Motivation-process that influences the direction, persistence, and vigour of goal -directed behavior. Instinct-inherited predisposition to behave in a specific and predictable way when exposed to a particular stimulus. Psychological motives have evolutionary underpinnings that are expressed through the actions of genes. Adaptive significance of behavior is a key to understanding motivation. Homeostasis- state of internal physiological equilibrium that the body strives to maintain. Maintaining homeostasis requires a sensory mechanism for detecting changes in the internal environment, a response system that can restore equilibrium , and a control centre that receives information from the sensors and activates the response system. Drive theory of motivation, physiological disruptions to homeostasis produce drives, states of internal tension that motivate an organism to behave in ways that reduce tension. Incentives represent environmental stimuli that pull and organism toward a goal. Al reinforcement involves some kind of biological drive reduction food is incentive because it reduces drive of hunger.