Who’s the smartest sibling – the oldest, middle or youngest child?

In your family, are you the D.J., Stephanie or Michelle Tanner?

Well, good news for all you D.J.s out there because a new study has found that first-born children are smarter than their younger siblings – thanks to your parents.

The reason for the higher IQ in eldest children, researchers say, is because parents tend to take more time developing the child’s thinking skills but then become more laid back with other children once they feel they have the hang of parenting.

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“As the household gets bigger, time has to be split with younger children so they miss out on the advantage of being an only child for a time,” lead author Dr. Ana Nuevo-Chiquero tells The Telegraph. “It doesn’t mean first-borns get more love, that stays the same. But they get more attention, especially in those important formative years.”

Researchers from University of Edinburgh, Analysis Group and the University of Sydney followed 5,000 kids from pre-birth to age 14. Every two years they would assess the children through reading recognition testing, as well as collect information on environment factors, like family background and economic conditions.

Researchers also looked at the parents and their behaviour by using the home Observation Measurement of the Environment assessment tool. This helped them look at their smoking and drinking habits during pregnancy and post-birth behaviours, such as mental stimulation and emotional support.

The study found that parents offered less mental stimulation to their younger kids and also took part in fewer activities with them, like reading, crafts and playing musical instruments.

Tweet This Click to share quote on Twitter: The study found that parents offered less mental stimulation to their younger kids and also took part in fewer activities with them, like reading, crafts and playing musical instruments.

Parents also show a more relaxed attitude to smoking and drinking during pregnancy.

The findings could help explain the “birth order effect” – when children born earlier in families earn better wages and are more educated later in life – the study says.

Canadian parenting expert and family therapist Alyson Schafer, who was not involved in the study, agrees with most of what researchers found.

“Our parenting does change with each subsequent child,” she says. “Getting three kids bathed and into bed looks a lot different than it did when you had only one. We get more skilled and more relaxed with practice.”

Tweet This Click to share quote on Twitter: "Our parenting does change with each subsequent child," she says. "Getting three kids bathed and into bed looks a lot different than it did when you had only one. We get more skilled and more relaxed with practice."

However, Schafer offers another possible explanation as to why the older siblings tend to do well in academics, citing something called Adlerian psychology – a theory which looks to how children try to differentiate themselves in the family.

“Each sibling tries to excel in unique areas,” Schafer says. “Typically, our society and families focus on school and achievement. First-borns who get a lot of attention from parents – about everything – tend to want to please their parents and elicit smiles and approval. They tend to want to do things right and well, so they like to learn rules and apply rules to succeed.”

And a great place for applying those rules, Schafer says, is school.

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One thing to keep in mind, though, is cultural differences and other factors when discussing the “birth order effect,” says Schafer.

“You might be the first born in a family, but if you have a disability or illness you may assume the ‘role’ or psychological position of being the baby,” Schafer points out. “In cultures where gender differences are culturally entrenched, you may have a first-born female but the second-born male is treated specially as the first-born male heir for example.”

A 2015 study also looked at how birth order can affect children and found that while the order of which one was born determines their personality type, it could signal other outcomes.

After examining 20,000 people, researchers from the University of Leipzig concluded that older siblings are smarter on average while younger siblings are healthier and are more likely to be gay (if they’re men).

It was the second-largest study to look at the effects of birth order.