Control dynamics and timing a discrete motor response

Altering the resistive dynamics of a handle moved 60 cm. to fill a 2-sec. interval manipulated the proprioceptive feedback (PFB) from the response. Spelling aloud 2-, 3-, and 4-letter words during the motor response prevented overt counting. 84 11-14 year old boys were given immediate KR, the lapsed time for the motor response, for 50 or 60 trials according to the design. Only the condition reducing time varying PFB to a minimum, no movement and no spelling, prevented accurate timing of the responses, but above the minimal level, accuracy, consistency and rapidity of learning was increased by the addition of large resistances varying with velocity and acceleration.