Stereotypic Behavior and Compulsive Disorder

When an animal persistently and repetitively engages in a single behavior that serves no apparent function, the behavior is called a stereotypy. When the stereotypic behavior persists regardless of the environment, compulsive disorder (CD) is diagnosed. CD occurs in many species and is a common diagnosis in behavior services. In human medicine, the more complete term, obsessive-compulsive disorder (OCD), is used. According to the Diagnostic and Statistical Manual of Mental Disorders, 4 edition, obsessions are “persistent ideas, thoughts, impulses, or images that are experienced as intrusive and inappropriate and that cause marked anxiety or distress.” Thus, by definition, obsessions take place within the psyche and cannot be directly measured by an external observer. Compulsions are “repetitive behaviors or mental acts, the goal of which is to prevent or reduce anxiety or distress, not to provide pleasure or gratification.” While repetitive mental acts cannot be observed in animals, repetitive behaviors can. Thus the more limited term CD is typically used for animals. Not all repetitive behaviors are CD. For example, a captive wild animal confined to a small cage may pace back and forth. This behavior probably derives from multiple motivations, including attempts to escape and attempts to engage in physical activity at levels that would be normal for the animal in the wild. As the animal paces back and forth, the behavior can be identified as stereotypic. If the animal is then turned loose in its natural habitat or in a large, appropriate, complex enclosure and begins to engage in behaviors that are normal for its species, it does not have CD. If, on the other hand, after release into a large, complex enclosure, the animal goes to a corner, begins pacing back and forth, and spends large amounts of time repeating this behavior over the following days, CD can be diagnosed. The repetitive behavior is now being caused by a pathologic development in the central nervous system and is unrelated to environmental conditions.