The influence of alcohol and sleep deprivation on stimulus evaluation.

The effects of alcohol and sleep deprivation on choice reaction time (RT) as a function of stimulus intensity, stimulus quality, and response compatibility were investigated. Fifty-four male subjects were assigned to one of three levels of alcohol (0.00, 0.07, or 0.10 BAC), and one of two levels of sleep deprivation (0 or 24 h). Stimulus intensity, stimulus quality, and response compatibility were varied (high or low), with RTs identified according to time on task. Significant main effects of each of the stimulus variables were present in baseline analysis, with low-level conditions producing longer RTs. Alcohol produced an overall slowing of RT. The combination of both treatments led to larger increases in RT for low stimulus quality. Sleep deprivation increased RT for high stimulus intensity. Alcohol increased RT for low stimulus intensity, but only when subjects were not sleep deprived. These results imply higher risk with degraded stimulus conditions, e.g., driving in settings of low visibility or at night.