If you want one experiment that perfectly captures what science is learning about the deep-seated differences between liberals and conservatives, you need go no further than BeanFest. It’s a simple learning video game in which the player is presented with a variety of cartoon beans in different shapes and sizes, with different numbers of dots on them. When each new type of bean is presented, the player must choose whether or not to accept it—without knowing, in advance, what will happen. You see, some beans give you points, while others take them away. But you can’t know until you try them.

In a recent experiment by psychologists Russell Fazio and Natalie Shook, a group of self-identified liberals and conservatives played BeanFest. And their strategies of play tended to be quite different. Liberals tried out all sorts of beans. They racked up big point gains as a result, but also big point losses—and they learned a lot about different kinds of beans and what they did. Conservatives, though, tended to play more defensively. They tested out fewer beans. They were risk averse, losing less but also gathering less information.

One reason this is a telling experiment is that it’s very hard to argue that playing BeanFest has anything directly to do with politics. It’s difficult to imagine, for example, that results like these are confounded or contaminated by subtle cues or extraneous factors that push liberals and conservatives to play the game differently. In the experiment, they simply sit down in front of a game—an incredibly simple game—and play. So the ensuing differences in strategy very likely reflect differences in who’s playing.



and the Biology
of Political Differences
by John R. Hibbing, Kevin B. Smith, and John R. Alford
Routledge, 304 pp.

The BeanFest experiment is just one of dozens summarized in two new additions to the growing science-of-politics book genre: Predisposed: Liberals, Conservatives, and the Biology of Political Differences, by political scientists John R. Hibbing, Kevin B. Smith, and John R. Alford, and Our Political Nature, by evolutionary anthropologist Avi Tuschman. The two books agree almost perfectly on what science is now finding about the psychological, biological, and even genetic differences between those who opt for the political left and those who tilt toward the right. However, what they’re willing to make of these differences, and how far they are willing to run with it, varies greatly.

Hibbing, Smith, and Alford, a team of researchers at the University of Nebraska-Lincoln and Rice University who have published some of the most penetrating research on left-right differences in recent years, provide a lively and amusing tour of the landscape. But they mostly just walk up to and peer at the overriding question of why these apparently systematic left-right differences exist in the first place. Their explanation for the “origin of subspecies,” as they put it, is tentative at best. Tuschman, by contrast, has written a vast and often difficult book that attempts nothing less than a broad evolutionary explanation of the origins of left-right differences across countries and time—and does so by synthesizing such a huge body of anthropological and biological evidence that it’ll almost bury you. Whether the account deserves to be called merely thought-provoking or actually correct, though, will be up for other scholars to evaluate—scholars like Hibbing, Smith, and Alford.

Let’s begin with the large body of shared ground. Surveying the evidence with a fair mind, it is hard to deny that science is revealing a very inconvenient truth about left and right: long before they become members of different parties, liberals and conservatives appear to start out as different people. “Bedrock political orientations just naturally mesh with a broader set of orientations, tastes, and preferences because they are all part of the same biologically rooted inner self,” write Hibbing et al. The research demonstrating this is so diverse, comes from so many fields, and shows so many points of overlap and consistency that you either have to accept that there’s really something going on here or else start spinning a conspiracy theory to explain it all away.


Our Political Nature: The Evolutionary Origins of What Divides Us
by Avi Tuschman
Prometheus Books, 500 pp.

The most rock-solid finding, simply because it has been shown so many times in so many different studies, is that liberals and conservatives have different personalities. Again and again, when they take the widely accepted Big Five personality traits test, liberals tend to score higher on one of the five major dimensions—openness: the desire to explore, to try new things, to meet new people—and conservatives score higher on conscientiousness: the desire for order, structure, and stability. Research samples in many countries, not just the U.S., show as much. And this finding is highly consequential, because as both Hibbing et al. and Tuschman note, people tend to mate and have offspring with those who are similar to them on the openness measure—and therefore, with those who share their deeply rooted political outlook. It’s a process called “assortative mating,” and it will almost certainly exacerbate our current political divide.

But that’s just the beginning of the research on left-right differences. An interlocking and supporting body of evidence can be found in moral psychology, genetics, cognitive neuroscience, and Hibbing’s and Smith’s preferred realm, physiology and cognition. At their Political Physiology Lab at the University of Nebraska-Lincoln, the researchers put liberals and conservatives in a variety of devices that measure responses like skin conductance (the moistening of the sweat glands) and eye gaze patterns when we’re exposed to different types of images. In doing so, Hibbing and his colleagues have been able to detect involuntary physiological response differences between the two groups of political protagonists when they encounter a variety of stimuli. Once again, it’s hard to see how results like these could mean anything other than what they mean: those on the left and right tend to be different people.

Indeed, here is where perhaps some of the most stunning science-of-politics results arise. Several research groups have shown that compared with liberals, conservatives have a greater focus on negative stimuli or a “negativity bias”: they pay more attention to the alarming, the threatening, and the disgusting in life. In one experiment that captured this, Hibbing and his colleagues showed liberals and conservatives a series of collages, each comprised of a mixture of positive images (cute bunnies, smiling children) and negative ones (wounds, a person eating worms). Test subjects were fitted with eye-tracker devices that measured where they looked, and for how long. The results were stark: conservatives fixed their eyes on the negative images much more rapidly, and dwelled on them much longer, than did the liberals.

Liberals and conservatives, conclude Hibbing et al., “experience and process different worlds.” No wonder, then, that they often cannot agree. These experiments suggest that conservatives actually do live in a world that is more scary and threatening, at least as they perceive it. Trying to argue them out of it is pointless and naive. It’s like trying to argue them out of their skin.

Perhaps the main reason that scientists don’t think these psychological and attentional differences simply reflect learned behaviors—or the influence of cultural assumptions—is the genetic research. As Hibbing et al. explain, the evidence suggests that around 40 percent of the variation in political beliefs is ultimately rooted in DNA. The studies that form the basis for this conclusion use a simple but powerful paradigm: they examine the differences between pairs of monozygotic (“identical”) twins and pairs of dizygotic (“fraternal”) twins when it comes to political views. Again and again, the identical twins, who share 100 percent of their DNA, also share much more of their politics.

In other words, politics runs in families and is passed on to offspring. Hibbing and his coauthors suspect that what is ultimately being inherited is a set of core dispositions about how societies should resolve recurring problems: how to distribute resources (should we be individualistic or collectivist?); how to deal with outsiders and out-groups (are they threatening or enticing?); how to structure power relationships (should we be hierarchical or egalitarian?); and so on. These are, of course, problems that all human societies have had to grapple with; they are ancient. And inheriting a core disposition on how to resolve them would naturally predispose one to a variety of specific issue stances in a given political context.

All of which brings us to the really big question. It is difficult to believe that systematic psychological and biological differences between those who opt for the left and the right in different countries—differences that are likely reflected in the genetic code—arose purely by chance. And yet, providing an evolutionary explanation for what we see is fraught with peril: to put it bluntly, we weren’t there. We didn’t see it happen.

Moreover, in evolution, some things happen for an explicitly Darwinian “reason”—traits become more prevalent or fixed in populations because they advanced organisms’ chances of survival and reproduction in a particular environment—while others happen more accidentally. Some complex social traits may emerge, for instance, because they are a fortuitous by-product of other, more fundamental traits laid down by Darwinian evolution.

A good example of such a trait may be religion. It’s pretty clear that evolution laid down a series of attributes that predispose us toward religiosity, such as “agency detection,” which refers to the human tendency to detect minds and intentions everywhere around us in the environment, even when they aren’t necessarily there. The evolutionary reason for such a trait seems obvious: after all, better to be safe than sorry when you’re out in the woods and hear a noise. But start thinking that there are intentions behind the wind blowing, or the hunt failing, and you are well on your way to constructing gods. And indeed, religion seems to be a cross-cultural human universal. But does that mean that evolution selected for religion itself, or just for simpler precursors like agency detection?

You see the difficulty. In this context, Hibbing and his colleagues consider a variety of potential explanations for the stubborn fact that there is large, politically relevant psychological and biological diversity among members of the human species, and ultimately settle on a tentative combination of two ideas. First, they assert, conservatism is probably more basic and fundamental, because it is more suited to a world in which life is “nasty, brutish, and short.” Being defensive, risk aversive, hierarchical, and tribal makes sense when the threats around you are very real and immediate. As many of these threats have relaxed in modern times, however, this may have unleashed more variability among the human species, simply because now we can afford it. Under this scenario, liberals are the Johnny-come-latelys to the politico-evolutionary pageant; the Enlightenment itself is less than 300 years old, less than an eyeblink in evolutionary time. “Liberalism may thus be viewed as an evolutionary luxury afforded by negative stimuli becoming less prevalent and deadly,” write Hibbing et al.

However, Hibbing and his colleagues also consider a more controversial “group selection” scenario, in which evolution built some measure of variability in our political typologies because sometimes, diversity is strength (for the group, anyway, if not for the individual). The trouble is, it is still fairly novel for evolutionary explanations to focus on the reproductive fitness of a group of individuals, rather than on the fitness of a single individual or even that individual’s DNA. Nonetheless, it’s easy to see why a group of early humans comprised of both conservative and liberal psychologies might have fared better than a more homogenous group. Such a society would have forces in it that want to hunker down and defend, but also forces that push it to explore and change. This would surely make for better adaptation to more diverse environments. It just might enhance the group’s chance of survival.

Yet it would be going much too far to suggest that Hibbing et al. have a strong or highly developed theory for why biopolitical diversity exists among humans. Avi Tuschman does, though. “Political orientations are natural dispositions that have been molded by evolutionary forces,” he asserts. If he’s right, a dramatic new window opens on who we are and why we behave as we do.

One of the most stunning revelations of recent genetic anthropology is the finding that Homo sapiens, our ancestors, occasionally bred with Homo neanderthalensis in Europe or the Middle East some 40,000 to 50,000 years ago. These encounters may have been quite rare: just one offspring produced every thirty years, according to one estimate. But it was enough to shape who humans are today. Recent genetic analyses suggest that some modern humans have a small but measurable percentage of Neanderthal DNA in our genomes—particularly those of us living in Europe and Asia.

The more you think about it, the more mind-boggling it is that this cross-species mating actually occurred. Imagine how strange it must have been, as a member of Homo sapiens, to encounter another being so closely related to us (much more closely than chimpanzees), and yet still so different. J. R. R. Tolkien buffs can probably visualize it the best, because it would indeed have been something like humans encountering dwarves. Neanderthals were shorter and stronger, with outjutting brows. There is some evidence suggesting that they had high-pitched voices and red hair.

Knowing how prevalent racism and xenophobia are today among members of the same human species, we can assume that many of our ancestors would have behaved even worse toward Neanderthals. And yet some Homo sapiens bred with them, produced offspring with them, and (presumably) cared for those offspring. Which ones were the lovers, not the haters?

The answer, hints Tuschman in Our Political Nature, is that it may have been the liberals. For one core of the apparently universal left-right difference, he argues, is that the two groups pursue different reproductive strategies, different ways of ensuring offspring and fitness in the next generation.

And thus we enter the realm of full-blown, and inevitably highly controversial, evolutionary explanations. Tuschman doesn’t hold back. Conservatives, he suggests in one of three interrelated evolutionary accounts of the origins of politics, are a modern reflection of an evolutionary impulse that leads some of us to seek to control sexual reproduction and keep it within a relatively homogenous group. This naturally makes today’s conservatives more tribal and in-group oriented; if tribalism does anything, it makes it clear who you are and aren’t supposed to mate with.

Tuschman’s liberals, in contrast, are a modern reflection of an evolutionary impulse to take risks, and thereby pull in more genetic diversity through outbreeding. This naturally makes today’s liberals more exploratory and cosmopolitan, just as the personality tests always suggest. Ultimately, Tuschman bluntly writes, it all comes down to “different attitudes toward the transmission of DNA.” And if you want to set these two groups at absolute war with one another, all you need is something like the 1960s.

According to Tuschman, these competing reproductive strategies arise from the fact that there are advantages to keeping mating close within the group, but also advantages to mixing in more genetic diversity. Moreover, there is a continuum from extreme inbreeding to extreme outbreeding, featuring many different reproductive strategies along the way. Thus, we see in other species, such as birds like the great tit, a range in mating behavior, from a high level of breeding with more closely related birds to a high level of outbreeding.

Outbreeding brings in diversity, which is vital. For instance, diversity in the genes that create the proteins that ultimately come to comprise our immune systems has obvious benefits. But outbreeding also has risks—like encountering deadly new pathogens when you encounter new human groups—even as a moderate degree of inbreeding appears to have its own advantages: perpetuating genetically based survival strategies that are proven to work, increasing altruism that arises in kin relationships, and also, it appears, having more total offspring.

Extreme inbreeding, to be sure, is deleterious. But Tuschman presents evidence suggesting that there is an optimum—at around third-cousin or fourth-cousin mating—for producing the largest number of healthy offspring. He also shows related evidence in Danish women suggesting that a moderate degree of geographic dispersal to find a mate (measured by the distance between a woman’s birthplace and her husband’s) is related to having a high number of children, but too much dispersal and too little are both related to less overall fertility.

Returning to the present, Tuschman emphasizes that conservatives, and especially religious conservatives, always want to seem to control and restrict reproduction (and other sexual activities) more than liberals do. It’s understandably hard for an evolutionary biologist not to see behaviors that systematically affect patterns of reproduction in a Darwinian light.

And it’s not just reproductive patterns: Tuschman also suggests that other aspects of the liberal-conservative divide reflect other evolutionary challenges and differential strategies of responding to them. He traces different left-right views on hierarchy and equality to the structure of families (a move that cognitive linguist George Lakoff has in effect already made) and the effect of birth order on the personalities and political outlooks of siblings. And Tuschman traces more positive and negative (or, risk-aversive) views of human nature on the left and the right to different types of evolutionarily based altruism: altruism toward kin on the conservative side, and reciprocal altruism (which can be toward anyone) on the liberal side.

But is all of this really … true? Tuschman’s book is difficult to evaluate on this score. It says so much more about evolution than Hibbing, Smith, and Alford do, and yet manages to do so without leaving the same impression about the importance of caveats and nuances. Is Tuschman advancing a group selection theory, or not? It sometimes sounds like it, but it isn’t clear. And most importantly, is the variation among humans of politically relevant traits just part of the natural order of things, or does it itself reflect something about evolution? Again, it isn’t clear. This is not to suggest that Tuschman lacks a view on such questions; it’s just that he synthesizes so much scientific evidence that this kind of hand-holding seems less of a priority.

In the end, Tuschman’s book attempts a feat that those of us monitoring the emerging science of politics have long been waiting for—explaining the now well-documented psychological, biological, and genetic differences between liberals and conservatives with reference to human evolution and the differential strategies of mate choice and resource allocation that have been forced on us by the pressures of surviving and reproducing on a quite dangerous planet. It may or may not stand the test of time, but it certainly forces the issue.

In the end, what’s so stunning about all of this is the tremendous gap between what scholars are learning about politics and politics itself. We run around shutting down governments and occupying city centers—behaviors that can only be driven by a combination of intense belief and equally intense emotion—with almost zero perspective on why we can be so passionate one way, even as our opponents are passionate in the other.

To see politics as Hibbing, Smith, Alford, and Tuschman see it, by contrast, is inevitably to want to stop fighting so much and strive for some form of acceptance of political difference. That’s why, even though not all of the answers are in place yet, we need their line of thinking to catch on. Ideological diversity is clearly real, deeply rooted, and probably a core facet of human nature. Given this, we simply have no choice but to come up with a much better way to live with it.

Buy these books from Amazon and support Washington Monthly: Predisposed: Liberals, Conservatives, and the Biology of Political DifferencesOur Political Nature: The Evolutionary Origins of What Divides Us

Chris Mooney

Chris Mooney is a reporter for Climate Desk (climatedesk.org) and cohost of the Inquiring Minds podcast.