That Is Not How Your Brain Works

Forget these scientific myths to better understand your brain and yourself.

Lisa Feldman Barrett By Lisa Feldman Barrett March 3, 2021

The 21st century is a time of great scientific discovery. Cars are
driving themselves. Vaccines against deadly new viruses are created…By
Lisa Feldman Barrett

The 21st century is a time of great scientific discovery. Cars are
driving themselves. Vaccines against deadly new viruses are created in
less than a year. The latest Mars Rover is hunting for signs of alien
life. But we’re also surrounded with scientific myths: outdated beliefs
that make their way regularly into news stories.

Being wrong is a normal and inevitable part of the scientific process.
We scientists do our best with the tools we have, until new tools
extend our senses and let us probe more deeply, broadly, or precisely.
Over time, new discoveries lead us to major course corrections in our
understanding of how the world works, such as natural selection and
quantum physics. Failure, therefore, is an opportunity to discover and
learn.^1

Brains don’t work by stimulus and response. All your neurons are
firing at various rates all the time.

But sometimes, old scientific beliefs persist, and are even vigorously
defended, long after we have sufficient evidence to abandon them. As a
neuroscientist, I see scientific myths about the brain repeated
regularly in the media and corners of academic research. Three of them,
in particular, stand out for correction. After all, each of us has a
brain, so it’s critical to understand how that three-pound blob between
your ears works.

Myth number one is that specific parts of the human brain have specific
psychological jobs. According to this myth, the brain is like a
collection of puzzle pieces, each with a dedicated mental function. One
puzzle piece is for vision, another is for memory, a third is for
emotions, and so on. This view of the brain became popular in the 19th
century, when it was called phrenology. Its practitioners believed they
could discern your personality by measuring bumps on your skull.
Phrenology was discredited by better data, but the general idea was
never fully abandoned.^2

Today, we know the brain isn’t divided into puzzle pieces with
dedicated psychological functions. Instead, the human brain is a
massive network of neurons.^3 Most neurons have multiple jobs, not a
single psychological purpose.^4 For example, neurons in a brain region
called the anterior cingulate cortex are regularly involved in memory,
emotion, decision-making, pain, moral judgments, imagination,
attention, and empathy.
LIZARD BRAIN: Why does the tale linger that our instincts stem from a
part of our brain inherited from reptilian ancestors? Because if bad
behavior stems from our inner beasts, then we’re less responsible for
some of our actions.Galina Gala / Shutterstock

I’m not saying that every neuron can do everything, but most neurons do
more than one thing. For example, a brain region that’s intimately tied
to the ability to see, called primary visual cortex, also carries
information about hearing, touch, and movement.^5 In fact, if you
blindfold people with typical vision for a few days and teach them to
read braille, neurons in their visual cortex become more devoted to the
sense of touch.^6 (The effect disappears in a day or so without the
blindfold.)

In addition, the primary visual cortex is not necessary for all aspects
of vision. Scientists have believed for a long time that severe damage
to the visual cortex in the left side of your brain will leave you
unable to see out of your right eye, assuming that the ability to see
out of one eye is largely due to the visual cortex on the opposite
side. Yet more than 50 years ago, studies on cats with cortical
blindness on one side showed that it is possible to restore some of the
lost sight by cutting a connection deep in the cat’s midbrain. A bit
more damage allowed the cats to orient toward and approach moving
objects.

Perhaps the most famous example of puzzle-piece thinking is the “triune
brain”: the idea that the human brain evolved in three layers. The
deepest layer, known as the lizard brain and allegedly inherited from
reptile ancestors, is said to house our instincts. The middle layer,
called the limbic system, allegedly contains emotions inherited from
ancient mammals. And the topmost layer, called the neocortex, is said
to be uniquely human—like icing on an already baked cake—and supposedly
lets us regulate our brutish emotions and instincts.

Myth number one is that specific parts of the human brain have
specific psychological jobs.

This compelling tale of brain evolution arose in the mid 20th century,
when the most powerful tool for inspecting brains was an ordinary
microscope. Modern research in molecular genetics, however, has
revealed that the triune brain idea is a myth. Brains don’t evolve in
layers, and all mammal brains (and most likely, all vertebrate brains
as well) are built from a single manufacturing plan using the same
kinds of neurons.

Nevertheless, the triune brain idea has tremendous staying power
because it provides an appealing explanation of human nature. If bad
behavior stems from our inner beasts, then we’re less responsible for
some of our actions. And if a uniquely human and rational neocortex
controls those beasts, then we have the most highly evolved brain in
the animal kingdom. Yay for humans, right? But it’s all a myth. In
reality, each species has brains that are uniquely and effectively
adapted to their environments, and no animal brain is “more evolved”
than any other.

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So why does the myth of a compartmentalized brain persist? One reason
is that brain-scanning studies are expensive. As a compromise, typical
studies include only enough scanning to show the strongest, most robust
brain activity. These underpowered studies produce pretty pictures that
appear to show little islands of activity in a calm-looking brain. But
they miss plenty of other, less robust activity that may still be
psychologically and biologically meaningful. In contrast, when studies
are run with enough power, they show activity in the majority of the
brain.^7

Another reason is that animal studies sometimes focus on one small part
of the brain at a time, even just a few neurons. In pursuit of
precision, they wind up limiting their scope to the places where they
expect to see effects. When researchers instead take a more holistic
approach that focuses on all the neurons in a brain—say, in flies,
worms, or even mice—the results show more what looks like whole-brain
effects.^8

Pretty much everything that your brain creates, from sights and sounds
to memories and emotions, involves your whole brain. Every neuron
communicates with thousands of others at the same time. In such a
complex system, very little that you do or experience can be traced to
a simple sum of parts.

Myth number two is that your brain reacts to events in the world.
Supposedly, you go through your day with parts of your brain in the off
position. Then something happens around you, and those parts switch on
and “light up” with activity.

Brains, however, don’t work by stimulus and response. All your neurons
are firing at various rates all the time. What are they doing? Busily
making predictions.^9 In every moment, your brain uses all its
available information (your memory, your situation, the state of your
body) to take guesses about what will happen in the next moment. If a
guess turns out to be correct, your brain has a head start: It’s
already launching your body’s next actions and creating what you see,
hear, and feel. If a guess is wrong, the brain can correct itself and
hopefully learn to predict better next time. Or sometimes it doesn’t
bother correcting the guess, and you might see or hear things that
aren’t present or do something that you didn’t consciously intend. All
of this prediction and correction happens in the blink of an eye,
outside your awareness.

If a predicting brain sounds like science fiction, here’s a quick
demonstration. What is this picture?

If you see only some curvy lines, then your brain is trying to make a
good prediction and failing. It can’t match this picture to something
similar in your past. (Scientists call this state “experiential
blindness.”) To cure your blindness, visit
[176]lisafeldmanbarrett.com/nautilus and read the description, then
come back here and look at the picture again. Suddenly, your brain can
make meaning of the picture. The description gave your brain new
information, which conjured up similar experiences in your past, and
your brain used those experiences to launch better predictions for what
you should see. Your brain has transformed ambiguous, curvy lines into
a meaningful perception. (You will probably never see this picture as
meaningless again.)

Predicting and correcting is a more efficient way to run a system than
constantly reacting in an uncertain world. This is clear every time you
watch a baseball game. When the pitcher hurls the ball at 96 miles per
hour toward home plate, the batter doesn’t have enough time to wait for
the ball to come close, consciously see it, and then prepare and
execute the swing. Instead, the batter’s brain automatically predicts
the ball’s future location, based on rich experience, and launches the
swing based on that prediction, to be able to have a hope of hitting
the ball. Without a predicting brain, sports as we know them would be
impossible to play.

What does all this mean for you? You’re not a simple stimulus-response
organism. The experiences you have today influence the actions that
your brain automatically launches tomorrow.

The third myth is that there’s a clear dividing line between diseases
of the body, such as cardiovascular disease, and diseases of the mind,
such as depression. The idea that body and mind are separate was
popularized by the philosopher René Descartes in the 17th century
(known as Cartesian dualism) and it’s still around today, including in
the practice of medicine. Neuroscientists have found, however, that the
same brain networks responsible for controlling your body also are
involved in creating your mind.^10 A great example is the anterior
cingulate cortex, which I mentioned earlier. Its neurons not only
participate in all the psychological functions I listed, but also they
regulate your organs, hormones, and immune system to keep you alive and
well.

Modern research in molecular genetics has revealed that the triune
brain idea is a myth.

Every mental experience has physical causes, and physical changes in
your body often have mental consequences, thanks to your predicting
brain. In every moment, your brain makes meaning of the whirlwind of
activity inside your body, just as it does with sense data from the
outside world. That meaning can take different forms. If you have
tightness in your chest that your brain makes meaningful as physical
discomfort, you’re likely to visit a cardiologist. But if your brain
makes meaning of that same discomfort as distress, you’re more likely
to book time with a psychiatrist. Note that your brain isn’t trying to
distinguish two different physical sensations here. They are pretty
much identical, and an incorrect prediction can[177] cost you your
life. Personally, I have three friends whose mothers were misdiagnosed
with anxiety^11 when they had serious illnesses, and two of them died.

When it comes to illness, the boundary between physical and mental is
porous. Depression is usually catalogued as a mental illness, but it’s
as much a metabolic illness as cardiovascular disease, which itself has
significant mood-related symptoms. These two diseases occur together so
often that some medical researchers believe that one may cause the
other. That perspective is steeped in Cartesian dualism. Both
depression^12 and cardiovascular disease^13 are known to involve
problems with metabolism, so it’s equally plausible that they share an
underlying cause.

When thinking about the relationship between mind and body, it’s
tempting to indulge in the myth that the mind is solely in the brain
and the body is separate. Under the hood, however, your brain creates
your mind while it regulates the systems of your body. That means the
regulation of your body is itself part of your mind.

Science, like your brain, works by prediction and correction.
Scientists use their knowledge to fashion hypotheses about how the
world works. Then they observe the world, and their observations become
evidence they use to test the hypotheses. If a hypothesis did not
predict the evidence, then they update it as needed. We’ve all seen
this process in action during the pandemic. First we heard that
COVID-19 spread on surfaces, so everyone rushed to buy Purell and
Clorox wipes. Later we learned that the virus is mainly airborne and
the focus moved to ventilation and masks. This kind of change is a
normal part of science: We adapt to what we learn. But sometimes
hypotheses are so strong that they resist change. They are maintained
not by evidence but by ideology. They become scientific myths.

Lisa Feldman Barrett ([178]@LFeldmanBarrett) is a professor of
psychology at Northeastern University and the author of Seven and a
Half Lessons About the Brain. Learn more at[179]
LisaFeldmanBarrett.com.

References

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4. Anderson, M.L. After Phrenology MIT Press, Cambridge, MA (2014).

5. Liang, M., Mouraux, A., Hu, L., & Lannetti, G.D. Primary sensory
cortices contain distinguishable spatial patterns of activity for each
sense. Nature Communications 4, 1979 (2013).

6. Merabet, L.B., et al. Rapid and reversible recruitment of early
visual cortex for touch. PLoS One 3, e3046 (2008).

7. Gonzalez-Castillo, J., et al. Whole-brain, time-locked activation
with simple tasks revealed using massive averaging and model-free
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8. Kaplan, H.S. & Zummer, M. Brain-wide representations of ongoing
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11. Martin, R., et al. Gender disparities in common sense models of
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disorders. Annals of Medicine 40, 281-295 (2008).

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