Food-deprived rats were divided into four groups according to the equal interval and time durations of a multiple fixed-interval, fixed-time schedule (15, 30, 60, and 120 s). Fixed-time components were signaled by a tone and lever withdrawal. d-Amphetamine (0.25-4.0 mg/kg) produced similar dose-dependent reductions in the drinking and licking induced by fixed-interval and fixed-time schedules. ...
