I looked into this a bit a while ago, and what I've learned basically boils down to: The MBTI does measure aspects that roughly correlate with other, scientifi

I looked into this a bit a while ago, and what I've learned basically boils down to: The MBTI does measure aspects that roughly correlate with other, scientifically accepted measures (such as the Big Five, where the classic MBTI basically is only missing the 'neuroticism' aspect, which is added as another dimension in some variants of the MBTI). As such, I believe it does have some validity on its own. But the big problem is that the MBTI simply dissects every one of its dimension into two halves and your 'type' is based on which respective halves you fall into. But if your personality dimensions are well-calibrated, you would expect most people to fall exactly into the middle of the scale, and so it's pretty silly to then fully assign them to the camp they just barely end up in. This still kind of works for people that very clearly are at one end of the spectrum in all the dimensions, but it doesn't really work well for the majority of people. All that is to say, I think if there was something like the MBTI that also had a neuroticism axis, and would use three intervals (of roughly equal 'expected size' among the general population) per dimension, it would be a lot more accurate. But at that point, you'd basically just have a clustering of the Big Five into 243 'types' -- which makes it a lot less handy than the neat '16 personalities' the MBTI offers.