Why do we do things that we know are bad for us? Why do we line up to buy greasy fast food that is terrible for our bodies? Why do we take the potentially lethal risk of cosmetic surgery to have a smaller nose, bigger lips, or a less wrinkled face? Why do we risk life and limb in a fit of road rage to seek revenge against someone who merely cut us off in traffic? If these life choices are simply responses to cultural norms and pressures,...