The Nuance

People in the radio business call them “buttons.” They’re those short music clips you hear in between news segments on NPR and other stations.

Bob Boilen, former director of NPR’s All Things Considered, once talked about these music interludes in an interview with the American Journalism Review. He called them “a breath in the show … a place to either think about something you just heard or get you to the next place.”

Boilen was on the money, maybe more so than he realized.

Since the publication of a landmark 1989 study in the Journal of Neuroscience, experts have recognized that the sleeping brain likes to run through its recent experiences and that this “replay” supports learning and memory. More recently, they figured out that replay also takes place while we’re awake.

When you experience something new and potentially useful — for example, you hear an interesting story on the radio — your brain will immediately replay this experience, at 20x speed.

This replay process is mostly unconscious and automatic. It takes place in the hippocampus, which is the part of your brain that sorts and stores information — turning new experiences into durable memories. One of the functions of replay is to strengthen your brain’s grip on new information, sort of like how repeating someone’s name just after you’ve heard it can help you remember it.

“Inundating the brain with a constant flow of information prevents this opportunity for replay, and thus will have detrimental effects on learning, memory, and decision-making.”

But that’s not all replay does. “Replay also reactivates related experiences,” says Shantanu Jadhav, PhD, an associate professor of psychology at Brandeis University in Massachusetts.

For a 2019 study in the journal Neuron, Jadhav and his colleagues found that replay involves an “internal cognitive search” of relevant memories. In other words, replay helps your brain sift through its collection of past experiences in order to better comprehend and contextualize new information.

Here’s an example: You bump into a neighbor, and the two of you have a chat. When you part ways, your brain will replay this new experience and also call up its recollections of your previous encounters. What you’ll end up with is more than a solitary memory; you’ll have a fuller mental model of your neighbor — one that will inform all of your future interactions.

Replay also supports your brain’s grasp of motor and spatial information.

A 2019 study in the Proceedings of the National Academies of Sciences found that hippocampal replay strengthened people’s ability to master a complicated button-pushing task. A lot more work has found that replay helps you remember how to get to and from places you’ve visited.

It’s not an exaggeration to say that the replay process undergirds all forms of learning and many aspects of behavior. Without it, your brain can’t do much with the information it encounters.

An overloaded brain is a confused brain — one that may be prone to lapses in memory, judgment, and emotion regulation.

But there’s a catch: Jadhav says that replay takes place during “downtime,” or those idle moments when your brain isn’t preoccupied with novel information. If your brain never gets those breaks, its replay functions suffer.

“Inundating the brain with a constant flow of information prevents this opportunity for replay, and thus will have detrimental effects on learning, memory, and decision-making,” he says.

The good news is that, if left alone, your mind tends to take replay breaks.

The bad news is that NPR and its music interludes are significant outliers in a media landscape that does its best to capture and hold your attention with a steady stream of stimulating content. There’s the “infinite scroll” design of most social media sites. And then there’s the way Netflix and YouTube try to propel you into a new show or clip the second you’ve finished watching something.

While these design features keep you “engaged” — good for these platforms — they don’t give your brain much time to sort, store, or make sense of what you’ve encountered. At the very least, this can lead to memory failures, especially for fine-grained details.

There may be more-significant downsides.

Some preliminary work in the journal Computers in Human Behavior has linked social media information overload to depressive symptoms and reduced overall well-being. More work has found that replay-related states — sleeping, downtime — may support hippocampal health in ways that strengthen emotional processing and counteract mood disorders.

The picture that emerges from all this work is that an overloaded brain is a confused brain — one that may be prone to lapses in memory, judgment, and emotion regulation.

The takeaway lesson is that your brain needs breathers — moments of distraction-free wandering interspersed throughout your day, and perhaps especially just after you’ve engaged with useful information. For example, if you’ve attended an important lecture, read a compelling article, or practiced your backhand, taking a few minutes afterward to zone out may help your brain make the best use of those experiences.

On the other hand, if you fill every idle moment with inbox checks or social media scrolling, your brain — and maybe also your mind — will pay a price for it.