Lori Andersen, in Reader's Digest
As a professional animal trainer, I was disturbed when my own dog developed a bad habit. Every time I hung my wash out on the clothesline, she would yank it down. Drastic action was called for. I put a white kitchen towel on the line and waited. Each time she pulled it off, I scolded her. After two weeks the towel was untouched. Then I hung out a large wash and left to do some errands. When I came home, my clean clothes were scattered all over the yard. On the line was the white kitchen towel.