Sure :3
Probably, yea. MBTI received even more attention that Jung's work because MBTI did that very thing: simplified. It condensed Jung's work and left out all the important bits in order to give it a marketable, quick-and-easy form. =/
But if typology reaches hard-science, then it would grow even more popular than that. It would be studied academically and be in the books.
He does mention mirrored brain hemisphere, yes. I think his study showed that left-handed people had a 50% chance of showing their brain activity mirrored.
Mm, I'm not sure what is being asked. You mean to suggest that the plasticity of the brain and what region is used for what process - makes it so that we can't fully map out/correlate brain regions with functions?
If so, I think the way to answer that is that what he observed were brain patterns - some region specific while others are not. For instance, the "christmass tree" pattern involves the whole brain. Very rapidly, all sections switch their frequency & amplitude up and down sporadically - seemingly randomly - for however long they are focused on the task of brainstorming. This christmas-tree pattern was seen in all the test subjects/students who identified as
ENTP/ENFP/INTP/INFP, and not in any others.
Other patterns use four sections, such as the "circuit". In fractions of a second, four sections light up, each immediately after the other, right before executing a decision or task. This pattern was seen in the ENxJ personality types.
Other regions are more static. For instance, while working out math problems some students displayed zero activity in all regions except for one - the one he used to work out the math - and so on. It's really interesting, I hope you do watch it.
He limited the age range of his test subjects to between 20-25, in order to reduce the number of variables present in this preliminary study. Yesh, it'd be interesting to see how specific brain types develop in age.
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Though I suppose that's a secondary question, firstly he is trying to understand whether types exist
at all - which is a great point of skepticism still.
One by one, every assertion made by Jung/MBTI will have to be tested. For instance "does type really stay static during your lifetime?" or "are the 16 hierarchies really ordered the way the theory (somewhat arbitrarily?) says they are?". So I suppose the answer to that is, we honestly don't know yet.