might undermine the temptations of violence, the Prisoner’s Dilemma. In his popular Scientific American column, the computer scientist Douglas Hofstadter once agonized over the fact that the seemingly rational response in a one-shot Prisoner’s Dilemma was to defect.266 You cannot trust the other player to cooperate, because he has no grounds for trusting you, and cooperating while he defects will bring you the worst outcome. Hofstadter’s agony came from the observation that if both sides looked down on their dilemma from a single Olympian vantage point, stepping out of their parochial stations, they should both deduce that the best outcome is for both to cooperate. If each has confidence that the other realizes that, and that the other realizes that he or she realizes it, ad infinitum, both should cooperate and reap the benefits. Hofstadter envisioned a superrationality in which both sides were certain of the other’s rationality, and certain that the other was certain of theirs, and so on, though he wistfully acknowledged that it was not easy to see how to get people to be superrational.
Can higher intelligence at least nudge people in the direction of superrationality? That is, are better reasoners likely to reflect on the fact that mutual cooperation leads to the best joint outcome, assume that the other guy is reflecting on it as well, and profit from the resulting simultaneous leap of trust? No one has given people of different levels of intelligence a true one-shot Prisoner’s Dilemma, but a recent study came close by using a sequential one-shot Prisoner’s Dilemma, in which the second player acts only after seeing the first player’s move. The economist Stephen Burks and his collaborators gave a thousand trainee truck drivers a Matrices IQ test and a Prisoner’s Dilemma, using money for the offers and payoffs.267 The smarter truckers were more likely to cooperate on the first move, even after controlling for age, race, gender, schooling, and income. The investigators also looked at the response of the second player to the first player’s move. This response has nothing to do with superrationality, but it does reflect a willingness to cooperate in response to the other player’s cooperation in such a way that both players would benefit if the game were iterated. Smarter truckers, it turned out, were more likely to respond to cooperation with cooperation, and to defection with defection.
The economist Garrett Jones connected intelligence to the Prisoner’s Dilemma by a different route. He scoured the literature for all the Iterated Prisoner’s Dilemma experiments that had been conducted in colleges and universities from 1959 to 2003.268 Across thirty-six experiments involving thousands of participants, he found that the higher a school’s mean SAT score (which is strongly correlated with mean IQ), the more its students cooperated. Two very different studies, then, agree that intelligence enhances mutual cooperation in the quintessential situation in which its benefits can be foreseen. A society that gets smarter, then, may be a society that becomes more cooperative.
Intelligence and Liberalism. Now we get to a finding that sounds more tendentious than it is: smarter people are more liberal. The statement will make conservatives see red, not just because it seems to impugn their intelligence but because they can legitimately complain that many social scientists (who are overwhelmingly liberal or leftist) use their research to take cheap shots at the right, studying conservatism as if it were a mental defect. (Tetlock and Haidt have both called attention to this politicization.)269 So before turning to the evidence that links intelligence to liberalism, let me qualify the connection.
For one thing, since intelligence is correlated with social class, any correlation with liberalism, if not statistically controlled, could simply reflect the political prejudices of the upper middle classes. But the key qualification is that the escalator of reason predicts only that intelligence should be correlated with classical liberalism, which values the autonomy and well-being of individuals over the constraints of tribe, authority, and tradition. Intelligence is expected to correlate with classical liberalism because classical liberalism is itself a consequence of the interchangeability of perspectives that is inherent to reason itself. Intelligence need not correlate with other ideologies that get lumped into contemporary left-of-center political coalitions, such as populism, socialism, political correctness, identity politics, and the Green movement. Indeed, classical liberalism is sometimes congenial to the libertarian and antipolitical-correctness factions in today’s right-of-center coalitions. But on the whole, Haidt’s surveys show that it is the people who identify their politics with the word liberal who are more likely to emphasize fairness