diverse channels may convey the meta-message that society cares about this health issue. Similarly, repeated exposure to a message in multiple channels may increase the probability of interpersonal discussion of the message, further multiplying exposure and diffusion of a communication message. Finally, repeated message exposure carries with it an implicit legitimization of the subject of the health message. It also may increase the likelihood of policy attention to the problem. Issues given high exposure often interest politicians.
The previous discussion sets the stage for considering media effects. It is often assumed that a portion of the target audience will be exposed to a given message, and that a portion of those exposed to the message will learn its contents and change their health behavior. For example, consider again adolescent initiation of marijuana use. A health communication message might focus on the belief that beginning marijuana use will damage relationships with parents. We might hypothesize that youth watching the marijuana use ad immediately form (or strengthen) their belief, and as a result of this belief change, some youth may reduce their intention to use or their actual use of marijuana. Communication also can affect one’s beliefs (and behaviors) in other ways. For example, rather than having an immediate direct effect on beliefs, there may be a time lag between exposure to the message and belief (and/or behavior) change. In addition, rather than being directly exposed to a message, one may be indirectly exposed to the contents of the message through interpersonal interaction. Equally important, messages directed toward a specific belief or behavior may generalize to other beliefs or health behavior changes.
Five different paths through which a health communication message may have an effect on target beliefs (and behaviors) are: (1) immediate learning, (2) delayed learning, (3) generalized learning, (4) social diffusion, and (5) institutional diffusion.
Immediate learning. People can learn directly from health communication messages that enable them to make different decisions. For example, youth learn that trying marijuana has negative