War paint. Fashion statement. Tradition. Advertisement. Pulpit. That's why most athletes wear black grease, or stickers, under their eyes. The vague possibility of some anti-reflective capability helping to distinguish a speeding object while staring into light seems more a rationalization for routine than a true crack at a competitive advantage. What make us so confident? In 60-years of misplaced mascara there's been one peer-reviewed study, and a couple less esteemed, that even attempted to quantify the effect of the ritual. Funny thing is, the data shows it works. Well, sort of.