A scary story in which a storyteller makes effective use of a dramatic pause followed by a sudden, loud outburst to get the audience to "jump" out of their seats, thanks to the mammalian auditory startle reflex --the human brain's auditory lobes, reflexively attuned to sudden changes in sound ("Boo!"), triggers the amygdala and circuits of the reticulospinal tract to activate the startle. Our cochlear root neurons probably have something to do with it, too.

The story may be about ghosts, or vampires, or bloody corpses, but it's not necessary-- case in point, I've heard a Brazilian storyteller tell a "four jump" story-- his translator told us he would make us jump four times. And sure enough, though the story was about werewolves, he told it entirely in Portuguese, so we in the English speaking audience couldn't follow the plot directly. Nevertheless, even with advance warning, through his cunning use of eye contact, vocal effects, and the dramatic pause-- we jumped.

Classic American jump stories heard on the playground, around the campfire, and at slumber parties:

Want more? Check out Alvin Schwartz's Scary Stories to Tell in the Dark (New York : Lippincott; New York : HarperTrophy, 1981)

--Clemens, Samuel, as Mark Twain. How to Tell a Story and Other Essays (New York: Harper & Brothers, 1897)
--Davis, Michael, "Neural Circuitry and Neurotransmitters That Mediate the Acoustic Startle Reflex," paper presented at 138th ASA Meeting, Acoustical Society of America, Columbus, Ohio, November 3, 1999; http://acoustics.org/pressroom/httpdocs/138th/davis.htm
--Givens, David B. "Startle Reflex" in The Nonverbal Dictionary of Gestures, Signs, and Body Language Cues, http://members.aol.com/doder1/startle1.htm (Accessed Sept. 28, 2001) See also: http://www.nonverbal-dictionary.org/2013/01/startle-reflex.html
--Ramos, Roberto Carlos, "Storytelling as a Tool in the Education of Marginalized Children," translated by Livia de Almeida, National Storytelling Conference, University of San Diego, July 1999