How did Ivan Pavlov explain the role of language in human thought?

Ivan Pavlov explained the role of language in human thought by characterizing it as a system based on long chains of conditioned reflexes involving words.1

Beginning around 1930, Pavlov posited that language functions as a unique human capability that extends beyond simple communication. He argued that language allows for the elaboration of generalizations—a cognitive process he believed was not possible in animals lower than humans. By integrating these verbal conditioned reflexes, humans are able to move beyond the immediate, stimulus-driven responses observed in other species, facilitating a more complex level of higher nervous activity.1