If one activity occurs more often than another, the opportunity to do the most frequent activity will reinforce the less frequent activity.

2) A higher frequency operant will reinforce a lower frequency behavior.

3) The principle that one can use the opportunity to do something that one is likely to do reinforce doing something that one is not as likely to do. For example, one can use the opportunity to play ball to reinforce a person to doing something he or she is less likely to do, such as washing dishes.

4) A principle that states that contingent access to high-frequency behaviours ("preferred" activities) serves as a reinforcer for the performance of low-frequency behaviors. See also Response deprivation hypothesis.

5) The relativity of reinforcers and punishers. See REINFORCEMENT.