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Theory of Planned Behavior


The theory of planned behavior (TPB), outlined by Icek Ajzen in 1988, is an extension of the theory of reasoned action in that it identifies the importance of assessing the amount of control an individual has over behaviors and attitudes (perceived behavioral control). The TPB takes into account that all behavior is not under volitional control and that behaviors are located at some point along a continuum that extends from total control to a complete lack of control. Control factors include both internal factors (such as skills, abilities, information, and emotions) and external factors (such as situation or environmental factors). The components of the model, as they relate to behavioral intention, include attitude toward the behavior, subjective norms, and perceived behavioral control.

Donald E. Morisky

(see also: Attitudes; Behavioral Change; Health Belief Model; Social Cognitive Theory; Theory of Reasoned Action )


Ajzen, I. (1988). Attitudes, Personality, and Behavior. Chicago: The Dorsey Press.

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