Final answer:
B. F. Skinner was the American psychologist who championed the use of behavioral conditioning to alter human behavior and society. He was a key figure in behaviorism, which emphasized the influence of reinforcement and punishment in learning.
Step-by-step explanation:
The American psychologist who advocated behavioral conditioning on a mass scale to reshape human behavior and culture was B. F. Skinner. Skinner's work on operant conditioning emphasized the role of reinforcement and punishment in shaping behavior. Through the use of devices like the Skinner box, he was able to conduct experiments that contributed significantly to our understanding of learning behavior. Behaviorism, as a school of thought, focused on observable behavior as the main subject of psychology, an approach also promoted by John B. Watson, often regarded as the father of behaviorism. Skinner's ideas have influenced various methodologies of behavioral modification and are still applied in areas such as education, mental health, and organizational management despite the rise of cognitive psychology, which began shifting focus back to internal mental processes during the cognitive revolution.