Perception Shift

A Perception Shift is a moment in which the audience's belief of understanding of something in the play changes due to a twist in plot or an unexpected revelation; Characters can also experience shifts in perception.

The most important part of a perception shift, either for the audience or for a character, is what causes that shift. There are plenty of ways of telegraphing information, either to the characters or to the audience. Many playwrights have a miraculous phone call where someone reveals what's really going on, or a messenger who arrives in the nick of time. These aren't necessarily the most fun things to watch.

What is more interesting to watch is a Conflict that escalates until a new piece of information bursts out of it. Maybe a character didn't want to have to say something, but she had no other choice. Maybe, because of the Conflict, a line was crossed that had never been crossed before. Whatever it is, there is a specific, physical moment that causes this shift, sometimes during the Climax.

As long as that link between the cause for the shift, and the shift itself, is clear, an audience will be right beside you as it happens.

Most well known plays have a character with a perception shift at some point throughout the play, if not a major one at the end. Macbeth learns the Witches fated him to die. The Capulets and the Montagues learn that their feud has killed two of their children.

Anything that could be considered a "spoiler" is probably a perception shift.