statistics, the past 20 years, covered the US, China, Japen, Some Europe countries,
for every additional kid, his/her IQ goes down 2.5 point.
the main reason, is that at the early stage childhood of kids, the first born child talk to two adults; the second child talks to two adults and one child, .... The tenth child, had almost no chance to talk to an adult.
for every additional kid, his/her IQ goes down 2.5 point.
the main reason, is that at the early stage childhood of kids, the first born child talk to two adults; the second child talks to two adults and one child, .... The tenth child, had almost no chance to talk to an adult.
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