Unlike your previous correspondents on black-white IQ differences (Letters, March 31), we are specialists on this subject. For nearly 100 years, the data have shown that in dozens of studies throughout Africa, in Britain, the US and the Caribbean, black people have lower average IQ scores than white people. There is a clear overlap in the black and white IQ distributions.
The scientific debate is mainly over the causes of the average differences. We have concluded that genetic factors have a role to play in this difference, as evidenced by the fact that black infants adopted and brought up by white middle-class parents show little improvement in their IQ scores by late adolescence.
IQ is also related to brain size, where the races also differ. It is the lower average IQ scores of blacks that contributes to their poorer performance in school and later on to their lower earnings.
Many other scientists have reached the same conclusion as us. Thus, Frank Ellis has done no more than restate what has been well known and accepted for many decades by those who have expertise in this subject.
J. Philippe Rushton
University of Western Ontario