 Research suggests that AAs, who smoke fewer CPD but take in more nicotine per cigarette, are behaving like peak-seekers smoking primarily for the direct nicotine-mediated positive reinforcement. In contrast, whites, who smoke more CPD with less nicotine intake per cigarette, are behaving more like trough-maintainers seeking to maintain consistent nicotine levels through the day, presumably to avoid withdrawal symptoms andor to desensitize receptors. 