Most of us know that a few beers impair decision making, but a sleepless night could be just as bad for your brain. That's the suggestion from a study of students in Arkansas who were asked to judge the motivations of the women in hypothetical situations. When the students were kept up all night and given the survey again, the men perceived the women as being more sexually interested – and were more likely to act on the misperception. "Men are not as good at making decisions when they're sleepy," says study co-author and psychologist Jennifer Peszka. Sleep debt and alcohol both impact the performance of the brain's frontal lobe (a night without sleep is equivalent to 0.1 blood-alcohol level), where we process variables and data, and make interpretations and decisions. "We need to be aware that when we're sleep-deprived we may interpret things differently," Peszka says. "If we're aware we can at least make adjustments."