Behavioral medicine is the scientific study of everything animals do, whether the animals are insects, birds, mammals, fish, or humans. The field of animal behavior is concerned with understanding the causes, functions, development, and evolution of behavior. Behavior refers to the actions or reactions of an organism. Behavior is usually in relation to the environment, and is controlled by the endocrine and nervous systems. The complexity of animal behavior is related to the complexity of its nervous system. Generally, animals with complex nervous systems have a greater capacity to learn new responses and thus adjust their behavior.

An animal's behavior is influenced by many factors. Some of these factors include genetic predisposition, experience and learning, environment, and physiology. Several dog studies have shown that behavior can be inherited to some degree. In addition, maternal influences can affect personality and temperament. If puppies are separated from a fearful mother, the puppies are less likely to be fearful than if they are left with their mother. The effect of other puppies in the litter, the amount and type of human handling, and exposure to new objects and experiences all influence a dog's behavior. The brain and its associated neurotransmitters also play a fundamental role in temperament and behavior. Abnormal levels of various hormones play a role in certain forms of aggression and fear.

Understanding the nature of behavior problems is essential to developing a rational basis for their treatment. While this chapter focuses primarily on the abnormal behavior of dogs, the extent to which a dog's behavior is abnormal is defined by how much it deviates from “normal” or by the severity of the problem that this behavior poses to its owner.

Last full review/revision July 2011 by Karen L. Overall, MA, VMD, PhD, DACVB, ABS Certified Applied Animal Behaviorist