Birth order doesn’t affect younger siblings intelligence and personality: or does it? Find out!

Birth order doesn't affect younger siblings intelligence

Many people differentiate between their children’s intelligence and personality. Some people think older siblings are more intelligent than younger ones, and that younger siblings are more outgoing etc. These thoughts and beliefs continue in families, and some scientists decided to do some studies to see whether birth order plays a part in a person’s personality, intelligence etc.

One of the latest studies was conducted on 20,000 people belonging to different countries- UK, US and Germany. Another studied 377,000 US school students.

Read on to find out if birth order doesn’t affect younger siblings or whether the opposite is true:

Birth order doesn’t affect younger siblings, say scientists

Birth order doesn't affect younger siblingsThe belief that birth order determines personality traits and IQ of families is deeply entrenched in society. The usual view of people across the world is that younger siblings have to compete for parents’ attention, find many different ways for that, and thus are cleverer. First-borns are perceived to be physically and mentally stronger, and so are usually more aggressive, or rather bossy!

Scientists from Leipzig University as well as Johannes Gutenberg University, Mainz, Germany, studied how is a person’s achievements and personality affected by their birth order. They studied about 20,000 people or more belonging to the United States, Germany and United Kingdom, comparing siblings. They looked at people of same order of birth among different families, and also compared siblings from same family.

The good news is that the scientists found that birth order did not play any role in the intrinsic nature of people, and birth order doesn’t affect younger siblings. They said that birth order did not affect agreeableness, emotional stability, extraversion, conscientiousness. It does not affect imagination either, which they said is a ‘subdimension of openness’.

Birth order does not affect personality, confirms a US study

A study which was published in ‘Journal of Research in Personality’ found very little evidence that birth order has anything to do with the personality differences. The study had a whopping 377,000 high school students as participants. The scientists tried to answer the question does birth order affect personality? 

In order to analyze that, the scientists looked at five traits of personality – agreeableness, openness, extraversion, neurotism, conscientiousness. They predicted that first born children would be more conscientious, neurotic and dominant. According to them, other siblings would be more agreeable and sociable.

So does birth order affect personality? Apparently, after studying the data gained from 377,000 students, they found that birth order doesn’t affect younger siblings. The study found that there was an insignificant difference between personality traits of first born children and younger siblings. Younger siblings may therefore rejoice that birth order doesn’t affect younger siblings! Personality traits do not depend on the order of birth, but on some other things – most probably the inherent nature that every person is born with.

Does birth order affect intelligence

first borns and later borns Looking at all the results of various studies, we can conclude that birth order doesn’t affect younger siblings personality. The birth order study conducted on the high school students also studied whether birth order affects intelligence.

The study revealed that birth order did have a slight impact on intelligence between first borns and later borns – first born children tended to have higher IQs, but only by one point. Another study however found that this too did not matter, as the IQs of some teenagers changed drastically. IQs between children could differ by about 20 points within a span of four years. It was not necessarily the oldest child who was also the most intelligent. So to think that birth order affects intelligence would be a wrong assumption.

Therefore, whether you’re the first born or the middle child or the youngest, you can have an IQ difference of 20 points with your siblings, and even if you’re the youngest, you may be the brainiest of them all!

Then again…

According to huge national surveys conducted in the UK, US and Germany, younger siblings usually have lower IQ than older sisters and brothers. The surveys found that there was an ‘objective dip’ in IQ, which occurs gradually i.e. the first born is the most intelligent, second born child a little less and the last born child has the lowest IQ, though the difference could be very low. Doesn’t sound good for the youngest child, does it?

The scientists speculated that the most likely reasons for this disparity could be because:

  • Parents pay more attention to older children, as there are no other children to divide their attention. Younger siblings get lesser parenting time, as parents’ time is divided between two or three (or more) children. Birth order doesn’t affect younger siblings, personality wise, but in the initial years, due to birth order, older children might be slightly more intelligent.
  • Parents put many more demands on first born, in academics etc. Younger siblings might get more leeway with academic and sports results etc.
  • The ‘tutoring hypothesis’ – according to this hypothesis, a first child can and usually do tutor their younger siblings. They teach them academics as well as explain the ways of the world. Instructing is considered to be an activity which is cognitively demanding. Thus, instructing younger sister and brothers may give first born children a unique mental experience/training.
  • Another theory is that younger children ‘dilute’ parents’ resources.

Researchers also found that younger siblings assessed themselves as being less intelligent than older siblings.


Birth order doesn’t affect younger siblings when it comes to personality. A person can have any personality, which does not depend whether they were born first or last. Some researchers suggest that birth order has been the concept traditionally used to explain different personalities across and within families. But there is no scientific data to prove that personality traits are a result of birth order.

As for intelligence, the first born children may have an edge over their siblings in their initial years, but the younger ones catch up with their older sisters and brothers over time. So birth order doesn’t affect younger siblings, and people are what they are due to completely different reasons!

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