Consciousness Is Not a Human Invention, but the Definition Is

Nobody Agrees on What Consciousness Is

Here is the state of play: after roughly 2,500 years of organized thinking about consciousness, the people paid to study it cannot agree on a definition. They can tell you what it is not. They can tell you it is hard to explain. They have named the difficulty of explaining it. But they cannot hand you a definition that the person in the next office would sign off on.

Philosopher David Chalmers, in a 1995 paper that launched a thousand dissertations, drew a line between what he called the “easy problems” and the “hard problem.” The easy problems are things like explaining how the brain processes sensory information, integrates data, or controls behavior. These are staggeringly complex, but they are engineering problems: given enough time and funding, neuroscience will crack them. The hard problem is different. The hard problem is why any of this processing is accompanied by subjective experience at all. Why does it feel like something to see the colour red, rather than the information simply being processed in the dark?

That question, as simple as it sounds, has resisted every serious attempt at an answer. We can map which brain regions light up during conscious experience. We can observe the neural correlates. What we cannot do is explain why those correlates produce the inner movie rather than running silently, like a thermostat processing temperature without experiencing warmth.

We Started by Assuming We Were Special

The question of whether animals are conscious is older than the scientific method. But the default answer, for most of Western intellectual history, was no. Rene Descartes, writing in the seventeenth century, declared animals to be betes-machines: biological automata, elaborate clockwork driven by stimulus and response, incapable of thought, feeling, or awareness. A dog yelping when kicked was, in this framework, no different from a bellows wheezing when squeezed. The machinery produced noise. Nobody was home.

Descartes had reasons. His entire philosophy of mind depended on a clean division between thinking substance (the soul, exclusive to humans) and extended substance (matter, which made up everything else, animals included). Granting animals consciousness would have collapsed the distinction. So he did not grant it. The framework was not built from evidence about animal minds. It was built from a prior commitment to human uniqueness, and the evidence was arranged afterward.

This matters because the Cartesian assumption did not die with Descartes. It became the water Western science swam in. For three centuries, studying animal cognition was professionally risky. The sin was called “anthropomorphism,” and it was treated as a graver scientific error than its opposite: denying animals capacities they obviously possessed. Behaviourism, the dominant school of psychology for much of the twentieth century, doubled down: all animal behaviour was stimulus and response. Internal states were unscientific. The question of what an animal experienced was, by methodological decree, not a question at all.

The Evidence for Animal Consciousness Got Too Loud

Things changed. They changed slowly, grudgingly, and against institutional resistance, but they changed.

In 2012, a group of prominent neuroscientists gathered at Cambridge University for the Francis Crick Memorial Conference. They signed the Cambridge Declaration on Consciousness, which stated that “non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess the neurological substrates that generate consciousness.” The declaration was signed in the presence of Stephen Hawking. It was a watershed, though its actual content was something that anyone who had spent time with a dog could have told you for free.

Then, in April 2024, the New York Declaration on Animal Consciousness went further. Signed by researchers including neuroscientist Anil Seth, philosopher David Chalmers, and zoologist Lars Chittka, the declaration stated that there is a “realistic possibility of conscious experience in all vertebrates (including all reptiles, amphibians and fishes) and many invertebrates (including, at minimum, cephalopod mollusks, decapod crustaceans and insects).”

Insects. The scientific establishment, or at least a well-credentialed slice of it, is now saying that bees might be conscious.

The evidence that pushed them there is worth examining. Bumblebees, given small wooden balls in a lab at Queen Mary University of London, rolled them around and rotated them in what researchers could only describe as play: the behaviour had no connection to mating, foraging, or survival. Cleaner wrasse fish passed versions of the mirror test, swimming upside down before their reflections and attempting to scrub off marks placed under their skin. Octopuses avoided chambers where they had previously experienced pain, preferring ones where they had been given anaesthetic, which means they not only felt pain but remembered it and acted on the memory. Crayfish displayed anxiety-like states that were reversible with anti-anxiety medication.

The Real Problem Is the Definition

Here is the thesis: the reason it took science so long to “discover” animal consciousness is not that the evidence was lacking. It is that the definition of consciousness was built, from the start, around the assumption that only humans had it.

When we define consciousness in terms of language, self-report, abstract reasoning, or the ability to discuss philosophy, we are not describing consciousness. We are describing the things humans do with consciousness. That is like defining swimming as “the thing Michael Phelps does” and then concluding that dolphins cannot swim because they lack the butterfly stroke.

Thomas Nagel saw this clearly in 1974. His paper “What Is It Like to Be a Bat?” argued that consciousness exists wherever there is “something it is like” to be a given organism. A bat perceives the world through echolocation, a sensory mode so alien to us that we cannot imagine what it is like from the inside. But the impossibility of imagining it does not mean there is nothing to imagine. Nagel’s point was not that bat consciousness is unknowable. It was that our inability to access it says more about the limits of human imagination than about the inner life of bats.

We keep making the same error in different clothes. We set up tests calibrated to human cognition, administer them to other species, and then act surprised when the results are ambiguous. The mirror test is a perfect example: it assumes that self-recognition is visual, that it involves caring about a mark on your body, and that a creature that fails the test lacks self-awareness rather than simply not caring about marks. Many dog owners can confirm that their dog recognises itself by smell perfectly well. The dog is not failing the test. The test is failing the dog.

Why This Matters

This is not an abstract dispute. How we define consciousness determines how we treat the creatures that have it. If consciousness is a binary switch that clicks on at Homo sapiens and nowhere else, then factory farming is morally uncomplicated, animal experimentation requires no ethical framework, and we can pave over ecosystems without guilt. If consciousness is a spectrum, widely distributed across the animal kingdom, then we have been making ethical decisions based on a factual error for centuries.

The New York Declaration’s third point makes this explicit: “When there is a realistic possibility of conscious experience in an animal, it is irresponsible to ignore that possibility in decisions affecting that animal.” That is a carefully worded sentence. It does not say animals are definitely conscious. It says that the possibility is real enough that pretending otherwise is reckless.

Jonathan Birch, one of the declaration’s architects, told NBC News that the past decade has been “very exciting” for the study of animal minds. “People are daring to go there in a way they didn’t before.” The phrasing is revealing. “Daring.” Studying whether animals have inner lives was, until very recently, an act of professional courage. Not because the evidence was weak, but because the assumption was strong.

The Honest Answer

So what is consciousness? Honestly: we do not know. We do not know what it is, how it arises, or why it exists. The hard problem remains hard. What we do know, with increasing confidence, is that whatever consciousness is, it is not ours alone. The evidence points toward a spectrum, not a switch: a gradient of awareness, experience, and inner life that extends far beyond the species that happened to invent the word for it.

The question was never really “do animals have consciousness?” The question was always “why did we assume they didn’t?” And the answer, when you trace it back through Descartes, through behaviourism, through centuries of theology that placed humans at the centre of creation, is uncomfortably simple: we assumed they didn’t because it was convenient. The intellectual framework served the economic and moral framework. If animals don’t suffer, you don’t have to care. If they don’t experience, you don’t have to ask permission.

The science is catching up to what most pet owners, farmers, and anyone who has locked eyes with an octopus already suspected. Consciousness is probably not a human invention. But the definition of it, the narrow, self-serving, species-specific definition that kept the question closed for three hundred years, absolutely was.

The Hard Problem and Its Anthropocentric Scaffolding

David Chalmers’ 1995 formulation of the hard problem of consciousnessThe question of why brain processes give rise to subjective experience — why there is something it is like to feel pain or see a color, rather than just neural activity. is, on its face, species-neutral. The question “why is the performance of cognitive functions accompanied by experience?” does not specify whose experience, or what kind. But in practice, the hard problem has been investigated almost exclusively through the lens of human phenomenology. The “what it is like” locution, borrowed from Thomas Nagel’s 1974 paper in The Philosophical Review, was specifically designed to highlight the limits of third-person analysis when applied to subjective experience. Yet even Nagel’s bat, chosen precisely for its alien sensorium, served primarily as a foil for exploring what humans cannot imagine rather than what bats actually experience.

The problem runs deeper than individual papers. The entire field of consciousness studies rests on methodological foundations that presuppose human-type consciousness as the paradigm case. We study consciousness by asking subjects to report on their experiences. We validate theories against human phenomenological intuitions. We test for consciousness using mirrors, language, and temporal reasoning: tools calibrated to primate cognition and, more specifically, to the cognitive profile of adult Homo sapiens. The circularity is structural. We defined consciousness by reference to ourselves, built instruments that measure our version of it, and then concluded from the measurements that we are the primary (or sole) possessors.

The Cartesian Inheritance

This circularity has a genealogy. Descartes’ bete-machine doctrine, articulated in the Discourse on Method (1637) and the Meditations (1641), did not merely deny animal consciousness. It made the denial load-bearing for an entire metaphysics. Cartesian dualism required a clean partition between res cogitans (thinking substance, the mind) and res extensa (extended substance, matter). Animals, lacking rational souls, fell entirely on the matter side. Their behaviours, however complex, were hydraulic: nerves as pipes, muscles as springs, animal spirits as the water driving the apparatus.

Descartes proposed two tests for genuine intelligence: the language test (capacity for novel, meaningful speech) and the action test (flexible behaviour across varied contexts). These tests did not emerge from empirical study of animal cognition. They were reverse-engineered from the conclusion. The tests selected for the one capacity Descartes was already committed to treating as the marker of consciousness: discursive reason in a human linguistic mode. Three and a half centuries later, the language test remains oddly persistent: the ability to verbally report on one’s experience is still treated, in many consciousness studies, as the gold standard for confirming its presence.

The behaviourist movement of the twentieth century replaced Cartesian metaphysics with methodological positivism but arrived at a functionally identical conclusion. B.F. Skinner and his successors did not deny animal consciousness on philosophical grounds. They declared it scientifically inaccessible and therefore irrelevant. The effect was the same: a century of psychology in which the question “what does the animal experience?” was not unanswerable but unaskable. The sin of anthropomorphism (attributing human-like inner states to animals) was policed far more aggressively than the sin of anthropodenialThe refusal to recognize psychological continuity between humans and other animals; coined by primatologist Frans de Waal as the inverse of anthropomorphism. (the term coined by primatologist Frans de Waal for the a priori refusal to recognise continuity between human and animal minds).

The Empirical Correction

The Cambridge Declaration on Consciousness (2012) was not, strictly speaking, a scientific discovery. It was a collective acknowledgment that the existing evidence had already outstripped the existing assumptions. Written by Philip Low and edited by Jaak Panksepp, Diana Reiss, David Edelman, Bruno Van Swinderen, and Christof Koch, the declaration stated that “non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibit intentional behaviors.” The declaration specifically named all mammals, all birds, and octopuses.

The New York Declaration on Animal Consciousness (April 2024) extended the scope considerably. Organised by Jeff Sebo (NYU), Kristin Andrews (York University), and Jonathan Birch (London School of Economics), and signed by figures including Anil Seth, Christof Koch, David Chalmers, and Lars Chittka, the declaration identified three tiers of evidence: strong scientific support for consciousness in mammals and birds; a realistic possibility of conscious experience in all vertebrates; and the same realistic possibility in cephalopod mollusks, decapod crustaceans, and insects.

The specific findings that forced this expansion are worth examining in detail. Lars Chittka’s lab at Queen Mary University of London demonstrated that bumblebees engage in behaviour indistinguishable from play: given small wooden balls, bees rolled and rotated them repeatedly, with no connection to foraging, mating, or any identifiable survival function. Masanori Kohda’s research on cleaner wrasse showed that fish passed modified versions of the mirror test, exhibiting novel behaviours (swimming upside down) before reflective surfaces and attempting to remove marks placed under their skin. Robyn Crook’s work on octopus nociceptionThe nervous system's process of detecting and signaling potentially harmful stimuli such as heat or pressure, before they are consciously perceived as pain. demonstrated that octopuses not only respond to painful stimuli but remember the spatial context of pain and actively avoid locations associated with it, preferring locations associated with anaesthetic relief. Separate studies showed that crayfish exhibit anxiety-like states following electrical shocks, states that could be reversed with administration of chlordiazepoxide, a benzodiazepine.

The Definitional Problem Is the Core Problem

The thesis of this article is that the anthropocentrism embedded in consciousness studies is not merely a bias to be corrected. It is the central obstacle to progress on the hard problem itself.

Consider: every major theory of consciousness currently in competition (Integrated Information TheoryA theory of consciousness proposing that conscious experience arises from a system's ability to integrate information, quantified by the measure phi (Φ)., Global Workspace TheoryA theory proposing that consciousness arises when information is broadcast to a brain-wide network, making it widely available to different cognitive processes., Higher-Order Thought theories, Recurrent Processing Theory) was developed primarily to explain human consciousness and tested primarily against human data. When these theories are extended to other species, they produce wildly divergent verdicts. IIT, with its mathematical formalism based on integrated information, potentially attributes consciousness to systems far removed from biological brains. Global Workspace Theory, which requires information to be broadcast to a “global workspace” of interconnected cortical regions, risks excluding any species that lacks the relevant cortical architecture. Higher-Order Thought theories, which require thoughts about thoughts, may exclude most of the animal kingdom by design.

The disagreement is not a minor calibrationThe alignment between self-assessed and actual performance or knowledge. Well-calibrated people accurately estimate their own abilities; poorly calibrated people misestimate. issue. These theories do not disagree about edge cases. They disagree about whether a bee is conscious. The reason they disagree is that each theory operationalises consciousness differently, and each operationalisation carries implicit assumptions about what consciousness must look like: assumptions derived, in every case, from the human instance.

Nagel’s insight remains the sharpest diagnostic tool available. Consciousness, if it exists in a bat, exists in a form we cannot access through imagination. If it exists in a bee, the gap is wider still. The question is not whether we can prove it from the outside. The question is whether our inability to do so is evidence of absence, or evidence of the limits of our epistemic positionA state of knowledge or understanding regarding what can be known about a situation. One's position of access to information and the limitations on what one can verify or claim with certainty.. The history of the field suggests the latter. Every time the tools have improved, the circle of attributed consciousness has expanded. It has never, in the history of the discipline, contracted.

The Ethical Implication Is Not Optional

If consciousness is a spectrum rather than a binary property, the ethical implications are not a philosophical afterthought. They are the practical core of the question. The New York Declaration’s third point states this directly: “When there is a realistic possibility of conscious experience in an animal, it is irresponsible to ignore that possibility in decisions affecting that animal.”

This is a precautionary principle applied to phenomenology. It does not claim certainty. It claims that the cost of being wrong in the direction of denial (treating conscious beings as unconscious, inflicting unrecognised suffering at industrial scale) vastly exceeds the cost of being wrong in the direction of attribution (treating an unconscious system with unwarranted consideration). The asymmetry is not close.

The Cartesian framework served a function. If animals are machines, you can do anything to them. If animals are potentially conscious, you have to justify what you do. The intellectual history of consciousness studies cannot be separated from the economic and moral history of animal use. The definition was never neutral. It was never merely descriptive. It was, from the beginning, a permission structure. (The same question, incidentally, is now being asked about free will: whether the definitions we use serve the truth or serve our comfort.)

What We Actually Know

We do not know what consciousness is. We do not know how subjective experience arises from physical processes. The hard problem remains hard, and anyone who tells you otherwise is selling a theory rather than reporting a discovery.

What we do know is that the evidence for widely distributed consciousness across the animal kingdom has grown steadily and in one direction for decades. We know that the historical reasons for denying animal consciousness were philosophical and economic, not empirical. We know that the definitions of consciousness that excluded animals were not derived from the study of consciousness but from prior commitments about human uniqueness. And we know that every expansion of the circle, from mammals to birds to fish to cephalopods to insects, has been resisted by the same appeal to insufficient evidence, only to be vindicated by the next generation of research.

Consciousness is not a human invention. But the conviction that it must be was one of the most durable and consequential inventions humans ever produced.