smells being used as triggers...hmmm.... do ghosts even have a sence of smell??, lol..... if they are on another plane, just how much of our world do they or can they actually experience??.... sounds like a good idea maybe, but also sounds kinda gimmiky too... like something some of the reality TV groups might try, lol... this is also putting too much human (living) traits or abilities to a non human (living) entity... do ghost sleep? do they eat?... if so then a bigmac or alarm clock might work just as well...lol.... so much we don't know or can even begin to understand, (for me anyways...lol).... I would think that smells would have more of an effect on the living participants than on the non-living.... we still are affected subconsciously by smells without realizing it, due to not using the ability, but it is still there.....
