Positive Behavior Intervention and Support (PBIS) is based on external motivation. It asks adults to find some behavior that they wish young people to do and then rewards them for doing it. The theory is that, if a reward is given, the person will repeat what the addult desires. In essence, the purpose is to use rewards to control behavior.
The concept of behaviorism originated with Ivan Pavlov and is referred to as classical conditioning. Ring a bell and give a dog food. Soon you can just ring a bell and the dog will salivate. Pavlov did not experiment with a cat. Cats are much more independent. B.F. Skinner, the famed former psychologist, used this approach to train pigeons and rodents and then extrapolated that the idea would work with humans.
Tom Sawyer was a more successful psychologist. Tom Sawyer was able to get many other boys to whitewash Aunt Polly’s fence AND pay for the privilege. This is something that Positive Behavioral Interventions and Supports (PBIS)—an external motivational approach—is incapable of accomplishing.
A much more effective approach is to have young people behave responsibly because it will be in their own best interest, rather than to receive some external prize. An example of this approach can be seen at the Raise Responsibility System.