The Theory of Reasoned Action

Icek Ajzen’s “Theory of Reasoned Action” is a useful tool for predicting an individual’s or group’s behavior considering several key constructs. The theory’s premise is that people behave according to their reasoning and intentions, when the opportunity allows. The primary construct, intentions, is assumed to have a direct effect on the specified behavior, and these intentions are influenced by two other key constructs, attitude and subjective norms. The theory of reasoned action informs health promotion strategists regarding the specific construct that they should be targeting when trying to motivate healthier decision making. Because the three constructs are mere perceptions, health educators can influence these beliefs, leading people to adopt the targeted behavior.

Intentions in this context are defined as the subjective probability of performing a behavior, which can be assessed with the Likert scale. Accordingly, surveys should directly ask the participants how likely it is that they would perform the activity in question on a scale from 1 to 5, 1 being very unlikely and 5 being very likely, with a gradient of likeliness in between these options.

Attitudes then have a direct influence on these intentions. Attitudes can be either experiental or instrumental, and these are directly impacted by two secondary constructs: behavioral beliefs and outcome evaluations. The former regards the beliefs about the outcome of the behavior, while the latter is the individual’s perception of how favorable or unfavorable that outcome is. In order to assess attitudes, participants should be asked about the positive or negative connotations they would ascribe to performing the behavior in question.

In addition to attitudes, subjective norms are another construct of the theory that have a direct impact on an individual’s intention to perform a behavior. Two secondary constructs also affect the subjective norm: normative beliefs and motivation to comply. The former takes into account the beliefs of influential people in the individual’s life (parents, peers, celebrities), while the latter assesses an individual’s willingness to adhere to these norms. If motivation to comply is low, then the subjective norms are likely to have little impact on intentions. Assessing this construct is much more difficult as researchers must determine who is important in an individual’s life as well as the influence that these people can have.

In order for the theory to be successful, several assumptions must be met. People must be acting rationally, their beliefs must be stable, and intentions must be the determinant of behavior. For example, if someone had the full intention to stop smoking and knew that smoking led to poor health, that person would cease smoking if they were completely rational. But people are not completely rational, and often emotional drives can also influence our choices. Thus, critics have argued that the theory is limited in this regard. Ajzen also noted that the theory is only useful for predicting behaviors that are under complete volitional control, which led to a slight modification of the theory in a later publishing. He incorporated the construct of perceived behavioral control, which improved the statistical power to predict behavior for instances where full volitional control is not possible.

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