Can Anyone Solve This Difficult Logic puzzle?

Ok, so theres 3 perfect logitians in a room. A man steps into the room and shows them he has 2 black hats and 3 white hats. He turns off the lights, and places one hat on each of the logitians heads. (note that the logit tians can only see the hats on the other peoples heads.) The man then turns on the light and tells them that if they KNOW that they have a white hat on, then they should leave the room when the light turns off. He says he will turn the lights on and off several times. after the lights go off twice, none of the three perfect logitians have left, but on the third time the lights go off, all three men leave. Why?

Logitians* (in the parenthisies)