Study: More evidence for ‘interleaving’
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Study: More evidence for ‘interleaving’

Practice sessions typically consist of learners rehearsing a single skill until they master it. But a growing body of research on the power of “interleaving” suggests that you get better results when you mix things up.

A recent study conducted in a real-world classroom found that interleaved practice sessions – sessions that ask learners to revisit a number of different skills – are more beneficial than practice focused solely on one skill.

The research

The study took place in a math class over the course of three months. Learners were divided into two groups. The traditional, or “blocked” practice, group were taught a new math concept each day followed by practice problems focused solely on the new concept.

The interleaved practice group received the same instruction but was assigned problems that included several recently learned concepts, not just the one from that day’s class. The variety of problems forced learners to consider and revisit numerous strategies before coming to a final solution.

At the end of the 30-day research period, both groups were given a review session, then a final test. The interleaved practice group scored an average of 80 percent on the exam, 16 points higher than the blocked practice group.

This finding alone shows the significant value of interleaving. But one month later, the researchers found something even more impressive.

To gauge interleaving’s effect on long-term retention, the researchers returned after 30 days to administer a follow-up test. The results were even more dramatic. The interleaved practice group averaged 74 percent, dropping just 6 percentage points over the month, leading researchers to write that interleaved practice provided “near immunity against forgetting.”

The blocked practice students’ performance told a very different story. Their scores plummeted, averaging 42 percent on the test – a 22-point drop.

Why interleaving isn’t standard practice

This study – and many others – demonstrates the significant boost interleaving can give learners and training programs. So why isn’t it widely used?

The answer, the researchers suggest, is simple: Learners don’t like practicing this way. It’s challenging to switch from skill to skill during practice. It’s much easier to focus on one thing at a time. But “easy” isn’t how we learn best.

Research has proven that we tend to learn more when we struggle. Interleaving forces learners to recall topics they learned days, weeks or months ago, which can be tough. And that struggle strengthens memory, making the content easier to recall in the future.

Some struggle upfront leads to serious gains in the long term.


Show learners the power. Before rolling out interleaved practice in your training program, explain the benefits. Tell learners that it’s proven to improve learning and long-term retention. And let them know that, when it comes to learning something new, struggle is a good thing.

Conduct interleaved practice. While you may get some resistance from learners at first, the benefits of interleaved practice are too significant to ignore. So, the next time you conduct a practice session, a quiz or a role play, consider including several different topics or skills, not just the one they learned most recently.

Encourage learners to use it on their own.
Make sure learners know that blocked practice may be easier and more efficient in the short term, but if their goal is long-term retention, interleaved practice will serve them much better.

Rohrer, D., et al. (2015). Interleaved practice improves mathematics learning. Journal of Educational Psychology, 107(3), 900-908.

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