How did they know?

How could they know? How can there be a sign telling you that you are going the wrong way? Isn't every way somehow also a right way?


Okay... now I get it! They come in pairs on campus. After every "Do not enter" sign there is a sign for those who did enter a one way road the wrong way to tell them they are going the wrong way.
Except - Now I'm still trying to figure out how this goes together with the whole "the brightest minds in the world"-thingie.