Decoding the puzzle of human consciousness.
Might humans be the only species on this planet to be truly conscious? Might lobsters and lions, beetles and bats be unconscious automata, robotically responding to their worlds with no hint of subjective experience?
Aristotle certainly thought so, claiming that humans have rational souls while other animals have only the instincts needed to survive. In medieval Christianity, the “great chain of being” placed humans above soulless animals and below only God and the angels. And the 17th-century French philosopher René Descartes argued that animals have only reflex behaviors.
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Yet the more biology we learn, the more obvious it is that we share not only anatomy, physiology and genetics with other animals but also systems of vision, hearing, memory and emotional expression. Could it really be that we alone have an extra special something—this marvelous inner world of subjective experience?
The question’s hard because although your own consciousness may seem the most obvious thing in the world, it is perhaps the hardest to study. We don’t even have a clear definition beyond appealing to a famous question asked by philosopher Thomas Nagel back in 1974: “What is it like to be a bat?”
Nagel chose bats because their lives are so different from our own. We may try to imagine what it’s like to sleep upside down or to navigate the world using sonar, but does it feel like anything at all?
And that’s the crux here: If there’s nothing it is like to be a bat, we can say a bat isn’t conscious. If there is something (anything) it is like for the bat, it is conscious. But who can know for sure?
We have a lot in common with bats: we have ears, and we can at least imagine our arms as wings. But now try to imagine being an octopus. You’ve got eight curly, grippy, sensitive arms for getting around and catching prey but no skeleton, so you can squeeze yourself through tiny spaces. Only a third of your neurons are in a central brain; the rest are found in the nerve cords in each of your eight arms. So: Is it like something to be a whole octopus, to be its central brain or to be a single octopus arm? The science of consciousness provides no easy way of finding out.
Even worse is what philosopher David Chalmers dubbed the “hard problem” of consciousness: How does subjective experience arise from objective brain activity? How can physical neurons, with all their chemical and electrical communications, create the feeling of pain, the glorious red of the sunset or the taste of fine claret? This is a problem of dualism: How can mind arise from matter? Indeed, does it?
The answer to this question still divides consciousness researchers. On one side is the “B Team,” as philosopher Daniel C. Dennett described them in a heated debate. Members of this group agonize about the hard problem and believe in the possibility of the “philosophical zombie,” an imagined creature indistinguishable from you or me but that has no consciousness.
The possibility of such zombies means other animals might be seeing, hearing, eating, mating “in the dark,” with no subjective experience at all. If that’s the case, consciousness must be some special additional capacity that we evolved either with or without and that, many would say, we’re lucky to have.
On the other side is the A Team: scholars who reject the possibility of zombies and think the hard problem is, to quote philosopher Patricia Churchland, a “hornswoggle problem” that obfuscates the issue.
Either consciousness just is the activity of bodies and brains, or it inevitably comes along with everything we so obviously share with other animals. In the A Team’s view, there’s no point in asking when or why “consciousness itself” evolved or what its function is because “consciousness itself” doesn’t exist.
Pain and Suffering
So why does all this matter? One reason involves the implications of pain and suffering.
When I accidentally step on my cat’s tail and she screeches and shoots out of the room, I’m sure I’ve hurt her. That sounds like a reasonable assumption on my part, but behavior can be misleading. For example, if we were to place pressure sensors in the tail of a robotic cat to activate a screech when stepped on, we wouldn’t think the robot suffered pain when we stomped on its tail.
Many people become vegetarians because of the way farm animals are treated. But are those poor cows and pigs pining for the great outdoors? Do battery hens suffer horribly in their tiny cages? Behavioral experiments show that although hens enjoy scratching about in litter and will choose a cage with litter if access is easy, they won’t bother to push aside a heavy curtain to get to it. So do they not much care?
When lobsters and crabs are taken out of water or have a claw twisted off, they release stress hormones similar to human cortisol and corticosterone. This response provides a physiological reason to believe they suffer. An even more telling demonstration is how, when injured prawns limp and rub their wounds, this behavior can be reduced by giving them the same painkillers that would reduce our own pain.
We see something similar with fish. When zebra fish were given a choice between a tank with gravel and plants and a barren one, they chose the interesting tank. But if they were injected with acetic acid and the barren tank contained a painkiller, they swam to the barren tank instead. Fish pain may be simpler or different in other ways from our own, but these experiments suggest they do feel pain.
Still, some people remain unconvinced. Australian biologist Brian Key argues that fish may respond as though they’re in pain, but this doesn’t prove they’re consciously feeling anything. Noxious stimuli, he asserted in the open-access journal Animal Sentience, “don’t feel like anything to a fish.”
Human consciousness, Key argues, relies on signal amplification and global integration, and fish lack the neural architecture that makes these connections possible. In effect, Key rejects all the behavioral and physiological evidence, relying on anatomy alone to uphold the uniqueness of humans.
A World of Different Brains
If such studies can’t resolve the issue, perhaps comparing brains might help. Could humans be uniquely conscious because of their large brains?
British pharmacologist Susan Greenfield suggests that consciousness increases with brain size across the animal kingdom. But if she’s right, then African elephants and grizzly bears are more conscious than you are, and Great Danes and Dalmatians are more conscious than Pekinese and Pomeranians. And that makes no sense.
More relevant than size may be aspects of brain organization and function that scientists think are indicators of consciousness. Almost all mammals and most other animals—including many fish and reptiles and some insects—alternate between waking and sleeping states or at least have strong circadian rhythms of activity and responsiveness. Specific brain areas, such as the lower brain stem in mammals, control these states.
In the sense of being awake, then, most animals are “conscious.” Still, this isn’t the same as asking whether they have conscious content: whether there’s something it is like to be an awake slug or a lively lizard.
Many scientists, including Francis Crick and, more recently, British neuroscientist Anil Seth, have argued that human consciousness involves widespread, relatively fast, low-amplitude interactions between the thalamus (a sensory way station in the core of the brain) and the cortex (the gray matter at the brain’s surface). These “thalamocortical loops,” they claim, help to integrate information across the brain and thereby underlie consciousness.
If this is correct, finding these features in other species should indicate consciousness. Seth concludes that because other mammals share these structures, they are therefore conscious. Yet many other animals don’t share them: lobsters and prawns, for example, have no cortex or thalamocortical loops. Perhaps we need more specific theories of consciousness to find the critical features.
Among the most popular is global workspace theory (or GWT), originally proposed by American neuroscientist Bernard Baars. The idea is that human brains are structured around a workspace, something like working memory. Any mental content that makes it into the workspace, or onto the brightly lit “stage” in the theater of the mind, is then broadcast to the rest of the unconscious brain. This global broadcast is what makes individuals conscious.
This theory implies that animals with no brain, such as starfish, sea urchins and jellyfish, couldn’t possibly be conscious. Nor could those whose brains lack the right global workspace architecture, including fish, octopuses and many other animals. Yet, as we’ve already explored, a body of behavioral evidence implies that they are conscious.
Another approach called integrated information theory (or IIT) was originally proposed by neuroscientist Giulio Tononi. It’s a math-based theory that defines a quantity called “phi,” which is a measure of the extent to which information in a system is both differentiated into parts and unified into a whole.
Various ways of measuring phi lead to the conclusion that large and complex brains like ours have high phi, deriving from amplification and integration of neural activity widely across the brain. Simpler systems have lower phi, with differences also arising from the specific organization found in different species.
Unlike global workspace theory, IIT implies that consciousness might exist in simple forms in the lowliest creatures, as well as in appropriately organized machines with high phi.
Both these theories are currently considered contenders for a true theory of consciousness. But when it comes to animal consciousness, their answers clearly conflict.
The Evolving Mind
Unfortunately, our behavioral, physiological and anatomical studies all give mutually contradictory answers, as do the two most popular theories of consciousness. Perhaps it would help to explore how, why and when consciousness evolved.
Here again we meet that gulf between the two groups of researchers. Those on the B Team assume that because we’re obviously conscious, consciousness must have a function, such as directing behavior or saving us from predators. Yet their guesses as to when consciousness arose range from billions of years ago right up to historical times.
For example, psychiatrist and neurologist Todd Feinberg and biologist Jon Mallatt offer, without giving compelling evidence, an opaque theory of consciousness involving “nested and nonnested” neural architectures and specific types of mental images. These, they claim, are found in animals from 560 million to 520 million years ago.
Bernard Baars, the author of global workspace theory, ties the emergence of consciousness to that of the mammalian brain around 200 million years ago. And British archaeologist Steven Mithen points to the cultural explosion that started 60,000 years ago when, he contends, separate skills came together in a previously divided brain.
Psychologist Julian Jaynes agrees that a previously divided brain became unified but claims this happened much later. Finding no evidence of words for consciousness in the Greek epic the Iliad, he concludes that the Greeks were not conscious of their own thoughts in the same way that we are, instead attributing their inner voices to the gods. Therefore, Jaynes argues, until 3,000 years ago people had no subjective experiences.
Are any of these ideas correct? Well, they’re all mistaken, according to those on the A Team, because consciousness has no independent function or origin: it’s just not that kind of thing.
A Team members include “eliminative materialists” such as Patricia and Paul Churchland, who maintain that consciousness just is the firing of neurons and that one day we’ll come to accept this in the way we accept that light just is electromagnetic radiation… IIT also denies a separate function for consciousness because any system with sufficiently high phi must inevitably be conscious.
Neither of these theories makes human consciousness unique, but one final idea might. This is the well-known, though much misunderstood, claim that consciousness is an illusion. This approach doesn’t deny the existence of subjective experience but claims that consciousness and the self aren’t what they seem.
Illusionist theories include psychologist Nicholas Humphrey’s idea of a “magical mystery show” being staged inside our heads. Out of our ongoing experiences, Humphrey says, the brain concocts a story that serves an evolutionary purpose: it gives us a reason for living.
Then there’s neuroscientist Michael Graziano’s attention schema theory, in which the brain builds a simplified model of what it’s paying attention to and how. When linked to a model of self, this idea allows the brain—or potentially even a machine—to describe itself as having conscious experiences.
By far the best-known illusionist hypothesis, however, is Dennett’s “multiple drafts theory.” According to this theory, brains are massively parallel systems with no central theater in which an “I” sits viewing and controlling the world. Instead multiple drafts of perceptions and thoughts are continually processed, and none is conscious or unconscious until the system is probed and elicits a response. Only then do we say the thought or action was conscious; thus, consciousness is an attribution we make after the fact.
Dennett relates this to the theory of memes—a meme being information copied from person to person, including words, stories, technologies, fashions and customs. Because humans are capable of widespread generalized imitation, we alone can copy, vary and select among memes, giving rise to language and culture. “Human consciousness is itself a huge complex of memes,” Dennett writes in his book Consciousness Explained, and the self is a “‘benign user illusion.”
This complex of memes is what I call the “selfplex”: an illusion that we are a powerful self that has consciousness and free will—which may not be so benign.
Paradoxically, our unique capacity for language, autobiographical memory and the false sense of being a continuing self might actually serve to increase our suffering. While other species may feel pain, at least they can’t make it worse by crying out, “How long will this last? Will it get worse? Why me? Why now?” In this sense, our suffering may be unique.
For illusionists such as myself, the answer to our question is simple and obvious. We humans are unique because we alone are clever enough to be deluded into believing that there is a conscious “I.”
Reference: The Hardest Problem. Susan Blackmore in Scientific American Vol. 319, No. 3, 48-53; September 2018. doi:10.1038/scientificamerican0918-48