Brain uses a universal evidence-accumulation system for decisions, including new abstract rules

New research shows the centro-parietal positivity (CPP) EEG signal tracks evidence accumulation not only for sensory input but also for arbitrary, newly learned categories. In a drift-diffusion framework with 38 participants, moving lines farther from a hidden boundary led to faster drift rates and steeper CPP buildup, indicating a single, adaptable brain mechanism that handles both real and abstract decisions; motor cortex activity remained constant with task difficulty, and the study notes limitations and the need to test more complex, real-world categories.