How America Polarized

Polarization has always been with us. What has kicked it into overdrive?

Kevin Dorst
Feb 3 · 9 min read

Becca and I grew up in a Midwestern college town. Our friendship was built around small-town life: college football, barbecues by the lake, and so on. If you had asked us about politics, we both would’ve been fairly moderate—and unconcerned—in our replies. It just didn’t matter much, we thought.

Then we went our separate ways. I, to a liberal, urban university; she, to a conservative, rural college. Life got more complicated. Our friendship faded.

And, as you can guess, we polarized.

In the years sense, I’ve become increasingly liberal, and she’s become increasingly conservative. Now, we think, politics really matters.

Our story is typical of the modern American story: one of increasing—and increasingly predictable—polarization.

But what exactly does that mean? In what sense have Americans polarized — and in what sense is the predictability of this polarization new?

That’s a huge question. Here’s the short of it.

Polarization has always been with us. A set of basic psychological and sociological mechanisms explain why human societies have always been characterized by local conformity and global diversity: there tends to be agreement within small social circles, but disagreement between them. As a result, when people go off on different life trajectories, it’s normal for their attitudes to drift apart.

What’s changed is that a series of factors have come together to align these various mechanisms, and kick them into overdrive. Now, when people go off on different life trajectories, their opinions diverge in predictable and consistent directions, and do so faster and farther than before.

There are many moving parts in a full story of modern polarization. As a representative example, focus on me and Becca. There are three questions we want to answer:

  • In what sense have we “polarized”?

In What Sense Have We “Polarized”?

There are three distinct “polarizations” that Becca and I — and the United States in general — have gone through in recent decades.

The first is ideological sorting.

My views have become more consistently liberal and aligned with those of the Democratic Party. Becca’s views have become more consistently conservative and aligned with those of the Republican Party.

In 2010, I was pro-choice and Becca was pro-life, but we were both un-opinionated about gun rights. Yet in the decade since, my views have become more consistently Democratic — I am now both pro-choice and anti-gun. Meanwhile, Becca’s views have become more consistently Republican — she’s now both pro-life and pro-gun.

The second is affective polarization.

Our views of the opposing party have become increasingly negative.

In 2010, most of my friends were conservative, and as a result I had quite a bit of respect for the Republican Party. Today, I have to wrack my brain to think of people I know who might have voted for Trump; and — I must admit — I’ve come to dislike Republicans more, and understand where they’re coming from less. A similar story, no doubt, governs Becca’s opinions toward Democrats.

The third is attitude polarization.

Our disagreements over political questions have become much sharper.

If, in 2010, you’d have asked us whether it would be good for the country for a Republican to be elected president in 2020, Becca would’ve been mildly inclined to agree and I’d have been mildly inclined to disagree. What if you ask us today? We’d both admit that the last election felt like a matter of life or death for our country. Becca thought, “If Biden wins, the police will be abolished and we’ll be cast into socialism!” I thought, “If Trump wins, the norms that uphold our democracy will be under direct assault!”

So Becca and I have “polarized” in that (1) our attitudes became more consistently opposed, (2) our feelings toward the other side became more negative, and (3) our disagreements became increasingly sharp.

This process is pervasive.

  • The United States has become increasingly ideologically sorted by politics — for example, the proportion of people with consistently liberal or consistently conservative positions more than doubled between 1994 and 2014.

So Americans have always been polarized, but that polarization has kicked into overdrive in recent decades.

Given that, we need to know two things: Why, in general, do societies polarize? And what has changed to make this more severe in recent decades?

Why Do Societies Polarize?

Psychologists and sociologists have long known of a set of mechanisms that drive people to have stronger (and more conflicting) attitudes over time — especially when they are put in different social and informational environments.

First mechanism: Most obviously, and most simply, people are persuaded by arguments. That means that if two people enter different environments in which they’ll tend to encounter arguments for different positions, their opinions will predictable diverge.

Since I was headed to a liberal university, I could expect to hear arguments in favor of progressive taxation and the existence of oppressive sexism; and since Becca was headed to a conservative college, she could expect to hear arguments in favor of the value of capitalism and the importance of being a good woman.

Second mechanism: When groups of like-minded individuals share and discuss their opinions, they tend to become both more homogenous and more extreme in those opinions. This is known as the group polarization effect, and is one of the most robust findings in social psychology.

When I started taking about gun rights with groups of mostly-liberal university students (the majority of whom had never held a gun), we all grew more confident that interpretations of the Second Amendment have been bastardized, leading to the rise in mass shootings. Meanwhile, when Becca did the same with groups of mostly-conservative friends (many of whom owned guns), she grew more confident that the right to bear arms was central to American identity—and that since we’ve always had guns, the rise in mass shootings has other causes.

These first two mechanisms — persuasion and group polarization — are what gets polarization started: simply by putting me and Becca in different (liberal vs. conservative) social environments, our opinions began to be pulled apart.

Once our opinions had already been pulled slightly further apart by our new environments, a new set of mechanisms kicked in: our opposing beliefs started to ratchet up on their own.

Much of this phenomenon goes under the rather disunified label of “confirmation bias”: people’s tendency to gather and interpret evidence in a way that confirms their prior or favored beliefs. Confirmation bias can be broken down into the following three mechanisms, rounding out our story of polarization.

Third mechanism: selective exposure. When given a choice, people tend to prefer to see new information that they expect to confirm their prior beliefs, rather than information they expect to disconfirm them.

Soon after we parted ways I began to consistently check The New York Times and The Washington Post to get my news. Becca, meanwhile, became more consistent in checking Fox News and National Review.

Fourth mechanism: biased assimilation of evidence. When confronted with conflicting or messy evidence, people tend to interpret it in a way that favors their prior beliefs.

When Republicans stonewalled Obama’s proposals to use government funds to boost the economy, I took this to show that Republicans tend to put party over country — but Becca took it to show that Democrats tend to resort to government over-reach.

Final mechanism: motivated reasoning, a.k.a. identity-protective cognition. People tend to gather and make use of evidence in a way that confirms the things that they want to believe, especially when the belief is tied to their identity.

When Tara Reade accused Biden of sexual assault, I was inclined to be a bit skeptical — to spend a bit longer looking at articles that questioned her credibility than at those that supported it. Yet when Christine Blasey Ford made an accusation against Brett Kavanaugh, I made no such skeptical effort. Becca, no doubt, reacted in exactly the opposite way.

These mechanisms should sound familiar — we all know that people tend to be persuaded by arguments, that their motivations tend to affect the way they reason, and so on.

This is as it should be. Polarization is a familiar fact of life — it’s always been with us. Thus any adequate explanation of it will be built upon other familiar facts of life; an explanation built solely upon new or surprising findings would be missing the bigger picture.

Nevertheless, there is something new in our polarized politics — and there is something surprising lying behind these familiar mechanisms.

What’s new is that these mechanisms have become collectively aligned and individually kicked into overdrive.

And what’s surprising is that all of them — including howlers like biased assimilation and motivated reasoning — are to be expected from rational people who care about the truth but face systematically ambiguous evidence.

What Has Changed?

What has led to recent the increases in American polarization? The story, in outline, is that a variety of societal changes have led to increased social and informational sorting.

Both the Southern realignment and the civil rights movement started the process of making Democrats the party of consistent progressives and the Republicans the party of consistent conservatives. In turn, this increase in ideological consistency may have combined with the fading influence of religion to make political party the new key to many people’s identity.

Meanwhile, an increasing urban-rural divide has made it so that the political views of one’s (future) friends has become more predictable than ever. Combined with a precipitous fall in civic engagement, this has led to a decrease in cross-party social pollination and fewer friendships across party lines.

At the same time, an increasingly fragmented media landscape, along with the rise of web personalization has allowed people greater freedom in choosing their sources of information and opinion.

In short, decades ago, our social circles were ideologically diverse, our news sources constantly confronted us with differing opinions, and our political beliefs were not terribly consistent or central to our identities. Today, all that has changed. As a result, the effects of persuasion, group polarization, selective exposure, biased assimilation, and motivated reasoning all point in increasingly the same direction — pulling Democrats to the left, and Republicans to the right.

In my case, the more time I spent talking with Democrats, the more persuaded I was of their arguments and the more opinionated we all became. The more informational choices I had, the more inclined I was to listen to and trust liberal sources. The more confident I became, the more inclined I was to interpret ambiguous stories about Republican ideas and politicians in negative ways. The more I came to identify with being a Democrat, the more motivated I was to see new evidence as confirming my Democratic beliefs. And the stronger each of these processes became, the more it reinforced the others.

Similarly for Becca — and for Americans everywhere.

What does this story — of old polarizing mechanisms, recently kicked into overdrive — mean for the rationality of politics?

It means that we if understand the old mechanisms, we’ll understand both why we’ve always been polarized, and the route through which polarization has increased.

And it means that if we come to see these old mechanisms as rational—as I’ve argued we should—then we’ll be able to see our polarized politics as the result of reasonable people who care about the truth but who are pulled apart by ambiguous, hard-to-interpret evidence.

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