There's all kinds of stereotypes about
what your position in your family says
about you. Oldest kids are the most
responsible, the ones in the middle are
rebels and since I'm the youngest, I must
be spoiled. And sorry only children,
according to society you're selfish. It's
called birth order theory. And it might
sound like an appealing way to explain
why your older brother is so overbearing
and competitive, or why your younger
sister always has to get what she wants.
But even though psychologists have used
birth order theory to explain
personality traits for decades,
recent studies are finding that it
doesn't actually seem to matter where
you are in your family.
The theory dates way back to 1908, the
early days of psychology, when it was
proposed by Austrian psychologist Alfred
Adler, a buddy of famous psychoanalysts
Freud and Jung. All three of them agreed
that experiences a person had as a kid
could have big impacts on their
personality as an adult. Adler took it
one step further and argue that a
child's position in their family would
have a big impact on their development
because each kid would experience a
different psychological environment. In
his writings he theorized that the
firstborn child starts out as the
spoiled only child and is basically
dethroned when the next sibling comes
along after getting bumped, the oldest
child ends up overbearing and neurotic
since they feel responsible for looking
after their younger siblings. Middle born
children on the other hand, they're
likely to feel overlooked and become the
rebels of the family. And the youngest
children might be babied by their
parents, so according to Adler they
typically end up the most spoiled. Adler
never used any scientific research to
justify his theory but he used it as a
therapeutic tool when working with his
clients anyway. As the idea became more
popular, psychologists realize that they
should probably do some actual research
to find out if birth order theory was
actually true. Personality is a complex
thing to try and quantify and it can
change over time, but scientists have
figured out a way to sort of measure
personality using what's known as the
five factor model or just the Big Five.
It's not so much a theory of personality
as it is a way to categorize different
traits on sliding scales. People can take
a test to see where they fall on the
scales of five traits; openness to
experience, conscientiousness,
extraversion, agreeableness, and
neuroticism. Based on a handful of early
studies, some psychologists are pretty
convinced that you can connect birth
order to specific big five traits. Like
oldest children are more conscientious
and neurotic while youngest children are
more open to new experiences. And this
approach is really appealing because it
sounds totally plausible right? Like I
have an older brother, he's pretty neurotic.
But those earlier studies have a lot of
flaws and the more recent research with
bigger better design studies, hasn't
found much of a connection between birth
order and Big Five personality traits.
One of the problems with those smaller
studies was that they often depended on
one sibling self-reporting their
personalities and those of their
siblings, like what I just did. So if the
researchers were interviewing an oldest
child for example, the subject was more
likely to report that they were more
responsible, while their free-spirited
little brother was more open. But the
difference between the way someone sees
themselves, and how they see someone else,
can really affect the result of the
survey. New studies had other flaws too,
for instance they mostly looked at the
differences between siblings within the
same family and they interviewed
everybody around the same time, which
meant that the people born first were
always older than the siblings they were
being compared to. So if the researchers
found that firstborns tended to be more
responsible was that because they were
born first or because people just tend
to get more responsible as they get
older. So even though some of those early
studies did seem to find a link between
birth order and personality, their flaws
meant that the results weren't super
reliable. Now more recently, researchers
have been using much bigger data sets to
analyze differences in large groups of
kids from multiple Western countries. And
it turns out that once you start
comparing traits across families and
looking at more subjects, the effects
tend to go away. In two huge studies
published in 2015, scientists were able
to compare tons of different kids across
lots of different families. One of the
studies looked at almost 400,000 US high
school students, and the other included
over 20,000 students from the US, UK, and
Germany. The one difference they found,
and if you are an older sibling I expect
you to hold this over your younger
siblings, was a small change in
intellect, which is considered one of the
sub traits of openness in the big five.
Siblings born first tend to have a very
slightly higher IQ than siblings born
later. We're talking like a couple
of points. It could come from firstborn
kids getting a little bit more direct
attention from their parents at an early
age. But as we talked about before here
on Scishow Psych, IQ is just a way to
measure learning ability, and that's only
one part of the complex concept of
intelligence. And it can be affected by
lots of different things like how
motivated you are to do well on the test.
And other studies looking at things at
the data haven't found an affect of
birth order on IQ at all. Other than that,
these gigantic studies found no
significant effect of birth order on any
of the other big five traits. So most
psychologists treat birth order theory
with a healthy amount of skepticism
these days, although it hasn't been
totally disregarded. Birth order might be
an appealing way to explain differences
in the behavior of siblings, but when you
look across large groups of families, the
effects just aren't there. You might know
individual people who fit the stereotype
of an oldest sibling who's more
responsible, or a youngest who seems
spoiled, but there are also plenty of
responsible youngest children or oldest
children who act like total brats. Over
time and across populations those traits
balance out. So birth order theory
doesn't actually explain why your middle
sister ran off to start a rock band,
that's just because she's awesome.
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