During this period, research converged on the role of learner attitudes and motivation as central determinants of engagement, persistence, and achievement in second language learning across ages, while debates about aptitude and beliefs highlighted individual differences. A cognitive-psycholinguistic lens integrated language development with general cognitive mechanisms, transfer between first and second language, and developmental constraints, aligning psycholinguistic findings with classroom practice. Methodologically, researchers emphasized rigorous measurement, test design, error analysis, and reading assessment to trace proficiency trajectories, and cross-language relations framed SLA as a continuum linking L1 acquisition with L2 development, guiding pedagogy and theory. Historical Significance: This era produced foundational works that shaped subsequent SLA research. Attitudes and Motivation in Second-Language Learning (1972) established integrative motivation and affective factors as core determinants and influenced classroom practice and motivation research for decades. Other works—Natural Sequences in Child Second Language Acquisition (1974) demonstrated orderly morpheme and syntax development in child SLA, anchoring the natural-order hypothesis and informing input-oriented theories; Is There a Natural Sequence in Adult Second Language Learning? (1974) questioned universal sequences across ages, prompting critical reexaminations of development patterns; From communication to language—a psychological perspective (1974) helped shift the focus from grammar to meaningful communicative use, bridging psycholinguistics and pedagogy and laying groundwork for communicative language teaching. Together these contributions consolidated an integrative paradigm that persisted and evolved in later cognitive-psycholinguistic and cross-language SLA research.