It appears that the age old belief regarding the differences in the personalities among siblings, which are often described in relation to birth order, is now faced with a new study that contradicts such notion. The study, titled "The associations of birth order with personality and intelligence in a representative sample of U.S. high school students," was published in the Journal of Research in Personality. According to its lead authors, Rodica Ioana Damian and Brent W. Roberts, from the University of Illinois at Urbana-Champaign, their study aims to correct the belief that the birth order among siblings in a family has a significant effect on the personality and IQ of a child.
Taking into consideration 377,000 high school students - the biggest sample size to date, according to National Post, Damian and Roberts found that no notable difference could be detected among siblings in terms of their personalities and IQs in relation to their birth order. "This is a conspicuously large sample size...It's the biggest in history looking at birth order and personality," Roberts revealed, according to Consumer Affairs.
The research revealed that first-born children exhibited a single-point advantage in their IQ, according to Metro. In addition, these children are observed to be typically more "extroverted, agreeable and conscientious" in general compared with those born later. However, the study also revealed that the differences are so miniscule that the birth order seemed insignificant.
"In some cases, if a drug saves 10 out of 10,000 lives, for example, small effects can be profound," said Roberts. He added, "But in terms of personality traits and how you rate them, a 0.02 correlation doesn't get you anything of note."
He went on to say, "You are not going to be able to see it [the differences] with the naked eye. 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." This is further expounded by his co-author. "The message of this study is that birth order probably should not influence your parenting," Damian continued to explain, "because it's not meaningfully related to your kid's personality or IQ."
The same details were disclosed in the Results section of the study. Roberts and Damian wrote, "In sum, although the direction of some of the effects supported the hypothesized relation between birth order and both personality and intelligence, we would conclude that the magnitude of the effects would indicate that birth order is not an important consideration to either of these outcomes."
