How does our brain divide the day into different ‘chapters'?

The moment someone steps into a new environment – whether it’s walking into a restaurant, attending an event, or settling in to watch TV – the brain essentially starts a new “chapter” in their day. 

These mental shifts happen all day long, with the brain constantly dividing experiences into individual events that we can later understand and remember. 

But what exactly causes the brain to mark these moments as new “chapters”? This is what a new study published in the journal Current Biology set out to explore.

Mental chapters in the brain

The research was led by Christopher Baldassano, an associate professor of psychology at Columbia University, and Alexandra De Soares, a former member of his lab.

The team sought to understand what prompts the brain to form boundaries around experiences, organizing them as distinct events in our day. 

The researchers explored two main possibilities: one being that these mental chapters are triggered by big changes in our surroundings, such as moving from the outdoors into a restaurant. 

The other possibility is that our brain might be guided more by internal scripts based on past experience and goals, so even significant changes in the environment might be ignored if they aren’t relevant to our current focus.

Focus of the research

To test their hypothesis, the researchers created a set of 16 audio narratives, each about three to four minutes long. 

The stories took place in one of four locations (a restaurant, an airport, a grocery store, or a lecture hall) and dealt with one of four social situations (a breakup, a proposal, a business deal, and a romantic meeting).

Brain chapters shaped by focus

The researchers discovered that the way the brain organizes experiences into distinct events is shaped by what a person is currently focused on. 

For instance, when participants listened to a story about a marriage proposal at a restaurant, their prefrontal cortex typically grouped the story around the progression of the proposal, leading up to the hopeful “yes.” 

However, when participants were asked to focus on other aspects – such as the couple’s dinner orders – their brains began dividing the experience into new chapters based on those details.

The passive response of the brain 

“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,” Baldassano said. 

“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.”

Measuring chapters in the brain

The experts measured how the brain created these chapters by examining MRI scans to track brain activity, and by asking a separate group of participants to press a button when they felt a new part of the story had begun.

They found that depending on the perspective participants were told to adopt, the brain divided the story differently. 

For instance, a person listening to a breakup story at an airport might register new chapters when they passed through security or arrived at the gate if they were asked to focus on airport-specific details. 

But if their attention was directed toward the emotional side of the breakup, the brain might register new chapters based on the unfolding of the relationship. 

Similarly, in a story about a business deal happening in a grocery store, participants could either focus on the stages of the business deal or the steps of grocery shopping, which influenced what their brain perceived as new chapters.

Life experiences and memories

The researchers are also interested in how these shifting perspectives affect long-term memory. They asked participants to recall as much as they could about each story, and they are still analyzing that data to understand how different perspectives shape memory. 

More broadly, this study contributes to an ongoing effort to build a comprehensive theory of how real-life experiences are divided into event memories, suggesting that prior knowledge and expectations play a crucial role in how our brains organize and recall these events.

Meaningful stories and mathematical models 

For Baldassano, this project has been a rewarding journey. “Tracking activity patterns in the brain over time is a big challenge that requires using complex analysis tools,” he said. 

“Using meaningful stories and mathematical models to discover something new about cognition is exactly the kind of unconventional research in my lab that I am most proud of and excited about.”

The findings provide insight into the way the brain processes and organizes our experiences, highlighting that it’s not just changes in the external world that shape how we perceive new events, but also our internal focus, expectations, and goals.

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