At the first (orientation) visit, participant will be asked about their feelings and moods, as well as their smoking status. Participant will fill out questionnaires on a computer and complete a breath test. The questionnaires will be about mood, stress, and smoking-related issues, and should take about 1 hour and 30 minutes to complete. To complete the breath test, participant will blow into a tube that's attached to a machine about the size of a pocket computer. The breath test is used to estimate the amount of tobacco smoke that participant inhales. Participant will also complete two computer-based tasks. Women who are pregnant should not take part in this study.