The Myers-Briggs - a possible validation through our evolutionary past

While the Myers-Briggs personality test has become unfashionable in scientific circles it is booming on the internet on sites like Quora and Reddit and even on dedicated YouTube channels. A lot of young people turn to online tests and sites and are generally relieved when they learn that they are not “weirdos” or “aliens” but have a rare personality type like “INTJ” or “INFP” instead. I do the tests with my students, and students as young as 16 tell me that they already have found out their MBTI (Myers-Briggs Type Indicator) in their quest to understand themselves.

While only 30 years ago great scientists like Stephen J. Gould had no qualms about using the MBTI for scientific research, nowadays most psychologists and scientists will only recognize the Five-Factor Model (Big Five/OCEAN) or the revised model with six factors (HEXACO). The reason: the Big Five model was derived using mathematical methods, whereas the MBTI was created mostly on intuition. However, the MBTI isn’t that different from the OCEAN and the traits show a high degree of correlations.  

Any theory of personality must ultimately be able to show the evolutionary origin of the single traits. The oldest human personality trait is probably the T/F (testosterone - estrogen) dimension (in OCEAN the Agreeableness dimension), which characterizes more “male” or more “female” traits. Both men and women can be T or F, even though T is more common in men and F in women. This personality trait also shows physically in digit ratio, amount of facial hair, and via traits such as a more angular and boney or a softer, rounder face.

The trait “Conscientiousness”  or J in MBTI is probably related to early farming (dominant hormone serotonin) and  “Openness” or N (dominant hormone oxytocin) in MBTI to hunting and gathering (read more here). So, three personality traits can be explained by the type of subsistence economy our ancestors practiced.

The most famous personality dimension, i.e. “introversion/extroversion” cuts across all four personality groups. I have hypothesized elsewhere that introversion has its origin in hunter-gatherer female mate choice in order to maintain their alloparenting way of life. Extraversion might be connected to pastoralist female mate choice, as the dominant hormone in SP types is dopamine, which also plays an important role in extraversion. Out of all extraverts, the SPs are usually the most extroverted type (ESFP nicknamed "The Entertainer"), followed by SJs, NFs and NTs.