Theory of Planned Behaviour

The theory of planned behaviour (TPB) aims to explain why we decide to act in certain ways. It sets out by 'assumes' that we will behave sensibly; that we will use the information available to us, and think carefully about the implications of our actions (Ajzen, 1991, 2005).

TPB is underpinned by three factors: our personal factors, our social influences, and how controlled we are (Ajzen, 2005):

• Our personal factors: our own feelings, which are our attitude towards a particular act. Our broad attitudes about organisations, people, or things are studied by social psychologists, but what about individual positive or negative evaluations of actions? Our behaviours are considered "overdetermined" as so, so many things combine to produce a particular action. For example, do we think of exercise as being good or bad? Helpful or harmful? Fun or a drag? And if we find exercise is enjoyable and makes us feel great, we are much more likely to keep doing it.
  
  
• Subjective norms/social influences to perform or not perform the behavior under consideration. This is what others think about what we do, and whether the opinions of others matter to us. If our friends, family, or community approve or disapprove of our behaviour, we may be less likely to continue - a perceived 'normative prescription'. If our norm group of friends at Uni think studying hard is cool, we are much more likely to study hard ourselves.
  
  
• Perceived behavioral control, or our sense of self-efficacy or ability to perform the behaviour. If we rate an action, and feel social pressure to do it, AND think we can deliver on it, when we "have the means and opportunities to do so" (Ajzen, 2005, p. 118). So if we think we can do something, we are much more likely to try. It might be our perception of how easy or difficult we think the act is. It might be understanding we have done an earlier version before, and this is just a bit harder. It might be that we have skills, resources, and opportunities to try something similar to a previous experience that we can translate our skills into. As a beginner cook, a family recipe, our memory, and a range of YouTube videos can enable us to make soup for the first time. We are likely to encounter difficulties, but will our mindset (Dweck, 2006) help us to overcome these or become blocked when we encounter them? Understanding the realistic constraints and how we may act is key.

These three TPB variables will help us understand what our intention is likely to be, and therefore how likely it is that we will act in an intended way. The relative weighting of the factors varies from one person to another, or from one population to another. Sometimes, only one or two of the factors are at play, while at others, all three are important. For some intentions our attitudes/personal factors feel more important than social norms, while for others, norms will provide the most influence. Perceived behavioral control is more important for some behaviours than for others, such as do our perceptions of behavioral control align to our actual sense of control? If so, we are more likely to see ourselves doing it, and actually get it done. Being able to measure each of these three factors should help us predict our intentionality. 

Sometimes our perceived behavioral control is not that realistic (often when we don't know much about a task!) and that is where the dotted arrow in the TPB diagram (accompanying this post) indicates that if our perceived behavioural control and our understanding of being able to deliver the act (i.e. actual behaviour; our actual control over our behaviour) do not align, we are unlikely to do behave regardless of our intention. We will be all talk and no trousers.

So TPB is where desire, norms and capability shape our intentions - our plan to act - and our intention then influences our actual behaviour. Poor intention without control leads to little to no action. Having a strong intention with a good sense of control means we are likely to act. 

So if we are in a big city and broke, we could decide to save money by walking to the next bus zone to decrease the fare (personal attitude), gaining exercise (societal norm), and saving money without it being too great a leap (perceived control). 

Sam

References:

Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50(2), 179-211. https://doi.org/10.1016/0749-5978(91)90020-T

Ajzen, I. (2005). Attitudes, Personality and Behavior: Mapping social psychology (2nd ed.). Open University Press.

APCDA. (2025). Gunawan, W., Riasnugrahani, M., Budiwan, T. I., 112b Preparing for the Future: Exploring Employability and Entrepreneurship Antecedents of Uni Students [video]. APCDA Hybrid Conference 12-26 May 2025, Zheng Zhou Shi, China. https://asiapacificcda.vids.io/videos/ea91dbbf1f1de6c163/112b-preparing-for-the-future-exploring-employability-and-entrepreneurship-antecedents-of-uni-students

Dweck, C. (2006). Mindset: The New Psychology of Success. Baltimore Books.