Edinburgh psych researcher Richard Wiseman and team left a load of wallets lying around with various contents, trying to see if there was a correlation between, say, baby pictures or cards indicating charitable giving and the rate at which wallets are returned. It turns out that people in Edinburgh (and maybe everyone) have a high likelihood of returning wallets with baby pictures, but are much less likely to return the wallets of charitable givers:



The baby photograph wallets had the highest return rate, with 88 per cent of the 40 being sent back. Next came the puppy, the family and the elderly couple, with 53 per cent, 48 and 28 respectively. At 20 per cent and 15, the charity card and control wallets had the lowest return rates.

Overall, 42 per cent of the wallets were posted back — more than the team had anticipated. "We were amazed by the high percentage of wallets that came back," said Dr Wiseman.

Scientists have also found evidence for a baby instinct in brain scanning experiments. A recent study at the University of Oxford examined how people responded when they were shown photographs of baby or adult faces.