The document reviews the evolution of theories in second language learning from the 1940s to the 2000s, highlighting key movements such as behaviorism, cognitive psychology, and constructivism. It discusses the limitations of early theories that focused solely on observable behaviors and linguistic structures while emphasizing the role of more modern approaches that consider meaning, social interaction, and the learner's active role. Ultimately, it concludes that no single theory is wholly correct, and all contribute valuable insights to understanding language learning.