"You have a great need for other people to like and admire you. You have a tendency to be critical of yourself." Sound like you? It sounds like almost everyone. That is exactly the problem, and it is what an experiment run in 1948 in an American classroom showed.
Bertram Forer's experiment
Psychologist Bertram Forer gave a personality test to his 39 students. A week later, each of them received a profile presented as personal, drawn up from their answers. They were asked to rate, from 0 to 5, how well the profile fitted them.
The average was above 4 out of 5. The students found their profile remarkably accurate. Then Forer revealed the trick: they had all received exactly the same text, made of thirteen sentences taken mostly from an astrology book bought at a newsstand. Here are a few of them:
- "You have a great need for other people to like and admire you."
- "You have a great deal of unused capacity which you have not turned to your advantage."
- "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."
Forer published his results in 1949 under a blunt title: The fallacy of personal validation: a classroom demonstration of gullibility.
Why "Barnum"?
The name comes from P. T. Barnum, the famous 19th-century American showman whose circus was said to offer "a little something for everybody". In 1956, psychologist Paul Meehl used the expression to criticize psychological reports so vague that they would fit any patient. The term stuck. It is also called the Forer effect, or subjective validation.
The ingredients of a profile that rings true
Barnum statements are not chosen at random. They share a few well-known recipes:
- they apply to almost everyone: who has never doubted themselves or wanted to be liked?
- they cover both sides: "sometimes sociable, sometimes reserved" covers every possibility at once;
- they are flattering: untapped potential, independent thinking… Researchers have shown that people accept a positive profile far more readily than a negative one;
- they stay vague: the reader does the work, searching their memories for examples that fit.
Context matters too. In later studies, people rated a profile as more accurate when they believed it had been made for them alone, for example from their exact date and time of birth, and when the source seemed competent.
A serial killer's horoscope
The French statistician Michel Gauquelin, who spent much of his life testing astrology scientifically, told of a famous experiment. He offered a free personalized horoscope through a newspaper ad. Everyone who replied received the same text: the horoscope of Dr Marcel Petiot, one of the worst serial killers in French history. According to his account, more than nine out of ten said they recognized themselves, and several added that their family and friends recognized them too.
Wherever people talk about us
The Barnum effect explains much of the success of horoscopes: a text written for one twelfth of humanity often seems to hit the mark. It is also the favorite tool of psychics and mentalists, who practice "cold reading": general statements, then close attention to the person's reactions to refine as they go.
Personality tests are not immune either, including the best known ones in the workplace. The MBTI, which sorts people into sixteen types, is heavily criticized by psychologists: a large share of people get a different type when they retake the test a few weeks later, which does not stop them from finding their description very accurate each time. By contrast, the Big Five model (openness, conscientiousness, extraversion, agreeableness, neuroticism), used in research, has been validated over decades. But even a serious test benefits from the Barnum effect: the feeling that a result is accurate does not prove that it is.
What about our quizzes?
Our quizzes are made for fun, and they are no exception. When a result profile sounds like you, part of that impression comes from you: you search your own life for what fits. That is not a flaw, it is what makes the exercise enjoyable. You just need to read it as a mirror, not as a diagnosis.
A quiz like Are you really your sign, or just its cliché? actually plays with this trap: it does not look at your sign, but at your relationship with astrology.
Three habits to avoid being fooled
- The neighbor test: read someone else's horoscope or result. If it fits you as well as your own, it is a Barnum profile.
- Hunt for two-sided phrases: "sometimes… sometimes", "you can be… but also…". A sentence that says everything says nothing.
- Look for a counterexample: ask yourself what in the profile could not apply to you. If nothing could, it tells you nothing about yourself.
In short
- In 1948, Bertram Forer gave the same profile to 39 students, who on average rated it as very accurate.
- The Barnum effect relies on universal, flattering and vague statements, and on the feeling that they were written for us.
- It explains the success of horoscopes, fortune-telling and part of the success of personality tests.
- A result that "rings true" is not proof. It can still be a good moment, as long as you take it as a game.
