WHY WALKING HELPS US THINK

WHY WALKING HELPS US THINK

Moreover, you must walk like a camel, which is said to be the only beast that ruminates when walking. Henry David Thoreau, “Walking” 1861

Charles Darwin was an introvert. Granted, he spent almost five years traveling around the world on the Beagle recording observations that produced some of the most important scientific insights ever made. But he was in his twenties then, embarking on a privileged, 19^th– century naturalist’s version of backpacking around Europe during a gap year. After returning home in 1836, he never again stepped outside the British Isles.
He avoided conferences, parties, and large gatherings. They made him anxious and exacerbated an illness that plagued much of his adult life. Instead, he passed his days at Down House, his quiet home almost 20-miles southeast of London, doing most of his writing in the study. He occasionally entertained a visitor or two but preferred to correspond with the world by letter. He installed a mirror in his study so he could glance up from his work to see the mailman coming up the road – the 19^th-century version of hitting the Refresh button on email.

Darwin’s best thinking, however, was not done in his study. It was done outside, on a lowercase d-shaped path on the edge of his property that he called the Sandwalk. Today, it is known as Darwin’s thinking path.

As a businessman, he would pile up a mound of flints at the turn of the path and knock one away every time he passed to ensure he made a predetermined number of circuits without having to interrupt his train of thought. Five turns around the path amounted to half a mile or so. The Sandwalk was where he pondered. In this soothing routine, a sense of place became preeminent in Darwin’s science. It shaped his identity as a thinker.
Darwin circled the Sandwalk as he developed his theory of evolution, by means of natural selection. He walked to ponder the mechanism of movement in climbing plants and to imagine what wonders pollinated the fantastically shaped colorful orchids he described. He walked as he accumulated evidence for human ancestry. His final walks were done with his wife Emma as he thought about earth worms and their role in gradually remodeling the soil.

Today, the desk in his study is still cluttered with books, letters, and small specimen boxes containing pinned insects. Hanging from a nearby chair is his black jacket, black bowler hat, and a wooden walking stick, the bottom of which is well worn – evidence of the miles on the Sandwalk. Walk out the back kitchen of the cream-coloured home, pass the green trellis and vine-covered columns holding up Darwin’s back porch, dross the beautifully groomed garden, and enter the Sandwalk. It is easy to imagine that it was 1871 and that you are taking a walk with Darwin himself. Stack 5 flat flints at the entrance for 5 laps and begin the walk, first along the meadow and then counterclockwise into the woods. The Sandwalk is alive. Underfoot, fungi decompose wet leaves, emitting the smell of wet earth. With each step, the gravel crunched, and your shoes occasionally slip on damp stones worn smooth by thousands of footsteps, including some taken by Darwin himself.

Down House is not a place of magic, nor is it a place of worship. Looping the Sandwalk one flint at a time doesn’t endow you with the wisdom to continue your scientific pursuits. It turns out, any walk outdoors has the potential to unlock our brains. The Sandwalk just happened to be where the unlocking of one 19^th-century brain helped change the world and our place in it. But why? Why does walking help us think?

Walking and thinking. You are undoubtedly familiar with this situation: You’re struggling with a problem – a tough work or school assignment, a complicated relationship, the prospects of a career change – and you cannot figure out what to do. So, you decide to take a walk, and somewhere along that trek, the answer comes to you.
The 19^th-century English poet William Wordsworth is said to have walked 180,000 miles in his life. Surely on one of those walks, he discovered his dancing daffodils. French philosopher Jean-Jacques Rousseau once said, “There is something about walking which stimulates and enlivens my thoughts. When I stay in one place I can hardly think at all; my body has to be on the move to set my mind going.” Ralph Waldo Emerson’s and Henry David Thoreau’s walks in the New England woods inspired their writing, including “Walking,” Thoreau’s treatise on the subject. John Muir, Jonathan Swift, Immanuel Kant, Beethoven, Henry Cavendish, and Frederick Nietzsche were obsessive walkers. Nietzsche, who walked with his notebook every day between 11 am and 1 pm, said, “All truly great thoughts are conceived by walking.” Charles Dickens preferred to take long walks through London at night. “The road was so lonely in the night, that I fell asleep to the monotonous sound of my own feet, doing their regular four miles an hour,” Dickens wrote, “Mile after mile I walked, without the slightest sense of exertion, dozing heavily and dreaming constantly.” More recently, walks became an important part of the creative process of Apple cofounder Steve Jobs.

It is important to pause and reflect on these famous walkers. They were all guys and virtually all had Asperger’s syndrome. Little has been written about famous women who regularly walked. Virginia Woolf is one exception. She apparently walked quite a bit. More recently, Rob Davidson trekked with her dog and four camels across Australia and wrote about it in her book Tracks. In 1999, Dorris Haddock, an 89-year-old grandmother from Dublin, New Hampshire, walked 3,200 miles from coast to coast to protest United States campaign finance laws.

Historically, however, walking has been the privilege of white men. Black men were likely to be arrested, or worse. Women just out for a walk were harassed, or worse. And, of course, rarely in our evolutionary history was it safe for anyone to walk alone.
Perhaps it is a coincidence that so many great thinkers were obsessive walkers. There could be many brilliant thinkers who never walked. Did Willian Shakespeare, Jane Austen, or Toni Morrison walk every day? What about Frederick Douglass, Marie Curie, or Isaac Newton? Surely the astoundingly brilliant Stephen Hawking did not walk after ALS paralyzed him. So walking is not essential to thinking, but it certainly helps.

Marily Oppezzo, a Stanford University psychologist, used to walk around campus with her Ph.D. advisor to discuss lab results and brainstorm new projects. One day they came up with an experiment to look at the effects of walking on creative thinking. Was there something to the age-old idea that walking and thinking are linked?

Oppezzo designed an elegant experiment. A group of Stanford students was asked to list as many creative uses for common objects as they could. A Frisbee, for example, can be used as a dog toy, but it can also be used as a hat, a plate, a bird bath, or a small shovel. The more novel uses a student listed, the higher the creativity score. Half the students sat for an hour before they were given their test. The others walked on a treadmill. The results were staggering. Creativity scores improved by 60% after a walk.

Another study of brain connectivity recruited 65 couch-potato volunteers aged 55 – 80 and imaged their brains in an MRI machine. For the next year, half of her volunteers took 45-minute walks three times a week. The other participants kept spending their days watching Golden Girls reruns and only participated in stretching exercises as a control. After a year, they were put back in the MRI machine and imaged their brains again. Not much had happened to the control group, but the walkers had significantly improved connectivity in regions of the brain understood to play an important role in our ability to think creatively.

Walking changes our brains, and it impacts not only creativity but also memory.
A study involving 18,766 women aged 70 to 81 showed that even walking as little as 90 minutes per week reduced the rate at which cognition declined over time. As cognitive decline is what occurs in the earliest stages of dementia, walking might ward off that neurodegenerative condition. But correlation does not equal causation. Maybe mentally active people were simply more likely to go for a walk?

One source of information comes from medical students dissecting cadavers in first-year anatomy. Paleontologists need to know anatomy. A fossil could be from any one of more than 200 different bones in the body and from one of dozens of different animals often found along with human fossils. The brain is accessed by sawing off the top of the head. Students are awed when they hold the brain. The brain is the person. The brain is cut into left and right halves. Sitting on top of the brain stem is a thick loop of tissue about the length of a pinky finger. It is called the hippocampus and is the memory center of the brain. Old memories are often retained, but new ones aren’t. This puzzles and frustrates them and they get angry. This should make us want to do everything we can to maintain this region of our brain. Other kinds of memories are stored elsewhere – the ability to recognize faces, so-called implicit memories like how to ride a bike, and so-called explicit memories such as the date WWII began. But the hippocampus is the depository of our life stories.

As we get old, our brain gets smaller and in later years, the hippocampus shrinks at a clip of 1 to 2% per year, and it becomes more and more difficult to recall things that used to come to us instantly. What are we to do about this? Walk.

A study of 120 aging but otherwise healthy people had MRIs that measured the size of their hippocampus. Half were asked to walk forty minutes three times a week. The other half just did stretches but did not take the long walks. After a year, the stretching group had lost between 1 and 2% of the volume of the hippocampus. That was expected. But something extraordinary happened with the walkers. They gained some. The walking group, on average, had grown the hippocampus by 2%. Accordingly, their memory had improved.

The hippocampus, it turns out, can regenerate, and even with just a daily walk can promote growth. Walking can not only delay some effects of aging but can reverse them. But how? One explanation is that walking, or any exercise, helps get the blood flowing,  and, indeed this happens.

MRI brain scans of people who walked for 10 minutes every half hour or so and others who sat all day showed that those who walked had significantly greater blood flow in the middle cerebral and carotid arteries. But blood flow is just the vehicle. It must be carrying something of critical importance to the brain.