It appears that the eldest children tend to be the smartest among their siblings.
A new study from the University of Leipzig in Germany found that each successive child after first-borns possessed a lower IQ. Researchers aren’t certain why eldest brothers and sisters seem to be brighter, but they say it may be because they receive undivided attention from their parents up until the next child comes along.
“While the firstborn gets full parental attention, at least for some months or years, lateborns will have to share from the beginning,” study co-author Julie Rohrer told The Telegraph.
Another possible contributing factor to the finding is that eldest children may be smarter because they have to teach their younger siblings about how the world works, among other things.
“Teaching other people has high cognitive demands – 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 firstborns,” Rohrer said.
Biology may also play a role in the IQs of younger siblings, researchers say, as they may be more prone to genetic problems since their parents are older when the children are conceived, the Daily Mail reported.
The decrease in IQ is small, however, with each successive sibling posting 1.5 IQ points lower than the one before them.
In a two-child family, Rohrer said the eldest will possess the higher IQ six out of 10 times, which means the younger brother or sister still has the chance to shine, the Daily Mail reported.
The study further finds that younger siblings have more freedom to do what they want.
A 2013 study conducted by the National Bureau of Economic Research, an American non-profit research organization, had similar findings. It stated that earlier-born children do better in school and attributed this to parents. Economists V. Joseph Hotz and Juan Pantano, who authored the study, said because mothers and father tend to be more lenient with their later-born kids, first-borns usually receive better parenting and the better grades.
The study, however, did not find any differences in the personalities of siblings, despite the popular belief that younger brothers and sisters tend to be funnier or more extroverted, according to The Telegraph.
In a separate study published in August, it was found that eldest sisters are more likely to be obese. Scientists examined data from 13,400 pairs of sisters and found that firstborn women were, on average, 29 percent more likely to be overweight and 40 percent more likely to be obese than their second-born sisters, the Daily Mail reported.
