The theory of planned behaviour (TPB) was proposed by Ajzen (1989) as a refinement to the earlier theory of reasoned action proposed in the 1970s by Ajzen and Fishbein. It helps us to understand how humans can change a behaviour (e.g. reduce addiction). The model claims that behaviour is controlled by intentions. These intentions vary in their strength and are influenced by three factors: behavioural attitudes about the outcome of the behaviour and the value placed upon the outcome; the individual’s subjective norms (their perception of how others would view the behaviour); and perceived behavioural concerns (the extent to which they feel they can actually perform the behaviour). The TPB can be used to explain the processes that led to addiction, and also be applied to help develop appropriate programmes to bring about long-lasting changes in addictive behaviour. The theory suggests that in order to change the behaviour, you need to change the behavioural attitudes (create a different attitude towards smoking or gambling); change the subjective norms by giving actual data about the number of people who actually engage in the risky behaviour (e.g. the number of teenage smokers or pathological gamblers), and change the perceived behavioural control, by helping smokers or gamblers to focus on the willpower and effort required to give up their behaviour.