Why the eldest child is the brightest one

They get more of Mum and Dad’s undivided attention

ELDEST children have l ong complained about having a stricter upbringing than their little brothers or sisters.

But the extra attention from parents may actually do them good – as oldest siblings tend to be the smartest, according to a study.

Researchers found that each successive sibling is generally slightly less bright, and say the difference could be down to younger family members having to ‘share’ their mother and father.

Younger children also see themselves as less intelligent than their older brothers and sisters – despite the actual difference being quite small.

The team from Leipzig University i n Germany crunched together the results of three national studies, including one from the UK, involving more than 20,000 people i n total. Data included the results of IQ and personality tests.

Families with more than four children were excluded because there were too few of them to provide meaningful input.

Analysis showed a clear drop in IQ of around 1.5 points for each extra sibling – as well as in the person’s own perception of their intelligence.

However no personality differences were found – despite some previous studies claiming that birth order affects character traits such as extraversion and reliability.

Researcher Julia Rohrer said that the impact of birth order had long fascinated both scientists and the public.

She added that while she did not specifically examine why eldest children tend to be brainier, the reason could well lie in upbringing. ‘ One theory is that following children dilute their parents’ resources,’ she said.

‘While the first-born gets full parental attention, at least for some months or years, late-borns will have to share this from the beginning.’

Dr Rohrer added that another possible explanation is that older children benefit from telling their little brothers or sisters about their surroundings.

‘[It] is described as the tutoring hypothesis: A first- born can “tutor” their younger siblings, explaining to them how the world works and so on,’ she said.

‘Teaching other people has high cognitive demands. 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.’

Biology may also play a role, with younger children more prone to genetic problems because their parents are that bit older when they are born.

However previous research shows that if a second-born child is raised as the eldest – for example if the first-born dies in infancy – their intelligence is on a par with other first-borns.

Yet despite Dr Rohrer’s findings, which were published in the j ournal Proceedings of t he National Academy of Sciences, eldest children should resist gloating too much.

According to her calculations, in a two-child family the eldest will have the higher IQ six times in t en –a statistic t hat stil l gives younger children the opportunity to shine.

‘Late borns have to share’