comply with this pressure (e.g. ‘people who are important to me will approve if I lose
weight and I want their approval’); Perceived behavioural control, which is composed of a belief that the individual can
carry out a particular behaviour based upon a consideration of internal control
factors (e.g. skills, abilities, information) and external control factors (e.g. obstacles,
opportunities), both of which relate to past behaviour.
According to the TPB, these three factors predict behavioral intentions, which are then
linked to behaviour. The TPB also states that perceived behavioural control can have a
direct effect on behaviour without the mediating effect of behavioural intentions.
Using the TPB
If applied to alcohol consumption, the TPB would make the following predictions: if
an individual believed that reducing their alcohol intake would make their life more
productive and be beneficial to their health (attitude to the behaviour) and believed
that the important people in their life wanted them to cut down (subjective norm),
and in addition believed that they were capable of drinking less alcohol due to
their past behaviour and evaluation of internal and external control factors (high
behavioural control), then this would predict high intentions to reduce alcohol
intake (behavioural intentions). The model also predicts that perceived behavioural
control can predict behaviour without the influence of intentions. For example, if
perceived behavioural control reflects actual control, a belief that the individual
would not be able to exercise because they are physically incapable of exercising
would be a better predictor of their exercising behaviour than their high intentions
to exercise. Using the TPB to predict exercise is described in Focus on research 7.2,
page 179.
Support for the TPB
The theory of planned behaviour has been used to assess a variety of health-related
behaviours. For example, Brubaker and Wickersham (1990) examined the role of the
theory’s different components in predicting testicular self-examination and reported that
attitude towards the behaviour, subjective norm and behavioural control (measured as
self-efficacy) correlated with the intention to perform the behaviour. A further study
evaluated the TPB in relation to weight loss (Schifter and Ajzen 1985). The results
showed that weight loss was predicted by the components of the model; in particular,
goal attainment (weight loss) was linked to perceived behavioural control.
Criticisms of the TPB
Schwarzer (1992) has criticized the TPB for its omission of a temporal element and
argues that the TPB does not describe either the order of the different beliefs or any
direction of causality. However, in contrast to the HBM and the PMT, the model attempts to
address the problem of social and environmental factors (in the form of normative beliefs).
HEALTH BELIEFS 33