Mice, taken collectively, are not very good at escaping from a crowded room. They act pretty much as humans do, namely they all crowd toward the door and few get out very quickly. Each individual mouse appears to make a rational calculation of a sort. The mice do best, and adopt some form of queuing behavior, when the door is large enough to let only one mouse through at a time. Researchers suggest that humans may exit a crowded more quickly, the smaller the door, which limits the crush toward the exit. For more information read this article from New Scientist.