tive, that is, guidelines for acceptable behavior associated with sociocultural values. Norms are maintained both by social reinforcements and social sanctions. A social learning analysis of tobacco use takes into account the different types of social reinforcement that coincide with the development of tobacco use from experimentation to initiation to maintenance of regular use. Experimentation typically occurs under conditions of peer reinforcement; usually the initial inhalation of smoke is aversive but eventually the youth develops a tolerance to it. In other words, the adolescent "learns" in a peer context that tobacco use is an acceptable or desirable behavior, despite initial negative physiological reactions. Continued use produces pharmacologic reinforcement to sustain the behavior independent of social reinforcement. The behavior then occurs in different situations, where new learning takes place. The young smoker discriminates between situations in which smoking is socially acceptable or unacceptable. At the same time, various environmental or situational cues, such as an ashtray, or an empty cigarette pack, or a party, not only can suggest acceptability but can also stimulate physiological responses that reinforce the addiction to nicotine.1 Hence, whereas the addictive power of nicotine drives a person to use tobacco regularly and to maintain that regular use, it is the power of these perceived social norms that persuades children and youths to experiment with and initiate use of tobacco.
The development of these perceived norms among children and youths is influenced by pervasive images and messages of everyday life. These messages come from numerous sources: friends, peers, family, school, the workplace, church, films, magazines, radio and television, billboards, electronic media, advertisements, sports events, arts performances, and so on. These messages typically have a prescriptive influence on social norms; in other words, in addition to characterizing what members of society do, they suggest to people what they should do. As standards set by a society or social group, norms define the boundaries of behavior; they dictate etiquette, protocol, and a sense of what is normal, natural, expected, and acceptable in given contexts. Because the norms of society are in large part prescribed through public sources, they are subject to the influence of interest groups that seek to legitimize an agenda and to engineer behavior.
Social groups are influenced by, but do not passively accept, prescribed norms. They mark their identity by selectively adopting and appropriating behaviors and images that take on meaning in opposition to behaviors and images adopted by other groups. Markers of group identity and conventions of group membership are not fixed, but rather change over time. Images associated with tobacco use are not stable, if not reinforced.
For adolescents, norms are particularly complex, for two reasons. First, adolescence is a transitional period "shaped by prior development in childhood and the future requirements of adulthood, as well as by current expectations and opportunities."2 Second, adolescence itself is a complex developmental period,