Dec. 20, 2006 -- Practicing your golf swing may make it better, but it'll never make it perfect, because the brain is wired for inconsistency.
The study found variations in monkeys' brain activity in the planning stages before they performed the same task over and over again -- and that those variations were associated with inconsistencies in their performance.
"The main reason you can't move the same way each and every time, such as swinging a golf club, is that your brain can't plan the swing the same way each time," says researcher Krishna Shenoy, assistant professor of electrical engineering at Stanford University, in a news release.
In the study, published in Neuron, researchers trained monkeys two simple reaching tasks: to reach and touch a green spot slowly, and to reach and touch a red spot quickly.
After monitoring thousands of attempts, they found the monkeys rarely reached with the exact same speed for either spot, and that about half the inconsistencies in the monkeys' performance was in their heads rather than their muscles.
Specifically, the study showed changes in neural activity for planning a movement was predictive of the variations in reach speed.
The researchers say inconsistencies in how the brain plans for each movement may have an evolutionary reason.
"The nervous system was not designed to do the same thing over and over again," says researcher Mark Churchland, a postdoctoral student at Stanford, in the release.
"The nervous system was designed to be flexible," Churchland says. "You typically find yourself doing things you've never done before."
Of course practice can reduce the variation in the mind's and body's ability.
But, researchers say, it can't change the variable way the mind plans motion.