Constructs from theoretical models are often used to elucidate health behaviors and guide interventions, such as smoking cessation programs. The Theory of Planned Behavior is one such model, which is actually an extension of another, the Theory of Reasoned Action. These theories assume that an individual’s attitude, social norms and perceived control over a behavior influence his intention to perform the behavior. That intention, in turn, predicts whether the behavior will occur.
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Attitudes about the target behavior can be direct or indirect. A direct attitude about smoking may be a smoker’s overall assessment about whether quitting is good or bad. An indirect attitude involves how strongly a person believes a peripheral outcome will occur as a result of performing the behavior, coupled with an assessment of that outcome. For example, a smoker might believe that it’s very likely she will gain unwanted weight if she quits smoking.
A subjective norm involves the people around you, more specifically, what you think they think--and how strongly they think it--about a given behavior. A smoker might believe that society disapproves of smoking and therefore approves of quitting. Similarly, advice from a doctor to quit indicates approval for performing the target behavior. Next, the theory would suppose that the smoker will assess how likely or unlikely it is that he will comply with others’ beliefs about quitting.
Perceived Behavioral Control
Perceived behavioral control is much like the concept of “self-efficacy,” an individual’s own confidence in successfully executing a behavior. It accounts for external factors that may affect the person’s intent toward a behavior. Within the context of smoking, a person might consider factors that may help or hinder quitting. For example, a smoker determines that if she quits there will be withdrawal symptoms, but she is confident that her new daily walking regimen will help.
According to the Theory of Reasoned Action and the Theory of Planned Behavior, the individual’s intent to perform a behavior predicts the occurrence of that behavior. Assuming this is true, the appeal is that if intention influences behavior, then interventions can strategically identify and target factors--in this case, attitudes, norms and perceived behavioral control about quitting smoking--that influence intention. While a 2006 study by Godin et al. published in the "British Journal of Addiction" supports this relationship between intention and behavior, the article also acknowledges other studies that do not.
Assumptions and Utility
The Theory of Reasoned Action and Theory of Planned Behavior assume a causal relationship between an individual’s attitudes about a behavior, her intention, and the actual performance of that behavior. Another assumption is that people process every piece of information and act accordingly. Simple observation of many smokers will likely reveal that even the best intentions do not necessarily result in quitting. Yet, examination of these constructs is helpful in understanding the complexities of human behavior.