Final answer:
B. F. Skinner was referred to as a radical behaviorist because he believed that cognition didn't matter and that the mind should not be studied. He focused on studying behavior and believed that even complex mental functions are nothing more than stimulus-outcome associations.
Step-by-step explanation:
B. F. Skinner was referred to as a radical behaviorist because he developed a staunch form of behaviorism that focused exclusively on studying behavior rather than cognition. Skinner believed that even complex mental functions like human language are nothing more than stimulus-outcome associations. He considered the mind a 'black box' and argued that it should not be studied.