Abstract
A new theory, called the neuromotor noise theory of stress and human performance, is proposed to account for (in)effective strategies in space oriented behavior. According to the theory, goal directed movement is the outcome of an optimization process by which noisy neuromotor recruitment signals to the muscles are filtered by means of strategic levels of limb stiffness, to arrive at an adequate signal-to-noise ratio for the resulting limb displacement trajectory. Neuromotor noise is thought to be the joint outcome of stochastic muscle force recruitment processes, the spreading of noise from concurrent processes in the brain, and interruptions of the motor output by servo control. The filtering capacities of the moving limb are assumed to be set through the application of cocontraction of agonist and antagonist muscles and by varying friction forces with the working surface. An example of the latter is the enhancement of pen pressure in graphic tasks when the difficulty of the task is increased. In an experiment with a graphical aiming task subjects made pen movements to targets varying in width and distance to test the prediction that time pressure and dual task load would influence error rates and movement noisiness, together resulting in biomechanical adaptations of pen pressure. The results provided clear evidence for all three predictions. In the discussion section the implications of the theory for understanding the etiology of Work Related Upper Extremity Disorders (WRUEDs) is further demonstrated through a comparison of pen pressure data of a group of WRUED patients (n = 11) and controls (n = 24).
