Burrhus Frederic Skinner (March 20, 1904 – August 18, 1990), commonly known as B. F. Skinner, was an American psychologist, behaviorist, author, inventor, and social philosopher. He was the Edgar Pierce Professor of Psychology at Harvard University from 1958 until his retirement in 1974.Skinner considered free will an illusion and human action dependent on consequences of previous actions. If the consequences are bad, there is a high chance the action will not be repeated; if the consequences are good, the probability of the action being repeated becomes stronger. Skinner called this the principle of reinforcement.To strengthen behavior, Skinner used operant conditioning, and he considered the rate of response to be the most effective measure of response strength. To study operant conditioning, he invented the operant conditioning chamber, also known as the Skinner Box, and to measure rate he invented the cumulative recorder. Using these tools, he and C. B. Ferster produced his most influential experimental work, which appeared in their book Schedules of Reinforcement (1957).Skinner developed behavior analysis, the philosophy of that science he called radical behaviorism, and founded a school of experimental research psychology—the experimental analysis of behavior. He imagined the application of his ideas to the design of a human community in his utopian novel, Walden Two, and his analysis of human behavior culminated in his work, Verbal Behavior.