<P> Two neurobiological models of emotion in the prefrontal cortex made opposing predictions . The Valence Model predicted that anger, a negative emotion, would activate the right prefrontal cortex . The Direction Model predicted that anger, an approach emotion, would activate the left prefrontal cortex . The second model was supported . </P> <P> This still left open the question of whether the opposite of approach in the prefrontal cortex is better described as moving away (Direction Model), as unmoving but with strength and resistance (Movement Model), or as unmoving with passive yielding (Action Tendency Model). Support for the Action Tendency Model (passivity related to right prefrontal activity) comes from research on shyness and research on behavioral inhibition . Research that tested the competing hypotheses generated by all four models also supported the Action Tendency Model . </P> <P> Another neurological approach proposed by Bud Craig in 2003 distinguishes two classes of emotion: "classical" emotions such as love, anger and fear that are evoked by environmental stimuli, and "homeostatic emotions"--attention - demanding feelings evoked by body states, such as pain, hunger and fatigue, that motivate behavior (withdrawal, eating or resting in these examples) aimed at maintaining the body's internal milieu at its ideal state . </P> <P> Derek Denton calls the latter "primordial emotions" and defines them as "the subjective element of the instincts, which are the genetically programmed behavior patterns which contrive homeostasis . They include thirst, hunger for air, hunger for food, pain and hunger for specific minerals etc . There are two constituents of a primordial emotion--the specific sensation which when severe may be imperious, and the compelling intention for gratification by a consummatory act ." </P>

Who proposed that there are different brain systems for different emotions