fixed-interval schedule

n. In operant conditioning, a schedule of reinforcement in which a target behavior is reinforced the first time it is emitted after a predetermined time interval. If the time periods in a fixed-interval schedule are more than a few seconds, organisms tend to develop a pattern of responding in which there are few or no responses at the start of the interval and more toward the end of the interval. This type of schedule leads to behaviors that are more resistant to extinction than are those conditioned through continuous reinforcement.