I don't see how this finding would conflict with the Jungian model. Care to explain this thought?
As far as dopamine level variance goes, different people have different brain chemistry, that's one of the things that makes us who we are. Here's an article (hopefully not the same one you've referenced) about the differences between introvert and extrovert brain chemistry that explains it pretty well: http://suite101.com/article/extrover...version-a24464
I do not agree with this article in that it says introverts are typically not leaders. It also says that introverts avoid thrilling roller coasters, which is strange to me because I'm a total adrenaline junky
Anyway, it could be that because extraverts tend to think outside themselves more, their brain chemistry reflects their thought processes in dopamine production. Dopamine is associated with many types of thought processes besides external pleasure, although its relationship to this type of experience does have a very causal
link to the extraverted personality. Dopamine could be involved in sensing and interpreting the outside environment. Elevated dopamine levels in extraverts could be a sign of the basic way they tend to think, not just of how much they like external pleasure and rewards. As stated in the article, they are desensitized to dopamine, so they need more of it to feel the same way as an introvert feels with less. If dopamine is involved in external sensing, this could explain why extraverts tend to build up tolerance for it.