A variable ratio schedule is a type of reinforcement schedule used in behavioral psychology. In this system, a response is reinforced after an unpredictable number of actions. This means that the reward is not given every time the behavior occurs, making it more difficult to predict when the next reward will come. This schedule is often seen in gambling, such as with slot machines, where players receive payouts after an uncertain number of spins. The unpredictability of the reward encourages continued engagement, as individuals are motivated by the possibility of a win, leading to persistent behavior.