The Theory of Planned Behaviour– The Good, the Bad and the Usefulness
Theory of Planned Behaviour Ajzen (1985) applied to Vaping.
What is it?
The Theory of Planned Behaviour (TPB) is a model by Ajzen (1985) which proposes that our intentions and perceived behavioural control (PBC) determines whether we carry out a specific behaviour [1]. PBC refers to the perception as to how easy or difficult the behaviour is to enact. PBC also can influence our intentions, as do our attitudes towards the behaviour and surrounding subjective norms (i.e. the approval or disapproval of those around us) (see Figure).
What is it used for?
Dominant in health research, TPB has been used to explain, predict and even intervene in behaviours such as smoking, diet choices, substance use, physical activity and much more. For instance, studies could use the TPB to uncover a population’s underlying beliefs that drive their intention to perform a certain behaviour. From there, researchers could derive a questionnaire to assess said beliefs and differentiate who is less likely to perform the behaviour. They may then design appropriate interventions to change those beliefs and subsequently the behaviour itself [2].
Strengths of TPB.
The theory holds several appeals, including its simplicity and applicability to numerous health areas. Correlational tests provide strong support, with meta-analyses finding intentions to explain high amounts of variance in health behaviours [3]. Furthermore, TPB acknowledges how our beliefs and cultural norms can influence our behaviour.
Limitations of TPB.
Yet, studies that test a TPB-based intervention do not always see a subsequent change in the target behaviour, leading some to question whether the TPB is useful in actually enacting behaviour change [2]. Academics have criticised the TPB for over-emphasising conscious decision-making and point out that many factors outside our awareness play an important role too. For example, factors such as age, socioeconomic status, physical and mental health and environment features predict physical activity more than TPB variables [4]. Furthermore, experiments supporting the TPB typically recruit student samples and are held over a short period of time; once adult samples and longitudinal experiments are held, the TPB is less able to predict individuals’ behaviour.
So is it useful?
Perhaps. TPB is useful as a starting point for many empirical health studies as it provides a way to break down behaviour into discrete variables and form testable hypotheses. Researchers can then narrow down which variables are important to target during behaviour change interventions. However, as critics have pointed out, TPB may not suffice in completely changing behaviour. Other theories, or even extensions of TPB, are more well-versed, such as the Prime Theory of Motivation or Temporal Self-Regulation Theory [4]. As is the case with all theories, its utility wholeheartedly depends on the researchers and practitioners’ end goals.
References
[1] Ajzen, I. (1985). From intentions to actions: A theory of planned behavior. In J. Kuhl & J. Beckman (Eds.), Action-control: From cognition to behavior (pp. 11–39). Heidelberg: Springer.
[2] Hardeman, W., Johnston, M., Johnston, D. W., Bonneti, D., Wareham, N., & Kinmonth, A. L. (2002). Application of the theory of planned behaviour in behaviour change interventions: A systematic review. Psychology & Health, 17(2), 123–158. 10.1080/08870440290013644a
[3] McEachan, R. R. C., Conner, M., Taylor, N. J., & Lawton, R. J. (2011). Prospective prediction of health-related behaviors with the Theory of Planned Behavior: A meta-analysis. Health Psychology Review, 5, 97–144. doi:10.1080/17437199.2010.521684
[4] Sniehotta, F. F., Presseau, J., & Araújo-Soares, V. (2014). Time to retire the theory of planned behaviour. Health psychology review, 8(1), 1–7. https://doi.org/10.1080/17437199.2013.869710