Dr. Joseph Jebelli is a neuroscientist and writer. Of his previous books, In Pursuit of Memory was shortlisted for the Royal Society Trivedi Science Book Prize and longlisted for the Wellcome Book Prize.
What’s the big idea?
Your brain’s default network is the most important part of your brain that you have probably never heard about. It is critical for maintaining intelligence, creativity, memory, and so much more. The key to a healthy default network? Rest. Productivity and success that doesn’t burnout or deteriorate depends on granting ourselves ample time for quality rest rituals.
Below, Joseph shares five key insights from his new book, The Brain at Rest: How the Art and Science of Doing Nothing Can Improve Your Life. Listen to the audio version—read by Joseph himself—below, or in the Next Big Idea App.
1. Overwork is literally killing us.
There is a global pandemic quietly being ignored by governments everywhere, which I call the work pandemic. I call it a pandemic because it is literally killing a huge number of us. The statistics of overwork are grim.
Globally, overwork causes 745,000 deaths a year, a 29 percent increase since 2000. Three in five employees now report a lack of interest, motivation, and energy, a 38 percent increase since 2019. Japanese language even has a word for working to death: karoshi, which is estimated to cause 20,000 deaths a year in Japan.
In the brain, overwork thins the frontal cortex in the same way that aging does, meaning it literally makes the brain older than it is. Like a forest gradually disappearing, your neurons lose the branch-like structures known as dendrites, which, once gone, are incredibly hard to recover. The frontal cortex is also the brain region responsible for good judgment and an awareness of long- term consequences, making it the only region that could advise a person against working too hard.
Economically, our culture of overwork cost Britain’s economy £20.7 billion in 2022, and this figure is set to escalate rapidly in the coming years. The estimated cost to the global economy for mental-health issues, such as depression and anxiety, is $1 trillion a year, forecast to reach $16 trillion by 2030—a sum that would fund universal healthcare in all low- and middle-income countries three times over.
While it’s true that working conditions are better than in the past, the inescapable fact is that we are in a dramatic regression in terms of burnout and overwork.
2. Rest is the key to sustained productivity.
We live in a world obsessed with work and short-term productivity. We’re constantly told that to be happy, creative, and successful, we need discipline and focus. But neuroscience shows that rest, not work, is the secret to sustained productivity.
When you rest, your brain activates the default network. This is the most important part of your brain that you’ve probably never heard of. The default network is a circuit of neurons that fans out across your brain and allows you to think in completely new ways. It occupies four main brain regions: the medial prefrontal cortex (just behind your forehead, beneath the brain’s surface), the posterior cingulate cortex (in the middle of your brain), the precuneus (at the top of your brain, toward the back) and the angular gyrus (near the back of your head, just above your ears).
When you activate your default network with rest, you improve your intelligence, creativity, memory, problem-solving abilities, emotional processing, and so much more. It can even reduce the risk of developing neurological illnesses, including depression and dementia.
“A mountain of new research shows that, as a general rule, the more time you spend doing nothing, the better it is for your brain.”
How can rest, the act of seemingly doing nothing, have such incredible neurological benefits? Well, we’ve known for a while that blood flow in the frontal lobe (responsible for nearly all our higher faculties, including intelligence, memory, and attention) is at its highest when a person is resting, not working. For decades, neuroscientists ignored what the brain is doing when we rest. They were so focused on what the brain is doing when we perform a task, they thought of this resting brain activity as meaningless background noise.
But in the last few years, it has become increasingly evident that engaging in a task dampens the brain, like a dimmer switch turned all the way down, while disengaging from a task stimulates the brain, like a dimmer switch turned all the way up. How can doing nothing require more energy than doing something? It’s as counterintuitive as braking on a bicycle to speed up and pedalling to slow down.
A mountain of new research shows that, as a general rule, the more time you spend doing nothing, the better it is for your brain. Whether you’re a doctor, a train driver, a student—whatever task you’re doing—you will perform better if you rest beforehand, precisely because you are activating your brain’s default network. This new neuroscience is teaching us that people often succeed in life not despite their inactivity but because of it.
3. Napping has a much bigger impact on brain health than we ever imagined.
We’ve known for a while that sleep is a time of strong default network activity. But what’s come as a surprise is the finding, in 2023, that people who take a 30-minute daytime nap literally have bigger brains than those who power through the day.
The difference is significant: nappers’ brains are 15 cm3 larger than non-nappers’ brains—the volume of a small plum. Think about the millions of neurons and synapses in that space, and all the cognitive potential we’re losing by not taking that essential 30-minute nap every day. And there’s more: that 30-minute nap has also been shown to slow the rate of brain ageing by up to six years.
Evidence suggests that napping halfway through your day is ideal, and that naps should last no more than half an hour. Napping longer than that can make us feel groggy and cause a short-term dip in our thinking skills (however, over time, these long naps may still lead to improved brain function). On the other hand, a quick half-hour nap can immediately boost brain power, making us sharper and more alert. The catch is that the benefits from short naps don’t last long. To keep our minds sharp, we should aim for a short nap every day.
How do naps do this? We’re not entirely sure yet, but one leading theory is that, when we nap, the brain and the default network clean themselves: a vat of cerebrospinal fluid washes over our brain, washing away toxic proteins that accumulate during our waking hours, including beta-amyloid, a sticky protein thought to be a leading cause of Alzheimer’s disease. Even a single night of sleep deprivation can lead to increased levels of beta-amyloid in the brain.
“One leading theory is that, when we nap, the brain and the default network clean themselves.”
In terms of bedtime rituals, we know that a warm bath one to two hours before bed not only helps you fall asleep ten minutes faster, it also leads to deeper and more restorative sleep.
Another period of strong default network activity is our hypnagogic phase, the phase between wakefulness and sleep, and our hypnopompic phase, the phase between sleep and wakefulness. During these phases, please don’t scroll on your phone. Instead, just stare into space for a few minutes and then write down your thoughts.
It’s worth mentioning that we now think the main reason we’re seeing such an alarming rise in young cancer cases is because we spend a lot of time scrolling on our phones just before and just after sleep. The artificial light of phones blocks our melatonin production, and melatonin has now been found to have an incredibly powerful anti-cancer effect.
4. Mind wandering is a powerful tool to activate our brain’s default network.
Incredibly, we spend 25-50 percent of our waking lives mind wandering. This is one of the most effective ways to activate the default network, especially the medial temporal lobe, a region that supports the kind of introspective, creative, and autobiographical thinking that only happens when we’re not focused on a task.
As well as taking more breaks throughout the day, step out of your daily routine for a few minutes and just stare into space. Let your mind wander. This isn’t mindfulness or meditation; it isn’t about focused attention on the present—it’s more effortless than that.
Studies show that when people are asked to perform a repetitive task, those who engage in more mind wandering almost always perform better, precisely because they’re engaging their default network, which then increases creativity as well. Even when mind wandering hinders our performance in a task—when we have our heads in the clouds for just a little too long—it still ramps up creativity overall.
Why does mind wandering do this? Some research suggests that mind wandering facilitates creativity using a mechanism called the “fresh start” effect, a kind of neuronal reset switch that helps us see problems with fresh eyes. Other research suggests that mind wandering is a mental filtering process that occurs when the brain decides that the task just isn’t worth the effort, and that this then prompts a search for a better, more fulfilling task. So, when we’re forced into monotonous work, our brain essentially performs an unconscious calculation that simply asks, Is this worth it? And if the answer is No, it will send a message to our default network that basically says, Do your thing— wander!
Personally, I like to mind wander in the bath, which is a great way to unwind and decompress the brain before bed.
5. Nature reawakens the brain’s default network.
When we’re in green spaces, our brain waves shift from busy and anxious beta waves to daydreaming and creative alpha waves and meditative theta waves. That’s because nature abounds with what psychologists call “soft fascinations”—things that hold our attention in an effortless and relaxing way.
In everyday urban life, we’re relentlessly bombarded by “hard fascinations,” things like smartphone alerts, emails, train announcements, flashing billboards, overbearing bosses, and tight deadlines, each competing for our attention and causing cognitive fatigue.
“Nature abounds with what psychologists call ‘soft fascinations’—things that hold our attention in an effortless and relaxing way.”
Astonishingly, studies show that spending time in a forest improves creativity and problem-solving ability by 50 percent, and memory recall by 20 percent, compared to walking down an urban street, regardless of the weather.
There are broader physiological effects, too. Trees release natural chemicals called phytoncides, which protect them from bacteria. When we breathe in phytoncides—after just a few days of camping—our immune system activity can increase by up to 40 percent, and the effects can last for a month.
Walking in nature even modifies our skeletal muscles, prompting them to secrete molecules called myokines (also known as “hope molecules”), which cross the blood- brain barrier and act as an antidepressant. Even something as simple as hugging a tree has real effects: it slows your heart rate, lowers blood pressure, lifts your mood, and lowers stress. A study involving 20,000 people found that spending two hours a week in green spaces significantly improves psychological wellbeing, so I’d aim for a minimum of twenty minutes a day.
This new science has revolutionized my own life. These days, I work solidly for four to six hours a day and take breaks whenever I need them. I set a daily goal and achieve it, interspersing my work with time spent gazing out of the window, going on long walks in the park, taking afternoon naps, and allowing myself time to simply do nothing. Rest, I have realized, is the key to my health and productivity.
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