The Forer Effect: The Science of Fooling One Person with Sentences Meant for Everyone

In 1948, Bertram Forer, a clinical psychologist at a mental health clinic affiliated with the U.S. Department of Veterans Affairs in Los Angeles, conducted an experiment in his introductory psychology class that later became one of the most enduring findings in the history of personality psychology. The result of this experiment is now known as the “Forer Effect” or the “Barnum Effect”; a phenomenon that explains why daily horoscopes, astrology, handwriting analysis, and today even online personality tests can seem so “accurate” and “made specifically for us.”

The Experiment: One Text, 39 People, and a Collective Laugh

Before this experiment, Forer had designed a test called the Diagnostic Interest Blank (DIB), a questionnaire about people’s interests, hobbies, personality traits, and hidden aspirations. When he introduced the instrument in class, students asked him to administer the test and provide them with an analysis of their personalities. Forer agreed.

Thirty-nine students completed the questionnaire. A week later, each received a sheet with their name on it and a 13-point personality description below. What no one knew was this: all 39 sheets were exactly identical, word for word. Forer even made sure that the students were seated two chairs apart on a day when they also had another exam, preventing them from comparing their sheets.

The description was a combination of sentences that Forer himself said he had taken largely from a cheap astrology book; sentences such as:

You have a great need for other people to like and admire you... Although you strive to improve yourself, you still have considerable unused capacity within you... On the outside you appear disciplined and self-controlled, but inside you tend to be worried and insecure... You take pride in your independent thinking and do not accept others’ claims without sufficient reason... Security and peace are among your main goals in life.

The students were asked to rate two things: first, how well the DIB test represented their personality (from zero to five), and second, how accurate the description itself was. They were also asked to mark each of the 13 statements individually as “true,” “false,” or “uncertain.”

The result? Out of 39 people, only one gave the test a score below 4; everyone else rated it between 4 and 5. For the description itself, only five people gave a score below 4. The average number of statements that each person identified as “true about themselves” was 10.2 out of 13 statements.

When Forer asked the class who thought the test had worked well, almost everyone raised their hand. He then read the first statement of the description aloud and asked who had seen something similar on their own sheet. All the hands went up again — and at that moment the class realized that everyone had received the same text. According to Forer’s own report, at least one-third of the students later asked him to give them a copy of the text so they could try “the same trick” on their friends.

Why Does This Trick Work?

Forer explained that the secret lies in what he called a “valid description for everyone” — derived from a concept that the German psychologist Otto Buber-Tarock had called “universal characteristic.” The logic is simple: having two eyes tells us nothing about how one person differs from another, because everyone has two eyes. Similarly, statements such as “you sometimes doubt yourself” or “sometimes you need solitude and sometimes you need company” are true of almost every person on Earth — not because the individual is special, but because such traits do not distinguish anyone from others.

Quoting Gordon Allport, one of the pioneers of personality psychology, Forer wrote: “One way personality analysts gain fame is by using vague terms that apply to every mortal human being.” The important point is this: people usually recognize these traits in themselves easily — when those traits are not harmful to their self-image — while overlooking the same traits in others. This is why, for example, psychology students reading psychiatric textbooks often find symptoms of themselves in descriptions of disorders.

Forer called this process “Personal Validation”: judging the accuracy of an analysis by asking the person’s own opinion. The problem is that if a description is fundamentally “valid for everyone,” receiving confirmation from the individual has no evidential value — because the description would have been confirmed anyway, regardless of whether the measuring tool had actually discovered anything. The greater danger appears when this confirmation is unconsciously extended to the entire tool or the entire analyst; that is, the person not only believes the description but also begins to place greater trust in the test and its creator.

Forer also described a personal experience in his article: a handwriting analyst at a nightclub asked him to read his handwriting. Instead of accepting, Forer suggested that he administer a Rorschach test to the handwriting analyst himself. A friendly debate followed, during which the handwriting analyst claimed that the scientific basis of his work could be seen in the approval of his clients. Forer responded that even a blindfolded psychologist could achieve the same level of “confirmation” — because receiving approval has nothing to do with actual accuracy.

Statistical Results: Not Random, but Patterned

Forer also carefully examined the data. It was found that there was a significant correlation at the one percent level between the rating of the description (how accurate it was) and the number of statements that individuals marked as “true” — meaning that the more statements people matched to themselves, the more accurate they considered the description. Interestingly, however, there was no significant relationship between ratings of the DIB test itself and the number of correct statements. In other words, acceptance of the test was an “all-or-nothing” phenomenon: once a certain threshold of evidence was crossed, individuals accepted the entire tool, regardless of how much of the description actually matched them.

Three weeks later, Forer conducted another small experiment: he asked the remaining 32 participants to recall the scores they had given to the test and the description. The results showed that the scores people remembered giving to the description were significantly lower than their actual scores — seven people who had given a score of 5 remembered it as 4. Forer considered this evidence of a defensive mechanism of memory: when a person’s self-esteem is threatened (in this case, by realizing they had been fooled), memory unconsciously distorts reality slightly to soften the blow.

From Forer’s Classroom to Our Phone Screens

What Forer demonstrated in 1948 with paper and pencil is now repeated on a massive scale through digital tools. Online personality tests, daily horoscope apps, astrology websites, and even some products that present themselves as “scientific” use the same technique of the “statement valid for everyone” — only with a more modern package: algorithms, artificial intelligence, or data analysis.

Consider, for example, a text like this, which could today appear as the result of an online “personality analysis” test:

You tend to be self-critical and sometimes have serious doubts about whether you have made the right decision or choice... On the surface you appear disciplined and self-controlled, but inside you may experience worry and insecurity... You need others to like, admire, and accept you... Sometimes you are outgoing and social, while at other times you need solitude and privacy... You enjoy change and variety, and too many restrictions can make you dissatisfied.

If you compare these sentences with Forer’s original text, there is little difference — only a more contemporary tone and smoother phrasing. These kinds of texts usually share three characteristics, each of which is exactly what Forer described:

1. Internal duality in each statement. Sentences such as “you are sometimes extroverted and sometimes introverted” or “you are both disciplined and occasionally insecure” cover both ends of a spectrum at once. Anyone reading them can recall a moment when they experienced that state — because all people experience both sides of such a spectrum in different situations.

2. A balance of positive and negative. Descriptions usually place a weakness beside a strength (“despite some weaknesses, you can generally overcome them”). Research after Forer has shown that people are more likely to believe flattering or moderately positive descriptions than neutral or negative ones — which is why these texts usually frame flaws and weaknesses as “opportunities for growth” rather than genuine shortcomings.

3. A veneer of credibility. When a text is presented by a “smart algorithm,” a scientific-looking test, or an experienced astrologer, our minds are prepared to accept it before reading even a single word. Forer made the same point about the handwriting analyst at the nightclub: a socially “credible-looking” setting makes belief easier, regardless of the actual accuracy of the claim.

Horoscopes and Astrology: The Same Mechanism, a Different Outfit

Astrology works in much the same way, with one difference: even the supposedly personalized input is merely a birth date or zodiac sign — something that contains no genuine psychological information about the individual. Daily horoscope texts for “Leo” or “Gemini” are often written so broadly that they can fit anyone, regardless of their sign: “Today is a day when new opportunities may appear before you, but you should also pay attention to your close relationships.” There is hardly any day on which such a sentence would not be true for any human being.

An important point that Forer emphasizes in the conclusion of his article is this: the overall evaluation of a description is more vulnerable to error than the evaluation of each individual sentence. In other words, when you ask someone, “How accurate is this description overall?”, their answer will likely be more positive than it would be if they examined each sentence separately and carefully. That is why quickly and generally reading a horoscope or personality test result creates a stronger sense of correspondence than comparing each sentence individually with the realities of one’s life.

How Can We Avoid Being Fooled by These Texts?

At the end of his article, Forer draws six conclusions that remain useful guides today:

First, the claim of validity made by any pseudoscientific tool or person — from fortune-tellers to personality-test apps — can be reproduced or even surpassed without any genuine measurement tool, simply by using a prewritten identical text. Second, validation through a person’s own approval is an inherently flawed method because it assumes that our self-assessment is objective and unbiased — while it usually is not. Third, even a fabricated description can persuade people to accept a tool, even if they do not fully accept the description itself; a minimal degree of fit is enough.

The practical point is this: whenever you read a text about your “real personality” and feel, “Wow, that is exactly me!”, try a simple exercise: read each sentence separately and ask yourself, “Could I say this about three other people I know and find it equally true?” If the answer is yes — and in most of these texts it is — then what you have read is not a mirror; it is a blurred painting in which everyone sees their own face.