Clever Hans

Clever Hans is the famous 1911 study by Oskar Pfungst (1874-1932), the German psychologist who exposed how the horse Clever Hans, supposedly able to do arithmetic, was in fact reading unconscious cues from his questioners. Pfungst’s careful experiments gave science the Clever Hans effect, a permanent caution about experimenter influence that still shapes how animal cognition and psychology are tested. The book is a classic of experimental method. Free PDF download available on BDeBooks.