A general theory of learning and conditioning: Part I

Psyckometrika, March 1943, Volume 8. Issue 1, pp. 1-18. Oliver Selfridge (in his 1993 Gardens of Learning paper) called the 1943 paper by McCullough & Pitts "the first AI paper ever". See also: A general theory of learning and conditioning: Part II, Psychometrika, June 1943, Volume 8, Issue 2, pp. 131-140 (https://link.springer.com/article/10.1007/BF02288697).