Our local Waitrose has a self-scanning system (in fact, has done for years), so you have your own barcode reader and as you go around the shop you pick up the things you want, scan them yourself and then put them in your shopping bag. It's a good system, and it save time and queues because when you have finished shopping you just put your chip and PIN card in to pay and then go. Since your shopping is already in shopping bags, you're off.
Occasionally, the computer will ask an assistant to take a couple of random things out of your shopping bag and scan them to check that you're scanned them in properly. This doesn't happen that often, maybe once a year or something, so it's no inconvenience. Today, though, when I went to check out, the computer called for a "rescan". This was tedious, because it meant that I had to take everything out of my shopping bags and have the assistant re-scan all of them, It's presumably a random anti-fraud check.
What stress! As far as I knew I'd scanned everything properly. But as I stood there waiting for the assistant to finish, I began to panic. What if there was something in the bad that I hadn't scanned. What if I'd forgotten something? What if my impending senility had led me to completely forget to scan something? I would be forever branded a criminal by the John Lewis supercomputer and I would never be able to hold my head up in middle-class Britain again.
Why does this happen? What is it in our brains that triggers the sensations of guilt in these circumstances?
Everything in the bag had been scanned correctly, of course, since it's second nature now. But when I left, I definitely had an increased heart rate and sweaty palms.