The terms System 1 (see “System 1”) and System 2 were popularized by the work of Daniel Kahneman in his book, Thinking Fast and Slow (2011). System 2 refers to the conscious processing of a stimulus or experience. Conscious processing can involve logical reasoning and rationalization that require more cognitive effort and attention, in order to come to a decision. Hence, it tends to be a slower response than System 1. Typically, System 1 and System 2 are working in parallel. The System 1/ System 2 paradigm is a conceptual framework and does not represent specific regions of the brain specialized for System 1 or System 2 processing.