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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Addiction. 2016 Jan 23;111(5):903–912. doi: 10.1111/add.13264

Figure 2.

Figure 2

Percent of participants abstinent as a function of intake (Visit 0) and subsequent study visits (Visits 1–33). During Phase 1, participants provided breath CO and urinary cotinine specimens daily and earned voucher-based incentives contingent on smoking abstinence. During Phase 2, participants were randomized to either a group that continued to receive abstinent-contingent incentives (Extended Contingent) or a group that received incentives independent of smoking status (Extended Noncontingent). Abstinence at Study Visits 1-5 was defined as a breath CO ≤ 6ppm; starting at Visit 6, it was defined using the more sensitive measure of urine cotinine ≤ 80ng/ml and this remained in place for the remainder of the study. Data are presented for Extended Contingent (filled symbols) and Extended Noncontingent (open symbols) groups, with asterisks indicating a significant difference between experimental conditions at that study visit.