and all the other resources are poured into one child instead of being spread around several children. Thus only child has higher IQ and development level than when there are several of them.
"A twenty-year tracking study of 3,000 high school students demonstrated that only children have higher IQs than their peers with one sibling -- in fact, "there are marked negative effects on IQ of increasing sib size."
--- end of citation --
There are also similar results of first child having higher IQ than second - as all the attention goes to him/her during the critical first years of brain development while second child doesn't have such undivided attention.
> "A twenty-year tracking study of 3,000 high school students demonstrated that only children have higher IQs than their peers with one sibling -- in fact, "there are marked negative effects on IQ of increasing sib size."
I didn't see any mention of household income in the NYT article. I'm interested to know if the researchers factored in household income because from what I've read, people with higher incomes tend to have higher IQs and fewer children, and intelligence is heritable.
the driver of adaptation, survival and progressive development of the species [and its civilization if any] are not necessarily the ones who live happy and prosperous life.
30+ years ago China made a choice between 2 alternatives - "1B population with IQ 135" or "2B population where 1B has IQ 130 and 1B has IQ 120" (the specific values 135/130/120 are just for illustration)
and all the other resources are poured into one child instead of being spread around several children. Thus only child has higher IQ and development level than when there are several of them.
http://www.nytimes.com/books/first/m/mckibben-one.html
"A twenty-year tracking study of 3,000 high school students demonstrated that only children have higher IQs than their peers with one sibling -- in fact, "there are marked negative effects on IQ of increasing sib size."
--- end of citation --
There are also similar results of first child having higher IQ than second - as all the attention goes to him/her during the critical first years of brain development while second child doesn't have such undivided attention.