New Study Suggests Firstborns Are Smarter
The difference in I.Q. was small—an average of three points higher in the oldest child than in the next sibling—but the researchers consider it significant. Why should that be so? Perhaps, one theory went, the mother’s body was somehow attacking the later offspring in utero. Maternal antibody levels do increase with each successive pregnancy. But there’s no evidence that this leads to differences in intelligence, and the new study in Science, based on records from nearly a quarter of a million young Norwegian men, strikes down the antibody hypothesis....