Effects of a Specific Substance in Smokers

The study agent will be administered via beverages and/or a capsule. The substances used in the study are legal, non-prescription, and are proven safe for human consumption at the doses used. The study agent may be a depressant (such as alcohol), a stimulant (such as caffeine), or an analgesic (such as aspirin).

In the placebo conditions participants will consume beverages and capsules that contain no or very small quantities of the study agent.