Birth Order and IQ

I “clipped” this off of CNN for a couple reasons. One is to comment on the fact that I first saw this research months ago – CNN is pretty slow sometimes – okay, slow most of the time – at reporting new research. Second, even though there was a statistically significant difference between IQ scores of 1st, 2nd, and 3rd born children, there is only a difference of 3 points between 1st and 3rd. That doesn’t really mean anything in real life. Also, this is significant in part as a result of the huge same size – 200,000+. Additionally, the subjects all were male. There are other limitations pointed out in the CNN article.

We shouldn’t be so set on statistical significance (I worry about it in my research, of course). There is internal and experimental validity and then there is ecological validity. Intelligence research means very little without good ecological validity.

clipped from
But the debate over the impact of birth order gained new urgency this summer when the results of a new study were announced: Firstborns’ IQs tend to be higher than those of their younger siblings.
Does that mean later-born kids are destined to be less accomplished and successful? Studies like this don’t tell the whole story — and neither do birth-order stereotypes. Here’s how to bring out the best in each child:
Norwegian scientists analyzed test results and birth data from more than 241,000 military conscripts and found that oldest children had an average IQ of 103, second children came in at 101, and third-borns were at 100.

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