Red Brain, Blue Brain

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SHANKAR VEDANTAM, HOST:

This is HIDDEN BRAIN. I'm Shankar Vedantam. We start today with an account of two communities. One is liberal, the other conservative. I want you to guess which is which.

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JOHN HIBBING: The schools would stress patriotism and respect. And it would be a very rules-based educational system. The houses would be fairly similar. The lawns would be very nicely kept and beautifully green and mowed. The town would be quiet, with lots of churches.

VEDANTAM: That's town one. Here's town two.

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HIBBING: The schools would be based more on experiential kinds of things rather than rote memory. People would prefer older houses with wooden floors rather than wall-to-wall carpeting. They would keep the yards natural - lots of bars and community theaters and foreign films, more of those than churches.

VEDANTAM: That was easy, right? Conservatives like order. Liberals embrace ambiguity. Now, you may be rolling your eyes or even getting angry at these stereotypes. But we all know there's more than a grain of truth to them. So how did these two towns, which our guest today refers to as Liberalville (ph) and Conservaton (ph), get this way?

When most of us think about how we came to our political views, we tend to have a straightforward explanation. We use our upbringing and life experiences as the basis for our political beliefs. We imagine that our parents, teachers and friends shape our views on everything, from taxes and the economy to immigration and national security. But what if I told you there is something deeper to those attitudes, drives that shape the music we listen to, the food we eat, the politicians we elect? This week on HIDDEN BRAIN, how the partisan divide in our country might arise not just from our upbringing and lived experiences, but from biology.

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VEDANTAM: On a regular basis, right before an election, someone will share an article with me about how science proves that the brains of liberals are stunted. Or a post on Twitter will say, Republicans are less intelligent than Democrats. These claims obscure something far more interesting and far more accurate.

There are genuine psychological differences between liberals and conservatives. Understanding these differences can give us fresh insight into our political conflicts. John Hibbing is a political scientist at the University of Nebraska\u2013Lincoln. He has spent many years studying the psychological and neurological differences between liberals and conservatives. He is co-author of the book, "Predisposed: Liberals, Conservatives, And The Biology Of Political Differences." John, welcome to HIDDEN BRAIN.

HIBBING: Thank you, Shankar, pleasure to be with you.

VEDANTAM: When most of us think about how we came to our political views, John, we have a relatively straightforward explanation that has to do with our upbringing and background. How does that theory go?

HIBBING: Well, whenever I ask my students where their political views come from, the first thing they say is their parents.

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HIBBING: And I think we have this sense that those views that our parents have passed along are supplemented by those, you know, from a clergy member or a trusted relative, a close friend. But we sort those through our own view of the world. And we come to a very rational understanding of the world and an understanding of what social policies are best to make the world better.

VEDANTAM: So we're going to look in-depth at some of the psychological and brain differences that do exist between liberals and conservatives. But I want to start by looking at how differences between partisans are not limited to politics. These differences show up in many domains that have nothing to do with politics. Republican President George H. W. Bush once spoke about an issue that had bothered him for many years.

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GEORGE H. W. BUSH: I do not like broccoli.

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BUSH: And I haven't liked it since I was a little kid. And my mother made me eat it. And I'm president of the United States. And I'm not going to eat any more broccoli.

VEDANTAM: What do food differences tell us about liberals and conservatives?

HIBBING: Well, we tend to see that there are differences in tastes. Conservatives do like meat and potatoes more. Liberals are more likely to prefer ethnic food. So you see that. And that, we think, is part of a deeper pattern of conservatives are a little bit fonder of kind of predictability, of standard kinds of things. And liberals are a little bit more willing to experiment. And this comes through in food tastes and a variety of other things.

VEDANTAM: Here's another example. Researchers once went into the living spaces of people - offices and dorm rooms. And they recorded the items that they saw. What was different about the living and work spaces of liberals and conservatives?

HIBBING: Well, conservatives tended to have lots of things like sports memorabilia, whereas liberals tended to have more experiential things - lots of books, lots of CDs, especially diverse CDs, whereas conservatives were more likely to have things that organized their lives - calendars, clothes baskets. Also the researchers suggested the liberals' rooms were not quite as tidy or as well-lighted as the conservative rooms and offices.

VEDANTAM: There's even been some research looking at differences in our preferences for different kinds of pets. I understand Jonathan Haidt and others have explored that liberals and conservatives gravitate to different kinds of dogs.

HIBBING: Different kinds of dogs - it tends to be the case that conservatives prefer purebreds. And liberals will go with mixed-breed dogs. There are some studies that suggest how you view pets - there isn't that much difference in how many have pets. Both liberals and conservatives like to have pets at about equal level. But they might view them somewhat differently. Liberals are a little bit more likely to view them as part of the family rather than, you know, just a pet. So you have those kinds of very interesting things, not just in pet ownership, but kind of in orientation to the pet.

VEDANTAM: The patterns that John and others have identified are more than just curious. These patterns suggest that our model of political differences is wrong in an important way. Liberals and conservatives don't just have different political preferences. They have different temperaments. Conservatives don't just care about lower taxes. They also care about whether poetry rhymes.

HIBBING: That's right. Should poetry rhyme? We also ask, you know, are you more comfortable with novels that end with clear resolution, those kinds of things. And, you know, you can start to see a pattern already, I think, in our discussion, that it is the case that liberals are more likely to say, sure, I'm OK with free verse, whereas conservatives say, no, you know, we really think there should be a pattern. Music should come back to a recognizable melody. Poetry should rhyme. And novels should - should wrap up in a way that we are comfortable with.

VEDANTAM: To be clear, the differences John identifies are averages. So you can certainly have a Republican who likes free verse and a Democrat who hates jazz. The point of this research isn't to stereotype liberals and conservatives but to show that our political choices flow from deeply ingrained psychological differences. Many of us don't realize how our choices as consumers - the cars we buy, the food we eat, the music we listen to - that these choices inadvertently reveal our political preferences.

So I'm happy to tell people on Facebook what kind of music I listen to. But I imagine that they wouldn't be able to tell from that whether I was a Democrat or a Republican. I asked John about research that suggests you can tell whether someone's a conservative or a liberal if you know what kind of movies they watch, what kind of food they eat, what kind of vacations they take.

HIBBING: It's very reasonable that people would not resonate with that line of argument because to them, it's not like they say, well, you know, in order to be a good conservative, I need to do this - or in order to be a good liberal. So you know, they're just being themselves. And I think that's the real message here, is that our political beliefs are part and parcel of our entire being. You know, it's not like they're completely separate. And it's just a natural outgrowth of these larger psychological and even physiological tendencies that we've been talking about.

VEDANTAM: When we come back, the psychological traits and brain differences that shape our political choices and preferences. Stay with us.

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VEDANTAM: I want to start with one of the most important differences you and others have identified when it comes to politics. Liberals and conservatives differ when it comes to how they see threats and danger. Here's Wayne LaPierre of the National Rifle Association.

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WAYNE LAPIERRE: We know, in the world that surrounds us, there are terrorists, and there are home invaders, drug cartels, carjackers, knockout gamers and rapers and haters and campus killers, airport killers, shopping mall killers...

VEDANTAM: So talk about this difference, John. When liberals hear this, what do they hear? When conservatives hear this, what do they hear?

HIBBING: Yeah, it really is a remarkable quote. I remember Jon Stewart played this once on "The Daily Show." And after the clip, they pan back to Stewart...

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JON STEWART: Where the [expletive] do you live?

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HIBBING: ...And he was hiding behind his desk.

VEDANTAM: (Laughter).

HIBBING: So, you know, you get the sense that if you listen to this very long, you're scared of everything. The message that I take from this is that, you know, you play this to liberals, and they say, this guy is nuts. You know, others have told me he's just doing it because he makes millions of dollars from the NRA, and he doesn't really believe it.

I think he does. These threats are very real to him, and we're not going to get anywhere unless people who don't feel that way understand that some people do. And likewise, the Wayne LaPierres of the world need to understand that for some people, they just - you know, they don't see the world as threatening as he does. And they don't think we need to build our society around mitigating those threats.

VEDANTAM: So, you know, when a liberal like Jon Stewart hides behind the desk, partly what he's doing is he's mocking Wayne LaPierre. He's sort of saying, this is ridiculous. It's beyond ridiculous to imagine that all these threats are basically around us. We live in a relatively safe society. And basically, what Jon Stewart is communicating is, you know, what you're saying doesn't make any sense. And what you're saying is, it might not make sense to you. But it makes sense to Wayne LaPierre.

HIBBING: Exactly. You know, one of the favorite things for conservatives to say about liberals is that they just don't get it - meaning that, you know, they don't appreciate that it's a dangerous world. And I think that is absolutely true. But it's not that they don't get it because they're being obtuse or they're not informed. They read about events in the world, and they just don't respond to them in the same way.

And likewise con - liberals, rather, need to recognize that while this may seem silly - and you're right about Jon Stewart mocking this - you know, how can you live your life worried and whatever. But to them, this is very real. And a good citizen is vigilant and is prepared to do battle to protect himself, his family and society from those threats.

VEDANTAM: What's interesting about both groups here is that there is a very powerful illusion that we have that the rest of the world sees the world the way that we see the world. And if they come to a different conclusion, it must be because they're being deliberately obtuse or somehow deliberately biased, as opposed to the idea that people are actually - they might be seeing the world the same way, but their reactions to world might actually be very different.

HIBBING: Yeah, I'm really glad you brought that up. Psychologists talk about false consensus. So it turns out that if your favorite color is blue, you grossly overstate the percent of the population whose favorite color is blue. So, you know, I think we need to recognize that. We did a study once. There's a substance, androsterone - it turns out that people smell it very differently. It's just because our olfactory systems are structured differently. Some people smell it very favorably. It smells like kind of cookies or incense. Others smell it unfavorably. It'll smell like sweat or even urine. And some don't smell it at all. And it's a genetically based difference. So we had a bunch of our graduate students smell this. And I remember one fellow, and he smelled it, and it just smelled awful to him. And it didn't smell awful to many of the other graduate students. And he was convinced that this was some kind of psychological trick, that we were trying to, you know, get him to say, well, yeah, it doesn't smell bad. It was one of those studies. When in fact, he just couldn't believe that people were that different in the way they smelled this substance. And I think the same thing applies to political beliefs and to the way we experience threats in the world.

VEDANTAM: I remember one of the things that broke the Internet recently was the big controversy about whether people heard the word laurel...

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COMPUTER-GENERATED VOICE: Laurel.

VEDANTAM: ...Or heard the word yanny.

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COMPUTER-GENERATED VOICE: Laurel.

VEDANTAM: But this idea that, you know, the way that we see, hear, something must be the way everyone else sees it, and there's just this feeling of utter disbelief that other people might not see and hear the world the same way.

HIBBING: Yeah, it's just what we're used to. It makes sense to us. So I do think that's something we need to continue to pound away on - that we really are wired up quite differently.

VEDANTAM: Let's look at how this plays out when it comes to the subject of immigration. Here is Republican Donald Trump.

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PRESIDENT DONALD TRUMP: They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people.

VEDANTAM: And here is Democrat Nancy Pelosi.

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NANCY PELOSI: We are constantly reinvigorated by immigrants coming to our country. Their commitment and courage and commitment to the American dream, which drew them here in the first place, strengthens the American dream.

VEDANTAM: Now, it's important to stipulate here, John, that it's entirely possible - these are politicians. They might indeed be saying things that are just politically strategic. But how might differences in threat perception shape the way liberals and conservatives in general think about the subject of immigration?

HIBBING: Yeah, I really think - you know, immigration, defense, police, law and order - I think this is really at the core of who we are and at the core of political differences. So, you know, if I am a person like Wayne LaPierre who feels these threats and thinks they're all around us, then it seems to me I would want a set of policies put forward by our government that helped to reduce those threats. And how am I going to do this? I'm going to do it by allowing people to be well-armed. I'm going to do it by spending a lot on defense. I'm going to empower police. I'm going to have the death penalty. And I'm going to not allow immigrants to come here. Or if they do, they are going to be extremely vetted, as the president's once said. So you know, those, I think, to a threat-sensitive mindset, are steps that - you know, they only make sense. They just can't really understand why anybody would be opposed to those kinds of things because this would help us to be a safer place.

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VEDANTAM: Now, there are all kinds of confounding factors when it comes to studying how politicians speak in the actual world, political considerations that are difficult to disentangle from psychological and biological traits. But John and others have studied these differences in experimental settings. John once showed liberals and conservatives positive and negative pictures, and he found they reacted very differently.

HIBBING: A positive picture would be something like a beautiful sunset or somebody enjoying themselves on a ski slope, a happy child. A negative picture would be things like a house that had just been leveled by a hurricane or a guy eating worms or children who are malnourished. We had people hooked up to some physiological devices. The most obvious one is electrodermal activity or skin conductance, which is a common way of seeing if somebody is just having a reaction - having a physiological arousal to that stimulus. And what we found is that people do have arousals when they see these kinds of images because they have some emotional content. But we tended to find that liberals were more reactive to the positive images, and conservatives are more reactive to the negative images.

VEDANTAM: I understand that in one brain-imaging study that you conducted, volunteers were shown disgusting images. And brain activation from even a single image was actually pretty good at being able to tell who was liberal and who was conservative.

HIBBING: That's true. There have been three or four studies that attempt to see if the brain activation patterns of liberals and conservatives is different. And the one that we did goes back to kind of our favorite thing, which is to show them these different kinds of pictures. Actually, we had the most luck with pictures of mutilations. And you're right. When we did that, it was very easy to categorize people, you know, without knowing anything about them. All we would look at was the brain scan results. And we could be incredibly accurate knowing whether they were liberal or conservative just on the basis of that. Liberals' brains, when they looked at mutilation images, were much more active in a part of the brain called the S2, somatosensory 2. And this is part of the brain that will be activated if you suffer pain. So if I kick you in the shin, your somatosensory 2 would be active. But it's also active if you see pain in others. And so if you would see a movie of somebody stepping on a rusty nail - goes right through their foot - your somatosensory 2 would be active. And what we saw in these brain scans was that liberals were more likely to have activation in the somatosensory 2 than conservatives. Doesn't mean that conservatives are hard-hearted; it just means that things are happening differently when they see these different images.

VEDANTAM: Now, you could argue that a lot of this research is correlational. You could also argue that a lot of the patterns that John and others find are consistent with the power of upbringing in shaping political preferences. Here's how. Let's say I'm raised in a conservative home. I learned to be politically conservative from my parents, but my family also influences all kinds of other things about me that have nothing to do with politics. They shape the kind of food I like to eat, the kind of movies I like to watch, the kind of sports I enjoy. By this line of reasoning, the fact that liberals and conservatives are different on all manner of things isn't about biology. It just shows you how your family environment can affect lots of things about you.

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VEDANTAM: There's a really interesting way to separate the effects of biology from the environment. Think about fraternal and identical twins. Identical twins have identical genes. Fraternal twins have similar but not identical genes. If you follow a group of fraternal and identical twins, each twin pair is raised in the same household. Each pair eats the same food, listens to the same conversations, watches the same movies. Now, if you find differences between identical twins as a group and fraternal twins as a group, that suggests that biology, not environment, is the driver. I asked John what such studies reveal about political preferences.

HIBBING: We were fortunate to have access to a data set. It's very large - includes thousands and thousands of twin pairs, collected by a guy named Lindon Eaves long ago. It's a fairly dated data set, but it was a valuable one for us because it included lots of information about their political views. And when we subjected these data to the standard twin design approach, we did indeed find that the political views were quite heritable. Although, people oftentimes misread this, our results suggested that maybe 30 or 40 percent of our political views come from genetics. But, you know, that bothered a lot of people, and this was quite a controversial study in political science. Many people didn't like that at all, and they tended to over-interpret those results and make it sound like we were saying that everything was genetic. But, you know, if it's 30 to 40 percent genetic, that obviously leaves, you know, 50, 60, 70 percent that comes from the environment. So all we're saying is that that genetic component is not zero, but apparently that was enough that some people were upset about that.

VEDANTAM: And so you basically - you're able to tell, in some ways, that there is a closer link in the political orientation of identical twins than in the political orientation of fraternal twins. And that tells you that there is some element of the biology, some element of genetics, that is driving political preferences.

HIBBING: Exactly. Now, that's well put. And again, it's nice to compare political views with other kinds of things. Height, for example, turns out to be about 80 percent heritable when you see these - when you subject it to the same kind of design. Personality traits are about 56 percent. Political views - 30 to 40 percent, I would say.

VEDANTAM: One of the big implications of all of this work, besides just being interesting in itself, is that it helps us, I think, think about the political conflicts we have with fresh insight. And you've made the case that in many ways, the more we are able to see the differences between groups of people as inherent or biological, in some ways, it changes the way we think about those differences. Talk to me about that idea, John.

HIBBING: Yes. When other traits have been understood to be biological - I'm thinking of something like handedness. You know, we used to think that if you were left-handed, that was just because you got into a lazy habit. My father was left-handed, and the teacher - you know, this was long ago - would beat him on the hand with a ruler whenever he wrote with his left hand, trained him to write with his right hand. So we viewed that as a flaw, as something that need to be driven out. Of course, now we understand that being left-handed is very biological. This is something much deeper than just a lazy habit. Or, of course, you know the big one today would be sexual orientation. When people realized that sexual orientation is indeed biologically-driven and not something that they just have decided to do, then people are much more tolerant of that. So we were wondering if perhaps the same thing might happen with regard to politics. If we realize that our political opponents were not simply being lazy but rather were oriented to the world in a different fashion, that maybe we would be a little bit more tolerant of them, that this is the only way we're going to get anywhere if we at least understand where they're coming from, even if we still might deeply disagree with their conclusions.

VEDANTAM: What would you say to critics who would say, you know, the argument that psychological traits and biological differences are beneath our deep political conflicts doesn't make sense because we didn't always have this deep divide in our country between liberals and conservatives. There was a time when we had many, many more people in the center. The most liberal Republican was often to the left of the most conservative Democrat. And, you know, there really has been a sorting of the political parties in recent years. What explains this change, especially over the last 20, 30 years?

HIBBING: What I would say to that argument is that I believe we have always had this very same division, this very basic difference between people who are fairly sensitive to threats and think we need to be vigilant and those people who are more into experimentation and trying new things. Ralph Waldo Emerson has a great quote, and I'm sorry I can't give it to you verbatim. But it's basically that the division between those people who are supporters of tradition and those people who are supportive of innovation is very old and has structured the world since time began.

VEDANTAM: John Hibbing is a political scientist at the University of Nebraska-Lincoln. He has spent years studying the psychological and neurological differences between liberals and conservatives. Along with Kevin Smith and John Alford, he is the co-author of the book, "Predisposed: Liberals, Conservatives, And The Biology Of Political Differences." John, thanks for joining me today on HIDDEN BRAIN.

HIBBING: Thank you, Shankar. It was a pleasure to be with you.

VEDANTAM: This episode of HIDDEN BRAIN was produced by Thomas Lu and edited by Tara Boyle and Camila Vargas-Restrepo. Our team includes Rhaina Cohen, Jenny Schmidt, Parth Shah and Laura Kwerel. Our unsung hero of this week is Alex Yang. Alex works with our IT team at NPR. He recently helped us update our archiving systems. Throughout the process - and this was a massive undertaking involving more than 100 HIDDEN BRAIN episodes - he answered all our endless questions without once rolling his eyes. Thank you, Alex. You can find more HIDDEN BRAIN on Facebook and Twitter. If you liked the show, please tell one friend about us today. Again, if you love HIDDEN BRAIN, take one moment, think of one friend and spread the word. I'm Shankar Vedantam, and this is NPR. Transcript provided by NPR, Copyright NPR.