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Edge 307—December 4, 2009
[7,150 words]





THE YEAR’S BEST BOOKS

"brilliant ... captivating ... overwhelming"

Books to read (and give) now
SEED PICKS DECEMBER 1, 2009

This Will Change Everything: Ideas That Will Shape the Future
Edited by John Brockman (Harper Perennial)

The latest prophetic collection from John Brockman of Edge.org invites scores of the world’s most brilliant thinkers, including Richard Dawkins, Lisa Randall, and Brian Eno, to predict what game-changing events will occur in their lifetimes. Their speculations run the existential gamut, as some predict deliberate nuclear disaster or accidental climatic apocalypse and others foresee eternal life, unlimited prosperity, and boundless happiness. Between such extremes of heaven and hell lie more ambiguous visions: An end to forgetting, the creation of intelligent machines, and cosmetic brain surgery, to name a few. Pouring over these pages is like attending a dinner party where every guest is brilliant and captivating and only wants to speak with you—overwhelming, but an experience to savor.


The parasite my lab is beginning to focus on is one in the world of mammals, where parasites are changing mammalian behavior. It's got to do with this parasite, this protozoan called Toxoplasma. If you're ever pregnant, if you're ever around anyone who's pregnant, you know you immediately get skittish about cat feces, cat bedding, cat everything, because it could carry Toxo. And you do not want to get Toxoplasma into a fetal nervous system. It's a disaster.

TOXO
A Conversation with Robert Sapolsky


[24:27 minutes]

ROBERT SAPOLSKY is a professor of biological sciences at Stanford University and of neurology at Stanford's School of Medicine. His books include A Primate's Memoir, and Zebras Don't Get Ulcers: A Guide to Stress, Stress-Related Diseases and Coping.

Robert Sapolsky's Edge Bio Page

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TOXO

[ROBERT SAPOLSKY:] In the endless sort of struggle that neurobiologists have — in terms of free will, determinism — my feeling has always been that there's not a whole lot of free will out there, and if there is, it's in the least interesting places and getting more sparse all the time. But there's a whole new realm of neuroscience which I've been thinking about, which I'm starting to do research on, that throws in another element of things going on below the surface affecting our behavior. And it's got to do with this utterly bizarre world of parasites manipulating our behavior. It turns out that this is not all that surprising. There are all sorts of parasites out there that get into some organism, and what they need to do is parasitize the organism and increase the likelihood that they, the parasite, will be fruitful and multiply, and in some cases they can manipulate the behavior of the host.

Some of these are pretty astounding. There's this barnacle that rides on the back of some crab and is able to inject estrogenic hormones into the crab if the crab is male, and at that point, the male's behavior becomes feminized. The male crab digs a hole in the sand for his eggs, except he has no eggs, but the barnacle sure does, and has just gotten this guy to build a nest for him. There are other ones where wasps parasitize caterpillars and get them to defend the wasp's nests for them. These are extraordinary examples.

The parasite my lab is beginning to focus on is one in the world of mammals, where parasites are changing mammalian behavior. It's got to do with this parasite, this protozoan called Toxoplasma. If you're ever pregnant, if you're ever around anyone who's pregnant, you know you immediately get skittish about cat feces, cat bedding, cat everything, because it could carry Toxo. And you do not want to get Toxoplasma into a fetal nervous system. It's a disaster.

The normal life cycle for Toxo is one of these amazing bits of natural history. Toxo can only reproduce sexually in the gut of a cat. It comes out in the cat feces, feces get eaten by rodents. And Toxo's evolutionary challenge at that point is to figure out how to get rodents inside cats' stomachs. Now it could have done this in really unsubtle ways, such as cripple the rodent or some such thing. Toxo instead has developed this amazing capacity to alter innate behavior in rodents.

If you take a lab rat who is 5,000 generations into being a lab rat, since the ancestor actually ran around in the real world, and you put some cat urine in one corner of their cage, they're going to move to the other side. Completely innate, hard-wired reaction to the smell of cats, the cat pheromones. But take a Toxo-infected rodent, and they're no longer afraid of the smell of cats. In fact they become attracted to it. The most damn amazing thing you can ever see, Toxo knows how to make cat urine smell attractive to rats. And rats go and check it out and that rat is now much more likely to wind up in the cat's stomach. Toxo's circle of life completed.

This was reported by a group in the UK about half a dozen years ago. Not a whole lot was known about what Toxo was doing in the brain, so ever since, part of my lab has been trying to figure out the neurobiological aspects. The first thing is that it's for real. The rodents, rats, mice, really do become attracted to cat urine when they've been infected with Toxo. And you might say, okay, well, this is a rodent doing just all sorts of screwy stuff because it's got this parasite turning its brain into Swiss cheese or something. It's just non-specific behavioral chaos. But no, these are incredibly normal animals. Their olfaction is normal, their social behavior is normal, their learning and memory is normal. All of that. It's not just a generically screwy animal.

You say, okay well, it's not that, but Toxo seems to know how to destroy fear and anxiety circuits. But it's not that, either. Because these are rats who are still innately afraid of bright lights. They're nocturnal animals. They're afraid of big, open spaces. You can condition them to be afraid of novel things. The system works perfectly well there. Somehow Toxo can laser out this one fear pathway, this aversion to predator odors.

We started looking at this. The first thing we did was introduce Toxo into a rat and it took about six weeks for it to migrate from its gut up into its nervous system. And at that point, we looked to see, where has it gone in the brain? It formed cysts, sort of latent, encapsulated cysts, and it wound up all over the brain. That was deeply disappointing.

But then we looked at how much winds up in different areas in the brain, and it turned out Toxo preferentially knows how to home in on the part of the brain that is all about fear and anxiety, a brain region called the amygdala. The amygdala is where you do your fear conditioning; the amygdala is what's hyperactive in people with post-traumatic stress disorder; the amygdala is all about pathways of predator aversion, and Toxo knows how to get in there.

Next, we then saw that Toxo would take the dendrites, the branch and cables that neurons have to connect to each other, and shriveled them up in the amygdala. It was disconnecting circuits. You wind up with fewer cells there. This is a parasite that is unwiring this stuff in the critical part of the brain for fear and anxiety. That's really interesting. That doesn't tell us a thing about why only its predator aversion has been knocked outwhereas fear of bright lights, et cetera, is still in there. It knows how to find that particular circuitry.

So what's going on from there? What's it doing? Because it's not just destroying this fear aversive response, it's creating something new. It's creating an attraction to the cat urine. And here is where this gets utterly bizarre. You look at circuitry in the brain, and there's a reasonably well-characterized circuit that activates neurons which become metabolically active circuits where they're talking to each other, a reasonably well-understood process that's involved in predator aversion. It involves neurons in the amygdala, the hypothalamus, and some other brain regions getting excited. This is a very well characterized circuit.

Meanwhile, there is a well-characterized circuit that has to do with sexual attraction. And as it happens, part of this circuit courses through the amygdala, which is pretty interesting in and of itself, and then goes to different areas of the brain than the fear pathways.

When you look at normal rats, and expose them to cat urine, cat pheromones, exactly as you would expect, they have a stress response: their stress hormone levels go up, and they activate this classical fear circuitry in the brain. Now you take Toxo-infected rats, right around the time when they start liking the smell of cat urine, you expose them to cat pheromones, and you don't see the stress hormone release. What you see is that the fear circuit doesn't activate normally, and instead the sexual arousal activates some. In other words, Toxo knows how to hijack the sexual reward pathway. And you get males infected with Toxo and expose them to a lot of the cat pheromones, and their testes get bigger. Somehow, this damn parasite knows how to make cat urine smell sexually arousing to rodents, and they go and check it out. Totally amazing.

So on a certain level, that explains everything. Ah ha! It takes over sexual arousal circuitry. This is utterly bizarre. At this point, we don't know what the basis is of the attraction in the females. It's something we're working on.

Some extremely nice work has been done by a group at Leeds in the UK, who are looking at the Toxo genome, and we're picking up on this collaboratively. Okay, Toxo, it's a protozoan parasite. Toxo and mammals had a common ancestor, and the last they did was God knows, billions of years ago. And you look in the Toxo genome, and it's got two versions of the gene called tyrosine hydroxylase. And if you were a neuro-chemistry type, you would be leaping up in shock and excitement at this point.

Tyrosine hydroxylase is the critical enzyme for making dopamine: the neurotransmitter in the brain that's all about reward and anticipation of reward. Cocaine works on the dopamine system, all sorts of other euphoriants do. Dopamine is about pleasure, attraction and anticipation. And the Toxo genome has the mammalian gene for making the stuff. It's got a little tail on the gene that targets, specifies, that when this is turned into the actual enzyme, it gets secreted out of the Toxo and into neurons. This parasite doesn't need to learn how to make neurons act as if they are pleasurably anticipatory; it takes over the brain chemistry of it all on its own.

Again that issue of specificity comes up. Look at closely related parasites to Toxo: do they have this gene? Absolutely not. Now look at the Toxo genome and look at genes related to other brain messengers. Serotonin, acetylcholine, norepinephrine, and so on, and you go through every single gene you can think of. Zero. Toxo doesn't have them, Toxo's got this one gene which allows it to just plug into the whole world of mammalian reward systems. And at this point, that's what we know. It is utterly cool.

Of course, at this point, you say well, what about other species? What does Toxo do to humans? And there's some interesting stuff there that's reminiscent of what's going on in rodents. Clinical dogma is you first get a Toxo infection. If you're pregnant, it gets into the fetal nervous system, a huge disaster. Otherwise, if you get a Toxo infection, it has phases of inflammation, but eventually it goes into this latent asymptomatic stage, which is when these cysts form in the brain. Which is, in a rat, when it stops being anything boring like asymptomatic, and when the behavior starts occurring. Interestingly, that's when the parasite starts making this tyrosine hydroxylase.

So what about humans? A small literature is coming out now reporting neuropsychological testing on men who are Toxo-infected, showing that they get a little bit impulsive. Women less so, and this may have some parallels perhaps with this whole testosterone aspect of the story that we're seeing. And then the truly astonishing thing: two different groups independently have reported that people who are Toxo-infected have three to four times the likelihood of being killed in car accidents involving reckless speeding.

In other words, you take a Toxo-infected rat and it does some dumb-ass thing that it should be innately skittish about, like going right up to cat smells. Maybe you take a Toxo-infected human and they start having a proclivity towards doing dumb-ass things that we should be innately averse to, like having your body hurdle through space at high G-forces. Maybe this is the same neurobiology. This is not to say that Toxo has evolved the need to get humans into cat stomachs. It's just sheer convergence. It's the same nuts and bolts neurobiology in us and in a rodent, and does the same thing.

On a certain level, this is a protozoan parasite that knows more about the neurobiology of anxiety and fear than 25,000 neuroscientists standing on each other's shoulders, and this is not a rare pattern. Look at the rabies virus; rabies knows more about aggression than we neuroscientists do. It knows how to make you rabid. It knows how to make you want to bite someone, and that saliva of yours contains rabies virus particles, passed on to another person.

The Toxo story is, for me, completely new terrain — totally cool, interesting stuff, just in terms of this individual problem. And maybe it's got something to do with treatments for phobias down the line or whatever it is to make it seem like anything more than just the coolest gee whiz thing possible. But no doubt it's also a tip of the iceberg of God knows what other parasitic stuff is going on out there. Even in the larger sense, God knows what other unseen realms of biology make our behavior far less autonomous than lots of folks would like to think.

With regard to parasite infections like Toxo in humans, there is a big prevalence in certain parts of the world. There's a higher prevalence in the tropics, where typically more than 50 percent of people are infected. Lower rates in more temperate zones for reasons that I do not understand and do not choose to speculate on. France has really high rates of Toxo infection. In much of the developing world, it's bare feet, absorbing it through soil, where cats may have been. It's food that may not have been washed sufficiently and absorption through hands. It's the usual story that people in the developing world are more subject to all sorts of infectious stuff.

A few years ago, I sat down with a couple of the Toxo docs over in our hospital who do the Toxo testing in the Ob/Gyn clinics. And they hadn't heard about this behavioral story, and I'm going on about how cool and unexpected it is. And suddenly, one of them jumps up, flooded with 40-year-old memories, and says, "I just remembered back when I was a resident, I was doing a surgical transplant rotation. And there was an older surgeon, who said, if you ever get organs from a motorcycle accident death, check the organs for Toxo. I don't know why, but you find a lot of Toxo." And you could see this guy was having a rush of nostalgic memories from back when he was 25 and all because he was being told this weird factoid ... ooh, people who die in motorcycle accidents seem to have high rates of Toxo. Utterly bizarre.

What is the bottom line on this? Well, it depends; if you want to overcome some of your inhibitions, Toxo might be a very good thing to have in your system. Not surprisingly, ever since we started studying Toxo in my lab, every lab meeting we sit around speculating about which people in the lab are Toxo-infected, and that might have something to do with one's level of recklessness. Who knows? It's very interesting stuff, though.

You want to know something utterly terrifying? Here's something terrifying and not surprising. Folks who know about Toxo and its affect on behavior are in the U.S. military. They're interested in Toxo. They're officially intrigued. And I would think they would be intrigued, studying a parasite that makes mammals perhaps do things that everything in their fiber normally tells them not to because it's dangerous and ridiculous and stupid and don't do it. But suddenly with this parasite on board, the mammal is a little bit more likely you go and do it. Who knows? But they are aware of Toxo.

There are two groups that collaborate in Toxo research. One is Joanne Webster, who was at Oxford at the time that she first saw this behavioral phenomenon. And I believe she's now at University College London. And the other is Glenn McConkey at University of Leeds. And they're on this. She's more of a behaviorist, he's more of an enzyme biochemist guy. We're doing the neurobiology end of it. We're all talking lots. (I'm not quite sure what the previous paragraph adds, so I'd be happy to see it cut, if you're looking to save some space).

There's a long-standing literature that absolutely shows there's a statistical link between Toxo infection and schizophrenia. It's not a big link, but it's solidly there. Schizophrenics have higher than expected rates of having been infected with Toxo, and not particularly the case for other related parasites. Links between schizophrenia and mothers who had house cats during pregnancy. There's a whole literature on that. So where does this fit in?

Two really interesting things. Back to dopamine and the tyrosine hydroxylase gene that Toxo somehow ripped off from mammals, which allows it to make more dopamine. Dopamine levels are too high in schizophrenia. That's the leading suggestion of what schizophrenia is about neurochemically. You take Toxo-infected rodents and their brains have elevated levels of dopamine. Final deal is, and this came from Webster's group, you take a rat who's been Toxo-infected and is now at the state where it would find cat urine to be attractive, and you give it drugs that block dopamine receptors, the drugs that are used to treat schizophrenics, and it stops being attracted to the cat urine. There is some schizophrenia connection here with this.

Any time Toxo's picked up in the media, and this schizophrenia angle is brought in, the irresistible angle is the generic crazy cat lady, you know, living in the apartment with 43 cats and their detritus. And that's an irresistible one in terms of Toxo psychiatric status: cats. But God knows what stuff is lurking there.


Where I intend to be divisive is with respect to the argument that religion, and moral education more generally, represent the only — or perhaps even the ultimate — source of moral reasoning. If anything, moral education is often motivated by self-interest, to do what's best for those within a moral community, preaching singularity, not plurality. Blame nurture, not nature, for our moral atrocities against humanity. And blame educated partiality more generally, as this allows us to lump into one category all those who fail to acknowledge our shared humanity and fail to use secular reasoning to practise compassion.

IT SEEMS BIOLOGY (NOT RELIGION) EQUALS MORALITY
by Marc D. Hauser

MARC D. HAUSER an evolutionary psychologist and biologist, is Harvard College Professor, Professor of Psychology and Program in Neurosciences, and Director of Primate Cognitive Neuroscience Laboratory. He is the author of The Evolution of Communication, Wild Minds: What Animals Think, and Moral Minds: How Nature Designed Our Universal Sense of Right and Wrong.

Marc Hauser's Edge Bio Page

PERMALINK


IT SEEMS BIOLOGY (NOT RELIGION) EQUALS MORALITY

For many, living a moral life is synonymous with living a religious life. Just as educated students of mathematics, chemistry and politics know that 1=1, water=H2O, and Barack Obama=US president, so, too, do religiously educated people know that religion=morality.

As simple and pleasing as this relationship may seem, it has at least three possible interpretations.

First, if religion represents the source of moral understanding, then those lacking a religious education are morally lost, adrift in a sea of sinful temptation. Those with a religious education not only chart a steady course, guided by the cliched moral compass but they know why some actions are morally virtuous and others are morally abhorrent.

Second, perhaps everyone has a standard engine for working out what is morally right or wrong but those with a religious background have extra accessories that refine our actions, fuelling altruism and fending off harms to others.

Third, while religion certainly does provide moral inspiration, not all of its recommendations are morally laudatory. Though we can all applaud those religions that teach compassion, forgiveness and genuine altruism, we can also express disgust and moral outrage at those religions that promote ethnic cleansing, often by praising those willing to commit suicide for the good of the religious "team".

None of my comments so far are meant to be divisive with respect to the meaning and sense of community that many derive from religion. Where I intend to be divisive is with respect to the argument that religion, and moral education more generally, represent the only — or perhaps even the ultimate — source of moral reasoning. If anything, moral education is often motivated by self-interest, to do what's best for those within a moral community, preaching singularity, not plurality. Blame nurture, not nature, for our moral atrocities against humanity. And blame educated partiality more generally, as this allows us to lump into one category all those who fail to acknowledge our shared humanity and fail to use secular reasoning to practise compassion.

If religion is not the source of our moral insights — and moral education has the demonstrated potential to teach partiality and, therefore, morally destructive behaviour — then what other sources of inspiration are on offer?

One answer to this question is emerging from an unsuspected corner of academia: the mind sciences. Recent discoveries suggest that all humans, young and old, male and female, conservative and liberal, living in Sydney, San Francisco and Seoul, growing up as atheists, Buddhists, Catholics and Jews, with high school, university or professional degrees, are endowed with a gift from nature, a biological code for living a moral life.

This code, a universal moral grammar, provides us with an unconscious suite of principles for judging what is morally right and wrong. It is an impartial, rational and unemotional capacity. It doesn't dictate who we should help or who we are licensed to harm. Rather, it provides an abstract set of rules for how to intuitively understand when helping another is obligatory and when harming another is forbidden. And it does so dispassionately and impartially. What's the evidence?

To experience what subjects in some of our studies experience, see the moral sense test . It asks for information about gender, age, nationality, education, politics and religion. Once logged in, there is a series of scenarios asking participants to judge whether a particular action is morally forbidden, permissible or obligatory.

Most of the scenarios involve genuine moral dilemmas. All are unfamiliar, for a reason. Unfamiliar and artificial cases have an advantage over familiar scenarios, such as abortion, euthanasia and charitable donations: no one has a well-rehearsed and explicit moral argument for such cases, and for all the cases we create, neither the law nor religious scripture provides any guidance.

For example, if five people in a hospital each require an organ to survive, is it permissible for a doctor to take the organs of a healthy person who happens to walk by the hospital? Or if a lethal gas has leaked into the vent of a factory and is headed towards a room with seven people, is it permissible to push someone into the vent, preventing the gas from reaching the seven but killing the one? These are true moral dilemmas — challenging problems that push on our intuitions as lay jurists, forcing us to wrestle with the opposing forces of consequences (saving the lives of many) and rules (killing is wrong).

Based on the responses of thousands of participants to more than 100 dilemmas, we find no difference between men and women, young and old, theistic believers and non-believers, liberals and conservatives. When it comes to judging unfamiliar moral scenarios, your cultural background is virtually irrelevant.

What guides your judgments is the universal and unconscious voice of our species, a biological code, a universal moral grammar. We tend to see actions as worse than omissions of actions: pushing a person into the factory vent is worse than allowing the person to fall in. Using someone as a means to some greater good is worse if you make this one person worse off than if you don't. This is the difference between an evitable and inevitable harm. If the person in the hospital or in the factory is perfectly healthy, taking his life to save the lives of many is worse than if he is dying and there is no cure. Distinctions such as these are abstract, impartial and emotionally cold. They are like recognising the identity relationship of 1=1, a rule that is abstract and content-free.

If this code is universal and impartial, then why are there are so many moral atrocities in the world? The answer comes from thinking about our emotions, the feelings we recruit to fuel in-group favouritism, out-group hatred and, ultimately, dehumanisation.

Consider the psychopath, Hollywood's favourite moral monster. Clinical studies reveal that they feel no remorse, shame, guilt or empathy, and lack the tools for self-control. Because they lacked these capacities, several experts have argued that they lack the wherewithal to understand what is right or wrong and, consequently, to do the wrong thing. New studies show, however, that this conclusion is at least partially wrong. Psychopaths know full well what is right and wrong but don't care. Their moral knowledge is intact but their moral emotions are damaged. They are perfectly normal jurists but perfectly abnormal moral actors. For the psychopath, other humans are no different from rocks or artefacts. They are disposable.

Here lies the answer to understanding the dangers of nurture, of education and partiality. When we fuel in-group biases by elevating and praising members of the group, we often unconsciously, and sometimes consciously, denigrate the "other" by feeding the most nefarious of all emotions, the dragon of disgust.

We label the other (the members of the out-group) with a description that makes them sub-human or even inanimate, often parasitic and vile, and thus disgusting. When disgust is recruited, those in the in-group have only one way out: purge the other.

When the Dalai Lama stated that the Chinese were attempting "cultural genocide" against the Tibetans by attempting to stop protests, he was not only making a statement about the Chinese per se but about a particular form of moral education, one that fails to acknowledge autonomy, preaches partiality and feeds disgust and dehumanisation. The Chinese must stop their attempt to purge the Tibetans of their cultural heritage and right of cultural expression. And the nations of the world, and their diverse peoples, must remain vigilant against any attempts at cultural decimation.

The good news about the psychology of prejudice, of creating distinctive classes of individuals who are in the tribe and outside of it, is that it is flexible, capable of change and — viewed from an evolutionary perspective — as abstract and content-free as the rules that enter into our moral grammar.

All animals, humans included, have evolved the capacity to create a distinction between members of the in-group and those in the out-group. But the features that are selected are not set in the genome. Rather, it is open to experience.

For example, we know from studies of child development that within the first year of life, babies prefer to look at faces from their own race to faces of a different race, prefer to listen to speakers of their native language over foreigners, and even within their native language prefer to listen to their own dialect. But if babies watch someone of another race speaking their native language, they are much more willing to engage with this person than someone of the same race speaking a different language.

These social categories are created by experience, and some features are more important than others because they are harder to fake and more indicative of a shared cultural background. But, importantly, they are plastic. Racial discrimination is greatly reduced among children of mixed-racial parents. And adults who have dated individuals of another race are also much less prejudiced. On this note, moral education can play a more nurturing role by introducing all children, early in life, to the varieties of religions, political systems, languages, social organisations and races. Exposure to diversity is perhaps our best option for reducing, if not eradicating, strong out-group biases.

Lest there be any confusion about the claims I am making, I am not saying that our evolved capacity to intuitively judge what is right or wrong is sufficient to live a moral life. It is most definitely not and for two good reasons.

For one, some of our moral instincts evolved during a period of human history that looked nothing like the situation today. In our distant past, we lived in small groups consisting of highly familiar and often familial individuals, with no formal laws. Today we live in a large and diffuse society, where our decisions have little-to-no impact on most people in our community but with laws to enforce those who deviate from expected norms. Further, we are confronted with moral decisions that are unfamiliar, including stem cells, abortion, organ transplants and life support. When we confront these novel situations, our evolved system is ill-equipped.

The second reason is that living a moral life requires us to be restless with our present moral norms, always challenging us to discover what might and ought to be. And here is where nurture can re-enter the conversation. We need education because we need a world in which people listen to the universal voice of their species, while stopping to wonder whether there are alternatives. And if there are alternatives, we need rational and reasonable people who will be vigilant of partiality and champions of plurality.


THE REALITY CLUB: On "Signatures of Consciousness: A Talk by Stanislas Dehaene"

Steven Pinker, Donald Hoffman, Arnold Trehub


ARNOLD TREHUB: I agree with Steve Pinker that a global workspace is a key function of consciousness, but it is not an explanation of consciousness. In order to understand consciousness we have to explain how the brain is able to represent a volumetric world filled with objects and events from our own privileged egocentric perspective — the problem of subjectivity. This challenge is compounded by the fact that we have no sensory apparatus for detecting the 3D space in which we live. [...]

DONALD HOFFMAN: ...his assumption that biological systems are too warm for quantum computing appears to be empirically false. His assumption of reductive functionalism, despite being widely shared by researchers in the field, is provably false. And his assumption that consciousness is accomplished by the brain, again widely shared by researchers in the field, needs to be tested by simulations of evolutionary games that investigate the shaping of perception by natural selection. [...]

STEVEN PINKER: I have always thought that the global-workspace theory is the best explanation of the function of consciousness, and coming from a completely different direction (language), I've argued, like Dehaene, that the ability of an analog brain to emulate a digital, combinatorial symbol processor is the key to human intelligence and perhaps the most profound problem in cognitive neuroscience. [...]


ARNOLD TREHUB
Psychologist, University of Massachusetts, Amherst; Author, The Cognitive Brain


Stan Dehaene has done excellent work in exploring the neuronal correlates of the brain's global workspace. But we have to recognize that what he and his colleagues are measuring are the brain changes in response to a novel perception of a previously masked object by a person who is already conscious. I agree with Steve Pinker that a global workspace is a key function of consciousness, but it is not an explanation of consciousness. In order to understand consciousness we have to explain how the brain is able to represent a volumetric world filled with objects and events from our own privileged egocentric perspective — the problem of subjectivity. This challenge is compounded by the fact that we have no sensory apparatus for detecting the 3D space in which we live. Recent work combining empirical measures of phenomenal experience, brain imaging, and detailed neuronal modeling, are making encouraging progress in our effort to understand consciousness and subjectivity.


DONALD HOFFMAN
Cognitive Scientist, UC, Irvine; Author, Visual Intelligence

Although the relation between brain and consciousness remains unresolved, real advances are afoot; the fascinating studies by Dehaene and his collaborators are among the more promising. Nevertheless, because the problem remains unresolved, it is prudent to question assumptions, even ones deeply held.

Dehaene assumes, explicitly, that quantum computing is irrelevant to understanding consciousness in the brain because the brain is too warm. Coherence is essential to quantum computing, and current technology cannot avoid decoherence in warm macroscopic objects.

But, apparently, bacteria can do what technology cannot. Engel and collaborators announced in Nature in 2007 that photosynthesis in the green sulfur bacterium Chlorobium tepidum involves wavelike energy transfer through quantum coherence. Quantum computation appears to be essential to the remarkable efficiency of photosynthesis in this bacterium and, probably, in plants. Photosynthesis evolved more than 3.5 billion years ago; perhaps quantum computation has had time to evolve in other biological systems, including the brain.

Indeed, natural selection might favor quantum computation. Quantum game theory has discovered games in which quantum strategies defeat all classical strategies. In the prisoners' dilemma, for instance, a superposition strategy defeats cooperate and defect strategies, and resolves the prisoners' dilemma by being both Pareto optimal and a Nash equilibrium. This has obvious implications for evolutionary game theory. Biological games might arise in which quantum strategies are evolutionarily stable. Natural selection could then drive these quantum strategies to fixation, but only if such strategies are viable in warm biological systems. Photosynthesis suggests that they are.

If natural selection has on occasion favored quantum computation, then why don't neuroscientists today see evidence for quantum computation in brain processes? Probably for the same reason that neuroscientists working prior to, say, the 1946 invention of the ENIAC computer didn't see evidence for classical computation in brains. What one can see depends on one's training. Neuroscientists today are well versed in classical computation; few know the rudiments of quantum computation. Perhaps the next generation of neuroscientists, familiar with writing quantum algorithms for their quantum laptops, will peer inside brains and see quantum wizardry that is not seen today.

Dehaene proposes that there is an "identity between slow serial processing and conscious processing." This proposal assumes reductive functionalism, viz., the doctrine that consciousness is identical to certain functional processes of the brain. This assumption is widespread among researchers studying consciousness. As a scientific hypothesis it must, of course, be falsifiable. Unfortunately, the "scrambling theorem," published in 2006, proved that reductive functionalism is false. The proof of this theorem requires the assumption that conscious experiences can be represented mathematically, e.g., by sets. But the same is required by any theory of conscious experiences that meets normal standards of rigor. Thus Dehaene (along with many others in the field) makes an assumption (viz., reductive functionalism) that is not just unlikely, but provably false.

Dehaene also assumes that consciousness is accomplished by the brain (although not by one area alone). This is again a widespread assumption, but one that can be questioned on evolutionary grounds. The question is deep: What is the relation between objective reality and our perceptions of that reality as shaped by evolution? Natural selection favors perceptions that increase the chance of having kids. It has endowed us with perceptions of spatiotemporal objects. Are our perceptions, in terms of space and time and objects, a genuine insight, or simply a species-specific and niche-specific adaptation?

This is not a rhetorical question. It can be addressed rigorously with the tools of evolutionary game theory. We can create whatever artificial worlds we wish and whatever perceptual strategies we wish. We can let these strategies compete and find out which survive and which go extinct.

Suppose it turns out that what survives are perceptions that resemble reality no more than the word "dog" resembles the animal? In this case there would still be a systematic relation between between perception and reality, just as there is a systematic relation between words and their referents. But we could no more infer the properties of reality by examining objects in space and time than we could infer the properties of a dog by examining "dog."

We perceive the brain as an object in space and time. When we assume that consciousness is accomplished by the brain, we are assuming that our perceptions are, to some extent, genuine insights into objective reality. This is an empirical assumption that must be tested using evolutionary game theory. If it is false, then no wonder the "hard problem" is so hard. If it is true, then we can proceed with confidence to look for a theory of how consciousness is accomplished by the brain. Determining whether it is true or false is a matter for simulation, not speculation.

In summary, Dehaene's studies are a genuine and interesting advance. However his assumption that biological systems are too warm for quantum computing appears to be empirically false. His assumption of reductive functionalism, despite being widely shared by researchers in the field, is provably false. And his assumption that consciousness is accomplished by the brain, again widely shared by researchers in the field, needs to be tested by simulations of evolutionary games that investigate the shaping of perception by natural selection. If perception is likely to be a species-specific hack rather than a genuine insight, then we must question carefully any causal inferences we make relating brain processes and conscious processes.


STEVEN PINKER
Harvard College Professor and Johnstone Family Professor of Psychology, Harvard University; Author, The Stuff of Thought

"Signatures of Consciousness" reminds me of why I admire the work of Stan Dehaene so much. He zeroes in on deep problems, avoids cute and glib answers, absorbs the ideas of those who worked before him, and always comes up with theories that are both interesting and well-supported. In this presentation he wisely avoids the so-called "hard problem of consciousness" (why it subjectively feels like something to be a functioning brain) and concentrates on just the aspect of consciousness that are scientifically tractable: why some products of neural information processing are accessible to a wide range of cognitive, affective, and linguistic processes and others are not.

I have always thought that the global-workspace theory is the best explanation of the function of consciousness, and coming from a completely different direction (language), I've argued, like Dehaene, that the ability of an analog brain to emulate a digital, combinatorial symbol processor is the key to human intelligence and perhaps the most profound problem in cognitive neuroscience. His theory and data (both neurobiological and behavior) hang together nicely, and represent a real advance. The term "easy problem of consciousness" used to be an in-joke — the science of consciousness is "easy" only in comparison with the philosophical conundrum of subjectivity — but Dehaene is helping to make it easy in practice.


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