The brain deals with rationality-related processes in multi-dimensional and diverse ways. It is supposed that the brain starts processing such complicated complex cognitive processes immediately after the stimulus appears. Components in event-related potentials can reflect those processes that are underlying them. For example, mismatch negativity (MMN) reflects the violation of a rule established by a sequence of sensory stimuli. N2 components are supposed to be related to cognitive control. P300 components are elicited when stimulus detection engages memory operations. N400 is related to meaning processing. P600 is associated with syntactic and semantic reanalysis processes. Early left anterior negativity (ELAN) is supposed to be a marker of syntactic first-pass parsing. Error-related negativity (ERN) is a negative waveform that arises after a participant makes a detectable error. These components can reflect various rationality-related processes in decision making. In dual process theory, there are two distinctive types of processes: fast and intuitive process, that is System 1 (Type 1), and deliberative and reflective process, that is System 2 (Type 2). It is supposed that the two processes deal with rationality based on their respective characteristics. However, the detailed processes are not clear. For an analysis using ERP components, it is expected that the rational-related processes in the course of time reveal up to about 1000ms.
