much more likely to intend to enact certain behaviors when they feel that they can enact them successfully. The theory has thus improved upon TRA. Extension of self-efficacy Along with attitudes and subjective norms (which make up TRA), TPB adds the concept of perceived behavioral control, which grew out of self-efficacy theory (SET). The construct of self-efficacy was proposed by Bandura in 1977, in connection to social cognitive theory. Self-efficacy refers to a person's expectation or confidence that he or she can master a behavior or accomplish a goal; an individual has different levels of self-efficacy depending upon the behavior or goal in question. Bandura distinguished two distinct types of goal-related expectations: self-efficacy and outcome expectancy. He defined self-efficacy as the conviction that one can successfully execute the behavior required to produce the outcome in question. Outcome expectancy refers to a person's estimation that a given behavior will lead to certain outcomes. Bandura advanced the view that self-efficacy is the most important precondition for behavioral change, since it is key to the initiation of coping behavior. Previous investigations have shown that a person's behavior is strongly influenced by the individual's confidence in his or her ability to perform that behavior. As self-efficacy contributes to explanations of various relationships among beliefs, attitudes, intentions, and behavior, TPB has been widely applied in health-related fields such as helping preadolescents to engage in more physical activity, thereby improving their mental health, and getting adults to exercise more. Key concepts Normative beliefs and subjective norms Normative belief: an individual's perception of social normative pressures, or the beliefs of relevant others bearing on what behaviors should or should not be performed. Subjective norm: an individual's perception about the particular behavior, which is influenced by the judgment of significant others (e.g., parents, spouse, friends, teachers). Control beliefs and perceived behavioral control Control beliefs: an individual's beliefs about the presence of factors that may facilitate or hinder performance of the behavior. Perceived behavioral control: an individual's perceived ease or difficulty of performing the particular behavior. The concept of perceived behavioral control is conceptually related to self-efficacy. It is assumed that perceived behavioral control is determined by the total set of accessible control beliefs. Behavioral intention and behavior Behavioral intention: an individual's readiness to perform a given behavior. It is assumed to be an immediate antecedent of behavior. It is based on attitude toward the behavior, subjective norm, and