It's a fact that reading, studying and thinking increases the synapses in the brain. We Jews are a people of the book. We have studied Torah, among other things, for millennia. So, over thousands of years, as a people, we have gotten smarter and smarter. We LOVE to read and learn and to study. That gets passed down genetically. Schooling and doing well in school is stressed in Jewish homes and Jewish children have no choice but to buckle down and do well. I am speaking of Jews here "on the whole." This is obviously not true for each and every Jewish household. But this is a general truth, as I see it. It's actually kind of obvious that if, as a people, you love to read, learn and study, then you'll produce some very smart people over the years.
Regarding the Chinese: In so many Chinese families, studying and doing well is very much stressed. Combine that with the fact that there are billions of Chinese people, then the laws of averages will guarantee you some very smart Chinese people. If there were billions of Jews, you can only imagine how much even greater the accomplishment of Jews would be. As it is, Jews are an amazing people, just looking at their percentage in the world and the percentage of Nobel Prizes we have won.
As a general rule (yes, I'm generalizing here), Blacks in America do not focus on studying and getting high marks in school. As a matter of fact, doing well in school is called "acting White" and is frowned on -- in many communities. This puts them at an enormous disadvantage as compared with, say, Jews or Chinese.
