The idea here is simple. Rather than drill yourself on the capital of Alabama twenty times, then the capital of Alaska twenty times, and so on in alphabetical order, you could mix it up. Alabama, then Alaska, then Arizona, then… and when you finish, go back to Alabama, and repeat twenty times. That way, you’re never recalling from working memory. Most people can only hold only about seven items in working memory; hence the title of Miller’s classic 1956 paper on the subject, “The magic number seven, plus or minus two.” So by putting so many other things to recall in between repeated questions, you’re forcing the relevant knowledge out of working memory.

This way, you successfully practice the long-term recall that you wanted to practice. For the really long term, you work up to reviews separated by days or weeks with spaced repetition. But when you’re learning, not just memorizing, it’s important to frequently clear your working memory to make sure your gains will last.

An even better approach is to randomize the order of the fifty states. With the above method, you can always remember “Juneau comes after Montgomery” rather than associating Juneau with Alaska. This makes your memory more fragile. (It’s also, sadly, exactly how we practice piano, and often results in preventable memory lapses.) By forcing yourself to recall things at random, you build stronger connections.

(By the way, what’s the capital of Lithuania?)

This is a well-studied effect, and it shows up in many domains, from motor to cognitive skills (Rohrer and Pashler, 2010). The studies reported in “The shuffling of math problems improves learning” (Rohrer and Taylor, 2007) show exactly what the title claims. Students’ performance was “vastly superior” when they practiced problems that were mixed randomly compared to when the problems were blocked by type.

Even more importantly, the authors were able to distinguish between the effects of spaced repetition—that is, the mere fact that similar problems were further apart in time when they were randomly mixed—from the effects of interleaved practice (which they call mixed practice)—that is, specifically having a variety of problems in between similar problems. What did they find?

While blocked practice proved superior to mixed practice during the practice session, subsequent test scores were much greater when practice was mixed rather than blocked.

In other words, blocked (or massed) practice will feel productive and successful at the time—but for long term gains, you need to mix up your practice. The authors attribute this success to the way that mixed practice forces the students not just to know how to solve a given problem, but to know which solution procedure to apply. They reinforced this conclusion in their 2010 paper. When similar practice problems are blocked, students are able to just apply the same procedure over and over again. But when they’re mixed, students have to dig into their longer-term memory or review the material again to figure out which technique to apply.

How does this apply to learning music?

• Divide your piece into small phrases or passages that you can practice individually.
• Don’t divide your practice session into long blocks, one for each passage.
• Instead, divide your practice session into short intervals where you select a passage at random to practice. Make the intervals short enough that you can revisit passages multiple times during the practice session, so your practice is truly interleaved. Breaking up your practice in this way has the additional benefit of keeping your focused attention on goal-directed skill-building, for better deliberate practice.
• Make sure you don’t just practice these sections in isolation, of course! Practice the transitions, and practice starting in random places.
• If you practice for hours at a time, consider breaking that up into smaller sessions—and make sure you visit the same pieces of music in each session.