In the second-to-last chapter of his excellent book The Better Angels of Our Nature: Why Violence Has Declined, Harvard University psychology professor Steven Pinker writes, in a short section subtitled "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 leftist or liberal) use their research to take cheap shots at the right, studying conservatism as if it were a mental defect. (Fetlock and Haidt have both called attention to this politicization.) So before turning to the evidence that links intelligence to liberalism, let me qualify the connection.
What is the qualification? He writes:
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. (italics in original)
In the next section, subtitled "Intelligence and Economic Literacy," Pinker writes:
And now for a correlation that will annoy the left as much as the correlation with liberalism annoyed the right. The economist Bryan Caplan also looked at data from the General Social Survey and found that smarter people tend to think more like economists (even after statistically controlling for education, income, sex, political party, and political orientation).
They are more sympathetic to immigration, free markets, and free trade, and less sympathetic to protectionism, make-work policies, and government intervention in business.
Of course none of these positions is directly related to violence. But if one zooms out to the full continuum on which these policies lie, one could argue that the direction that is aligned with intelligence is also the direction that has historically pointed peaceward.
To think like an economist is to accept the theory of gentle commerce from classical liberalism, which touts the positive-sum payoffs of exchange and its knock-on benefit of expansive networks of cooperation. That sets it in opposition to populist, nationalist, and communist mindsets that see the world's wealth as zero-sum and infer that the enrichment of one group must come at the expense of another.
The historical result of economic illiteracy has often been ethnic and class violence, as people conclude that the have-nots can improve their lot only by forcibly confiscating wealth from the haves and punishing them for their avarice. As we saw in chapter 7, ethnic riots and genocides have declined since World War II, especially in the West, and a greater intuitive appreciation of economics may have played a part (lately there ain't been much work on account of the economy).
At the level of international relations, trade has been superseding beggar-thy-neighbor protectionism over the past half-century and, together with democracy and an international community, has contributed to a Kantian Peace.
Just as Dorothy Boyd said to Jerry Maguire, "You had me at hello," I would say to Steven Pinker "You had me at 'think like an economist.'"