Personality tests claim to provide accurate descriptions of who we are. Before they came along, it was fashionable to study the shape and size of the skull as an indication of character and mental ability. People thought how you interpreted ambiguous images of inkblots would reveal your personality characteristics. Lombroso’s phrenology and Rorschach’s inkblot tests were long ago discredited as diagnostic devices, yet the Myers-Briggs Type Indicator lives on.

Isabel Myers and Katherine Briggs were two well-meaning amateurs not formally educated in any scientific discipline.

They began creating their Type Indicator in their homes before doing any extensive scientific research, instead of the other way around. Then they shopped around for a veneer of legitimacy and found Carl Jung. A psychiatrist, Dr. Jung had created his stereotypes as points of orientation, not as the solutions claimed by Myers and Briggs. During WW2, their MBTI was used to identify the sort of war-time jobs that would be “most comfortable and effective” for women.

Circular Reasoning.

People use the MBTI because it’s valuable and it’s valuable because people use it. Just like a perpetual motion machine, its popularity is interpreted as an indication of its accuracy and utility, which leads to wider use and less inclination to question its foundations. Today, the MBTI is  administered two million times a year.

Why your company’s HR department uses Myers-Briggs.

It is a prepackaged solution that is easily administered and analyzed by people with no training in measuring human behavior, which describes HR quite nicely. Their lack of training means they are unaware of the MBTI’s shortcomings and limitations. Another lure is that the 4-day, certification course promises instant expertise. Unlike the undergraduate degree that must be earned before entering a graduate program, no background in Psychology, testing, or psychometrics is required for admission.

The reason both horoscopes and the MBTI descriptions appear accurate is the Barnum Effect –  the tendency for individuals to view generally flattering and sufficiently vague statements as highly accurate descriptions of themselves.

Two spurious assumptions of the MBTI.

• One assumes that personality type is inborn and never changes. Most don’t know that half of the people who take the test again fall into a different category than they did the first time. Are you the same person today as you were as a middle schooler? Of course not.
• Another assumes categories are mutually exclusive, meaning one or the other, but never both. Test results do not distinguish between someone who is 99% introverted from someone who is 51% introverted. If the MBTI measured intelligence, everyone would be either stupid or brilliant. You already know most people fall in the middle somewhere, so mutually exclusive categories don’t even make sense.

No middle ground.

The biggest problem is that test takers are forced to choose one of only two options – thinking and feeling, for example. Those who choose 11 thinking and 9 feeling items are deemed to be exactly the same as those who choose 20 thinking and zero feeling items. This is beyond unlikely.

There is no scientific evidence that the MBTI measures anything of value. Many well-informed people agree it provides a ridiculously limited and simplified view of human personality, a concept known to be  very complex – just like yours.

For a famous sailor’s take on personality types, watch this 7-second video.