Sunday, 24 February 2008

the barnum effect by forer

The Barnum Effect

In the late 1940s, psychologist Bertram Forer published an eye-opening study that he called a "demonstration of gullibility" (Forer 1949). After administering a questionnaire to his introductory psychology class, he prepared personality sketches. For example: "Disciplined and self-controlled outside, you tend to be worrisome and insecure inside. At times you have serious doubts as to whether you have made the right decision or done the right thing. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations."

Forer asked the students to rate their own sketches for accuracy. The students gave an average rating of "very good." More than 40 percent said that their sketch provided a perfect fit to their personality.

The results seemed to show that Forer's personality questionnaire possessed a high degree of validity. However, there was a diabolical catch: Forer had given all the students the same personality sketch, which he manufactured using horoscopes from an astrology book. The students had gullibly accepted this boiler-plate personality description as if it applied to them uniquely as individuals.

Although the statements borrowed from the astrology book were seemingly precise, they applied to almost all people. Following the eminent researcher Paul Meehl, psychologists now call such personality statements "Barnum statements," after the great showman P.T. Barnum who said, "A circus should have a little something for everybody" (he's also credited with, "There's a sucker born every minute").

As Forer had discovered, people tend to seriously overestimate the degree to which Barnum statements fit them uniquely. For example, students in one study who were given Barnum statements disguised as test results responded with glowing praise: "On the nose! Very good"; "Applies to me individually, as there are too many facets which fit me too well to be a generalization."

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