When I'm grocery shopping something very strange always happens. I'll be wandering up the aisle with my trolley, looking up at the shelves and deciding what to buy. Then suddenly I'll hear a voice behind me saying 'Sorry'. I'll turn around and someone would be standing behind me. We hadn't touched, nor had our trolleys touched, but for some reason they had apologised for standing behind me. I never understood why, but people in supermarkets always say "Sorry" as they walk past me or stand near me. Has anyone else had this, does anyone do this, and can anyone tell me why?