All Hallows’ Eve. The night of the year when we psychologists, just like normal people, like to sit around the fire, toast marshmallows, and swap scary stories while we sip our pumpkin-spice martinis.
We’re made of stern, rational stuff. And scary stories – like that one that ends with “…but the call was coming from INSIDE THE HOUSE” – are treated with the scepticism that they deserve.
No. For a psychologist there are only three really scary stories, and they end like this.
One. “…and the evidence was there. Astrology was proven.”
Two. “…so it turns out that correlation does imply causality after all.”
But the third, the most terrifying of them all…
“… and so, the Myers Briggs was shown to be a perfectly valid and robust measure of personality.”
I shudder just typing those words. Let me explain why.
You may be aware that the Myers-Briggs Type Indicator (MBTI) is a personality test widely used in business. It’s based on on Carl Jung’s theory of psychological types. It measures four dimensions of interactional and thinking styles, and classifies individuals on those dimensions. For each dimension you are given a letter: extraverted (E) or introverted (I); sensing (S) or intuitive (N); thinking (T) or feeling (F); and judging ( J) or perceiving (P). You end up with one of sixteen four letter codes (such as ESFJ, ENFP, INTP, and ISFJ) that is intended to describe behaviors, attitudes, and decision-making styles.
People cannot be sorted into simple types or categories.
And that’s the first problem with it: people cannot be sorted into simple types or categories. Not easily anyway. Classifying people into one of 16 “types” oversimplifies what we know about personality.
The majority of personality research demonstrates that there are more – perhaps way more – than 4 different dimensions of personality. And instead of being at one end or the other on each dimension (like extraverted vs. introverted, or sensing vs. intuitive), each dimension is actually a continuum. You can be slight introverted, really extraverted, or any point along the scale. In fact, most people are a little bit of both, depending on the situation: someone may have the tendency to exhibit introverted behaviors in the office but exhibit extraverted behaviors at a party.
There’s little to no evidence of validity.
Quite reasonably, you might expect a personality test that is in common use to have plenty of evidence to demonstrate its validity. Or simply put, the test should measure what it is intended to measure. But numerous studies have evaluated the MBTI and found little to no evidence of validity (Boyle, 1995; Pettinger, 1993; Sipps, Alexander, & Friedt, 1985). This is because, for example, the theories it is built on do not hold and it has poor psychometric properties. Scientists now largely agree that the MBTI should not be used due to its lack of supporting validity evidence.
The MBTI does not reliably predict important behaviors.
When we say that there is no validity, it means that almost no evidence exists to demonstrate that the test is capturing the four ‘dimensions’ that supposedly classify individuals. To put it more bluntly, “the patterns of data do not suggest that there is a reason to believe that there are 16 unique types of personality,” say Pittenger (1993). The same paper also points out that a large body of research exists to show that the MBTI does not reliably predict important behaviors (Pittenger, 1993).
Granted, some studies have claimed that the MBTI is a valid tool, but on close inspection these claims were often based in an unscientific understanding of psychometric validity (Boyle, 1995; Pettinger, 1993).
I’ll spare you the details of how we assess validity: that’s a scary story for another Halloween. If you can’t wait, you can refer to the American Educational Research Association (AERA), American Psychological Association (APA), and the National Council on Measurement in Education (NCME), the Society for Industrial-Organizational Psychology (SIOP) along with other psychometric experts who have agreed upon a set of Standards, Principles, and guidelines that should be followed when assessing validity.
There are personality assessments out there with much stronger validity evidence.
In recent scientific review articles, expert scientists that specialize in the study of personality have taken to not even mention or acknowledge the MBTI when discussing the history of personality (e.g., Chernyshenko, Stark, & Drasgow, 2010; Revelle, Willt, & Condon, 2011). Further, if scientists used the MBTI to measure personality and submitted their research paper to a top-tier journal, the paper would get rejected on the basis of poor measurement and in turn poor research methods; the study would lack validity. That’s not because of professional jealousy (although who wouldn’t want some of that sweet, sweet MBTI money) but because there are personality assessments out there with much stronger validity evidence.
If you want to learn more about modern day theories of personality, check out the Personality Project, a collection of websites and resources devoted to the academic study of personality. And if you want to contribute to research and learn about your own personality you can take a personality test based in the most up-to-date personality science.
By Ben Hawkes and Dr. Nikki Blacksmith
American Educational Research Association, American Psychological Association, & National Council on Measurement in Education. (1999). Standards for educational and psychological testing. Washington, DC: American Educational Research Association.
Boyle, G. J. (1995). Myers-Briggs Type Indicator (MBTI): Some psychometric limitations. Australian Psychologist 30, 71-74.
Chernyshenko, O. S., Stark, S., & Drasgow, F. 2011. Individual differences: Their measurement and validity. In S. Zedeck (Ed.), APA handbook of industrial and organizational psychology. Vol. 2. Selecting and developing members for the organization: 117-151. Washington, DC: American Psychological Association.
Pittenger, D. J. (1993). The utility of the Myers-Briggs Type Indicator. Review of Educational Research, 63, 467-488.
Revelle, William. 1997. “Extraversion and Impulsivity: The Lost Dimension?” In The Scientific
Study of Human Nature: Tribute to Hans J. Eysenck at Eighty, ed. Helmuth Nyborg, 189-212 Amsterdam: Pergamon/Elsevier Science.
Schmitt, N. (2014). Personality and cognitive ability as predictors of effective performance at work. Annual Review of Organizational Review and Organizational Behavior, 1, 45-65.
Sipps, G. J., Alexander, R. A., & Friedt, L. (1985). Item analysis of the Myers-Briggs Type Indicator. Educational and Psychological Measurement, 45, 789-796.
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