Brain Rules (Updated and Expanded)

18 months old: Your preferences aren’t the same as mine
The distance between 14 months of age and 18 months of age is
extraordinary. Around 14 months, toddlers think that because they like
something, the whole world likes the same thing—as summed up in the
“Toddler’s Creed”:
If I want it, it is mine.
If I give it to you and change my mind later, it is mine.
If I can take it away from you, it is mine.
If we are building something together, all of the pieces are mine.
If it looks just like mine, it is mine.
If it is mine, it will never belong to anybody else, no matter what.
If it is yours, it is mine.
Around 18 months, it dawns on babies that this viewpoint may not
always be accurate. They begin to learn that adage that most newlyweds
have to relearn in spades: “What is obvious to you is obvious to you.”
How do babies react to such new information? By testing it, as usual.
Before the age of 2, babies do plenty of things parents would rather them
not do. But after the age of 2, small children will do things 
because
their
parents don’t want them to. The compliant little darlings seem to transform
into rebellious little tyrants. Many parents think their children are actively
defying them at this stage. (The thought certainly crossed my mind as I
nursed Joshua’s unfortunate beesting.) That would be a mistake, however.
This stage is simply the natural extension of a sophisticated research
program begun at birth. You push the boundaries of people’s preferences,
then stand back and see how they react. Then you repeat the experiment,
pushing them to their limits over and over again to see how stable the
findings are, as if you were playing peekaboo. Slowly you begin to perceive
the length and height and breadth of people’s desires, and how they differ

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from yours. Then, just to be sure the boundaries are still in place, you
occasionally do the whole experiment over again.
Babies may not have a whole lot of understanding about their world, but
they know a whole lot about how to get it. It reminds me of the old proverb,
“Catch me a fish and I eat for a day; teach me to fish and I eat for a
lifetime.”
Babies reveal more of the brain’s secrets each year
Why does a baby stick its tongue back out at you? The beginnings of a
neural road map have been drawn in the past few years, at least for some of
the “simpler” thinking behaviors, such as imitation. Three investigators at
the University of Parma were studying the macaque, assessing brain activity
as it reached for different objects in the laboratory. The researchers recorded
the pattern of neural firing when the monkey picked up a raisin. One day,
researcher Leonardo Fogassi walked into the laboratory and casually
plucked a raisin from a bowl. Suddenly, the monkey’s brain began to fire
excitedly. The recordings were in the raisin-specific pattern, 
as if the animal
had just picked up the raisin
. But the monkey had not picked up the raisin.
It simply saw Fogassi do it.
The astonished researchers quickly replicated and extended their
findings, and then published them in a series of landmark papers describing
the existence of “mirror neurons.” Mirror neurons are cells whose activity
reflect their surroundings. Cues that could elicit mirror neural responses
were found to be remarkably subtle. If a primate simply heard the sound of
someone doing something it had previously experienced—say, tearing a
piece of paper—these neurons could fire as if the monkey were
experiencing the full stimulus. It wasn’t long before researchers identified
human mirror neurons. These neurons are scattered across the brain, and a
subset is involved in action recognition—that classic imitative behavior
such as babies sticking out their tongues. Other neurons mirror a variety of
motor behaviors.
We also are beginning to understand which regions of the brain are
involved in our ability to learn from a series of increasingly self-corrected
ideas. We use our right prefrontal cortex to predict error and to
retrospectively evaluate input for errors. The anterior cingulate cortex, just

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south of the prefrontal cortex, signals us when perceived unfavorable
circumstances call for a change in behavior. Every year, the brain reveals
more and more of its secrets, with babies leading the way.
We never outgrow the desire to know
We can remain lifelong learners. No question. This fact was brought home
to me as a postdoctoral scholar at the University of Washington. In 1992,
Edmond Fischer and Edwin Krebs shared the Nobel Prize in Physiology or
Medicine. I had the good fortune to be familiar with both their work and
their offices. They were just down the hall from mine. By the time I arrived
at the university, Fischer and Krebs were already in their mid-70s. The first
thing I noticed upon meeting them was that they were not retired. Not
physically and not mentally. Long after they had earned the right to be
lounging on some tropical island, both had powerful, productive
laboratories in full swing. Every day I would see them walking down the
hall, oblivious to others, chatting about some new finding, swapping each
other’s journals, and listening intently to each other’s ideas. Sometimes they
would have someone else along, grilling them and in turn being grilled
about some experimental result. They were as creative as artists, wise as
Solomon, lively as children. They had lost 
nothing
. Their intellectual
engines were still revving, and curiosity remained the fuel. They taught me
that our learning abilities don’t have to change as we age.