Firstborns, get ready to throw this in your siblings' faces: A massive study of 377,000 high school students—the "biggest in history looking at birth order and personality," author Brent Roberts says—shows those born first tend to have higher IQs and different personality traits compared to their younger brethren. But, and it's a big but, the study finds firstborns' IQ is just one point higher on average, which, in terms of how it affects people's lives, is ultimately meaningless, reports Science Daily. The distinctions among character traits are also "infinitesimally small," though firstborns were found to be slightly more extroverted, agreeable, and conscientious, and less anxious than their siblings. Basically, "you're not going to be able to sit two people down next to each other and see the differences between them. It's not noticeable by anybody," Roberts says.
The lesson for parents? "Birth order probably should not influence your parenting, because it's not meaningfully related to your kid's personality or IQ," says the study's co-author. The study, which controlled for details like economic status and the number of siblings, was among the first to compare children with those of different families, rather than just their own siblings. One issue with earlier "within-family" studies is that "the oldest child is always older," as Roberts puts it, so they're more likely to show the positive traits (like responsibility) that come with age. More news on the birth-order front: A working paper Quartz reported on this week suggests a correlation between birth order and health: It found firstborns are more likely to be overweight or obese, while laterborns are more likely to smoke. (Find out why it pays to be the middle kid.)