Paranormal activity is a pretty broad term.
Ghosts? Probably not but I'm smart enough to know that I don't know everything. Besides, "ghosts" don't need to be undead spirits.
Aliens? More likely in my opinion, the idea that aliens could and would travel to our planet seems unlikely to be but the existence of aliens, even highly intelligent ones is highly probable given the size of the universe.
If it helps you understand what kind of a person I am any better, I grew up with Sci-Fi and have watched the entire runs of The X Files, Star Treks DS9 and Voyager (as well as most of TNG), Babylon 5, Stargate SG-1 (working on Atlantis at the moment), and bits of Andromeda, Doctor Who, Earth: Final Conflict, Sliders, and various other shows. In other words, I'm a sci-fi fan.