Theory  of  Planned  Behaviour

The Theory of Planned Behaviour (TPB) is an extension of the Theory of Reasoned Action.

The theory is based on consumers using available information and “implicitly or explicitly consider the implications of their actions” (Ajzen, 2005, p. 117). The TRA has limitations when dealing with behaviours where individuals do not have complete control. Complete control means that a person can decide to perform or not perform a given behaviour (Ajzen, 1991). A central factor in TPB, as well as in TRA, is intention to behave in a certain manner.

As Ajzen (1991) states, “intentions are assumed to capture the motivational factors that influence a behaviour”. A third factor is added, which resulted in the TPB to address the issue of incomplete control, namely perceived behavioural control (Harari and Legge, 2001).

Perceived behavioural control (PBC) is the perception a person has of how easy or difficult it is to perform the behaviour, and can vary depending on the situation (Ajzen, 1991). A person with more confidence in what he is doing is more likely to keep trying than a person who lacks confidence. PBC can be linked to self-efficacy theories (Ajzen, 1991), where perceived self-efficacy refers to the confidence an individual has in the ability to perform the behaviour needed in a given situation (Bandura, 1997). Self-efficacy beliefs can affect which activities a person choose to perform, how he or she prepares for the activity, level of effort during the performance, way of thinking, and emotional reactions (Ajzen, 1991).

Behaviour is dependent on both motivation (intention) and ability (behavioural control), and it is the resources and opportunities available to an individual that to a certain degree determines the likelihood of achieving the behaviour. Examples of resources that can influence behaviour are time, money, personal skills and cooperation of others (Ajzen, 1991).

Perceived behavioural control can be shown as in the following equation:

PBC = α∑ⁿi=1 cipi

Equation 3: Perceived behavioural control (Ajzen, 1991)

PBC is a function of each control belief (ci) multiplied by the perceived power (pi) of a particular control factor. (n) equals number of control beliefs. Control beliefs deals with the availability of resources and opportunities based on past experience or second-hand information. Furthermore they can be based on the experiences of others or by factors that

can increase or decrease perceived difficulty in performing the behaviour. Perceived power is the perceived control an individual has over the behaviour (Ajzen, 1991).

The TPB can be presented as below:

Model 2: Theory of Planned Behaviour (Ajzen 1991)

TPB by Ajzen (1991) is a function of three determinants; perception of a persons ability to perform the behaviour, attitude towards the behaviour and normative pressure. Individuals will have greater intentions to perform the behaviour if they feel that it is within their control. Depending on the situation only two of the three factors may be needed to explain intention, or in other instances the weighting of them can vary (Ajzen, 2005).

Perceived behavioural control is directly related to behaviour in addition to predict intention.

One reason is that with higher perceived behavioural control, a successful end-state is more likely. A second reason is that perceived behavioural control can often be used as a substitute to measure actual control. However it depends on the accuracy of the perceptions. If accuracy is high, perceived behavioural control can, in addition to intention to perform the behaviour, help predict actual behaviour. Accuracy may be weak if a person lacks

information about the behaviour, if available resources or requirements change, or with the entrance of new and unfamiliar elements (Ajzen, 1991).

TPB has been applied to predict behaviour in many studies. Thorbjørnsen et al. (2007) used an extended version of the model in the context of Multimedia Messaging (MMS) adoption.

They include the concepts of self-identity expressiveness and social identity expressiveness to predict intentions, and their results indicate that behavioural intention is driven by variables reflecting intrinsic motives for use and identity expressiveness. Subjective norm is not a direct predictor of intentions but indirectly through its affect on social identity expressiveness. Pelling and White (2009) used an extended TPB to investigate the intentions to use social networking web-cites where attitude, subjective norm, self-identity and past behaviour were significant, while Su and Huang (2011) studied the intention of undergraduate consumers to shop online in China by applying the TPB.

3.3.2.1 Limitations and strengths

The TPB has been highly influential in explaining relations between attitude, intention and behaviour (Thorbjørnsen et al., 2007). The model is a better predictor of behaviour than TRA as it includes one additional factor. This model cannot explain all variances (Harari and Legge, 2001), however a considerable proportion of it (Ajzen, 1991). Studies have shown that by including perceived behavioural control it can explain an extra two percent of variance in behaviour (Cheung and Chan, 2000; Armitage and Conner, 2001; Ajzen, 2005).

This component separates the TPB from the TRA, although it might not be necessary for all types of behaviour to include this component. A strength with the TPB, as with the TRA, is the lack of attributes already incorporated in the models. Researchers can therefore decide which attributes to include.

Researchers have questioned the subjective norm component, and studies by Armitage and Conner (2001, as cited in Thorbjørnsen et al., 2007) found subjective norm to be a weak predictor of intentions. They stressed the need to expand the subjective norm and add variables related to identity and sociality. Identity expressiveness should be included to predict intention rather than the subjective norm isolated (Thorbjørnsen et al., 2007).

Ajzen (1991) claims that the TPB is highly useful in understanding behaviours, as intention, attitude towards behaviour, subjective norm and perception of behavioural control reveals

different aspects of a type of behaviour. The beliefs behind the components enable researchers to gain information about what determines a type of behaviour.