For other mammals and birds, the scientific support is strong. For fishes, octopuses and insects, the most careful statement available says only that conscious experience is a realistic possibility — which is not yes. That is the wording of the 2024 New York Declaration on Animal Consciousness, and the gap between it and the headlines is the story.
Most pages on this question are either sentimental or a list of clever-animal anecdotes. The hard part was never whether animals do impressive things, but what any behavior can tell you about whether there is something it is like to be the one doing it.
What does the New York Declaration on Animal Consciousness actually say?
On 19 April 2024 at New York University, researchers in animal cognition, neuroscience and philosophy — led by Kristin Andrews, Jonathan Birch and Jeff Sebo — published the New York Declaration on Animal Consciousness. Headlines reported it as scientists declaring insects conscious. It says something more restrained, and more interesting.
The Declaration makes a graded claim, not a flat one. It states that there is strong scientific support for attributing conscious experience to other mammals and to birds. It then says something weaker and more careful about everyone else: the empirical evidence indicates at least a realistic possibility of conscious experience in all vertebrates — reptiles, amphibians and fishes included — and in many invertebrates, among them cephalopods such as octopuses, decapod crustaceans such as crabs and lobsters, and insects. And it draws a practical conclusion rather than a metaphysical one: where there is a realistic possibility of conscious experience in an animal, it is irresponsible to ignore that possibility in decisions affecting that animal. Read closely, the document never declares that a crab or a bee is conscious. It declares that the possibility is live enough that dismissing it is no longer defensible.
That is a claim about how to reason under uncertainty, not a verdict on who is home — the difference between a court convicting and a court finding enough evidence to hear the case. Reporting the second as the first is how a careful document becomes a bad headline.
Which animals is the evidence strongest for?
What moves specialists is rarely the charming anecdote; it is behavior that is flexible rather than fixed. Birds are the clearest case outside mammals. Corvids and parrots solve novel problems, make and modify tools, and plan across contexts in ways that resist explanation as fixed reflex — with forebrain architecture organized quite differently from the mammalian cortex. That decouples experience from mammal anatomy.
Cephalopods are the strangest case. An octopus keeps most of its neurons outside its central brain, and shows individual learning, exploratory handling of novel objects, and responses to injury beyond simple withdrawal. Decapods and insects sit further out — but they show learning that transfers between contexts, and responses to damaging stimuli that trade off against other goals rather than firing automatically.
None of that is proof. Each item is a marker — an observable property some theory of consciousness predicts a conscious system would have. The Stanford Encyclopedia of Philosophy's survey of animal consciousness is careful here: the distributional question (which animals have experience) and the phenomenological question (what their experience is like) come apart, and our methods bear far more directly on the first.
How do you test for something you cannot observe?
The method of the moment is indicator properties: take the leading scientific theories of consciousness, extract from each the functional properties it says a conscious system must have, and assess a system against that list. The clearest published statement of the method is not about animals at all — it is Butlin, Long and colleagues' 2023 assessment of artificial systems, which draws indicators from several theories so that no single contested theory has to be assumed true.
Its limit is structural: indicators inherit the assumptions of the theories they come from. If every theory on the list explains how a brain produces experience, a system without that architecture scores low by construction — not because it lacks experience, but because it was measured with a ruler built for something else.
Underneath sits the older obstacle. Thomas Nagel's 1974 paper What Is It Like to Be a Bat? does not argue that bats are conscious — it assumes it, and asks what follows. What follows is that no third-person description of echolocation tells you what echolocating is like from inside. If that holds, the question has a floor no method reaches. We take the argument apart on its own terms in Nagel's bat argument, explained.
Is animal behavior evidence of experience — or projection?
Here is the skeptical case at full strength.
Behavior underdetermines experience. Every behavior listed above is, in principle, producible by a mechanism with nothing it is like to be. Convergent evolution is the proof of concept: octopus and vertebrate eyes arrived at similar optics from utterly different ancestry. Flexible, injury-avoiding behavior may converge the same way — because it is what any system under selection pressure will do — without carrying experience along with it. We infer minds from behavior in other humans because they are built like us and can tell us. Neither warrant holds for a bee.
The methodological version is Morgan's Canon, the century-old rule against explaining an action by a higher psychological faculty when a lower one will do. It exists because the failure mode runs systematically toward over-attribution. We are pattern-hungry, social animals who see agency in weather.
The substantive version is philosophical. Peter Carruthers has argued from higher-order theories that a mental state is phenomenally conscious only when it is available to be represented by other mental states — so a creature with sophisticated first-order processing and no higher-order capacity could register damage, act on it and learn, with no felt quality anywhere. Daniel Dennett's objection lands lower and harder: intuitions are not evidence, and a discipline running on anecdote and empathy has no way to be wrong.
Take that seriously and the Declaration's caution stops looking like timidity. It looks like the only honest wording available.
If following an argument to the point where it costs the writer something is the kind of reading you want more of, the full case is in the guide.
What does Holopsychism propose about animal consciousness?
What follows is the framework's own reading — a proposal offered for testing, not a finding. Nothing in the Declaration, the marker evidence or the indicator literature supports it over a physicalist account. The evidence above is compatible with the framework; compatibility is not support, and pretending otherwise would be the cheapest move available.
The proposal starts from a distinction ordinary usage collapses. Consciousness, in its stipulated sense here, is pure potential — the structureless field of what can take form, not the state of being awake. Awareness is selection: the act by which potential resolves into one definite configuration rather than another. We set the split out at length in consciousness vs awareness. On this reading a nervous system is not a generator of experience but a receiver, filter and translator of it — argued separately in does the brain create consciousness — or receive it?.
The consequence for animals is the framework's signature claim: resolution is a spectrum, not a hierarchy. A microbe, a bee, an octopus and a human differ in the resolution of reception — how finely their structure resolves what it selects from — not in rank on a ladder of being. Human exceptionalism is rejected explicitly. There is no threshold consciousness switches on at, because nothing is switching on; there are only differences in aperture. The wider account of life as the refinement of receivers sits in the theory section on life and evolution.
Doesn't "resolution" just smuggle the hierarchy back in?
It is the first objection worth making, and the framework has to answer it rather than repeat the slogan. "High-resolution receiver" sounds exactly like "better," and better is a rank.
Resolution, as used here, is a claim about what gets selected, not about how much anyone is there. A wider aperture resolves more; it does not house more of what is being resolved. A creature at lower resolution is not a partial person or an early draft of one — it is a different opening onto the same substrate. If the language implies otherwise, the language has failed.
And here the proposal costs something. If brains receive rather than generate, neural markers are evidence about the receiver — its bandwidth, its tuning — not about whether reception is occurring. The framework therefore cannot tell you where any line falls, and has no test that would. It does not tell you whether a bee is conscious. It says the question may be badly formed, which is a philosophical claim, not a discovery.
Two things it is not. Not panpsychism, which locates mentality in the micro-level constituents of matter; the framework locates structureless potential at the level of the whole, with awareness as a separate act of selection. And holopsychism is this site's coined name for a position, not a recognized academic school.
How could the reading fail? If the best account of every marker — the crab's trade-off, the octopus's exploration, the corvid's plan — turns out to be fully discharged by mechanism with no phenomenal remainder, there is nothing for a receiver to receive. That outcome is live: it is the illusionist's position, and the framework has no result that rules it out.
Where this leaves the question
The most useful thing the Declaration did was change the shape of the burden. The animal question has long been posed as a demand for proof: show me that the fish feels it. The document quietly substitutes a different one — given that the possibility is realistic and the evidence will not close, what do you owe a realistic possibility? That has an answer while the metaphysics stays open, and it survives whichever metaphysics turns out to be right, including this one.
That is an uncomfortable place for a framework to end up, because the practical conclusion does not need the framework at all. It is also the honest one.
Frequently asked questions
Did the New York Declaration say insects are conscious? No. It said the evidence indicates at least a realistic possibility of conscious experience in many invertebrates, including insects, and that ignoring such a possibility in decisions affecting those animals is irresponsible. Its stronger claim — strong scientific support — was restricted to other mammals and birds.
Which animals are most likely to be conscious? On the Declaration's grading, mammals and birds have the strongest support. Other vertebrates — reptiles, amphibians, fishes — and invertebrates including cephalopods, decapod crustaceans and insects fall under the weaker "realistic possibility" wording.
How do scientists test for consciousness in animals? Mainly through indicator or marker properties: features leading theories predict a conscious system would have, such as flexible learning and trade-offs under damaging stimuli. The limitation is that those indicators come from theories built around brains like ours, so they measure resemblance to us more directly than experience.
Can we ever know what an animal's experience is like? Nagel's 1974 argument says no — objective description is systematically incomplete for subjective facts, so we can have good reason to think a bat is conscious while remaining unable to characterize echolocation from inside. Whether that gap is permanent remains disputed.
Does Holopsychism claim animals are conscious? It proposes that awareness differs across organisms by resolution of reception rather than by rank, which rejects any line dividing conscious from non-conscious creatures. That is a proposal, not a result, and the framework cannot currently say where such a line falls or how to test for it.
If the version of this question that refuses both the sentimental answer and the dismissive one is the one you want followed further, the full argument is in the guide.
