Animal Language Research: Marine Mammals Re-Enter the Controversy

Abstract

A horse named Clever Hans, who lived in Germany at the turn of the century, drew world-wide attention because he could apparently talk and solve arithmetical problems. By tapping with his front leg the horse could not only do arithmetic, but could also combine letters into words, words into sentences, and thus express his thoughts. What his questioners were unaware of was that Clever Hans used a simple “go” or “no-go” set of cues. The “go” cue was a slight leaning forward by the questioner, the “no-go” cue was an inadvertent straightening-up by the questioner when the correct number of taps had been reached (Pfungst, 1911; Sebeok and Rosenthal, 1981). Every time the correct number of taps was given the horse received a food reward. There are two lessons to be learned from the Clever Hans Effect, as it has come to be known. The first lesson is an obvious one; take precautions to prevent inadvertent cueing of subjects in psychological experiments. The second, and related, lesson is that one should interpret animal behavior parsimoniously rather than otherwise, i.e. use simple and straightforward assumptions and explanations of behavior rather than invoking uncalled-for complex processes.