Anyone who has ever tried to serve a tennis ball or flip a pancake or even play a video game knows, it is hard to perform the same motion over and over again. But don’t beat yourself up —errors resulting from variability in motor function is a feature, not a bug, of our nervous system and play a critical role in learning, research suggests.
Variability in a tennis serve, for example, allows a player to see the effects of changing the toss of the ball, the swing of the racket, or the angle of the serve — all of which may lead to a better performance. But what if you’re serving ace after ace after ace? Variability in this case would not be very helpful.
If variability is good for learning but bad when you want to repeat a successful action, the brain should be able to regulate variability based on recent performance. But how?
That question was at the center of a recent study from Harvard researchers published in the journal Current Biology.
Using an enormous amount of data from about 3 million rat trials, the researchers found that rats regulate their motor variability based on the outcomes of the most recent 10 to 15 attempts at a task. If the previous trials have gone poorly, the rats increased their amount of variability — employing a try-anything approach. However, if the previous trials have gone well, the rats limited their variability, proving that rats too subscribe to the old adage “if it ain’t broke, don’t fix it.”
But is this the best strategy?
“By using simulations to determine what the optimal variability regulation strategy should be, we found that it was very similar to the one used by rats,” said Ashesh Dhawale, a postdoctoral fellow in the Department of Organismic and Evolutionary Biology and first author of the study. “We also found that the degree to which individual rats regulated variability could predict how well they learned and performed on the motor task. This means that regulating variability based on performance is important for doing well both in the short and the long term.”