Two psychologists give us the lowdown.
It’s just over a week until Christmas and families around the country are getting ready to come together for a time of joyful-handholding, laughs and mutual love…
SAID NO ONE EVER.
The holidays are universally a stressful time. Every dysfunctional (even semi-functional) family are suddenly forced to traverse the delicate spaces between various members, hoping neither to enrage anyone or become enraged. Perhaps the most volatile relationships of all are the ones between siblings.
Conventional wisdom tells us it’s toughest being the middle child. They’re squished between the oldest kid who got undivided attention from newbie parents and the youngest who gets more freedom and special privileges as the “baby” of the family. What does the middle child get? A whole pile of resentment.
No one summed up the stereotype quite like Jan Brady from the Brady Bunch with her whiney middle-child-anthem, “Marcia, Marcia, Marcia!” Popular culture also gave us the forever-suffering Malcolm from Malcolm in the Middle and Lisa Simpson, The Simpsons family misfit.
Australia psychotherapist Alfred Adler is attributed with coming up with the idea in the 1920s that birth order is determinative of personality, but how much scientific evidence really exists for theories like middle-child syndrome? In fact, does birth order have any bearing on personality or IQ at all? We asked two experts for the answers.
Dr. Rodica Damian, an Assistant Professor of Social and Personality Psychology at the University of Houston, was the first author on the largest study yet of birth order and personality published last year.
About the same time, psychologist Julia Rohrer from the University of Leipzig was part of a team of German researchers who analysed data from 20,000 people from three nations in one of the most comprehensive studies to date.
Edited for brevity
Why do you think the idea that birth order has an effect on personality and IQ is so popular?
Damian: I think the main reason is that everyone can relate and can provide anecdotal evidence on how they are different from their siblings or on how other people are different from their siblings. The big issue is that, in this case, daily observation will always be biased because siblings are always of different ages, and age has a huge impact on developmental processes and maturation.
Rohrer: You might selectively search for and interpret information that confirms your beliefs about birth order position. In my experience, this type of confirmation bias is most visible for the case of only children. Someone is egocentric and an only child? Typical only child!
But if the only child instead acts selfless, you will probably not attribute her behavior to the fact that she is an only child but find a different explanation.
There’s also bad science: Psychologists have published a lot of studies that "prove" birth order effects on pretty much every personality trait imaginable, and these studies often made their way into the popular press and pop science books ...This type of research – analysing the data until you find something and then wrapping everything up in a nice narrative to get it published – has turned out to be a huge problem for psychology as a science.
In the last five years, a lot of supposedly rock-solid findings could not be replicated: One team of researchers finds that amazing effect that gets a lot of press coverage; but a second team of researchers tries to run the very same study and does not find anything.
What stereotypes do you hear about birth order?
Damian: The funny thing is that everyone believes the "theory" says whatever they want. They believe so strongly in anecdotal evidence and their personal experiences that they believe everyone else has the same experiences and compares in the same way with their siblings. Truth is, there is so much variability in those experiences that the overarching pattern of a correlation between birth order and personality at the population level is close to zero.
Rohrer: I think the most common ones are the more mature but also bossy firstborn, the disadvantaged middle ("sandwich") child, and the spoiled last-born. Those stereotypes might even mirror some actual family dynamics: Firstborns are sometimes more mature because they are older and they can afford to be more dominant because they are often larger and stronger than their younger siblings. Middle-born children might indeed struggle to get their parents undivided attention and last-borns probably do profit from the fact that the parents have more experience after having raised multiple children.
However, the important thing is that these factors do not have a lasting, significant impact on one's personality, which is why we cannot find reliable birth order effects on adults' personalities in settings outside of the family.
What were the main results of the studies you were each part of?
Damian: Personality effects were close to zero and some of them were not in the direction predicted by birth order theories, first borns were slightly higher in almost all the traits.
Rohrer: We found that there is a very weak but reliable decline in average intelligence from firstborns to lastborns.
On an individual level, a group mean level difference of one IQ point is pretty much meaningless. For example, if you are a second-born, you are either approximately as smart as your older sibling, or smarter, or less smart. A small difference between the average firstborn and the average second-born just means that it is a bit more likely that your older sibling is smarter than you; it does not rule out that you are smarter than your older sibling.
Even if birth order had a reasonably strong impact on personality, the effects would not turn out to be deterministic: I am quite certain that there are no deterministic effects in personality psychology, which is why we are only talking about probabilities and averages.
What did you find most surprising about the results?
Damian: The fact that the effect was almost zero overall!
Rohrer: I was quite surprised how the three quite different samples we used – one from Germany, one from the United Kingdom, one from the United States – all resulted in the same conclusion: Reliable birth order effects on intelligence and personality traits that are tightly linked to the intellectual domain; no meaningful birth order effect on the other traits (extraversion, emotional stability, agreeableness, and conscientiousness).
What do you think your research means for families around the holiday season? Should we finally stop blaming birth order for our dysfunctional sibling relationships?
Damian: Yes! I'm not saying birth order can't affect your life! It sure can! Historically, firstborns inherited the parents' wealth, not to mention entire kingdoms, and positions of power. But it is a social construct, it affects our lives because of the meaning we attribute to it and the decisions we make based on it, not because it somehow magically makes us different from each other.
Rohrer: For the holiday season, I would suggest that we keep in mind that personality can be highly context dependent. The psychologist Judith Harris claims that there are indeed systematic birth order effects, but they only really matter within the family context.
You might show a specific "first-born personality" whenever you interact with your siblings, but it simply does not transfer to interactions outside of the family. So if anyone – regardless of their birth order – is being bossy, or complaining, or acting entitled, it might help to recall than they are probably quite different and maybe even more likeable in a different context.