Myers-Briggs personality tests are widely used, produce appealing results and seem rigorous. There’s just one problem: they have little grounding in theory or practice.

The Force is strong with this test

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The Myers-Briggs typology is probably the most popular form of personality testing ever devised. It is widely used in the corporate and educational worlds. An article from the Guardian reports that there are “companies that make a point of putting employee MBTI profiles on the doors to their offices, so people entering know how best to engage with them.” It has evolved into a multimillion dollar industry. And it has achieved enough cultural salience that things like this chart exist:

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My personality

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According to this online version of the Myers-Briggs test, I am INTJ (Introverted iNtuitive Thinking Judging) like Emperor Palpatine. And to be fair the supposed traits of this personality would be useful for trying to rule the Galaxy:

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INTJs are introspective, analytical, determined persons with natural leadership ability. Being reserved, they prefer to stay in the background while leading. Strategic, knowledgable and adaptable, INTJs are talented in bringing ideas from conception to reality. They expect perfection from themselves as well as others and are comfortable with the leadership of another so long as they are competent. INTJs can also be described as decisive, open-minded, self-confident, attentive, theoretical and pragmatic.

But does my being an INTJ really tell you more about me than my being a Gemini? Would an employer administering a MBTI test to a job applicant be anymore reasonable than consulting their horoscope?

Consistency and clarity

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For all its other deficiencies, astrology does at least have the benefit of consistency. I was born in mid-June and therefore will forever more be a gemini.
By contrast, I’ve not always been a Palpatine like INTJ. On previous occasions I’ve taken the test I’ve been Yodaesque INTP. As my one time spirit animal might say: troubling implications has this. If your result is going to be a reasonably useful indicator for long term decisions like career choices you’d expect some consistency in the results.
My flip from Jedi master to Sith lord comes about because of a structural flaw in the test. It work by categorising people according four dichotomies: Extraversion-Introversion, Sensing-Intuition, Thinking-Feeling and Judging-Perception. These are then combined to produce an overall classification. The problem is that what the test presents as distinct categories are actually a scale. Rather than being say a sensor or an intuitor, we all combine features of both.
Myers Briggs works a bit like a weather forecast that instead of telling you the temperature just tells you whether it’s hot or cold. That would be terrible. It wouldn’t make any distinction between a cool day and a snow blizzard. Plus during spring and autumn, you’d constantly be switching between the two categories as small changes in temperature took you over the dividing line.
This is essentially what happens with my test. I don’t have a clear preference for judging vs perceiving, so tend to come out near the borderline. Therefore, it doesn’t take much variation to push me over the boundaries between the categories. Now you might think this is just me and my awkward personality refusing to be easily categorised but in fact that’s pretty standard. As on most scale people congregate near the median, and extreme results are rare. Therefore, the drawing of a sharp distinction is especially inappropriate.
So in terms of clarity and consistency, astrology is our clear winner. So at this early stage it’s 1-0 to Astrology.
Theoretical underpinnings
As Sheldon explains in the above clip from the Big Bang Theory, astrology has no real theoretical basis. How about myers-briggs?
Well, it should raise our scepticism that neither of its creators Katharine Cook Briggs and her daughter, Isabel Briggs Myers had a professional background or academic training in psychology. They based their work on the Swiss psychoanalyst Carl Jung’s book Psychological Types.
Jung is a troubling source. Rather than a psychologist or psychiatrist he was a psychoanalyst. This was one of disciplines that Karl Popper branded as a paradigm example of an unempirical pseudoscience driven by anecdotes and conjecture rather than rigorous testing. Actual attempts to test it tend to fall down. As for Jung in particular many of his ideas were rather strange.

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Apart from his alchemy-fuelled notion of the collective unconscious, we have to thank Jung for terms and ideas like New Age, the age of Aquarius and synchronicity, the ‘scientific’ study of coincidence. Frankly, it is all rather fluffy and daffy.

So we have a draw: both horoscopes and  Myers-Briggs come up short on the theoretical front. So it’s still 1-0 to the astrologers.

Putting it to an empirical test

Astrology fails this test so spectacularly that we need not discuss it further.
Myers Briggs does not do much better.
Consider this finding by a researcher at the University of Indiana:

In summary, it appears that the MBTI does not conform to many of the basic standards expected of psychological tests. Many very specific predictions about the MBTI have not been confirmed or have been proved wrong. There is no obvious evidence that there are 16 unique categories in which all people can be placed. There is no evidence that scores generated by the MBTI reflect the stable and unchanging personality traits that are claimed to be measured. Finally, there is no evidence that the MBTI measures anything of value.

Or this:

A number of studies have found that personality types said to be most appropriate for certain professions, notably nursing or teaching, turn out to be no more prevalent among that profession than among the general population. The Army Research Institute commissioned one such study to determine if the MBTI or similar tests could be used to improve the placement of personnel in different duties, and firmly concluded that the results of such tests did not justify their use in career counseling.

However, this round has to go the Myers-Briggs test because the following research while almost entirely rejecting it does not do so completely:

Consistent with earlier research and evaluations, there was no support for the view that the MBTI measures truly dichotomous preferences or qualitatively distinct types, instead, the instrument meastires four relatively independent dimensions. The interpretation of the Judging-Perceivmg index was also called into question. The data suggest that Jung’s theory is either incorrect or madequately operationalized by the MBTI and cannot provide a sound basis for interpreting it. However, correlational analyses showed that the four MBTI indices did measure aspects of four of the five major dimensions of normal personality The five factor model provides an alternative basis for interpreting MBTI findings within a broader, more commonly shared conceptual framework.

So we’ve come to a draw overall: 1-1.

For fun but nothing more!

I concede that Myers-Briggs has a certain intuitive appeal. It feels right to me that the two Star Wars characters I should be most like are Yoda and the Emperor! And as Myers-Briggs typology is so well known it is ideal for exercises like classifying fictional characters.
However, something of such flimsy scientific merit has no place in serious matters like choosing careers, degree subjects or partners.
It is only good when it is treated as a bit of fun. Rather like horoscopes.