Libby has developed in the last couple of weeks this odd obsessive-compulsive behavior with chasing shadows. She can't seem to concentrate on anything else if she sees a shadow of something. This happens inside and outside. We can be in the middle of playing fetch and she'll see my shadow move, drop the ball and try to attack my shadow. Sometimes she'll dig at the grass a bit, like she's trying to grab it. She does the same thing in the house, diving at the shadow and then biting at the floor or scratching at it. Has anyone had a dog that did this? Or any experience breaking an obsessive behavior?