What type of reinforcement schedule requires a set number of responses before delivering a reward?

The correct answer is based on the concept of reinforcement schedules, specifically the fixed ratio schedule. In a fixed ratio schedule, a reinforcement is provided after a specific number of responses have been made. For example, if a rat in a Skinner box receives a food pellet after it presses a lever five times, this is a fixed ratio schedule. This type of reinforcement leads to a high rate of responding, as the individual learns that a set number of actions will reliably yield a reward.

In contrast, a fixed interval schedule provides reinforcement after a set amount of time has passed, regardless of the number of responses made during that time. A variable ratio schedule offers reinforcement after an unpredictable number of responses, which can lead to high rates of response but is not based on a fixed number. Lastly, a variable interval schedule delivers reinforcement based on varying time intervals, again not tied to a specific number of responses. Therefore, the essence of the fixed ratio schedule is the reliance on a predetermined number of actions to receive a reward, which distinguishes it from the other options.