What happens in a Variable Interval (VI) schedule?

In a Variable Interval (VI) schedule, the reward is given after an interval of time that varies unpredictably. This means that the amount of time that must pass before a reward can be earned is not constant and can change from one instance to the next. This unpredictability tends to result in a steady rate of responding because the learner knows that a response made at any time may eventually lead to a reward, but they cannot predict when it will happen.

This method of reinforcement is effective because it encourages continuous and consistent behavior; the learner is motivated to keep responding since they know that rewards can come at any time interval. This setup is often used in animal training as well as in human behavioral scenarios, such as slot machines in casinos, where the rewards are not guaranteed at any specific time, prompting continuous engagement.

In contrast, the other options present different reinforcement scenarios that do not accurately describe a VI schedule. For instance, a fixed time for a reward would characterize a Fixed Interval (FI) schedule, where the time intervals remain consistent. Similarly, rewards at fixed intervals point towards a fixed schedule rather than the variability described in a VI schedule. The absence of rewards for responses aligns more closely with extinction rather than a reinforcement schedule.