CONTROL OF OPERANT RESPONSE FORCE

Differences in motor-control strategies (feedback or feedforward) enga ged by rats to produce operant response force were investigated under 2 conditions of external feedback. In the immediate condition, liquid sucrose reinforcers were delivered as soon as each forelimb response m et the force requirement, whereas under the terminal condition, reinfo rcers were delivered at response termination. When feedback control of response force was precluded by delivering reinforcers at response te rmination, force was adjusted by modulation of the rate of rise of for ce. However, under immediate reinforcer delivery, response force was c ontrolled by adjustments of time to peak force. Such adjustments of re sponse time to meet response requirements of increasing difficulty are consonant with expressions of the speed-accuracy tradeoff commonly ob served in studies of human motor control.