I know it sounds like a joke, but it's not. According to a research by Steven Most of the Yale University, when you look to a smutty picture you will suffer of "emotion-induced blindness". The news is reported on The Economist which indirectly suggests this finding might affect billboard advertising, since Dr Most made this discovery while studying the rubbernecking effect (when people slow down to stare at a car accident). According to the research, the lapse of attention to the road (temporary blindness) lasts between two-tenths and eight-tenths of a second, which "is long enough for a driver transfixed by an erotic advert on a billboard to cause an accident".