What do people do when they find a wallet on the street? Leave it? Take it to a police station? Post it back to the owner? Keep it, even? The answer, scientists have found, depends rather more on evolution than morality.
Hundreds of wallets were planted on the streets of Edinburgh by psychologists last year. One of four photographs was inserted behind a clear plastic window in each of the wallets, showing either a smiling baby, a cute puppy, a happy family or a contented elderly couple. Some wallets had no image and some had charity papers inside.
When faced with the photograph of the baby people were far more likely to send the wallet back, the study found. The baby photograph wallets had the highest return rate, with 88 percent being sent back. Next came the puppy, the family and the elderly couple, with 53, 48 and 28 percent respectively. At 20 and 15 percent, the charity card and control wallets had the lowest return rates.
Scientists argue that it would be difficult to genetically code for feeling empathy exclusively towards your own child, and much easier to code for feeling empathy towards all children.