The study, which was led by Brent Roberts and Rodica Damian, both of whom are researchers at the University of Illinois, involved an examination of 377,000 high school students. Researchers asked the students questions about their personality and intelligence.
Researchers found that first-born siblings tend to have slightly higher intelligence (one more IQ point) and scored higher on some personality traits, including extroversion, agreeableness, and conscientiousness. However, researchers said the differences in these scores were “infinitesimally small.”
Even after controlling for family economic status and number and ages of children, there was virtually no personality or IQ difference between older and younger siblings, the University of Illinois researchers found.
In the end, Roberts says it’s virtually impossible to tell people apart based on birth order. “You are not going to be able to see it with the naked eye,” Roberts said. “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.”
So, what’s the end message here? Damian says it should result in parents treating all of their children equally, no matter their birth order. “The message of this study is that birth order probably should not influence your parenting, because it’s not meaningfully related to your kid’s personality or IQ,” she said.
