Participants in the present study achieved somewhat higher peak alcohol exposure compared to prior CASE studies, in which BrAC ranged from 70–80mg% in the context of 100mg% (Zimmermann et al., 2008) and 120mg% (Zimmermann et al., 2009) safety ceilings. These differences likely reflect recruitment of heavier drinkers in the current study; for instance, mean AUDIT scores in this sample were considerably higher than in a prior study of young adults (Zimmermann et al., 2009). However, it is notable that initial CASE studies are consistent in showing considerably higher BrAC levels under free-access intravenous self-administration compared with oral self-administration. A review of oral self-administration studies reported average consumption in the range of .45 – .51g/kg, corresponding with peak BrAC levels of 40–50mg%, notwithstanding the inclusion of alcohol-dependent participants in some studies (Zimmermann et al., 2013). Higher alcohol exposure in intravenous studies could reflect differential demand characteristics, greater uncertainty of the quantity of alcohol consumed, differences in operant paradigms across studies, or undetermined factors (Zimmermann et al., 2008, 2013). Importantly, differences in behavior across paradigms could have implications for detecting genetic influences
