In the locker room today a stranger next to me asked me if I could change a £20 note. I apologised and said there was a change machine a few yards away behind the door. He quickly motioned to the open locker next to mine and asked if I could watch his things, and ran off to the machine.

I had been in this guy’s presence approximately 15 seconds and said all of 3 words to him, so why did he trust that I – as opposed to anyone else around – might not be a thief?

It happens all the time. In cafes, trains, bus stations…when you’re caught out unexpectedly on your own, something tells you leaving your stuff unattended isn’t a good idea, so you ask your fellow travellers/coffee drinkers to watch your things. But just because a stranger is next to you, can you trust them more? Out of all the learned library-goers in the locker room this morning, the probability of one us being a thief was just as high for me as anyone else.

A cursory glance at internet forums reveals a variety of responses ranging from ‘it’s a great way of hitting on a girl’ to ‘why should I put myself out having to watch your stuff?’ But I suspect most of us just say yes.

I guess if something goes missing, you know it was the stranger you asked, or they’d have told you the story of the other thief. But that’d be no good if I’ve already legged it with your stuff while you were away. In a busy place where people are static, such as train carriage or café it may even be so everyone around knows the stuff on that chair/table doesn’t belong to the person next to it, so that we all have a citizen duty to realise if it does start moving with another stranger.

So perhaps there’s method in the madness? Or perhaps it’s just a bizarre thing we all do without really knowing why we do it? If any psychologists out there can give me a more concrete answer, please let me know!