What observations about dogs’ salivation first interested Ivan Pavlov?

Ivan Pavlov’s initial interest in dogs’ salivation arose during his research on the digestive system. While studying salivary secretion, he observed that dogs salivated not only when food was placed in their mouths but also in response to the sight or smell of food, and even at the sight or sound of the technician who typically provided it.1

Initially, Pavlov viewed these responses—which he termed "psychic secretions"—as an interference with his planned experiments on digestive glands. However, he soon recognized that these observations provided a valuable, objective tool for studying how animals learn, leading him to shift his focus toward the systematic study of conditioning and the development of the conditioned reflex.1