An empty stomach can lead to an empty wallet

"Hunger makes us think about seeking, acquiring, and consuming food," says Alison Jing Xu, assistant professor of marketing at the Carlson School. "The acquisition-related thoughts can spill over and put us in a mode of also getting nonfood items even though they are incapable of satisfying our hunger."

In one of five studies conducted by Xu and colleagues, participants were asked to refrain from eating for at least four hours. Prior to a survey designed to measure their attitudes toward a common office supply, one group's hunger was eliminated through a blind taste test of cakes. The other group proceeded directly to the survey on binder clips. The researchers provided participants in both groups the opportunity to request as many samples of the clips as they liked. Hungry participants opted for 70 percent more products than their satiated counterparts.

Hungry Mall Shoppers Spent 64% More Money

Another study in the paper examined the relationship between actual purchases at a mall and the shopper's degree of hunger. After shopping at a large department store, consumers were surveyed and their purchases were analyzed. Controlling for the influence how much time they spent shopping, the hungrier shoppers were found to have spent 64% more money than those who were less hungry.

"If you go for a shopping trip with an empty stomach you may spend more money and buy more stuff than you otherwise would," said Xu. "Why not feed yourself before a shopping trip? Alternately, if you are hungry and you have to make purchasing decisions, think twice before you buy. "

The research, co-authored by Norbert Schwarz (USC's Marshall School of Business) and Robert S. Wyer, Jr, (the Chinese University of Hong Kong) appears in the current issue of the journal Proceedings of the National Academy of Sciences.