The control (CN) participants were recruited through advertisements and compensated for their time, and none of them reported a history of head injury, psychiatric disorders or substance dependence (other than cigarette smoking). Only male participants were selected as gender effect was not a focus of this study. Both cohorts of HU and CN were current tobacco users. The HU and CN were matched in age (HU, 30.1 ± 5.3 years, range from 22 to 39 years; CN, 29.8 ± 7.2 years, range from 20 to 39 years; t(25) = 0.093, ns) and years of education (HU, 9.71 ± 2.7, range from 5 to 14; CN, 10.8 ± 1.6, range from 8 to 13; t(25) = −1.296, ns). After complete description of the study to the participants, written informed consent was obtained from them for their involvement in this study in accordance with the review board of University of Science & Technology of China.
