Still, the relationship between IQ and success is hardly arbitrary, and it’s no accident that universities take such tests so seriously. They reveal abilities such as mental speed and the capacity for abstract thought, and it’s not hard to see how these abilities aid intellectual pursuits. Indeed, high intelligence is not only related to success; it’s also related to kindness. Highly intelligent people commit fewer violent crimes (holding other things, such as income, constant) and are more cooperative, perhaps because intelligence allows one to appreciate the benefits of long-term coordination and to consider the perspectives of others.

Then there’s self-control. This can be seen as the purest embodiment of rationality, in that it reflects the working of a brain system (embedded in the frontal lobe, the part of the brain that lies behind the forehead) that restrains our impulsive, irrational, or emotive desires. In classic studies of self-control that he conducted in the 1960s, Walter Mischel investigated whether children could refrain from eating one marshmallow now to get two later. What he found was that the kids who waited for two marshmallows did better in school and on their SATs as adolescents, and ended up with better self-esteem, mental health, relationship quality, and income as adults. In his recent book, The Better Angels of Our Nature, Steven Pinker notes that a high level of self-control benefits not just individuals but also society. Europe, he writes, witnessed a thirtyfold drop in its homicide rate between the medieval and modern periods, and this, he argues, had much to do with the change from a culture of honor to a culture of dignity, which prizes restraint.

What about the capacity for moral judgment? In much of social psychology, morality is seen as the paradigm case of insidious irrationality. Whatever role our intellect might play in other domains, it seems largely irrelevant when it comes to our sense of right and wrong. Many people will tell you that flag burning, the eating of a deceased pet, and consensual sex between adult siblings are wrong, but when pressed to explain why, they suffer what Jonathan Haidt has described as “moral dumbfounding.” They flail around trying to find reasons, which suggests it’s not the reasons themselves that guided their judgments, but their gut intuition.

But as I argue in my book Just Babies, the existence of moral dumbfounding is less damning than it might seem. It is not the rule. People are not at a loss when asked why drunk driving is wrong, or why a company shouldn’t pay a woman less than a man for the same job, or why you should hold the door open for someone on crutches. We can easily justify these views by referring to fundamental concerns about harm, equity, and kindness. Moreover, when faced with difficult problems, we think about them—we mull, deliberate, argue. I’m thinking here not so much about grand questions such as abortion, capital punishment, just war, and so on, but rather about the problems of everyday life. Is it right to cross a picket line? Should I give money to the homeless man in front of the bookstore? Was it appropriate for our friend to start dating so soon after her husband died? What do I do about the colleague who is apparently not intending to pay me back the money she owes me?