>> introverts find interactions with other “draining”
> I'm pretty sure this is bullshit.
Both me and my SO are more introvert than not.
We've come to the conclusion that one of the core reasons it's so draining for us is that we puts a lot of thought into interactions and conversations, even superficial small talk ones.
At least in our experience, those who appear more extrovert seem to do less of that. They don't seem to reflect over all our actions, or everything we say. Some of it, or at certain times, sure. But seemingly not to the same degree.
If that is the case, then it is more draining, because we exert more mental effort.
> Level of drain = lack of trust in that person X overall level of anxiety
Speaking for myself at least, anxiety has nothing to do with it, nor lack of trust. I don't feel any anxiety striking a random conversation with someone in a bar or with a family member at home. And when I have a random conversation with someone in a bar, it doesn't matter if I trust them or not, because the topics are almost never intimate. With my family members I know I can trust them, so that's moot as well.
But both conversations can be quite draining, and at least for me, I suspect it has more to do with what I described above.