Midterm notes chapter 13 motivation and emotion. Motivation: general term for a group of phenomena that affect the nature of strength, and persistence of an individual"s behaviour. This chapter focuses on eating, sexual behaviour and aggression as these are important to survival of individual and species. Complex organisms possess physiological mechanisms that detect deficits or imbalances associated with these needs and related regulatory behaviours: behaviour that tends to bring physiological conditions back to normal, thus restoring the condition of homeostasis. Homeostasis: process by which important physiological characteristics are regulated so that they remain at their optimum level. System variable: variable controlled by a regulatory mechanism for example temperature in a heating system. Set point: optimum value of the system variable in a regulatory mechanism. Detector: in a regulatory process, a mechanism that signals when the system variable deviates from its set point. Correctional mechanism: the mechanism that is capable of restoring the system variable to the set point.