I am of the opinion that there is really no way to prove this either way, not in any scientific sense, but that one's intuition says whether or not something is just a part of the mind or if it may stem from the environment. I have had strange dreams while sleeping in inhospitable places involving hostile people that were only a few doors down and I am convinced that parts of their animosity might have been picked up by my sleeping mind. Whether or not they actually entered my dream is doubtful [and also somewhat not that important] but I do believe that the energy was coming from somewhere - though this brings up questions of range and so on.