Rational economics doesn’t always govern how we make decisions about our money in the real world. As part of our series Brain Drain with Marketplace’s Wealth and Poverty desk, we’re exploring the ways in which our minds are rigged to cost us money.

The sixth topic of our series: how wealth influence social behavior.

Wealthier people are more likely to cheat to win a prize, or lie during negotiations. Poorer people are more helpful, generous and trusting of others. Paul Piff, a social psychologist at the University of California Irvine, has conducted dozens of studies about how economic class influences behavior and personality. Now, he’s piloting a new study looking at how college students respond to inequality.

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