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Wednesday, February 9, 2011

The theory of planned behaviour

The theory of planned behaviour
The theory of planned behaviour (figure 19.4) was developed by Ajzen and colleagues (Ajzen, 1985; 1988; Ajzen & Madden, 1986). It emphasizes behavioural intentions as the outcome of a combination of several beliefs .The theory proposes that intentions should be conceptualized as ‘plans of action in pursuit of behavioural goals’ (Ajzen & Madden, 1986), and that these are a result of the following composite beliefs:

Attitude towards a behaviour – composed of a positive or negative evaluation of a particular behaviour, and beliefs about the outcome of the behaviour (‘Exercising is fun and will improve my health’).

Subjective norm – this represents the beliefs of important others about the behaviour, and the individual’s motivation to comply with such beliefs (‘People who are important to me will approve if I lose weight, and I want their approval’).

Perceived behavioural control – comprising a belief that the individual can carry out a particular behaviour based on a consideration of internal control factors (e.g. skills, abilities, information) and external control factors (e.g. obstacles, opportunities) – both of which are related to past behaviour.

These three factors predict behavioural intentions, which are then linked to behaviour. (The theory of planned behaviour also states that perceived behavioural control can have a direct effect on behaviour without the mediating effect of behavioural intentions.)Applied to alcohol consumption, the theory would predict that someone will have high intentions to reduce alcohol intake (behaviour intentions) if he believes that:reducing his alcohol intake will make his life more productive and be beneficial to his health (attitude to the behaviour);the important people in his life want him to cut down (subjective norm); and he is capable of drinking less alcohol due to his past behaviour and evaluation of internal and external control factors (high behavioural control).
The model also predicts that perceived behavioural control can predict behaviour without the influence of intentions. For example, a belief that the individual would not be able to exercise because they are physically incapable of doing so might well be a better predictor of their exercising behaviour than their high intentions.

Howard Leventhal (1931– ) is Professor of Psychology at the State University of New Jersey at Rutgers. He has carried out extensive research into the experience of being ill, which has informed much work on illness perceptions, and he developed the self-regulatory model of illness behaviour. He places emphasis on the role of symptom perception in triggering illness behaviour and the links between emotion and health.

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