Theory of planned behaviour- Ajzen (1989)

Theory of planned behaviour- Ajzen (1989)

Cognitive theory - 3 factors, that lead to decision to engage in particular behaviour. Can be directly predicted by their intention to engage in the behaviour. 

Behavioral attitudes - individuals' beliefs about addictive behaviour and the associated consequences of that behaviour, both pos and neg. 

Subjective norms - individual's subjective awareness of social norms related to the addictive behaviour as well as their own beliefs about significant others would view the behaviour. e.g. if parents are against smoking you are less likely to engage in the behaviour 

Perceived behavioural control - linked to self efficacy. Relates to individual's perceived control over the addicitive behaviour and ability to manage it. 

Therefore in order to prevent addiction we must consider factors that contribute to intention and manipulate these factors. e.g. changing behavioural attitudes about addictive behaviour from pos to neg.

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Practical applications

The TPB can be used as an explanatory frameworkfor understanding the processes that lead to addiction. Also means to understanding prevention and treatment. Thus can be used to help develop appropriate programmes to bring about long lasting changes

practical applications - Rise et al - Found that behavioural attitude and subjective norms played more important role than other aspects of the TPB in predicting whether smokers would actually quit.   This suggests that TPB is a valid theory. research supports ideas that behavioural attitude and subjective norms influence individual's intention towards addicitive behaviour.

Godin et al- examined extent to which the TPB could explain smoking intentions and behaviours in adults intending to give up smoking. Data collected using self report techniques. Found that 3 elements of TPB helped to explain intentions, whereas perceived control was the most important predictor of ultimate addictive behaviour. The researchers concluded that prevention programmes should help smokers to focus on will power required to give up smoking and alert smokers to the effort needed to modify smoking behaviour.  This suggests that TPB is effective understanding of individual intentions because the findings support that each factor contributes to whether an individual will start smoking. Therefore can be used to prevent addicitive behaviour. H/E self report findings may not be valid 

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Practical applications cont..

Slater et al - Campaign launches (2005) to lower teenage marijuana use found to be highly effective, Review of efffectivness attributes its success to its influence on attitudes. Previous campaigns focused on risk of abuse but many teenagers not risk avoidant. The campaign called 'Above the influence' tried to create different attitude towards effect of marijuana use; namely that it is inconsistent with being autonomous and achieving aspirations. This target on attitudes may be key to success of current campaign. 

This suggests that the behavioural attitude is main factor that influences addicition and therefore TPB can be seen to be effective as can be used to prevent such addictive behaviours. If we can change these attitudes we can help prevent addicitive behaviour. 

Wilson and Kolander (2003) - highlighted anti- drug campaigns look to give actual data about the % of people angaging in risk behaviour. This is done to change nebjective norms. H/E most adolescents don't smoke therefore exposure to statistical info should correct subjective norms and should form an effective campaign.  This suggests that TPB is effective as it guides interventions such as anti smoking campaigns. Also if it shows that subjective do play a part in influence of smoking initiation so therefore beliefs do need to be altered in order to overcome the behaviour. Supports the role of subjective norms in the development of addictive behaviour. Also if we can change these norms/ make individuals aware of norms, can reduce/prevent/change addicitive behaviour.

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TPB: Evaluation


Theory criticised for being too rational and not taking into account individuals' emotions, compulsions or other irrational determinants of behaviour (Armitage et al 1999). E.g. when completing a questionnaire about attitudes and intention, people might find it immposible to anticipate the strong desires and emotions that drive their behaviour in real life.This is a weakness because it is oversimplisitic as it only explains addicitive behaviour in terms of thought processes and fails to acknowledge other factors.

Self report techniques - lack reliability, validity and generalisability. Means that results used are innaccurate and weakens the theory. ( social desirability bias, retrospective)

Predicts intention rather than behaviour change. Has been suggested that TPB is primarily an account of intention formation rather than specifying the processes involved in translating the intention into action. - Cannot predict behaviour change so cannot be applied/ translated to intention of behavioural change. 

Correlational analysis - Weakness because research on TPB is based mainly on correlational data and therefore can't establish cause and effect. Based on idea that though process influence reducing addictive behaviour. However cannot established correlational link. 

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