Practice and myelin
Sunday, April 15th, 2007
NYT mag article on tennis kids :
myelin is a sausage-shaped layer of dense fat that wraps around the nerve fibers ‘ and that its seeming dullness is, in fact, exactly the point. Myelin works the same way that rubber insulation works on a wire, keeping the signal strong by preventing electrical impulses from leaking out. This myelin sheath is, basically, electrical tape, which is one reason that myelin, along with its associated cells, was classified as glia (Greek for “glue”). Its very inertness is why the first brain researchers named their new science after the neuron instead of its insulation. They were correct to do so: neurons can indeed explain almost every class of mental phenomenon’memory, emotion, muscle control, sensory perception and so on. But there’s one question neurons can’t explain: why does it take so long to learn complex skills?
“Everything neurons do, they do pretty quickly; it happens with the flick of a switch,” Fields said. “But flicking switches is not how we learn a lot of things. Getting good at piano or chess or baseball takes a lot of time, and that’s what myelin is good at.”
To the surprise of many neurologists, it turns out this electrical tape is quietly interacting with the neurons. Through a mechanism that Fields and his research team described in a 2006 paper in the journal Neuron, the little sausages of myelin get thicker when the nerve is repeatedly stimulated. The thicker the myelin gets, the better it insulates and the faster and more accurately the signals travel. As Fields puts it, “The signals have to travel at the right speed, arrive at the right time, and myelination is the brain’s way of controlling that speed.” 2
It adds up to a two-part dynamic that is elegant enough to please Darwin himself: myelin controls the impulse speed, and impulse speed is crucial. The better we can control it, the better we can control the timing of our thoughts and movements, whether we’re running, reading, singing or, perhaps more to the point, hitting a wicked topspin backhand.
Every talent, according to Ericsson, is the result of a single process: deliberate practice, which he defines as “individuals engaging in a practice activity (typically designed by teachers) with full concentration on improving some aspect of their performance.” In a moment of towering simplification, “The Handbook” distills its lesson to a formula known as the Power Law of Learning: T = a P-b . (Don’t ask.) A slightly more useful translation: Deliberate practice means working on technique, seeking constant critical feedback and focusing ruthlessly on improving weaknesses.
“It feels like you’re constantly stretching yourself into an uncomfortable area beyond what you can quite do,” Ericsson told me. It’s hard to sustain deliberate practice for long periods of time, which may help explain why players like Jimmy Connors succeeded with seemingly paltry amounts of practice while their competitors were hitting thousands of balls each day. As the tennis commentator Mary Carillo told me, “He barely practiced an hour a day, but it was the most intense hour of your life.”
Ericsson also discusses the Ten-Year Rule, an intriguing finding dating to 1899, which shows that even the most talented individual requires a decade of committed practice before reaching world-class level. (Even a prodigy like the chess player Bobby Fischer put in nine hard years before achieving his grandmaster status at age 16.) While this rule is often used to backdate the ideal start of training (in tennis, girls peak physically at around 17, so they ought to start by 7; boys peak later, so 9 is O.K.), the Ten-Year Rule has more universal implications. Namely, it implies that all skills are built using the same fundamental mechanism, and that the mechanism makes physiological demands from which no one is exempt.
One fact missing from the article but dropped into a short film segment accompanying the article: myelination ends in your early twenties.