The period solidified a neurobehavioral view of infant sensorimotor development, integrating autonomic regulation, perceptual-motor coordination, and early cognitive processes within evolving neural organization. Researchers emphasized multimodal measurement—heart-rate dynamics, EEG/evoked responses, and detailed motor observation—to reveal how sleep-wake states and sensory input modulate motor emergence and responsiveness across infants. Theoretical and methodological work highlighted staged action, organization of skilled behavior, and the centrality of environmental context for interpreting motor development, shaping cross-cultural and replication-oriented research. Historical Significance: The era delivered foundational insights into neural specialization and perception-action coupling as drivers of early development. Demonstrations of language-related left-hemisphere bias, synchrony between infant movements and adult speech, and cross-cultural acceleration of motor milestones underscored the plasticity of the developing system and the critical role of environment. Collectively, these contributions established enduring concepts of lateralization, intentional action planning, and ecological validity that guided subsequent cognitive-neuroscience and developmental-practice research.