Final answer:
A postreinforcement pause occurs in a fixed interval schedule, but only at the end of the interval.
Step-by-step explanation:
In a fixed interval schedule, there is a postreinforcement pause that occurs after the reinforcement is delivered, but only at the end of the interval. This means that there is a period of time after the reinforcement is received where there is a decrease in the response rate. For example, in a fixed interval schedule where a student is rewarded every 30 minutes for studying, there will likely be a pause in studying right after the 30-minute mark, before the next reinforcement is available.