Let's settle a debate once and for all: first-born children are definitely the smartest.
A study out of Leipzig University in Germany found that the difference between first-born and later children is small, but consistent, and while the research team doesn't have any concrete answers as to why the eldest sibling is brighter than their less smart siblings, they have some interesting theories.
The study, from a team led by Julia Rohrer, examined the effects of birth order on personality. Using data from three long-term and historical studies, from the U.K. and Germany, the team looked for significant differences in personality, intelligence, imagination, and various social and psychological traits.
Existing, long-standing theories on the effects of birth order convey all kinds of advantages onto the first-born. For instance, the paper references a 1928 paper by Alfred Adler, which speculates about the first-born’s personality traits:
First-borns were privileged, but also burdened by feelings of excessive responsibility and a fear of dethronement and were thus prone to score high on neuroticism. Conversely, he expected later-borns, overindulged by their parents, to lack social empathy.
But the Leipzig study shows that birth order affects nothing but intelligence, and found "no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination." The study was designed to be as rigorous as possible, and to study only the effect of being a first born. To this end, the data was controlled to control for age differences (because, of course, the first-born is always older than its siblings), and for family size. "Differences between first- and later-borns might emerge because later-borns are more likely to be born into families with a lower socioeconomic status," says the study, "which can in turn be associated with differences in intelligence and personality."
The results show that first-borns score consistently higher than their younger brothers and sisters on both conventional intelligence tests and when self-reporting their own prodigious intellect.
One theory about why is that the first born gets more time from its parents in key early development periods. "While the first-born gets full parental attention, at least for some months or years, late-borns will have to share from the beginning," Rohrer told the Daily Mail.
Another possibility is that the eldest kid has to teach his or her siblings, which itself leads to better development. "Teaching other people has high cognitive demands," said Rohrer. "The children need to recall their own knowledge, structure it and think of a good way to explain it to younger siblings, which could provide a boost to intelligence for some first-borns."
If you’re the eldest child in your family, don’t go rubbing it in just yet. While the average intelligence difference is consistent, it is also small—just 1.5 IQ points between siblings. And because it’s just the average, it’s perfectly likely that your younger brother or sister is smarter than you. Then again, you don’t need to tell them that.
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