Thinking Animals ¹

Abstract

ABOUT ten years ago it became known that “Clever Hans,” an Arab stallion owned by a Herr von Osten in Berlin, was able to answer arithmetical and other questions, tapping out the reply with his fore-foot. Notoriety led to heated controversy, and the appointment of committees to investigate. The second of these, under Prof. Stumpf, resulted ifl Pfungst's book, explaining everything in terms of signals consisting in slight movements made unconsciously by some person present knowing the answer. This seemed to have solved the problem finally until the appearance of Krall's book in 1912. The author, a wealthy jeweller of Elberfeld and friend of von Osten's, had after the latter's death continued to experiment, obtaining results which, he claimed, refuted Pfungst's explanation. This laim found support in a report signed by the zoologists, Kraemer, Sarasin, and Ziegler, asserting that signalling was excluded since correct answers were given even when. none of the human participanth was visible to the animal. The opinions expressed on Krall's book vary from that of Prof. Dexler—“a shameful l)lOt on German literature,” to that of Prof. Ostwald, who foresees that it will “as clearly mark. the beginning of a new chapter in the doctrine of man's place in nature as Darwin's chief work did in its day.”