Nancy Folbre is professor emerita of economics at the University of Massachusetts, Amherst.

Today's Economist Perspectives from expert contributors.

“Dysfunctional” is a word often applied to the federal government shutdown. If only we had a functional understanding of the causes of dysfunction. Many explanations offered point to the effects of increased income inequality on political institutions. But increased inequality may have even more direct effects, undermining trust and driving the emotional climate toward more intense expressions of envy and scorn.

The announcement of a recent Gallup Poll was headlined “Dysfunctional Government Surpasses Economy as Top U.S. Problem.” The results are newsworthy: 33 percent of Americans cite dissatisfaction with government and elected representatives as their top concern, the highest level in a Gallup survey since the question was first asked in 1939. As Gallup notes, this is far higher than the 19 percent of Americans who label the economy their top concern.

These two domains, however, can’t be neatly separated. Economics affects both the way we govern and our perceptions of who is governing.

As an American Political Science Association Task Force on Inequality and American Democracy noted in 2004, the proportion of Americans who agreed that “the government is run by a few big interests looking out only for themselves” more than doubled from the mid-1960s to the mid-1990s, reaching more than 60 percent.

A more recent global survey conducted by CBS International found that 64 percent of Americans felt the government was run by a few big interests, compared with 5 percent who felt the same in Norway and 83 percent in Greece.

Cross-national comparisons suggest that inequality can literally undermine democratic institutions, perhaps because the very rich find them inconvenient. The political scientist Christian Houle finds that inequality is associated with an increased “probability of backsliding from democracy to dictatorship.”

Many of the causal links are obvious. Those with money to invest in campaign contributions and lobbying exercise a disproportionate influence on political outcomes. Apparently, a few super-rich individuals can supersede the influence of a business community that has more to gain from political compromise.

The reduced size and growing insecurity of the middle class weaken the political influence of a buffer group that has a stake in mediating conflict at least to the extent of averting government shutdowns.

But the explanations above are based on a “rational choice” theory of politics, in which both individuals and groups accurately perceive and consciously act on their interests. That can’t be the whole story. For one thing, evidence suggests that many people don’t clearly understand how policies affect income inequality and grossly underestimate inequality of wealth.

Furthermore, what people feel may be at least as important as what they think. The shutdown is fueled more by anger than by analysis. Its hot-tempered, intransigent mood seems entirely consistent with a new wave of social science research documenting the relevance of phenomena below the surface of the conscious mind, like loss of trust, emotional frustration and displaced aggression.

Richard Wilkinson and Kate Pickett provide a broad summary in “The Spirit Level: Why Greater Equality Makes Societies Stronger,” showing that income inequality across states within the United States, as well as across countries, is associated with a higher level of socially dysfunctional outcomes in a variety of domains, including health, education, obesity and incarceration.

They contend that increased inequality intensifies social stress, making it difficult for individuals to successfully collaborate. While they don’t insist this dynamic is biologically hard-wired, they mention evidence that primates and monkeys living in strict social hierarchies often behave more aggressively than others, attacking their inferiors and seeking to appease their superiors.

Susan Fiske provides a more closely focused perspective on the nexus between inequality and emotion in her new book “Envy Up, Scorn Down: How Status Divides Us.” She reviews research findings that powerful people “develop deficits specific to understanding others’ emotions and thoughts,” adding, “Power may allow scorn.” Envy also has a distinctive social signature that can lead to very bad behavior.

Both scorn and envy are, to some extent, built in. As Ms. Fiske puts it, we are “wired for comparative cognition,” which helps us make our way in the world. This raises such important questions: Does growing inequality intensify scorn and envy? And if so, how much more can we tolerate?

“Class envy” is often derogated as a kind of moral lapse. Maybe we should consider it, instead, an inevitably toxic result of an unhealthy social and economic environment.