If you have siblings, you've definitely heard this before—that you’re “totally the middle child” or that you've always been spoiled “because you're the baby.” In fact, it's quite ingrained into our society that our personalities can be largely determined by where we stand when it comes to birth order in relation to our siblings.
You may have even found that some of the things people say about birth order checks out when it comes to you and your brood. Take it as a coincidence, though, because the research is clear—the order in which siblings are born means nothing, and we’ll tell you why.
What are the stereotypes, anyway?
As early as the 1900s, people were taking notice of how siblings could be so different from one another. A scientist named Francis Galton began to notice that many of his colleagues tended to be firstborn children in their families and wondered if that had anything to do with their successes in their fields. He determined that, since firstborn sons were the family heirs at that point in time, that they often became more successful and productive members of society because their families gave them more attention and resources.
The entire theory that birth order determines personality traits first came about in the 1920s. A man named Alfred Adler, who was actually a colleague of famed psychologist Sigmund Freud, came up with several ideas based around his own family, in which he was the middle child. He deduced from his own experiences that—
The eldest child was a natural leader but could often be self-centered and slightly neurotic, due to the fact that the second child had “de-throned” them.
The middle child, he theorized, would be the rebellious one—healthy and full of independence.
The baby would naturally be more immature, outgoing, and especially spoiled.
Since then, we've essentially turned these theories into facts.
In some ways, there is some merit to them. In 2007, The New York Times reported on study from Norway published in Science and Intelligence journals that determined that firstborn sons have an IQ that is, on average, two to three points higher than that of their younger siblings.
Catherine Salmon, Ph.D., a co-author of The Power of Middle Children, says, “Middle-borns don’t have the rights of the oldest or the privileges of the youngest,” which is what often helps them learn how to compromise and become confident negotiators.
When it comes to the babies of the family, though, Salmon said, “Parents are more lenient, so youngest kids tend to be less rules-oriented, and yet they still get lots of attention,” which is what might make them more adventurous and childish.
However, new studies are shaking up the theories we’ve clung to for centuries.
A recent study published in 2015 in Proceedings of the National Academy of Sciences examined over 20,000 individuals from not only the United States, but from Germany and the United Kingdom as well. It compared siblings within one family, along with people who had the same birth order within their family. What'd the researchers find out? “All in all, we did not find any effect of birth order on extraversion, emotional stability, agreeableness, conscientiousness, or imagination, a subdimension of openness,” they said.
One of the core components that drives the many theories behind birth order and personality lies in the believe that, evolutionarily, siblings must find different ways to gain their parents’ attention and affection, which gets harder as more siblings are added to the bunch. However, the study doesn't support this belief because, if it were true, the researchers believe the effects of it on personality would be much more pronounced when the children were younger and still living together.
Another study published by the Journal of Research in Personality, also from 2015, followed 377,000 high school students within the United States. The researchers tracked what they called the “Big Five” personality traits: extraversion, openness, neuroticism, agreeableness, and conscientiousness. They predicted that, “firstborns (versus laterborns) should be higher in Conscientiousness, Neuroticism, and the dominance aspect of Extraversion, whereas laterborns should be higher in Agreeableness and the sociability aspect of Extraversion.”
They found that the differences were minute, though.
While the research revealed that firstborns were slightly more dominant and contentious and were also less sociable, they were typically more agreeable and less neurotic—something most people wouldn't attribute to a firstborn child. Not only that, but they had to look at hundreds and thousands of people to even discover the effect sizes of these differences because they weren't even that prominent. They did find that firstborns often had an IQ one point above their siblings’, but deemed it pretty insignificant—a 2011 study found that IQ can change by up to 20 points while someone is still an adolescent.
They concluded their research by saying, “Birth order is often invoked as an important variable to explain the development of personality and intelligence within and across families. We would have to say that, to the extent that these effect sizes are accurate estimates of the true effect, birth order does not seem to be an important consideration for understanding either the development of personality traits or the development of intelligence in the between-family context.”
So, why do we still pay so much attention to birth order?
Much like zodiac signs and their corresponding horoscopes, these theories about birth order provide us with descriptions of our personality traits that tend to be fairly vague and broad. The fact that they aren't entirely specific allows us to project these traits onto ourselves and feed into what the theories say about us, even if only one specific trait or experience applies.
A University of Wisconsin student named Stacey Armitage wrote a graduate thesis that aimed to determine how sets of siblings viewed themselves after reading Adler’s birth-order descriptions. While she found that the majority of people she interviewed felt that they fit the description that matched their birth order, many of them also clung to certain qualities, most likely because they found them admirable. For example, many of the people Armitage studied would claim they were the most considerate or the most rebellious of their siblings, even if those traits didn't fit their birth order personality description.
Another reason why we think the effects of birth order matter? Adhering to these theories, people are able to explain away any of their undesirable traits or behaviors. For example, someone who’s into astrology might say, “I'm a Leo, so I can't help that I'm always getting attention,” whereas a firstborn child might say, “I can't help that I'm bossy; I'm the oldest!” It's essentially their way of pushing the blame for their negative behavior away from themselves and onto something else.
Though this recent research definitely seems to undermine centuries of belief when it comes to personality and birth order, we don't predict that people will stop putting stock into the hype anytime soon. Perhaps it's because people just enjoy fitting into a specific category, or maybe it's because they have competitive family and enjoy bringing up to their siblings that they're the responsible one, the levelheaded one, or whatever else they might think they are (or who they want to be).
But hey, if they put so much faith into it, you can definitely bring that up the next time your older sibling tries to boss you around or can't follow directions. They should be the smart one, after all.