Thursday, June 23, 2011

The Theory of Planned Behavior, operationalized

This may seem rudimentary, but did you know that the Theory of Planned Behavior, a critical behavioral model for public health interventions, can actually be operationalized with mathematical measures?

Theory of Planned Behavior ... with math!

For those of you who aren't completely familiar with this model, I've included a diagram above. Now, I have always been a little wary of simplistic models such as this, because you have to wonder whether intention directly leads to behavior; however, I like that this model includes perceived behavioral control as a factor that influences behavior as well.

At any rate, when we consider this model, we're interested in measuring how attitudes, subjective norms, and perceived behavioral control influence intention, which in turn should influence behaviors. What do all of these terms mean?

Attitude: individual evaluation of a behavior. Operationalized (measured) by considering:
- personal beliefs that a behavior will result in a specific outcome
- evaluation of the outcome
- number of beliefs relevant to the behavior

Subjective norm: how society or environment contributes to behavior. Includes:
- probability that the subject believes the behavior is appropriate
- motivation to comply with this reference point
- number of reference points

Perceived behavioral control: the extent to which the individual believes he or she can control behavior. Includes:
- beliefs about whether factors that will affect the difficulty of the behavior
- perceived power of these factors
- number of factors

Yeah, I had no idea that this model was so ... scientific. It's hard sometimes to conceptualize these models as anything except the brainchild of some doctoral student in a think tank far, far away. And I really do wonder about their ability to predict behavior with such ease. There are so many variables that play into predictors of behavior ... I have to admit, a lot of the times I have intentions to change my behavior, but something prevents me from doing so. (Ex: I can NEVER seem to eat enough vegetables. Grrrr.) I am not 100% convinced that my inability to transfer my good intentions to behavior is a factor of only perceived behavioral control. I believe I can eat more vegetables. I really do.

Anyway, the point is that we need to critically evaluate these commonly accepted models. Although I admit I'm not an expert, I hesitate to just swallow these theoretical constructs that claim to distill human behavior to such simplistic terms. Also, the models' developers are often loath to disclose limitations that they might anticipate with their constructs ... did they honestly not forsee these problems, or were they hoping to fly under the radar, hoping other scientists wouldn't notice the models' inherent shortcomings?

I wouldn't put such nefarious measures past members of our scientific community, but when our entire understanding of human behavior is built on such shifting sands, it sure does humble a student in this field. Our comprehension of ourselves and the world around us is still so ... rudimentary. For all of our happy diagrams and well-articulated arguments, we really aren't close to understanding motivation, faith, or any other nebulous human attribute.

Without this fundamental knowledge, how are we expected to facilitate change?


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  2. This is Ijeoma Eze, a DNP student at california State University, Fullerton. Please, I intend to use the above image of theory of planned behavior for my doctoral project and I was wondering how to obtain the copyright permission. My email address: Looking forward to hearing from you. Thank you for your anticipated cooperation.l