Are We Learning All Wrong? A Look at Interleaving

When you normally try to learn a skill, you focus on one particular aspect at a time. If you’re student in school focused on multiplication, your homework will likely consist of multiplication problems of varying difficulties. Similarly, if you’re trying to improve your basketball game, you might focus on shooting free throws for an hour. Then, move to three point shots.

This type of learning is referred to as block practice referring to the fact that the skills are broken down and focused on one at a time. Research is now indicating that even though we’ve been using this method for many years, it might not be the best method to learn.

Researchers Tim Lee and Dick Schmidt co-wrote an influential textbook, Motor Control and Learning: A Behavioral Emphasis, popularizing the a technique referred to as interleaving or “variable practice.”

Interleaving is a form of learning wherein participants practice skills as a mixed bag rather than one at a time. With interleaving, a student might practice a multiplication problem alongside several addition and subtraction problems. In the basketball example, you may take a free-throw shot. Then, step back and throw up a three. Finally, you might charge the basket for a lay-up.

Interleaving seems like quite the change of pace from the normal block practice in the school setting. Doug Rohrer, a psychologist from the University of South Florida, explains the problem with the traditional teaching method:

“There are always two steps to solving a problem: identify the solving strategy, and then execute it,” Rohrer said. “In blocked study, [students] know that this is a unit on, say, the Pythagorean theorem, so they don’t need to choose a strategy. All they have to do is execute, over and over.” (Source)

So, to see how interleaving actually works in the classroom, Rohrer approached a seventh-grade classroom in Tampa Bay with a simple experiment. For one group, the teacher interleaved their homework assignments mixing up problems from the current lesson alongside techniques they learned months previously. The other group received traditional “block” homework focused only on the lesson at hand.

At the end of the experiment, the children were given a test. On those concepts that were practiced in an interleaving context, the students scored 72% compared to 38% for those learned through block practice.

Additional research has aimed to identify exactly what makes interleaving so effective. A recent paper identifies the major benefit to interleaving as discriminative contrast. Through practicing different concepts together, aspiring learners can identify the differences between two concepts rather than solely being exposed to the similarities that block learning provides. By highlighting what’s different about two concepts, students gain a better understanding of the idea overall.

We’ve been drilled for years that block practice is the preferred method for learning. Normally, we don’t have a great idea of how we learn best.

The great majority of the participants in the present study, as well as those in prior studies…judged that they had learned more effectively with blocked than with interleaved study. (Source)

This understanding led researchers to conclude with this piece of advice for anyone trying to learn a new skill:

If your intuition tells you to block, you should probably interleave.

Photo credit: Matthew Paulson