October 16, 2023 • 42 mins
Can we explain our rich experience of life only by studying the molecules that compose us? How is the color of your passport related to your chances of presenting with schizophrenia? Males are more predisposed to commit crime, so why don’t all males commit crime? And what does any of this have to do with traffic jams, why Seinfeld is funny, and how we’re ever going to come to know ourselves from studying biology? Join Eagleman to talk about levels of understanding, what a meaningful explanation would look like, and the possibility that we are not near the conclusion of science's journey, but instead near the beginning.
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Speaker 1 (00:05):
Can we explain our consciousness just by looking at the
molecules in our brain? How is the color of your
passport related to whether you get schizophrenia? Males are more
predisposed to commit crime, so why don't all males commit crime?
And what does any of this have to do with
traffic jams, or why Seinfeld is funny? Or how we're
(00:28):
ever going to come to know ourselves from studying our biology.
Welcome to the Inner Cosmos with me David Eagleman. I'm
a neuroscientist and an author at Stanford and in these
episodes we sail deeply into our three pound universe to
examine the intersection of our brains in our lives. Today
(01:00):
episode is part two of the question of knowing Thyself.
So last week we talked about how we know with
certainty that our consciousness our essence is tied to our
biology and the possibility that we are nothing but our biology.
In this episode, I want us to expand our imagination
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even more and consider ourselves in the context of people
not at the conclusion of science's journey, but instead is
people just some distance along the path who are facing
hundreds or thousands of years of research ahead. Of us,
and specifically, I want to be clear eyed about the
challenges and possibly the impossibility of trying to explain our
(01:47):
experience of life in terms of the interaction of molecules.
So in this episode, we're going to talk about levels
of understanding and what a meaningful explanation would look like. Okay,
so you remember the Human Genome project, in which our
(02:09):
species successfully decoded the billions of letters long sequence in
our own genetic cookbook. Now, that project was a massive
landmark achievement for us, and almost everyone has heard of
the Human Genome project, but not everyone knows that in
some ways the project was a failure because we sequenced
(02:32):
the whole code, but once we got there, we didn't
find the hoped for breakthrough answers about the genes that
are unique to humankind. Instead, what we discovered was a
massive recipe book for building the nuts and bolts of
biological organisms. We found that other animals have essentially the
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same genome that we do, and this is because they
are made of the same nuts and bolts, only in
slightly different configurations. The human genome is not terribly different
from the squirrel genome or the tunafish genome, even though
humans are terribly different from squirrels and tunafish. At least,
humans and these other animals seem quite different at first,
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but keep in mind that all of them require the
recipes to build eyeballs and spleens and skin and bones
and hearts and so on, so as a result, the
genomes are not so dissimilar. Imagine going to different factories
and examining the pitches and lengths of the screws that
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are used. This would tell you very little about the
function of the final product. Say if it's a toaster
versus a blow dryer, both assemble similar elements to achieve
different functions. Now, the fact that we didn't learn what
we thought we might is not a criticism of the
human genome project. It was an enormously important first step.
(04:02):
But what this does tell us is that successive levels
of reduction are typically going to tell us very little
about the questions important to humans. So in the last episode,
we introduced this question of whether we can understand ourselves
by an approach called reductionism. Reductionism is the idea that
(04:26):
we can successively reduce the problems down to their small
scale biological pieces and parts, and eventually come to explain
complex phenomena like thinking and consciousness by understanding the molecules. Now,
there's been a lot of excitement about this possibility for
a long time in neuroscience. For example, in the last episode,
(04:50):
I mentioned Huntington's disease, which is a disorder that's caused
by a mutation in a single gene, and in fact
it was the first gene pulled for a disease, which
seemed like a great success story for reductionism. If you
have this gene, you'll get this disease. But note that
Huntington's is one of the very few examples that can
(05:13):
be dredged up for this sort of one to one mapping.
The reduction of a disease to a single mutation is
extraordinarily rare. Most diseases are polygenetic, meaning that they result
from subtle contributions of tens or hundreds of different genes,
(05:34):
and as science develops better techniques, we're discovering that not
just the coding regions of the genes matter, but also
the areas in between what used to be thought of
as junk DNA. Most diseases seem to result from a
perfect storm of numerous minor changes that combine in dreadfully
(05:57):
complex ways. The challenge to reductionism is far worse than
just a multiple genes problem. The contributions from the genome
can really be understood only in the context of interaction
with the environment. So consider schizophrenia, a disease for which
(06:19):
teams of researchers have been gene hunting for decades. Now
have they found any genes that correlate with the disease?
Sure they have hundreds. In fact, does the possession of
any one of these genes offer much in the way
of prediction about who will develop schizophrenia as a young adult.
(06:39):
Very little. No single gene mutation is as predictive of
schizophrenia as the color of your passport. What does your
passport have to do with schizophrenia? It turns out that
the social stress of being an immigrant to a new
country is one of the critical factors in developing schizophrenia.
(07:02):
In studies across countries, immigrant groups who differ the most
in culture and appearance from the host population carry the
highest risk of schizophrenia. In other words, a lower level
of social acceptance into the majority correlates with a higher
chance of a schizophrenic break in ways not fully understood.
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It appears that repeated social rejection perturbs the normal functioning
of the dopamine systems. But even these generalizations don't tell
the whole story, because within a single immigrant group, say
Koreans in America, those who feel worse about their ethnic
differences from the majority are more likely to become psychotic.
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Those who are proud and comfortable with their heritage are
mentally safer. Now this news comes as a surprise to many.
Isn't schizophrenia a genetic disorder? The answer is that genetics
play a role. If the genetics make nuts and bolts
that have a slightly altered shape, the whole system may
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run in an unusual manner when put in particular environments.
In other environments, the shape of the nuts and bolts
may not matter. When all is said and done, how
a person turns out depends on much more than the
molecular suggestions written down in the DNA. You may remember
(08:32):
that in an earlier episode on neurolaw, I mentioned that
some people have an eight hundred and twenty eight percent
higher chance of committing a violent crime if they carry
a certain set of genes. And those genes you may
remember are summarized as the Y chromosome. If you are
(08:52):
a carrier, we call you a male. Now that correlation
between the Y chromosome and crime is fact, But the
important question to ask is this, why aren't all males criminals?
In fact, there's only one percent of males that get incarcerated.
So what's going on the answer is that knowledge of
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the genes alone is not sufficient to tell you much
about behavior. Consider the work of Stephen Swomy. He's a
researcher who raises monkeys in natural environments in Maryland. Now,
in his natural environment setting, he can observe the monkey's
social behavior from their day of birth, and one of
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the first things he noticed was that monkeys begin to
express different personalities from a surprisingly early age. He saw
that virtually every social behavior was developed and practiced and
perfected during the course of peer play by four to
six months of age. Now this observation would have been
(09:56):
interesting by itself, but Swomy was able to combine the
behavior observations with regular blood testing of hormones and metabolites,
as well as genetic analysis. What he found were that
five percent of the baby monkeys were overly aggressive. They
showed impulsive and inappropriately belligerent behavior. Those monkeys had low
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levels of a blood metabolite related to the neurotransmitter serotonin.
Now here's the key. Swomi and his team found that
there were two different flavors of genes. These are called
alleles that one could possess for a protein that's involved
in transporting serotonin. Let's just call these the short and
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the long forms. Now, the monkeys with the short form
showed poor control of violence, while those with the long
form displayed normal behavioral control. But that turned out to
be only part of the story. How a monkey's personality
developed depended on its environment as well. So there were
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two ways the monkeys could be reared, either with their mothers,
which was a good environment, or with their peers, which
was called an insecure attachment relationship environment. So the monkeys
with the short form ended up as the aggressive type
when they were raised with their peers, but they did
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much better when they were raised with their mothers. For
those with the long form of the gene, the rearing
environment didn't seem to matter much. They were well adjusted
in either case. Now, there are at least two ways
to interpret these results. The first is that the long
allele is a good gene that gives resilience against a
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bad childhood environment. The second way you could interpret this
is that you have some monkeys who would have turned
out to be bad seeds, but they were rescued by
good mothering. Now these two interpretations aren't exclusive, and we
don't know which one is exactly correct, but they boiled
down to the same important lesson. A combination of genetics
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and environment matters for the final outcome. So, following on
from these monkey studies, people started to study gene environment
interactions in humans. In two thousand and one, a researcher
named av Shalom Caspi and his colleagues set out to
ask whether there are genes for depression. When they went
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on the hunt, they found that the answer is sort of.
They learned that there are genes that predispose you, but
whether you actually suffer from depression depends on your life's events.
The researchers discovered this by carefully interviewing dozens of people
to find out what sort of major traumatic events had
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transpired in their lives. The loss of a loved one,
a major car accident, and that sort of thing. So
for each participant, they also analyzed the genetics, specifically the
form of a gene involved in regulation of serotonin levels
in the brain. Because people carry two copies of the gene,
one from each parent, there are three possible combinations that
(13:14):
someone might carry, a short short, a short long, or
a long long. The amazing result they found was that
the short short combination predisposed the participants to clinical depression,
but only if they experienced an increasing number of bad
life events. If they were lucky enough to have a
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good life, then carrying the short short combination made them
no more likely than anyone else to become clinically depressed.
But if they were unlucky enough to run into serious troubles,
including events that were entirely out of their control, then
they were more than twice as likely to become depressed
as someone with the long long combination. So whether somebody
(14:00):
sense with depression is a matter of their genes and
their life circumstances. Now, Caspy's group then did an entirely
(14:24):
different second study to address a deep societal concern. Do
children who are abused grow up to become child abusers themselves?
Many people believe this statement, but is it really true
and does it matter what kind of genes the child carries.
What caught the attention of the researchers was the fact
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that some abused children become violent as adults, but other
abused children do not. When all the obvious factors were
controlled for. The fact stood that childhood abuse by itself
does not predict how an individual would turn out. So
inspired to understand the difference between those who perpetrate the
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violence and those who don't, Caspian his colleagues discovered that
a small change in the expression of a particular gene
is what differentiated these two groups. Children with low expression
of the gene were more likely to develop conduct disorders
and become violent criminals as adults, but this bad outcome
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was much more likely if the children were abused. If
they harbored the let's call it the bad forms of
the gene, but had been spared childhood abuse, they were
not likely to become abusers. And if they harbored the
good form of the gene, then even a childhood of
severe maltreatment would not necessarily drive them to continue the
(15:54):
cycle of violence. And let me give a third example
of the interaction of gene an environment, and this one
comes from the observation that smoking cannabis marijuana as a
teenager increases the probability of developing psychosis as an adult.
But this connection is true only for some people and
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not for others. By this point you can guess the
punch I'm going to say, which is that a genetic
variation underlies one's susceptibility to this. With one combination of alleles,
there's a strong link between cannabis use and adult psychosis.
With a different combination, the link is weak. And here's
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another example. The psychologists Angelos Scarpa and Adrian Rain measure
differences in brain function among people diagnosed with antisocial personality disorder,
which is characterized by a total disregard for the feelings
and rights of other people. And antisocial personality disorder, or ASPD,
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is highly prevalent among the criminal population. So the researchers
found that ASPD had the highest likelihood of occurring when
brain abnormalities were combined with a history of adverse environmental experiences.
In other words, if you have certain problems with your brain,
but you are raised in a good home, you might
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turn out fine. If your brain is fine and your
home is terrible, you might still turn out fine. But
if you have mild brain damage and end up in
a bad home life, you're tossing the dice for a
very unlucky synergy. All these examples demonstrate that it is
neither biology alone nor your environment alone that determines the
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final product of a personality. When it comes to the
nature versus nurture question, the answer almost always includes both.
Now importantly, you don't choose your nature and you don't
choose your nurture much less they're entangled interaction. You inherit
a genetic blueprint, and you're born into a world over
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which you have no choice throughout your most formative years.
This is the reason people come to the table with
quite different ways of seeing the world, and dissimilar personalities
and varied capacities for decision making. These are not choices.
These are the hand of cards that you're dealt. The
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point of episode fifteen about neurolaw was to highlight the
difficulty of assigning culpability under this circumstance of you choosing
neither your genes or your environment. The point of this
episode is to highlight the fact that the machinery that
makes us who we are is not simple, and that
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science is not perched on the verge of understanding who
you are and exactly how you came to be that way.
So where we are is this weird place where we
know without a doubt that minds and biology are connected,
but we're not going to have any hope of understanding
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that connection with a purely reductionist approach. Reductionism is misleading
for two reasons. First, as we've just seen, the unfathomable
complexity of gene environment interactions puts us a long way
from understanding how any individual person, with her lifetime of
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experiences and conversations and abuses and joys and foods she's eaten,
and recreational drugs and prescribed medications and pesticides and educational
experience and so on, we have no idea how she's
going to develop as an individual. It is simply too complex,
and presumably it is going to remain too complex. The
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second reason reductionism is misleading is that even while it's
true that we are tied to our molecules and proteins
and neurons, as strokes and hormones and drugs and microorganisms
indisputably tell us, it doesn't logically follow that humans are
best described only as pieces and parts. Like that, the
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extreme reductionist idea that we are no more than the
cells of which we are composed is a non starter
for anyone trying to understand human behavior. Just because a
system is made of pieces and parts, and just because
those pieces and parts are critical to the working of
the system, that does not mean that the pieces and
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parts are the correct level of description. And I'll give
a few examples of that in a moment. So, given
these shortcomings of reductionism, why did it catch on in
the first place. To understand this, we just need to
look at the historical roots. Over recent centuries, thinking people
watched the growth of deterministic science around them in the
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form of the equations of Galileo and Newton and others.
These scientists pulled springs and rolled balls and dropped weights,
and increasingly they were able to predict what the objects
were going to do with simple equations. So by the
nineteenth century, Pierre Simon Laplace had proposed that if one
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could know the position of every particle in the universe,
then one could compute forward to know the entire future
and crank the equations the other way to know everything
in the past, this deterministic approach was massively successful. It
predicted the flight of cannon balls and the movement of planets,
and that success was at the heart of biological reductionism.
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The idea is that big things can be understood by
discerning smaller and smaller pieces. In this viewpoint, the eras
of understanding all point to the smaller levels humans can
be understood in terms of biology, biology, the language of chemistry, chemistry,
and the equations of atomic physics. In many ways, reductionism
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has been the engine of science for the past four
hundred years, and in most fields it has done a
great job. But reductionism isn't the right viewpoint for everything,
and it certainly won't explain the relationship between the brain
and the mind. This is because of a feature known
as emergence. When you put together large numbers of pieces
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and parts, the whole can become something greater than the sum.
None of the individual hunks of an airplane have the
property of flight, but when they are attached together in
the right way, the result takes to the air. A
thin metal bar won't do you much good if you're
trying to control a jaguar, but several of them in
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parallel standing up have the property of containment. This concept
of emergent properties means that something new can be introduced
that is not inherent in any of the parts. As
another example, imagine that you were an urban highway planner
and you needed to understand your city's traffic flow. You
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need to understand where the cars tend to bunch up,
where people speed, where the most dangerous attempts at passing occur.
It won't take you long to realize that an understanding
of these issues will require some model of the psychology
of the drivers. You would lose your job if you
propose to study the length of the screws and the engine,
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or the combustion efficiency of the spark plugs. Those are
the wrong levels of description for understanding traffic jams. This
is not to say that the small pieces don't matter.
They do matter. As we saw with brains, adding narcotics,
or changing neurotransmitter levels or mutating genes, this can radically
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all alter the essence of a person. And similarly, if
you modify screws and spark plugs, the engines work differently,
and the cars might speed up or slow down, and
other cars might crash. Into them, so the conclusion is clear.
While traffic flow depends on the integrity of the parts,
it is not in any meaningful way equivalent to the parts.
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Or think of it this way. If you want to
know why the TV show Seinfeld is funny, you won't
get very far by studying the transistors and capacitors in
the back of your TV. You might be able to
list all the electronic parts in great detail, and you'll
probably learn a thing or two about electricity, but that
won't get you any closer to understanding hilarity. Enjoying Seinfeld
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depends entirely on the integrity of the transistors, but the
parts are not themselves funny. And it's exactly the same
with neuros science. While minds depend on the integrity of
the neurons, neurons are not themselves thinking and feeling, and
this forces a reconsideration of how to build a scientific
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account of the brain. If we were to work out
a complete physics of neurons and their chemicals, would that
explain the mind? Probably not. The brain presumably does not
break any of the laws of physics, but that doesn't
mean that equations describing biochemical interactions will amount to the
correct level of description, as the complexity theorist Stuart Kaufman
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puts it, quote, a couple in love walking along the
banks of the sin are in fact a couple in
love walking along the banks of the sin, not mere
particles in motion unquote. So in the same way, a
meaningful theory of human biology can't be reduced to chemistry
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and physics. Instead, it has to be understood in its
own vocabulary of evolution and competition and reward and desire
and reputation and greed and friendship and trust and hunger
and so on, in the same way that traffic flow
is not going to be understood in the vocabulary of
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screws and spark plugs, but instead in terms of speed
limits and rush hours and road rage and people wanting
to get home to their families as soon as possible
when their workday is over. And there's another reason why
the neural pieces and parts won't be sufficient for a
full understanding of human experience, and that is your brain
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is not the only biological player in the game of
determining who you are. The brain is tied in constant
two way communication with the endocrine and immune systems, which
can be thought of as the greater nervous system. The
greater nervous system is in turn inseparable from the chemical
environments that influence its development, including nutrition and lead paint
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and air pollutants and so on and even more. You
are part of a complex social network that changes your
biology with every interaction, and which your actions can change
in return. This makes the borders interesting to contemplate. How
should we define you? Where do you begin and where
do you end? The only solution, I think is to
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consider the brain the densest concentration of unice. It's the
peak of the mountain, but it's not the whole mountain.
When we look at behavior and we talk about the
role of the brain, this is actually a shorthand label
that includes contributions from a much broader system, what we
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often call a psychobiosocial system. The brain is not so
much the seat of the mind as the hu ubb
of the mind. So let's summarize where we are following
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a one way street in the direction of the very
small is the mistake that reductionism can make, and it's
a trap that we want to avoid. Whenever you see
a shorthand statement such as you are your brain which
I say sometimes don't take that to mean that neuroscience
will understand minds only as massive constellations of atoms or
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vast jungles of neurons. Instead, the future of understanding the
mind lies in deciphering the patterns of activity that live
on top of the wetwear, and these patterns are directed
both by the internal workings and by interactions from the
surrounding world. So laboratories all over the world are working
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to figure out how to understand the relationship between physical
matter and subjective experience, but it's far from a solved
problem now. In the early nineteen fifties, the philosopher Hans
Reichenbach stated that humanity was poised before a complete scientific,
objective account of the world, a scientific philosophy. Now that
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was over seventy years ago. Have we arrived, not yet anyway,
and in fact we're a long way off. For some people.
The game is to act as those sciences just on
the brink of figuring everything out. And indeed there's great
pressure on scientists from granting agencies and popular media to
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pretend as though the major problems are about to be
solved at any moment. But the truth is that we
face a field of question marks, and this field stretches
to the vanishing point. This suggests an entreaty for openness
while exploring these issues. As one example, the field of
quantum mechanics includes the concept of observation, when an observer
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measures the location of a photon that collapses the state
of the particle to a particular position while a moment
ago it was in an infinity of possible states. What
is it about observation? Do human minds interact with the
stuff of the universe? This is a totally unsolved question
in science, and one that may somehow provide a critical
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meeting ground between physics and neuroscience. Now, most scientists currently
approach the two fields as separate, and researchers who try
to look more deeply into the connections between them often
end up marginalized. I mentioned in a previous episode that
sometimes scientists will make fun of the pursuit by saying
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something like quantum mechanics is mysterious and consciousness is mysterious,
therefore they must be the same thing. Haha. Now that
kind of dismissiveness is actually bad for the field. To
be really clear, I'm not asserting there is a connection
between quantum mechanics and consciousness. I am saying we can't
rule out yet that there is a connection, and that
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a premature dismissal is not in the spirit of scientific
inquiry and progress. When people assert that brain function can
be completely explained by classical physics, it's important to recognize
that that is simply an assertion. It's difficult to know
in any age of science what pieces of the puzzle
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were missing. As an example, I'll mention what I call
the radio theory of brains, which I mentioned in episode seventeen.
Imagine that you are a primitive tribesman somewhere and that
you stumble upon a transistor radio in the sand. You've
never seen something like this before, so you might pick
it up and you twiddle the knobs, and suddenly, to
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your surprise, you hear voices streaming out of this strange
little device. If you are curious and scientifically minded, you
might try to understand what's going on. So you might
pry off the back cover and you discover a little
nest of wires. Now, let's say you begin a careful
scientific study of what causes the voices, and you notice
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that each time you pull out the green wire, the
voices stop, and when you put the wire back on
its contact, the voices begin again. The same goes for
the red wire. Yanking out the black wire causes the
voice to get garbled, and removing the yellow wire reduces
the volume to a whisper. So you step carefully through
all the combinations, and you come to a clear conclusion.
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The voices depend entirely on the integrity of the circuitry.
Change the circuitry and you damage the voices. So you're
proud of your new discoveries, and you devote your life
to developing a science of the way in which certain
configurations of wires create the existence of magical voices. At
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some point, a young person asks you how some simple
patterns of wires can engender conversations and music, and you
admit that you don't exactly know, but you insist that
your science is about to crack that problem at any moment.
But your conclusions are limited by the fact that you
know absolutely nothing about radio waves, and more generally about
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electromagnetic radiation, or the fact that there are structures in
distant cities called radio towers, which sends signals by perturbing
invisible waves that travel at the speed of light. It
is so foreign to you that you couldn't even dream
that up. You can't taste radio waves, and you can't
see them, you can't smell them, and you don't yet
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have any pressing reason to be creative enough to fantasize
about them. And if you did dream of invisible radio
waves that carry voices, who are you going to convince
of your hypothesis. You have no technology to demonstrate the
existence of the waves, and everybody justifiably points out to
you that the onus is on you to convince them.
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So you would become a radio materialist. You would conclude
that somehow the right configuration of wires engenders classical music
and intelligent conversation. You wouldn't realize that you're missing an
enormous piece of the puzzle. Now, to be clear, I
am not asserting that the brain is like a radio,
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that we are receptacles picking up signals from elsewhere, and
that our neural circuitry needs to be in place to
do so. But I am noting that things like this
could be true. There's nothing in our current science that
rules this out, and knowing as little as we do
at this point, in history, we have to retain concepts
like this in the large filing cabinet of ideas that
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we cannot yet rule in favor of or against. So,
even though very few working scientists will design experiments around
eccentric hypotheses, ideas always need to be proposed and nurtured
as possibilities until evidence weighs in one way or another. Now,
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we scientists will often talk about the parsimony of an explanation,
which means is this simplest way to explain something? Can
I come up with an explanation that doesn't add anything
extra that's not needed? And you've probably heard this idea
of Okham's razor, which is simply a statement that the
simplest explanation is probably correct. It's a very useful tool
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to keep in mind to make sure that your hypothesis
doesn't have a bunch of extra baggage that's not useful.
But we shouldn't get seduced by the apparent elegance of
argument from parsimony, because that line of reasoning has failed
in the past at least as many times as it succeeded.
For example, it is more parsimonious to assume that the
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sun goes around the Earth. It's more parsimonious to suggest
that tiny atoms follow the same rules as objects at
larger scales. It's more parsimonious to suggest that what we
perceive is really what's out there. All of these positions
were long defended by argument from parsimony, and they were
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all incorrect. In my view, the argument from parsimony is
really not an argument at all. Is typically used just
to shut down discussion that sometimes shouldn't be shut down.
If history is any guide, it's never a good idea
to assume that a scientific problem is cornered at this
moment in history. I'd say that many or most in
(36:52):
the neuroscience community subscribe to materialism and reductionism. And when
my colleagues and I design experiment and so, we sort
of have to make this assumption. And what it means
is that we should be understandable as a collection of
cells and blood vessels and hormones and proteins and fluids,
all following the basic laws of chemistry and physics as
we currently understand them. Each day, neuroscientists go into laboratory
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and work under the assumption that understanding enough of the
pieces and parts will given understanding of the whole. This
break it down to the smallest bits approach is the
same successful method that has been employed in physics and
chemistry and the reverse engineering of electronic devices, But we
(37:37):
don't have any real guarantee that this approach will work
in neuroscience. The brain, with its private, subjective experience, is
unlike any of the problems that we've tackled so far,
and anybody who tells you that we have the problem
cornered with a reductionist approach doesn't actually understand the complexity
(37:59):
of the problem. Keep in mind that every single generation
before us has worked under the assumption that they possessed
all the major tools for understanding the universe, and they
were all wrong without exception. Just imagine trying to construct
a theory about rainbows before the understanding of optics, Or
(38:21):
imagine trying to understand lightning before the knowledge of electricity,
or imagine trying to understand Parkinson's disease before the discovery
of neurotransmitters. Does it seem reasonable that we are the
first ones lucky enough to be born in the perfect generation,
the one in which the assumption of a comprehensive science
(38:42):
is finally true, or does it seem more likely that
in one hundred years from now people will look back
on us and wonder what it was like to be
ignorant of what they now know. Just to be very
clear on this point, I am not claiming that materialism
is incorrect, or even suggesting that I hope it's incorrect.
After all, even a materialist universe would be mind blowingly amazing.
(39:08):
Imagine for a moment that we are nothing but the
product of billions of years of molecules coming together and
ratcheting up through natural selection. That we are composed only
of highways of fluids and chemicals sliding along roadways within
billions of dynamic cells. Imagine that trillions of synaptic conversations
(39:30):
are flashing in parallel, and that this vast fabric of
micron thin circuitry runs algorithms that are totally undreamt of
in modern science, and that these neural programs give rise
to our decision making and loves and desires and fears
and aspirations. To me, that understanding would be a numinous experience,
(39:55):
better than anything ever proposed in anyone's holy text. Whatever
else exists beyond the limits of our current science is
an open question for future generations. But even if strict
materialism turned out to be it, that would be enough.
So to wrap up this week's episode, I'm going to
turn to a famous quip from the great sci fi
(40:17):
writer Arthur C. Clark. He pointed out that any sufficiently
advanced technology is indistinguishable from magic. I don't view the
massive complexity we face in neuroscience as depressing. I view
it as magic. We're already seeing in this podcast series
that everything contained in the biological bags of fluid we
(40:39):
call us is already so far beyond our intuition, beyond
our capacity to think about such vast scales of interaction,
beyond our introspection, that this fairly qualifies is something beyond us.
The complexity of the system that we are is so
vast as to be indistinguishable from Clark's magical technology. As
(41:05):
the saying goes, if our brains were simple enough to
be understood, we wouldn't be smart enough to understand them.
I wrapped my book Incognito years ago by pointing out that,
in this same way that the cosmos is larger than
we ever imagined, we ourselves are something greater than we
had intuited simply by introspection, and we're now getting the
(41:28):
first glimpses of the vastness of this inner space, this internal, hidden,
intimate cosmos. It has its own goals, imperatives, and logic.
It's an organ that feels alien and outlandish to us,
and yet its detailed wiring patterns sculpt the landscape of
(41:52):
our inner lives. What a perplexing masterpiece our brain is,
and how lucky we are to be in a generation
that has the technology and the will to turn our
attention to it. It is the most wondrous thing we
have discovered in the universe, and it is us to
(42:15):
find out more and to share your thoughts. Head over
to Eagleman dot com slash podcasts. Send me an email
at podcasts at eagleman dot com with questions or discussion,
and I'll be making episodes in which I address those
and you can watch full episodes of Inner Cosmos on YouTube.
Subscribe to my channel so that you can follow along
each week for new updates until next time. I'm David Eagleman,
(42:38):
and this is Inner Cosmos.
Can we explain our consciousness just by looking at the
molecules in our brain? How is the color of your
passport related to whether you get schizophrenia? Males are more
predisposed to commit crime, so why don't all males commit crime?
And what does any of this have to do with
traffic jams, or why Seinfeld is funny? Or how we're
(00:28):
ever going to come to know ourselves from studying our biology.
Welcome to the Inner Cosmos with me David Eagleman. I'm
a neuroscientist and an author at Stanford and in these
episodes we sail deeply into our three pound universe to
examine the intersection of our brains in our lives. Today
(01:00):
episode is part two of the question of knowing Thyself.
So last week we talked about how we know with
certainty that our consciousness our essence is tied to our
biology and the possibility that we are nothing but our biology.
In this episode, I want us to expand our imagination
(01:22):
even more and consider ourselves in the context of people
not at the conclusion of science's journey, but instead is
people just some distance along the path who are facing
hundreds or thousands of years of research ahead. Of us,
and specifically, I want to be clear eyed about the
challenges and possibly the impossibility of trying to explain our
(01:47):
experience of life in terms of the interaction of molecules.
So in this episode, we're going to talk about levels
of understanding and what a meaningful explanation would look like. Okay,
so you remember the Human Genome project, in which our
(02:09):
species successfully decoded the billions of letters long sequence in
our own genetic cookbook. Now, that project was a massive
landmark achievement for us, and almost everyone has heard of
the Human Genome project, but not everyone knows that in
some ways the project was a failure because we sequenced
(02:32):
the whole code, but once we got there, we didn't
find the hoped for breakthrough answers about the genes that
are unique to humankind. Instead, what we discovered was a
massive recipe book for building the nuts and bolts of
biological organisms. We found that other animals have essentially the
(02:55):
same genome that we do, and this is because they
are made of the same nuts and bolts, only in
slightly different configurations. The human genome is not terribly different
from the squirrel genome or the tunafish genome, even though
humans are terribly different from squirrels and tunafish. At least,
humans and these other animals seem quite different at first,
(03:18):
but keep in mind that all of them require the
recipes to build eyeballs and spleens and skin and bones
and hearts and so on, so as a result, the
genomes are not so dissimilar. Imagine going to different factories
and examining the pitches and lengths of the screws that
(03:40):
are used. This would tell you very little about the
function of the final product. Say if it's a toaster
versus a blow dryer, both assemble similar elements to achieve
different functions. Now, the fact that we didn't learn what
we thought we might is not a criticism of the
human genome project. It was an enormously important first step.
(04:02):
But what this does tell us is that successive levels
of reduction are typically going to tell us very little
about the questions important to humans. So in the last episode,
we introduced this question of whether we can understand ourselves
by an approach called reductionism. Reductionism is the idea that
(04:26):
we can successively reduce the problems down to their small
scale biological pieces and parts, and eventually come to explain
complex phenomena like thinking and consciousness by understanding the molecules. Now,
there's been a lot of excitement about this possibility for
a long time in neuroscience. For example, in the last episode,
(04:50):
I mentioned Huntington's disease, which is a disorder that's caused
by a mutation in a single gene, and in fact
it was the first gene pulled for a disease, which
seemed like a great success story for reductionism. If you
have this gene, you'll get this disease. But note that
Huntington's is one of the very few examples that can
(05:13):
be dredged up for this sort of one to one mapping.
The reduction of a disease to a single mutation is
extraordinarily rare. Most diseases are polygenetic, meaning that they result
from subtle contributions of tens or hundreds of different genes,
(05:34):
and as science develops better techniques, we're discovering that not
just the coding regions of the genes matter, but also
the areas in between what used to be thought of
as junk DNA. Most diseases seem to result from a
perfect storm of numerous minor changes that combine in dreadfully
(05:57):
complex ways. The challenge to reductionism is far worse than
just a multiple genes problem. The contributions from the genome
can really be understood only in the context of interaction
with the environment. So consider schizophrenia, a disease for which
(06:19):
teams of researchers have been gene hunting for decades. Now
have they found any genes that correlate with the disease?
Sure they have hundreds. In fact, does the possession of
any one of these genes offer much in the way
of prediction about who will develop schizophrenia as a young adult.
(06:39):
Very little. No single gene mutation is as predictive of
schizophrenia as the color of your passport. What does your
passport have to do with schizophrenia? It turns out that
the social stress of being an immigrant to a new
country is one of the critical factors in developing schizophrenia.
(07:02):
In studies across countries, immigrant groups who differ the most
in culture and appearance from the host population carry the
highest risk of schizophrenia. In other words, a lower level
of social acceptance into the majority correlates with a higher
chance of a schizophrenic break in ways not fully understood.
(07:25):
It appears that repeated social rejection perturbs the normal functioning
of the dopamine systems. But even these generalizations don't tell
the whole story, because within a single immigrant group, say
Koreans in America, those who feel worse about their ethnic
differences from the majority are more likely to become psychotic.
(07:49):
Those who are proud and comfortable with their heritage are
mentally safer. Now this news comes as a surprise to many.
Isn't schizophrenia a genetic disorder? The answer is that genetics
play a role. If the genetics make nuts and bolts
that have a slightly altered shape, the whole system may
(08:11):
run in an unusual manner when put in particular environments.
In other environments, the shape of the nuts and bolts
may not matter. When all is said and done, how
a person turns out depends on much more than the
molecular suggestions written down in the DNA. You may remember
(08:32):
that in an earlier episode on neurolaw, I mentioned that
some people have an eight hundred and twenty eight percent
higher chance of committing a violent crime if they carry
a certain set of genes. And those genes you may
remember are summarized as the Y chromosome. If you are
(08:52):
a carrier, we call you a male. Now that correlation
between the Y chromosome and crime is fact, But the
important question to ask is this, why aren't all males criminals?
In fact, there's only one percent of males that get incarcerated.
So what's going on the answer is that knowledge of
(09:12):
the genes alone is not sufficient to tell you much
about behavior. Consider the work of Stephen Swomy. He's a
researcher who raises monkeys in natural environments in Maryland. Now,
in his natural environment setting, he can observe the monkey's
social behavior from their day of birth, and one of
(09:35):
the first things he noticed was that monkeys begin to
express different personalities from a surprisingly early age. He saw
that virtually every social behavior was developed and practiced and
perfected during the course of peer play by four to
six months of age. Now this observation would have been
(09:56):
interesting by itself, but Swomy was able to combine the
behavior observations with regular blood testing of hormones and metabolites,
as well as genetic analysis. What he found were that
five percent of the baby monkeys were overly aggressive. They
showed impulsive and inappropriately belligerent behavior. Those monkeys had low
(10:19):
levels of a blood metabolite related to the neurotransmitter serotonin.
Now here's the key. Swomi and his team found that
there were two different flavors of genes. These are called
alleles that one could possess for a protein that's involved
in transporting serotonin. Let's just call these the short and
(10:39):
the long forms. Now, the monkeys with the short form
showed poor control of violence, while those with the long
form displayed normal behavioral control. But that turned out to
be only part of the story. How a monkey's personality
developed depended on its environment as well. So there were
(11:02):
two ways the monkeys could be reared, either with their mothers,
which was a good environment, or with their peers, which
was called an insecure attachment relationship environment. So the monkeys
with the short form ended up as the aggressive type
when they were raised with their peers, but they did
(11:22):
much better when they were raised with their mothers. For
those with the long form of the gene, the rearing
environment didn't seem to matter much. They were well adjusted
in either case. Now, there are at least two ways
to interpret these results. The first is that the long
allele is a good gene that gives resilience against a
(11:43):
bad childhood environment. The second way you could interpret this
is that you have some monkeys who would have turned
out to be bad seeds, but they were rescued by
good mothering. Now these two interpretations aren't exclusive, and we
don't know which one is exactly correct, but they boiled
down to the same important lesson. A combination of genetics
(12:05):
and environment matters for the final outcome. So, following on
from these monkey studies, people started to study gene environment
interactions in humans. In two thousand and one, a researcher
named av Shalom Caspi and his colleagues set out to
ask whether there are genes for depression. When they went
(12:28):
on the hunt, they found that the answer is sort of.
They learned that there are genes that predispose you, but
whether you actually suffer from depression depends on your life's events.
The researchers discovered this by carefully interviewing dozens of people
to find out what sort of major traumatic events had
(12:50):
transpired in their lives. The loss of a loved one,
a major car accident, and that sort of thing. So
for each participant, they also analyzed the genetics, specifically the
form of a gene involved in regulation of serotonin levels
in the brain. Because people carry two copies of the gene,
one from each parent, there are three possible combinations that
(13:14):
someone might carry, a short short, a short long, or
a long long. The amazing result they found was that
the short short combination predisposed the participants to clinical depression,
but only if they experienced an increasing number of bad
life events. If they were lucky enough to have a
(13:37):
good life, then carrying the short short combination made them
no more likely than anyone else to become clinically depressed.
But if they were unlucky enough to run into serious troubles,
including events that were entirely out of their control, then
they were more than twice as likely to become depressed
as someone with the long long combination. So whether somebody
(14:00):
sense with depression is a matter of their genes and
their life circumstances. Now, Caspy's group then did an entirely
(14:24):
different second study to address a deep societal concern. Do
children who are abused grow up to become child abusers themselves?
Many people believe this statement, but is it really true
and does it matter what kind of genes the child carries.
What caught the attention of the researchers was the fact
(14:47):
that some abused children become violent as adults, but other
abused children do not. When all the obvious factors were
controlled for. The fact stood that childhood abuse by itself
does not predict how an individual would turn out. So
inspired to understand the difference between those who perpetrate the
(15:09):
violence and those who don't, Caspian his colleagues discovered that
a small change in the expression of a particular gene
is what differentiated these two groups. Children with low expression
of the gene were more likely to develop conduct disorders
and become violent criminals as adults, but this bad outcome
(15:31):
was much more likely if the children were abused. If
they harbored the let's call it the bad forms of
the gene, but had been spared childhood abuse, they were
not likely to become abusers. And if they harbored the
good form of the gene, then even a childhood of
severe maltreatment would not necessarily drive them to continue the
(15:54):
cycle of violence. And let me give a third example
of the interaction of gene an environment, and this one
comes from the observation that smoking cannabis marijuana as a
teenager increases the probability of developing psychosis as an adult.
But this connection is true only for some people and
(16:16):
not for others. By this point you can guess the
punch I'm going to say, which is that a genetic
variation underlies one's susceptibility to this. With one combination of alleles,
there's a strong link between cannabis use and adult psychosis.
With a different combination, the link is weak. And here's
(16:37):
another example. The psychologists Angelos Scarpa and Adrian Rain measure
differences in brain function among people diagnosed with antisocial personality disorder,
which is characterized by a total disregard for the feelings
and rights of other people. And antisocial personality disorder, or ASPD,
(16:58):
is highly prevalent among the criminal population. So the researchers
found that ASPD had the highest likelihood of occurring when
brain abnormalities were combined with a history of adverse environmental experiences.
In other words, if you have certain problems with your brain,
but you are raised in a good home, you might
(17:20):
turn out fine. If your brain is fine and your
home is terrible, you might still turn out fine. But
if you have mild brain damage and end up in
a bad home life, you're tossing the dice for a
very unlucky synergy. All these examples demonstrate that it is
neither biology alone nor your environment alone that determines the
(17:44):
final product of a personality. When it comes to the
nature versus nurture question, the answer almost always includes both.
Now importantly, you don't choose your nature and you don't
choose your nurture much less they're entangled interaction. You inherit
a genetic blueprint, and you're born into a world over
(18:07):
which you have no choice throughout your most formative years.
This is the reason people come to the table with
quite different ways of seeing the world, and dissimilar personalities
and varied capacities for decision making. These are not choices.
These are the hand of cards that you're dealt. The
(18:28):
point of episode fifteen about neurolaw was to highlight the
difficulty of assigning culpability under this circumstance of you choosing
neither your genes or your environment. The point of this
episode is to highlight the fact that the machinery that
makes us who we are is not simple, and that
(18:49):
science is not perched on the verge of understanding who
you are and exactly how you came to be that way.
So where we are is this weird place where we
know without a doubt that minds and biology are connected,
but we're not going to have any hope of understanding
(19:09):
that connection with a purely reductionist approach. Reductionism is misleading
for two reasons. First, as we've just seen, the unfathomable
complexity of gene environment interactions puts us a long way
from understanding how any individual person, with her lifetime of
(19:30):
experiences and conversations and abuses and joys and foods she's eaten,
and recreational drugs and prescribed medications and pesticides and educational
experience and so on, we have no idea how she's
going to develop as an individual. It is simply too complex,
and presumably it is going to remain too complex. The
(19:55):
second reason reductionism is misleading is that even while it's
true that we are tied to our molecules and proteins
and neurons, as strokes and hormones and drugs and microorganisms
indisputably tell us, it doesn't logically follow that humans are
best described only as pieces and parts. Like that, the
(20:17):
extreme reductionist idea that we are no more than the
cells of which we are composed is a non starter
for anyone trying to understand human behavior. Just because a
system is made of pieces and parts, and just because
those pieces and parts are critical to the working of
the system, that does not mean that the pieces and
(20:37):
parts are the correct level of description. And I'll give
a few examples of that in a moment. So, given
these shortcomings of reductionism, why did it catch on in
the first place. To understand this, we just need to
look at the historical roots. Over recent centuries, thinking people
watched the growth of deterministic science around them in the
(21:01):
form of the equations of Galileo and Newton and others.
These scientists pulled springs and rolled balls and dropped weights,
and increasingly they were able to predict what the objects
were going to do with simple equations. So by the
nineteenth century, Pierre Simon Laplace had proposed that if one
(21:22):
could know the position of every particle in the universe,
then one could compute forward to know the entire future
and crank the equations the other way to know everything
in the past, this deterministic approach was massively successful. It
predicted the flight of cannon balls and the movement of planets,
and that success was at the heart of biological reductionism.
(21:44):
The idea is that big things can be understood by
discerning smaller and smaller pieces. In this viewpoint, the eras
of understanding all point to the smaller levels humans can
be understood in terms of biology, biology, the language of chemistry, chemistry,
and the equations of atomic physics. In many ways, reductionism
(22:06):
has been the engine of science for the past four
hundred years, and in most fields it has done a
great job. But reductionism isn't the right viewpoint for everything,
and it certainly won't explain the relationship between the brain
and the mind. This is because of a feature known
as emergence. When you put together large numbers of pieces
(22:30):
and parts, the whole can become something greater than the sum.
None of the individual hunks of an airplane have the
property of flight, but when they are attached together in
the right way, the result takes to the air. A
thin metal bar won't do you much good if you're
trying to control a jaguar, but several of them in
(22:54):
parallel standing up have the property of containment. This concept
of emergent properties means that something new can be introduced
that is not inherent in any of the parts. As
another example, imagine that you were an urban highway planner
and you needed to understand your city's traffic flow. You
(23:16):
need to understand where the cars tend to bunch up,
where people speed, where the most dangerous attempts at passing occur.
It won't take you long to realize that an understanding
of these issues will require some model of the psychology
of the drivers. You would lose your job if you
propose to study the length of the screws and the engine,
(23:39):
or the combustion efficiency of the spark plugs. Those are
the wrong levels of description for understanding traffic jams. This
is not to say that the small pieces don't matter.
They do matter. As we saw with brains, adding narcotics,
or changing neurotransmitter levels or mutating genes, this can radically
(23:59):
all alter the essence of a person. And similarly, if
you modify screws and spark plugs, the engines work differently,
and the cars might speed up or slow down, and
other cars might crash. Into them, so the conclusion is clear.
While traffic flow depends on the integrity of the parts,
it is not in any meaningful way equivalent to the parts.
(24:24):
Or think of it this way. If you want to
know why the TV show Seinfeld is funny, you won't
get very far by studying the transistors and capacitors in
the back of your TV. You might be able to
list all the electronic parts in great detail, and you'll
probably learn a thing or two about electricity, but that
won't get you any closer to understanding hilarity. Enjoying Seinfeld
(24:49):
depends entirely on the integrity of the transistors, but the
parts are not themselves funny. And it's exactly the same
with neuros science. While minds depend on the integrity of
the neurons, neurons are not themselves thinking and feeling, and
this forces a reconsideration of how to build a scientific
(25:13):
account of the brain. If we were to work out
a complete physics of neurons and their chemicals, would that
explain the mind? Probably not. The brain presumably does not
break any of the laws of physics, but that doesn't
mean that equations describing biochemical interactions will amount to the
correct level of description, as the complexity theorist Stuart Kaufman
(25:39):
puts it, quote, a couple in love walking along the
banks of the sin are in fact a couple in
love walking along the banks of the sin, not mere
particles in motion unquote. So in the same way, a
meaningful theory of human biology can't be reduced to chemistry
(26:01):
and physics. Instead, it has to be understood in its
own vocabulary of evolution and competition and reward and desire
and reputation and greed and friendship and trust and hunger
and so on, in the same way that traffic flow
is not going to be understood in the vocabulary of
(26:21):
screws and spark plugs, but instead in terms of speed
limits and rush hours and road rage and people wanting
to get home to their families as soon as possible
when their workday is over. And there's another reason why
the neural pieces and parts won't be sufficient for a
full understanding of human experience, and that is your brain
(26:44):
is not the only biological player in the game of
determining who you are. The brain is tied in constant
two way communication with the endocrine and immune systems, which
can be thought of as the greater nervous system. The
greater nervous system is in turn inseparable from the chemical
environments that influence its development, including nutrition and lead paint
(27:08):
and air pollutants and so on and even more. You
are part of a complex social network that changes your
biology with every interaction, and which your actions can change
in return. This makes the borders interesting to contemplate. How
should we define you? Where do you begin and where
do you end? The only solution, I think is to
(27:31):
consider the brain the densest concentration of unice. It's the
peak of the mountain, but it's not the whole mountain.
When we look at behavior and we talk about the
role of the brain, this is actually a shorthand label
that includes contributions from a much broader system, what we
(27:52):
often call a psychobiosocial system. The brain is not so
much the seat of the mind as the hu ubb
of the mind. So let's summarize where we are following
(28:20):
a one way street in the direction of the very
small is the mistake that reductionism can make, and it's
a trap that we want to avoid. Whenever you see
a shorthand statement such as you are your brain which
I say sometimes don't take that to mean that neuroscience
will understand minds only as massive constellations of atoms or
(28:42):
vast jungles of neurons. Instead, the future of understanding the
mind lies in deciphering the patterns of activity that live
on top of the wetwear, and these patterns are directed
both by the internal workings and by interactions from the
surrounding world. So laboratories all over the world are working
(29:04):
to figure out how to understand the relationship between physical
matter and subjective experience, but it's far from a solved
problem now. In the early nineteen fifties, the philosopher Hans
Reichenbach stated that humanity was poised before a complete scientific,
objective account of the world, a scientific philosophy. Now that
(29:28):
was over seventy years ago. Have we arrived, not yet anyway,
and in fact we're a long way off. For some people.
The game is to act as those sciences just on
the brink of figuring everything out. And indeed there's great
pressure on scientists from granting agencies and popular media to
(29:48):
pretend as though the major problems are about to be
solved at any moment. But the truth is that we
face a field of question marks, and this field stretches
to the vanishing point. This suggests an entreaty for openness
while exploring these issues. As one example, the field of
quantum mechanics includes the concept of observation, when an observer
(30:13):
measures the location of a photon that collapses the state
of the particle to a particular position while a moment
ago it was in an infinity of possible states. What
is it about observation? Do human minds interact with the
stuff of the universe? This is a totally unsolved question
in science, and one that may somehow provide a critical
(30:35):
meeting ground between physics and neuroscience. Now, most scientists currently
approach the two fields as separate, and researchers who try
to look more deeply into the connections between them often
end up marginalized. I mentioned in a previous episode that
sometimes scientists will make fun of the pursuit by saying
(30:55):
something like quantum mechanics is mysterious and consciousness is mysterious,
therefore they must be the same thing. Haha. Now that
kind of dismissiveness is actually bad for the field. To
be really clear, I'm not asserting there is a connection
between quantum mechanics and consciousness. I am saying we can't
rule out yet that there is a connection, and that
(31:17):
a premature dismissal is not in the spirit of scientific
inquiry and progress. When people assert that brain function can
be completely explained by classical physics, it's important to recognize
that that is simply an assertion. It's difficult to know
in any age of science what pieces of the puzzle
(31:37):
were missing. As an example, I'll mention what I call
the radio theory of brains, which I mentioned in episode seventeen.
Imagine that you are a primitive tribesman somewhere and that
you stumble upon a transistor radio in the sand. You've
never seen something like this before, so you might pick
it up and you twiddle the knobs, and suddenly, to
(31:59):
your surprise, you hear voices streaming out of this strange
little device. If you are curious and scientifically minded, you
might try to understand what's going on. So you might
pry off the back cover and you discover a little
nest of wires. Now, let's say you begin a careful
scientific study of what causes the voices, and you notice
(32:21):
that each time you pull out the green wire, the
voices stop, and when you put the wire back on
its contact, the voices begin again. The same goes for
the red wire. Yanking out the black wire causes the
voice to get garbled, and removing the yellow wire reduces
the volume to a whisper. So you step carefully through
all the combinations, and you come to a clear conclusion.
(32:44):
The voices depend entirely on the integrity of the circuitry.
Change the circuitry and you damage the voices. So you're
proud of your new discoveries, and you devote your life
to developing a science of the way in which certain
configurations of wires create the existence of magical voices. At
(33:06):
some point, a young person asks you how some simple
patterns of wires can engender conversations and music, and you
admit that you don't exactly know, but you insist that
your science is about to crack that problem at any moment.
But your conclusions are limited by the fact that you
know absolutely nothing about radio waves, and more generally about
(33:31):
electromagnetic radiation, or the fact that there are structures in
distant cities called radio towers, which sends signals by perturbing
invisible waves that travel at the speed of light. It
is so foreign to you that you couldn't even dream
that up. You can't taste radio waves, and you can't
see them, you can't smell them, and you don't yet
(33:53):
have any pressing reason to be creative enough to fantasize
about them. And if you did dream of invisible radio
waves that carry voices, who are you going to convince
of your hypothesis. You have no technology to demonstrate the
existence of the waves, and everybody justifiably points out to
you that the onus is on you to convince them.
(34:16):
So you would become a radio materialist. You would conclude
that somehow the right configuration of wires engenders classical music
and intelligent conversation. You wouldn't realize that you're missing an
enormous piece of the puzzle. Now, to be clear, I
am not asserting that the brain is like a radio,
(34:39):
that we are receptacles picking up signals from elsewhere, and
that our neural circuitry needs to be in place to
do so. But I am noting that things like this
could be true. There's nothing in our current science that
rules this out, and knowing as little as we do
at this point, in history, we have to retain concepts
like this in the large filing cabinet of ideas that
(35:03):
we cannot yet rule in favor of or against. So,
even though very few working scientists will design experiments around
eccentric hypotheses, ideas always need to be proposed and nurtured
as possibilities until evidence weighs in one way or another. Now,
(35:23):
we scientists will often talk about the parsimony of an explanation,
which means is this simplest way to explain something? Can
I come up with an explanation that doesn't add anything
extra that's not needed? And you've probably heard this idea
of Okham's razor, which is simply a statement that the
simplest explanation is probably correct. It's a very useful tool
(35:47):
to keep in mind to make sure that your hypothesis
doesn't have a bunch of extra baggage that's not useful.
But we shouldn't get seduced by the apparent elegance of
argument from parsimony, because that line of reasoning has failed
in the past at least as many times as it succeeded.
For example, it is more parsimonious to assume that the
(36:10):
sun goes around the Earth. It's more parsimonious to suggest
that tiny atoms follow the same rules as objects at
larger scales. It's more parsimonious to suggest that what we
perceive is really what's out there. All of these positions
were long defended by argument from parsimony, and they were
(36:30):
all incorrect. In my view, the argument from parsimony is
really not an argument at all. Is typically used just
to shut down discussion that sometimes shouldn't be shut down.
If history is any guide, it's never a good idea
to assume that a scientific problem is cornered at this
moment in history. I'd say that many or most in
(36:52):
the neuroscience community subscribe to materialism and reductionism. And when
my colleagues and I design experiment and so, we sort
of have to make this assumption. And what it means
is that we should be understandable as a collection of
cells and blood vessels and hormones and proteins and fluids,
all following the basic laws of chemistry and physics as
we currently understand them. Each day, neuroscientists go into laboratory
(37:17):
and work under the assumption that understanding enough of the
pieces and parts will given understanding of the whole. This
break it down to the smallest bits approach is the
same successful method that has been employed in physics and
chemistry and the reverse engineering of electronic devices, But we
(37:37):
don't have any real guarantee that this approach will work
in neuroscience. The brain, with its private, subjective experience, is
unlike any of the problems that we've tackled so far,
and anybody who tells you that we have the problem
cornered with a reductionist approach doesn't actually understand the complexity
(37:59):
of the problem. Keep in mind that every single generation
before us has worked under the assumption that they possessed
all the major tools for understanding the universe, and they
were all wrong without exception. Just imagine trying to construct
a theory about rainbows before the understanding of optics, Or
(38:21):
imagine trying to understand lightning before the knowledge of electricity,
or imagine trying to understand Parkinson's disease before the discovery
of neurotransmitters. Does it seem reasonable that we are the
first ones lucky enough to be born in the perfect generation,
the one in which the assumption of a comprehensive science
(38:42):
is finally true, or does it seem more likely that
in one hundred years from now people will look back
on us and wonder what it was like to be
ignorant of what they now know. Just to be very
clear on this point, I am not claiming that materialism
is incorrect, or even suggesting that I hope it's incorrect.
After all, even a materialist universe would be mind blowingly amazing.
(39:08):
Imagine for a moment that we are nothing but the
product of billions of years of molecules coming together and
ratcheting up through natural selection. That we are composed only
of highways of fluids and chemicals sliding along roadways within
billions of dynamic cells. Imagine that trillions of synaptic conversations
(39:30):
are flashing in parallel, and that this vast fabric of
micron thin circuitry runs algorithms that are totally undreamt of
in modern science, and that these neural programs give rise
to our decision making and loves and desires and fears
and aspirations. To me, that understanding would be a numinous experience,
(39:55):
better than anything ever proposed in anyone's holy text. Whatever
else exists beyond the limits of our current science is
an open question for future generations. But even if strict
materialism turned out to be it, that would be enough.
So to wrap up this week's episode, I'm going to
turn to a famous quip from the great sci fi
(40:17):
writer Arthur C. Clark. He pointed out that any sufficiently
advanced technology is indistinguishable from magic. I don't view the
massive complexity we face in neuroscience as depressing. I view
it as magic. We're already seeing in this podcast series
that everything contained in the biological bags of fluid we
(40:39):
call us is already so far beyond our intuition, beyond
our capacity to think about such vast scales of interaction,
beyond our introspection, that this fairly qualifies is something beyond us.
The complexity of the system that we are is so
vast as to be indistinguishable from Clark's magical technology. As
(41:05):
the saying goes, if our brains were simple enough to
be understood, we wouldn't be smart enough to understand them.
I wrapped my book Incognito years ago by pointing out that,
in this same way that the cosmos is larger than
we ever imagined, we ourselves are something greater than we
had intuited simply by introspection, and we're now getting the
(41:28):
first glimpses of the vastness of this inner space, this internal, hidden,
intimate cosmos. It has its own goals, imperatives, and logic.
It's an organ that feels alien and outlandish to us,
and yet its detailed wiring patterns sculpt the landscape of
(41:52):
our inner lives. What a perplexing masterpiece our brain is,
and how lucky we are to be in a generation
that has the technology and the will to turn our
attention to it. It is the most wondrous thing we
have discovered in the universe, and it is us to
(42:15):
find out more and to share your thoughts. Head over
to Eagleman dot com slash podcasts. Send me an email
at podcasts at eagleman dot com with questions or discussion,
and I'll be making episodes in which I address those
and you can watch full episodes of Inner Cosmos on YouTube.
Subscribe to my channel so that you can follow along
each week for new updates until next time. I'm David Eagleman,
(42:38):
and this is Inner Cosmos.
Host
David Eagleman
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