Too stupid to know they're stupid.

[xoxoxoBruce]

The first part, about the stupid don't know their stupid, seems self evident. Who would make bad decisions knowing they were bad?
The second part, about mediocre people who are uneducated or not smart enough to know they're mediocre, is believable too.
But when they get into anosognosia they're talking about people that are physically damaged... they were using patients with anosognosia as an example of having the same result as the first two groups. I think they should have quit there. By the time they got to the fifth part, I'm not convinced anosognosia is a good correlation. He talks about some anosognosia patients who are apparently aware of their limitations but unconsciously and selectively choose to block them.