Basically, thanks Freakonomics for bringing correlation/causation to my mind every time I read an article like this.
They good control it by looking at IQ relationships of brothers potentially.
Two parts of your statement. 1. most famous programmers were older brothers: interesting statistic. But 2. it doesn't support the older-father-lower-IQ hypothesis.
In my previous post I just stated an observation but I forgot to add that I don't hold it as an explanation nor proof. In this particular case I believe that older siblings enjoy more freedom and have an opportunity to grow up faster since parents become pre-occupied with younger brothers/sisters, thus older kids grow up being more independent.
But I do over to the nurture side of the equation more - the interesting part on more freedom and growing up for older siblings is interesting. Also supporting your idea, older siblings often take on more responsibility in family affairs too.
But, there is an area where it may be impossible to show either way, and you have a battle of religion. To see why this is the case, consider inherited fear responses (I forgot the actual term for this). You can, for example, probably train a goose to not fear an eagle-shaped shadow. There would be a measurable change in neuronal wiring, because the fear response previously paired to the pattern recognizers of eagle-shaped shadows is now inhibited or diverted. If this works, it is "nurture."
But to turn it around, the fact that you could re-train the goose would imply that plasticity was part of the equation. This is "nature." Then, there are parts where plasticity is simply never going to be part of the equation (without some extreme bioengineering): you cannot teach a modern goose to read, period.
So, to rephrase: it is possible to interpret all "nurture" phenomenon under an all-nature framework: it's simply a distinction of whether you are born with plasticity for certain domains of learning. This difference, which you can validly call nature vs. nurture, is meaningful in many contexts, but in my opinion is not so much a dichotomy than different ways of looking at the same thing.
I'm not all about predeterminism though; the important task to figure out what, why, how, and when circuits are plastic.
I wonder if there's a big difference of the IQ in twins. If there is then the IQ difference of 3 in the article may not be all that significant.
The ideal case would be children from the same parents that lived in the same town, went to the same schools, participated in the same activities, had similar friends, and a whole list of other factors. It would also be convenient to have there be more than 2 kids to see the quantitative meaning of "older"
This may just be an indication of a first time parent spending a lot more effort on the first child or just having the resources to do so. During the early years the IQ of the first child is developed while there are fewer resources for the later children.
On the other hand, younger parents may just be starting out and have fewer resources/experience to help them raise the child.
You can also take a look at grandparents - younger parents will have a more active set of grandparents which may be contributing to this IQ boost as well.
Too may unknowns here but an interesting topic.
http://en.wikipedia.org/wiki/Inheritance_of_intelligence#Fam...
I have twin sisters (identical). Both of them are highly intelligent (go to Ivy league schools), but one has a slight "edge" on the other.
Growing up, they did everything together- the only difference between the two is that the slightly "dumber" one, I used to put down a lot more and make fun of (I got along with my other sister a little better).
It's funny how the little things you do when you're young (we have a great relationship now) can affect things when you're older.