Your second child is more trouble than your first. You're not imagining it, it's science.

It’s a universal parenting truth that most people with more than one kid know: as soon as you think you might know what you’re doing, the second child comes along and chaos reigns again. Because the second child is never a replica of the first.

Now, a 2017 study backs that up with scientific evidence. So, if you’ve ever felt your second-born was more ‘challenging’, it’s now official, and not just in your head.

Massachusetts Institute of Technology economist, Joseph Doyle, studied thousands of families in Denmark and America with two or more children in search of evidence of this commonly-felt phenomenon.

It’s important to note that Doyle admits the sampling included a majority of families where the second-born was male.

And also, that Doyle did not speak to the mother of this writer (who is the second-born).

Mamamia Out Loud discusses sibling rivalry. 

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The study found that second-borns presented more “challenging” behaviour; they were more likely to get in trouble at school, and, more alarmingly, with the justice system as adults.

So why is this the case? The authors of the research explained their reasoning:

“We consider differences in parental attention as a potential contributing factor to the gaps in delinquency across the birth order.”

Of course it is – it’s always a parent’s fault, right? But actually, even Doyle admitted that’s not the full picture.


He said: “The firstborn has role models, who are adults. And the second, later-born children have role models who are slightly irrational 2-year-olds, you know, their older siblings.”

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An example of an oldest sister enjoying a younger's downfall. Source: Giphy.

So before you drown in a wave of parent-guilt, take comfort knowing that you can blame it partly on your first-born, too.


Of course, the study is not the first to assert that birth order effects a child's behaviour and influences their life.

Dr Gail Gross, a Human Behaviour and Education Expert, previously told Mamamia;

"Some researchers believe birth order is as important as gender and almost as important as genetics. It gets back to the old nurture vs. nature business."

Since the 1970s, thousands of scientific studies have been conducted into birth order. Whilst there is disagreement about how much birth order is a factor in development, there seems to be a general consensus that there are some common traits between oldest, youngest and middle siblings.

These common traits are that, generally speaking, the oldest sibling seems to be achievement-oriented, and responsible. The youngest child, however, is generally more rebellious and attention-seeking, but also creative.

“Firstborns tend to be responsible, competitive and conventional, whereas laterborns have to ‘distinguish’ themselves and create a specific niche by being playful, cooperative, and especially, rebellious,” Belgian psychologists Vassilis Saroglou and Laure Fiasse wrote in a 2003 paper published in the journal Personality and Individual Differences.

Regardless of what all the researchers, academics, and professionals assert, many parents of more than one child will testify, based on their lived experience, that there's truth to the theory - except for this writer's mother, of course.

Is your second child more trouble than your first? Tell us in the comments section below.