Feed me! Love me! Return my lost wallet!: Wallets containing pictures of babies were more likely to be returned.Courtesy Alex Motrenko

They inspire people to return missing wallets. Scientists in Scotland deliberately placed wallets on the streets in Edinburgh to to see how many would be returned. Most of the wallets contained a photo—a baby, a puppy, a family portrait, or a photo of an elderly couple. Some wallets had no photos, but a charity receipt. And still others had nothing beyond name and address. None of the wallets contained any money.

In all, 42& of the wallets were returned. Those with baby pictures came back most often, 88% of the time. The puppy dog picture triggered an honest response in 53% of the finders; the family photo 48%; and the elderly couple photo only 28%. (I take this as evidence that Scots don't like old people.) Bringing up the rear were the wallets with the charity receipt (20%) and the ones with nothing special at all (15%).

Professor Richard Wiseman, the psychologist who ran the experiment, said the results demonstrate that humans are hard-wired with an instinct for compassion and want to protect vulnerable infants. This no doubt inspires us to protect future generations, but it's a raw deal if you ain't cute.