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Sherene Fernando, Fahrin Rawji, Alexandra Major, Brian Timney; The Effects of Acute Alcohol Consumption on the Visual Perception of Velocity and Direction. Journal of Vision 2010;10(7):460. doi: 10.1167/10.7.460.
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The effects of alcohol on velocity and direction discrimination were examined. Participants completed both tasks under control and alcohol conditions (.08% BAC) conducted at both a “slow” (3os-1) and “fast” velocity (12os-1). Stimuli were dark dots on a light background that could vary in speed or direction. They were presented within a 5° circular field on a computer display spanning 12° × 16° in visual angle. Thresholds were measured using a Method of Constant Stimuli and a 2-interval AFC. In the velocity condition, one stimulus was always moving at the standard speed and the other, comparison, stimulus varied over a range of 85-115% of the standard velocity. Participants made judgments as to which moved faster. Using the same procedure, participants in the direction task judged which of the two drifting patterns was moving vertically. The standard was always vertical, while the comparison stimuli ranged from 0.5 to 3.5° to the right of the vertical plane. As expected, results of the velocity task demonstrated a small but significant effect of alcohol, demonstrating impairment in the general ability to accurately discriminate stimulus velocity. In the direction discrimination condition, performance was impaired at both velocities, but for the slower speed, the initial range of directions used resulted in a floor effect, with performance at chance for both the alcohol and no alcohol conditions. There was a significant effect of alcohol for the higher velocity pattern. We conclude that, overall, alcohol has a modest effect on the ability to discriminate both the velocity and the direction of moving targets.
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