I've had a very weird experience with Jax one day.. My boyfriend and I were sitting on my bed watching TV and right at the very same time the space heater in my room turned on and the TV changed to channel 3 on its own. I didn't think anything of it because I figured it was some kind of power surge or glitch. Soon after my boyfriend left for work and I grabbed Jax to come lay in bed with me. As soon as we got in my room Jax got all stiff in my arms and started growling. I put him down on my bed and knelt against the bed. He would lean as close and he could against me and act all scared for awhile. He wouldn't even move. I then took him off the bed and set him on the floor. He then began barking and growling at something and he would stretch his little body as far as he could without moving or leaving my side to bark and growl some more. I decided I was just gonna watch TV in the living room after that. lol
I believe dogs can sense spirits and unknown stuff like that. In fact, one of the ghost hunter shows I just started watching on TV was advertising for another episode they were going to show where dogs were acting strange and sensing stuff.