Brain Waves

Examining perception, sound and hearing, language and learning.

4 Rules For Hanging On to What You Learn

One researcher's search for the perfect amount of practice

My children were given math homework this summer in hopes of avoiding the infamous “brain drain.” That's the tendency, between June and September, to lose a surprising amount of what they learned the previous school year. The other day, I finally sat down with the boys and made them start the assignments. And sure enough, after just a few weeks of vacation, they already seemed to have forgotten a lot of what they learned last year.

Fortunately for them, instead of freaking out, I was intrigued.

As it happens, one reason it took us a while to get to the math was that I had been away at a conference where I heard an interesting talk by Beverly Wright.

Wright, an experimental psychologist at Northwestern University, does not study brain drain or even anything that deals with academics directly. She studies a far more elemental type of learning, asking subjects to master very basic tasks of auditory perception such as identifying which of two tones is higher in pitch or longer in duration.

Her idea is—and the data suggests—that such simple abilities and the improvement in them possible with training might tell us something that generalizes to more complicated tasks, auditory and otherwise. The research could tell us something about the learning process itself and maybe even someday tell us what it might take to remember middle school math.

Other researchers agree. “The principles underlying simple and complex tasks are similar,” says Merav Ahissar, a neuroscientist who studies the relationship between perception and cognition at Hebrew University of Jerusalem, adding that questions like how fast and effectively skills are learned apply to both kinds of tasks.

Wright’s laboratory has arrived at four tentative principles of auditory learning. They seem straightforward but actually run counter to some prevailing ideas about training, such as the belief that every practice session counts.

The first is “Just do it,” and it holds that you have to practice the particular skill you want to learn. In Wright’s studies, subjects who practiced identifying pitch got better at identifying pitch but no better at judging the length of a tone. Their work on one listening skill did not transfer to another. 

To hold on to a skill across days—what good is mastering something on Monday if you’ve lost it on Tuesday—requires the second principle: “Practice, practice, practice.” Perhaps more than one might expect. Wright had one set of listeners train on discriminating between pitches 360 times per day for approximately six days. Another group practiced 900 times per day for the same period. The first set of listeners didn’t improve, but the second set did. Even when listeners practiced the same number of times overall, the critical factor in whether they got any better was how many times they practiced per day.

That said, once a person has mastered a skill, principle number three kicks in: “Enough is enough.” In other words, the perfect amount of practice isn't necessarily always 10,000 hours. While it took 900 trials to learn to discriminate between pitches, listeners who were asked to decide which tone was longer showed improvement after 360 times and were just as good at it as those who practiced 900 times. In other words, for this task, the additional 540 trials were what researchers call “inefficient” and what the rest of us call “a waste of time.”

So what’s the magic number? Where is the threshold between cementing what’s been learned and wasting time? Unfortunately, we don’t know—yet. As Wright’s work makes clear, different tasks have different thresholds. But that's as much as she knows so far. Undiscouraged, she argues that it wouldn’t take much to establish guidelines for certain tasks, and an obvious application would be in rehabilitation. “What is rehabilitation after all but learning,” says Wright. “Before people didn’t know you needed enough training per day. They’d dabble here and there.”

Nine-hundred practice sessions is a lot, however. That’s why Wright’s fourth principle is encouraging. It says that “Two wrongs make a right.” While alternating between learning two skills can wipe out progress in both, and you can’t learn from passive exposure alone, you can learn if you alternate practice with passive exposure to the same thing. Perhaps that explains why I soaked up far more French when I was both studying the language and visiting France than when I did either thing in isolation. Indeed, Wright mentions understanding foreign accents as a task directly related to her work.

The importance of practice, Wright hypothesizes, is that it “somehow highlights the neural circuitry involved . . . placing that circuitry into a state in which it can be modified.” With continued exposure—in the right time period—the changes to the highlighted circuits become permanent as if someone wrote over them in ink. The new network results in a new and improved brain--at least for the skill being trained.

You can think of learning like water accumulating in a bucket, says Wright. “You’re waiting for that bucket to be filled. If it isn’t filled [in the right amount of time], you could lose everything in it and have to start over.”

It’s too soon to say for sure what Wright’s principles mean for my soon-to-be 6th grader’s ability to remember how to multiply fractions except that I know we don’t want to have to start over. Mastering facts and figures—known as declarative learning—is certainly a complex task compared to the perceptual skills that Wright studies. Yet both kinds of learning require changes in the brain. And her work makes me think there’s no harm in my son and I trying to find the sweet spot between practicing enough fractions to know them cold and wasting our time when we could go swimming instead.

 

Lydia Denworth is a New York based science writer. Her most recent book is I Can Hear You Whisper.

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