My son is an avid reader and often when he was small we'd go into the local bookshop for him to buy more books. While he was choosing I browsed through a number of books and eventually my son joined me. I was still removing, glancing through and replacing the books and my son, having made his selection was anxious to go. In a loud voice he eventually said "Dad, are you going to pay for the book this time?" I knew what he meant, was I going to buy the book I was holding, but everybody turned and gave me a very dirty look. It was a long time before I returned to that shop again.