I wonder if the study controlled for the selection bias inherent in the decisions of males of various ages to reproduce and in their preferences for mates. Presumably, 50 year-old men are not procreating with women their age. Do older men choose younger, but dumber women to mate with? Do dumber men end up having children later in life? Are 50 year-old men worse parents?
While I was reading this article I felt almost the exact same thing - the whole article feels like bad science because they present the conclusion that "many scientists believe that genetic mutations that build up in the sperm of older men are to blame." Presumably, the only thing this study has shown is that lower intelligence is correlated with older fathers but the cause could be any number of factors like what you said or even, for example, that people with lower intelligences are predisposed to postpone having children.
Basically, thanks Freakonomics for bringing correlation/causation to my mind every time I read an article like this.
Pick a list of successful people you believe are intelligent. Uncheck those who don't have brothers/sisters. Then look if they're an older/younger kid in the family. I've done the exercise out of curiosity and it appears the article is correct: most famous programmers were older brothers.
That risks conflating intelligence, IQ, fame, programming ability (and programming affinity), and general organizedness into one. You may be right -- but we have zero idea to what degree.
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.
You're absolutely right. While I don't hold a PhD in phycology or neurology or child development I don't believe in superior/inferior intelligence or natural talent: take this as a totally unscientific gut feeling that I'm sticking to, unless an undeniable evidence (something other than surveys or Einstein brain scans) emerges.
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.
Interesting. I happen to gut feel nurture >>>>>>>>>>>>> nature, but I think nature plays a part too. It seems unlikely to me that we all have slightly different bodies, and those bodies are heritable to some extent, but our brains are wired consistently the same and/or not heritable.
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.
I lean on the nature side. I also feel like this is the dogma in "formal" neuroscience; it is hard for nurture to maintain favor when all you look at is whether some gene turned on or some phenotype expressed.
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.
Then you run into problems of other parents since they will have their own parenting style which will affect the IQ.
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.
Numerous studies have been done on siblings and twins who were raised separately. The IQ correlation between hereditary siblings is strong, that between twins is overwhelmingly strong and that between adopted siblings is almost non-existent past adolescence.
This is entirely anecdotal, but I'll jump in on this topic:
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.
