Desire is a sense of longing or hoping for a person, object, or outcome. The same sense is expressed by emotions such as "craving." When a person desires something or someone, their sense of longing is excited by the enjoyment or the thought of the item or person, and they want to take actions to obtain their goal. The motivational aspect of desire has long been noted by philosophers; Thomas Hobbes (1588–1679) asserted that human desire is the fundamental motivation of all human action. While desires are often classified as emotions by laypersons, psychologists often describe desires as different from emotions; psychologists tend to argue that desires arise from bodily structures, such as the stomach's need for food, whereas emotions arise from a person's mental state. Marketing and advertising companies have used psychological research on how desire is stimulated to find more effective ways to induce consumers into buying a given product or service. While some advertising attempts to give buyers a sense of lack or wanting, other types of advertising create desire associating the product with desirable attributes, by showing either a celebrity or a model with the product. The theme of desire is at the core of romance novels, which often create drama by showing cases where human desire is impeded by social conventions, class, or cultural barriers. The theme of desire is also used in other literary genres, such as gothic novels (e.g., Dracula by Bram Stoker, in which desire is mingled with fear and dread). Poets ranging from Homer to Toni Morrison have dealt with the themes of desire in their work. Just as desire is central to the written fiction genre of romance, it is the central theme of melodrama films, which use plots that appeal to the heightened emotions of the audience by showing "crises of human emotion, failed romance or friendship", in which desire is thwarted or unrequited.