22 Oct Habits are often as much a curse as a benefit (CHARLES DUHIGG) | Part A’
When the MIT researchers started working on habits in the 1990s—
at about the same time that Eugene came down with his fever—they
were curious about a nub of neurological tissue known as the basal
ganglia. If you picture the human brain as an onion, composed of layer
upon layer of cells, then the outside layers—those closest to the scalp—
are generally the most recent additions from an evolutionary
perspective. When you dream up a new invention or laugh at a friend’s
joke, it’s the outside parts of your brain at work. That’s where the most
complex thinking occurs.
Deeper inside the brain and closer to the brain stem—where the
brain meets the spinal column—are older, more primitive structures.
They control our automatic behaviors, such as breathing and
swallowing, or the startle response we feel when someone leaps out
from behind a bush. Toward the center of the skull is a golf ball–sized
lump of tissue that is similar to what you might find inside the head of
a fish, reptile, or mammal. This is the basal ganglia, an oval of cells
that, for years, scientists didn’t understand very well, except for
suspicions that it played a role in diseases such as Parkinson’s.
In the early 1990s, the MIT researchers began wondering if the basal
ganglia might be integral to habits as well. They noticed that animals
with injured basal ganglia suddenly developed problems with tasks
such as learning how to run through mazes or remembering how to
open food containers. They decided to experiment by employing new
micro-technologies that allowed them to observe, in minute detail,
what was occurring within the heads of rats as they performed dozens
of routines. In surgery, each rat had what looked like a small joystick
and dozens of tiny wires inserted into its skull. Afterward, the animal
was placed into a T-shaped maze with chocolate at one end.
The maze was structured so that each rat was positioned behind a
partition that opened when a loud click sounded. Initially, when a rat
heard the click and saw the partition disappear, it would usually
wander up and down the center aisle, sniffing in corners and
scratching at walls. It appeared to smell the chocolate, but couldn’t
figure out how to find it. When it reached the top of the T, it often
turned to the right, away from the chocolate, and then wandered left,
sometimes pausing for no obvious reason. Eventually, most animals
discovered the reward. But there was no discernible pattern in their
meanderings. It seemed as if each rat was taking a leisurely,
unthinking stroll.
The probes in the rats’ heads, however, told a different story. While
each animal wandered through the maze, its brain—and in particular,
its basal ganglia—worked furiously. Each time a rat sniffed the air or
scratched a wall, its brain exploded with activity, as if analyzing each
new scent, sight, and sound. The rat was processing information the
entire time it meandered.
The scientists repeated their experiment, again and again, watching
how each rat’s brain activity changed as it moved through the same
route hundreds of times. A series of shifts slowly emerged. The rats
stopped sniffing corners and making wrong turns. Instead, they zipped
through the maze faster and faster. And within their brains, something
unexpected occurred: As each rat learned how to navigate the maze, its
mental activity decreased. As the route became more and more
automatic, each rat started thinking less and less.
It was as if the first few times a rat explored the maze, its brain had
to work at full power to make sense of all the new information. But
after a few days of running the same route, the rat didn’t need to
scratch the walls or smell the air anymore, and so the brain activity
associated with scratching and smelling ceased. It didn’t need to
choose which direction to turn, and so decision-making centers of the
brain went quiet. All it had to do was recall the quickest path to the
chocolate. Within a week, even the brain structures related to memory
had quieted. The rat had internalized how to sprint through the maze
to such a degree that it hardly needed to think at all.
But that internalization—run straight, hang a left, eat the chocolate
—relied upon the basal ganglia, the brain probes indicated. This tiny,
ancient neurological structure seemed to take over as the rat ran faster
and faster and its brain worked less and less. The basal ganglia was
central to recalling patterns and acting on them. The basal ganglia, in
other words, stored habits even while the rest of the brain went to
sleep.
To see this capacity in action, consider this graph, which shows
activity within a rat’s skull as it encounters the maze for the first time.
Initially, the brain is working hard the entire time:
After a week, once the route is familiar and the scurrying has
become a habit, the rat’s brain settles down as it runs through the
maze:
This process—in which the brain converts a sequence of actions into
an automatic routine—is known as “chunking,” and it’s at the root of
how habits form. There are dozens—if not hundreds—of behavioral
chunks that we rely on every day. Some are simple: You automatically
put toothpaste on your toothbrush before sticking it in your mouth.
Some, such as getting dressed or making the kids’ lunch, are a little
more complex.
Others are so complicated that it’s remarkable a small bit of tissue
that evolved millions of years ago can turn them into habits at all. Take
the act of backing your car out of the driveway. When you first learned
to drive, the driveway required a major dose of concentration, and for
good reason: It involves opening the garage, unlocking the car door,
adjusting the seat, inserting the key in the ignition, turning it
clockwise, moving the rearview and side mirrors and checking for
obstacles, putting your foot on the brake, moving the gearshift into
reverse, removing your foot from the brake, mentally estimating the
distance between the garage and the street while keeping the wheels
aligned and monitoring for oncoming traffic, calculating how reflected
images in the mirrors translate into actual distances between the
bumper, the garbage cans, and the hedges, all while applying slight
pressure to the gas pedal and brake, and, most likely, telling your
passenger to please stop fiddling with the radio.
Nowadays, however, you do all of that every time you pull onto the
street with hardly any thought. The routine occurs by habit.
Millions of people perform this intricate ballet every morning,
unthinkingly, because as soon as we pull out the car keys, our basal
ganglia kicks in, identifying the habit we’ve stored in our brains
related to backing an automobile into the street. Once that habit starts
unfolding, our gray matter is free to quiet itself or chase other
thoughts, which is why we have enough mental capacity to realize that
Jimmy forgot his lunchbox inside.
Habits, scientists say, emerge because the brain is constantly
looking for ways to save effort
Part b’ follows
The power of habit
CHARLES DUHIGG
