Clever Hans- an extraordinary horse

A study found in the Lilienfeld text that I found extremely interesting was the case of Clever Hans the horse. This was so interesting to me because the idea of a horse being able to do math problems is so radical in itself that I found it very hard to believe. As i was reading though, the explanation of how this horse was able to do math problems made me believe that it was true because I could not think of a logical reason as to how this could be fake. A panel of 13 psychologists tested Clever Hans and even they could not find any reason to prove that this was simply a trick.
Eventually a psychologist named Oscar Pfungst got to the bottom of this extreme case and revealed that the horse Clever Hans was indeed being helped unconsciously by the people who were asking the questions. The person who asked the question would tense up their muscles before Clever Hans got to the right answer and to the horse this was a signal that the answer was correct.
This case was the first case that demonstrated the experimenter expectancy effect. I think that is is a very important concept to understand because it is truly an unintentional bias. As humans we do not like to be wrong, so when we make a hypothesis it is our natural instinct to want it to be correct. Even though good psychologists know that they are not always going to be correct, I find it astonishing that we still unconsciously do things to prove we are right even if we honestly didn't intend to.
In the case of Clever Hans, the experimenter expectancy effect was present and it was an extraordinary claim that was overlooked by many psychologists. This proves that unusual cases need to be throughly examined in order to be proved true or false.