Most people know not to go grocery shopping on an empty stomach. They've tried it and ended up with a cart full of smoked oysters or more junk food than a trick-or-treater on Halloween. But not everyone realizes that an empty stomach can also lead to other types of bad decisions.

Whether it was food, money or music, people were more likely to settle for a smaller reward now than a larger one they had to wait for, if they were hungry, according to a recent study. And while choosing a smaller short-term reward can sometimes be a wise choice, it tends to backfire with respect to making important life decisions.

When you're hungry, immediate gratification seems to be the order of the day and not just for food.

Researchers from the University of Dundee in the United Kingdom tested fifty young adults just after they had eaten and also after they had been fasting for ten hours. They were offered varying amounts of money, chocolate bars and music downloads, but they would always get more if they were patient enough to wait.

The largest amounts offered were $25, 10 chocolate bars or 20 song downloads.

Not surprisingly, hungry people did not patiently wait for food. They were willing to wait 35 days to receive twice as many chocolate bars if they had a full stomach. But when they were hungry, they would only wait three days on average. If they had to wait any longer, they would take fewer chocolate bars now. And who can blame them?

The same situation was seen for money and music, though the effect wasn't quite as strong. Hungry people would wait only about half as long (40 days vs. 90) to get twice as much money and only about a third as long (12 days vs. 40) to double their song downloads. Otherwise, they would choose the smaller but immediate reward.

When you're hungry, immediate gratification seems to be the order of the day and not just for food.

“We found there was a large effect, people's preferences shifted dramatically from the long to short term when hungry,” said study co-author, Benjamin Vincent, a lecturer in the Division of Psychology at the University of Dundee. “This is an aspect of human behavior which could potentially be exploited by marketers so people need to know their preferences may change when hungry.”

The authors caution that the study looked at people's reactions to hypothetical rewards, not actual ones. It's not clear how people would react if real food, money or songs were involved, along with real waiting periods. But the findings suggest that people should be cautious about making important decisions when they are hungry.

For more details, see the article in Psychonomic Bulletin and Review.