From the BBC:
The harsh truth, however, is that greater intelligence does not equate to wiser decisions; in fact, in some cases it might make your choices a little more foolish. Keith Stanovich at the University of Toronto has spent the last decade building tests for rationality, and he has found that fair, unbiased decision-making is largely independent of IQ. Consider the “my-side bias” – our tendency to be highly selective in the information we collect so that it reinforces our previous attitudes. The more enlightened approach would be to leave your assumptions at the door as you build your argument – but Stanovich found that smarter people are almost no more likely to do so than people with distinctly average IQs.
That’s not all. People who ace standard cognitive tests are in fact slightly more likely to have a “bias blind spot”. That is, they are less able to see their own flaws, even when though they are quite capable of criticising the foibles of others. And they have a greater tendency to fall for the “gambler’s fallacy” – the idea that if a tossed coin turns heads 10 times, it will be more likely to fall tails on the 11th. The fallacy has been the ruination of roulette players planning for a red after a string of blacks, and it can also lead stock investors to sell their shares before they reach peak value – in the belief that their luck has to run out sooner or later. More.
Actually, there are many more successful life forms that lack individual intelligence than there are independently intelligent ones.
Maybe intelligence is like good taste? It may or may not pay, but if you experience it, you don’t want to lose it.
See also: The human mind, the skinny