Burrhus Frederic Skinner (1904 – 1990). American psychologist, behaviourist, author, inventor, and social philosopher. He was a professor of psychology at Harvard University from 1958 until his retirement in 1974.Considering free will to be an illusion, Skinner saw human action as dependent on consequences of previous actions, a theory he would articulate as the principle of reinforcement: If the consequences to an action 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 developed behaviour analysis, especially the philosophy of radical behaviourism, and founded the experimental analysis of behaviour, a school of experimental research psychology. He also used operant conditioning to strengthen behaviour, considering the rate of response to be the most effective measure of response strength. To study operant conditioning, he invented the operant conditioning chamber (aka the Skinner Box), and to measure rate he invented the cumulative recorder. Using these tools, he and Charles Ferster produced Skinner's most influential experimental work, outlined in their book Schedules of Reinforcement (1957).