As you read this, the physiology of your brain is processing information about your surroundings. This is accompanied by a sense of self, the feeling that you are experiencing something. You are conscious—and that is about all anyone can say with certainty about the mind’s most enigmatic phenomenon.
Almost everything we know about consciousness, along with every philosophical and scientific challenge it raises, is cryptic. The questions that surround it ring with controversy, disagreement, and discord: How are we conscious? What are its origins? What exactly is consciousness?
"Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does."
Unfortunately, there is no universally-accepted answer to this question. The most basic definitions state that consciousness is essentially anything and everything that you experience, but this is hardly a satisfying answer.
The haziness surrounding what consciousness means is indicative of just how little we understand of it. The Stanford Encyclopedia of Philosophy describes it, along with numerous other possible definitions, as, “states one is aware of,” for example, but this leaves plenty of room for debate about the varying levels of awareness in humans and other species. Is a stone conscious? Most would agree that it isn’t, owing to the fact that our intuitions and scientific inquiries lead us to believe a stone isn’t experiencing anything as waves wash over it on a beach, for example.
There are, however, certain qualities that researchers and philosophers generally agree are necessary when attempting to form any interpretation of consciousness. In her book Consciousness: A Brief Guide to the Fundamental Mystery of the Mind, Annaka Harris applies the philosopher Thomas Nagel’s definition from his well-known essay What Is It Like to Be a Bat?: "An organism has conscious mental states if and only if there is something that it is like to be that organism—something it is like for the organism."
This is a good and relatively uncontroversial place to start. There is something it’s like to be you, something it’s like to experience the emotions and sensations inherent in existence. If there is an inner experience taking place, it’s likely that consciousness is present. In defining consciousness in this way, however, we’re immediately confronted with a much harder problem than just qualifying the concept.
“Consciousness is experience itself,” Harris explains, “and it is therefore easy to miss the profound questions staring us in the face in each moment: Why would any collection of matter in the universe be conscious? [....] Is it like something to be a grain of sand, a bacterium, an oak tree, a worm, an ant, a mouse, a dog? At some point along the spectrum, the answer is yes, and the great mystery lies in why the “lights turn on” for some collections of matter in the universe.”
This is known as the hard problem of consciousness, a phrase popularized by the philosopher David Chalmers in his 1995 paper Facing Up to the Problem of Consciousness: “Why should physical processing give rise to a rich inner life at all? It seems objectively unreasonable that it should, and yet it does. If any problem qualifies as the problem of consciousness, it is this one.”
How does consciousness work?
Many, including Chalmers, believe it will be another 50 to 100 years before we get close to solving the hard problem. Meanwhile, scientists have had more success in tackling what has been labeled the soft problem of consciousness, identifying the neural mechanisms involved in producing it.
The soft problem falls well within the scope of existing scientific inquiry. We can map the brain, analyzing what parts are needed to give rise to emotions, feelings of agency, the ability to recognize faces, and more.
Christof Koch, chief scientist for the MindScope program at the Allen Institute of Brain Science, was one of the first researchers to energize the hunt for the physical correlates of consciousness. His collaboration with the late Francis Crick, the molecular biologist whose research was pivotal in uncovering the helical structure of DNA in the early 1950s, established a set of 10 principles to help guide researchers in their attempts to explain consciousness physically, psychologically, and philosophically.
While those explorations haven’t been able to definitively explain the why of consciousness, their work hints at where it might and might not reside in our physiology.
“What happens to consciousness if parts of the cerebellum are lost to a stroke or to the surgeon's knife?” Koch asks in Scientific American. “Very little! Cerebellar patients complain of several deficits, such as the loss of fluidity of piano playing or keyboard typing but never of losing any aspect of their consciousness. They hear, see and feel fine, retain a sense of self, recall past events and continue to project themselves into the future.”
On account of such work, we’re getting tantalizingly close to a more cohesive view of these neural correlates. While the spinal cord and cerebellum don’t seem to play much of a role, the posterior cortical "hot zone,” a region comprising the parietal, occipital, and temporal regions of the posterior cortex does. Remove even a tiny part of this cortex, and at least some of what we associate with conscious living—the ability to see color, motion, and even physical space— is impaired or lost.
We’re also getting better at identifying when consciousness is present in individuals and when it isn’t. After developing a new metric to assess the relationship between brain activity and consciousness called the Perturbational Complexity Index, Marcello Massimini, along with Giulio Tononi and a group of their colleagues, applied it to 43 medical patients who were in some kind of vegetative state. For each of these patients, all previous attempts to establish some kind of communication, and therefore grounds for their being conscious, had failed.
When they applied the PCI, however, nine patients displayed brain activity similar to that of conscious individuals, meaning it’s likely that they were conscious but unable to communicate this fact.
Beauty and the (conscious) Beast
Determining if someone is conscious or not is a crucial distinction in the world of medicine, playing a large role in difficult but necessary conversations about the quality of life and, in some cases, whether or not to end it.
“It is incredible to me there is still a debate over whether animals are conscious and even a debate over whether human beings can know animals are conscious.”
That distinction is just as crucial when considering the consciousness of other forms of life on the planet. Not only would this knowledge further our understanding of consciousness in general, the implications of mislabelling anything unconscious when there is an experience being had are also ethically substantial.
It’s just this potential pitfall that Carl Safina, author of the book Beyond Words: What Animals Think and Feel, stridently campaigns against. Safina considers it patently obvious that much of the animal world is conscious in similar ways to ourselves. In an interview with National Geographic, he points to documented accounts of animals displaying human-like behavior as evidence, like elephants protecting people lost in the wild or humpback whales hiding seals from hunting orcas.
“It is incredible to me there is still a debate over whether animals are conscious and even a debate over whether human beings can know animals are conscious,” he explains. “If you watch mammals or even birds, you will see how they respond to the world. They play. They act frightened when there’s danger. They relax when things are good. It seems illogical for us to think that animals might not be having a conscious mental experience of play, sleep, fear or love.”
Many in the scientific community feel similarly. Writing in Live Science, cognitive ethologist Mark Bekoff argues that thousands of studies validate the existence of animal sentience, saying we should declare their consciousness proven at this point.
In an attempt to formalize these claims, a group of neurophysiologists, neuropharmacologists, cognitive neuroscientists, and neuroanatomists signed The Cambridge Declaration on Consciousness at the Francis Crick Memorial Conference at Cambridge University in 2012.
The document states that a lack of a neocortex doesn’t seem to prevent organisms from experiencing emotional states, concluding that “the weight of evidence indicates that humans are not unique in possessing the neurological substrates that generate consciousness. Nonhuman animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.”
Consciousness in plants: Herb your enthusiasm
The proposition that plants might be conscious, however, is far more divisive. While some researchers believe they possess a version of it, scientists are far from a consensus on the issue. Due to the fact our current understanding of consciousness relies heavily on neural processing infrastructure, many flat-out reject the possibility.
In a paper published in Trends in Plant Science in 2019, a group of researchers led by botanist Lincoln Taiz “consider the likelihood that plants, with their relative organizational simplicity and lack of neurons and brains, have consciousness to be effectively nil.”
Likewise, a 2020 article published in the journal Protoplasma debunks claims of plant consciousness, claiming plants exhibit responsive but not proactive behaviors and that their properties preclude perception of injury or wounding as being painful.
It’s worth noting, however, that other studies have provided curious insights into plant behavior that could indicate some level of conscious activity. Smithsonian Magazine reported in 2018 on the growing body of evidence that shows how trees are more social in behavior than previously thought, communicating and maintaining interdependent relationships with other trees using methods of communication that include electrical signals and underground fungal networks. These networks enable them to exchange nutrients in times of need or send out distress signals as warnings against diseases.
We see similar phenomena in the work of Suzanne Simard, an ecologist at the University of British Columbia who has been studying forests for nearly 35 years. In an interview with the Yale School of the Environment, Simard details her research in the forests of British Columbia, where she discovered paper birch trees and Douglas firs competing and cooperating with each other through these mycorrhizal (pertaining to a relationship between green plants and fungi) networks.
Simard inhabits something of an outpost on the epistemological frontier of scientific inquiry. “I have always been very aware of following the scientific method and of being very careful not to go beyond what the data says,” she states, responding to accusations that she too readily ascribes human traits to the plant life she studies.
“But there comes a point when you realize that that sort of traditional scientific method only goes so far and there’s so much more going on in forests than we’re able to actually understand using the traditional scientific techniques. So I opened my mind up and said we need to bring in human aspects to this so that we understand deeper, more viscerally, what’s going on in these living creatures that are not just these inanimate objects.”
Where does consciousness come from?
Even if we take consciousness as a given in our own species, the question of where it came from still remains.
“Selective enhancement [...] probably evolved sometime between hydras and arthropods—between about 700 and 600 million years ago, close to the beginning of complex, multicellular life.”
In his book Minimal Selfhood and the Origins of Consciousness, the philosopher Rupert D.V. Glasgow argues that consciousness “is a Darwinian adaptation and that as such it confers an advantage upon those organisms that happen to be endowed with it: in concrete terms, the advantage of being able to propel oneself in a direction that is aligned with one’s interests rather than just remaining motionless or moving at random.”
The Attention Schema Theory proposed by Michael Graziano, professor of psychology and neuroscience and Princeton University, claims that consciousness arose from a problem that most brain systems throughout evolution encountered: needing to process a near-constant stream of information. To deal with this, nervous systems developed mechanisms like selective signal enhancement, where a brain directs attention to the neurons that fire most intensely, to filter out and prioritize certain information.
This process can be seen in a wide variety of animals and evolved hundreds of millions of years ago. Writing in The Atlantic, Graziano says, “Selective enhancement [...] probably evolved sometime between hydras and arthropods—between about 700 and 600 million years ago, close to the beginning of complex, multicellular life.”
AST claims that we can trace human consciousness throughout this evolutionary history, with each attention mechanism becoming more complex than the last. Interestingly, Graziano concludes that, because of how early this foundational attention mechanism developed, it provides a scientific basis for consciousness in much of the animal kingdom.
Other, more radical ideas include the theory of consciousness called Panpsychism, the idea that all particles, even those as small as electrons, possess a kind of awareness. According to the theory, these smaller bits of lower-level awareness come together in complex systems like the brain to form the higher consciousness that humans possess.
The theory is plagued by what’s known as the combination problem, however, which is the issue of how the consciousness of many could form a coherent consciousness of one, and no scientific evidence exists to support it.
Finally, there are those who believe that consciousness is the great trick, that it may just be the mind telling itself it’s conscious, rather than it being an inherent property of the brain.
The controversy-courting philosopher Daniel Dennet takes just such a view, explaining in an interview with Tufts University that “consciousness is not a part of the brain. It’s what brains can do [...] It’s not in your genes—in the same way German or English isn’t in your genes. Many of the features of consciousness are things that basically get installed culturally and at mother’s knee. It’s part of your rearing, your upbringing, your learning languages. It’s what you learn language in, and you learn a lot of consciousness, too.”
We’re likely to learn a great deal more about the nature of consciousness before any one origin theory wins out, or before we solve either the hard or the soft problem. Regardless, the contemplations that result from taking even a cursory glance at consciousness are more than daunting and rewarding enough to sustain the curious mind until we get there.