In an ideal world, people would adopt a positive attitude toward a healthy lifestyle as a result of carefully considering relevant and strong arguments. Attitudes based upon such considerations are believed to be stable and good predictors of related behavior, and less vulnerable to counterattitudinal messages. However, carefully evaluating arguments in such messages is difficult. First, people need to identify what information can serve as an argument and construe the argumentative relation between the information and the advocated claim. Next, they need to assess the extent to which the argument satisfies the criteria for a strong argument. What these criteria are depends on the type of argument at hand: an argument from analogy, for instance, should be evaluated with different criteria than an argument from authority. Argument scrutiny thus entails reconstruction, identification, and evaluation.
The good news is that even though argument scrutiny is a complex task, it seems that people are pretty well equipped to carry it out. Meta-analyses have shown that messages containing strong arguments are more persuasive than those containing weak arguments. In addition, there is evidence that people are sensitive to what extent a specific argument satisfies relevant criteria when evaluating arguments. The bad news is that people may use these skills not so much to make objective evaluations to reach a better decision, but rather to defend the type of behavior that they already feel they want to perform. That is, they use their argument evaluation skills to reason why the arguments in support of the behavior that they favor are stronger than the arguments against that behavior.