Final answer:
In operant conditioning, 'Functional relation' is not considered a principle of behavior. Instead, principles include reinforcement, punishment, and extinction which influence the likelihood of a behavior occurring.
Step-by-step explanation:
The principle that is NOT a part of the principles of behavior as it pertains to operant conditioning is b. Functional relation. Operant conditioning involves reinforcing or punishing a voluntary behavior to influence the likelihood of its occurrence. Reinforcement, whether positive or negative, aims to increase the likelihood of a behavior. Punishment, also either positive or negative, aims to decrease the likelihood of a behavior. Extinction is the process by which a behavior ceases to be displayed after consistently not being reinforced. On the other hand, a functional relation, as it might relate to the mentioned concepts, is not typically listed among the primary principles of operant conditioning.