An adjusting avoidance schedule.

A shock-avoidance schedule is described in which the animal accumulated 5 sec of safe time whenever it pressed a lever. With this schedule, the animal was not differentially reinforced for long pauses between responses; and, consistent with this property of the schedule, the probability that the animal would press the lever was not related in any regular way to the amount of time that had elapsed since its preceding lever press. Other features of the performance are also described. If the animal was given a warning stimulus whenever it came within 5 sec of a shock, it tended to spend more time in the close temporal vicinity of the shock and less time at the maximum temporal distance from shock.