The Barnum effect is the tendency for an individual to personalize a generalization that could apply to anyone. It is a type of cognitive bias that was characterized by psychologist Bertram Forer as being a logical fallacy of personal validation.
In the late 1940's, Professor Forer gave his psychology students a demonstration of how easily a client and psychologist could be misled by a poor evaluation tool. The instrument Forer used for demonstration purposes was a personality test that asked each student to provide information about his or her hobbies, what they liked to read, their personal characteristics, job duties and role models. Students were told that the test creator would review each student's answers to create a personalized personality profile.
After students received their individualized profiles, they were asked to rank the accuracy of the test as a diagnostic tool by using a Likert scale of 0=very poor to 5=excellent. The class ranked the test's usefulness as a diagnostic tool as 4.26, on average. What the students did not know was that they had all received the exact same profile, which consisted of 13 general statements taken from an astrology book.
- 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.
The Barnum effect relies upon the logical fallacies appeal to vanity and appeal to authority and exploits people's willingness to personalize flattery if they believe it comes from a credible source. In advertising, the effect is often used to encourage an individual to think that a product, service or advertising campaign has been designed specifically for a select group of special people. A popular example of how the Barnum effect has been used effectively in advertising is L'Oreal's "Because you're worth it" campaign for hair color.
Forer's experiment remains a popular tool for teaching psychology students and human resource managers about the challenges inherent in selecting personality test instruments. The practice of referring to the Forer effect as "the Barnum effect" is generally credited to psychologist Paul Meehl, author of "The Dynamics of 'Structured' Personality Tests." Phineas Taylor Barnum was a 19th-century American showman and entrepreneur who studied human nature and effectively used his knowledge to bring in customers and increase revenue. In addition to being remembered for his marketing skills, P.T. Barnum is known for inventing the three ring-circus and is often associated with the quote "There is a sucker born every minute."