Behavioral biometrics which continuously authenticates users by analyzing how they type, swipe, walk, speak, or move a mouse, patterns that arise from deep neural and motor processes and are nearly impossible to fake, detailing the major modalities of keystroke dynamics, mouse movement, gait recognition, touchscreen gestures, and voice biometrics, exploring their mechanisms, uses, tools, and constraints. It connects these behaviors to neuroscience, showing how the motor cortex, basal ganglia, cerebellum, and prefrontal regions generate habits and muscle memory, ensuring stable and unique patterns over time. To address the issue of mental surveillance, the chapter proposes frameworks for layered consent, neuro-rights, and transparent AI governance to protect cognitive liberty.