How did Ivan Pavlov connect conditioned reflexes to the nervous system?

Ivan Pavlov connected conditioned reflexes to the nervous system by using salivary secretion as a quantitative, objective measure of higher nervous activity. By observing how animals responded to stimuli, he sought to explain mental phenomena through measurable physiological processes rather than subjective interpretation.12

Pavlov drew analogies between the conditioned reflex and the spinal reflex, incorporating concepts such as the excitation and inhibition of nerves. He expanded this framework to include:1

• Cortical and subcortical influences: Integrating the role of the brain in processing complex stimuli.1
• Mosaic action: Describing the functional organization of the brain.1
• Irradiation and induction: Applying these neural concepts to explain the spread and interaction of excitation and inhibition.12
• Language function: Proposing that human behavior is based on long chains of conditioned reflexes involving words, which allow for generalizations not seen in other animals.1

By reducing complex behaviors to these physiological terms, Pavlov aimed to provide a scientific basis for understanding both normal behavior and psychiatric conditions.13