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Findings on birth order and IQ prompt debate

Benedict Carey

New evidence that eldest children develop higher IQs than their siblings has intensified the debate over two of the most stubborn questions in social science: What are the family dynamics that enhance intelligence? And can they — and should they — be changed?

The new findings, from a landmark study published on Friday last, showed that eldest children had a slight but significant edge in IQ — an average of three points over the closest sibling. And it found that the difference was not because of biological factors but the psychological interplay of parents and children. Predictably, the study set off a swarm of Internet commentary from parents, social scientists, and others, speculating about what in families could enrich one child’s intellectual environment more than others.

“Anyone with siblings wonders about this,” said Sue Monaco, 51, of Delaware, who has two sons and five siblings. She was one of about 150 readers who posted questions on Friday to a New York Times Web forum about the stu dy.

Researchers acknowledge that few of the family variables affecting intelligence are well understood, and some argue that peer influences are eventually more significant. But studies suggest that two elements are important during childhood: the perceived role a child has in the family; and the apparent benefit a child receives when he or she tutors someone else, like a younger sibling.

Well before entering the high school hothouse of geeks and jocks, children who grow up with siblings get tagged with labels: The airhead, the klutz, the whiner. And then there is the serious one, little Mr. or Ms. Responsible, who most often is the eldest, psychologists have found. Studies suggest that other family members tend to consider the eldest the most conscientious of the siblings, more likely to achieve academically. At least for some firstborns, that role may be self-fulfilling.

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 IQ tests.

Something else is at work, Professor 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. “The younger one is asking questions, and challenging meanings and explanations, and that will contribute to the intellectual maturity of the older one.” (Only children receive the benefit of more parental attention but miss the opportunity to tutor a younger brother or sister.)Ms. Monaco, who has two sons in their 20s, said her oldest was expected to help his brother from an early age. “He was a teacher to his brother, and he has grown up to be a more intense thinker; he’s studying business management,” she said. Parents who recognise the different niches that their children fill can enhance the family’s intellectual environment by exploiting each child’s expertise, researchers say. “Given the evidence we have on this, I would as a parent encourage late-born siblings to take on teaching roles, with other siblings or other children,” said Paul Trapnell, a psychologist at the University of Winnipeg.

Professor Trapnell compared this process to the so-called jigsaw approach used in classrooms, in which complex projects are divided up and each child becomes an expert in a particular task and instructs the others.

Younger siblings often have something more to pass on than the tricks of their favourite hobby, or the philosophy behind their social charm. Evidence suggests that younger siblings are more likely than older ones to take risks based on their knowledge and instincts. It is important to keep in mind, too, that the new study found average difference in IQ; the scores varied widely from family to family. In many families, younger brothers and sisters eventually took the lead in IQ.

Moreover, experts have long noted that while even slight differences in IQ score can be important for some, the test measures a narrow set of skills. Excessive attention to it can blind parents to the diverse and equally rich expertise that later-born children usually develop. The best way to react to the news, some psychologists said, is to relax. — New York Times News Service

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