Modern AI systems excel in both intuitive pattern recognition (System 1) and analytical reasoning (System 2), yet lack the sophisticated metacognitive mechanisms that humans employ to regulate these processes. We introduce System 1.5, a theoretical framework implementing metacognitive regulation in artificial systems that monitors cognitive processes, generates responses, and evaluates outcomes to determine when to rely on intuition versus analysis. Our key contributions include a theoretical foundation bridging cognitive science and AI, a formal framework for metacognitive regulation, and insights into coordinating different processing modes in expert decision-making.