Researcher Keith Payne has found something surprising: When people flying coach are forced to walk past the pampered first-class flyers in the front of the plane, the likelihood of some sort of air rage incident rises sharply.

In his 2017 book The Broken Ladder, Payne, a social psychologist at the University of North Carolina, argues that humans are hardwired to notice relative differences. When we’re reminded that we’re poorer or less powerful than others, we become less healthy, more angry, and more politically polarized.

I reached out to Payne because his argument seems to lead to a counterintuitive conclusion: American society would be more be more stable if we had more poverty and less inequality. I reached out to him to see if that’s what he’s come to believe after writing his book.

A lightly edited transcript of our conversation follows.

Sean Illing

Tell me what you think we least understand about the social costs of inequality.

Keith Payne

One big misunderstanding is that when people start talking about inequality, their minds go straight to poverty, but poverty’s only half of the equation. Inequality is about the size of the gap between the wealthy and the poor. It’s obviously important to be concerned about poverty and to alleviate the suffering that accompanies it, but that’s still only half the problem.

Sean Illing

What’s the other half of the problem?

Keith Payne

What people underappreciate is how having extreme inequality driven by the high end of wealth also causes trouble for society and for people’s well-being. Poverty is a related but separate problem. The presence of extreme inequality destabilizes a society in ways that are hard to understand but absolutely devastating.

Sean Illing

Let’s get into that. What sorts of problems spring from these wealth gaps?

Keith Payne

For starters, it produces serious health problems, and not subjective problems but objective health problems, like chronic diseases, obesity, drug and alcohol problems, and, ultimately, shorter life expectancies. You see comparatively higher rates of these health issues in countries with the most income inequality, and that’s after controlling for average income.

Sean Illing

I know what you mean when you say “controlling for average income,” but can you make that clear for people who don’t have a background in statistics?

Keith Payne

Sure, it means that if you take two people who make the same income, but one lives in a very high-inequality place and one lives in a low-inequality place, the person in the high-inequality location is more likely to deal with these chronic diseases, more likely to deal with these drug and alcohol problems, more likely to actually die sooner than the same person living in a low-inequality environment.

The high-inequality countries also have more crime, more incarceration, more school dropouts — things that we normally associate with poverty, but in wealthy developed countries, they’re actually more closely linked to inequality than to poverty rates.

Sean Illing

It seems obvious that wealthier people with more resources and better access to medical care will be healthier than poor people. But when you compare across societies, you find that the average person in a high-inequality society like America is less healthy than the average person in a low-inequality society like Sweden or Norway. How do you explain this gap?

Keith Payne

The perception of inequality around us has a couple of different effects. One is that it makes the average person feel poorer, [in] comparison to those who have more. And the second is that it raises our expectations. It raises our standards for what we think it is to be normal. Now, that all seems very subjective, but when you perceive yourself as poor compared to other people, that sets off a chain of events that translates into physical outcomes.

Sean Illing

That’s what I’m getting at: What’s the pathway from subjective perceptions of one’s relative poverty to actual physical health problems?

Keith Payne

One pathway is stress. If you perceive yourself as relatively low on the social ladder compared to others around you, it’s stressful, and the body treats that stress in the same way it treats a physical threat. So if you get the fight-or-flight response, you get immune responses that in the short term are good, but if they go on over the long term, over weeks or months, they can cause health problems.

Another pathway is that feeling lower on the status ladder compared to other people changes the way we approach decision-making in our own minds. It makes us riskier in our decisions; we focus more on the short term as opposed to the long term. So you have more people playing the lottery, taking payday loans, making questionable choices to try to get ahead economically. The long-term effects of these choices are usually bad — economically, emotionally, and physically.

Sean Illing

You also find that high-inequality societies are more polarized, more chaotic, and more dysfunctional. What accounts for this?

Keith Payne

What you find is that people who perceive themselves as having low status in a society often search for meaning in various ways, and one form that takes is believing in conspiracy theories. People disillusioned by their status in society look for various kinds of patterns around them, ways to justify their place, and that often takes irrational forms like conspiracy theories. Other times, it takes more normative forms like enhanced religious devotion.

Feeling lower status also has the effect of leading people to feel that the system is rigged against them. And so you hear a lot in the news about lower-education white voters feeling left behind as a function of the current economy and the kind of political consequences that has.

This feeling of being left behind is a real thing, but it’s not necessarily traceable to the fact that factories have gone overseas and that robots are replacing jobs. That’s clearly part of it, but the resentment is far worse when it happens in a society where people with higher educations and good social connections are getting wealthier and wealthier. It’s not hard to see how that can create political problems.

Sean Illing

Is it fair to say that economic inequality produces more political tribalism?

Keith Payne

I would call it more polarization, but you can call it political tribalism. And it happens on the left and the right. Again, people look for ways to make sense of a world that seems unfair, and often they do that by retreating into tribal identities — whether it’s political or religious or ethnic or whatever.

Sean Illing

A lot of the psychological problems you point to stem from our tendency to measure ourselves in terms of our social status. But humans have done this since we started living in groups, and certainly since the emergence of private property and individual rights. We’re just hardwired to detect relative differences. Is there something unique about what we’re seeing now?

Keith Payne

There’s nothing new about this psychological tendency to measure ourselves against others; that’s no different than it was 100 years ago or 1,000 years ago. What’s different today is the scale of the inequality around us, which is about as high as we’ve seen since we started keeping records of it.

Sean Illing

Do you think we would be healthier and happier if we had more poverty and less inequality?

Keith Payne

I think there’s a case to be made that trading off some measures of wealth, like the gross domestic product, would be worth it for the benefits that come with reduced inequality. The problem now isn’t that there’s too much wealth; it’s that nearly all of the increases are going to the wealthiest members of society.

Even if by some miracle we doubled everyone’s income tomorrow, that would only increase the inequality because when you double the income of millionaires, they get a lot richer than when you double the income of somebody making $20,000.

Usually, there isn’t a trade-off between more wealth and less inequality, because if you look across countries, the countries with lower levels of inequality actually have greater levels of social mobility. It’s easier to climb up that economic ladder if you’re in a place where inequality is on a human scale, as opposed to the astronomical levels of inequality that we see in America.

Sean Illing

A free society is going to produce unequal outcomes, and that’s fine so long as those inequalities don’t explode to epic proportions. So how do we negotiate these tensions?

Keith Payne

You put it well. That’s the trade-off we face. I don’t think there’s one optimum level; each society has to sort this out for itself. What works for Norway might not be the solution for America.

But the argument isn’t that everyone should be the same, or be equally successful. The argument is that democratic societies have got to negotiate these trade-offs and find the right balance between free markets and a progressive taxation system or a safety net that helps to even out the winners and losers in a way that preserves equality of opportunity but doesn’t allow society to become destabilized by inequalities.

I’m not a policy person, so I don’t have the answers. But we have enough data to know that this is something we ought to do if we want to keep our societies stable and healthy.