Eldest siblings are more intelligent, study claims

You can actually blame the parents

In news that may tear apart families across the globe, eldest siblings are more likely to be cleverer than their younger brothers and sisters.

Researchers at the Universities of Houston, New South Wales and Sheffield found there was “a strong negative relation between birth order and cognitive outcomes of children.”

So the more older siblings you have, the less intelligent you’re likely to be: “The magnitudes of these birth order effects are substantial,” the researchers said.

They also found that older siblings tend to feel confident in their intelligence, and younger siblings are more likely to lack confidence in their scholastic abilities.

But there’s variation in subjects too - the researchers found that the effects of birth order on cognitive test scores are larger when maths is excluded.

This may be because while reading is often encouraged by parents at home, mathematic skills are generally only learned in the classroom.

However, the differences between the siblings are evident before they even start school: “Latter-born children perform worse on cognitive assessments from a very early age, well before they enter school,” the researchers note.

To reach their conclusions, the researchers studied results from over 5,000 children whose reading and picture vocabularies were assessed every two years until they reached the age of 14.

But why the differences between siblings?

According to the researchers, it all comes down to varying levels of parental attention. The more siblings you have, the less attention you get, and the less well you’re likely to perform in academic tests as a result.

“Although latter-born children are not born disadvantaged in their health or developmentally, we find that parents are unable to provide them with the same level of cognitive support as they do with their first-born,” the study explains.

First-born children receive more mental stimulation in the early years of their lives and therefore develop higher brain function than their younger siblings.

The study authors also propose that differences in maternal behaviour during pregnancy and in the first year of a child’s life with regard to alcohol and tobacco consumption and the decision to breastfeed could play a role too.

They suggest that “parents are choosing to relax what they might deem as non-essential rearing practices for their latter-born children.”

Of course, the more children you have, the harder it is to balance all your responsibilities given the time constraints.

However, according to the study, the change in parental attitudes and behaviour “appear to set their latter-born children on a lower path for cognitive development and academic achievement, with lasting impact on adult outcomes.”