I'm seeing a fundamental misunderstanding in both the article and a lot of the comments here, that to me seems closely related to the "some people have no inner

I'm seeing a fundamental misunderstanding in both the article and a lot of the comments here, that to me seems closely related to the "some people have no inner voice" / "some people can't visualize things" findings: People making the assumption that how you act defines whether you're an introvert or an extrovert because only the external expression exists, not the internal state. And so all their examples reveal they think introvert/extrovert refer to how social a person is in the moment, instead of what it actually is - a measure of how draining (or not) social interactions are. You really can't tell if someone is an introvert or extrovert in one instance in a setting, only in what happens later - it's totally possible to be a social introvert, for example, it just means you need alone time later to recharge before you can go again. When not given a chance to recharge it can come off in various ways depending on the person - often people describe it as getting tired, I've also seen snippiness, and I tend to get a headache.