The Theory of Planned Behaviour (AQA A Level Psychology): Revision Note

The theory of planned behaviour (TPB)

• TPB is a cognitive theory that can be applied to explain many behaviours and efforts to change behaviour, including addiction

• Ajzen (1991) developed the TPB to explain how intention and beliefs affect behaviour change

• The core idea of the TPB is that to predict the outcome of an effort to change behaviour, it is necessary to consider the intention of the individual, which is affected by their attitudes, beliefs and perception of control

• TPB states that any behaviour, which would include addiction, is affected by the intention to behave in a certain way

• Intention has three main components:

  • Behavioural attitude – the degree to which the individual approves or disapproves of the behaviour and a consideration of the outcomes

  • Subjective norms – these refer to an individual’s beliefs and feelings about whether people they value/admire/love think the individual should engage in the behaviour

  • Perceived behavioural control – the perception of the control the individual believes they have over the behaviour, with a perception of strong control leading to more chance of the behaviour occurring

The role of the TPB in changing addictive behaviour

• It is possible to apply the TPB to explain how an individual’s attitudes, beliefs and perception of control affect the likelihood of them being able to change their addictive behaviour

• For example, for an individual wanting to make behavioural changes to stop smoking:

  • Behavioural attitude – the individual wants to give up smoking, as they hold the belief that smoking is bad for their health and they need to quit, e.g., ‘I am so sick of feeling unwell due to my smoking.’

  • Subjective norms -  the individual perceives that their family and friends have a negative attitude to smoking and disapprove of their behaviour, e.g., ‘I want my children to see that I no longer smoke, that I’ve managed to quit this horrible habit’

  • Perceived behavioural control – the individual believes they can control their behaviour and the likelihood is they will be successful in stopping smoking, e.g., ‘I am confident that I can successfully quit smoking’

• After going through the above processes, the individual should – in theory – stop smoking

• The TPB may be used to explain the process of changing any addictive behaviour

• The TPB can also be used to explain why some people are more successful than others at changing their addictive behaviour, as if they missing any of the required attitudes, subjective norms or perceived behavioural control, then behaviour change will be much harder for them

Research which investigates the theory of planned behaviour

• Oh & Hsu (2001) used a questionnaire to assess gamblers’ behavioural intentions, attitudes, subjective norms and perceived behavioural control and found a positive correlation between attitudes and behavioural intentions and actual behaviour change, supporting the TPB

• Godin et al. (2006) investigated the extent to which the TPB could explain intentions and behaviours in adults intending to give up smoking and found that perceived behavioural control was the most important predictor of success

Evaluation of the theory of planned behaviour

Strengths

• The theory is used widely in health psychology, suggesting that medical professionals acknowledge its validity and its predictive power, meaning it has useful practical application 

• Peers have already been shown to be important in starting an addictive behaviour, and this theory acknowledges their role (subjective norms) in influencing behaviour change in order to end the addiction

Weaknesses

• The theory does not consider emotion as a key factor in addiction, focusing instead on the less emotional processes involved, such as motivation and beliefs, which limits its scope as an explanation of behaviour change

• The model relies mainly on self-report questionnaires as a research method, which is a problem, as individuals may show social desirability effect and downplay the level of their addiction, meaning the results may lack internal validity 

Issues & Debates

• TPB is a nomothetic theory, aiming to predict behaviour across large groups through general laws of cognition and intention

  • This may overlook individual differences in addiction recovery, such as emotional motivation or unique personal history

• TPB supports the idea of free will, as it focuses on intentional decision-making based on beliefs, attitudes, and perceived control

  • However, it could be argued that these cognitive processes are influenced by external factors, aligning it partially with soft determinism