Oskar Pfungst

The purpose of this commission was misunderstood, and therefore many were disappointed with the report which it published, (Supplement II). Some had been expecting a positive conclusive explanation; the commission recommended further investigation. Some had asked for a solution of the question whether or not the horse was able to think; the commission maintained neither the one, nor the other. Some had indicated as the main condition of a satisfactory investigation, that both Mr. von Osten and Mr. Schillings be excluded from the tests; this was not done. But the commission-which, by the way, did not give itself this name, since it had been delegated by no one-undoubtedly had the right to formulate its problem as it saw fit, and this was carefully expressed at the beginning of its report as follows: "The undersigned came together for the purpose of investigating the question whether or not there is involved in the feats of the horse of Mr. von Osten anything of the nature of tricks, that is, intentional influence or aid on the part of the questioner." It was this preliminary question, and not whether or not the horse could think, which the commission intended to answer.

Oskar Pfungst (1874-1933) was a German comparative biologist and psychologist. While working as a volunteer assistant in the laboratory of Carl Stumpf in Berlin, Pfungst was asked to investigate the horse known as Clever Hans, who could apparently solve a wide array of arithmetic problems set to it by its owner. After formal investigation in 1907, Pfungst demonstrated that the horse was not actually performing intellectual tasks, but was watching the reaction of his human observers. Pfungst discovered this artifact in the research methodology, wherein the horse was responding directly to involuntary clues in the body language of the human trainer, who had the faculties to solve each problem. The trainer was entirely unaware that he was providing such cues.In honour of Pfungst's study, the anomalous artifact has since been referred to as the Clever Hans effect and has continued to be important knowledge in the observer effect and later studies in animal cognition.Pfungst never earned an advanced academic degree, though he later received an honorary MD from the University Frankfurt, where he lectured. According to Zusne (1984), Pfungst published only "about fifteen titles" in his career.