Social: Why Our Brains Are Wired to Connect (3 page)

CHAPTER 2
The Brain’s Passion

W
hen I was in graduate school, I went through a rough breakup with a girlfriend that left me feeling lost, as if I were half a person.
After a few months of self-pity and unhappy happy hours, I made a decision to devote myself to self-improvement.
If I was half a person, I had room to develop the other half.
So I set out to become who I wanted to be and who I thought I ought to be.
Within a year, I forgot all about this self-improvement plan and was simply myself again, but for a year, I was devoted to this project of becoming.

During that year, I devoted a few hours each day to whatever it was I hoped would change my life for the better.
But I had to make careful choices about how to spend these precious hours.
I had to place my bets.
What did I want to work at?
What a person practices not only reveals what a person believes he or she can be better at but also reflects a bet that person has made about what is worth spending time improving.
I decided to focus on becoming a better writer.
I practiced writing in my spare time, throwing out entire passages I had written just to see if I could rewrite them more effectively.
I studied art history, and I took folk guitar lessons, as well, but unlike my focus on writing, these pursuits didn’t produce any ripples that still affect my life today.

It turns out our brains have a passion of their own; we know this because the brain seems to devote nearly all of its spare time to one thing.
Unlike the different choices you and I might have made
about how to divide up our free time, our brains, when given a chance, almost all seem to practice the same thing.
Yes, our brains respond adaptively to whatever tasks they are given throughout the day.
If you are an accountant completing a report on a deadline, the brain regions involved with math are recruited to support your calculations.
If you are an art historian working as a curator at a museum, other brain regions might be brought online.
But when the brain is not focused on a specific task, when there are no tax spreadsheets or art inventories to be updated, the brain turns to its lifelong passion.

What is it that the human brain likes to practice?
Clearly, it must be extremely important to our success and well-being in life.
The brain did not evolve over millions of years to spend its free time practicing something irrelevant to our lives.
Indeed, the discovery that the brain is constantly practicing something suggests that evolution has, in a sense, made a bet about the value of that particular thing.

The Default Network

In 1997, Gordon Shulman and his colleagues
at Washington University published two papers back to back in the same issue of the
Journal of Cognitive Neuroscience
, a prestigious journal for neuro-imaging research.
At the time, positron emission tomography (PET) was a popular method for trying to identify which brain regions were involved in particular mental processes, such as memory, vision, and language.
In PET scanning, subjects inhale radioactive tracers; using gamma rays, scientists can determine where blood, containing the tracers, is flowing to in the brain.
When a region has more active neurons, more blood travels to that region.
Prior to PET scanning, neuropsychologists were largely limited to waiting for the occasional and unfortunate brain injury as a result of disease or head trauma if they wanted to advance their understanding of
where psychological processes occur in the brain.
Sadly, the best periods in the history of neuropsychological research tended to cluster around major wars, because of all the war-related head wounds causing damage to different brain regions.
PET scanning changed all of this.
Scientists were able to study almost any psychological question, whenever they wanted, without harming anyone.
It’s hard to overstate how profound this advance was.

Shulman’s two papers had a single mission: to look at a set of nine previous PET studies to determine whether there were brain regions that were always activated across a variety of mental activities studied by cognitive psychologists.
The first of these papers examined which regions were commonly activated by different tasks, including motor, memory, and visual discrimination tasks (such as indicating when an image changed slightly).
The results were a little disappointing: only a few regions showed increased activity across all the tasks, and they weren’t very interesting brain regions.
In hindsight, we know that these tasks rely on relatively distinct brain networks, so it makes sense that there wasn’t much overlap across these tasks.

In the second paper the scientists asked the question, “What is more active in the brain when one is
not
doing one of these cognitive, motor, or visual tasks?”
It was an unusual question.
Typically neuroscientists have been interested in brain regions that are “switched on”—that become more active—when performing a task, identifying regions that help us accomplish it.
Asking what in the brain becomes more active when you stop performing a task was a surprising approach.
Thankfully, Shulman asked the question anyway.
And he found a set of brain regions that were reliably more active when people were at rest, doing nothing, than when they were performing any of the specific tasks (see
Figure 2.1
).
This paper set in motion a mystery that is still unsolved to this day.
Why do we have brain regions that become more active when our minds go on their lunch break, so to speak—that is, when we are not doing anything in particular?
It makes sense that areas of the brain
involved in motor skills would quiet down when you finish doing a task that involves motor skills.
But why would some regions of the brain systematically become
more
active when you are finishing a motor task—the same regions that become more active when you are finishing a visual task or a math problem?

Figure 2.1 The Default Network

Calculatus Eliminatus

In the animated film of Dr.
Seuss’
The Cat in the Hat
, a “moss-covered three-handled family gradunza” has gone missing.
The Cat employs the official-sounding but entirely fictional technique of
calculatus eliminatus
in order to track it down.
According to the Cat,
calculatus eliminatus
requires identifying all the places the missing object is not.
The only remaining location will necessarily have to be where the missing object is.
Hardly an efficient approach to locating where you left your car keys.

Nevertheless, early on, this was roughly the approach that scientists had to take with the network Shulman had discovered.
Much more was known about what this network
did not do
than what it did.
The early name given to describe the network
was the “task-induced deactivation network” because it turned off in response to so many different kinds of tasks.
In other words, tasks induce this network to turn off.
Imagine having your job described in terms of all the things you
don’t
do.
You’re the nonaccountant, nonmarketer,
nonjournalist, nonsalesperson?
Cool.
But what is it you do exactly?
The second name given to this network
was the “default network” (or “default mode network”), which was better if only for its brevity.
This name has stuck with neuroscientists.
It refers to the fact that the network comes on by default when other tasks are finished.

Let’s see if we can figure out a bit more about what this network does.
Because participants lying in the PET scanner were not told to do anything during chunks of time when this network came on, it’s easy to imagine they were doing nothing.
As a result, it is natural to describe this default network as the set of regions in the brain that turn on when you are doing nothing.
However, there is an enormous difference between not being given a specific task and actually doing nothing.
Imagine you are lying inside a PET scanner.
Let’s say you are performing a routine cognitive task, such as indicating whether two letters on the screen are the same or different.
After doing this for a minute, the word “Rest” appears.
You know you have a minute of downtime before you have to start performing the boring task again.

The experimenter can’t gauge what you do next, but your mind is hardly at rest.
Go ahead and close your eyes for thirty seconds and try.
If you did, your mind probably darted around from one thought, feeling, or image to another.
Instead of being at rest, your mind was highly active.
If you are like most people, you thought about other people, yourself, or both.
In other words, you engaged in what psychologists call
social cognition
, which is simply another way of describing thinking about other people, oneself, and the relation of oneself to other people.
A college sophomore asked to do boring repetitive tasks in a psychology experiment in order to earn money to take someone on a date will start thinking, as soon as there is a break in the task, about the girl, the date, and whether or not she really likes him.

So perhaps the default network that comes on when we are given a break from performing cognitive tasks is involved in social cognition, the capacity to think about other people and ourselves.
It took
a while to find out whether or not that was true because social neuroscientists weren’t paying attention to research on the default network at first.
What the brain does when we stop doing a motor task does not sound like the kind of thing a social neuroscientist would usually care about.
But as it happens,
the network in the brain that reliably shows up
during social cognition studies is virtually identical to the default network.
In other words, the default network supports social cognition—making sense of other people and ourselves.

Default Social Cognition

At this point, you might think, “Isn’t it obvious that people think about people when they are not otherwise engaged?
Why is that so interesting?”
When I first noticed the overlap between the default network and the social cognition network, I didn’t think it was particularly significant for this very reason.
All this overlap tells us is that people typically have a strong interest in the social world and are likely to choose to think about it when they have free time.

I have since become convinced that I had the relationship between these two networks backward.
And this reversal is tremendously important.
Initially, I thought, “We turn on the default network during our free time because we are interested in the social world.”
While that is true, the reverse is also true and far more interesting: I now believe “we are interested in the social world
because we are built to turn on the default network during our free time
.”
In other words, if this network comes on like a reflex, it may nudge our attention toward the social world.
And not just to other people as objects in our environment.
Rather, the default network directs us to think about other people’s minds—their thoughts, feelings, and goals.
To take what philosopher Daniel Dennett called “the intentional stance,” it promotes understanding and empathy, cooperation, and consideration.
It suggests that evolution, figuratively speaking, made a big bet on the importance of developing and
using our social intelligence for the overall success of our species by focusing the brain’s free time on it.
I bet a year on becoming a better writer; evolution bet millions of years on making us more social.

But is there any reason to believe this claim that default network activity can be a cause, rather than a consequence, of our interest in the social world?
Is there evidence that it is a leading, rather than a lagging, indicator of social thinking?
There are a few provocative findings that suggest default network activity during rest may reflect an evolved predisposition to think about the social world in our free time rather than its being merely a moment-by-moment personal choice.

One key finding comes from newborns.
Babies show default network activity almost from the moment of birth.
One study looked at which brain regions were engaged
in highly coordinated activity in two-week-old babies and found that the default network was chugging away just as it does in adults.
Another group found evidence of a functional default network in two-day-old infants.
However, the same pattern was not seen in infants born prematurely, suggesting that this mechanism is engaged and set to turn on when we are most likely to enter the social world.

Why does the presence of default network activity in infants matter?
Because infants clearly haven’t cultivated an interest in the social world yet, or in model trains, or in anything.
Two-day-old infants cannot even focus their eyes yet.
In other words, the default network activity precedes any conscious interest in the social world, suggesting it might be instrumental in creating those interests.