> Thank you, must admit I had wondered about the ghost thing too!
After we had our adult rescue dog for about a year, he started to growl & bark at things in the house, it really freaked us out. We couldn't see anything that he could be barking at, we were convinced it was ghosts.
We then discovered what it was - and realised he pays much more attention to deatails than us!!!
He was staring at the wall behind my head, really intently, then he started a low growl, walking forward like he was stalking, then he suddenly pounced past me at the wall as he tried to grab .......... the head of a nail that ws poking out of the wall!!!!!
He also would bark at the wall if he heard noises from the neighbours, it took a while for us to figure that one out as it was very faint noises he would start at. He would also not be happy if he caught sight of his relfection. New light fittings/shades, ornaments he hadn't taken notice of before etc.. were all other things he would bark at.
Dogs senses are much better than ours, it could be any number of things that is getting your dogs attention, I hope you figure it out soon, because it does get you thinking about ghosts!!!