The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (38 page)

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Authors: Daniel Bor

BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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There is a way to sidestep these traps, and that is by ignoring behavior and merely investigating the structure and function of a brain, or indeed any computational object, for telltale signs of awareness. The first, crudest attempt is simply to rate an animal according to its brain size. If we use such an index as a rough estimate of consciousness—perhaps by virtue of the provisional argument that more neurons means that more information can be processed in a given brain—then humans come near the top of the table, but are by no means the leaders of the pack. Our brains weigh about 1.3 kilograms, a shade less than the bottlenose dolphin, whose brain weighs in at 1.8 kilograms. The African elephant has a brain that weighs around 6.5 kilograms, nearly five times that of the human. Of all the animals on land or sea, the sperm whale wins comfortably, with a brain that tops 8 kilograms. So if it’s true that brain size alone reflects consciousness, then an intriguing thought is that dolphins, elephants, and some whales have considerably more of it than us.
But in some ways it’s not surprising that a sperm whale has a brain six times the size of our own. After all, sperm whales can weigh nearly a thousand times what we do. Much of that extra brain mass is probably needed to move a body that’s 20 meters long, as well as to keep track of all the other internal states that need to be managed rather more carefully when an animal is larger than most buses. Because of this, most scientists believe that a better comparison to make is the size of a brain
compared to the animal’s body
. The logic behind this is that if a brain is far larger than you’d expect from the animal’s body, then all those extra neurons must be doing something over and above the standard tasks of making the animal move, regulating its states, and so on—and very probably the extra brain matter relates to more complex processing, including consciousness.
Although calculating this brain-to-body ratio is rather more complex than it at first sounds,
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humans come out on top in the entire animal kingdom, with a considerably larger brain than you’d expect for our size and body type. Dolphins aren’t too far behind, followed by chimps, bonobos, orangutans, and gorillas. It’s broadly assumed that an animal’s position on this line is a reasonable reflection of its ability to learn, but we only have circumstantial evidence that our large brains really do reflect our greater consciousness. We also have no idea how consciousness scales with brains—the threshold for consciousness may be a hair’s breadth under the human brain-to-body ratio, or a billionth of it—if even such a threshold exists. Therefore, this biological comparison can only be seen as a suggestive hint of how conscious an animal is.
CHAUVINISTIC ANATOMICAL BOOTSTRAPPING
 
A more promising approach is a kind of bootstrap method, where we learn from humans what parts and processes of the brain are important for consciousness and we then assess the level of similarity between these key features in humans and other animals. The thalamus and prefrontal parietal network are crucial for consciousness in humans. So to what extent do other animals share these structures with us? All vertebrates have a thalamus in some form, but not all have any kind of cortex resembling the prefrontal parietal network. From this line of evidence alone, we’d conclude that our great ape cousins, with a prefrontal parietal network not dissimilar to the human model, have the most similar levels of consciousness to us. Other primates, such as monkeys, have prefrontal and parietal structures that we can broadly match with our own, but the anatomical stretch suggests that their conscious capacity is diminished compared to ours. Most mammals at least have a cortex—and some capacity for consciousness, perhaps—while nonmammals, with little hint of a prefrontal parietal network, may not have any consciousness at all.
But this approach, while at least adding more clues to the collection, feels rather circumstantial. It also discounts the possibility that consciousness could arise in animals with a very different brain to ours.
We tend to think of all those animals that never left the oceans as far more mentally simplistic than us, almost certainly not conscious—which is part of the reason why many people still consider themselves vegetarian if they eat fish. But the octopus’s cognitive skills, if fully known, would raise doubts in many who believe such assumptions. The octopus, although an invertebrate—with no thalamus or cortex to speak of—behaves in ways that utterly belie its primitive label. It has around 500 million neurons, not too far from the numbers in a cat. But the octopus brain is decidedly unusual, with an exceptionally parallel architecture—almost always a positive quality when you are talking about brains. The majority of octopus neurons are to be found not in its brain, but in its arms. In effect, if you include the neuronal bundles in its limbs, the octopus has nine semi-independent brains, making it unique in the animal kingdom. The octopus is also a genius among ocean creatures. It has highly developed memory and attentional systems. In nature, this allows these invertebrates to take on a wide range of shapes to mimic other animals, rocks, or even plants. In the lab, octopuses can distinguish shapes and colors, navigate through a maze, open a jar with a screw-on lid, and even learn by observing the behavior of another octopus—an ability thought previously only to exist in highly social animals.
David Edelman, who studies octopus cognition with Graziano Fiorito, has spoken of his uncanny experiences upon entering the octopus room in the grand pillared basement of their palatial Naples zoological department. All of the octopuses immediately press their faces to the sides of their tanks and carefully, continuously track the movements of this new intruder. Such sustained attention is normally only found in obviously intelligent animals. If octopuses are conscious of their world, then we would simply never realize it from this comparison of brain anatomy, as their brains are utterly unlike human or even mammalian brains.
QUANTIFYING CONSCIOUSNESS
 
While all these approaches in concert help inform the debate about animal consciousness, one theory stands out in its promise of a definitive solution. Giulio Tononi’s information integration theory is a well-regarded, modern theory of consciousness. It promises a single number for conscious level, calculated from the measure of the number of neurons in a brain, how they are wired together, and how they interact. In principle, this could show, to pluck numbers out of the air, that fully awake humans have a consciousness of 100 units, coma patients 2 units, chimps 50, rats 10, and so on.
A clear consequence of this theory is that virtually every animal will have some value for its consciousness level. A honeybee, for instance, with nearly a million neurons, certainly will. Even the simple nematode worm,
C. elegans
, with its 302 neurons, will have a value for its level of consciousness, although this figure will admittedly be minuscule. It’s even conceivable that a colony of ants would, under this system, be collectively classed as conscious. Some people are uncomfortable with the notion that such lowly creatures could even have a minimal level of consciousness, let alone a group of animals. Although it is true that more work needs to be carried out to validate this theory, it may turn out that such skeptical intuitions may be wrong. It may well be that any kind of brain, however small or simple, will generate some level of consciousness. The fruit fly, for instance, shows signs of a rudimentary attentional system, which is certainly one of the prime mental components of consciousness.
Tononi’s information integration theory is also compatible with the notion that computers or robots will at some point have consciousness—and we could in principle use the mathematics of the model to rate the level of consciousness of some artificial being according to its network equivalent of a brain.
However, this theory—and indeed all current theories linking consciousness with joined-up information in a network—rules out consciousness in bacteria and plants, despite their rudimentary computational processes. There simply is no information network to speak of, nor, returning to my main thesis, is there any capacity for the creature, in the moment, to combine lower-level information to form a more meaningful chunk.
In practice, things aren’t so simple. As the theory stands in its current form, the number of computations required to calculate this consciousness number scales up ferociously with the number of nodes, or neurons, so that even with a simplistic simulation of the humble
C. elegans
, with its 302 neurons, it would take 5 × 10
79
years on a standard PC to calculate its level of consciousness—by which point the universe may no longer exist! Whatever the other strengths of this theory, unfortunately it cannot practically be used to measure the conscious levels of any animal, and certainly not of humans.
However, there are researchers, including my current lab colleagues Adam Barrett and Anil Seth, who are working hard to adapt the theory to make it practically computable for large-scale systems like the human brain. So in all likelihood there may be effective ways of calculating the level of consciousness of any being within the next decade, at least based on Tononi’s theory. All that would be required would be a mathematical algorithm applied to an approximation of the number of neurons (or artificial nodes) and the connections between them in a given brain—data that are already available for many species.
Rather than waiting for the mathematicians to adapt this measure of consciousness so that the calculations don’t take the age of the universe, Giulio Tononi, along with his colleague Marcello Massimini, has already been developing an intriguing method by which to make a practical rough-and-ready approximation. The experiment uses EEG to record brain waves as well as a transcranial magnetic stimulation (TMS) machine. TMS involves a figure-eight device about the size of a small book that is placed on the scalp. This machine is in fact a powerful electromagnet. The magnet is turned on for a fraction of a second, which causes the cortical neurons under the scalp, at the center of the figure-of-eight coil, to fire. All that the subject feels (I’ve experienced TMS myself multiple times) is a kind of tap on the head. In this particular experiment, the only task the volunteers had to perform was to nod off while the TMS pulses were delivered every couple of seconds. If the subjects were awake, the TMS would cause a spike of brain waves that would spread almost all over the brain during the next few hundred milliseconds or so. When the subjects drifted off to a dreamless sleep, although the initial spike of activity was greater, it would die down faster, and would remain only at the local site that was stimulated by the TMS machine. This study shows firsthand how, in wakefulness, information can flow freely across our entire cortical surface, but when we’re asleep, although the neurons are just as capable of firing, they only weakly transmit their information to their nearest neighbors. Massimini and Tononi see this as evidence that our ability to combine information throughout much of the cortex is high when we’re awake, but low when asleep (these data are also applicable to other consciousness theories, however).
Although at present this method can do little more than distinguish between wakefulness and sleep, plans are afoot to turn it into a far more sensitive measure. Massimini and his group are starting to use the complexity in the EEG wave, rather than how far it travels and for how long, as a more accurate way of gauging level of consciousness. Soon one of these techniques may be able to generate a practical index of consciousness. This quantification of the level of awareness could be applied to any normal subject, whether awake or asleep, as well as any patient, or indeed many animals. Similar methods could even be developed in the future to perturb the activations of an artificial being. Therefore, within the next decade or so, we may well have a viable means of measuring and comparing consciousness in humans and many other animals.
ETHICAL IMPLICATIONS
 
How can a science of consciousness assist the moral conundrums surrounding issues such as animal rights, or human abortion? This is certainly not a book on ethics, and these questions are fiendishly complex. All I will offer here, then, are a few personal thoughts on the matter, informed by my understanding of the science of consciousness.
In ethics, a broad distinction is often made between two very different frameworks: The first is a rights-based system, with laws against murder and theft being obvious examples. The second type of ethical mechanism, in contrast, centers only on a calculation of the net pleasure and suffering of a given population. Economics and its obsession with money would be a rough approximation to this second stance.
If we were to talk about the first system, of rights, such as the right to life and to freedom from easily avoidable suffering, then any animal that has a broad potential for consciousness would also have a significant capacity to suffer, and should fall under the umbrella of such rights, preferably as enshrined in law. Personally, I would want to live in a society that would err on the side of caution in order to ensure that suffering in innocent creatures by our powerful hands was minimized.
One international movement, the Great Ape Project, has aims that mirror these, though with limited scope. Backed by renowned scientists such as Jane Goodall and Richard Dawkins, this movement is pushing for a United Nations declaration to ensure that all great apes (chimpanzees, bonobos, orangutans, and gorillas) have a right to life and freedom from torture. I believe that based on the current scientific picture of animal consciousness, governments around the world should not only accept this view but also seriously consider extending its scope. In the scientific thesis that I have defended here, consciousness is most closely aligned with innovation. Tool invention and use, which require innovative, flexible thoughts, are therefore strong indicators of an extensive consciousness. This would class not just our great ape cousins, but also, at the very least, monkeys, corvids, dolphins, and octopuses as creatures that deserve protection under our laws. Experiments have additionally shown that various nonhuman species can master self-recognition in a mirror and demonstrate self-doubt. Given that we’d automatically take these skills as evidence of a rich form of consciousness in ourselves, we should cautiously accept the same conclusion for any other animals that use such abilities. The list of animals that use tools, recognize themselves in a mirror, or exhibit self-doubt would currently include not only the great apes, but also dolphins, monkeys, elephants, pigs, corvids, and octopuses—although the list will almost certainly grow as more tests are carefully carried out. Barring all these animals from being subject to experiments that would cause suffering, removing them from our food industry, and making it a crime to harm or kill such animals would be a radical step, and not one that I can see any political leader advocating any time soon. Nevertheless, it would be a consistent and caring departure from the way we currently view animals, and would acknowledge the advances in our scientific understanding of the mental lives of these other species.

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