If you have been reading idealawg for a while, you may recall that I am not a big supporter of self-report tests. For those of you interested in personality testing, I recommend The Cult of Personality Testing: How Personality Tests Are Leading Us to Miseducate Our Children, Mismanage Our Companies, and Misunderstand Ourselves by Annie Murphy Paul. In the book's chapter on Myers-Briggs, Paul describes one reason why I am skeptical of personality tests.
But what about all those "aha" moments? Could thousands of Myers-Briggs devotees have been deceived? Once again, science's conclusion is blunt: yes, they could. Psychologists explain the test's overwhelming popularity with reference to what they call the "Barnum effect." The phenomenon is named after the famous showman P.T. Barnum, who liked to say that a circus should have "a little something for everybody." MBTI [Myers-Briggs Type Indicator] personality descriptions, it's suggested, also offer "a little something for everybody": enough hedged statements and vague commonplaces to allow any individual to read one and think, "Yep, that's me."
The first research on what would later be termed the Barnum effect was conducted by psychologist Bertram Forer in 1949. After administering a personality test to a group of subjects, Forer handed back the results—but the participants' ostensibly individualized personality descriptions were actually all the same, lifted from an astrology book Forer had purchased at a newsstand. ...
Participants were then asked how accurate they found their profiles. On a scale of 0 (poor) to 5 (perfect), the subjects gave their reports an average of 4.2, with more than 40 percent awarding a flawless 5. Subsequent research has demonstrated other intriguing aspects of the Barnum effect: that people are often unable to tell whether the results they're given are derived from a test they've taken or made out of whole cloth , for example, and that given a choice, we actually prefer the invented feedback. A finding with particular relevance for the Myers-Briggs is that individuals are more likely to endorse positive accounts of themselves, a phenomenon scientists call the "Pollyanna principle."
Paul also devotes a chapter each to the Rorschach, the MMPI, and other tests revealing "the surprising and disturbing story behind the tests that claim to capture human nature." This book will get you thinking.
Note (added September 5, 2010): The Myers-Briggs Personality Test: A critical look at the world's most popular psychological metric, the Myers-Briggs Type Indicator (Skeptoid).
Image credit: clarita.