Driving through a tunnel effectively narrows our field of vision. The walls and ceiling restrict our view to only that which is inside the tunnel. It doesn’t matter if there’s a mountain parked on top of the roof, or an ocean of water being held back by the walls: when we’re inside the tunnel, those things are outside our view.
This concept of tunnel vision provides a good way to talk with your writing students about using first person point of view. This viewpoint is distressingly easy to mess up. When we’ve chosen to tell a story using the “I” voice, it’s all too simple to slip into another character’s head. But it’s a no-no to wander into a landscape that is beyond the “view” of the perspective character.
Sometimes it happens because the writer has been tempted to bring in information that the character doesn’t know, perhaps to increase tension or suspense (Will the snake the author has told us is hiding under the bed strike a fatal bite? Will she ever realize that he’s secretly attracted to her, as the reader knows because the writer snuck into his innermost thoughts?).
And sometimes it happens just as a slip: suddenly the writer has entered another character’s thoughts, or introduced action, that is outside the field of vision of the perspective character.
There’s a simple line I use to remind students that they can’t deviate from their character’s “tunnel vision” this way: in first person, the action has to stop whenever that character falls asleep, slips into a coma, or leaves the room.
The character can certainly come back into the room (or wake up from the coma) and guess that something has happened: they might read someone’s face and guess they’ve been crying, or see a broken vase and interpret that somebody threw it in a rage. But what happened inside that room after the character left is officially “outside the tunnel,” and therefore out of bounds of the character’s direct experience for storytelling purposes. If the writer wants what happened to be part of the story’s action, they have to find a clever way for the point of view character to discern what has gone on; they can’t simply sneak into somebody else’s head.
What happens outside the tunnel, stays outside the tunnel.