I recently learned about Forer effect or how people can take general statements and make them their own. In a classic experiment , Forer asked his students to fill a personality test. A week later, he gave his analysis back to each student and made them rate its accuracy on a scale of 0 (poor) to 5 (perfect). The analysis were so targeted that only one out of 39 students rated the results lower than 4.
As it turned out, the results were not good, they were perceived as good. Everyone received the exact same excerpt from an astrology book. Students believed the analysis were targeted because they were made of universally valid statements:
A universally valid statement, then, is one which applies equally well to the majority or the totality of the population. A universally valid statement is true for the individual, but it lacks the quantitative specification and the proper focus which are necessary for differential diagnosis.
Some universal statements taken from Forer’s paper are:
You have a great need for other people to like and admire you.
You have a tendency to be critical of yourself.
Some of your aspirations tend to be pretty unrealistic.
One of Forer’s conclusions is that people are really bad at assessing information about themselves. Denis Dutton explains very nicely how this weakness is used by mentalists to deceive people with cold reading.