In a modified "subject-paced" rather than fixed rate version of a rapid information processing (RIP) task, the presentation rate of the stimuli is continuously adapted to the individual performance level. Thus, this modified task version probably assesses a continuous "speed function" rather than mere "vigilance". In order to compare the two task versions more directly, we carried out a study which assessed the effects of a regular nicotine cigarette and the nearly nicotine-free cigarette NEXT on both task versions under the same experimental conditions. The dominant alpha frequency pointed to a greater arousal evoked by the subject-paced RIP version compared with the fixed rate version. With the fixed rate version, smoking nicotine cigarettes reduced reaction times, whereas with the subject-paced version, processing rate was improved. Additionally, smoking NEXT decreased craving less than smoking the regular cigarettes. It was concluded that the two task versions are sensitive to different cognitive functions. Whereas the subject-paced version was more sensitive to effects on the speed of processing, the fixed rate version was more sensitive to effects on reaction time.