Intelligence, as measured by IQ tests, is at least 50% heritable and positively correlated with better socioeconomic outcomes in education, income, health, and crime. It may seem obvious that you want your kids to be smarter. Satoshi Kanazawa makes an intriguing point in his book The Intelligence Paradox that it is not so simple:
Yes, intelligent people make better physicians, astronauts, better scientists, and better violinists, because all these pursuits are evolutionarily novel.
But these are all the unimportant things in life...They do not make better friends, they do not make better spouses and partners, and they do not make better parents, precisely because these are things our ancestors have done for hundreds of thousands of years on the African savanna.
His basic idea, hotly disputed by other evolutionary psychologists, is that intelligence applies to novel human activities, so simple but very meaningful and important tasks like friendship, social exchange, mating, and parenting are at best orthogonal to such intelligence. He argues that more intelligent people reject the simplistic solutions offered by common sense as applied to these time-tested arenas even though it is usually the correct solution. Intelligent people are tempted to apply analytic reasoning instead of feelings, unnecessarily complex ideas simply because their intelligence allows them to entertain such complex ideas. "Clever sillies" as Bruce Charlton called them.
He notes that more highly intelligent people have no kids at all, surely an evolutionary dead end. He cites a study of a bunch of gifted kids who had IQs higher than 155, and years later found they were clearly more successful as adults in scientific and academic achievement, but were less successful in parenting and marriage. Idiocracy seems to have been one of the more prescient movies every made.
He makes the point with this exchange between talk show host Larry King and Stephen Hawking:
Larry King: What, Professor, puzzles you the most? What do you think about the most?
Stephen Hawking: Women
Larry King: Welcome aboard.
The book is a nice, quick read filled with fun tid-bits like the fact that the frequency of excercise is significantly positively associated with general intelligence, a fact that I will use in Calvinist fashion to motivate me (ie, I must work out because I am more intelligent!).