dont think anyone knows for sure - unless they can see ghosts too.
however I have heard that women and children are more prone to seeing ghosts than men due to men beleiving more in logic. Children especially because they wouldn't not see them if you know what I mean...
So in that respect I think dogs can because they just dont process information in the same way we humans/adults do...
My Dog barks at thin air. i think it is probably just that our dogs can hear something like a mouse under the floor (i'm not saying this is good!). Also if you get excited thinking your dog can see a ghost, your do will probably get excited aswell!
today when i was at my grandads house in the front bedroom wich used to be my nan and grandads bedroom untill she passed and i still had my dog on the lead and i nipped up yo get something frm that room and she wouldnt go in i tried to drag her in aswell but she just wouldnt budge and even when she isnt on the lead she will not come in the front bedroom :S:S spooky