Chris Mooney.

Science journalist Chris Mooney became well-known — and controversial — after his debut book, 2005’s The Republican War on Science, which charted the extraordinary, decades-long assault by the U.S. conservative movement on scientists, scientific institutions, and inconvenient scientific results (see: climate change). He admits to some level of naive hope that a full accounting of the phenomenon would lead to change. But, he says, no one changed their mind about anything. The right just retrenched.

For his new book, The Republican Brain, he set out to discover why. That led him into a burgeoning body of research on the roots of political ideology in deeper psychological traits, brain structures, and even genes — correlations that show up again and again in different circumstances and in different countries. Social scientists, it seems, are busy confirming our gut sense that conservatives and liberals do not merely disagree on matters of policy, but are different kinds of people, who process information differently.

On average, conservatives prefer simplicity and clear distinctions, where liberals display “integrative complexity” and are more comfortable with ambiguity and nuance. Conservatives are “hierarchs” and highly sensitive to in-group/out-group distinctions, where liberals are egalitarians. Conservatives come to decisions quickly and stick to them; liberals deliberate, sometimes to the point of dithering. Conservatives are more sensitive to threats while liberals are more open to new experiences.

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As Mooney emphasizes over and over again in the book, this is not determinism. No substantive belief is “hard-wired.” Our nature does not determine our fate any more than our nurture does. These are averages and tendencies, not destinies, and individuals can be found all along a broad spectrum. Some of the scientific results, particularly the ones related to genetics, are early and highly tentative. Nonetheless, the totality of the science is substantial enough that it no longer makes sense to ignore it. The way we think about politics and democracy must incorporate a fuller picture of human cognition and cultural identity.

Q. One of the objections to the book I’ve seen around is that it places too much value on the social-science behavioral and psychology studies that don’t meet proper scientific standards of rigor — asking people questions outside of bars, etc.

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A. I think scientists have an absolute right to ask people questions outside bars!

It isn’t physics, but after having interviewed the scientists involved in this stuff and asked about uncertainties, etc., it’s clear there’s some firm knowledge now. It’s not like there’s hot counterevidence to the basic point that liberals and conservatives have different personalities. It shows up every single time. It’s not as airtight as climate science, not as airtight as evolutionary science, but that doesn’t mean that there’s no weight of knowledge or understanding here.

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Q. If genes and brain structures and psychology play such a big role in partisan politics, why does the U.S. conservative movement seem qualitatively different from conservative parties in other developed democracies?

A. It’s the shift of U.S. conservatism into being authoritarian conservatism. Not everybody followed us in that. That’s a story of the last 30, 40 years, the story of the conservative revolution in America. Marc Hetherington and Jonathan Weiler, who I talk about in the book, measured how authoritarianism became concentrated in the Republican Party over time.

You can have social change with psychology underlying some aspects of the change. The best explanation is going to be a nature/nurture amalgam, which is what you ultimately get in the book. I never claimed that it was one vs. the other.

Q. The stuff about genes has brought out charges of determinism.

A. It all comes down to people not knowing how genes work. I only spent four pages of the book on genes. I just said there is some evidence of a genetic component in how we differ; I counted something like 10 studies showing a genetic component to political ideology. It doesn’t mean that you lack the ability to change who you are. That doesn’t follow at all! The genetic studies, if they are correct, show that genes control maybe 40 percent of the variability of views, so 60 percent is everything else. That leaves tons of room for all kinds of things to happen to people.

Q. Have social and political changes in the U.S. served to exacerbate or exaggerate these basic psychological differences?

A. Sure. I would point to the growth of conservative think tanks, reinforcing the sense that conservatives have their own evidence, and the growth of the conservative media echo chamber, which has the same effect, more on a mass scale. The echo chamber has the think-tank experts on, but the think-tank experts are mainly for the sophisticated. These are ideology-reinforcing mechanisms. They make you really sure that you’re right.

Q. Do you think it’s worth people’s time to do personality tests?

A. Oh yeah. We should test all the presidents — rather than their tax returns, we should release their personality test.

Q. What do you make of the common critique that scientists have politicized climate science by pushing a liberal policy agenda?

A. There’s maybe a very small percent there. If James Hansen goes and protests at a coal plant and Fox News attacks him for it, who made conservatives not like climate science? It’s complicated. But in most cases where conservatives are being told now that scientists are their enemy, I don’t think the scientists did anything at all to merit it. If you take something like Climategate — the scientists were being ordinary people who weren’t careful enough in their emails. There’s no way they could have known that they would be taken out of context and turned into a souped-up scandal.

Q. You are careful to say in the book that liberal and conservative personalities are yin and yang, complementary, and both can be effective depending on context. But take a problem like climate change: it’s incremental, ambiguous, and ridden with uncertainty and complexity. It implies huge changes in the status quo. From where I’m sitting, it looks like liberal psychology is better suited to grappling with it.

A. I would agree with you that liberals are better optimized psychologically for dealing with a problem like climate change. All I wanted to say was that there are situations in which conservative traits can be a benefit. I’m not saying that they’re all situations in modern life and I’m not saying that it’s even equal. I was just very careful in the book to point out that some of these traits can work out on either side. It’s probably not an accident that human beings have this kind of versatility.

I’ll even defend conservatives a little — in terms of real rigidity, we’re talking about the extremes. But a little sprinkling, a moderate conservative, is going to have some of the traits I’m talking about in an amount that actually leads to a good balance, because it counteracts liberal excesses. I try to point out the liberal blind spots as best I can — things that they can’t see that they’re doing, because of their assumptions, because of their worldview.

Q. It’s sort of disturbing to abandon the view of politics as rational persuasion. Is it disheartening to you?

A. I think I’m a realist. When Jefferson said we need a well-informed public as a foundation for making policy — that view doesn’t understand people very well. There can be reasonable deliberation in certain circumstances, but with all that we now know about identity and reasoning, it’s uglier than that.

We have sectors of society that are more rational than others. It’s tough to talk about now with the Supreme Court case, but in general the legal system is more accurate and deliberative. It does find ways to put checks on some of this stuff, although there’s still a lot of biased views and bad judges and lawyers. There are ways of reforming it to make it more rational. If journalism enforced some norms, like it used to, then a lot of this stuff could be weeded out.

There’s ways we can set up different structures of society — journalism, legal system, scientific community — where there’s reputational risks to not being accurate. There’s a lot of value to that. You lose that if you have echo chambers where you get patted on the back for saying something like, global warming is phony.

In terms of polarization, just arguing facts all the time really does seem to be a trap; it really does seem to just inflame passions on both sides. Because facts are never really what it’s about. Values are what drive the argument. And personalities process information differently. I think that there’s a lot to learn, and we can do better. I’m still a liberal. I just want to make things better.