Women lose a quarter of their maternal urges for every 15 extra IQ points they have, according to international research.
Using data from Britain's National Child Development Study, Mr Kanazawa studied the links between intelligence and maternal urges in women. He found more of the former meant less of the latter.
Even after adding controls for economics and education, the results remained the same - the more intelligent the woman, the less likely she was to have children.
Mr Kanazawa published his findings in his book, The Intelligence Paradox, and the research into the number of children compared with IQ was in the chapter titled "Why intelligent people are the ultimate losers in life".
He found that the more intelligent both men and women were in their childhood, the fewer children they wanted when they were older. Those who wanted no offspring when they were young had a mean IQ of 105.5, almost 7 points higher than those who did want children.
But while the level of intelligence affected whether women reproduced later in life, it did not affect men.
Mr Kanazawa, who lived in Christchurch for a year, said: "More intelligent women have fewer children in their lifetimes than less intelligent women. In contrast, more intelligent men, despite having wanted to have fewer children at age 23, do not actually have fewer children by age 47."
And he did not believe that smart women choosing to not have children had anything to do with their desire to pursue academics or a career. The psychologist believed that only childhood intelligence, not educational achievement or earnings, decreased the number of children women had.
I think it's got nothing to do with intelligence as such over the long term, it's just a reaction by intelligent girls to the type of society we live in today, and the past few decades, and the impressions those girls have of what they need to do in order to get ahead in life. Right now the messages are to not have or to limit children, and the more intelligent are going to pick up on that, thinking that's the right thing to do.
This could have a negative impact on how smart society was.
Except that women don't tend to be excessively intelligent. We are typically clustered around the centre of the scale, with very few women being incredibly stupid and very intelligent. Unlike men who are strung out more with a higher number being stupid and also a higher number being intelligent. There far more average intelligent women than there are men as a result.
"If more intelligent women have fewer children, and are more likely to have fewer children, and are more likely to remain childless, then one potential consequence is that the average level of general intelligence in society may decline over time."
Mensa New Zealand member and clinical psychologist Dr Aloma Parker said the lowering of society's general intelligence was a possibility, but unlikely because research showed traits tended to drift back to the norm.
Dr Parker has an IQ of above 133 and is in the top 2 percentile. She also has two children.
But she agrees that smarter women do have a tendency to have fewer children, especially since the advancement of birth control.
My intelligence is at the top 0.25% percentile and I have had two children. I wish I had had more. I decided to only have two when I was young and that's how it turned out. I don't think it was a particularly intelligent idea to only limit myself to two children and to plan my life accordingly, but then when I was young I was picking up on the messages that society gave and that was that it was more important for women to be productive workers than have children. I have now overcome a great deal of the false societal programming of my youth, but it's too late for me to have more children. All I can do it warn others. I might end up having a bigger impact by doing that than if I had just had more children. Maybe. :)
Related link: Smarter women have fewer children, researcher discovers ~ NZ Herald