LOS ANGELES - If you found a lost wallet on the ground with money inside, how likely would you be to return it to its rightful owner?
In a global study, researchers planted more than 17,000 "lost wallets" across 355 cities in 40 countries and kept track of how often somebody contacted the supposed owners. The unexpected conclusion was that people are more likely to return a lost wallet if it contains money.
And the more cash, the better.
The presence of money -- the equivalent of about $13 U.S. dollars -- improved this response rate to about 51 percent, versus 40 percent for wallets with no cash.
That trend showed up in almost every country where the study was conducted, although the actual numbers varied.
Researchers increased the amount of money in the U.S., the United Kingdom and Poland. The response jumped to 72 percent for wallets containing the equivalent of about $94, versus 61 percent for those containing $13.
If no money was enclosed, only 46 percent attempted to contact the wallet's "owner."
"The evidence suggests that people tend to care about the welfare of others, and they have an aversion to seeing themselves as a thief," said Alain Cohn of the University of Michigan, one of the authors who reported the results Thursday in the journal Science.
The wallets in the study were transparent business card cases, chosen so that people could see money inside without opening them. A team of 13 research assistants posed as people who had just found the wallets and turned them in at banks, theaters, museums or other cultural establishments, post offices, hotels and police stations or other public offices.
After walking into the building, the research assistant approached an employee at the counter and said, "Hi, I found this (wallet) on the street around the corner. Somebody must have lost it. I'm in a hurry and have to go. Can you please take care of it?"
The key question was whether the employee receiving each "lost wallet" would contact its supposed owner, whose name and email address were displayed on three identical business cards within.
The business cards were crafted to make the supposed owner appear to be a local person, as was a grocery list that was also enclosed.
Some wallets also contained a key, and they were more likely to get a response than the ones without a key. This led researchers to conclude that concern for others was playing a role, since -- unlike money -- a key is uniquely valuable to its owner.
The study found that in 38 out of the 40 countries, citizens were "overwhelmingly" more likely to report lost wallets with money in them than without -- with Mexico and Peru being the exceptions.
Nations varied widely in how often the wallet's "owner" was contacted. In Switzerland the rate was 74 percent for wallets without money and 79 percent with it, while in China the rates were 7 percent and 22 percent.
The U.S. figures were 39 percent without and 57 percent with money.
The study measured how employees act when presented with a wallet at their workplaces, but the authors said it was unclear whether those same people would act differently if they found a wallet on a sidewalk.
Robert Feldman, psychology professor at the University of Massachusetts Amherst who didn't participate in the work, said he suspected the experiment might have turned out differently if it involved "everyday people" rather than employees acting in an official capacity.
But Feldman called the study impressive and said it seems like "a very real result."
Dan Ariely, a psychology professor at Duke University who didn't participate in the research, said the conclusions fit with research that indicates keeping a larger amount of money would be harder for a person to rationalize.
"It very much fits with the way social scientists think about dishonesty," he said.
The Associated Press contributed to this report.