[ajross]

Yes, you certainly did get smarter between 6 and 25. Children's brains are still developing until late puberty. All sorts of cognitive tasks show development, including short term memory, working memory, etc... It's absolutely not just factual learning taht is happening.

[liber8]

Agreed (and studies show that brains are developing until at least 18, possibly into early 20's).

But why? Most people seem to think that this rapid development is, for the most part, genetically driven. Doesn't it seem strange to reach this conclusion when we don't even have a solid idea about what "intelligence" really means (other than "performs above X level on some cognitive test")?

[AngryParsley]

>But why?

For the same reason that people grow taller until they're in their late teens and get stronger until they're in their early 20's.

>Most people seem to think that this rapid development is, for the most part, genetically driven.

It is. Depending on which studies you cherry-pick, the heritability of intelligence is somewhere between 0.5 and 0.8. The best way to be smart is to choose your parents.

>Doesn't it seem strange to reach this conclusion when we don't even have a solid idea about what "intelligence" really means (other than "performs above X level on some cognitive test")?

People can argue about the definition of strength just as easily. Who is the strongest person in the world? Is it whoever can bench-press the most weight? What about leg press? Clean-and-jerk? Maybe some average of these measures? Maybe we want to factor the person's weight in as well. While "strength" doesn't always have a precise definition, it's usually pretty easy for us to tell weak people from strong ones. It's the same when people talk about intelligence. The precise definition varies, but there are lots of correlating ways to measure it.