I'm not talking about writing the "clever code" that nobody understands (including the coder 6 months afterward)—that's a symptom of the hubris-laden self-proclaimed intelligent programmer the original author is confused about. A genuinely intelligent programmer might early in his career write that esoteric crap as well, but soon learns that nobody—including himself—can understand it after a while. And that is the difference: the intelligent programmer stops doing that immediately while the pseudo-intelligent guy can't stop himself, worlds without end.
I've been in a variety of shops over the past 20 years or so where new kids come in, thinking they're all that and a bag of chips, and systematically replace smart, well-engineered, and working modules with their new ones that will now take years to become as robust, and never be half as elegant.
They do this because they won't take an afternoon to spend the time to read and understand the original code.
Intelligence isn't wholly a matter of genetics—some of these earnest kids do eventually learn better in spite of their natures. They spend enough time with the real good guys to figure out they're not one of them, and then they start trying to figure out why. The fakes go on for years and years writing the worst stuff imaginable and even after shown direct evidence of their incompetency will refuse to reclassify themselves. They start getting defensive, paranoid, thinking they're the poor misunderstood artist. Whatever.
Coders who aren't willing to get into someone else's code to see the "whys" beyond the "hows" are the people I specifically exclude from my projects.