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.