Why Practice Makes Perfect

1 WHY PRACTICE MAKES PERFECT

If you've ever listened to Arthur Rubinstein tear through a complicated passage of Chopin or Schumann [or a speed contestant at the NSRA or CCRA conventions rip through technical 2-voice testimony at 280 words a minute], you've probably wondered how his fingers can move that fast. With good reason. Consider that in Chopin's presto from the B-flat Minor Sonata, Rubinstein puts away the 1,760 notes in one minute 16 seconds flat, a speed of 23 notes per second.

[A count of the recent NSRA speed contest reveals that one of the top three contestants executed 1.3 strokes per second.]

And that's just the beginning. The striking of each note requires the controlled motion of all three joints in each finger, including distinct flexing, extending, and lateral movements. Meanwhile, for each finger that moves into playing position, at least two fingers must get out of the way. According to the late physiologist Homer W. Smith of New York University, a performance of 20 to 30 notes per second may actually involve as many as 600 individual actions per second.

"And the number may be much higher," says Frank R. Wilson, neurologist with the Performing Artists Program at the University of California, San Francisco, and author of Tone Deaf and All Thumbs? Consider that so many quick and complex maneuvers combine to yield an artistic performance -- all of it done almost without a conscious thought -- and you have a sense of the achievement of what Wilson calls "the small-muscle athlete."

How do mind and muscle accomplish such a feat? The skilled movements of an Arthur Rubinstein are simply too fast to be governed by the system that oversees most voluntary movements, 2 such as the act of turning to this page. That movement began with your brain commanding certain muscles to set your arm and hand in motion. Immediately signals from your eyes and from sensory nerves in your muscles began to feed information back to the brain on how well you were doing, perhaps reporting that your hand was heading a little wide of the mark. The brain then would have ordered a mid-course correction, adjusting the path up or down, left or right. Your reach was gradual enough that there was plenty of time for repeated checks and adjustments.

But you'd never be able to rip through Chopin's presto at 23 notes per second using such a deliberate process. "That's just too many movements performed too quickly to be explained by the traditional model of actions continuously guided by sensory feedback," says Wilson.

BALLISTIC MOVEMENTS

Instead, the body creates a different kind of movement -- what neurophysiologists call a ballistic movement. As the name suggests, a ballistic movement is like the firing of a gun: Once the trigger is pulled, the bullet will go only where it was aimed.

Ballistic movements are very economical. All they require is the initial electrical burst, which lasts just long enough to get the muscles moving at the right speed and in the right direction. The impulse is usually over by the time the muscle is only halfway through its motion. That leaves the arm (or any moving limb) to continue on its set course until it runs out of steam or into some physical resistance. It also leaves the brain free to worry about the next movement -- which is probably one reason ballistic movements can occur in as few as 80 milliseconds, according to some estimates, compared to a minimum of about 400 milliseconds for actions controlled by continuous 3 feedback signals.

But because a ballistic movement relies on only one signal, its trajectory, force, and speed have to be just right -- and carefully worked out in advance. And that, as your third-grade music teacher (or theory class teacher) probably told you, takes practice.

"Gradually through practice unnecessary movements are eliminated."

The role of practice is the same whether you're sharpening your tennis swing or learning a Bach fugue (or trying to reach the next speed plateau): to work out the best estimate of the initial ballistic impulse needed to carry an arm, hand, or finger through to its ultimate destination. Part of practice is homing in on exactly which muscles are needed to perform a given movement. "In the early stages of practicing a skilled movement, we begin by contracting many more muscles than we really need," explains Emilio Bizzi, a neurophysiologist at MIT. That probably accounts for the stumbling stiffness of the beginning typist and the novice knitter. "Gradually, however, through practice," says Bizzi, "unnecessary movements are eliminated."

So, too, is the need for continuous feedback. We begin by practicing slowly, which gives the brain plenty of time to receive and process sensory signals, to let it check how well we're doing. The more we practice, the more accurate we get. According to Bizzi, feedback is essentially an error signal, a measure of how far the actual movement is from the brain's original intent. "So as performance becomes more optimal through practice, the error signal grows smaller and smaller."

Once a ballistic movement's precise force and trajectory 4 have been worked out, they can be executed without continuous checking. Wilson describes experiments in which researchers taught monkeys to perform a series of actions -- pointing quickly to a target light, for example -- and then severed connections to sensory nerves in their limbs. The monkeys continued to point with virtually the same accuracy. "That tells us practice produces something like a computer subroutine, a set of information for the execution of skilled movements that can be run apart from feedback."

Some researchers believe skilled actions may be stored as chunks of instructions -- all the information to execute a measure of music, let's say -- that can be called up and executed by a single command.

Studies of accomplished typists offer some support for this theory of chunking. The reasoning goes that if the brain actually controlled typing letter by letter, a given letter would always be executed at roughly the same speed. In reality the speed varies widely. In one study a typist executed the letter o in 370 milliseconds when it appeared in the word 'brown,' but in only 130 milliseconds in the word 'dog.'

What barely varied was the total time for a sequence of keystrokes that made up a given word -- suggesting that the keystrokes for that word may be chunked together and under the control of a single program. The skilled movements of a musician, dancer, or karate master could be stored in similarly coherent chunks.

DEEP RELAXATION

Getting ballistic trajectories down just right is one important part of practice. But Wilson raises another, more surprising role. Although no one knows which parts of the brain 5 control ballistic movements, studies suggest that the cerebellum, long associated with voluntary movement, appears to have a lot to do with it. "And that's interesting because the cerebellum is primarily an inhibitory organ," says Wilson. The firing of nerve cells and the movement of muscles are determined by combinations of On and Off signals (again, similar to the computer). The cerebellum exerts its control primarily by providing the Off signals. "It could well be that the cerebellum's role is to orchestrate the full relaxation that must precede muscle contraction during ballistic movements," says Wilson. So through practice, the brain works out the proper sequence of these Off signals just as precisely as the On impulses that get things moving.

Wilson likens the process to a fire engine equipped with a device to control stoplights as it roars through intersections. "The cerebellum may be clearing intersections, taking over nerve synapses, making sure everything else gets out of the way in order to allow those extremely rapid movements to take place."

That may account for the state of deep relaxation that many musicians experience during performance. For if practice is a special kind of memorizing based on repetition and refinement, performance becomes a special kind of forgetting. "Ultimately the musician must relinquish the illusion of moment-to-moment control," says Wilson, "trusting the program to remember exactly how each finger must move. The musician becomes aware only of the feeling, the emotion in the music."

That's the moment when the musician leaps from mere technician to artist -- or the reporter gets that "impossible" witness -- and practice becomes perfection.