Some readers of our first post added some long, thoughtful and often angry commentaries. One main source of anger: employers giving 'personality tests' that seemed frivolous and/or irrelevant to the job. Readers reported tests asking about one's favorite color, how you cross your legs and what kind of animal you'd like to be. Why are such tests out there? Why are they popular? The answer is something called the Forer effect.
The Forer (or Barnum) effect is also known as the subjective validation effect or the personal validation effect.The expression, "the Barnum effect," seems to have originated with psychologist Paul Meehl, in deference to circus man P.T. Barnum's reputation as a master psychological manipulator. Psychologist B.R. Forer found that people tend to accept vague and general personality descriptions as uniquely applicable to themselves without realizing that the same description could be applied to just about anyone.
Forer gave a personality test to his students, ignored their answers, and gave each student a copy of a page that he had randomly selected from a horoscope book. He asked them to rate the evaluation from 0 to 5, with '5' meaning the recipient felt the evaluation was an 'excellent' assessment and '4' meaning the assessment was 'good.' The class average evaluation was 4.26. That was in 1948. The test has been repeated hundreds of times with psychology students and the average is still around 4.2. In short, Forer convinced people he could successfully read their character. His accuracy amazed his subjects, though his personality analysis was taken from a newsstand astrology column and was presented to people without regard to their sun sign.
How can you tell whether a personality profile is a P.T Barnum trick or a genuine psychometric instrument? Here's the test:
Imagine that you have a group of 12 people, each born on a different day in a different month. You then write each person's birthday on a piece of opaque paper and lay the 12 sheets on paper on a table face down. What are the chances that an individual can go to the table and pick the sheet with their own birthday on it? The answer is one in twelve, or 8.3 percent of the time. If you turn the papers right side up, people will pick their own birthday 100 percent of the time. Something which genuinely differentiates individuals should be selected more often than chance dictates. If you obtain horoscopes based on the 12 individuals' birth dates and put them face up around the table, the chances of the right one being selected are about the same as chance.
Now let's think about the kind of information a business would like to have about a prospective employee: his or her behavioral traits in the workplace. If you have a group of 12 people who have been reliably observed to have strongly different behavioral styles and give them one of the 'parlor game' personality tests, the chances of picking out their own report will be (as you would expect) nearly chance. A genuinely scientific test, however, will make assertions that will not apply to everyone in the world and the chances of picking one's own report out of twelve differing reports will be far above chance.
In other posts, we'll look at the science behind some of the tests that do give valuable and accurate results. If you want to ask questions in advance, post them as comments to this article. Or share experiences you may have had with either very powerful tests, or very dumb tests.
-=John Loven
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