Why did Ivan Pavlov believe mental phenomena should be studied through measurable physiology?

Ivan Pavlov believed that mental phenomena could only be studied scientifically by reducing them to measurable physiological quantities. He recognized that traditional approaches to studying the mind often relied on subjective components, which he sought to avoid by emphasizing objective, physiological measures.12

By using observable biological processes—specifically salivary secretion—as a quantitative measure of an animal's "psychical" or subjective activity, Pavlov was able to transform complex mental states into simple, experimental terms. This methodological shift allowed him to formulate the laws of the conditioned reflex, providing a framework to analyze behavior and higher nervous activity through the lens of physiology rather than abstract introspection.12