There is a popular belief that the behavior of children in a
family depends a lot on their birth order.
First-born children are supposed to be fairly conformist, because they
do not have to compete for their parents’ attention and resources at the start
of their lives. They have a favored
status that leads them to identify with authority. Middle children have to fight hard for attention,
and so they may rebel as a way of getting noticed. This effect should be mixed for the youngest
in a family. On the one hand, they also
have to compete for attention. As the youngest, however, they may get some
amount of attention just for being the last child.
This idea has also been put forward within the psychology
community. For example, Frank Sulloway
wrote the popular book Born to Rebel essentially making
this case.
Some data have been collected that support this idea. In typical analyses, researchers find
large-scale surveys that measure rebellious behaviors in teens (like drinking,
marijuana use, and nonviolent crime) and then look to see whether birth order
in families predicts the delinquent behavior.
The typical finding is that middle children are most likely to exhibit
these behaviors, and first born children are least likely to display them.
The problem with these analyses is that they are typically
done between families. That is, the
children all come from different families, and so it is hard to know for sure
whether birth order is the true cause of the effect or whether it is some other
variable like parental involvement in the family that is causing the observed
relationship.
A paper in the August, 2013 issue of Personality and Social Psychology Bulletin by Patrick Cundiff found a data set that allowed him to tease
apart these effects. He analyzed the Add
Health survey that was collected on school children from 1994-2008. This survey collected information about a
variety of children’s behaviors. The
survey also contained a lot of data about siblings within a family. The survey also had information about
potential confounding factors like socioeconomic status, grade point average in
school, and parental involvement in the home.
Cundiff did both a between family and a within family
analysis of the data. The between family
analysis used all of the children in the sample (over 14,000), while the
within-family analysis used only the data from 3,800 children where the entire
family was observed.
The between-family analysis showed the same effects as
previous research. This analysis found that
middle children were about 33% more likely to exhibit delinquent behaviors than
firstborn children. Last born children
were about 20% more likely to exhibit these behaviors than firstborn children. Examination of a variety of aspects of the
children like grade point average and aspects of families like parental
closeness did not eliminate the effect of birth order.
However, when the data set looked only within families, the
relationship between birth order and delinquent behavior was sharply reduced in
size and was no long statistically significant.
In this analysis, only gender and parental involvement had a reliable
effect on behavior. That is, boys were
more likely to engage in delinquent behavior than girls, and children with a
low level of parental involvement were more likely to engage in delinquent
behavior than children with a high level of parental involvement.
This paper is consistent with a growing body of evidence
suggesting that there are few reliable effects of birth order on children’s
behavior. Thus, while it is intuitively reasonable to think that firstborn and
later-born children differ, it does not look like that is really happening.
