The next time you putt 100 balls at the range, because you know the practice will improve your short game, know this: it probably won't.
Why? Because it's not just practice that makes perfect. It's practicing intelligently that improves performance.
Such are the conclusions of a study published this week in the journal Nature Neuroscience by a group of neuroscientists at the University of Southern California and the University of California, Los Angeles. The authors compared the performance of people who tried to hone a skill through "constant practice" that is, the rote repetition of a task, like taking 100 serves across the net and those who underwent "variable practice," in which you work on a mix of skills during a training session. An example of variable practice: taking a serve, followed by a backhand, then mixing in a drop shot and forehand.
In the study, participants were asked to mimic a 60-degree forearm movement that was represented as a wavy line on a computer screen. They moved their forearms while holding a lever, and their results were superimposed onto the target line after each movement. The more the movement mimicked the target, the better the performance. Those who repeated the movement 120 times (constant practice) performed just as well during the practice session as those who did the 60-degree movement 60 times, and a 30-degree, 45-degree, and 75-degree movement 20 times each, in a jumbled order (variable practice).
Of course, you can knock the cover off the ball in practice. But it's the game that counts. About 24 hours after the volunteers finished their practice sessions, the authors tested their performance again. This time, they found that those in the variable-practice group performed better on the 60-degree movement than those who trained with rote repetition. The suggestion is that during the key postpractice period when the brain processes and retains the lessons it has just learned known by neuroscientists as the consolidation phase mixing tasks pays off.
Why? Psychologists have long known that variable practice of motor skills leads to better retention. The current study, however, offers a neurological explanation for this phenomenon. Immediately after the practice sessions, some study participants (from both the variable- and constant-practice groups) received transcranial magnetic stimulation (TMS), a procedure that temporarily interferes with brain activity through the application of electric coils on the primary motor cortex, the area of the brain associated with simple motor learning. "We kind of messed with the brain after practice," says Shailesh Kantak, a former Ph.D. student in the Division of Biokinesiology and Physical Therapy at USC and the lead author of the study. Another group received TMS on the dorsolateral prefrontal cortex, a brain region associated with higher-level cognitive functions like problem-solving and planning.
The variable-practice participants who received TMS to the prefrontal cortex did not perform as well as those who received TMS to the primary motor cortex, or the control group. Since interference, and a temporary "slowing down," of the prefrontal cortex negatively affected performance of the variable-practice subset, the authors were able to conclude that variable practice engages this problem-solving and planning area of the brain. The engagement of this more powerful part of the brain, in turn, explains why variable practice improves retention levels the next day.
Similarly, people in the constant-practice group who received TMS to the primary motor cortex performed worse on the next-day retest than those who received prefrontal-cortex TMS. This implies that the rote drills engage a lower part of the brain, and further explains why constant practice is less effective for next-day retention of motor skills.
Tedium is bad for the brain. "In constant practice, people just go into auto mode, and are just like, 'Whatever,'" says Kantak, who is now a postdoctoral fellow at the Rehabilitation Institute of Chicago. "In variable practice, your brain is more actively engaged and actively processing information, which allows it to hold information better. Our brain is like a muscle, and when it gets a good workout, it gets stronger."
So go ahead, take those 100 serves. But don't forget to work on your drop shots. Your brain will thank you for it. And your opponent, perhaps, will rue the day you mixed up your workout.