Beyond the obvious convenience factor of listening on the go, what is it that makes some audio storytelling so engaging? And what happens in the brain when someone hears a really compelling story?

“A good story’s a good story from the brain’s perspective, whether it’s audio or video or text. It’s the same kind of activation in the brain,” says Paul Zak, the director of the Center for Neuroeconomics Studies at Claremont Graduate University. Zak has studied how watching and listening to stories influence our physiology and behavior.

In a study published in The Annals of the New York Academy of Science in 2009, Zak and his colleagues had participants watch short video clips featuring an emotional or unemotional scene. Afterwards, they filled out a survey about their emotions, played a game designed to test their level of generosity toward a stranger, and had their blood drawn. Those who reported feeling empathy for the characters in the clip were found to have 47 percent more of the neurochemical oxytocin in their body than those who didn’t feel empathetic toward the characters.

The researchers reason that experiencing tension in a story makes people feel stressed, which makes their bodies release the hormone and neurotransmitter oxytocin. Since oxytocin has been shown to increase empathy in some experiments, when things get tense while listening to a story, reading a book, or watching a TV show or movie, you may begin to empathize with the characters and get “transported” into the story.

Which means, according to Zak, that the best stories will always have an increasing level of tension, and that there exists a type of universal story structure—one in which a protagonist faces some sort of stressful challenge or conflict—that draws attention because it’s engaging emotionally and intellectually.

“What we have found in our research is that people require some sort of stressor, some sort of arousal response in the brain to have this type of narrative transportation where we begin to share the emotions of the characters in a story,” Zak says. “It makes sense that we need some sufficient reason to have that response. Our brain is trying to save resources and energy and having this arousal response is costly. Therefore we only want to give attention to something when it matters, when there’s something going on.”

He describes transporting into a story as a “neuro ballet” in which the reader, viewer, or listener knows she's not physically part of the story, and yet she still physically responds to it in a way that can change her behavior in the future.

Since oxytocin has been shown to make people more sensitive to social cues, Zak says that stories that keep people’s attention have to be character-driven. “You can tell a war story or something with a lot of action that will grab your attention,” he says, “but you still need a personal story, someone to empathize with. We need to have that social aspect for it to resonate with us.”