People Believe in Birth Order Theory, But Is It True?

a cartoon family
Image by Pixabay / CC 0

“Oh, you know how middle children are.”

“He’s just acting like a firstborn.”

“Well, she’s an only child, so…”

I can’t tell you how many times I’ve heard something like the above. Birth order theory, the idea that people’s personalities vary depending on their order of birth within their family, is incredibly popular.

Where did the notion of birth order theory come from? And has it held up to research?

It’s All Alfred Adler’s Fault

Birth order theory was one of psychology’s earliest hypotheses, formulated in the early days by Alfred Adler, an Austrian psychiatrist who was a contemporary of Freud and Jung. He argued that birth order was an integral part of a child’s development and affected how they made friends, developed romantic relationships, and started careers.

Adler argued that oldest children experience the subsequent birth of siblings as an attack on them, an unseating of their place in the hierarchy as the primary objects of their parents’ attention. He also argued that middle children feel lost in the crowd, leading them to developing “middle child syndrome.” And he also argued that younger and only children are pampered and spoiled.

Firstborns Are Kinda Smart, But That’s It

The idea took off. And is still widely believed. However, like many of the earliest psychological hypotheses that were formed in the early days of psychology (when the field lacked empirical rigor), birth order theory hasn’t held up under research.

Recent research on the interplay of birth order and personality has only found a single significant finding: Firstborns score slightly higher than individuals found elsewhere in the birth order on measures of intelligence.

However, there seem to be no birth-order-related effects on other personality measures such as extraversion, emotional stability, agreeableness, conscientiousness, or imagination.

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Disclosure regarding potential bias: The author of this article is a middle child (the third of four children).

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This post is part of an ongoing Poly Land feature called Psyched for the Weekend, in which I geek out with brief takes about some of my favorite psychological studies and concepts. For the entire series, please see this link.

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