The major goals of this study are 1) determination of the nature of the alcohol induced perceptual deficits in the driving situation, 2) an examination of the psychological processes underlying impaired perception, and 3) examination of interactions of such variables as age, sex, drinking history, etc. with alcohol effects. The research focuses on two aspects of driving: 1) the necessity to monitor several sources of information simultaneously (divided attention) and 2) the requirement to rapidly process this information in critical situations. Experimental techniques and methods include eye movement and fixation recording, and a series of measures of concentrated and divided attention as previously developed in studies of information processing. The study will utilize measures which have been demonstrated to be sensitive to low alcohol doses and to be relevant to man-machine performance. The study will attempt to identify the behavioral mechanisms which underly the impairment of information processing and attention by alcohol. Also, there will be examination with combined alcohol and marihuana treatments.