The researchers analyzed the personalities and IQ’s of siblings within the same family and came to the conclusion that the differences in these areas were negligible; first-born children only benefitted from an advantage of one IQ point over their siblings.
In terms of personalities, researchers found that first-borns were more likely to be extroverted, agreeable, and conscientious when compared to younger siblings. They also harbored less anxiety on average. But Brent Roberts, who helped lead the study, said that those differences were “infinitesimally small.”
No meaningful difference
Roberts and his fellow researchers were sure to collect a large sample size and control for as many variables as possible. The study examined 377,000 high school students, and factors such as economic status, number of children, and the relative age of siblings were all accounted for.
“This is a conspicuously large sample size…It’s the biggest in history looking at birth order and personality,” said Roberts.
The researchers stress that the differences they recorded in their results were so small that they are practically meaningless. “In some cases, if a drug saves 10 out of 10,000 lives, for example, small effects can be profound….But in terms of personality traits and how you rate them, a 0.02 correlation doesn’t get you anything of note. You are not going to be able to see it 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,” said Roberts.
Although the results do not provide anything of note, the magnitude of the study makes up for many within-family studies that have been conducted in the past. It has been published in the Journal of Research in Personality.