What is a variable interval schedule?

A variable interval schedule is characterized by the timing of reinforcement being unpredictable but occurring at an average rate. In this case, rewards are provided after varying time intervals, which means that the individual cannot predict precisely when the next reward will come, making the behavior more resistant to extinction. This unpredictability keeps the individual engaged in the behavior, as they remain hopeful that they could receive a reward at any moment.

In contrast, other schedules mentioned in the options have different characteristics. For example, a schedule where a reward follows a specific number of responses involves a fixed amount of effort or responses before reinforcement is given. A schedule providing a reward every time a behavior is exhibited represents continuous reinforcement, which is different from variable intervals, as it establishes a clear and consistent pattern of rewards. Lastly, a schedule providing rewards for certain behaviors instead pertains to the differentiation of behaviors rather than the timing of reinforcement. Thus, the defining aspect of a variable interval schedule is its unpredictable nature concerning time intervals between reinforcements.