In the never ending arguments about nature (heridity) and nurture (surrounding) having more effect on a person the position of the bulk of social scientists is that nurture has more importance. In fact they often hold that heritability is so small that it can be ignored.

In this book author takes the position that the contributions of heritability vs. environment can be measured to determine the separate contributions to the explanation of human psychological differences.

Perhaps the best summary of the author's point of view is the quotation he gives at the beginning of the book. Here the author quotes David Lykken: 'The denial of genetically based psychological differences is the kind of sophisticated error normally accessible only to persons having Ph.D. degrees.'

The rest of the book is concerned with proving this single point, and he does an excellent job.