The Forer Effect
The Forer effect is a term used to describe the tendency of people to interpret general statements as being accurate for them personally, even when they are not. Specifically, when people are given a random personality assessment and told it has been written for them personally, they will tend to rate it as highly accurate.
The term is named after American psychologist Bertram R. Forer (1914-2000), who conducted an experiment in 1948. Forer gave a personality test to a group of students, then asked them to rate the test results for accuracy (i.e. how well the test results described their unique personality). Students rated their results on average at 85.2% accurate. What the students didn't know was that they had all been given fake results—each had been given the same personality assessment, which was as follows:
You have a need for other people to like and admire you, and yet you tend to be critical of yourself. While you have some personality weaknesses you are generally able to compensate for them. You have considerable unused capacity that you have not turned to your advantage. Disciplined and self-controlled on the outside, you tend to be worrisome and insecure on the 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 also pride yourself as an independent thinker; and do not accept others' statements without satisfactory proof. But you have found it unwise to be too frank in revealing yourself to others. At times you are extroverted, affable, and sociable, while at other times you are introverted, wary, and reserved. Some of your aspirations tend to be rather unrealistic.
This assessment was created by combining snippets of horoscope readings. It demonstrates how easily people can be led to believe that their personality is being accurately assessed when it clearly is not. This is relevant when studying the work of practitioners who use personality assessment as part of their trade.
For example, astrology is based largely on personality assessment. People believe it works because they believe the assessments offered by astrology are reasonably accurate. However another well-known experiment showed otherwise: In 1979 French statistician Michel Gauquelin asked 150 people to rate a horoscope reading for how accurately it described their character. 94% rated the horoscope as accurate. The horoscope readings were fake—all 150 people had been given the horoscope of a serial killer named Marcel Petiot.
The Forer effect is also known as personal validation fallacy or the Barnum effect (after the P. T. Barnum quote "we've got something for everyone").