Another dimension to consider is that some people perform well at some specific things, but not all nonspecific things. And also that performance varies with si

Another dimension to consider is that some people perform well at some specific things, but not all nonspecific things. And also that performance varies with situation-to-situation and self-perception varies with mood/time. In reality, DK is an overall impression tendency rather than a strict rule... such is the nature of squishy, fungible social "sciences;" reality is messier than a numeric IQ result.