Personally I think I am very good at reading people's internal state. But I also am aware that I can be wrong. Reading someone who is very quiet for example can be hard and more prone to error.
When I talk with someone I often do assess how much turn taking they do, particularly with a stranger. When I'm really engrossed in a conversation or I'm with a good friend I can sometimes turn off this assessment.
Final point - the article was a great read. I'd have been really interested in their views on gender differences in communication (there can be differences).