In 1949, he accepted an offer to join the US Air Force organization that became the Air Force Personnel and Training Research Center, where he was research director of the Perceptual and Motor Skills Laboratory. In 1958, he returned to academia as professor at Princeton University, where his research shifted focus to the learning of problem solving and the learning of mathematics. In 1962, he joined the American Institutes for Research, where he wrote his first book, The Conditions of Learning.