How Birth Order Affects Who You (and Your Children) Are

Our beliefs about birth order make intuitive sense — but are they true?

How Birth Order Affects Who You (and Your Children) Are

Birth order is a slippery science. Ever since Austrian psychiatrist Alfred Adler (a contemporary of Sigmund Freud) first posited the theory that birth order has an indelible affect on your personality back in the 1920s, we’ve been using it as a shorthand to understand that bossy firstborn, the spoiled baby of the family or your own Jan Brady — the difficult, neglected middle child.

Our beliefs about birth order make intuitive sense — but are they true? Here’s how birth order really affects who you are.

Firstborns Are Smarter

In a 2007 study that all high-achieving, perfectionist firstborn children tend to cite, firstborns have higher IQs, by two or more points. The difference was deemed “slight” but “significant” at the time.

One possible explanation? "Firstborns have their parents’ undivided attention as infants, and even if that attention is later divided evenly with a sibling or more, it means that over time they will have more cumulative adult attention, in theory enriching their vocabulary and reasoning abilities," according to a New York Times article about the research.

The Accomplished Firstborn

The notion that firstborns are natural-born leaders is pretty ingrained — and there are some stats to back that up. Twenty-one of the first 23 astronauts to go into space were firstborns. Firstborns have won more Nobel Prizes in science than middle- or last-borns. And one study found that firstborn men (ahem) are more likely to be CEOs. A WBUR report put it this way: “Firstborn children are 30 percent more likely to be top managers; later-born children are much more likely to be self-employed.”

The reality is, as one might expect, a little more complicated. The New York Times contextualizes the abundance of firstborn Nobel Prize winners by stating, “Firstborns have won more Nobel Prizes in science than younger siblings, but often by advancing current understanding, rather than overturning it.”

The idea is that cautious and conscientious firstborns abide by the rules. Subsequent children are more free to overturn them and potentially create revolutionary change.

Who Runs the World? Firstborn Girls

The historical data on firstborns tends to focus on boys and men — with the caveat that the findings on IQ or achievement are likely to extend to women as well. But a 2014 study out of the University of Essex found that firstborn girls “especially outdo their siblings in educational dreams and attainment.”

Case in point? Just look at Angela Merkel, Hillary Clinton, Christine Lagarde, Oprah Winfrey, Sheryl Sandberg, JK Rowling and the Queen herself, Beyoncé.

Like Prefers Like

A 2009 study found that, when it comes to birth order, birds of a feather really do tend to flock together.

“Firstborns are more likely to associate with firstborns, middle-borns with middle-borns, last-borns with last-borns, and only children with only children,” wrote psychologist Joshua K. Hartshorne, of Boston College, in a piece for Scientific American.

Middle Child Syndrome Is B.S.

In 2015, German scientists debunked many of our beliefs about birth order, including, specifically, middle child syndrome, which suggests that middle children get neither the psycho-social benefits of being first nor the emotional boon of being last and are therefore neglected and isolated within the family.

In what was a massive study of more than 20,000 adults, researchers found no relevant correlations. “No matter how they spliced the data, they could find no association of birth order with any personality characteristic,” wrote Nicholas Bakalar in The New York Times. One of the researchers told him, blithely, “It’s important to stop believing that you are the way you are because of birth order.”

(Unless It’s Not)

Despite the landmark 2015 study, middle children have enjoyed a sustained comeuppance. Just read “The Secret Power of Middle Children: How Middleborns Can Harness Their Unexpected and Remarkable Abilities” and the spate of related articles, such as “5 Reasons Why Being the Middle Child Is Actually the Best," that have come out since.

Indeed, psychologist Catherine Salmon, Ph.D., and journalist Katrin Schumann have almost single-handedly reframed our understanding of middleborns, praising, for instance, the ability to be a peacemaker and effective negotiator and to be oriented toward others, particularly outside the family structure.

Middle Children Are an Endangered Species

Wherever you land on the middle child syndrome spectrum, one thing is irrefutable — there are fewer and fewer middle children to go around. In a headline story for New York Magazine’s vertical, The Cut, Adam Sternbergh wrote:

“In the ’70s, four kids (or more) was the most common family unit. Back then, 40 percent of mothers between 40 and 44 had four or more children. Twenty-five percent had three kids; 24 percent had two; and 11 percent had one. Today, those numbers have essentially reversed. Nearly two-thirds of women with children now have two or one — i.e., an oldest, a youngest, but no middle … Families with two or fewer kids have become the norm for every demographic group. Middle children, the most populous birth-order demographic throughout most of human history, will soon be the tiniest.”

The Middle Child Legacy Is Long

Although the conventional wisdom might suggest that, say, U.S. presidents are more likely to be firstborns — they’re not. Actually, 52 percent of presidents are middle children — a fact that takes into account older female siblings, which somehow hadn’t been included in previous data. Notable middles include Abraham Lincoln, John F. Kennedy and Donald Trump* as well as Winston Churchill, Bill Gates, Martin Luther King Jr., Warren Buffet, Madonna, Mart Twain, Mark Zuckerberg, Martha Stewart, Susan B. Anthony and Steve Forbes.

*As psychologist Catherine Salmon told CNN, “Donald Trump is a middle with a firstborn brother who didn't fit the role. Donald usurped it.”

The Thing With Second-Born Sons

Every middle child starts as a second-born, and in a two-child family, the second-born does double duty as the baby. Compared to their older brothers, second-born boys are in for some trouble — they’re more likely to get suspended, be delinquent and go to prison.

“I find the results to be remarkable,” says Joseph Doyle, an MIT economist who studied birth order, in an interview with NPR. “Across all these outcomes, we're getting 25 to 40 percent increases in the likelihood of these outcomes just by comparing a second-born sibling compared to a first-born.”

Babies Are Babied

Psychologist Kevin Leman, who wrote the best-selling book on the subject, “The Birth Order Book,” sums up the plucky, outgoing personality of the last-born thusly: “The babies of the family could sell dead rats for a living if necessary.”

Indeed, last-borns tend to be outgoing, fun-loving, free-spirited, spoiled and a bit manipulative, in part because, by the time they come around, their parents are over it when it comes to strict, authoritarian parenting.

Studies Have Shown … Almost Everything

It’s dizzying what researchers have undertaken in the name of birth order. As journalist Lauren Davidson points out in The Telegraph, “Previous research has led to all sorts of conclusions: First-borns are more prone to allergies, last-borns are promiscuous, middle children are more rebellious, babies of the family are shorter than their siblings and men with older sisters are less competitive.”

The Only Child

The only child typically has all the characteristics of the firstborn, but on steroids. (Some call them “super-firstborns.”) Their world is mostly adult, and that makes them seem incredibly mature for their age with respect to vocabulary and certain social skills.

“Growing up as an 'only' can be very empowering, creating very self-dedicated, strong-willed individuals who push themselves hard to achieve what they want,” psychologist Carl E. Pickhardt, author of “The Future of Your Only Child” told Business Insider.

On the flip side, only children are widely considered to be more selfish and less likely to share.

Your Brain, on Being an Only Child

Fascinatingly, one study showed that only children — in this case, hundreds of children from China, where the one-child policy reigned — have different brains than children with siblings.

Researchers found that only children had larger supramarginal gyrus volumes, which has to do with language and processing, and smaller medial prefrontal cortex (mPFC), which has to do with emotional regulation.

What About the Rest of Us?

Thanks to divorce, blended families and adoption, a lot of what we believe to be solid birth order traits get shaken up and challenged.

What happens when a firstborn is replaced by an older firstborn when two families merge? Or when a lastborn becomes a middle? Or an only child is recontextualized by siblings? As Dr. Leman puts it, "Blended families don't blend; they collide."

No Two Children Have the Same Roles in the Same Family

Not even twins have the same roles in the same family. Because of the complex ways we adopt — and enforce — roles and responsibilities within a family unit, we all have a unique role to play. Are you bossy because you were born first or because you naturally score high when it comes to conscientiousness? Are you the joker in the family because you’re the youngest or because you’re extraverted and agreeable?

With each new study comes a new understanding about what we believe about birth order. And if conventional wisdom has anything to do with it, it’ll probably be a rebellious middle or last-born child who will have done the work to upend it.