Compulsive behaviors in dogs that have a neurological or mental illness component often go beyond simple stress-related habits and reflect deeper disruptions in brain function or neurochemistry. These behaviors, such as obsessive light or shadow chasing, fixation on reflections or moving objects, tail spinning, or relentless licking, can resemble obsessive-compulsive disorder (OCD) in humans. They may stem from abnormalities in neurotransmitters like serotonin or dopamine, which regulate mood an