Initially, Briggs had designed her questionnaire to identify solid marriage partners, but after the Second World War, her daughter repositioned it to place people in the right jobs. The MBTI does what all profiling systems do: asks batteries of questions and organises the answers into types which are supposed to define your personality. And yet the test has no basis in clinical psychology, though it is deployed by most Fortune 500 companies, many universities, schools, churches, consulting companies, the CIA, the army and the navy.
The MBTI test-retest validity lies below statistical significance, meaning that if you test someone more than once, you are likely to get different results. More worrying is that the questionnaire poses binary questions, asking, for example, whether you value sentiment more than logic or vice versa. The question assumes that there is a simple answer to this question, absent of context. Yet in real life, preference is highly contextual: I value logic when purchasing car insurance; I may value sentiment more when choosing to play with my son. Binaries always simplify, often to the point of absurdity, and they polarise what are often complements.
Excerpt from: Uncharted: How to Map the Future by Margaret Heffernan