03/28/2008 02:44 am ET Updated Nov 17, 2011

Which Sibling Is Smarter? New Study On Birth Order And Brain Power Fuels Debate, Rivalry

The new findings, from a landmark study published Friday, showed that eldest children had a slight but significant edge in I.Q. -- 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'.

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