Four letters, held loosely

Katharine Briggs was a mother in Washington who had been quietly sorting the people in her life into types for years when, in 1923, she read Carl Jung and found he'd done it first. Her daughter Isabel Myers turned it into a questionnaire during the Second World War to help women entering the workforce find jobs that fit them. Sixteen types, four letters each. It became the most-taken personality instrument in the world.

It is also the most criticized, and I'll tell you why, because you'll hear it. The research says people are not sixteen types; they sit on lines. And about a third of people get a different type when they retake it. We seat it anyway, with its descendants, because fifty million people speak this language and you should know what they mean when they say "I'm an INFJ" at a dinner party.

The four letters. E or I: where you recharge, with people or alone. S or N: whether you trust the facts in front of you or the pattern behind them. T or F: whether you decide by logic or by values and people. J or P: whether you like things settled or open.

Its weakness is real. Its strength is also real: the vocabulary is everywhere, and it describes preference, not ability, so nobody walks away with a bad result. There is something kind in an instrument where every answer is a good one.

This month's use for it is narrow and useful. Take the free version. Note your four letters. Then set them beside the Big Five scores from day twenty-one. E lines up with extraversion, N with openness, F with agreeableness, J with conscientiousness. If they disagree, trust the Big Five; it's the better instrument. If they agree, you have two mirrors saying the same thing, and that's worth a line in the log.