The cycle of conflict, mystery, and resolution is as old as storytelling itself, and at the heart of every good tale is variability. The unknown is fascinating and strong stories hold our attention by waiting to reveal what happens next. In a phenomenon called “experience-taking,” researchers have shown that people who read a story about a character actually feel what the protagonist is feeling. As we step into the character’s shoes we experience his or her motivations — including the search for rewards of the tribe, hunt, and self.

— Hooked: How to Build Habit-Forming Products by Nir Eyal