The Premack principle states that a person will perform a less preferred activity (low probability behavior) to gain access to a more preferred activity (high probability behavior). A less preferred activity is defined as one in which the individual is unlikely to choose to do on their own, thus developing the term low probability behavior. A more preferred activity is an activity that the individual would likely choose to engage in on their own, a high probability behavior.
The Premack Principle states that a behavior an individual chooses to do on his own will reinforce a less preferred behavior. Professionals commonly use this intervention to reduce demand refusal, but there are many practical applications beyond this use.