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The Barnum effect, also called the Forer effect, is the observation that individuals will give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them but are, in fact, vague and general enough to apply to a wide range of people. This effect can provide a partial explanation for the widespread acceptance of some beliefs and practices, such as astrology, fortune telling, graphology, aura reading and some types of personality tests.
A related and more general phenomenon is that of subjective validation. Subjective validation occurs when two unrelated or even random events are perceived to be related because a belief, expectation, or hypothesis demands a relationship. For example, while reading it, people actively seek a correspondence between their perception of their personality and the contents of a horoscope.
The name "Barnum effect" seems to have originated with psychologist Paul Meehl in reference to the American circus entertainer P.T. Barnum, said to have claimed "we have something for everybody", or possibly in the sense of the noun meaning 'nonsense, humbug' to which he also lends his name.
In 1948, psychologist Bertram R. Forer gave a psychology test—his Diagnostic Interest Blank—to a group of his psychology students who were told that they would each receive a brief personality vignette or sketch based on their test results. One week later Forer gave each student a purportedly individualized sketch and asked each of them to rate it on how well it applied. In reality, each student received the same sketch, consisting of the following items:
- 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.
- While you have some personality weaknesses, you are generally able to compensate for them.
- 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.
- You pride yourself as an independent thinker and do not accept others' statements without satisfactory proof.
- You have found it unwise to be too frank in revealing yourself to others.
- At times you are extroverted, affable, sociable, while at other times you are introverted, wary, reserved.
- Some of your aspirations tend to be pretty unrealistic.
- Security is one of your major goals in life.
On average, the students rated its accuracy as 4.26 on a scale of 0 (very poor) to 5 (excellent). Only after the ratings were turned in was it revealed that each student had received an identical sketch assembled by Forer from a newsstand astrology book. The sketch contains statements that are vague and general enough to apply to most people.
In another study examining the Forer effect, students took the MMPI personality assessment and researchers evaluated their responses. The researchers wrote accurate evaluations of the students’ personalities but gave the students an accurate assessment and a fake assessment using vague generalities. Students were then asked to choose which personality assessment they believe was their own, actual assessment. More than half of the students (59%) chose the fake assessment as opposed to the real one.
The Forer effect is also known as the "Barnum effect". This term was coined in 1956 by American psychologist Paul Meehl in his essay "Wanted — A Good Cookbook". He relates the vague personality descriptions used in certain "pseudo-successful" psychological tests to those given by entertainer and businessman P. T. Barnum, who was a notorious hoaxer.
Repeating the study
Two factors are important in producing the effect, according to the findings of replication studies. The content of the description offered is important, with specific emphasis on the ratio of positive to negative trait assessments. The other important factor is that the subject trusts the person giving feedback to give them feedback based on honest assessment.
The effect is consistently found when the assessment statements are vague. People are able to read their own meaning into the statements they receive, and thus, the statement becomes "personal" to them. The most effective statements include the phrase "at times", such as "At times you feel very sure of yourself, while at other times you are not as confident." This phrase can apply to almost anyone, and thus each person can read a "personal" meaning into it. Keeping statements vague in this manner ensures observing the Forer effect in replication studies.
In 2011, the study was repeated with the statements altered so that they applied to organisations rather than individuals. The results were similar, suggesting that people anthropomorphize organisations and are gullible when interpreting their characters.
Variables influencing the effect
Studies have shown that the Forer effect is seemingly universal—it has been observed in people from many cultures and locations. In 2009, psychologists Paul Rogers and Janice Soule conducted a study that compared the tendencies of Westerners to accept Barnum personality profiles to the tendencies of Chinese people. They were unable to find any significant differences.
Later studies have found that subjects give higher accuracy ratings if the following are true:
- the subject believes that the analysis applies only to them, and thus applies their own meaning to the statements.
- the subject believes in the authority of the evaluator.
- the analysis lists mainly positive traits.
The method in which the Barnum personality profiles are presented can affect the extent to which people accept them as their own. For instance, Barnum profiles that are more personalized—perhaps containing a specific person's name—are more likely to yield higher acceptability ratings than those that could be applied to anyone.
Belief in the paranormal
Subjects who, for example, believe in the accuracy of horoscopes have a greater tendency to believe that the vague generalities of the response apply specifically to them. Studies on the relationship between schizotypy and susceptibility to the Forer effect have shown high amounts of correlation. However, Rogers and Soule's 2009 study (see "Variables influencing the effect" above) also tested subjects' astrological beliefs. Both the Chinese and Western skeptics were more likely to identify the ambiguity in the Barnum profiles. This suggests that individuals who do not believe in astrology are possibly influenced less by the effect.
Self-serving bias has been shown to cancel the Forer effect. According to the self-serving bias, subjects accept positive attributes about themselves while rejecting negative ones. In one study, subjects were given one of three personality reports. One contained Barnum profiles with socially desirable personality traits, one contained profiles full of negative traits (also called "common faults"), and the last contained a mixture of the two.
Subjects who received the socially desirable and mixed reports were far more likely to agree with the personality assessments than the subjects who received negative reports, though it should be noted that there was not a significant difference between the first two groups.
In another study, subjects were given a list of traits instead of the usual "fake" personality assessment. The subjects were asked to rate how much they felt these traits applied to them. In line with the self-serving bias, the majority of subjects agreed with positive traits about themselves and disagreed with negative ones. The study concluded that the self-serving bias is powerful enough to cancel out the usual Forer effect.
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