Friday, August 09, 2013

The Headline 'Smarter Women Have Fewer Children' is an Excellent Illustration of Why Correlation is Not Causation

A Japanese researcher who likes to provoke controversy, Satoshi Kanazawa, has proclaimed that women with high IQs have few or no children.  This leads him to proclaim in his book The Intelligence Paradox that "the urge to have kids among women drops by 25 percent with every extra 15 IQ points above a certain rate."

The correlation is likely true.  The causation, though, is not likely to be that high IQ leads women to want fewer children, and certainly not that the highest IQ women want no children.

Rather, high IQ women have many choices in life, and are much more likely to have long years of education and highly demanding jobs than lower IQ women do.  Therefore, the whole population of high IQ women is likely to have fewer children than women with average or low IQs.  The correlation, though, is not the cause.


Anonymous said...

More likely the causation is too complex for a blogpost (or comment) of this nature but has more to do with more higher IQ women chosing not to have children outside of a stable relationship and more men opting not to engage in stable relationships with women of higher IQs.

Diane M said...

@Anonymous - at this point in American society, higher IQ and more educated women are more likely to have stable long-term relationships.

I'm not sure what countries the data is based on, though.

Diane M said...

So my theory is that this is not about whether or not women want more children. It's about whether or not women can have as many children.

If you go to school longer and start having children later, you end up having fewer children.