To develop a unified theory of human decision-making in daily behavior selections, the authors propose an architecture model called Model Human Processor with Real Time constraints (MHP/RT) (Kitajima & Toyota, 2012). This model inte- grates the established theory of decision-making by Kahneman (2003), Two Minds, and the idea that human behavior is orga- nized in the ever-changing environment (Newell, 1990) into a construct that is capable of simulating such daily behavior as driving a car or watching a baseball game at a stadium. Kitajima and Toyota (2012) proposed that MHP/RT operates in one of four modes that are defined by the active components of MHP/RT at a specific time. Kitajima and Toyota (2011a) demonstrated that at a specific moment MHP/RT is processing one of four aspects of a certain event. This paper demonstrates how memory is used in the four operation modes and the four processing modes of MHP/RT.