Tom is trying to quit smoking. His parents, siblings, wife, children, and his doctor have all emphasized to him how important it is for him to quit. According to the theory of planned behavior, what factor is most likely to interfere with Tom's forming a firm behavioral intention to quit?

In the theory of planned behavior one acts rationally, using information that one knows and the outcome of one's actions in deciding whether or not to act in any way. Beliefs are a way for humans to gather convincing information and opinions to establish their behavior. In the case of Tom, his family and doctor are encouraging him to quit, based on which Tom will most likely intend to quit smoking through normative belief, which is a result of social pressure. The encouraging attitudes of his family and doctor are favorable to Tom, so he is more likely to perform the behavior they request.