tion (or other type of intervention). First, in the population under consideration, the belief should be strongly related to the intention or health behavior to be changed. Second, there should be enough people who do not already hold the targeted belief to warrant trying to change it. An example would be the belief that “My smoking is harmful to my health.” Because this belief is widely held by smokers as well as nonsmokers, little will be accomplished by trying to change it. Thus one must consider whether a communication intervention designed to change a given belief has the potential of moving enough people to make the intervention worthwhile. Finally, one must consider whether changing the belief is even possible. That is, can one support the targeted belief with a plausible argument based on strong evidence?

Relationship with Intentions and Behaviors

Clearly, with respect to the first criterion, theory-based survey data can identify beliefs that discriminate between intenders and nonintenders or that are highly related to the intention or behavior one wishes to change.

How Many People Already Hold the Targeted Belief?

Even though a belief may be highly related to the intention and behavior one wishes to change, little will be accomplished if most people already strongly hold the belief in question. It is important to recognize, however, that beliefs are not “held” versus “not held,” but vary in degree of strength. For example, people may “strongly agree” (think it is “extremely likely”) or “agree” (think it is “quite likely”) that a given behavior will lead to a given outcome. Clearly, if 80 percent of those who “strongly agree” but only 20 percent of those who “agree” have strong intentions to perform the behavior in question, then strengthening this belief is an appropriate target for an intervention. Thus, it is important to consider “belief strength” and to determine whether strengthening existing beliefs (i.e., moving people from “quite likely” to “ex-

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