Birth Order and IQ
There has been much discussion, the past few days, about a new Norwegian study showing that birth order affects IQ scores. Oldest sons tend to score higher on IQ tests than later sons, but the difference appears to be because of how children are raised, not biology. Later-born sons whose older brothers died in infancy show similar IQs to those who were first-born.
So what's to be made of this? Probably not much. The difference was 2-3 IQ points, which is pretty much meaningless. But that doesn't stop people from drawing whatever conclusions they like. I particularly laughed at the quote from the UC-Berkeley expert in the AP article I linked, above, stating that eldest children were probably smarter because they tutored their younger brothers and sisters. This idea that kids benefit from tutoring each other is often expressed in education circles, because it lets harried teachers use gifted kids as unpaid teaching assistants and claim it's good for them.
But anyway -- if I had to guess, I'd say the tiny difference is because parents have more time and energy to pay undivided attention to their first born children during the first 2 years of their lives. An acquaintance of mine recently confessed that with his first daughter, he was reading stories to her in the womb and, presumably, with even greater frequency after birth. The second daughter got no in-the-womb story sessions. Likewise, with my baby, I spend a reasonable amount of time showing him different patterns and objects, exposing him to different sounds, etc. I can't imagine doing as much of this if I had a 2-year-old shrieking around the house. But if that's the reason for the difference, the study's conclusion is heartening to me. If all that difference in time and energy only adds up to 2-3 IQ points, it would take a lot for good intentioned parents to really mess their children up.