Clever Hans Phenomenon

Clever Hans appeared to solve math problems, but he was actually responding to his trainer, Von Austin.
Crowds gathered to watch Clever Hans, and Von Austin earned a significant amount of money from these performances.
Von Austin genuinely believed that Clever Hans was intelligent and capable of solving math problems.

The audience would focus on Hans' hooves as he tapped.
When asked a question like "What's two plus two?", Hans would begin tapping his hoof.
Crucially, Hans would stop tapping when he reached the correct number (e.g., four).
Key Observation: The crowd would change their posture (stand straight up) when Hans reached the correct number of taps.
Clever Hans learned to associate the change in the audience's posture with receiving a treat.
In essence, Hans was trained to stop tapping his hoof when people changed their posture.

Psychologists conducted experiments to demonstrate that Hans was responding to cues rather than solving math problems.
Experiment 1: The experimenter was placed behind a curtain, preventing Hans from seeing them.
- Result: Clever Hans could no longer provide the correct answer.
Experiment 2: The question was whispered into Clever Hans's ear, so the audience couldn't provide cues.
- Result: Clever Hans could not get the right answer.
Experiment 3: The experimenter or trainer did not know the answer to the question.
- Result: Clever Hans failed to give the correct answer.

The behavior of the people around Clever Hans created a self-fulfilling prophecy.
The audience's expectation that Clever Hans would get the right answer influenced their behavior (posture).
This change in behavior (posture) acted as a signal for Clever Hans to stop tapping and get a reward.
In summary, the belief in Clever Hans's abilities inadvertently led to him "getting" the right answer through unintentional cues from the audience.