I think it would have to be "Storytelling". Yet storytelling has to be the oldest most basic thing known to mankind evolving with the creation of language and basic communication.
"Stay out of the cave OG, it bad in there!"
"How bad?"
"Rip you apart, eat you slowly,smells bad in there too."
"What beast lives in there, bear? Cougar? Something unseeable?"
"No, much worse than any or all of them, I call it Mywoman."

Last night what happened in my first room was pretty incredible. All house-virgins, a group of small children, teens and adults, yes I do have the wonderfully perculair advantage of my 1870 house stimulating their imaginations before they ever get out of the car.
My first room is odd, old, strange artwork (mine of course) so as I tell them about the haunted history of this old inn- schoolhouse- bordello they become engrossed in the outcome of the experince and time spent here.
Then as one teen girl was doing some question asking and adding a few remarks of her own she questioned as to how I could be a real, living person?
I slowly blocked more and more of the light coming out of my flashlight with my thumb as I said, "Now... you know.. I'm not exactly "alive".
Total darkness took the room as three teenagers who were their own group and six adults, small kids and teenagers were also their own group all vocally accellerated a sort of moan into a scream as they could tell I was moving toward them (just a small step or two) in this wonderfull yet so inexpensive, "dark".
I released the struggling beam of light from my flashlight to find the tall, thin, teenage boy had fists clenched, ready to punch "Jim the Ghost". (Even though swinging with a punch as you are sitting is usually fairly lame.)
"And what would happen if you punched a ghost?" I had to ask him.
He was to express very quick, loud curses with very little scary stimulation upon numerous ocassions, so much so that the little girls he didn't know began calling him "Pussy", then his 4 yr. old brother learned that new word and repeated it much to the dismay of his parents. (Of course everyone seemed to be very fast with the "F" word as immeadiate faux-danger overwhelmed them at every turn.)
IT all began with mere "words", storytelling.
I can tell a very convincing "Story" I have had much practise , but then maybe most seem to believe those strange tales I tell because I believe them.. because, yes, they are true and have happened.
"Life is strange, if you take the time to notice."