From the 1920s onward, the battle over the unconscious was being fought and lost in the fields of academic laboratory psychology in the United States. In the opening decades of the 20th century, first, the specter of Pavlov and then Watson began to dominate the academic laboratories with theories of learning and their emphasis on classical conditioning. In the 19-teens and twenties, Thorndike's theory of selecting and connecting and Toleman's conceptions of latent learning had their adherents, while Kohler's studies of insight learning, which had suddenly burst upon the scene with the publication of The Mentality of Apes (1925)¹ never made any impact among the experimentalists.