I once was demonstrating hypnosis before an introductory psychology class, and I asked for volunteers to be hypnotized. Two students and their teacher, who was not much older than they were, volunteered, all of whom happened to be female. As I began the induction, the teacher began to giggle, and this set off the other two.
When the giggling stopped and they had composed themselves, i began the induction once more. This time, the giggling was more intense when it broke out. I stopped, they composed themselves once more, and I began again. When the giggling broke out for the third time, it was so strong that the volunteers were rocking back and forth in their chairs,with laughter. I stopped the demonstration and the volunteers returned to their seats.
I had seen people "get the giggles" before on rare occasions as I was hypnotizing them individually, and I had always stopped after one or two attempts to continue, believing that it was a form of unconscious resistance. This time, with three volunteers involved, it seemed to me that we were seeing a miniature version of mass hysteria -- a form of psychological contagion which the teacher had communicated to her two students who had volunteered along with her.
Hyperempiria, or suggestion-enhanced experience, isn't just an alert hypnotic induction, as some people still believe. It's any form of experience which is enhanced by suggestion, and which occurs outside of a formal hypnotic induction :-- even becoming a victim of mass hysteria, as depicted in the following trailer from the 2015 motion picture, "The Falling," (The full motion picture is available on You Tube; and the director, Carol Morley, has published an excellent article in The Guardian which describes several historidal instances of mass hysteria.)