The Barnum effect explains how horoscopes can sound scarily accurate

Have you ever read a horoscope and wondered how it managed to be weirdly accurate? Or got a result in an online quiz that honestly did sound familiar? It could be down to a psychological quirk called the Barnum effect.

Personality sketch

The Barnum effect is also sometimes known as the Forer effect. In a now-classic experiment in psychology, Bertram Forer gave his introductory psychology class of 39 students a personality test. A week later, he gave each student a ‘personality sketch’ containing 14 sentences he said summed them up.

He then asked the students to rate the sketch’s accuracy on a scale of 1 to 5. They gave it an average of 4.3.

But here’s the kicker: They’d all read the exact same sketch. In fact, in the paper where he describes the experiment, published in the Journal of Abnormal Psychology in 1949, Forer says he cobbled it together from a “news stand astrology book”.

Here’s the paragraph each student was given:

“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. Your sexual adjustment has presented problems for you. 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.”

Sound familiar? Despite knowing that it’s not written specifically for you, it’s still hard to not see yourself in those statements.

Forer’s experiment was later replicated and people consistently rated the general statements they were given as highly accurate.

Barnum statements

Phrases that sound specific to you but are actually applicable to lots of people are called Barnum statements, after entertainer Phineus Taylor Barnum, whose life and work was the inspiration behind the film The Greatest Showman, released last year.

This name was coined in 1956 by Paul Meehl in an essay published in the American Psychologist. Meehl was frustrated by psychologists making statements about patients that could really be applied to anyone. He said:

“I suggest—and I am quite serious—that we adopt the phrase Barnum effect to stigmatize those pseudosuccessful clinical procedures in which personality descriptions from tests are made to fit the patient largely or wholly by virtue of their triviality.”

The key feature of a Barnum statement is that it’s sufficiently vague for anyone to be able to find meaning in it. A form of cognitive bias called subjective validation can then come into play, and make you think of the statement as true to you, without considering that it could be equally true of most other people.

Barnum’s own recipe for the success of his show was to “always have a little something for everybody.”

Your brain’s tendency to attach personal meaning to things, and discard anything that doesn’t fit, is something that psychics rely on to convince people they know more than they really do. And it works. Psychologist Barry Beyerstein, a critic of graphology, has written that “hope and uncertainty evoke powerful psychological processes that keep all occult and pseudoscientific character readers in business.”

In fact, Forer says he originally decided to try the experiment on his class after he was “accosted by a night-club graphologist who wished to ‘read’ his handwriting”. When Forer questioned how the graphologist knew his predictions were accurate, he said that his clients always told him they were correct.

Forer’s conclusion, after his experiment, was that people’s own assessment of what was accurate about themselves could not be trusted. He wasn’t very forgiving of the students who were taken in by his trick, and called his paper about it “a classroom demonstration of gullibility.”

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