This study investigated the impact of learner factors on complexity, accuracy, and fluency (CAF) when performing tasks with varying levels of complexity. The study measured working memory, language anxiety, and the scale and intensity of social interaction among 25 intermediate and 30 advanced Korean learners, as well as native Korean speakers. The results showed that the complexity of spoken language production increased with more complex tasks at the expense of accuracy, particularly among second-language learners. Conversely, native speakers maintained consistent accuracy across different task types. These findings underscore the importance of tailoring task design and implementation to individual learner profiles, which is essential for optimizing task-based language-learning environments. This study advocates a balanced approach that aligns task demands with learner needs to enhance educational outcomes.