reducing the threat and believes that he or she can successfully perform the adaptive
response. So, for example, smokers will try to quit smoking when they believe
themselves to be susceptible to smoking-related illnesses that they think to be serious
and where quitting smoking is perceived to be effective in reducing the threat and
perceived to be something they have confidence they can achieve. The PMT has been
successfully applied to the prediction of a number of health behaviours (for recent
reviews see Norman et al., 2005, 2015).
Theory of planned behaviour
The theory of planned behaviour (TPB) was developed by social psychologists and
has been widely applied to understanding health behaviours (Conner and Sparks, 2005,
2015). It specifies the factors that determine an individual’s decision to perform a
particular behaviour (see Figure 7.3). Importantly this theory added ‘perceived
behavioural control’ to the earlier theory of reasoned action (Ajzen and Fishbein, 1980),
which continues to be applied (Ajzen, 2001; Fishbein and Ajzen, 2010). The TPB
proposes that the key determinants of behaviour are intention to engage in that
behaviour and perceived behavioural control over that behaviour. As in the PMT,
intentions in the TPB represent a person’s motivation or conscious plan or decision
to exert effort to perform the behaviour. Perceived behavioural control (PBC) is a
person’s expectancy that performance of the behaviour is within their control and
confidence that they can perform the behaviour. PBC is similar to Bandura’s (1982)
concept of self-efficacy used in the PMT and the extended HBM.
In the TPB, intention is itself assumed to be determined by three factors: attitudes,
subjective norms and PBC. Attitudes are the overall evaluations of the behaviour by
the individual as positive or negative (and so include beliefs about benefits and barriers
included in the HBM). Subjective norms are a person’s beliefs about whether
significant others think they should engage in the behaviour. PBC is assumed to
influence both intentions and behaviour because we rarely intend to do things we
know we cannot and because believing that we can succeed enhances effort and
persistence and so makes successful performance more likely (see Chapter 8). Thus,
according to the TPB, smokers are likely to quit smoking if they form an intention
to do so. Such an intention to quit is likely to be formed if smokers have a positive
attitude towards quitting, if they believe that people whose views they value think
they should quit smoking and if they feel that they have control over quitting
smoking.
Attitudes are based on behavioural beliefs, that is, beliefs about the perceived
consequences of behaviours. In particular, they are a function of the likelihood of a
consequence occurring as a result of performing the behaviour and the evaluation of
that outcome (i.e. ‘Will it happen?’ and ‘How good or bad will it be?’). It is assumed
that an individual will have a limited number of consequences in mind when
considering a behaviour. Thus a positive attitude towards quitting smoking will result
when more positive than negative consequences are thought to follow quitting.
Subjective norm is based on beliefs about salient referents’ approval or disapproval of
whether one should engage in a behaviour (e.g. ‘Would my sexual partner approve?’
and ‘Would my best friend approve?’). These beliefs are weighted by the ‘motivation
to comply’ with each salient other on this issue (e.g. ‘Do I care what my sexual
148 MOTIVATION AND BEHAVIOUR