Average IQ Score Determined by Birth Order?

According to a recent study of nearly 250,000 malesthat child is the first one to require the extra
between 18 and 19 years old, the first-born had anexpenses. For example, the oldest child would most
average IQ score 2.3 points higher than their youngerlikely be the first to want to take a class of some
siblings. Doesn't sound like much, right? But, those 2.3kind, get involved in sports, go to college, etc.
points increase a child's chances of getting into an IvyThe theory that one of the researchers thinks is
League school by 30 percent. The results also provedmost accurate is called "niche partitioning". Basically,
that IQ is, at least in part, determined by social birththe oldest child is given the most authority and
order and not by genetics, putting an end to a nearlyresponsibility, therefore the parents tend to see him
70 year old debate.as a surrogate parent to the younger siblings. This
But, don't start resenting your older brother just yet.higher ranking then drives the later-born children to
While the 2.3 points are fairly significant, they onlyfind their "niche" in the family.
reflect the educational potential of an individual. So,Because older children already occupy the "disciplined
even if you weren't the first to arrive on the sceneand wise" niche, younger children have to find other
in your family, you are still entirely capable of beingroles to play. "So, younger siblings look for other
more successful than all of your siblings combined. It'sthings to be good at," said Frank J. Sulloway, a
all about how you use what you've got.visiting scholar at the University of California,
There are several theories as to why first-bornBerkeley, Institute of Personality and Social Research.
children usually have higher IQ's. One, they are usually"It may be that that extra 2.3 points in IQ reflects an
given undivided attention during their earlyinvestment of time to get that, and the later-born is
developmental years. As additional children are born,investing that time in something else and is getting
the attention of the parents is spread more thinly2.3 extra points in something else," he added.
across the entire family.Given that each child is finding his or her own niche,
Another possible explanation, parents usually spendthe difference in IQ is nothing for parents to worry
more money on the oldest sibling, simply becauseabout, Sulloway said.