It stirred a lot of interest worldwide last week, along with discussion, jokes, and maybe a few hard feelings among members of individual families: The finding by Norwegian researchers that first-born siblings have higher IQs than the sisters and brothers who follow them.
Now, comes the inevitable second wave of analysis: If this is true- and it is based on ten years’ worth of intelligence tests and family records from the 1960s and 70s- what are the underlying reasons?
Psychologists say that filling the role of the responsible firstborn, while important to academic achievement, still does not account for eldest children’s higher average scores on intelligence tests. Robert Zajonc, a psychologist at Stanford University, has argued that in fact having a younger sibling or two diminishes the overall intellectual environment for eldest children — who otherwise would be benefiting from the rich vocabulary and undivided attention of parents.
This helps explain why, under the age of 12, younger siblings actually outshine older ones on I.Q. tests.
Something else is at work, Dr. Zajonc said, and he has found evidence that tutoring — a natural role for older siblings — benefits the teacher more than it does the student. “Explaining something to a younger sibling solidifies your knowledge and allows you to grow more extensively,” he said.
By that reckoning, the oldest child becomes a kind of “senior partner” with his or her parents in bringing the younger siblings along toward success in school, and eventually responsible adulthood. Rather than being a reason for jealousy, maybe it’s a reason for gratitude: to an older sibling who helped, or a younger one who helped with a first-born child’s own education and confidence.
And that IQ advantage? The study says it’s only three points. As older children age and start losing brain cells, the younger ones won’t have far to go in catching up. And they, in the end, will be the smarter ones.