The Myers-Briggs test has become something of a pop culture phenom, which is a shame because it was actually developed with a very specific purpose. During World War II, women worldwide were flung into the workforce, many of them for the first time. Not only did they lack the practical knowledge — but also the required self-knowledge—to assess what they could do to help the war effort in the absence of so many young men. We think of Rosie the Riveter; images of beautiful young women whose beaus and husbands are fighting in the war, working in factories and wearing pants for the first time in their lives.

This had, of course, a major cultural impact: women were outside the home, visibly so, and many of them discovered that they knew very little about working on an assembly line — not just in the physical sense, but in the emotional sense. Outside of relating to the nuclear family, which they had been well-raised to wrangle, their self-knowledge of interpersonal skills outside the home was limited.

An author by the name of Katharine Cook Briggs read up on her Jungian psychology and, essentially, came up with the typology test as a way to help women entering the workforce understand what kind of work they would be best suited for. A woman’s score on the MBTI gave her insights into how she experienced the external world as well as her own internal environment. It addressed her reaction to conflict, her morals and intrinsic motivations and helped guide her towards work that she would not only be likely to excel in but that she might also enjoy and feel fulfilled by.

Briggs’ daughter, Isabel Myers, was also an author and the two of them fine-tuned the test and began presenting it academically to psychologists. The problem was, while both women were highly educated and well-read, neither of them had any psychoanalytic training, and therefore, the test was seen to lack validity. When they realized they couldn't pawn it onto psychologists, they instead ventured into the corporate sector — and began advertising it not so much as a psychological test, but more an aptitude test that businesses could use with potential employees — most specifically, women entering the workforce for the first time.

By the 1960s, the MBTI took on a more generalized use and since more people had access to it, statistics began to be collected about the relative occurrence of various types in the general population.