Animal consciousness, oranimal awareness, is thequality or state of self-awareness within an animal, or of being aware of an external object or something within itself.[2][3] In humans,consciousness has been defined as:sentience,awareness,subjectivity,qualia, the ability toexperience or tofeel,wakefulness, having a sense ofselfhood, and the executive control system of the mind.[4] Despite the difficulty in definition, many philosophers believe there is a broadly shared underlying intuition about what consciousness is.[5]
The topic of animal consciousness is beset with a number of difficulties. It poses theproblem of other minds in an especially severe form because animals, lacking the ability to usehuman language, cannot communicate their experiences.[6] It is also difficult to reason objectively about the question because a denial that an animal is conscious is often taken to imply that they do not feel, their life has no value, and that harming them is not morally wrong.[7] For example, the 17th-century French philosopherRené Descartes is sometimes criticised for enabling animal mistreatment through hisanimal machine view, which claimed that only humans are conscious.[8]
Philosophers who consider subjective experience the essence of consciousness also generally believe, as a correlate, that the existence and nature of animal consciousness can never rigorously be known. The American philosopherThomas Nagel spelled out this point of view in an influential essay titledWhat Is it Like to Be a Bat? He said that an organism is conscious "if and only if there is something that it is like to be that organism—something it is likefor the organism"; and he argued that no matter how much we know about an animal's brain and behavior, we can never really put ourselves into the mind of the animal and experience their world in the way they do themselves.[9] Other thinkers, such as the cognitive scientistDouglas Hofstadter, dismiss this argument as incoherent.[10] Several psychologists and ethologists have argued for the existence of animal consciousness by describing a range of behaviors that appear to show animals holding beliefs about things they cannot directly perceive—Walter Veit's 2023 bookA Philosophy for the Science of Animal Consciousness reviews a substantial portion of the evidence.[3]
Animal consciousness has been actively researched for over one hundred years.[11] In 1927, the American functional psychologistHarvey Carr argued that any valid measure or understanding of awareness in animals depends on "an accurate and complete knowledge of its essential conditions in man".[12] A more recent review concluded in 1985 that "the best approach is to use experiment (especiallypsychophysics) and observation to trace the dawning and ontogeny of self-consciousness, perception, communication, intention, beliefs, and reflection in normal human fetuses, infants, and children".[11] In 2012, a group of neuroscientists signed theCambridge Declaration on Consciousness, which "unequivocally" asserted that "humans are not unique in possessing the neurological substrates that generate consciousness. Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neural substrates."[13] In 2024, more than 500 academics and scientists signed theNew York Declaration on Animal Consciousness. The declaration states that there is strong scientific support for consciousness in mammals and birds and that it is a realistic possibility in other vertebrates and many invertebrates. It calls for these considerations to be taken into account in decisions affecting animals.[14]
Themind–body problem in philosophy examines the relationship betweenmind andmatter, and in particular the relationship betweenconsciousness and the brain. A variety of approaches have been proposed. Most are eitherdualist ormonist. Dualism maintains a rigid distinction between the realms of mind and matter. Monism maintains that there is only one kind of stuff, and that mind and matter are both aspects of it. The problem was addressed by pre-Aristotelian philosophers,[15][16] and was famously addressed byRené Descartes in the 17th century, resulting inCartesian dualism. Descartes believed that humans alone possess a non-physical mind, interpreting animal behaviour through amechanistic model that denied animal consciousness.[17]
The rejection of the mind–body dichotomy is found in FrenchStructuralism, and is a position that generally characterized post-warFrench philosophy.[18] The absence of an empirically identifiable meeting point between the non-physical mind and its physical extension has proven problematic to dualism and many modern philosophers of mind maintain that the mind is not something separate from the body.[19] These approaches have been particularly influential in the sciences, particularly in the fields ofsociobiology,computer science,evolutionary psychology, and theneurosciences.[20][21][22][23]
Epiphenomenalism is the theory inphilosophy of mind that mental phenomena are caused by physical processes in the brain or that both are effects of a common cause, as opposed to mental phenomena driving the physical mechanics of the brain. The impression that thoughts, feelings, or sensations cause physical effects, is therefore to be understood as illusory to some extent. For example, it is not the feeling of fear that produces an increase in heart beat, both are symptomatic of a common physiological origin, possibly in response to a legitimate external threat.[24]
The history of epiphenomenalism goes back to the post-Cartesian attempt to solve the riddle ofCartesian dualism, i.e., of how mind and body could interact.La Mettrie,Leibniz andSpinoza all in their own way began this way of thinking. The idea that even if the animal were conscious nothing would be added to the production of behavior, even in animals of the human type, was first voiced by La Mettrie (1745), and then byCabanis (1802), and was further explicated byHodgson (1870) andHuxley (1874).[25][26] Huxley (1874) likened mental phenomena to the whistle on a steam locomotive. However, epiphenomenalism flourished primarily as it found a niche among methodological or scientific behaviorism. In the early 1900sscientific behaviorists such asIvan Pavlov,John B. Watson, andB. F. Skinner began the attempt to uncover laws describing the relationship between stimuli and responses, without reference to inner mental phenomena. Instead of adopting a form ofeliminativism or mentalfictionalism, positions that deny that inner mental phenomena exist, a behaviorist was able to adopt epiphenomenalism in order to allow for the existence of mind. However, by the 1960s, scientific behaviourism met substantial difficulties and eventually gave way to thecognitive revolution. Participants in that revolution, such asJerry Fodor, reject epiphenomenalism and insist upon the efficacy of the mind. Fodor even speaks of "epiphobia"—fear that one is becoming an epiphenomenalist.[citation needed]
Thomas Henry Huxley defends in an essay titledOn the Hypothesis that Animals are Automata, and its History an epiphenomenalist theory of consciousness according to which consciousness is a causally inert effect of neural activity—"as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery".[27] To thisWilliam James objects in his essayAre We Automata? by stating an evolutionary argument for mind-brain interaction implying that if the preservation and development of consciousness in the biological evolution is a result ofnatural selection, it is plausible that consciousness has not only been influenced by neural processes, but has had a survival value itself; and it could only have had this if it had been efficacious.[28][29]Karl Popper develops in the bookThe Self and Its Brain a similar evolutionary argument.[30]
Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain. In his interactions with scientists and other veterinarians, Rollin asserts that he was regularly asked to prove animals are conscious and provide scientifically acceptable grounds for claiming they feel pain.[31] The denial of animal consciousness by scientists has been labelled asmentophobia byDonald Griffin.[32] Academic reviews of the topic are equivocal, noting that the argument that animals have at least simple conscious thoughts and feelings has strong support,[33] but some critics continue to question how reliably animal mental states can be determined.[34][35] A refereed journalAnimal Sentience launched in 2016 by the Institute of Science and Policy ofThe Humane Society of the United States is devoted to research on this and related topics.[36]
About forty meanings attributed to the termconsciousness can be identified and categorized based onfunctions andexperiences. The prospects for reaching any single, agreed-upon, theory-independent definition of consciousness appear remote.[37]
Consciousness is an elusive concept that presents many difficulties when attempts are made to define it.[38][39] Its study has progressively become an interdisciplinary challenge for numerous researchers, including ethologists, neurologists, cognitive neuroscientists, philosophers, psychologists and psychiatrists.[40][41]
In 1976,Richard Dawkins wrote, "The evolution of the capacity to simulate seems to have culminated in subjective consciousness. Why this should have happened is, to me, the most profound mystery facing modern biology."[42] In 2004, eight neuroscientists felt it was still too soon for a definition. They wrote an apology in "Human Brain Function", in which they stated:[43]
Consciousness is sometimes defined as the quality or state of being aware of an external object or something within oneself.[44][45] It has been defined somewhat vaguely as:subjectivity,awareness,sentience, the ability toexperience or tofeel, wakefulness, having a sense ofselfhood, and the executive control system of the mind.[4] Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is.[5]Max Velmans andSusan Schneider wrote inThe Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."[46]
Related terms, also often used in vague or ambiguous ways, are:[citation needed]
Sentience (the ability to feel, perceive, or to experience subjectivity) is not the same as self-awareness (being aware of oneself as an individual). Themirror test is sometimes considered to be an operational test for self-awareness, and the handful of animals that have passed it are often considered to be self-aware.[48][49] It remains debatable whether recognition of one's mirror image can be properly construed to imply full self-awareness,[50] particularly given that robots are being constructed which appear to pass the test.[51][52]
Much has been learned in neuroscience about correlations between brain activity and subjective, conscious experiences, and many suggest that neuroscience will ultimately explain consciousness; "...consciousness is a biological process that will eventually be explained in terms of molecular signaling pathways used by interacting populations of nerve cells...".[53] However, this view has been criticized because consciousness has yet to be shown to be a process,[54] and the so-called"hard problem" of relating consciousness directly to brain activity remains elusive.[55]
SinceDescartes's proposal ofdualism, it became general consensus that the mind had become a matter ofphilosophy and that science was not able to penetrate the issue of consciousness – that consciousness was outside of space and time. However, in recent decades many scholars have begun to move toward a science of consciousness.Antonio Damasio andGerald Edelman are two neuroscientists who have led the move to neural correlates of the self and of consciousness. Damasio has demonstrated that emotions and their biological foundation play a critical role in high level cognition,[56][57] and Edelman has created a framework for analyzing consciousness through a scientific outlook. The current problem consciousness researchers face involves explaining how and why consciousness arises fromneural computation.[58][59] In his research on this problem, Edelman has developed a theory of consciousness, in which he has coined the termsprimary consciousness andsecondary consciousness.[60][61]
Eugene Linden, author ofThe Parrot's Lament suggests there are many examples of animal behavior and intelligence that surpass what people would suppose to be the boundary of animal consciousness. Linden contends that in many of these documented examples, a variety of animal species exhibit behavior that can only be attributed to emotion, and to a level of consciousness that we would normally ascribe only to our own species.[62]
PhilosopherDaniel Dennett counters:
Consciousness requires a certain kind of informational organization that does not seem to be 'hard-wired' in humans, but is instilled by human culture. Moreover, consciousness is not a black-or-white, all-or-nothing type of phenomenon, as is often assumed. The differences between humans and other species are so great that speculations about animal consciousness seem ungrounded. Many authors simply assume that an animal like a bat has a point of view, but there seems to be little interest in exploring the details involved.[63]
Consciousness in mammals (including humans) is an aspect of the mind generally thought to comprise qualities such assubjectivity,sentience, and the ability toperceive the relationship betweenoneself and one'senvironment. It is a subject of much research inphilosophy of mind,psychology,neuroscience, andcognitive science. Some philosophers divide consciousness intophenomenal consciousness, which is subjective experience itself, and access consciousness, which refers to the global availability of information to processing systems in the brain.[64] Phenomenal consciousness has many different experienced qualities, often referred to asqualia. Phenomenal consciousness is usually consciousnessof something orabout something, a property known asintentionality in philosophy of mind.[64]
In humans, there are three common methods of studying consciousness: verbal reporting, behavioural demonstrations, and neural correlation with conscious activity, though these can only be generalized to non-human taxa with varying degrees of difficulty.[65] In a new study conducted inrhesus monkeys, Ben-Haim and his team used a process dissociation approach that predicted opposite behavioral outcomes for the two modes of perception. They found that monkeys displayed exactly the same opposite behavioral outcomes as humans when they were aware or unaware of the stimuli presented.[66]
| External videos | |
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 Self-recognition in apes–National Geographic |
The sense in which animals (or human infants) can be said to haveconsciousness or aself-concept has been hotly debated; it is often referred to as the debate over animal minds. The best known research technique in this area is themirror test devised byGordon G. Gallup, in which the skin of an animal (or human infant) is marked, while they are asleep or sedated, with a mark that cannot be seen directly but is visible in a mirror. The animals are then allowed to see their reflection in a mirror; if the animal spontaneously directs grooming behaviour towards the mark, that is taken as an indication that they are aware of themselves.[68][69] Over the past 30 years, many studies have found evidence that animals recognise themselves in mirrors. Self-awareness by this criterion has been reported for:
Until recently, it was thought that self-recognition was absent in animals without aneocortex, and was restricted to mammals with large brains and well-developed social cognition. However, in 2008, a study of self-recognition incorvids reported significant results for magpies. Mammals and birds inherited the same brain components from their last commonancestor nearly 300 million years ago, and have since independently evolved and formed significantly different brain types. The results of the mirror and mark tests showed that neocortex-lessmagpies are capable of understanding that a mirror image belongs to their own body. The findings show that magpies respond in the mirror and mark tests in a manner similar to apes, dolphins and elephants. The magpies were chosen to study based on their empathy and lifestyle, a possible precursor to their ability to develop self-awareness.[69] For chimpanzees, the occurrence is about 75% in young adults and considerably less in young and old individuals.[78] For monkeys, non-primate mammals, and a number of bird species, exploration of the mirror and social displays were observed. Hints at mirror-induced self-directed behavior have been obtained.[79]
According to a 2019 study,cleaner wrasses have become the first fish ever observed to pass the mirror test.[80] However, the test's inventor Gordon Gallup has said that the fish were most likely trying to scrape off a perceived parasite on another fish and that they did not demonstrate self-recognition. The authors of the study responded that because the fish checked themselves in the mirror before and after the scraping, this meant that the fish had self-awareness and recognized that their reflections belonged to their own bodies.[81][82][83]
The mirror test has attracted controversy among some researchers because it is entirely focused on vision, the primary sense in humans, while other species rely more heavily on other senses such as theolfactory sense in dogs.[84][85][86] A study in 2015 showed that the "sniff test of self-recognition (STSR)" provides evidence ofself-awareness in dogs.[86]
| External videos | |
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| Whale song –Oceania Project | |
| This is Einstein! –Knoxville Zoo |
Another approach to determine whether a non-human animal is conscious derives from passive speech research with a macaw (seeArielle). Some researchers propose that by passively listening to an animal's voluntary speech, it is possible to learn about the thoughts of another creature and to determine that the speaker is conscious. This type of research was originally used to investigate a child'scrib speech by Weir (1962) and in investigations of early speech in children by Greenfield and others (1976).[citation needed]
Zipf's law might be able to be used to indicate if a given dataset of animal communication indicate an intelligent natural language. Some researchers have used this algorithm to study bottlenose dolphin language.[87]
Further arguments revolve around the ability of animals to feelpain orsuffering, which implies consciousness.[88] If animals can be shown to suffer in ways comparable to humans, ethical arguments against human suffering may be extended to animals. Some scholars argue that pain can be inferred from non-purposeful or maladaptive reactions to negative stimuli.[89] One such reaction istransmarginal inhibition, a phenomenon observed in both humans and some animals that resembles mental breakdown.[citation needed]
CosmologistCarl Sagan argues that humans often deny animal suffering to justify practices such as enslavement, experimentation, and consumption. He contends that behavioral similarities between humans and other animals challenge such denials.[90]
John Webster, professor of animal husbandry, argues that suffering is not dependent on intelligence or brain size. He states that sentient animals actively seek pleasure and display behaviors indicating enjoyment, such as basking in the sun.[91]
However, there is no consensus about which organisms are capable of experiencing pain. PhilosopherJustin Leiber discusses varying views:Michel de Montaigne attributes consciousness to insects and even plants, whilePeter Singer andSamuel Clarke deny it in simpler organisms like sponges. Singer places the boundary somewhere between shrimp and oysters, while others speculate about insects, spiders, or tapeworms.[92]
Some critics draw comparisons to plants, questioning whether a focus on animal suffering is entirely distinct. Science writer Carol Kaesuk Yoon describes how plants, when damaged, initiate chemical defenses and repair processes, though these do not necessarily imply consciousness.[93]
Cognitive bias in animals is a pattern of deviation in judgment, whereby inferences about other animals and situations may be drawn in an illogical fashion.[94] Individuals create their own "subjective social reality" from their perception of the input.[95] It refers to the question "Is the glass half empty or half full?", used as an indicator of optimism or pessimism. Cognitive biases have been shown in a wide range of species including rats, dogs, rhesus macaques, sheep, chicks, starlings and honeybees.[96][97][98]
The neuroscientistJoseph LeDoux advocates avoiding terms derived from human subjective experience when discussing brain functions in animals.[99] For example, the common practice of callingbrain circuits that detect and respond to threats "fear circuits" implies that these circuits are responsible for feelings of fear. LeDoux argues that Pavlovian fear conditioning should be renamed Pavlovian threat conditioning to avoid the implication that "fear" is being acquired in rats or humans.[100] Key to his theoretical change is the notion of survival functions mediated by survival circuits, the purpose of which is to keep organisms alive rather than to make emotions. For example, defensive survival circuits exist to detect and respond to threats. While all organisms can do this, only organisms that can be conscious of their own brain's activities can feel fear. Fear is a conscious experience and occurs the same way as any other kind of conscious experience: via cortical circuits that allow attention to certain forms of brain activity. LeDoux argues the only differences between an emotional and non-emotion state of consciousness are the underlying neural ingredients that contribute to the state.[101][102]
Neuroscience is the scientific study of thenervous system.[103] It is a highly activeinterdisciplinary science that collaborates with many other fields. The scope of neuroscience has broadened recently to includemolecular,cellular,developmental,structural,functional,evolutionary,computational, andmedical aspects of the nervous system. Theoretical studies ofneural networks are being complemented with techniques forimaging sensory and motor tasks in thebrain.According to a 2008 paper, neuroscience explanations of psychological phenomena currently have a "seductive allure", and "seem to generate more public interest" than explanations which do not contain neuroscientific information.[104] They found that subjects who were not neuroscience experts "judged that explanations with logically irrelevant neuroscience information were more satisfying than explanations without.[104]
Theneural correlates of consciousness constitute the minimal set of neuronal events and mechanisms sufficient for a specific consciouspercept.[105] Neuroscientists use empirical approaches to discoverneural correlates of subjective phenomena.[106] The set should beminimal because, if the brain is sufficient to give rise to any given conscious experience, the question is which of its components is necessary to produce it.[citation needed]
Visual sense and representation was reviewed in 1998 byFrancis Crick andChristof Koch. They concludedsensory neuroscience can be used as a bottom-up approach to studying consciousness, and suggested experiments to test various hypotheses in this research stream.[107]
A feature that distinguishes humans from most animals is that we are not born with an extensive repertoire of behavioral programs that would enable us to survive on our own ("physiological prematurity"). To compensate for this, we have an unmatched ability to learn, i.e., to consciously acquire such programs by imitation or exploration. Once consciously acquired and sufficiently exercised, these programs can become automated to the extent that their execution happens beyond the realms of our awareness. Take, as an example, the incredible fine motor skills exerted in playing a Beethoven piano sonata or the sensorimotor coordination required to ride a motorcycle along a curvy mountain road. Such complex behaviors are possible only because a sufficient number of the subprograms involved can be executed with minimal or even suspended conscious control. In fact, the conscious system may actually interfere somewhat with these automated programs.[108]
The growing ability of neuroscientists to manipulate neurons using methods from molecular biology in combination with optical tools depends on the simultaneous development of appropriate behavioural assays and model organisms amenable to large-scale genomic analysis and manipulation.[109] A combination of such fine-grained neuronal analysis in animals with ever more sensitive psychophysical and brain imaging techniques in humans, complemented by the development of a robust theoretical predictive framework, will hopefully lead to a rational understanding of consciousness.[citation needed]
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Theneocortex is a part of the brain of mammals. It consists of thegrey matter, or neuronal cell bodies andunmyelinated fibers, surrounding the deeperwhite matter (myelinatedaxons) in thecerebrum. The neocortex is smooth inrodents and other small mammals, whereas inprimates and other larger mammals it has deep grooves and wrinkles. These folds increase the surface area of the neocortex considerably without taking up too much more volume. Also, neurons within the same wrinkle have more opportunity for connectivity, while neurons in different wrinkles have less opportunity for connectivity, leading to compartmentalization of the cortex. The neocortex is divided intofrontal,parietal,occipital, andtemporal lobes, which perform different functions. For example, the occipital lobe contains theprimary visual cortex, and the temporal lobe contains theprimary auditory cortex. Further subdivisions or areas of neocortex are responsible for more specific cognitive processes. The neocortex is the newest part of thecerebral cortex to evolve (hence the prefix "neo"); the other parts of the cerebral cortex are thepaleocortex andarchicortex, collectively known as theallocortex. In humans, 90% of the cerebral cortex is neocortex.[citation needed]
Researchers have argued that consciousness in mammals arises in the neocortex, and therefore by extension used to argue that consciousness cannot arise in animals which lack a neocortex. For example, Rose argued in 2002 that the "fishes have nervous systems that mediate effective escape and avoidance responses to noxious stimuli, but, these responses must occur without a concurrent, human-like awareness of pain, suffering or distress, which depend on separately evolved neocortex."[110] Recently that view has been challenged, and many researchers now believe that animal consciousness can arise fromhomologoussubcortical brain networks.[1] For instance, evidence suggests thepallium inbird brains to be functionally equivalent to the mammalian cerebral cortex as a basis of consciousness.[111][112]
Attention is thecognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources.[113] Attention also has variations amongst cultures. Voluntary attention develops in specific cultural and institutional contexts through engagement in cultural activities with more competent community members.[114]
Most experiments show that oneneural correlate of attention is enhanced firing. If a neuron has a certain response to a stimulus when the animal is not attending to the stimulus, then when the animal does attend to the stimulus, the neuron's response will be enhanced even if the physical characteristics of the stimulus remain the same. In many cases attention produces changes in theEEG. Many animals, including humans, producegamma waves (40–60 Hz) when focusing attention on a particular object or activity.[115]
Extended consciousness is an animal's autobiographical self-perception. It is thought to arise in the brains of animals which have a substantial capacity for memory and reason. It does not necessarily require language. The perception of a historic and future self arises from a stream of information from the immediate environment and from neural structures related to memory. The concept was popularised byAntonio Damasio and is used inbiological psychology. Extended consciousness is said to arise in structures in thehuman brain described asimage spaces anddispositional spaces. Image spaces imply areas wheresensory impressions of all types are processed, including the focused awareness of thecore consciousness. Dispositional spaces include convergence zones, which are networks in the brain where memories are processed and recalled, and where knowledge is merged with immediate experience.[116][117]
Metacognition is defined as "cognition about cognition", or "knowing about knowing."[118] It can take many forms; it includes knowledge about when and how to use particular strategies for learning or for problem solving.[118] It has been suggested that metacognition in some animals provides evidence for cognitive self-awareness.[119] There are generally two components of metacognition: knowledge about cognition, and regulation of cognition.[120] Writings on metacognition can be traced back at least as far asDe Anima and theParva Naturalia of the Greek philosopherAristotle.[121] Metacognologists believe that the ability to consciously think about thinking is unique tosapient species and indeed is one of the definitions of sapience.[citation needed] There is evidence thatrhesus monkeys and apes can make accurate judgments about the strengths of their memories of fact and monitor their own uncertainty,[122] while attempts to demonstrate metacognition in birds have been inconclusive.[123] A 2007 study provided some evidence for metacognition inrats,[124][125][126] but further analysis suggested that they may have been following simpleoperant conditioning principles,[127] or a behavioral economic model.[128]
Mirror neurons areneurons thatfire both when an animal acts and when the animal observes the same action performed by another.[129][130][131] Thus, the neuron "mirrors" the behavior of the other, as though the observer were themselves acting. Such neurons have been directly observed inprimate and other species includingbirds. The function of the mirror system is a subject of much speculation. Many researchers in cognitive neuroscience and cognitive psychology consider that this system provides the physiological mechanism for the perception action coupling (see thecommon coding theory).[131] They argue that mirror neurons may be important for understanding the actions of other people, and for learning new skills by imitation. Some researchers also speculate that mirror systems may simulate observed actions, and thus contribute totheory of mind skills,[132][133] while others relate mirror neurons tolanguage abilities.[134] Neuroscientists such as Marco Iacoboni (UCLA) have argued that mirror neuron systems in the human brain help us understand the actions and intentions of other people. In a study published in March 2005, Iacoboni and his colleagues reported that mirror neurons could discern if another person who was picking up a cup of tea planned to drink from it or clear it from the table. In addition, Iacoboni and a number of other researchers have argued that mirror neurons are the neural basis of the human capacity for emotions such asempathy.[131][135]Vilayanur S. Ramachandran has speculated that mirror neurons may provide the neurological basis of self-awareness.[136][137]
Consciousness is likely an evolvedadaptation since it meetsGeorge Williams' criteria of species universality, complexity,[138] and functionality, and it is atrait that apparently increasesfitness.[139] Opinions are divided as to where in biologicalevolution consciousness emerged and about whether or not consciousness has survival value. It has been argued that consciousness emerged (i) exclusively with the firsthumans, (ii) exclusively with the first mammals, (iii) independently in mammals and birds, or (iv) with the first reptiles.[140]Donald Griffin suggests in his bookAnimal Minds a gradual evolution of consciousness.[141] Each of these scenarios raises the question of the possible survival value of consciousness.[citation needed]
In his paper "Evolution of consciousness,"John Eccles argues that special anatomical and physical adaptations of the mammaliancerebral cortex gave rise to consciousness.[142] In contrast, others have argued that the recursive circuitry underwriting consciousness is much more primitive, having evolved initially in pre-mammalian species because it improves the capacity for interaction with both socialand natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine.[143] Once in place, this recursive circuitry may well have provided a basis for the subsequent development of many of the functions that consciousness facilitates in higher organisms, as outlined byBernard J. Baars.[144]Richard Dawkins suggested that humans evolved consciousness in order to make themselves the subjects of thought.[145] Daniel Povinelli suggests that large, tree-climbing apes evolved consciousness to take into account one's own mass when moving safely among tree branches.[145] Consistent with this hypothesis,Gordon Gallup found thatchimpanzees andorangutans, but not little monkeys or terrestrialgorillas, demonstratedself-awareness in mirror tests.[145]
The concept of consciousness can refer to voluntary action, awareness, or wakefulness. However, even voluntary behaviour involves unconscious mechanisms. Many cognitive processes take place in the cognitive unconscious, unavailable to conscious awareness. Some behaviours are conscious when learned but then become unconscious, seemingly automatic. Learning, especially implicitly learning a skill, can take place outside of consciousness. For example, plenty of people know how to turn right when they ride a bike, but very few can accurately explain how they actually do so.[145]
Neural Darwinism is a large scale theory of brain function initially proposed in 1978 by the American biologistGerald Edelman.[146] Edelman distinguishes between what he calls primary and secondary consciousness:
Primary consciousness can be defined as simple awareness that includesperception andemotion. As such, it is ascribed to most animals. By contrast, secondary consciousness depends on and includes such features as self-reflective awareness,abstract thinking,volition andmetacognition.[60][148]
Edelman's theory focuses on twonervous system organizations: thebrainstem andlimbic systems on one side and thethalamus andcerebral cortex on the other side. The brain stem and limbic system take care of essential body functioning and survival, while the thalamocortical system receives signals from sensory receptors and sends out signals to voluntary muscles such as those of the arms and legs. The theory asserts that the connection of these two systems during evolution helped animals learnadaptive behaviors.[147]
Other scientists have argued against Edelman's theory, instead suggesting that primary consciousness might have emerged with the basic vegetative systems of the brain. That is, the evolutionary origin might have come from sensations and primal emotions arising fromsensors andreceptors, both internal and surface, signaling that the well-being of the creature was immediately threatened—for example, hunger for air, thirst, hunger, pain, and extreme temperature change. This is based on neurological data showing thethalamic,hippocampal,orbitofrontal,insula, andmidbrain sites are the key to consciousness of thirst.[149] These scientists also point out that the cortex might not be as important to primary consciousness as some neuroscientists have believed.[149] Some researchers argue that systematic disruption of cortical regions in nonhuman animals does not prevent consciousness, and that reports of consciousness in children born without a cortex are consistent with this view. On this account, brainstem mechanisms are proposed to play a primary role in consciousness.[149] Still, these scientists concede that higher order consciousness does involve the cortex and complex communication between different areas of the brain.[citation needed]
While animals withprimary consciousness have long-term memory, they lack explicit narrative, and, at best, can only deal with the immediate scene in the remembered present. While they still have an advantage over animals lacking such ability, evolution has brought forth a growing complexity in consciousness, particularly in mammals. Animals with this complexity are said to have secondary consciousness. Secondary consciousness is seen in animals withsemantic capabilities, such as the fourgreat apes. It is present in its richest form in the human species, which is unique in possessing complexlanguage made up ofsyntax and semantics. In considering how the neural mechanisms underlying primary consciousness arose and were maintained during evolution, it is proposed that at some time around the divergence ofreptiles into mammals and then intobirds, theembryological development of large numbers of new reciprocal connections allowed richre-entrant activity to take place between the more posterior brain systems carrying out perceptual categorization and the more frontally located systems responsible for value-category memory.[60] The ability of an animal to relate a present complex scene to their own previous history of learning conferred an adaptive evolutionary advantage. At much later evolutionary epochs, further re-entrant circuits appeared that linked semantic and linguistic performance to categorical and conceptualmemory systems. This development enabled the emergence of secondary consciousness.[150][151]
Ursula Voss of theUniversität Bonn believes that the theory ofprotoconsciousness[152] may serve as adequate explanation for self-recognition found in birds, as they would develop secondary consciousness during REM sleep.[153] She added that many types of birds have very sophisticated language systems. Don Kuiken of the University of Alberta finds such research interesting as well as if we continue to study consciousness with animal models (with differing types of consciousness), we would be able to separate the different forms of reflectiveness found in today's world.[154]
For the advocates of the idea of a secondary consciousness,self-recognition serves as a critical component and a key defining measure. What is most interesting then, is the evolutionary appeal that arises with the concept of self-recognition. In non-human species and in children, themirror test (see above) has been used as an indicator ofself-awareness.[citation needed]
A 2020 paper byJonathan Birch, Alexandra K. Schnell, and Nicola S. Clayton outlined a multidimensional approach to animal consciousness, intended to account for variation in conscious experience across species. The authors propose that consciousness may not be meaningfully represented along a single continuum, and instead suggest five distinct dimensions for constructing species-specific profiles.[155]
The proposed dimensions are:[155]
The authors suggest that this framework could facilitate comparative studies of consciousness in different taxa, including mammals, birds, and cephalopods.[155]
The absence of aneocortex does not appear to preclude an organism from experiencing affective states. Convergent evidence indicates that non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibitintentional behaviors. Consequently, the weight of evidence indicates that humans are not unique in possessing theneurological substrates that generate consciousness. Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.[156]
In 2012, a group of neuroscientists attending a conference on "Consciousness in Human and non-Human Animals" at theUniversity of Cambridge in the UK, signed theCambridge Declaration on Consciousness (see box on the right).[1][157]
This declaration "unequivocally" asserts:[1]
In 2024, a conference on "The Emerging Science of Animal Consciousness" atNew York University[158] producedThe New York Declaration on Animal Consciousness.[14] This brief declaration, signed by over 500 scientists and academics, asserts that, in addition to the strong scientific support for consciousness in mammals and birds agreed on by Cambridge, there is also empirical evidence which "indicates at least a realistic possibility of conscious experience in all vertebrates (including reptiles, amphibians, and fishes) and many invertebrates (including, at minimum, cephalopod mollusks, decapod crustaceans, and insects)."[14][159] The declaration further asserts that "when there is a realistic possibility of conscious experience in an animal, it is irresponsible to ignore that possibility in decisions affecting that animal".[14]
A common image is thescala naturae, the ladder of nature on which animals of different species occupy successively higher rungs, with humans typically at the top.[160] A more useful approach has been to recognize that different animals may have different kinds of cognitive processes, which are better understood in terms of the ways in which they are cognitively adapted to their different ecological niches, than by positing any kind of hierarchy.[161][162]
Dogs were previously listed as non-self-aware animals. Traditionally, self-consciousness was evaluated via themirror test. But dogs, and many other animals, are not (as) visually oriented.[163][164] A 2015 study by biologist Roberto Cazzolla Gatti argues that the "sniff test of self-recognition" (STSR) provides evidence of self-awareness in dogs and that apparent species differences may reflect the methods used to assess it, rather than a capacity confined to great apes, humans, and a few other animals. The study further suggests adopting a species-specific, rather than anthropocentric, approach to research on animal consciousness.[86][165] This study has been confirmed by another study.[166]
Research with captivegrey parrots, especiallyIrene Pepperberg's work with an individual namedAlex, has demonstrated they possess the ability to associate simple human words with meanings, and to intelligently apply the abstract concepts of shape, colour, number, zero-sense, etc. According to Pepperberg and other scientists, they perform many cognitive tasks at the level of dolphins, chimpanzees, and even humantoddlers.[167] Another notable African grey isN'kisi, which in 2004 was said to have a vocabulary of over 950 words which she used in creative ways.[168] For example, whenJane Goodall visited N'kisi in his New York home, he greeted her with "Got a chimp?" because he had seen pictures of her with chimpanzees in Africa.[169]
In 2011, research led by Dalila Bovet ofParis West University Nanterre La Défense, demonstrated grey parrots were able to coordinate and collaborate with each other to an extent. They were able to solve problems such as two birds having to pull strings at the same time to obtain food. In another example, one bird stood on a perch to release a food-laden tray, while the other pulled the tray out from the test apparatus. Both would then feed. The birds were observed waiting for their partners to perform the necessary actions so their behaviour could be synchronized. The parrots appeared to express individual preferences as to which of the other test birds they would work with.[170]
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It was thought that self-recognition was restricted to mammals with large brains and highly evolved social cognition, but absent from animals without aneocortex. However, in 2008, an investigation of self-recognition incorvids was conducted to determine the ability of self-recognition in the magpie. Mammals and birds inherited the same brain components from their last commonancestor nearly 300 million years ago, and have since independently evolved and formed significantly different brain types. The results of the mirror test showed that althoughmagpies do not have a neocortex, they are capable of understanding that a mirror image belongs to their own body. The findings show that magpies respond to the mirror test in a manner similar to that of apes, dolphins, killer whales, pigs and elephants.[69]
A 2020 study found thatcarrion crows show a neuronal response that correlates with theirperception of a stimulus, which they argue to be an empirical marker of (avian) sensory consciousness – the conscious perception of sensory input – in the crows which do not have acerebral cortex. The study thereby substantiates the theory that conscious perception does not require a cerebral cortex and that the basic foundations for it – and possibly for human-type consciousness – may have evolved before the last common ancestor >320 Mya or independently in birds.[171][111] A related study showed that the birds'pallium's neuroarchitecture is reminiscent of the mammalian cortex.[172]
A 2025 review applied a five-dimensional framework of consciousness to corvids, examining sensory, evaluative, temporal, and self-related aspects of their experience. Drawing on behavioural and neurological evidence, the authors argue that corvids exhibit sophisticated cognitive capacities across all dimensions, including high perceptual acuity, emotional evaluation, episodic-like memory, future planning, and possible forms of self-awareness and theory of mind. While not claiming definitive proof of consciousness, the review supports the growing consensus that corvids are plausible sentient beings and proposes they serve as a model group for the comparative study of non-mammalian consciousness.[173]
![[icon]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aWiki_letter_w_cropped.svg) | This sectionneeds expansion with: other invertebrates, such as insects. You can help byadding to it.(February 2025) |
Octopuses are highly intelligent, possibly more so than any other order ofinvertebrates. The level of their intelligence and learning capability are debated,[174][175][176][177] but maze andproblem-solving studies show they have bothshort- andlong-term memory. Octopus have a highly complexnervous system, only part of which is localized in theirbrain. Two-thirds of an octopus'sneurons are found in the nerve cords of their arms. Octopus arms show a variety of complexreflex actions that persist even when they have no input from the brain.[178] Unlike vertebrates, the complex motor skills of octopuses are not organized in their brain using an internalsomatotopic map of their body, instead using a non-somatotopic system unique to large-brained invertebrates.[179] Some octopuses, such as themimic octopus, move their arms in ways that emulate the shape and movements of othersea creatures.[citation needed]
In laboratory studies, octopuses can easily be trained to distinguish between different shapes and patterns. They reportedly useobservational learning,[180] although the validity of these findings is contested.[174][175] Octopuses have also been observed toplay: repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them.[181] Octopuses often escape from their aquarium and sometimes enter others. They have boardedfishing boats and opened holds to eat crabs.[176] At least four specimens of the veined octopus (Amphioctopus marginatus) have been witnessed retrieving discardedcoconut shells, manipulating them, and then reassembling them to use as shelter.[182][183]
Shamanistic and other traditional cultures and folk tales speak of animal spirits and the consciousness of animals.[184][185] In India,Jains consider all thejivas (living organisms, including plants, animals and insects) to be conscious.[citation needed]
Some contributors to relevant research on animal consciousness include:
...a rejection of any dualism between mind and body, and a consequent insistence on the argument that the body is never simply a physical object but always an embodiment of consciousness.
{{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link){{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link){{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link){{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link){{cite book}}: CS1 maint: publisher location (link)The important thing to remember is that dogs are not as visually oriented as humans
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