>>271552786
Well yeah, dumb people are less able to evaluate if themselves, so they won't be as good at seeing their own failures. Their confidence stays high until they walk into traffic. 

If you know someone is dumb then you should put less weight into the attracted-to-confidence-because-success-indicator thing, but you probably find dummies unattractive anyway, so you're already doing that. If you use confidence as a indicator someone is dumb, you're probably dumb too. Smart people can recognize dummies the normal way and don't have to sabotage the value of other useful signals to do it.