What Is a Variable Interval Schedule?
A variable interval schedule is a principle in operant conditioning where the reinforcement for a certain behavior comes at random times, or variable intervals. This is an example of intermittent reinforcement, which occurs when only some instances of a certain behavior are rewarded (and not all of them).
For a variable interval schedule, the director of the experiment would choose a certain time frame and reward the behavior only when it occurs after that time has lapsed, changing the time frame every time. This means that the reinforcement schedule is unpredictable to the subject of the experiment and the behavior that is reinforced is more likely to continue for a longer period after reinforcement has stopped.