During this period, researchers pursued systematic observation of infant vocal development and early screening of reading, writing, and speech difficulties, linking language growth to educational outcomes. The work integrated language development with emergent cognitive processes, highlighting how language supports planning, problem solving, and listening comprehension. Methodologically, the approach combined structured observation with experimental tasks to trace language trajectories and cognitive relations. Historical Significance: This era established foundation for modern psycholinguistics and cognitive-developmental theories of language, showing language as both a product and driver of thinking. By pinpointing staging in speech production and demonstrating language’s role in cognitive tasks, it influenced therapy, screening, and remediation strategies. The period’s breakthroughs unified language development with cognitive processing research, guiding future research on learning, processing efficiency, and language-based disorders.