Is Birth Order Meaningless?

New research presents some surprising info when it comes to sibling chronology, IQ, and personality. (Photo: CBS)

Conventional wisdom has it that firstborn kids are brainier, more conscientious, and worth giving the car keys to because they’re naturally more responsible (think Prince William). Second- and later-born children, on the other hand, tend to be creative, fun-loving, and less likely to ace the SATs (sorry, Harry).

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But an exhaustive new study blows the lid off these stereotypes. While the study did find that firstborns had higher IQs and different personality traits than their young siblings, the differences were so small, they were pretty much irrelevant and undetectable.

“People seem to believe that firstborns share one personality type and later-born kids have another, and smaller studies support this,” Rodica Damian, coauthor of the study and professor of psychology at the University of Houston, tells Yahoo Parenting. “We wanted to find out if it’s really true, or if parents just expect to see these traits, so birth order becomes a self-fulfilling prophecy.”

So Damian and University of Illinois psychology professor Brent Roberts designed a study involving 377,000 high school students. They evaluated the students’ IQs and personality traits, then controlled for factors that can influence these, such as socioeconomic status and the total number of siblings in the family.

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The result: Firstborns racked up a one IQ-point advantage over their later-born siblings, which is statistically irrelevant, says Damian. The study was published online on July 16 in the Journal of Research in Personality.

They also determined that birth chronology did have an effect on personality—oldest kids really did turn out to be more extroverted, conscientious, and agreeable. But differences when compared to later-born siblings were too tiny to make a difference or notice.

One advantage that makes the new study more precise is that Damian and Roberts evaluated each child’s personality and intelligence using a variety of measurements; they didn’t simply ask the study subjects or their parents to describe them. If you ask a parent if their first-born is more intelligent, they might say yes because they buy into the stereotype, says Damian.

Another factor the study took into account was age. “Firstborns are considered responsible because they are, since they are older,” says Damian. “It’s the same with thinking a later-born child is fun-loving. She’s younger, so of course she will be more fun-loving when compared to her older, more mature sibling.”

The takeaway for parents, Damian says, is to be mindful that many personality traits come with age, not birth chronology. And to not pressure kids into future plans based on where they fall in the family lineup. Without realizing it, parents might steer a first-born away from an artistic career, or they may invest less in a second-born’s education because they assume she’s not as academically- minded, says Damian.

“A child’s experiences and genetic makeup play a big role in shaping who they are,” says Damian, but the study demonstrates that birth order does not.

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