People looking for precursors to artificial intelligence often point to science fiction by authors like Isaac Asimov or thought experiments like the Turing test. But an equally important, if surprising and less appreciated, forerunner is Skinner’s research with pigeons in the middle of the 20th century. When Sutton began working in AI, he felt as if he had a “secret weapon,” he told me: He had studied psychology as an undergrad. Skinner started his missile research with crows but switched to pigeons when the brainy black birds proved intractable. In the middle of the 20th century, Skinner took Pavlov’s principles of conditioning and extended them from an animal’s involuntary reflexes to its overall behavior.