Life can feel like a novel some days, full of romance and mystery, and perhaps a touch of horror or even a little fantasy. So perhaps it comes as little surprise that the human brain keeps track of narratives in discrete chunks not unlike the chapters of a book.
A study by researchers at Columbia University in the US builds on what we already know about this 'chapterization' of our lives, confirming new sections are marked with a noticeable change in brain activity as we move from place to place or activity to activity.
Segmentation clearly helps the brain make sense of the ongoing stream of life, though it hasn't been clear until now exactly how the brain decides where to start and end each chapter.
The new research reveals a personalized process, based on what's important to us and what our priorities are.
"We wanted to challenge the theory that the sudden shifts in brain activity when we start a new chapter of our day are only being caused by sudden shifts in the world – that the brain isn't really doing anything interesting when it creates new chapters, it's just responding passively to a change in sensory inputs," says Christopher Baldassano, an associate professor of psychology at Columbia University.
"Our research found that isn't the case: the brain is, in fact, actively organizing our life experiences into chunks that are meaningful to us."
In other words, moving from the bus station to the coffee shop might not necessarily trigger a new chapter if we're keeping track of a conversation between those locations.
The research team put together 16 short audio narratives that featured one of four locations (a restaurant, an airport, a grocery store, and a lecture hall) with one of four scenarios (a breakup, a proposal, a business deal, and a meet cute).
A total of 415 participants were invited to listen to these narratives. In some cases their brain activity was monitored, while in others the volunteers were asked to indicate when a new part of the story started by pushing a button.
Crucially, in some cases the researchers primed the participants to concentrate on different aspects of the study – so in a story about a marriage proposal at a restaurant, they might be asked to focus on the proposal, or the food orders.
The priming had an effect on the neurological defining of new chapters, showing that the brain adjusts its organizing techniques based on what we think is most significant at the time. Our current priorities and goals, as well as past experiences, can all play a role.
Next, the researchers want to see how expectations about what will happen next influence our chapter recordings, and which parts of our experience get logged in memory. There's a lot more to explore.
"These results identify mechanisms by which past experiences, distilled into schematic event scripts, change the way that we construct our present perceptions for realistic experience," write the researchers in their published paper.
The research has been published in Current Biology.