I
am currently reading Incognito: The
Secret Lives of the Brain by David Eagleman. It is one of several books
based on modern psychology that give us new insights into what our brains are
like—insights that are both disturbing and liberating.
I
already knew that the brain does not present us with an objective picture of
reality. I thought that it processes sensory information into a model of reality, one in which the
information from the environment is presented to us in a useful fashion. For
example, I knew about sensory fatigue, in which an unchanging sensory input is
soon ignored by the brain. This keeps the conscious brain from being
overwhelmed by information. I also knew that color is an illusion. The brain
uses inputs from three kinds of retinal cones to create a false-color picture
of the environment, one in which ripe fruits are red so that they can be easily
spotted by hungry animals without having to think about the complex mixture of
wavelengths reflected from the environment.
And
this is what I have been teaching my classes for almost three decades. But it
turns out I might be wrong about this. The brain does not, apparently, process
sensory information into a model of reality. Instead, our brains (according to
Eagleman) internally generate a
picture of reality. That is, what we see, hear, and feel is a model that the
brain generates from its own memories and expectations. The brain uses sensory
input only to modify and adjust this
model as needed.
I
took a walk in the woods this morning. It was the perfect time for a walk on
Turkey Mountain, just outside of Tulsa. A Tuesday morning is almost the only
time the parking lot is not full. The temperature was perfect, the sunlight was
clear, and the leaves were light green, soft, and profuse (they will later be
dark green, hard, and scraggly). It was also the last time for a while: the
abundant rains that have suddenly filled our low reservoirs will return
tomorrow. I walked on trails I have explored dozens of times. My mind pretty
much knew where to make my body go. My mind utilized sensory input only to
modulate where my feet moved so as to position themselves correctly on the
rocks that my subconscious mind probably already knew were there. I could not
have walked blindfolded, but just a few visual data are all that were necessary
to allow me to walk—a few more than usual, since I had to avoid mud holes that
others before me had not, and fallen branches and trunks.
Every
person who was on the trail had a different mental image of it. Some joggers noticed
only where the rocks and mud were, as they ran along listening to headphones.
Some hikers saw little more than this, perhaps being aware of the vaulted
canopy of branches overhead, as they concentrated mainly on their own animated
conversations. The brains of dirt bikers had to do quick calculations of
velocity and momentum, not having time to notice anything else.
And
then there was me, the botanist. I noticed all the different kinds of trees: no
matter how many times I see them, I feel like they are old friends. I wonder
how many other hikers realize just how many kinds of trees there are. I also
noticed the spatial patterns of the trees: the post oaks in higher and drier
spots, the red oaks in the lower and wetter spots. I also noticed that poison
ivy and aromatic sumac (with which it can be easily confused) never grow in
exactly the same place, the former preferring shadier and wetter microclimates.
Moreover, pollinating insects do not get poison ivy and smooth sumac (whose
flowers look almost alike) mixed up since poison ivy is blooming right now and
the smooth sumac flowers won’t open until at least next week; and they cannot
confuse either of these with aromatic sumac, whose flowers open before any of
the leaves have come out.
Here
are photos of poison ivy flowers, and the gigantic leaves!
I
also notice the bark of each tree. My daughter thinks I have a picture of every
tree trunk in Oklahoma, but I know I’ve missed more than half of them. Bark is
beautiful, each species having its own kind, each life stage having its own
kind, and each tree having bark that reflects its own personal story of
experience, growth, and recovery, as in this post oak that has had to start its
life over again at least twice:
I
see the forest as a functioning system in space and time, rather than as a
backdrop for my own human activities. My brain noticed all these things because
I consciously decided to look for them.
But
my brain ignored a lot of things that other scientists could have pointed out to
me. I am sure there were lots of insects, and insect galls, that I did not even
see. To me, an insect-damaged leaf was one to ignore when taking photos,
instead of a vital piece of information to understand the food chain of the
forest. It was only by chance that I noticed a wild bee pollinating a Phacelia flower.
As
for birds, you have to look closely to see the indigo buntings, whose blue
backs appear black at first glance. A geologist would be able to explain how
processes millions of years ago produced sandstone in some places, and shale in
others, on what is now Turkey Mountain, and until recently I walked right past
fossilized impressions and even petrified wood of prehistoric lepidodendrid
trees without even seeing them. My brain was in plant mode just as the joggers’
brains were in don’t-slip-in-the-mud mode. I, too, entered the forest with an
internally-generated model of what it was supposed to be like.
I
would like to leave you with this thought. You can always enjoy a place more if
you look closely and start noticing things. If you keep your brain in
energy-savings mode, so that it responds only to threats and inconveniences,
you are missing the joy of being alive.
Of course, I do not need to say this to anyone who is reading this essay right
now! And the people who come to the forest only to jog might, in fact, find
themselves surprised and pleased at discovering something about the forest
through which they had merely intended to run.
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