SAN DIEGO — Birth order within families has long sparked sibling rivalry, but it might also impact the child’s personality and intelligence, a new study suggests. First-borns are typically smarter, while younger siblings get better grades and are more outgoing, the researchers say.

The findings weigh in on a long-standing debate: What effect if any does birth order have on a person’s life? While numerous studies have been conducted, researchers have yet to draw any definitive conclusions.

The results lend support to some previous hypotheses - for instance, that the eldest sibling tends to have higher aptitude. But the study also contradicts other proposed ideas, for example, that first-borns tend to be more extroverted.

The findings shed light on the influence of sibling relationships, which often receives less attention compared with that of the mother-child or father-child relationship, said Tiffany L. Frank, a doctoral candidate at Adelphi University in Long Island, N.Y., who lead the study.

They also suggest some inherent differences between siblings exist, differences that might arise no matter what parents do. ‘While parents might want to treat each child equally, it’s almost impossible,’ Frank said here at the 118th Annual Convention of the American Psychological Association.

Sibling rivalries

Most previous studies on the […]