This course explores the biological and environmental foundations of human language development, focusing on how children acquire the phonological, morphological, syntactic, and semantic systems of their first language (L1). It critically examines major theoretical frameworks and evaluates the evidence supporting them. The course also addresses individual differences, the role of input and interaction, and the continuity between early child language and adult competence. Students will learn to analyze child language data using standard metrics and interpret experimental findings in developmental psycholinguistics.