When we see billboards with negatively worded messages, we drive slower and tend to drift into the other lane, according to a new study out of the University of Alberta. When we see billboard messages with positive connotations, on the other hand, we tend to speed up. Our reaction time gets faster, too. Why is that? Well, it’s generally understood that people perform better when they’re in a happy mood. They look better, too. Keep that in mind while you’re cruising in the passing lane—just don’t forget to signal.