This study explores whether reliance on generative AI leads to cognitive erosion (decline in mental effort) or cognitive extension (enhancement through support). Participants (N = 200) completed problem-solving tasks either independently or with AI assistance. Cognitive load, self-efficacy, and critical thinking were measured before and after. Results showed improved task performance with AI, but decreased metacognitive awareness and engagement. These findings suggest that frequent AI use may undermine independent thinking. The study offers early insights into how AI influences cognition, with implications for education, mental performance, and policy development in an increasingly AI-dependent world.