Brain Rules (Updated and Expanded)

Blind spots
There is a region in the eye where retinal neurons, carrying visual
information, gather together to begin their journey into deep brain tissue.
That gathering place is called the optic disk. It’s a strange region, because
there are no cells that can perceive sight in the optic disk. It is blind in that
region—and you are, too. It is called the blind spot, and each eye has one.
Do you ever see two black holes in your field of view that won’t go away?
That’s what you should see. But your brain plays a trick on you. As the
signals are sent to your visual cortex, the brain detects the presence of the
holes, examines the visual information 360 degrees around the spot, and
calculates what is most likely to be there. Then, like a paint program on a
computer, it fills in the spot. The process is called “filling in,” but it could

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be called “faking it.” Some scientists believe that the brain simply ignores
the lack of visual information, rather than calculating what’s missing. Either
way, you’re not getting a 100 percent accurate representation.
Dreams during the night—or day
It should not surprise you that the brain possesses an imaging system
with a mind of its own. Proof is as close as your most recent dream.
(There’s a hallucination for you.) Actually, the visual system is even more
of a loose cannon than that. Millions of people suffer from a phenomenon
known as the Charles Bonnet Syndrome. Most who have it keep their
mouth shut, however, and perhaps with good reason. People with Charles
Bonnet Syndrome see things that aren’t there.
Everyday household objects suddenly pop into view. Or unfamiliar
people unexpectedly appear next to them at dinner. Neurologist Vilayanur
Ramachandran describes the case of a woman who suddenly—and
delightfully—observed two tiny policemen scurrying across the floor,
guiding an even smaller criminal to a matchbox-size van. Other patients
have reported angels, goats in overcoats, clowns, Roman chariots, and
elves. The illusions often occur in the evening and are usually quite benign.
Charles Bonnet Syndrome is common among the elderly, especially among
those who previously suffered damage somewhere along their visual
pathway. Interestingly, almost all of the patients know that the
hallucinations aren’t real.
A camel in each eye
Besides filling in our blind spots and creating bizarre dreams, the brain
has another way of participating in our visual experience. We have two
eyes, each taking in a full scene, yet the brain creates a single visual
perception. Since ancient times, people have wondered why. If there is a
camel in your left eye and a camel in your right eye, why don’t you
perceive two camels? Here’s an experiment to try that illustrates the issue
nicely.
1) Point your left index finger to the sky. Touch your nose and then
stretch your left arm out.

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2) Point your right index finger to the sky. Touch your nose and then
move your finger about six inches away from your face.
3) Both fingers should be in line with each other, directly in front of
your nose.
4) Now speedily wink your left eye and then your right one. Do this
several times, back and forth. Your right finger will jump to the other side
of your left finger and back again. When you open both eyes, the jumping
will stop.
This little experiment shows that the two images appearing on each
retina always differ. It also shows that both eyes working together give the
brain enough information to create one stable picture. One camel. Two non-
jumping fingers. How?
The brain interpolates the information coming from both eyes. Just to
make things more complicated, each eye has its own visual field, and they
project their images upside down and backward. The brain makes about a
gazillion calculations, then provides you its best guess. And it is a guess.
You can actually show that the brain doesn’t really know where things are.
Rather, it hypothesizes the probability of what the current event should look
like and then, taking a leap of faith, approximates a viewable image. What
you experience is not the image. What you experience is the leap of faith.
The brain does this because it needs to solve a problem: The world is
three-dimensional, but light falls on the retina in a two-dimensional fashion.
The brain must deal with this disparity if it is going to portray the world
with any accuracy. To make sense of it all, the brain is forced to start
guessing. Upon what does the brain base its guesses, at least in part?
Experience with past events. After inserting numerous assumptions about
the visual information (some of these assumptions may be inborn), the brain
then offers up its findings for your perusal. Now you see one camel when
there really is only one camel—and you see its proper depth and shape and
size and even hints about whether it will bite you.
Far from being a camera, the brain is actively deconstructing the
information given to it by the eyes, pushing it through a series of filters, and
then reconstructing what it thinks it sees. Or what it thinks you should see.
All of this happens in about the time it takes to blink your eyes. Indeed, it is
happening right now. If you think the brain has to devote to vision a lot of

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its precious thinking resources, you are right on the money. Visual
processing takes up about half of everything your brain does, in fact. This
helps explain why professional wine tasters toss aside their taste buds so
quickly in the thrall of visual stimuli. And why vision affects other senses,
too.
Vision trumps touch, not just smell and taste
Amputees sometimes continue to experience the presence of their limb,
even though the limb no longer exists. In some cases, the limb is perceived
as frozen into a fixed position. Sometimes the person feels pain in the limb.
Studies of people with phantom limbs demonstrate the powerful influence
vision has on our other senses.
In one experiment, an amputee with a “frozen” phantom arm was seated
at a table upon which had been placed a lidless box divided in half. The box
had two portals in the front, one for the arm and one for the stump. The
divider was a mirror on both sides. So the amputee could view a reflection
of either his functioning hand or his stump. When the man looked down
into the box, he could see his right arm present and his left arm missing. But
when he looked at the reflection of his right arm in the mirror, he saw what
looked like another arm. Suddenly, the phantom limb on the other side of
the box “woke up.” If he moved his normal hand while gazing at its
reflection, he could feel his phantom move, too. And when he stopped
moving his right arm, he felt his missing left arm stop also. The addition of
visual information began convincing his brain of a miraculous rebirth of the
absent limb.
A picture really is worth a thousand words
One way we can measure the dominance of vision is to look at its effect on
learning. Researchers study this using two types of memory.
The first is called recognition memory, which underlies the concept of
familiarity. We often deploy recognition memory when looking at old
family photographs. Maybe you see a photo of an aunt not remembered for
years. You don’t necessarily recall her name, or the photo, but you still
recognize her as your aunt. With recognition memory, you may not recall

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certain details surrounding whatever you see, but as soon as you see it, you
know that you have seen it before.
The second involves working memory. Explained in greater detail in the
Memory chapter, working memory is that collection of temporary storage
buffers with fixed capacities and frustratingly short life spans. Visual short-
term memory is the slice of that buffer dedicated to storing visual
information. Most of us can hold the memory of about four objects at a time
in that buffer, so it’s a pretty small space. And it appears to be getting
smaller. As the complexity of objects in our world increases, we are capable
of remembering fewer objects over our lifetimes. Evidence also suggests
that the number of objects and complexity of objects are engaged by
different systems in the brain—turning the whole notion of short-term
capacity, if you will forgive me, on its head. These limitations make it all
the more remarkable that vision is probably the best single tool we have for
learning anything.
When it comes to both recognition memory and working memory,
pictures and text follow very different rules. Put simply, the more visual the
input becomes, the more likely it is to be recognized—and recalled. It’s
called the pictorial superiority effect. Researchers have known about it for
more than 100 years. (This is why we created a series of videos and
animations of the Brain Rules at