Dogs See Ghosts, Right?

I currently live in a house with a housemate that has a bulldog. The house isn't that old - perhaps 20 years or so and is located in Washington State. Sometimes when my housemate and I are sitting in the family room we hear noises - such as creaking floors, bumps and creeks - coming from the kitchen. Usually, right before then, the bulldog will begin to growl and bark at - nothing. Dogs see ghosts, right? Am I the only one who has noticed how sometimes a dog will track and follow something in a room (other than its butt) - yet we are unable to see whatever it is?

My housemate and I have investigated what might be the cause of the noises and why they only seem to happen at around the same time each night. We have a free-standing refrigerator in the kitchen so we investigated to see if perhaps the creeks were occurring when the frig turned on, but no - that wasn't it. We also checked the dining room to see if perhaps there was something in the dining room that would create the noises. No, that wasn't it, either.

One night, we heard a very distinct sound - someone stepping on a certain spot in the kitchen. We know because the floor creeks in that spot when you walk on it. Just for a minute, I know I turned around to speak to whomever it was...just for a moment forgetting that only my housemate and I were in the house. The dog went nuts! He went around the kitchen table, continuing to look at that spot in the kitchen and growling and barking. We don't experience this phenomena in any other part of the house and again, it only seems to occur at certain times of the night. So, I ask you - dogs must see ghosts, right?