Using the Theory of Planned Behavior in Program Design

Melissa Cater, PhD

In the summary of my last post, I posed the question, “How do we develop programs which target changed attitudes?” Today, we will delve into Ajzen’s (1991) Theory of Planned Behavior and look at one answer to that question.

Ajzen first described the Theory of Planned Behavior (TPB) in 1985. According to this theory, human behavior is influenced by attitudes and self-efficacy as well as by social norms surrounding the behavior. This is a really useful theory for Extension programming because it targets beliefs, and the attitudes and perceptions associated with those beliefs, in program design (see Figure 1).  In fact, one of our more popular types of program evaluation questions, intention to change or adopt a behavior, is solidly connected to the TPB model. A person’s intention to adopt a particular behavior should increase as the person develops a more positive attitude toward, and more confidence in, their ability to perform a behavior and as feedback from important people in their social sphere increases (Ajzen, 2006). Increasing intention to change and control over a particular behavior increases the likelihood of adoption of a behavior (Ajzen, 2011).

Using TPB in Program Design

Ajzen (2006) provides program design guidance which is extremely relevant to Extension programming (see Figure 2).

While all of this sounds really nice in theory, where is the practical application? Well, let’s see if we can overlay this theory with an Extension program.  We’ll frame this scenario using the following very simple logic model (see Figure 3) and then overlay a possible scenario using the TPB.

In beginning the program design process, we identify a long-term outcome of improving a family’s dietary quality. In this very simplistic model, we set a medium-term outcome of increasing vegetable intake. As this goal may be affected by accessibility of vegetables, the short-term outcome focuses on increased accessibility. Our program focuses on increasing accessibility by teaching families to grow their own vegetables in a limited-space environment.

The TPB-driven program design process would begin by identifying the target audience. This would be followed by an informal information gathering stage (the pilot study) with a small group of people within the targeted group. In this step, questions concerning vegetable accessibility, beliefs about gardening as a means of increasing accessibility, beliefs about social acceptability of gardening, and beliefs about skill and time available to garden would be posed. These questions would be based on the logic model we developed earlier.

In the second step of program design, a person would use a pre-survey to measure attitudes toward the beliefs, intentions to garden, and garden behaviors.  An example of the hypothetical model is presented in Figure 4.

The answers derived from these questions would drive the next steps of the program design process; however, for example’s sake, we will build the remainder of the model based on conjecture. We will speculate that our results indicate that our target audience does not consider gardening a viable means of increasing vegetable accessibility because of the time involved. If this were the case, our program would need to be designed to target a person’s beliefs about the time needed for gardening and their perceptions of time usage and/or time management skills (see Figure 5).

 Ultimately, we would expect that the intention to garden would have increased and would follow up at a later date to see if the number of gardens created and maintained had increased.

It is important to note that the entirety of the program design proposed here is targets one method of increasing accessibility to vegetables (gardening). Achieving the long-term outcome articulated in the logic model above (improved dietary quality) requires a complex program design incorporating multiple, smaller “programs-within-a-program” approach.

What programs are you conducting that would fit with this model? Please post an idea in the comments box below.


Ajzen, I. (1985). From intentions to actions: A theory of planned behavior. In J. Kuhi & J. Beckmann (Eds.),  Action. Control: From cognition to behavior (pp. 11-39). Heidelberg: Springer.

Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, 179-211.

Ajzen, I. (2006). Behavioral interventions based on the theory of planned behavior.

Ajzen, I. (2011). Behavior interventions: Design and evaluation guided by the theory of planned behavior. In M. Mark, S. Donaldson, & B. Campbell (Eds.), Social Psychology and Evaluation. New York: Guilford Press.

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