Animal behavior is generally divided into two categories: (instinctual) and learned (acquired through experience). Key areas of study include:

: Critical windows in early development—such as 3 to 14 weeks in puppies—where exposure to novel stimuli determines future sociability and fear responses.

: Studying animal behavior to better understand human psychology and evolution.

Veterinary science uses behavioral cues as diagnostic tools to treat patients who cannot speak.

In modern veterinary science, aggression is recognized as a clinical sign, not a diagnosis. The veterinarian suspects a medical cause. After an exam, they discover Max has a fractured carnassial tooth. The pain from that tooth, exacerbated by the vibration of a child yelling or moving quickly, triggered a defensive bite. Antibiotics and an extraction; the aggression vanishes.