There will be 3 lab sessions, during which you will be asked to complete questionnaires about your mood and feelings (about 30 minutes total). Also, you will give a breath sample by blowing air into a small tube. This sample shows how much you have smoked. In each session you will be asked to watch slides and listen to a series of tones through earphones. The slides will include pictures of people, nature scenes, and artwork. Slides showing victims of car crashes, medical procedures, and nude people will also be shown. You will be shown examples of these slides before beginning the procedure and given the opportunity to withdraw from the study. During the lab sessions, your heart rate, brain electrical activity (EEG), skin sweating, and muscle tension will be monitored. To do this, small sensors will be placed on the fingers, arms, scalp and face. You should not drink more than 2 cups of coffee or other caffeine drinks at least 2.5 hours before each session.