During the performance phase, the 10-response order remained the same across sessions and subjects had 60 s to complete as many chains as possible. The primary dependent measures for this task were the number of chains completed, selleck the number of errors committed, and the percentage of correct responses. For the acquisition version of the task, the index of curvature for the number of errors committed was also calculated to determine how efficiently the 10-response order was acquired. Stimulant drug effects on repeated acquisition of response sequences (RA) task performance have been reported to vary as a function of sensation seeking status (Stoops et al., 2007). Digit�CSymbol Substitution Task Participants completed a 1.5-min computerized version of the Digit�CSymbol Substitution Task (DSST) adapted from McLeod, Griffiths, Bigelow, and Yingling (1982).

Trial completion rate and accuracy was monitored on this psychomotor task. Rapid Information Processing Task Participants completed a 5-min computerized version of the rapid information processing task (RIP) (Fillmore et al., 2005). At the start of this task, single digits were presented in the center of the monitor at a rate of 90 digits/min, and subjects were instructed to press a key whenever three consecutive even or odd digits were presented. Each digit was displayed on the screen for 67 ms with an ISI of 600 ms. Following correct responses, the speed of digit presentation was increased, and following incorrect responses or missed signals, the speed of digit presentation was decreased.

Information-processing capacity (working memory) was determined based on the rate of digit presentation and signal detection accuracy (proportion of hits). Tobacco Self-Administration Smoking Topography Measures Smoking topography measures during the 2-hr smoking period included number of cigarettes smoked, Batimastat puffs per cigarette, and total puff volume and duration. Participants also completed the Cigarette Rating Questionnaire (CQ; Westman, Levin, & Rose, 1992), which assesses tobacco smoke characteristics, including: good taste, calmed, awake, reduced hunger, irritability, nauseated, dizzy, reduced craving, and throat/chest sensations on 100-unit Visual Analog Scale (VAS). The CQ was administered twice, once after the experimental cigarette session and again after ad libitum smoking. Data Analysis Sensation-seeking group differences in demographic variables and CO levels were analyzed using independent t-tests. A preliminary analysis of the 24-hr deprivation period was conducted using a three-way mixed-model analysis of variance (ANOVA) with sensation-seeking status as a between-subjects factor, and test week (1�C3) and session (pre- and postdeprivation) as within-subject factors.