Firstborn Get the Brains

Dekortage writes "Eldest children have higher IQs than their siblings, according to a recent study by Norwegian researchers. The study focused on men, particularly 'on teasing out the biological effects of birth order from the effects of social status,' but indicates that the senior boy in a family (either by being firstborn, or if an elder brother died) has an average IQ two or three points higher than younger brothers. As noted in the New York Times coverage, 'Experts say it can be a tipping point for some people — the difference between a high B average and a low A, for instance... that could mean the difference between admission to an elite private college and a less exclusive public one.'"

Comments

the teacher

[Speare]

It wouldn't surprise me, as the act of teaching while learning tends to reinforce the learning. The oldest kid, whether consciously or not, ends up demonstrating any new knowledge and capabilities to the younger kids in the family or neighborhood.

Subtle IQ differences

[John3]

Interesting study and the stats seem to back up their theory. However, the IQ difference is so subtle that I wonder how much difference it really makes. Does an IQ of 102 really provide that much of an advantage over someone with an IQ of 100?

Based on personal experience raising two daughters, I'm sure that part of the reason the second child lose two points of IQ is that the parents just start getting tired. :) Your first child gets all your energy, and you try out interesting things, go to interesting places. The arrival of the second child means you now divide your time and energy and so the second child will tend to lose out. When the first child leaves the house the second child is nearly full grown anyway.

I wonder if they looked at homes where the children were very far apart in age? Suppose one child was 10 when the second child was born. By that time the parents are comfortable with the progress of child #1 and might devote more time to child #2 than they would have if the children were only a year or two apart.

Data points

[garoo]

Just to commit a plural of anecdotes error:

Einstein was the older sibling, as I think is Stephen Hawking, Isaac Newton, Johannes Kepler and Robert Oppenheimer - doing fine so far. On the other hand (and merely AFAIK), Blaise Pascal was the second son, Dirac was the second son, Niels Bohr was the second of three, Faraday appears to have been well into the plurals and Ernest Rutherford was the fourth-born child. Van de Graaff had three older brothers, all of whom were into football rather than physics.

All of which may go to suggest only that seventh sons don't necessarily need to sell their scientific calculator and resign themselves to brainless toil quite yet.

Social environment affects intelligence

[yali]

Dunno about IQ (other than it being lower than firstborn's) but I recall a study showing that if you have an older and a younger brother you are more likely to be gay...

Such evidence does exist, but for different reasons. In the case of sexual orientation, the effect is because successive births change the hormonal environment of the womb. But for IQ it was social rank, not biological birth order. If someone had an elder brother who died young (making them biologically a secondborn but socially a firstborn), they looked like a firstborn.

This leads to an important point. All of the discussion has been about birth order, but the scientific importance of this study is broader than that. What's really exciting about this study (IMHO) is that it provides compelling evidence that family social environment affects intelligence. This flies in the face of recent arguments by Judith Rich Harris (who has been enthusiastically received by Steven Pinker, the Freakonomics guys, and others), claiming that parents don't matter.