Photo by Mcarls/CC-BY-SA, via Wikimedia Commons.
Source: Photo by Mcarls/CC-BY-SA, via Wikimedia Commons.

Everybody knows that first, second, and third-born children have particular personality characteristics determined by their position in the family: Firstborns are achievers, middle children are peacemakers, and the babies in the family are individualists. Influential books like Frank Sulloway’s Born to Rebel (1996) and Jeffrey Kluger’s The Sibling Effect: Brothers, Sisters, and the Bonds That Define Us (2011) say so. These stereotypes have become so much a part of our consciousness that I recently got a jokey Christmas catalogue with models on the cover sporting t-shirts proclaiming “I’m the Oldest/I Make the Rules,” “I’m the Middle/I’m the Reason We Had Rules,” and “I’m the Youngest/The Rules Don’t Apply to Me,” with the caption, “Wear it proud because it’s the truth!”

There’s only one problem: It isn’t.

A major new study demonstrates conclusively that, contrary to what those t-shirts take for granted—and most psychologists consider gospel—“birth order itself has no effect on character.”

The researchers in this head-clearing investigation—the lead author was Julia Rohrer of the University of Leipzig, and the original results appeared in the journal Proceedings of the National Academy of Sciences—used an enormous database of more than 20,000 people, drawn from three major international studies. The team looked for differences in everything you can think of and then some—extraversion, emotional stability, agreeableness, conscientiousness, self-reported intellect, IQ, imagination, and openness to experience. They analyzed data on brothers, sisters, small and large age gaps, and different family sizes. “But,” as a New York Times article on the study reported, “no matter how they spliced the data, they could find no association of birth order with any personality characteristic.”

The only detectable effect was that older children have very slightly higher IQ scores, but that may well be an artifact of the large sample size. The lead author of the study states, categorically, “There is no such thing as a typical older, middle or younger sibling.”

Why, then, do so many people swear by a phenomenon that does not exist? They want it to be true.

We find comfort in patterns that seem to make rational sense—patterns that are universal and predictable—and birth order seems to answer complex and mysterious questions about the origins of personality and the role of family dynamics in shaping who we are. It’s easier to seek explanations in superficial qualities, to focus on the outside rather than the inside. But when we look more closely, we see that every family, and every member of a family, is unique.

If birth order is irrelevant as a general explanation, then, what really does determine family dynamics? A combination of the personality traits and genders of the particular children who occupy each ordinal position—and the meaning parents attribute to these characteristics. Parents consciously or unconsciously assign specific roles to each child based on their own childhood sibling experience, and how their own parents perceived and treated them. This hidden factor contributes to the enormous variation the researchers uncovered. The role of the past, including events that occurred before people were even born, is potent but largely overlooked because of its subtlety and complexity.

When I give talks about siblings—I’ve written two books on the subject, and treating “normal” siblings of the disabled and dysfunctional is my therapeutic specialty—someone always asks about birth order. I respond by telling the following incident that happened in my own extended family:

A distant cousin of mine has always been bitterly estranged from both her mother and her sister, who is 10 years older. When I asked why, she told me that her mother had installed a dog gate on her teenage daughter’s door to prevent her toddler sister from bothering her. The teenager tortured her little sister by taking her beloved stuffed animals and refusing to return them, and her mother turned a blind eye, never punishing the culprit or comforting the victim. How, I wondered, could this otherwise caring mother—whom I knew—do something like that? How could she do something guaranteed to estrange her daughters from each other, and the younger one from her?

Golden Pixels LLC/Shutterstock
Source: Golden Pixels LLC/Shutterstock

My cousin knew why her mother did it. “She had been a teenager herself when a new baby was born, and this baby was shamelessly favored over her and allowed to get away with murder,” she explained to me. And her mother, when she had children herself, unconsciously vowed to right this wrong in the next generation, bending over backward to compensate her own teenage daughter for what she herself had suffered at her own mother’s hands. Of course, the plan backfired horribly: Instead of righting a wrong, she created its mirror image.

One size never fits all.

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