When a Plan Comes Together

The theory of planned behaviour is a model that tries to predict human behaviour. As noted by the author, Icek Azjen, explaining behaviour is a difficult task due to the many complex psychological variables that must be taken into account. The theory of planned behaviour is a relatively simple and accurate model and it is mainly for these reasons it has garnered a lot of attention among researchers. Even for those of us who had not heard of this theory beforehand it continues to be a relevant part of our lives since it is used to predict our behaviour towards many social projects (such as our intention to donate blood).

Theory of Planned Behaviour Model

As you can see, the model looks fairly simplistic, but the jargon can get in the way of our understanding. Let’s break it down:

Behaviour and Intention are fairly straight forward; behaviour is the action we take and our intention is our plan or motivation to commit to that action. Keep in mind that intention does not always lead to behaviour – but studies have shown that expressing that intent multiple times leads to an increased chance of taking action (Cooke & Sheeran, 2004). So the question is what determines our intentions. In this model the predictors of Intention are Attitudes, Subjective Norms and Perceived Behavioural Control (PBC).

  • Attitude (toward the behaviour) is our perception on whether the act is favourable. For example, if we believe exercise is good for our health then that can lead to an intention to start or increase our exercise regime.
  • Subjective Norm refers to the degree to which important people in our lives condone a certain act. This means our family, friends and colleagues can have an impact on our intentions depending on their beliefs.
  • Perceived Behavioural Control is a person’s perception that they can engage in an action successfully. Put simply, if we believe we can perform a task with the resources we have at hand then we are more likely to engage in that task. PCB can also prevent us from taking an action if we believe the resources are not enough (such as time constraints). The best example I can think of is studying; if we believe we are knowledgeable and disciplined with enough time to complete our assignment then we are more likely to have intent to begin the work. Perhaps the most interesting part of PCB is that we do not necessarily need intent to do something in order to engage in an action (behaviour). This occurs when we are oblivious to factors that facilitate or obstruct our intended behaviour.

So what do you think of Azjen’s theory of planned behaviour? Can you think of examples in your own life that support (or perhaps go against) the theory?

Ajzen, I. (1991). The Theory of Planned Behaviour. Organisizational Behavior and Human Decision Processes, 50, 179-211.

Cooke, R., & Sheeran, P. (2004). Moderation of cognition-intention and cognition-behaviour relations: A meta-analysis of properties of variables from the theory of planned behaviour. British Journal of Social Psychology, 43, 159-186.


6 comments so far

  1. ashfonty on

    The theory of planned behaviour is a very interesting concept. When you break it down into the things that can influence our intentions its interesting to consider what has the most weight in the process.

    For me, exercise if one of the big things I ‘intend’ to do more of, but never really get around to! While my attitude towards exercising is very positive and people in my life have the same view (but not neccesarily the actions), I’d have to say that its definitely my perceived behavioural control that holds me back. As a uni student holding down two jobs I certainly feel time-poor (I’m sure everyone can relate) so often while the intention is there, I don’t really get to follow through.

    So I definitely agree with Azjen’s model here as it highlights that perceived behavioural control has a greater influence in directing behaviour.

    • Aaron Cull on

      Yes, and it’s interesting to note how PBC was not included in the original model before this paper was released. You’re right in saying everyone can relate to having time constraints, although I did find it interesting how Azjen noted this as an inhibitor to action since a lack of time can sometimes spur someone into action for something they consider important.

      Perhaps in your case, exercise is not as important as finishing an assignment that’s due soon, and your perception of that importance is still based on the attitudes and norms discussed earlier.

  2. […] I find the idea of activating social norms an interesting tactic. The fact that we want to do what others perceive as appropriate as well as what others are doing is something I don’t think about, yet agree with. People would struggle daily to do what is right compared to what everyone else is doing. It’s peer pressure in a nutshell! Aligning injunctive and descriptive norms would not be an easy task for some PSA’s. However, Cialdini’s (2003) evidence seems to support that this is the most effective way to deliver your message and create intent to change behaviours (for more information on this see Azjen’s theory of planned behaviour in When a Plan Comes Together). […]

  3. osullivankate on

    I agree with both you and Ash on this one. I wonder which part really has the most impact on changing my behaviours.

    I find it interesting the number of people who are heavily effected by the social norm, which can there by prevent them taking action. Peer pressure exhibits such a control on peoples lives, and I wonder how much it actually overshadows our own individual opinions.

    • Aaron Cull on

      Yes, it’s almost like the author has tried to balance the predictors so that if you have two out of three supporting an action then you would be more likely to do something. How then do we assess what plays a more important role in our lives individually? People in different cultures will probably be affected by social norms more or less, but in the end, having only one of these predictors support an action will probably not be enough to go further than intention.

      I think this is the main purpose of the study, to find a model that predicts our actions based on the most balanced principles we can get. Perhaps this is why the model is so famous, because it is so accurate at predicting our behaviour regardless of our perceived importance of attitudes, norms and PBC.

  4. axl1228 on

    I can’t tell that which one is playing the most important role, but PBC is really a key part of changing our behaviours. More psychological facts are involved in the process, such as expectation of a mission, evaluation of success rate…
    And I think it’s reasons of PBC that result in procrastination, which is a special type of behaviour.

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