Phase I end: redemption of rewards or adoption of deposit contract. The majority of participants will receive confirmation of their smoking status at the clinic within a few minutes of taking the test. Research staff will verify the confirmatory test result on stickK and assist participants as they adopt the deposit contract or redeem their rewards. The deposit contract is a commitment device that allows users to voluntarily "deposit" rewards that they can only recover if they succeed in achieving a predetermined goal, which, in this case, is maintaining smoking abstinence over the four-month Phase II period. In other words, participants who elect to use the deposit contract risk losing some or all of the rewards they accrued during the "rewards phase" if they fail to test negative for smoking at Phase II end.