What characterizes a Variable Duration (VD) reinforcement schedule?

A Variable Duration (VD) reinforcement schedule is characterized by the requirement that behavior must be maintained for an average time period that varies. This means that the reinforcement is given after the dog engages in the desired behavior for a certain length of time, but the specific duration can change from one instance to the next. This variability in the timing helps to keep the dog engaged and motivated, as they do not know when they will receive the reinforcement, which can encourage them to maintain that behavior longer.

In contrast to other schedules of reinforcement, where specifics like fixed intervals or random intervals dictate when a reward is given, the variable duration schedule emphasizes an unseen standard that the dog must meet, contributing to both the unpredictability and the potential for a longer duration of the desired behavior. The concept emphasizes maintaining a specific level of behavior over time rather than simply rewarding the behavior at fixed or random moments, which leads to more sustained behaviors in the long term.