N the context of operant conditioning, the labels "positive" and "negative" are best viewed as mathematical labels like "increase" or "decrease" and not value judgments like "good" or "bad." This is related to what key principle of B. F. Skinner?

Psychologists should focus on observable behaviors only                                                                                                          

Explanation:

B. F. Skinner is best known for his contribution to psychology by discovering the operant conditioning theory. B. F. Skinner is one of the famous behaviorists and psychologists of his time. Therefore, he used to believe that all behaviors led by an organism including human beings, animals, etc are learned and hence it can be possible for people to determine the inner characteristics based on the organism's outer behavior.

B. F. Skinner criticizes the psychoanalytic and functionalist approach to psychology and believed that every psychologist should focus more on observable behaviors rather than any inner conflicts, or unconscious mind.