Tuesday, September 11, 2012

The Barnum Effect

Apparently, one can fool most of the people all of the time, according to this quote from FOOLING HOUDINI: Magicians, Mentalists, Math Geeks, and the Hidden Powers of the Mind by Alex Stone.

In 1948 the American psychologist Bertram Forer conducted an experiment in which he administered a personality test, called the Diagnostic Interest Bank, to a group of thirty-nine college students. A week after conducting the survey, he handed each student a personality description that was supposedly based on the data he'd collected. The students were then asked to rate the accuracy of their profiles on a scale of zero to five, with five being a perfect match and zero being poor. The results were impressive. The average score was a 4.26, meaning that a majority of the students thought the personality descriptions were spot-on. Only 12.8 percent of the students ranked their profiles below a 4.0 ("very accurate"), and none scored theirs lower than 2.0 ("average"). Typical responses from the students included statements such as:

- Surprisingly accurate and specific.- On the nose!- Very good. I wish you had said more.- Applies to me individually, as there are too many facets which fit me too well to be a generalization.
The Diagnostic Interest Blank seemed to be a sharp tool indeed. Except for one thing: Forer never used it. In reality, he had scrapped the test and given every student identical "personality descriptions" that consisted of a list of generic statements lifted from a newsstand astrology book:
- You have a great need for other people to like and admire you.- You have a tendency to be critical of yourself.- You have a great deal of unused capacity, which you have not turned to your advantage.
Forer had not unearthed some divine trove of universal truth at his local magazine store, but he had discovered a fascinating and surprisingly universal psychological principle, one that lies at the heart of every horoscope and palm reading and psychic divination, a multi-billion dollar industry in the United States alone. Forer's original result has been replicated dozens of times -- to this day, the average rating hovers around 4.2 -- and psychologists have since given a name to the astonishing eagerness with which people will embrace stock personality sketches as unique portraits. They call it the Barnum effect, after P. T. Barnum's favorite dictum, "We've got something for everyone."

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Truth is...another quote, often attributed to Barnum but probably actually uttered by a David Hannum, might be more appropriate: There's a sucker born every minute.

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