Science confirms that first-born siblings are in fact smarter

It's always been suspected that birth order affects character and personality traits, and now research weighs in on its affect on intelligence

A brother and his younger sister laying on the grass on a sunny day
(Image credit: Future)

The rumours have been mulling around for years. Does birth order really matter when it comes to intelligence? It appears that scientific evidence may finally give us a concrete answer.

We all know that having siblings can have a big effect on our upbringing. Of course, we're all familiar with the idea of sibling rivalry (although the good news is that kids who fight with their siblings will fare better in life) - and some studies have also shown how having older siblings can affect mental health,

Now, a new study by researchers at the Universities of Houston, New South Wales and Sheffield have revealed that older siblings are smarter than younger ones - and even revealed why. Study leaders found that older siblings are more confident in their academic ability, while younger siblings are more likely to doubt themselves.

The team claimed that this could be because first-born children don't have anyone to compare themselves to, but it could also be down to the amount of attention given by parents. This sentiment was echoed in a previous study by the University of Edinburgh, which found that first-born children do in fact have a higher IQ than their younger siblings and that parents are to blame.

first born siblings smarter

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Scientists found that the lower IQ in younger siblings could be down to differences in parental attention. While older siblings are likely to have spent focused alone time with their parents being mentally stimulated through reading, creative activities and playing musical instruments before the second child was born, younger siblings are accustomed to sharing their time with another child, without that focused attention the older brother or sister would have had.

This could help to justify the impression that birth order leads to higher wages and better education in first-borns. The study, published in the Journal of Human Resources and carried out in partnership with Analysis Group and the University of Sydney, looked at data from the US Children of the National Longitudinal Survey of Youth collected by the US Bureau of Labour Statistics to come to their conclusions.

The study examined almost 5,000 children from before birth up until 14 years of age. They assessed skills, such as reading and picture vocabulary, every two years to gauge the differences between first-borns and younger siblings.

Researchers also looked at children’s test scores in relation to parental behaviour, like smoking and drinking during pregnancy. They found that mothers tended to be more careful during their first pregnancies and were likely to take ‘higher risks’ during subsequent pregnancies. While this was not directly related to the study results, it could have a bearing on children’s IQ levels.

But while younger siblings can blame parents for possibly offering less support in developing thinking skills during their formative years, this study doesn’t give them an excuse to grill you about that one glass of wine you had during your third trimester. 

Aleesha Badkar
Lifestyle Writer

Aleesha Badkar is a lifestyle writer who specialises in health, beauty - and the royals. After completing her MA in Magazine Journalism at the City, the University of London in 2017, she interned at Women’s Health, Stylist, and Harper’s Bazaar, creating features and news pieces on health, beauty, and fitness, wellbeing, and food. She loves to practice what she preaches in her everyday life with copious amounts of herbal tea, Pilates, and hyaluronic acid.