The scientific name for the small differences between our expectations of an action and the reality of that action is "prediction errors."
The researchers note that when people perform a task - such as opening a door - their brains make comparisons of how the door moved with how they expected the door to move. This information is calculated in a way that allows the person to perform the task more efficiently next time.
The scientific name for the small differences between our expectations of an action and the reality of that action is "prediction errors." We learn prediction errors in a largely unconscious way.
To further investigate how the brain learns prediction errors, the researchers devised an experiment involving a joystick and a pair of dots on a screen.
The participants were told to guide a blue dot toward a red dot on the screen using the joystick. However, the participants were unable to see the joystick that they were holding, and the blue dot could also be programmed by the researchers to move in an off-kilter way.
To overcome the off-kilter movement of the dot, the participants were required to compensate their joystick movements accordingly. Typically, after a few attempts, they would adjust their movements to guide the blue dot to its target.
The researchers observed that the participants responded more quickly to small errors that pushed them consistently in one direction than to larger errors that were less consistent.
David Herzfeld, a graduate student in Shadmehr's laboratory who led the study, explains: "They learned to give the frequent errors more weight as learning cues, while discounting those that seemed like flukes."
Reza Shadmehr, PhD, a professor in the Department of Biomedical Engineering at Johns Hopkins, compares the experiment to his proficiency as a tennis player.
"I'm much better in my second 5 minutes of playing tennis than in my first 5 minutes," he says, "and I always assumed that was because my muscles had warmed up. But now I wonder if warming up is really a chance for our brains to re-experience error."
'Two processes happening simultaneously'
Further explaining the experience of learning a new motor task, Dr. Shadmehr says there appear to be two processes happening simultaneously. One of these is the learning of motor commands, and the other is critiquing the learning, "much the way a 'coach' behaves."
"Learning the next similar task goes faster, because the coach knows which errors are most worthy of attention. In effect, this second process leaves a memory of the errors that were experienced during the training, so the re-experience of those errors makes the learning go faster."
Daofen Chen, PhD, a program director at the National Institute of Neurological Disorders and Stroke, who co-funded the study, says that the research is a significant step toward understanding how we learn motor skills:
"The results may improve movement rehabilitation strategies for the many who have suffered strokes and other neuromotor injuries."
In the next component of the research, the team will examine which brain region is responsible for the "coaching" role in assigning different weights to various types of error.