During the act of reading engaging fiction, we can lose all sense of time. By the final chapter of the right book, we feel changed in our own lives, even if what we’ve read is entirely made up.

Research says that’s because while you’re engaged in fiction—unlike nonfiction—you’re given a safe arena to experience emotions without the need for self-protection. Since the events you’re reading about do not follow you into your own life, you can feel strong emotions freely.

The key metric the researchers used is “emotionally transported,” or how deeply connected we are to the story. Previous research has shown that when we read stories about people experiencing specific emotions or events it triggers activity in our brains as if we were right there in the thick of the action.