Participants were 32 non-treatment seeking adults (11 female) recruited from the community into two groups based on smoking status, hereafter termed moderate or heavy smokers (n = 16 per smoking group). Moderate smokers were required to smoke between 5 and 14 cigarettes per day and heavy smokers were required to smoke 15 to 24 cigarettes per day. Additional inclusion criteria included: (1) age between 18 and 55, and (2) no smoking abstinence lasting 3 months or more in the past year. Exclusion criteria were (1) currently taking psychoactive medications, (2) history of major psychiatric disorders, (3) current use of nonprescription drugs (other than alcohol and marijuana), and (4) if female, pregnant or planning to get pregnant.
