Glad you asked! Here’s how I look at personality tests, Myers-Briggs included. The first question is are they capturing something accurate about reality? Or, is it true that people do really have these sorts of characteristic differences, or does the test create the appearance of differences that do not exist? I think the answer here is that they do help point out real differences. They aren’t “natural kinds.” In other words God didn’t create the Myers-Briggs categories, but humans found them useful to uncover some aspects of the complex reality he has created. If you take the Myers-Briggs you’ll likely find descriptions and videos that capture how you see the world pretty well (my description) and even help to explain some of your behaviors to yourself. But the difficulty is that all personality tests tend to produce these sorts of results. I think it is likely that human beings are complex enough that there are multiple ways to draw commonalities to the surface, and each way of slicing these commonalities contributes to a clearer overall picture of how we work. So, I’d be careful investing too much significance into just one type of personality test. Think of them as sets of lenses that are bound to distort reality, but also help you to notice things you wouldn’t have.
But the second question is more important, are these helpful, if if so, how much? One angle into this is comparing how the two most popular tests are used, the Myers-Briggs and the Big Five Inventory. The Myers-Briggs is very commonly used within business organizations because its results aren’t very prejudiced against a particular type. The results are sometimes framed as if each type has strengths and weaknesses. When we did it with our church we watched these videos, which now require a paid subscription. The guy on the video talked about each personality type’s superpower and kryptonite. It was genuinely helpful. Psychologists, on the other hand, give the Big Five Inventory (BFI), which is much more helpful for assessing and addressing mental disorder, but is correspondingly less neutral about traits. People who are high in neuroticism, for example, are generally unhappy. The Myers-Briggs helps business to leverage people’s strengths and weaknesses; the BFI helps psychologists to figure out how people go wrong. In each case, the generalities that the tests provide bring “insight” or self-knowledge that help people know how to lean into strengths and fix weaknesses.
Third, the tests are most destructive when people use them as an excuse for not taking responsibility and for blaming others. Introverts have often recognized that America is prejudiced toward extroverts. They are right about this, but it not very helpful to know this if you can’t fix it. It tends to create victims. Being a victim is a horrible place to be psychologically because you develop a hatred to your imagined oppressor. These tests can also be used to box people in, to make quick judgments about what people are capable or incapable of. (As a general rule, fixing these sorts of things is accomplished by a combination of raising awareness/action of/toward systemic issues and taking personal responsibility in spite of them.)
Finally, these tests capture only characteristics of a person at a point in time. People’s personalities do change somewhat. I usually say for mental illness that as a rule of thumb genetics account for about 40% of it, and experience/choices about 60%. With personality, it seems that genetics accounts for more than 40%, but still is not totally determinative. Genetics accounts for the basic range of possibilities for a person’s personality. Epigenetics refers to how this range of possibilities actually expresses for a person, which aspects of the genetic make up actually get activated. Take Molly for example. I think genetically her personality is more likely to be extroverted, and she tests as a borderline extrovert. However, she functions much more like an introvert. Because of the anxiety of her childhood she is much more sensitive to noise and stress than she otherwise would have been and is much more like an introvert in some ways (introverts are more sensitive to noise generally). I used to test INTJ and now test INFJ. I think I have grown more empathetic over the last ten years, especially walking through suffering with Molly. So, I wouldn’t invest too much significance into categories as determining your life or personality. They are useful for self-understanding and growth, but they do not capture everything about us or set fixed limits on our abilities to change.
Hope that’s helpful.
P.S. If you take the Myers-Briggs, I’d love to know how you score. Also, try out the BFI since this is the standard test for psychologists. It might be interesting to compare the results of the two tests.