The theory states that attitude toward behavior, subjective norms, and perceived behavioral control, together shape an individual's behavioral intentions and behaviors.
1 Extension from the theory of reasoned action
The theory of planned behavior was proposed by Icek Ajzen in 1985 through his article "From intentions to actions: A theory of planned behavior." The theory was developed from the theory of reasoned action, which was proposed by Martin Fishbein together with Icek Ajzen in 1975. The theory of reasoned action was in turn grounded in various theories of attitude such as learning theories, expectancy-value theories, consistency theories, and attribution theory. According to the theory of reasoned action, if people evaluate the suggested behavior as positive (attitude), and if they think their significant others want them to perform the behavior (subjective norm), this results in a higher intention (motivation) and they are more likely to do so. A high correlation of attitudes and subjective norms to behavioral intention, and subsequently to behavior, has been confirmed in many studies.
A counter-argument against the high relationship between behavioral intention and actual behavior has also been proposed, as the results of some studies show that, because of circumstantial limitations, behavioral intention does not always lead to actual behavior. Namely, since behavioral intention cannot be the exclusive determinant of behavior where an individual's control over the behavior is incomplete, Ajzen introduced the theory of planned behavior by adding a new component, "perceived behavioral control." By this, he extended the theory of reasoned action to cover non-volitional behaviors for predicting behavioral intention and actual behavior.
2 Extension of self-efficacy
In addition to attitudes and subjective norms (which make the theory of reasoned action), the theory of planned behavior adds the concept of perceived behavioral control, which originates from self-efficacy theory (SET). Self-efficacy was proposed by Bandura in 1977, which came from social cognitive theory. According to Bandura, expectations such as motivation, performance, and feelings of frustration associated with repeated failures determine effect and behavioral reactions. Bandura (1986)[full citation needed] separated expectations into two distinct types: self-efficacy and outcome expectancy. He defined self-efficacy as the conviction that one can successfully execute the behavior required to produce the outcomes. The outcome expectancy refers to a person's estimation that a given behavior will lead to certain outcomes. He states that self-efficacy is the most important precondition for behavioral change, since it determines the initiation of coping behavior.
Previous investigations have shown that peoples' behavior is strongly influenced by their confidence in their ability to perform that behavior (Bandura, Adams, Hardy, & Howells, 1980).[full citation needed] As the self-efficacy theory contributes to explaining various relationships between beliefs, attitudes, intentions, and behavior, the SET has been widely applied to health-related fields such as physical activity and mental health in preadolescents, and exercise.
2 Concepts of key variables
1 Behavioral beliefs and attitude toward behavior
Behavioral belief: an individual's belief about consequences of...