I found this article published on TimesOnline about some Psychologists who placed 240 wallets around Edinburgh with pictures of different things in them amazingly recovered nearly half of them.
Here’s the gist:
Put a baby picture in your wallet and your quite likely to get your wallet back (88 per cent of the 40 were returned [9 out of 10]). Without a picture only (15 per cent were returned [1 out of 7]).
Why this works:
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. If you find a baby alone, there is a good chance it belongs to you, making it an effective evolutionary trait, said Dr Wiseman.
There are a lot of other tidbits in there since they also put pictures of dogs, old people and charity receipt slips and such in the wallets, and it explains how they were scattered to make a good test. Definately hit it up if your interested.
I for one am going to start carrying a baby picture of myself or the wife.