More intelligent people are more likely to be alcoholic and suicidal. Animals forced to act smarter suffer stress and die younger.
Forming neuron connections may cause harmful side effects. It is also possible that genes that allow learning to develop faster and last longer may cause other changes. “We use computers with memory that’s almost free, but biological information is costly,” Dr. Dukas said.
My guess is that relatively high intelligence is a social choice, and requires the expenditure of energy - or you could say it is a higher stress choice, a higher risk choice in terms of life fortune. I think even getting a high mark on an IQ test is about subjecting yourself voluntarily to stress, or if you like exerting greater mental effort. There probably are also limits to intellect imposed by genetics - but as I say, if high intelligence was an unequivocal good, there'd be more smart people about.
Also - why do smart people do dumb things?
(these all quoted from the blog linked above)
- Hubris. Pride to the point that you no longer feel shame, no longer believe that you are subject to public opinion, and no longer need to fear “the gods.” Examples: Gary Hart’s involvement with Donna Rice that ended his run for the presidency and the Dennis Kozlowski’s (Tyco) $2 million toga party.
- Arrogance. From the Latin word arrogare: “to claim for oneself.” Arrogant people believe they have claim to anything and everything they want--they are “entitled” to it. King David, for example, felt entitled to the wife (Bathsheba) of one of his soldiers. Modern day King Davids feel entitled to corporate jets and an entourage to tell them that their keynote speech rocked.
- Narcissism. Self absorption to the point that you are blind to reality. The world only exists to provide you gratification. Examples: Richard Nixon and Watergate; the Clintons and Whitewater—really just about every politician and CEO who falls from grace.
- Unconscious need to fail. If you think failing is hard, try winning. The questions that go through people’s minds when they they are on the doorstep of success are: Do I really deserve to win? Do I want the pressure of constantly having to win in the future? Can I really handle success? Perhaps this explains why professional athletes still take performance enchancement drugs even after watching their colleagues get busted.
Still, it's addictive isn't it? Once you've tried it, you can't go back, you have to keep on trying to get smarter, and of course failing.