Today cognitive theorists empirically study the impact of feelings on cognitive processes such as memory and judgment and also the reciprocal influence of cognition on emotion. However, evolutionary theorists view emotion as a powerful source of motivation—an internal communication that something must be done. For example, when people are threatened, they fed fear, which in turn leads them to deal with the threatening situation through either fight or flight. Emotions and drives may also operate in tandem to motivate action, as when excitement accompanies sexual arousal. From an evolutionary perspective, different emotions serve different functions. Fear facilitates flight in the face of danger; disgust prevents ingestion me potentially toxic substances such as rotting meat. An emotion that is less well understood is jealousy. Why do people become jealous in intimate sexual relationships? One series of studies tested evolutionary hypotheses about differences in the concerns men and women have about their partners' fidelity. Since females can have only a limited number of children during their lifetimes, to maximize their reproductive success they should be motivated to form. relationships with males who have resources and will contribute them to their offspring. Indeed, cross-cultural evidence demonstrates that one of the main mate selection criteria used by females around the world is male resources. From a female's point of view, then, infidelity accompanied by, emotional commitment to the other woman is a major threat to resources. A man unlikely to divert resources from his mate and her offspring to a casualling, but the risk increases dramatically if he becomes emotionally involved and perhaps considers switching long-term partners. Hence, a woman's jealousy would be expected to focus on her mate's emotional commitment to another female. For males, the situation is different. If a male commits himself to an exclusive relationship with a female, he must be certain that the offspring in whom he is investing are his own. Since he cannot be sure of paternity, the best he can do is to prevent his mate from copulating with any other males. In males, then, jealousy would be expected to focus less on the female's emotional commitment or resources and more on her tendency to give other males sexual access. Indeed, in species 'ranging from insects to humans, males take extreme measures to prevent other males from inseminating their mates. In humans, male sexual jealousy is the leading cause of homicides and of spouse battering cross-culturally. This passage discusses the______approach to human emotions.