Chapter 4 introduces the twentieth century’s most radical behaviorist: Burrhus Frederic Skinner. “We always called him Fred,” said Mrs. Gribbin, who apparently knew him well, explaining that his was a radical behaviorism not because he campaigned vigorously against established psychological orthodoxies, but because Skinner sought to get at the very roots of the discipline: The word radical has to do with the basic, fundamental nature of a thing. Skinner believed that to be a truly reliable science, psychology had to abandon its preoccupation with private mental events and concentrate instead on public events such as observable behaviors and their consequences. The chapter presents a detailed explanation of Skinner’s operant conditioning accompanied by illustrations of how Skinnerian findings relating to different types of reinforcers, schedules of reinforcement, aversive behavioral contingencies such as negative reinforcement and punishment, shaping, chaining, generalization, and discrimination are being applied in business, education, and day-to-day life. Mrs. Gribbin points out that Skinner is second only to Freud in terms of current recognition as a psychologist.