FOOD DELIVERIES DURING PAUSE ON FIXED-INTERVAL SCHEDULES

Pigeons were trained on fixed interval [FI] schedules of food delivery. In experiments I and II, the FI was initiated by the previous FI reinforcer; in experiment III, the FI was initiated by the 1st key peck following the preceding FI reinforcer (a chain fixed-ratio one, FI schedule). During the postreinforcement pause, variable-time schedules delivered food independent of any specific response. Rate of food delivery during the pause had only small effects on pause duration in experiments I and II. In experiment III, pause duration increased systematically with the rate of food delivery during the pause. These data suggest that the momentary proximity to reinforcement delivered via the FI schedule exerts potent control over pause termination. Additional analysis revealed that pause termination was unaffected by the intermittent delivery of food during the pause. Such data suggest that the temporal control by FI schedules is highly resistant to interference.