There is a walk you take without deciding to. Out of the gate, left at the warung with the blue tarpaulin, along the wall where the bougainvillea has escaped, past the tree that lifts the pavement, and back. You could not draw it accurately. Your feet could do it in the dark.

We are taught to be slightly ashamed of this. The culture of travel and self improvement tells us that the good life is made of new streets, that routine is a kind of sleep, and that a person who walks the same loop every evening has stopped paying attention. Take a different way home, the advice goes. Get lost on purpose.

It is pleasant advice for a holiday, and we have praised the aimless walk ourselves, in The Morning Walk Has No Destination. But as a verdict on routine it has things backwards. The known route is not where attention goes to die. It is where attention is finally released from the job of getting somewhere, and becomes available for everything else.

What habit hands back

In 2002 the psychologist Wendy Wood and her colleagues asked students to keep a diary, hour by hour, of what they were doing and what they were thinking about. Somewhere between a third and a half of what the students reported doing turned out to be habitual: performed almost daily, in the same place. That figure is often quoted. The more interesting finding sits beside it.

When people were doing something that was not a habit, their thoughts were about what they were doing. When they were doing something habitual, their thoughts were usually about something else entirely. They also reported less stress. Habit, in other words, is not just efficiency. It is a mechanism for separating the body’s business from the mind’s. The action runs by itself, and the person is set free inside it.

This is the quiet engineering behind the known route. A new street demands constant small decisions. Which way, how far, is this safe, where does it come out? Each one is trivial, and together they occupy exactly the part of the mind you were hoping to use. A familiar street has already answered all of them. The walk is solved. What remains is the walking.

Two ways of knowing a street

The brain keeps two different records of the places we move through. In a well known experiment, Tom Hartley, Eleanor Maguire and their colleagues put people in a scanner and had them move through a virtual town. When they had to find a new way between places, the work fell to the hippocampus, the structure that builds flexible maps. When they followed a route they had already learned well, activity shifted toward the caudate nucleus, part of the system that runs habits.

Maguire’s more famous study makes the contrast vivid. London taxi drivers, who must hold the whole city in their heads and improvise across it, had more grey matter in the rear of the hippocampus than other people, and more the longer they had driven. That is the brain of the pathfinder. It should be said plainly that the known route does not build this. If anything it lets that machinery rest. The well worn path is not a workout for the mind. It is a chair.

There is a modern counterfeit of this ease. A study by Louisa Dahmani and Véronique Bohbot found that drivers who had leaned most heavily on satellite navigation over their lives had poorer spatial memory when asked to find their way unaided. It was a small study and the authors asked for it to be repeated. But it points at a real distinction. A route your body knows is knowledge. A route your phone knows is a subscription. Both free you from thinking about the way. Only one of them belongs to you.

The thinking path

Behind his house in Kent, Charles Darwin laid out a gravel loop about a quarter of a mile around, through a strip of trees and along the edge of a field. It was called the Sandwalk, and it came to be known as his thinking path. He walked it daily for decades, and his son Francis remembered that in earlier years he would set a number of turns in advance and count them with a heap of flints, kicking one off the path each time he passed. His children, it is said, sometimes added stones to the pile.

The detail matters. Here was one of the most original minds of his century, a man who had sailed around the world, choosing for his daily thinking the least novel walk available, and then handing even the counting to a pile of stones. He wanted nothing left in his head but the problem.

Immanuel Kant’s afternoon walk in Königsberg is the more famous example, and the more embroidered. The poet Heinrich Heine, who never saw it, wrote that the neighbors knew the hour by the philosopher’s appearance in his grey coat. It is a satirist’s joke that hardened into a fact. What biographers do accept is that in his middle and later years Kant walked daily and with great regularity. The legend has the right instinct, all the same. We sense that the sameness of the walk and the range of the thought were not unrelated.

A modern experiment lends some support. At Stanford, Marily Oppezzo and Daniel Schwartz found that people generated more ideas, and more original ones, while walking than while sitting, on a treadmill facing a blank wall as well as outdoors, and that the effect lingered for a little while after they sat down. Walking did not help with problems that have a single right answer. It loosens the mind. It does not sharpen it. The study did not compare familiar routes with strange ones, but it is suggestive that a blank wall was enough. Scenery, apparently, is not the active ingredient.

An honest complication

It would be neat to stop there, with the freed mind wandering happily toward its discoveries. The evidence does not quite allow it. In a large study using a phone app to interrupt people at random moments, Matthew Killingsworth and Daniel Gilbert found that minds wander almost half the time, and that people are on the whole less happy when their thoughts have drifted than when they are absorbed in what they are doing. A wandering mind, they concluded, is an unhappy mind.

Nor is it settled that wandering makes us creative. One influential experiment suggested that a break spent on an undemanding task helps people solve problems they had been stuck on. Later attempts to repeat it have had mixed results. The honest summary is that the known route opens a door and does not guarantee what comes through it. Some evenings it is an idea. Some evenings it is the same worry, walked around the block.

Perhaps that is the point at which the luxury becomes a practice. The free attention that a familiar walk returns can be spent on rumination, or it can be spent outward: on the light, on the particular green of this week, on the neighbor who has repainted a gate. The route does not choose for you. It only makes the choice possible, which is more than most of the day offers.

A signature scent is a known route

There is the same suspicion in perfume as in walking. The enthusiast is supposed to want a new bottle every month, a collection, a wardrobe, a constant change of street. Wearing one fragrance for years is treated as a failure of curiosity.

We have come to think the opposite is true, or at least that both are needed. A scent worn for a long time stops being a decision. It no longer asks to be evaluated each morning. And because it is constant, it becomes an instrument for noticing everything that is not: how it sits differently in the rains, how it changes on a tired day, how a composition you believed you knew still has a turn in it that you only caught this year. Only on a street you know can you see what has changed.

The new street and the new bottle have their pleasures, and we would not want a life without them. But novelty is cheap now. It is delivered to everyone, all day, without being asked for. What has become rare is the other thing: a way home that your feet know, a small circuit of the world that asks nothing of you, and, while you are on it, a mind that is for once entirely your own.