June 21, 2007

Birth order and IQ

A large Norwegian study finds a small effect.

My published articles are archived at iSteve.com -- Steve Sailer


Anonymous said...

Not to disparage the Norwegian researchers, but I question the widespread applicability of a study that focused on the offspring of parents in a homogeneous society. Norwegian parents are likely to possess enough common traits to make measurable in their offspring minor influences such as birth order. I suspect that a study of American children would demonstrate that in cases where the genetic background of the parents is dissimilar, minor influences (such as birth order) would disappear.

Anonymous said...

Here is the link to a "science" article:


Anonymous said...

Many years ago I read a book on Birth Order. Many interesting things came from it, but here are just two:

1. Of the 25 first astronauts (at the time of printing), 23 were first-born.

2. Of all the different permutations a family can take, that which consists of a family having 2 children, both boys, about 3-5 years apart in age put more people in therpay BY FAR.

The reason was that the two children were close enough in age for them to compete but far apart enough for the older child to always dominate.

Anonymous said...

An alternative explanation for this effect might simply be that older parents are more likely to have children who possess harmful mutations or are affected by congenital defects that reduce intelligence.

If this study's conclusions are valid, it might have implications for the Flynn Effect; namely, reduced family sizes would result in higher mean IQ scores.

Anonymous said...

I'm a first born and I approve this study.

Steve Sailer said...

I haven't had a chance to read this study, so is reduced IQ a "younger brother" syndrome or a "younger sibling syndrome"?

With male homosexuality, men with older brothers have a slightly higher chance of being gay, but not men with older sisters. Ray Blanchard's theory is that this is caused by antibodies that mom's body generates in response to male fetus's male hormones in her womb. Over time, the effect apparently builds up causing a number of issues like greater chance of homosexuality.

So, can somebody take a look at this?