This article examines the potential influence of the work of two psychologists—G. F. Stout and James Sully—on J. M. Keynes’s economic theory. It does so by providing an analysis of aspects of the notes that Keynes made while studying for the Civil Service entrance examination in psychology in 1905-6, and how they related to the source materials on which they were based. It argues that Keynes did “absorb” some of the ideas of these two psychologists while studying for the Civil Service examination, and that they then reappeared in modified form in his later economic writings. Consequently, psychological ideas (and also ideas about physiological evolution) are more important in Keynes’s economic theory than is sometimes recognized.