While the IQs of children who were born first are higher than those of their younger siblings, the differences are so small that they are practically unnoticeable during day-to-day life, according to new research published in the October edition of the Journal of Research in Personality.
In fact, Forbes explains, the University of Illinois at Urbana-Champaign team behind the study analyzed data for more than 375,000 high school students to determine the impact of birth order on intelligence and personality development, and found that while the IQ of firstborns is higher than their siblings, it’s only higher by an average of just one point.
The publication, which called the new study the largest analysis ever conducted on birth order and personality, said that the results show that the findings indicate that there is “a statistically significant but practically meaningless difference” in the IQs of older and younger siblings. The study was funded by the NIH’s National Institute on Aging.
‘Infinitesimally small’ difference in intelligence, personality
The research, which was led by University of Illinois psychology professor Brent Roberts and former postdoctoral researcher Rodica Damian (now a professor at the University of Houston) also found that first-borns tended to be more extroverted, conscientious and agreeable than later-borns, and also had less anxiety, but that the differences were “infinitesimally small.”
In a statement, Roberts said that the differences in personality amounted to a correlation of 0.02, which will said to be far below the level of perception. “You are not going to be able to see it with the naked eye,” he explained. “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.”
The researchers said that their analysis controlled for potential variables such as the economic status of the family, the total number of children and the relative age of the siblings at the time the study was conducted. They also used a larger sample size than most other studies of a similar nature, and used a subset of two sibling-two parent families to confirm the findings in the study as a whole. In all cases, the differences were “minuscule,” according to Roberts.
“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,” added Damian.
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