A few weeks ago I was in line at the grocery store behind a lady who was buying a fair amount of groceries. Pretty typical trip to the store, except that as I watched, she was placing her items (from the cart) onto the little conveyor thing quite atypically. Rather than just lining everything up one after the other, she was placing the items here and there on the conveyor. It seemed rather random to me. Until at one point, as she was closely watching the total price go up and up, she said “ok, that’s...