The book The Bell Curve goes into it in detail. The basic observation is that the only thing predicting results on an intellectual test is the results of a prev

The book The Bell Curve goes into it in detail. The basic observation is that the only thing predicting results on an intellectual test is the results of a previous intellectual test. The correlation is caused by an underlying variable that has been given the name general intelligence. There is no residual correlation with socioeconomic status once the correlation with intelligence has been subtracted. Some politicians call this racism, which is probably why my comment was downvoted. Nothing is further from the truth. The whole point is that less-intelligent people score equally low regardless of race. Why different groups should have different intelligence is probably a result of evolution. It takes a better grade of ancestors to survive 20,000 years of European farming and winters.