In the spirit of the Halloween weekend, here is a cool article from Slate on why zombies lumber when they walk. The article is an excerpt from the new book Timothy Verstynen and Bradley Voytek, Do Zombies Dream of Undead Sheep?: A Neuroscientific View of the Zombie Brain (2014). Not only is it a good explainer for zombie walking patterns, but it also introduces some basic neuroscience.

Why Do Zombies Lumber?

Two neuroscientists explain why zombies have so much trouble walking.

By Timothy Verstynen and Bradley Voytek
October 30, 2014 

Drawing by Anne Karetnikov

Excerpted from Do Zombies Dream of Undead Sheep?: A Neuroscientific View of the Zombie Brain by Timothy Verstynen and Bradley Voytek. Out now from Princeton University Press.

In the movie Dawn of the Dead (1978) there is a scene when anarchist outlaws break into the mall that the movie’s heroes had secured and lived in for weeks. This invasion subsequently allows the horde of zombies—which had been aggregating outside—free range of the place. The humans are zipping around playing games while the zombies lumber along slowly and clumsily. The humans easily dispatch the threat of individual zombies because the undead are just too darn slow; there’s no real threat until the humans are outnumbered.

The slow and uncoordinated movements of zombies are perhaps the most identifiable feature of their behavior (next to the whole biting and flesh-eating thing of course). Ask anyone to impersonate a zombie and the first thing she’ll do is hold her arms out, widen her stance, stiffen her legs, and utter a low, guttural moan. That’s because, in the movies, as soon as zombies rise from the dead, they begin walking. Well not walking ... more like lumbering. Each step is slow and arduous. Their stance is wide and stiff. This presents us with a very important clue about what’s happened to their brains.

So what does it take to turn the normally smooth, fast, coordinated movements of a healthy person into the traditional zombie lumber? First, let’s consider the pathways in the brain that give rise to our movements.

While “higher” cognitive functions (aka thinking) tend to get all the glory in neuroscience, before the brain did a lot of deep thinking it did a lot of moving. In fact, some scientists have argued that the entire reason we have a brain is to get us moving around in the environment.

The logic for this argument arises from observations of a little ocean creature called the sea squirt. Seriously, that’s its name. The sea squirt is a small and evolutionarily old animal of the phylum Chordata (when scientists say “evolutionarily old,” we mean that the life form has been in a relatively unchanged state for millions and millions of years). In its young life, the sea squirt is a little larval creature that has a very primitive brain and sensory organs. Its goal during its larval stage of development is to swim around and find a rock to perch on. Once it has found a suitable home, like, say, a nice secure rock with plenty of organic food just flowing by, the sea squirt will attach itself with its head facing out. Then it basically just sits there catching food as it floats by. As it matures into a full-grown adult creature the sea squirt does something quite strange: It digests its own brain.

Yeah, you read that right. Let that sink in. It digests its own brain.

Biologists and neuroscientists have argued that this is evolutionarily advantageous. See, the brain is really expensive, from a metabolic standpoint. Meaning that it takes a lot of energy to keep the brain going, and energy (food) is pretty hard to come by when you’re little more than a stick on a rock with a mouth attached. So when you no longer need a metabolically expensive organ like the brain, it is better to just get rid of it. Thus, no longer needing to navigate around its environment, the sea squirt simply has lost the need for its brain and does away with it. But waste not, want not, in nature. So “doing away with it” means “eating it.” And thus the sea squirt digests its own brain.

Now luckily for us, we humans are more than mouth-sticks attached to rocks. We need to keep moving. We can’t just sit around and digest away our own brain, because food doesn’t just come to us. No, we still have to go out and get our food, even if it is just by driving to the local fast-food chain down the block. This means we get to keep our brains because, for the brain, movement is life.

Unfortunately, the same is true for zombies. Because humans rarely run to zombies, the walking dead have to go to their food source. Which means the zombies also still need their brains. Well, at least part of their brains.

If we presume that the primary function of the brain is to get us moving around in the world, then it’s not surprising that a lot of neural real estate is devoted to the planning and execution of actions. In fact, the computations required to simply move around our environment are distributed across vast swaths of both cortical and subcortical areas. So let’s take a walk through the multitude of brain systems that move us around, shall we?

Most of our voluntary movements start in the neocortex, in two of the four major lobes: the frontal and parietal lobes. Neurons in the parietal lobe that primarily maintain spatial awareness, and those in the frontal lobe that control decision making, are constantly negotiating with one another as to what action we should do next. We might imagine the dialogue going something like this:

• PARIETAL LOBE: “Hey, there’s a tasty piece of broccoli 30 degrees to the left.”
• FRONTAL LOBE: “Broccoli??? No way! I want something more awesome!”
• PARIETAL LOBE: [sigh] “OK, how about that doughnut 10 degrees to the right?”
• FRONTAL LOBE: “Now you’re talking. Hey! Right arm! Attention, right arm! Prepare the triceps, deltoids, and hand muscles for action. We’re going to make a reach.”
• MOTOR CORTEX: “Jawohl, Lord Frontal Cortex!”

In our silly little sketch here, the parietal lobe tells us where to attend to things that are in the environment while the frontal cortex in the front of the head decides what to do. Then the motor areas, in the back part of the frontal cortex, make the movement happen.

Contrary to what you may have heard, there’s not just a single motor cortex. In fact, there are several “motor” areas that are spread out across the frontal lobe and provide the groundwork for planning your movements. You can think of these as the middle management of motor planning. They take the decisions handed down from frontal areas and turn them into plans that the heavy lifters in the arms, legs, and other muscles know what to do with. Which isn’t as easy as it sounds.

Let’s consider the following scenario: You’re a zombie sitting very patiently on the examination table, hand resting on your desiccated, disgusting lap. The nerdy scientists in their awkward lab coats then place a tasty chunk of human flesh right in front of you. What remains of your undead frontal lobes will immediately say “GO GET THAT!” because, hey, free thigh.

Before you can actually grab that tasty piece of meat, however, the motor planning areas in your undead brain, called premotor regions, have to figure out how to get your hand from your lap to the yummy flesh. Now remember, while you can see the tasty morsel, the process of getting your hand off of your lap and to the chunk of meat is pretty complicated. Somehow your brain has to convert a map of the world that’s being projected from the back of your eyeballs to a plan of muscle contractions that uses your bones as levers, much as a puppet master has to coordinate the strings of a marionette doll to make it dance—except here the puppet master is your own brain.

Let’s return our attention to that horde of walking dead outside. While zombie movements are slow, stiff, and uncoordinated, zombies do seem to be able to plan movements in the right direction. That is, when a zombie wants to lunge toward you, it mostly gets the direction right. Once it gets its hands on you, it has no problem grasping and holding on. Therefore it would appear that the cortical motor systems are all intact. So what could be wrong? The only real neural culprits left as plausible candidates for the motor dysfunction seen in zombies are the basal ganglia and the cerebellum.

Given this restriction, let’s consider what happens when the basal ganglia are malfunctioning and compare that with when something goes wrong with the cerebellum. In both cases, people have trouble walking and coordinating their movements, but in dramatically different ways. For example, in Parkinson’s disease, people develop a slouched posture and walk by taking short, shuffling steps. They also have difficulty generating actions without a very obvious goal (they tend to freeze up). In contrast, people with spinocerebellar ataxia develop a stiff, wide-legged stance and take big, lumbering steps. And unlike those afflicted with Parkinson’s disease, these patients have no problem initiating movements.

How can we use this information to diagnose a zombie’s brain? We know that the walking dead are shown in movies as having a stiff, wide-legged stance and a big, lumbering walk. They tend to move slowly (most of the time) and lack smooth, coordinated actions. Yet they don’t seem to have trouble initiating movements. In fact, zombies are almost constantly on the move, they never have problems starting a movement (say reaching for a new victim), and they don’t stall in the middle of movements. They also don’t shuffle or have curvature in their posture.

For these reasons we argue that the cluster of symptoms seen in zombies, the wide stance, lumbering walk, lack of freezing, ease in general planning and execution of actions, reflects a pattern of cerebellar degeneration. That is, cerebellar dysfunction would lead to many of the motor symptoms of the zombie infection. However, cortical motor areas and basal ganglia pathways should be relatively intact.

At about this point, the really astute zombie movie fan will ask, “What about fast zombies?” For those who haven’t seen movies like World War Z, 28 Days Later, or the 2004 remake of Dawn of the Dead, “fast zombies” don’t appear to have any motor dysfunctions. They can move quickly and don’t appear to have any coordination problems. Given the terrifyingly coordinated movements that “fast zombies” exhibit, it is our belief that their cerebellums are likely intact. Any difficulty fast zombies may have moving are likely more to do with the fact that their arms and legs are rotting than any sort of neural damage.

In fact, this difference in presentation may allow us to develop neurological classifications of different subtypes of the disorder that may give important clues to the etiology of the zombie epidemic.

• Subtype I (slow-moving subtype): First observed variant of the disease. 

• Subtype II (fast-moving subtype): Distinguished from Subtype I variant by healthy motor coordination.

Hey folks ... sometimes diseases mutate. Why wouldn’t zombism?

Truth be told, when we had the opportunity to ask George Romero why he made his ghouls walk the way they did in the Living Dead movies, he responded, “They’re supposed to be dead. They’re stiff. That’s how you’d walk if you were dead.” Not quite the answer that appeals to our neuroscience instincts, but a good alternative hypotheses to test in the next zombie apocalypse.
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Excerpted from Do Zombies Dream of Undead Sheep?: A Neuroscientific View of the Zombie Brain by Timothy Verstynen and Bradley Voytek © 2014 by Princeton University Press. Reprinted by permission.

Timothy Verstynen is an assistant professor in the department of psychology and at the Center for the Neural Basis of Cognition at Carnegie Mellon University.

Bradley Voytek is an assistant professor of computational cognitive science and neuroscience at the University of California–San Diego.

Gary Gutting - Can Science Explain Consciousness?

From The Stone, the New York Times regular philosophy column, philosopher Gary Gutting (professor of philosophy at the University of Notre Dame) examines the possibilities for explaining consciousness through science.

He offers two thought experiments here that question the physical basis of consciousness. The least convincing of the two is the classic zombie argument (first proposed by David Chalmers, which offers that there can be a person who has no internal [subjective] experience of the world or itself). My experience and intuition counters that all mammals (a la Damasio) and some birds (crows, ravens, parrots) have subjectivity.

Still, it's nice to see discussions like this occurring in newspapers and not only in remote academic spaces.

Mary and the Zombies: Can Science Explain Consciousness?

By GARY GUTTING

THE STONE 

March 12, 2013


The Stone is a forum for contemporary philosophers on issues both timely and timeless.

We trust science because its claims are based on experience. But experience itself is a subjective reality that seems to elude the objectivity of scientific understanding. We know that our experiences—of seeing red, feeling pain, falling in love and so forth—depend on physical systems like the brain that science can, in principle, exhaustively explain. But it’s hard to make sense of the idea that experiences themselves could be physical. No doubt experiences correlate with objective physical facts, but, as subjective phenomena, how could they be such facts? When I feel intense pain, scientists may be able to observe brain-events that cause my pain, but they cannot observe the very pain that I feel. What science can observe is public and objective; what I feel is private and subjective.

Perhaps, though, it’s hard to understand how experiences could be physical only because we lack the relevant concepts. After all, before scientists developed the concepts of biochemistry, many found it impossible to imagine how organisms could be entirely physical. Now the idea is far more plausible. What’s to say that future scientific developments won’t allow us to understand how experiences can be entirely physical?

Nevertheless, some of the most interesting recent philosophical discussions have centered around two thought experiments suggesting that experiences cannot be physical. These thought-experiments have by no means settled the issue, but they have convinced quite a few philosophers and have posed a serious challenge to the claim that experience is entirely physical.

First, consider Mary, a leading neuroscientist who specializes in color perception. Mary lives at a time in the future when the neuroscience of color is essentially complete, and so she knows all the physical facts about colors and their perception. Mary, however, has been totally color-blind from birth. (Here I deviate from the story’s standard form, in which—for obscure reasons—she’s been living in an entirely black-and-white environment.)

Fortunately, due to research Mary herself has done, there is an operation that gives her normal vision. When the bandages are removed, Mary looks around the room and sees a bouquet of red roses sent by her husband. At that moment, Mary for the first time experiences the color red and now knows what red looks like. Her experience, it seems clear, has taught her a fact about color that she did not know before. But before this she knew all the physical facts about color. Therefore, there is a fact about color that is not physical. Physical science cannot express all the facts about color.

Second, consider a zombie. Not the brain-eating undead of movies, but a philosophical zombie, defined as physically identical to you or me but utterly lacking in internal subjective experience. Imagine, for example, that in some alternative universe you have a twin, not just genetically identical but identical in every physical detail—made of all the same sorts of elementary particles arranged in exactly the same way. Isn’t it logically possible that this twin has no experiences?

It may, of course, be true that, in our world, the laws of nature require that certain objective physical structures be correlated with corresponding subjective experiences. But laws of nature are not logically necessary (if they were, we could discover them as we do laws of logic or mathematics, by pure thought, independent of empirical facts). So in an alternative universe, there could (logically) be a being physically identical to me but with no experiences: my zombie-twin.

But if a zombie-twin is logically possible, it follows that my experiences involve something beyond my physical makeup. For my zombie-twin shares my entire physical makeup, but does not share my experiences. This, however, means that physical science cannot express all the facts about my experiences.

It’s worth noting that that philosophers who find these thought-experiments convincing do not conclude that there is no sense in which an experience is physical. Seeing red, for example, involves photons striking the retina, followed by a whole string of physical events that process the retinal information before we actually have a subjective sense of color. There’s a purely physical sense in which this is “seeing.” This is why we can say that a surveillance camera “sees” someone entering a room. But the “seeing” camera has no subjective experience; it has no phenomenal awareness of what it’s like to see something. That happens only when we look at what the camera recorded. The claim that experience is not physical applies only to this sense of experience. But, of course, it is experience in this sense that makes up the rich inner experience that matters so much to us.

Also, few philosophers think these thought-experiments show that there are souls or some other sort of supernatural entities. Frank Jackson, who first proposed the Mary scenario, and David Chalmers, who gave the most influential formulation of the zombie example, remain philosophical naturalists. They maintain that there is no world beyond the natural one in which we live. Their claim is rather that this world contains a natural reality (consciousness) that escapes the scope of physical explanation. Chalmers, in particular, supports a “naturalistic dualism” that proposes to supplement physical science by postulating entities with irreducibly subjective (phenomenal) properties that would allow us to give a natural explanation of consciousness. Not surprisingly, however, some philosophers have seen Jackson’s and Chalmers’s arguments as supporting a traditional dualism of a natural body and a supernatural soul.

I myself have come to no firm conclusions about the questions raised by these thought experiments, and I would be very interested in the ideas and arguments of Stone readers. We previously had what I found to be a very fruitful discussion of disagreement among epistemic peers, which convinced me that there could be value in “crowd-sourcing” current philosophical topics. Of course, professional philosophers have technical resources that non-philosophers lack. But a profession brings with it regulating assumptions that themselves should be open to philosophical questioning, and intelligent people outside the profession can be a source of fruitful new ideas. So I encourage readers to share their thoughts on the question: do these thought experiments show that there are facts about consciousness that go beyond what physical science can know—that there is a non-physical aspect to consciousness? I’ll discuss the responses in a follow-up column next week.

Gary Gutting is a professor of philosophy at the University of Notre Dame, and an editor of Notre Dame Philosophical Reviews. He is the author of, most recently, “Thinking the Impossible: French Philosophy since 1960,” and writes regularly for The Stone.

Alva Noë - The Zombie Within

Philosopher Alva Noë wrote an interesting article last week for NPR's 13.7 Cosmos and Culture blog on the zombie within, a metaphor for all of the "can't-help-yourself" books that have come out in the last year, many of which I have noted here many times (Daniel Kahneman's Thinking: Fast and Slow, David Eagleman's Incognito: The Secret Lives of the Brain, Michael Gazzaniga's Who's in Charge?: Free Will and the Science of the Brain, Leonard Mlodinow's Subliminal: How Your Unconscious Mind Rules Your Behavior, and Jonathan Haidt's The Righteous Mind: Why Good People Are Divided by Politics and Religion, among others) - and it was inspired by James Atlas's recent New York Times article, The Amygdala Made Me Do It.

Noë has generally been a supporter of agency and free will, and he remains so here:

Skillful, fluent action is not slavery to the neural zombie within; it is liberation from the rote and the regulated. It is flexible attunement to where we find ourselves.

I would like to read another 50 pages or so on this topic, by him.

The Zombie Within

May 20, 2012

by Alva Noë 

Francois Guillot/AFP/Getty Images
The inner, neural zombie exposed?

The zombie within: the idea that we don't know what we are doing, or where we are going, when we think we best know, is an old one. (The words I've just paraphrased are Emerson's.)

James Atlas, in a recent New York Times article, is probably on to something when he notices that there has been an explosion recently of what he wittily calls Can't-Help-Yourself Books. These are books that take as their starting point something like the idea that science now teaches us the "choices we make in day-to-day life are prompted by impulses lodged deep within the nervous system" and that, therefore, in some sense, we are not really the authors of our own actions, responses, choices.

Today I want to come at the question of whether we are really controlled by a neural zombie deep within by considering one route that might lead to that conclusion. This has to do with how we think about thinking, action and the intellect.

Consider that a novice basketball player needs to think about the mechanics of how to dribble; doing so — concentrating, paying attention to hand, wrist, ball, etc. — improves performance. But not so for the experienced player. It isn't just that that he or she doesn't need to pay attention to ball handling to play well; it's that fluent and skillful performance will be disrupted if she does. This is a general fact about expertise. Pick your favorite example. A chess beginner needs to think about the rules governing how the pieces move in order to play. That layer of thinking recedes into the background for the advanced player, freeing him up to pay attention to the things that matter for winning, such as tactics and strategy.

It's tempting to say that the contrast here is between thinking and not thinking, or being conscious and being a zombie. The expert leaves the plodding, deliberative mind behind and enters "the zone," captures "the flow," lets the zombie within guide the fingers as they race over the neck of guitar, or the hands and feet as they (not "you"!) work the pedals and gear shift as you accelerate to overtake on the high way.

But this gets what interests us wrong.

Yes, athletes, musicians, drivers and chess players, when they are in the flow, can act fast without needing to make decisions about what to do. But this is not because they aren't thinking. Nor is it because they are thinking really fast. It's because they are thinking about what matters, such as the musical ideas or the traffic or the potential vulnerability of the King to attack. Mastery consists precisely in shifting attention from the mechanics of a task to, if you like, the task's point.

Nothing illustrates this better than the case of language itself. We learn to decline and conjugate so that we can talk. The learner of a second language needs to give painstaking attention to grammatical choices and rules. But conversation — thoughtful participation in the parry and thrust, the give and take — requires that we stop focusing on the grammar and start focusing on what we are doing. What is required is not that we become automata, or forget the grammar; what is required is that we become masters of it.

Historically, we have tended to think of "intelligence" as a matter of deliberate judgment; we celebrate rationality. Agency consists of doing things for reasons: see, think, decide, plan, execute. This is the structure of human agency. If it should turn out to be the case that much of our action passes over the thinking/deciding/planing stage, then it would seem to follow that, at least much of the time, we are not the agents we think we are. If it should turn out that we act without deliberating, then, it would seem, we're a lot less smart and in control than we think we are.

But this conclusion isn't mandatory. We can and should reject the conception of intelligence and agency it presupposes. An expert is not simply someone who has learned to do what the beginner does but fast. The expert has an entirely different relation to the task. The expert's intelligence and thoughtfulness shines not despite the lack of deliberation, but thanks to the freedom not needing to deliberate affords.

Sometimes not deliberating is the mark of our intellectual fitness, as when I answer your question without needing to ponder your grammar or my own.

When it comes to the activities of daily life — talking, thinking, shopping, driving, reading, looking, learning — we are all experts.

It is expertise that lets us get out of our heads, to the things that matter. Skillful, fluent action is not slavery to the neural zombie within; it is liberation from the rote and the regulated. It is flexible attunement to where we find ourselves. (Echoes of Emerson again.) It is intelligent life.

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