APA Dictionary of Psychology

the “thinking horse,” reputed to be able to solve mathematical problems, spell words, distinguish colors, and identify coins, that became famous in Berlin around 1900. It signaled its answers by tapping its foot. However, German psychologist Oskar Pfungst (1874–1932), using experimental methods, demonstrated that the horse was responding to minimal cues in the form of involuntary movements on the part of its owner.