conventional learning techniques, overlearning gets the job done—it just takes a long time. This is a sneaky problem, and it explains why so many of us persist in using inefficient, outdated learning techniques. It’s not that they don’t work; they just work relatively poorly. And we don’t realize there’s a better way.
So, overlearning’s no good. Why is interleaving better?
Why is interleaving effective?
Interleaving helps us avoid overlearning, yes. But it has other benefits, too. In Make It Stick: The Science of Successful Learning, Peter Brown, Henry Roediger and Mark McDaniel give us three reasons interleaving works so well:
Mixing up problem types and specimens improves your ability to discriminate between types, identify the unifying characteristics within a type, and improves your success in a later test or in real-world settings where you must discern the kind of problem you’re trying to solve.
When we study one thing at a time, we’re learning without much context. Life doesn’t label situations by type, and before we can solve a real world problem, we need to know what kind of problem it is and what type of solution is likely to work.
Think of it this way: medical students don’t just learn about the various treatments available—ibuprofen is a nonsteroidal anti-inflammatory, codeine is an opioid—they spend thousands of hours learning when each treatment is appropriate to prescribe. As any doctor will tell you, making accurate diagnoses is the hard part.
In other words, context is everything, and interleaving prepares us accordingly.
How do I apply this to my life?
Depending on your goals and your stage in life, interleaving can have many applications.
If you’re a student, mix up problem types as you’re working. Interleaving is a fairly recent concept, and most textbooks still group questions and problems by type. Once you understand the basics of two or more types or problems, mix them up. Remember: your goal isn’t just to be able to work the problem or answer the question, it’s to be able to identify the type of problem you’re facing so you know which approach to take when you encounter similar problems “in the wild.”
If you’re a musician, resist the urge to dedicate each practice session to a narrow set of techniques or a single piece of music. Instead, structure your practice time so that you’re interleaving solo literature, orchestral excerpts, and jazz improvisation. As a performance approaches, you may want to shift away from interleaving and toward overlearning in order to cultivate the automaticity that Barbara Oakley references above. But in general, mix it up!
If you’re a lifelong learner, read multiple books at the same time, especially on the same or related subjects. Look for opportunities to make connections between authors, points of view, and entire disciplines. When you’re learning a new skill, work on multiple aspects simultaneously.
Interleaving is an easy way to learn more effectively, and it quickly becomes a good habit that works for you while requiring little ongoing maintenance.