Great article written by Kim Campbell Thorton that discusses various measures that can be taken to help break the cat or dog from compulsive disorders. "Licking, chewing, spinning, tail-chasing and running after shadows or beams of light can be normal behaviors in dogs and cats, but in some cases they become repetitive and harmful. When normal behaviors become repetitive or sustained and don’t seem to make any sense, a dog or cat is often diagnosed with compulsive disorder. Common repetitive behaviors in dogs include licking to the point of causing a wound known as a lick granuloma, tail-chasing or spinning to the point of exhaustion, and chasing shadows or light rays. Cats are known to suck on wool, groom excessively or chase their tails."
http://www.msnbc.msn.com/id/27329468/