Human beings are primates, and primates are political animals. Our brains, therefore, are designed not just to hunt and gather, but also to help us get ahead socially, often via deception and self-deception. But while we may be self-interested schemers, we benefit by pretending otherwise. The less we know about our own ugly motives, the better - and thus we don't like to talk or even think about the extent of our selfishness. This is "the elephant in the brain." Such an introspective taboo makes it hard for us to think clearly about our nature and the explanations for our behavior. The aim of...