The year is 1904. The spectators hold their breath in anticipation as a horse, Hans, stamps his hoof on the blackboard—on which the whole alphabet was written—in front of him, picking out the letters H, N, and A. The audience sighs in relief. Dohna—the name of the officer standing before Clever Hans and his owner Herr Wilhelm von Osten, and to whom they have been introduced earlier. Von Osten reaches out his hand to Hans to give the horse a treat. Everyone claps, but they look in bewilderment at each other as if to ask—how? Von Osten claims that he taught Hans just as any person might teach a child: Hans is instructed to “count” the number of balls by tapping his hoof—at the same time, von Osten counts out loud with him. Thus, supposedly, Hans associates the auditory signal provided by von Osten with the visual signals, and the hoof taps are a way for Hans to communicate the visual signals he perceives. Even philosopher-psychologist Carl Stumpf, who formed the Hans Commission in order to investigate the truthfulness of the phenomenon in 1904, concludes that Hans is, truly, capable of performing mathematical operations such as addition, fractions, and even square roots. Three years later, Professor Oskar Pfungst, a psychologist, studies the Orlov Trotter closely in his laboratory, and comes upon this conclusion: Clever Hans is clever, indeed, but not in the way his admirers, and even his trainer, know. Although Hans could generally answer the questions posed by people other than von Osten, the accuracy of his answers drops when the questioner was far, or completely obstructed from Hans’s view, and when the questioner did not know the answer to the question beforehand. Upon even closer investigation, Pfungst realizes that Hans derives his answers from the very subtle body language of his questioner. When Pfungst asks Hans a question, the psychologist looks down to observe the number of stamps the horse makes with his foot. When Hans arrives at the correct number of stamps, the researcher is satisfied and looks ever so slightly away, unwittingly signaling to the horse that he has arrived at the correct answer. The year is 1907, and Professor Oskar Pfungst discovers what will be known as the Clever Hans effect.
It is now 89 years later. An experimenter observes a subject walk along a hallway. He presses the stopwatch; it reads at around 8 seconds. He catches up with the participant and tells her the complete objective of the experiment—to see if participants primed with stimuli relevant to a stereotype would unconsciously embody the stereotype in some way. Minutes ago, this participant was made to manufacture a sentence out of a set of words given to them. Some of the words in this sentence were relevant to the elderly stereotype, such as “wise” and “wrinkle”. In some participants’ sentences, the words were completely neutral, age-wise. The experimenter tells the participant that they are investigating language proficiency in their participants. After the experimenter (partially) debriefs and thanks the participant for their time, a second experimenter takes note of the amount of time it takes for the participant to walk down the corridor—specifically, 9.75 m away from the doorway of the experiment room. As expected, the experiment appears to have significance—the participants who have been exposed to the elderly-stereotype-relevant words walk for an average of 8.28 seconds—significantly more than those who read age-neutral words, who walk for an average of 7.30 seconds. A replication of the experiment shows the same result: those who are primed walk an average of 8.20 seconds, while those who are not walk an average of 7.23 seconds. The year is 1996, and John A. Bargh, Mark Chen, and Lara Burrows have just shown that priming effects can still occur even when the subject is not aware of its presence.
The setting appears to be...