> - MBTI theory is complex. An order of magnitude more so than something like the big 5. This also makes it more useful / predictive.

If it's more predictive, where are the studies showing it? Big 5 has some fairly good studies (and of course lots of terrible no good very bad studies[1]) that show e.g. conscientiousness predicts future academic performance.

> - MBTI theory posits internal thinking processes. These cannot be directly observed. Most experiments don't even discuss this, they just rely on the unreliable type indicators (questionnaires) blindly. Of course they don't find significant results

Can they be indirectly observed? Are there studies doing so? Otherwise this is just another non-falsifiable prediction.

> - Most experiments that do discuss theory, discuss the simpler (and IMO plain wrong) trait model of MBTI that is more similar to the big 5 model. Under this model, MBTI terms (e.g. Introversion, Feeling) apply to people. The more sophisticated and plausible model (that almost all MBTI practitioners and theorists work with) applies these terms to Cognitive Processes (i.e. thinking mechanisms), and only then describes people in terms of which thinking processes they prefer (use more often/easily).

I am (possibly unfairly) regarding this as a no-true-scottsman. You may be right, but I've seen enough of "Oh, sure that MBTI wasn't good becaus X/Y/Z", but my special MBTI A/B/C is better!" type comments that I lack the motivation to continue investigating them. In addition, this is somewhat irrelevant to TFA because the MBTI types are exactly what the internet is obsessed with.

> - The theory itself is still often described in terms of Jargon that came from Jung. This makes it hard to understand what is being described, even though it very similar to other theories in mainstream academic psychology/philosophy.

Agreed. It doesn't help that a lot of Jung's theories are just absurd.

>> If we were to do the MBPI thing with IQ, then everyone under 100 would be "stupid" and everyone over 100 would be "smart" which is silly because obviously someone with a 99 IQ is much more similar to someone with a 101 IQ than either is to someone with an 85 or 115 IQ.

> This is actually a misconception. An MBTI type really describes "A baseline trajectory of preferences towards different mental processes across their lifetime". So:

> - Individuals will differ (due to life circumstances, experience, etc). The MBTI claim, is that modulo life experience, this individual would develop in this way.

This is probably not testable, and I'm not sure how it's useful to say "If you didn't have any life experience you Alice would be like X and Bob would be like Y"; if MBTI measures something that will have a net effect on life outcomes, than it should be revealed in the data.

> - A given individual will vary how they think over their lifetime (in a predictable way!).

> - A given individual will vary how they think over short time scales (minutes) in a random (unpredictable) way. But that over longer time scales patterns will emerge.

It seems likely that these statements are true, but I disagree that there is any reason to believe that MBTI will predict these patterns very well, and particularly not better than Big 5 (as your GP comment states).

> Notably, dual-process theory has the same binary structure, and a LOT of experimental evidence that the bimodal distribution holds up in practice.

Which makes me ask why MBTI doesn't have such experimental evidence about bimodal distributions showing up.

1: https://en.wikipedia.org/wiki/Sturgeon%27s_law Though I think in the soft sciences the number is closer to 99 than 90...