Understanding Nicotine and Tobacco Addiction (Novartis Foundation Symposia)Cigarette smoking is estimated to lead to 4. 9 million premature deaths per year worldwide. This is predicted to rise to 10 million by 2020. In western countries it kills half of all smokers who fail to stop. The prevailing model for tobacco addiction is that nicotine from cigarettes rewards smoking and punishes abstinence, tapping into a motivational system of operant conditioning that requires no conscious awareness. However, there are also accounts