the behavior. Often, important beliefs affecting behavior are different for different
behaviors and different populations.
TRA, TPB, and IBM provide frameworks to guide research that can empirically
identify factors on which intervention efforts should focus. However, selection of specific beliefs to change through interventions must be done carefully. Targeting a few
beliefs may not be effective if they represent a small proportion of the total set of beliefs affecting intentions. Similarly, targeting beliefs that comprise a model component not strongly associated with behavioral intention may be ineffective. It is also
important to consider the effect of intervention messages on the entire set of beliefs
underlying behavior. An intervention communication may change one targeted belief
in the desired direction but could adversely affect other important beliefs. Further,
intervention development should pay attention to all model components simultaneously. For example, attempting to modify efficacy or control beliefs may be effective
only if a person is sufficiently motivated to perform the behavior in the first place.
Conversely, changing attitude may not result in behavior change if the person holds
strong control or self-efficacy beliefs about conditions that constrain the behavior.
It is important to assess the effect of interventions on the beliefs targeted and on
other components of the model. TRA, TPB, and IBM provide a basis to evaluate behavior change interventions because they lead to hypotheses about how an intervention targeting a set of beliefs will affect the model component to which those items
belong (for example, attitude) and thereby affect intention and behavior. The evaluation design should make it possible to measure model components as intermediate
outcomes, both before and after intervention, to assess how they are influenced by
the intervention and whether change in model components is associated with behavior change. These theories should be applied in conjunction with communication theories to design and deliver behavior change interventions. In this way, the IBM can
complement the use of other theories of change and thereby improve health behavior research and practice.