Entropy compensation in human motor adaptation.

This experiment examined the changes in entropy of the coordination of isometric force output under different levels of task demands and feedback from the environment. The goal of the study was to examine the hypothesis that human motor adaptation can be characterized as a process of entropy conservation that is reflected in the compensation of entropy between the task, organism (motor output), and environment. Healthy young individuals produced two-finger force output to a total constant level under different task (error tolerance) and environmental (feedback frequency) conditions. Information entropy of the coordination dynamics (relative phase) of the motor output was made conditional on the idealized situation of human movement, for which the goal is always achieved. Conditional entropy of the motor output decreased as the error tolerance and feedback frequency were decreased. Thus, as the likelihood of meeting the task demands is decreased (increased task entropy) and/or the amount of information from the environment is reduced (increased environmental entropy), the subjects employed fewer coordination patterns in the force output to achieve the goal.