In a new paper published in the Proceedings of the National Academy of Sciences (PNAS), Professors Leda Cosmides and John Tooby from the University of California, Santa Barbara, and their coauthors take an evolutionary look at the issue of income inequality and redistribution. As the authors note,

"Markets have lifted millions out of poverty, but considerable inequality remains and there is a large worldwide demand for redistribution. Although economists, philosophers, and public policy analysts debate the merits and demerits of various redistributive programs, a parallel debate has focused on voters' motives for supporting redistribution. Understanding these motives is crucial, for the performance of a policy cannot be meaningfully evaluated except in the light of intended ends."

The authors of the study argue that support for redistribution reflects motivations that evolved for the small-scale world of our hunter-gatherer ancestors. "Understanding the economic and political nitty-gritty of redistribution does not come naturally to us," said lead author Daniel Sznycer, an assistant professor of psychology at the University of Montreal. "But humans have been interacting with worse-off and better-off individuals over evolutionary time. This process built neural systems that motivate us to act effectively in situations of giving, taking, and sharing."

According to the authors, we see the modern world through the eyes of our ancestors. "Political rhetoric about redistribution involves a cast of characters," said Cosmides, such as "the poor" and "the rich." "The idea is that we view these characters through the lens of motives that evolved to regulate interactions with their ancestral counterparts—community members who are worse-off and better-off than you are."

To understand the logic behind support for—or opposition to—economic redistribution, the research team focused on three motives: compassion, self-interest and envy. They tested how strongly each of these motivations predicted support for redistribution in four societies: the United States, the United Kingdom, India, and Israel.

"Compassion is the emotion that orchestrates need-based help—help toward those worse off than oneself," Tooby explained. "Our ancestors lived in a world without social or medical insurance, and so they benefited from covering each other's shortfalls through mutual help. If your neighbor is starving and you have food, you can save his life by sharing with him. Later, when the situation is reversed and he shares his food with you, your life is saved."

Accordingly, the authors found stronger support for redistribution in people who spontaneously feel more compassion toward individuals in need. Self-interest also played a role: support for redistribution was higher in people who thought that they or their family would benefit from it personally.

The more surprising findings involved envy and fairness. Envy, directed toward those better off than you, predicted support for redistribution. "When a rival outperforms you in some activity, your relative standing decreases," said Sznycer. "People sometimes act to chip away at their rivals' advantages, even when that also harms third parties or even sometimes themselves."

Envy and the spite it generates are socially destructive, he noted, but "they can make sense in the context of an ancestral world that included competitive zero-sum games." When given two hypothetical policies—lower taxes on the rich resulting in more revenue to help the poor versus higher taxes on the rich but less money for the poor—one in six people preferred the second, more spiteful option. This willingness to hurt the poor to pull down the rich was predicted only by the individual's proneness to envy.

Fairness looms large in political rhetoric and theories of justice. But differences in subjects' taste for fairness did not predict how strongly they supported redistribution. The results were the same in the United State, the United Kingdom, India, and Israel: support for redistribution was predicted by compassion, self-interest, and envy, but not fairness.