I'm at our New York office this week and I’ve been struck by what I see in the local stores. The corner convenience store has at least three photos of Barack Obama with the “Yes We Can” campaign slogan - quite an uplifting thought when you've just popped out for some gum. I can't remember ever seeing a picture of a UK politician in one of my local shops.

I found a less uplifting message on a number of the tills. It said: “If I do not give you a receipt for your purchase, please let my manager know and receive a $5.00 credit for your next purchase”. I asked a couple of assistants how they felt about the sign. They replied: “We’re used to it – the boss doesn’t trust anybody at all.”

I asked them if the manager gives many people five dollars off their next purchase and got the same response from two different stores and three members of staff: “Well, if you were going to think of doing this you would just make sure you gave the stuff away to your friends – not to people you don’t know.” I wonder if any of the store managers have realised that their system is not working! Stick people in a low-trust environment and, trust me, they will live up to your low expectations.