We can try to become more aware of the patterns governing our blunders, as “Predictably Irrational” urges. Or we can try to prod people toward more rational choices, as “Nudge” suggests. But if we really are wired to make certain kinds of mistakes, as Thaler and Sunstein and Ariely all argue, we will, it seems safe to predict, keep finding new ways to make them. (Ariely confesses that he recently bought a thirty-thousand-dollar car after reading an ad offering FREE oil changes for the next three years.)

If there is any consolation to take from behavioral economics—and this impulse itself probably counts as irrational—it is that irrationality is not always altogether a bad thing. What we most value in other people, after all, has little to do with the values of economics. (Who wants a friend or a lover who is too precise a calculator?) Some of the same experiments that demonstrate people’s weak-mindedness also reveal, to use a quaint term, their humanity. One study that Ariely relates explored people’s willingness to perform a task for different levels of compensation. Subjects were willing to help out -- moving a couch, performing a tedious exercise on a computer -- when they were offered a reasonable wage. When they were offered less, they were less likely to make an effort, but when they were asked to contribute their labor for nothing they started trying again. People, it turns out, want to be generous and they want to retain their dignity -- even when it doesn’t really make sense.