Clever Hans
Clever Hans (
Spectacle
During the early twentieth century, the public was especially interested in
Hans was a horse owned by Wilhelm von Osten, who was a
After von Osten died in 1909, Hans was acquired by several owners. After 1916, there is no record of him and his fate is unknown, but he was drafted into World War I as a military horse and "killed in action in 1916 or was consumed by hungry soldiers".[4]
Investigation
The great public interest in Clever Hans led the German board of education to appoint a commission to investigate von Osten's scientific claims.
The commission passed off the evaluation to Oskar Pfungst, who tested the basis for these claimed abilities by:
- Isolating horse and questioner from spectators, so no cues could come from them
- Using questioners other than the horse's master
- By means of blinders, varying whether the horse could see the questioner
- Varying whether the questioner knew the answer to the question in advance.
Using a substantial number of trials, Pfungst found that the horse could get the correct answer even if von Osten himself did not ask the questions, ruling out the possibility of fraud. However, the horse gave the right answer only when the questioner knew what the answer was and the horse could see the questioner. He observed that when Hans could see the questioner, the horse got 89 percent (50 out of 56) of the answers correct, but when Hans was not able to see the questioner, the horse answered only six percent (2 out of 35) of the questions correctly.[5]
Pfungst was aware of the ability of circus trainers to train horses to respond to small gestures, and was aware of a number of cases of dogs, like that of English astrophysicist Sir
Pfungst carried out laboratory tests with human subjects, in which he played the part of the horse. Pfungst asked subjects to stand on his right and think "with a high degree of concentration" about a particular number, or a simple mathematical problem. Pfungst would then tap out the answer with his right hand. He frequently observed "a sudden slight upward jerk of the head" when reaching the final tap, and noted that this corresponded to the subject resuming the position they had adopted before thinking of the question.[5]
Some critics of Pfungst suggest that a proper way of validating the body language hypothesis should involve Pfungst acting out the same body language cues himself in order to reliably get Hans to give wrong answers, this would've validated the hypothesis that Hans is simply tapping in correspondence with certain body language cues, independently of the true answer, however Pfungst never was able to successfully validate his hypothesis in this manner.
After the investigations by Pfungst were done, von Osten, who was never persuaded by Pfungst's findings, continued to show Hans around Germany, attracting large and enthusiastic crowds.[3]
The Clever Hans effect
After Pfungst had become adept at giving Hans performances himself, and believed he was fully aware of the subtle cues which made them possible, he discovered that he would produce these cues involuntarily regardless of whether he wished to exhibit or suppress them.[citation needed] Recognition of this phenomenon has had a large effect on experimental design and methodology for all experiments whatsoever involving sentient subjects, including humans.
The risk of Clever Hans effects is one reason why
The Clever Hans effect has also been observed in
A 2004 study of Rico, a border collie reported by his owners as having a vocabulary of over 200 words, avoided the Clever Hans effect by having the owner ask the dog to fetch items from an adjacent room, so that the owner could not provide real time feedback while the dog was selecting an object.[citation needed]
A study conducted in 2012 examined the socio-communicative ability of dogs with humans, looking at how much of an influence an owner, if present, would have on their dog during an object-choice pointing task, including looking at whether a Clever Hans effect was present. The study concluded that when the experimenter provided a pointing gesture regardless of the owner’s knowledge, and that when no pointing cue was given to the dog, it only performed at chance level. This study proved that, for this pointing task, there was no Clever Hans effect affecting the dogs' performance, as long as the owners did not actively influence them.[8]
Similarly, a study done in 2013 also examined whether a Clever Hans effect was present in a two-way object choice test and included an experimental group in which the owners actively tried to influence their dog's decision. The results showed that the experimenter had the strongest effect on the dog's choice in this task, regardless of the owner's knowledge or actions. This provides evidence that the Clever Hans effect is not always present when humans and dogs interact.[9]
Pfungst's final experiment showed that Clever Hans effects can occur in experiments with humans as well as with animals.
See also
- List of historical horses
- Harass II, a dog used in criminal investigations
- Ideomotor phenomenon
- Lady Wonder, a horse with purported telepathic abilities.
- Beautiful Jim Key
- Muhamed (horse)
References
- ^ "Clever Hans phenomenon". skepdic. Retrieved 2008-12-11.
- .
- ^ "Berlin's Wonderful Horse; He Can Do Almost Everything but Talk – How He Was Taught" (PDF). The New York Times. 1904-09-04. Retrieved 2008-02-26.
- PMID 24563716.
- ^ a b c "The Project Gutenberg eBook of Clever Hans (The Horse of Mr. von Osten), by Oskar Pfungst". Gutenberg.org. Retrieved 2013-10-21.
- ^ Oskar Pfungst, Clever Hans: (The Horse Of Mr. Von Osten), Pfungst 1911 pp.177-185
- ^ "Clever Hounds" (URL). The Economist. 2011-02-15. Retrieved 2011-05-14.
Sources
- ^ Hothersall, David. History of Psychology. McGraw-Hill. 2004.
- Pfungst, O. (1911). Clever Hans (The horse of Mr. von Osten): A contribution to experimental animal and human psychology (Trans. C.L. Rahn). New York: Henry Holt. (Originally published in German, 1907).
- The London Standard (1904-10-02). ""Clever Hans" Again. Expert Commission Decides That the Horse Actually Reasons" (PDF). The New York Times. Retrieved 2008-01-02.
External links
- Clever Hans the Math Horse
- Clever Hans public domain audiobook at LibriVox