A purely medical approach might find nothing wrong and prescribe an anti-anxiety medication. A purely behavioral approach might diagnose separation anxiety and suggest training. The does both simultaneously.
The stethoscope can listen to the heart and lungs, but it cannot hear the subtle yelp of a dog with a painful tooth. The ultrasound can see the kidneys, but it cannot visualize the terror in a cat’s eyes. It is the language that animals use to describe their pain, their fear, and their sickness.