This work is centered in explaining what psychological (cognitive and affective) and social factors can explain the beginning, the maintenance and the end of a behavior. Most of previous studies have considered the attitudes like the main variables implied in the behavior. In this order of things, the Theory of Reasoned Action (TAR) and the Theory of Planned action (TAP) show the importance of the attitudes in the formation of the intention of behavior. In both theories, besides the cognitive factors, the importance of the affective factors is underlined in the formation of the attitude. However, from our point of view, the influence of the affective factors is crucial, deserving a detalled study. Zimbardo y Leippe (1991) consider the attitude like an evaluation toward an object, being able to locate to this evaluation, of something or of somebody, along a continuous one that goes from the pleasure until the disliking.