A persons social and behavioral aspects when smoking

The primary reinforcing properties of nicotine ultimately sustain smoking behaviour: in experimental models, if nicotine is removed from cigarette smoke, or nicotine's effects on the central nervous system are blocked pharmacologically, smoking eventually ceases. However, under normal conditions, the intimate coupling of behavioural rituals and sensory aspects of smoking with nicotine uptake gives ample opportunities for secondary conditioning. For a 20 a day smoker, “puff by puff” delivery of nicotine to the brain is linked to the sight of the packet, the smell of the smoke, and the scratch in the throat some 70 000 times each year. This no doubt accounts for smokers' widespread concern that if they stopped smoking they would not know what to do with their hands, and for the ability of smoking related cues to evoke strong cravings.​ Social influences also operate to modulate nicotine's effects. The direction of this influence can be to discourage smoking—as, for example, with the cultural disapproval of smoking in some communities, the expectation of non-smoking that has become the norm in professional groups, or the effects of smoke-free policies in workplaces. Other factors encourage smoking, such as being married to a smoker or being part of social networks in socially disadvantaged groups, among whom prevalence is so high as to constitute a norm. Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC324461/