Eye-Tracking and Biometric Feedback in UX Research: Measuring User Engagement and Cognitive Load

User experience research often uses surveys and interviews, which may miss subconscious user interactions. This study explores eye-tracking and biometric feedback as tools to assess user engagement and cognitive load in digital interfaces. These methods measure gaze behavior and bodily responses, providing an objective complement to qualitative insights. Using empirical evidence, practical applications, and advancements from 2023-2025, we present experimental data, describe our methodology, and place our work within foundational and recent literature. We address challenges like data interpretation, ethical issues, and technological integration. These tools are key for advancing UX design in complex digital environments.