TL;DR: In a 1949 paper, psychologist Bertram Forer described giving 39 students identical personality profiles, mostly drawn from an astrology book sold at newsstands, while telling them each profile was their own personal result. The class rated the accuracy at an average of about 4.26 on a scale of 0 to 5. This phenomenon, later called the Barnum effect or Forer effect, shows that people tend to take vague descriptions that fit almost anyone as descriptions of themselves. Reviews by Dickson and Kelly (1985) and by Furnham and Schofield (1987) found that acceptance rises when a description seems tailored to the reader, is positive in tone, and comes from someone with authority. The main point to remember: a feeling that something is 'true about me' is not evidence, so test it yourself by showing the description to others and seeing whether they find it accurate too.
How did the Forer experiment unfold?
Psychologist Bertram R. Forer had 39 students in his introductory psychology class take a test called the "Diagnostic Interest Blank". He told them that each person would receive a short personality description, constructed individually from the results of their own test. A week later, Forer handed each student a description and asked them to rate how accurate it was about themselves.
The truth was that all 39 students received an identical description, most of whose sentences Forer had taken from an astrology book bought at a newsstand. The description contained 13 sentences, among them lines such as "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", "At times you are extroverted, affable, sociable, while at other times you are introverted, wary, reserved".
The average accuracy score the whole class gave was about 4.26 on a scale from 0 (very poor) to 5 (excellent). Only after collecting all the score sheets did Forer reveal that everyone had received the same description. He called this phenomenon the "fallacy of personal validation", and his 1949 paper, "The fallacy of personal validation: a classroom demonstration of gullibility" in The Journal of Abnormal and Social Psychology, described it as a classroom demonstration of gullibility.
Why do vague descriptive sentences make people feel they are accurate?
The core mechanism lies in the fact that the sentences in the experiment were at once vague, strongly positive in tone, and presented as produced by an expert on the basis of the recipient's own test results. These three factors together lead the reader to assign meaning to the wording and turn a sentence that is true of almost anyone into a sentence that feels true of themselves alone.
Two literature reviews often cited on this topic are Dickson and Kelly (1985), "The 'Barnum Effect' in Personality Assessment: A Review of the Literature", and Furnham and Schofield (1987), "Accepting personality test feedback: A review of the Barnum effect". According to Dickson and Kelly (1985), acceptance of a general description rises when the description appears to have been made specifically for the reader and when the content is positive. According to Furnham and Schofield (1987), the influencing factors include the positivity of the description, the false specificity of the wording, the credibility of the person giving the feedback, and the way the information was gathered.
The most effective sentences usually contain the phrase "sometimes" or "at times", for example "At times you are very confident, at other times you are not confident at all". This phrase is true of almost anyone, so each person can read a private meaning into it. Keeping the wording vague in this way is the condition for observing the Forer effect in replication studies.
Some evidence further suggests that people with an authoritarian or neurotic personality, or people with a higher than usual need for approval, show the Barnum effect more readily. People are also more willing to accept negative remarks about themselves if the person making them is regarded as a high-status expert.
Four conditions that raise accuracy scores
Later research brought together four conditions that lead recipients to give higher accuracy scores:
- The recipient believes the analysis was personalized, and therefore assigns personal meaning to the wording.
- The recipient believes in the credibility of the assessor.
- The analysis mainly lists positive personality traits.
- The descriptive sentences are vague and broad enough to be true of many people.
Are the Barnum effect and the Forer effect one and the same?
Yes, these are two names for the same phenomenon, but the origins of the names differ, and that is worth distinguishing. Forer, who produced the most famous demonstration of this phenomenon, called it the "fallacy of personal validation" in his 1949 paper; before him, Donald G. Paterson had used a description true of everyone to illustrate the same thing.
It was not until 1956 that psychologist Paul E. Meehl coined the term "Barnum effect" in his essay "Wanted: A Good Cookbook". He linked the vague personality descriptions used in some psychological tests that "succeed by pseudo-success" to the patter of circus impresario P. T. Barnum, famous for entertainment aimed at the crowd. So the same phenomenon can be called the Barnum effect, the Forer effect, or, less commonly, the Barnum-Forer effect.
How does this effect differ from cold reading and spiritual tricks?
The Forer effect is a core component of cold reading, the set of techniques that mentalists, fortune tellers and psychics use to create the impression that they know a great deal about the person in front of them. A cold reader needs no prior information; they observe body language, age, clothing, hairstyle, gender, religion, ethnicity, education level, manner of speech, place of residence, and then make high-probability guesses.
They then emphasize and reinforce the guesses that hit, while quickly skimming past the guesses that miss. Because most of the session is spent on the "hits", while the time spent noticing the "misses" is minimized, the participant feels that the reader knows far more about them than an ordinary stranger would.
One specific technique is "shotgunning": the reader throws out a very broad set of statements, watches the reaction, then narrows the range and adjusts the wording according to that reaction. For example, "I see a heart problem with a father in your family". Many illnesses involve chest pain, and heart disease is a leading cause of death worldwide. The phrase "a father" could mean a father, grandfather, uncle, cousin, or any man who has played a father's role for the listener.
Another technique is the "rainbow ruse", a sentence that pairs a personality trait with its opposite, for example "Most of the time you are positive and cheerful, but there have been times when you were very sad". This kind of sentence covers every possibility and still creates the impression that the reader has reasoned accurately, even though it is itself vague and self-contradictory. Personality traits are not measurable quantities, and almost everyone has experienced both sides of some emotion.
Warm reading and hot reading
Three levels need to be distinguished. Cold reading relies on the reactions of the person in front of you. Warm reading is the deliberate use of Barnum-effect sentences. Hot reading is the use of information already known about that person. When cold reading is combined with information gathered covertly, the reader can leave a very strong impression that they know, or have access to, a great deal of information about the participant.
Michael Shermer gives the example of the jewellery of a person in mourning. Most people in this situation are wearing or carrying a piece of jewellery connected to the deceased. But if asked directly in the setting of a spiritual reading whether they have such an item, the participant may be astonished and believe that the reader obtained that information directly from the deceased.
How much can audience size explain?
James Underdown of the Center for Inquiry and the Independent Investigations Group argues that in the setting of a full auditorium, cold reading is nothing very impressive, and he explains it with simple mathematics. A typical television audience has about 200 people, divided into three sections. A conservative estimate is that each person knows about 150 other people.
That means when a host asks "Who is Margaret?", they are hoping there is a Margaret among roughly 10,000 people in that area's database. If no one answers, they widen the question to the whole audience, with a database of more than 30,000 people. With a sample that large, having a few dozen people named Margaret is nothing surprising.
Mentalist Mark Edward recounts his own experience in the role of a spiritual performer. He threw out a line such as "a clown standing in a cemetery" to an audience of 300 people. A woman stood up and insisted he was speaking directly to her. She remembered that Edward had stated specifically that she knew a man dressed as a clown who placed flowers on a grave in her hometown. It took a while of persuading before she understood that he had not spoken to her individually at all, but had merely thrown that line out to the whole audience. Because the story sounded so personal and the situation so strange, she felt it was aimed straight at her.
Comparison table: vague sentences and why they are true of almost anyone
| Typical descriptive sentence | Why it is true of most people |
|---|---|
| "You have a great need for other people to like and admire you." | The need for approval is nearly universal in human beings. |
| "You have a tendency to be critical of yourself." | Almost everyone has blamed themselves at least once. |
| "At times you are extroverted, at other times introverted and wary." | The opposing pair covers every possibility and cannot be wrong. |
| "You have a great deal of unused capacity." | Everyone has skills or potential not fully exploited. |
| "Sometimes you doubt whether you made the right decision." | Doubting a decision is a common experience. |
| "You pride yourself on being an independent thinker." | Thinking highly of one's own independence is a common self-image. |
Who is more susceptible to this effect?
Not everyone reacts the same way. Research suggests that people with an authoritarian or neurotic personality, or people with a higher than usual need for approval, show the Barnum effect more readily. Some work further links this effect to schizotypy traits below the clinical threshold.
It should be said clearly that these are factors that increase sensitivity to the effect, not a psychological verdict. The Forer effect itself is a general cognitive feature of human beings, not a sign of pathology. The degree to which it shows varies between individuals, and recognizing the mechanism is the best way to reduce its influence.
How can you test this effect yourself in ten minutes?
The simplest way to test it is to reproduce Forer's own experiment with two people. Step one, take a passage of general personality description, perhaps a passage from Forer's 13-sentence description or one you write yourself in the style of "sometimes", "at times", "you have unused potential". Step two, give that passage to person A and say it is their personal analysis, asking them to score it from 0 to 5. Step three, give exactly that passage to person B, also saying it is B's own, and ask them to score it. Step four, compare the two scores. If both score it highly, you have reproduced the Forer effect.
Another way is to test it on yourself. Read a general description and ask yourself: "Is this sentence true of me, and is it true of most people I know?". If the answer to the second part is yes, then the feeling that it is true of you is not evidence that the description was personalized. This is precisely the core point of the Forer experiment.
Four questions to ask yourself when reading a personality description
- Does this description say it is based on my own data, or was I merely told so?
- Do its sentences contain the phrases "sometimes", "at times", or an opposing pair that covers every possibility?
- Is the proportion of positive sentences unusually high?
- If I gave this to a friend, would they also find it true of them?
The key point: self-validation is not validation
Michael Birnbaum, professor of psychology at California State University, Fullerton, remarks that the Forer effect is used by mentalists and psychics in cold reading, as well as by some television figures who claim expertise in depth psychology and assert that they can diagnose a guest's psychological problems within minutes. He says that genuine psychologists are horrified by this practice, but that they have not spoken out against it forcefully enough in public.
Birnbaum sums up the lesson of the Barnum demonstration in the sentence: "Self-validation is not validation". He advises readers not to be fooled by a psychic, a fake therapist, or a fake faith healer using this trick, but to be skeptical and demand evidence.
Denis Dutton wrote in 1988 that it is regrettable that academic psychology has not paid more attention to cold reading technique, since successful cold reading practice is precisely the foundation for most belief in supernatural abilities in society today. He called for analysis of the very techniques and methods that skilled cold readers use, rather than focusing research only on students.
What does the Forer effect have to do with astrology and personality tests?
The Barnum effect can partly explain the widespread acceptance of certain beliefs and practices regarded as mystical, such as astrology, fortune telling, aura reading, and some kinds of personality test. This does not mean that all personality tests are worthless, but it is a warning that a description that makes the reader feel it is "true about me" is not necessarily constructed specifically for that person.
The Myers-Briggs Type Indicator is a topic still under debate in research circles regarding its accuracy and value. The point to hold on to is the distinction between the subjective feeling of accuracy and objective evidence of accuracy. The Forer effect lives precisely in the gap between those two things.
Related phenomena
The Barnum effect is a specific example of the "acceptance phenomenon", the general human tendency to accept almost any false personality feedback. A related and more general phenomenon is subjective validation. Other concepts often mentioned alongside it include confirmation bias, the apophenia fallacy (seeing patterns in random data), and the Pollyanna principle, the tendency to use or accept positive feedback words more often than negative ones.
Does the Forer experiment really prove that astrology and fortune telling are false?
No. The Forer experiment shows that people readily accept a general description, true of almost anyone, as a description personal to themselves. It does not by itself refute astrology or fortune telling; it points out that the feeling that something is "true about me" is not sufficient as evidence. To reach a conclusion about astrology or fortune telling, separate tests are needed, kept apart from subjective feeling.
This effect is therefore an explanatory tool, not a verdict. It helps explain why a vague pronouncement still makes the listener nod along, but it says nothing about whether a particular birth chart is accurate or not. Keeping those two things distinct is what matters when reading any description of yourself.
