THERMODYNAMIC STUDY OF MOTOR BEHAVIOR OPTIMIZATION

Our work is aimed at studying the optimization of a complex motor beha viour from a global perspective. First, 'free climbing' as a sport wil l be briefly introduced while emphasizing in particular ib psychomotor aspect called 'route finding'. The basic question raised here is how does the optimization of a sensorimotoricity-environment system take p lace. The material under study is the free climber's trajectory, viewe d as the 'signature' of climbing behaviour (i.e., the spatial dimensio n). The concepts of learning, optimization, constraint, and degrees of freedom of a system will be discussed using the synergistic approach to the study of movement (Bernstein, 1967; Kelso, 1977). Measures of a trajectory's length and convex hull cad be used to define an index wh ose equation resembles that of an entropy. This index is a measure of the trajectory's overall complexity. Some important concepts related t o the thermodynamics of curves will also be discussed. The optimizatio n process will be studied by examining the changes in entropy over tim e for a set of trajectories generated during the learning of a route ( ten successive repetitions of the same climb). It will be shown that t he entropy of the trajectories decreases as learning progresses, that each level of expertise has its own characteristic entropy curve, and that for the subjects tested, the mean entropy of skilled climbers is lower than that of average climbers. Basing our analysis on the concep ts of degrees of freedom and constraint equations, an attempt is made to relate trajectory entropy to system entropy. Based on the postulate that trajectory entropy is equal to the difference in entropy between the unconstrained and constrained system, a model of motor optimizati on is proposed. This model is illustrated by an entropy graph reflecti ng a dynamic release process. In the light of our results, two opposin g views will be examined: movement construction vs. movement emergence .