Which intermittent reinforcement schedule delivers reinforcement after an unpredictable number of responses?

The appropriate choice is based on how reinforcement schedules are structured and their effectiveness in promoting behavior. The variable ratio schedule delivers reinforcement after an unpredictable number of responses, meaning that the number of responses required for reinforcement can change from one instance to the next.

This unpredictability creates a high and consistent rate of response, as the individual never knows when the next reinforcement will occur. This is why gambling, for instance, is so compelling; a player could win after any number of attempts, encouraging them to keep participating.

The variable ratio schedule is often considered one of the most effective reinforcement schedules for maintaining behavior over time, as it creates an element of surprise and excitement. In contrast, fixed schedules—whether ratio or interval—provide reinforcement after a set number of responses or after fixed time intervals, which do not foster the same level of response rate and engagement.