[I]n the past two decades anthropologists have gathered data on life and death in pre-state societies rather… — Steven Pinker

According to a recent study of the brains of identical and fraternal twins, differences in the amount of gray matter in the frontal lobes are not only genetically influenced but are significantly correlated with differences in intelligence.

But among many professional women the existence of sex differences is still a source of discomfort. As one colleague said to me, "Look, I know that males and females are not identical. I see it in my kids, I see it in myself, I know about the research. I can't explain it, but when I read claims of sex differences, steam comes out of my ears."

The three laws of behavioral genetics may be the most important discoveries in the history of psychology. Yet most psychologists have not come to grips with them, and most intellectuals do not understand them … . Here are the three laws: