B. F. Skinner

Born in 1904, Skinner started as a would-be novelist before pivoting to psychology and landing at Harvard, where he spent most of his career. He invented the operant conditioning chamber and the cumulative recorder to track how rats and pigeons responded to reinforcement, then codified the findings with Charles Ferster in their 1957 book Schedules of Reinforcement. His 1948 novel Walden Two imagined a society engineered on behaviorist principles, and his 1958 work Verbal Behavior extended the framework to language itself. He published 21 books and 180 articles before retiring in 1974. A 2002 survey named him the most influential psychologist of the 20th century - architect of radical behaviorism, which insisted that everything we do is learned, not willed.