 Experiments in this protocol employ fMRI to address the interactions of nicotine with such cognitive processes as working memory, attention, and the executive functions of inhibitory control, conceptual reasoning and attention switching, in addition to reward and temporal error reward processing. The effects of nicotine on these cognitive processes will also be assessed outside the MRI scanner. Assessments of genetic variants will be done with the hypothesis that these will account for some inter-individual differences in the brain imaging data. 