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Does Birth Order Really Determine Personality? Here’s What the Research Says

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One Friday afternoon at a party, I’m sitting next to a mother of two. Her baby is only a couple of weeks old. They’d taken a long time, she tells me, to come up with a name for their second child. After all, they’d already used their favorite name: it had gone to their first.

On the scale of a human life, it’s small-fry, but as a metaphor I find it significant. I think of the proverbs we have around second times—second choice, second place, second fiddle, eternal second. I think of Buzz Aldrin, always in the shadow of the one who went before him, out there on the moon. I think of my sister and my son: both second children.

I was the first child in our family. I was also fearful of failure, neurotic, a perfectionist, ambitious—undoubtedly to the point of being unbearable. My sister didn’t study as hard and went out more, worked at every trendy bar in town and spent many an afternoon in front of the TV.

I’d long attributed the differences in our characters to the different positions we held in our family. It seemed to me, all things considered, better to be the firstborn: you had to work harder to expand the boundaries your parents set for you, had a greater sense of responsibility, more persistence, and emerged, in the end, more self-confident.

That theory worked in my favor, but during my second pregnancy, I started to feel sorry for my son. Through no fault of his own, he’d missed out on the enviable position of firstborn. It took that sense of pity for me to realize that I could try to uncover the basis of my ideas about the personality traits of first and second children—and whether there was anything to them.

It was 1874, and Francis Galton, an intellectual all-rounder and a half cousin of Charles Darwin, published English Men of Science: Their Nature and Nurture. In his book, he profiled 180 prominent scientists, and in the course of his research Galton noticed something peculiar: among his subjects, firstborns were overrepresented.

Galton’s observation was the first in a long line of scientific and pseudoscientific publications on the birth-order effect. The greater chance of success for firstborns, in Galton’s view, was because of their upbringing, an explanation that fitted in with the mores of the Victorian era: eldest sons had a greater chance of having their education paid for by their parents, parents gave their eldest sons more attention as well as responsibility, and in families of limited financial resources, parents might care just a little bit better for their firstborns.

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The distribution system at the foundation of this is called primogeniture: the right of the eldest son (or less frequently, the eldest daughter) as heir. Among Portuguese nobility in the 15th and 16th centuries, for example, second- and later-born sons were sent to the front as soldiers more often than firstborn sons. Second and subsequent daughters were more likely than eldest daughters to end up in the convent. In Venice in the 16th and 17th centuries, it was generally the eldest brother who was permitted to marry, after which younger brothers would live with him and his family, dependent and subservient.

Apart from a few royal families, primogeniture is no longer the norm in Western countries. Somewhere in the course of the last century, most residents of industrialized countries became convinced that love, attention, time and inheritance should be divided equally and fairly among our offspring.

That’s what my partner and I strive to achieve: equal treatment of our two children. But we can’t get around the fact that first, second and subsequent children have slightly different starting points. The question is what consequences that has, exactly – and how insurmountable they are.

At the start of the 20th century, Alfred Adler, Freud’s erstwhile follower, the one who believed that the arrival of a younger sibling meant the dethronement of the firstborn, introduced the birth-order effect into the domain of personality psychology. According to Adler, the eldest identifies most with the adults in his environment and therefore develops both a greater sense of responsibility and more neuroses. The youngest has the greatest chance of being spoiled and is also, often, more creative. All children in the middle—Adler was a middle child—are emotionally more stable and independent: they’re the peacemakers, used to sharing from the start.

After Galton and Adler, the idea that family position affects personality has been subjected to many a scientific test. These tests generated factoids that undoubtedly still fly across the table at Christmas dinners: that firstborn children are overrepresented as Nobel Prize winners, composers of classical music, and, funnily enough, “prominent psychologists.” Subsequent children, on the other hand, were more likely to have supported the Protestant Reformation and the French Revolution.

There are so many assumptions, there’s so much research, and still there are very few hard conclusions to be drawn.

A friend, the eldest of four, presses into my hands a book that her mother claims to have been all the rage during the 1990s. The title is Brothers and Sisters: The Order of Birth in the Family, and it was written in the mid-20th century by the Viennese pediatrician and anthroposophist Karl König.

What strikes me from the very first pages is the certainty with which König characterizes first, second and third children. For example, he quotes a study that found firstborns to be “more likely to be serious, sensitive,” “conscientious,” and “good” and—this is my favorite—“fond of books.” Later on, these firstborns can become “shy, even fearful,” or they become “self-reliant, independent.” A second child, by contrast, is “placid, easy-going, friendly [and] cheerful”—unless they are “stubborn, rebellious, independent (or apparently so)” and “able to take a lot of punishment.” These typologies most resemble horoscopes, in the sense that it can’t be very hard to recognize yourself – or your children – at least partially in any of them.

By now, studies looking into the birth-order effect number in the thousands. There’s no shortage of popular publications either: titles such as Born to Rebel: Birth Order, Family Dynamics, and Creative Lives and Birth Order Blues: How Parents Can Help Their Children Meet the Challenges of Birth Order have helped spread the idea that your place in the family determines who you are.

In 2003, two U.S. and two Polish psychologists asked hundreds of participants what they knew about birth order. The majority of respondents were convinced that those born earlier had a greater chance of a prestigious career than those born later, and that those different career opportunities had to do with their specific birth-order-related character traits.

In sum, a century after the possible existence of the birth-order effect was first proposed, it had become common knowledge. That knowledge is now so common, in fact, that it lends itself to satire: “Study Shows Eldest Children Are Intolerable Wankers,” a headline on a Dutch satirical news website quipped in 2018.

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There is, however, plenty of criticism of birth-order theories and the associated empirical research. It’s not at all straightforward, critics point out, to know what you’re measuring when you try to unravel the factors that shape an individual human life. It’s also very hard to exclude all the “noise,” as physicists in a laboratory would be able to do more easily. This means that traits we might attribute to a person’s birth order may in fact have more to do with, say, socioeconomic status, the size or ethnicity of the family, or the values of a particular culture.

In the early 1990s, a group of political scientists observed with barely concealed exasperation that birth order had been “linked to a truly staggering range of behaviors.” They tried to debunk the myth that even a person’s political preferences were determined by their position in the family by reviewing studies that addressed, among other things, whether firstborns had “an uncommon tendency to enter into political careers,” were more conservative than those born later, and were more likely to hold political office. Their meta-analysis failed to find consistent patterns—but did find myriad methodological flaws.

There are so many assumptions, there’s so much research, and still there are very few hard conclusions to be drawn, although I suppose the latter is often the case, in the social sciences. They tend to provide more nuance rather than painting things in black and white— and rightly so.

Still, I’d like to know if there’s a counterargument to be made, in response to the certainty with which a friend remarks that second children are always “much more chill” than first children. Or to the way a family member takes it for granted that our son, independent and sociable as he is, is a “typical second child.”

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The end of 2015 saw the publication of two studies in which the methodological shortcomings of previous birth-order research (unrepresentative sample sets, incorrect inferences) were largely obviated. In one of these studies, two U.S. psychologists analyzed data about the personality traits and family position of 377,000 secondary-school pupils in the United States. They did find associations between birth order and personality, but besides being so tiny as to be “statistically significant but meaningless,” as one of the researchers formulated it, they also partially ran counter to those predicted by the prevailing theories. For instance, firstborn children in this data set might be a little more cautious, but they were also less neurotic than later-born children.

The other study looked for associations between personality and birth order in data from the United States, Britain and Germany for a total of more than 20,000 people, comparing children from different families as well as siblings from the same family and correcting for factors such as family size and age. Here, the researchers found no relationship between a person’s place in the family and any personality trait whatsoever.

Other recent studies, conducted mostly by economists, do find an association between birth order and IQ: on average, firstborns score slightly higher on IQ-tests – they also tend to get more schooling. This may be due, researchers speculate, to the fact that parents are able to devote more undivided time and attention to their firstborns when they are very small. It’s an effect that has less to do with innate characteristics and more with parental treatment.

For me, it feels as if my children have been given a little extra wiggle room, a more level playing field. Whoever my son is or will become, his personality has not, or in any case not only, been determined by the coincidental fact of his having arrived second. My relief is conditional, of course—science has a tendency to change its mind.

Even so, the authors of one of those 2015 studies cherish little hope of ridding the world of the belief that birth order determines personality. After all, they wrote in an accompanying piece, it takes forever for academic insights to trickle down to the general public. And we tend to be swayed less by scientific results than by our own personal experiences.

My second child is quicker to anger, I once told another mother in a parenting course. But hadn’t my daughter been just as irascible when she was my son’s age?

One of the reasons belief in the birth-order effect is so persistent, they suggest, is because it’s so easily confused with age. Pretty much everyone can see with their own eyes that older children behave differently from younger children. And there’s a good chance that a first child, when compared with a second child, will appear more cautious and anxious. It’s just that this difference probably has more to do with age than with birth order.

My second child is quicker to anger, I once told another mother in a parenting course. But hadn’t my daughter been just as irascible when she was my son’s age? I’d described my son, who was almost 2 years old at the time, as more emotionally stable. Perhaps what I’d meant is that I can easily discern his emotions: they’re still so close to the surface. He sulks when something doesn’t go his way, bows his head and looks askance when he’s doing something he knows he shouldn’t, throws everything within reach on the floor when he’s angry. When he’s excited, he wags—it doesn’t matter that he lacks a tail. His sister’s feelings have already grown more subtle and complex, and the way they’re expressed has become hard to read, for her own 5-year old self as well as for me.

That difference in age might also be the reason that children from the same family are often assigned specific roles, a Dutch developmental psychologist tells me when I present her with the hypothesis of the two U.S. researchers. That way, even if there are no fixed differences in personality, we might still impose differences in behavior. Parents tell the eldest to be responsible, and the youngest to listen to the eldest. The behavior that follows from this is an expression of that role, not of a person’s character.

I think of the way we tried to prepare my daughter for the arrival of her little brother. How we told her that soon there would be someone who couldn’t do anything at all. She’d be able to explain everything to him, we’d said, because she already knew so much. The prospect had appealed to her. Little did we know we were talking her into a stereotype-perpetuating role.

Of course, all the circumstances in which a child comes into the world—whether they’re born male or female, in war or peace, into relative poverty or exorbitant wealth—end up making a person who they are. But the birth-order effect seems to particularly enthuse and preoccupy us.

Perhaps because it’s so concrete: it’s rather more fun and more satisfying to attribute a baby’s generous smile to the fact that he’s a second child than to a vague interplay of personality and environment, expectations and discernment.

And perhaps that’s also what makes it so tempting to attribute the effect to ourselves. It absolves us for a moment of the responsibility for who we are and the duty to turn ourselves into who we want to become: my being neurotic isn’t my fault, it’s just because I’m the eldest.

My son began to dole out little smiles when he was barely 4 weeks old. They were not just twitches or reflexes, I knew for sure, but outright attempts at contact. He began smiling earlier than his sister had, and this made sense to me: he was the second child, and so the more sociable one, just like my own sister.

It didn’t occur to me in that moment that my interpretation of his smile was founded on stories we’d been passing on for generations. It’s only now that I’m beginning to understand that those stories have a history. And that, without us really realizing it, they might shape our children’s present as well as their future.

Excerpted from Second Thoughts: On Having and Being a Second Child by Lynn Berger. Published by Henry Holt and Company, April 20th 2021. Copyright © 2020 by Lynn Berger English translation copyright © 2020 Anna Asbury. All rights reserved.

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