An automatic aider of human cognitive functions for the operation of computerized displays. The invention estimates in real-time the mental decision made in response to a displayed stimulus from the single-even, transient, evoked cerebral potential and the corresponding visual response. The invention attains high accuracy levels of decision classification by combining a unique parametric model of the cerebral potential with advanced techniques drawn from numerical analysis, artificial intelligence, and nonlinear regression analysis. The invention uses an expert system to determine the decision aiding to be provided to the human operator from the disparities among the estimations and the decisions that are expected from task scripts for the displayed stimulus.