In Harry Potter and the Prisoner of Azkaban, Moony, Wormtail, Padfoot, and Prongs all speak to Severus Snape through the map when he caught Harry with it. Now "Prongs" (James Potter) is dead at the time this map is being read. Yet, he responds to Severus. Does that make the map some sort of Horcrux? Or is it just a bit of their collective consciousnesses, like one of Hogwarts's talking paintings. It would be very un-Maurauderlike to make a Horcrux, so the latter seems more likely. Which leads to the question- Did they know that the map could be used to mock people, even after the creators of it were dead?