It’s cliché to say “disagreement doesn’t have to be disagreeable.” There are, however, good reasons that we must be frequently reminded of this advice. We all know from experience that disagreement is often unpleasant and can even lead to hard feelings.

College has traditionally been celebrated as a place where disagreement and debate are not just tolerated but explicitly valued. Inside and outside the classroom, exploring unconventional and contrarian views has long been thought to be a fundamental part of the college experience.

But many people fear that even on college campuses — or perhaps especially on college campuses — the art of constructive disagreement has been lost, and dissenters from mainstream views are too prone to being demonized. These fears are, of course, Heterodox Academy’s raison d’être.

So, why does disagreement so often cause interpersonal animosity? Why might people overly demonize those whom we disagree with, and what does “overly” even mean in this context exactly? How could we possibly scientifically demonstrate this mistake, and what would cause it?

My new book, Undue Hate: A Behavioral Economic Analysis of Hostile Polarization in US Politics and Beyond, tries to tackle these questions. (There’s an open-access version here.) The book focuses on American partisan politics, which has of course become all too disagreeable over the past several decades. Hostility between the parties, aka affective polarization, has grown much more than disagreement over policy or ideological opinions.

I argue that Republicans and Democrats do indeed dislike each other more than they should, and that this mistake has grown over time. I don’t draw these conclusions based on judgments about why people in either party should like or dislike one another. Instead, I explain how subjective interpersonal feelings can be objectively wrong.

This might sound paradoxical, but it’s a simple point that is clearly true upon brief reflection: We can objectively misjudge other people by our own subjective standards. Since these judgments drive the warmth or coldness of our feelings, these feelings can be mistaken: too warm or too cool. For example, if I like people who give 10% of their income to charity and think you give only 5%, but you actually do give 10%, I’ll like you less than I should — by my own (subjective) standards.

A variety of types of empirical evidence imply that Americans in fact do have overly negative misperceptions about the other side: We think they are more extreme, more hostile toward us, more supportive of violence, and more self-serving than they really are. As a result, our feelings toward the other side are too cold. What’s more, people who dislike their political opponents the most tend to have the most distorted perceptions — further supporting the hypothesis that animus is based at least partly on false beliefs.

After the book defines undue dislike and presents evidence of it, I next discuss reasons for this mistake. First and perhaps foremost, this is due to our overconfidence in our beliefs (our overprecision) and our overconfidence in the universality of our personal preferences (our naive realism). Overprecision makes us overconfident that every time we’re challenged, whoever is doing the challenging is wrong. And we don’t like people who are wrong: We think their wrongness is a signal of incompetence, closed-mindedness, and bias, and perhaps even bad motives. Our overconfidence in these bad traits in others yields undue dislike toward them.

Naive realism can cause false consensus, or overconfidence that others share our beliefs and tastes. Jonathan Haidt’s The Righteous Mind famously compares moral values to taste buds, arguing that differences between the morals of Republicans and Democrats are akin to differences in tastes for food: Typically when we disagree, we are just different, and no one is right or wrong. But he doesn’t explain why these differences lead to hostility, much less undue hostility.

Ironically, false consensus — again, that’s overconfidence in the similarities of our tastes and beliefs — can help explain why differences in tastes, like those discussed by Haidt, can cause undue dislike. That’s because if I think you really know that my preference on the matter at hand is best — “come on, we all know what I’m saying is true” — when I hear you argue for a different opinion, I’ll think you’re being disingenuous. You’re arguing in bad faith. You must have a hidden motive for your argument, and we tend to dislike people with hidden, ulterior motives.

Another reason for undue dislike is alluded to by the old saying, “Don’t hate the player, hate the game.” Our actions that are coherent, given the incentives and strategic factors we face, often appear morally worse when observers don’t fully understand these incentives. The behavioral economics literature on limited strategic thinking shows how people indeed underestimate how strategic forces drive other people’s decisions.

An additional reason for undue dislike is captured by another adage, this time one popularized by Alcoholics Anonymous: “What’s hysterical is historical.” Our feelings today are based on a long history of interactions and tit-for-tat-esque dynamics. Motivated, self-serving memories and perceptions cause misunderstandings to compound over time.

The last and not least cause of undue dislike is the skew in the information we observe about the other side, in conjunction with the psychology of how we interpret this information. The prevalence of echo chambers online is debated. But most of us are in echo chambers to some degree — more than we realize — especially offline, where our friends, neighbors, and family are almost entirely like-minded politically. When we do interact with the other side online, we often see them at their worst. This is what sociologist Chris Bail calls the social media prism. We were not born yesterday, but we still err toward credulity, especially when we encounter information we hope is true. This includes negative information about the political opposition because this supports our side’s relative superiority. When we do have contact with the other side, we tend to understand them better — and like them better.

In the final chapter I discuss solutions. There are no easy fixes, but I argue we should have more of an all-hands-on-deck mentality — especially our leaders in politics and media, even if this seems to not be in their personal best interests. (One specific idea is a website project I’ve worked on that has shown promise. I’m happy to discuss this with anyone interested in using this!)

Regardless, we can all make the world a slightly better place by better understanding, and resisting, undue hate in our own lives — and helping others to better understand this as well.