Does being an oldest, middle or youngest child shape the person you become?
According to a large body of research on birth order, the answer is yes -- a child's rank in the family may exert a significant influence on their personality and intelligence. These studies have found that oldest children tend to be the intelligent, responsible high-achievers, while middle children are the peacekeepers and the babies of the family are the rebellious attention-seekers.
Is it true? Maybe not.
The largest study on birth order to date has come to a very different conclusion. The new research, conducted by scientists at the University of Illinois at Urbana-Champaign, suggests that while differences between older and younger siblings may exist, they're unlikely to have any real-world significance.
The research, published last week in the Journal of Research in Personality, found that firstborn children do tend to have higher IQs and personality traits distinct from later-born children. However, these differences were extremely minor.
"This is a very small difference that would not be visible in any way with the 'naked eye,' and it's unlikely to be meaningful for any real-world outcomes," Dr. Rodica Damian, one of the study's authors and now a professor of psychology at the University of Houston, told The Huffington Post in an email.
Analyzing data on 377,000 U.S. high school students, the researchers found that firstborn children on average had an IQ one point higher than later-born children.
They also observed minor changes in personality between oldest and younger children. The oldest children tended to be more extroverted, agreeable and conscientious, and less anxious than middle and youngest children, although the correlation was only a fraction of a percent.
The researchers explained that while these differences are statistically significant, they're unlikely to translate into noticeable distinctions in personality or intelligence.
The findings diverge from many previous findings that have shown a meaningful correlation between birth order and personality and intelligence.
Why? The latest researchers cite the small sample sizes of previous studies, as well as the fact that many of them relied on testimonies from parents, which can be biased. For instance, if a parent is asked to compare their children, he or she is likely to say that an older child is more responsible than a younger child, not because they are actually more conscientious but simply because they are older.
The takeaway: Your role in the family isn't preordained. Mom and dad shouldn't let birth order dictate how they parent.
"Personality changes over time, especially with age," Damian said, "so parents should be mindful of their kids' life stages and realize that whatever differences they see are likely due to age."