From Wikipedia, the free encyclopedia
Animal consciousness, or
animal awareness, is the
quality 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 to
experience or to
feel,
wakefulness, having a sense of
selfhood, 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 the
problem of other minds
in an especially severe form because animals, lacking the ability to
use human language, cannot tell us about their experiences.
[6]
Also, it is difficult to reason objectively about the question, because
a denial that an animal is conscious is often taken to imply that it
does not feel, its life has no value, and that harming it is not morally
wrong. The 17th-century French philosopher
René Descartes, for example, has sometimes been blamed for mistreatment of animals because he argued that only humans are conscious.
[7]
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 philosopher
Thomas Nagel spelled out this point of view in an influential essay titled
What 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 like
for
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 its world in the way it does itself.
[8] Other thinkers, such as the cognitive scientist
Douglas Hofstadter, dismiss this argument as incoherent.
[9]
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—
Donald Griffin's 2001 book
Animal Minds reviews a substantial portion of the evidence.
[10]
Animal consciousness has been actively researched for over one hundred years.
[11] In 1927 the American functional psychologist
Harvey 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 (especially psychophysics) 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 the
Cambridge 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]
Philosophical background
René Descartes argued that only humans are conscious, and not other animals
The
mind–body problem in philosophy examines the relationship between
mind and matter, and in particular the relationship between
consciousness and the brain. A variety of approaches have been proposed. Most are either
dualist or
monist.
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,
[14][15] and was famously addressed by
René Descartes in the 17th century, resulting in
Cartesian dualism. Descartes believed that humans only, and not other animals have this non-physical mind.
The rejection of the mind–body dichotomy is found in French
Structuralism, and is a position that generally characterized post-war
French philosophy.
[16]
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.
[17] These approaches have been particularly influential in the sciences, particularly in the fields of
sociobiology,
computer science,
evolutionary psychology, and the
neurosciences.
[18][19][20][21]
Epiphenomenalism
Epiphenomenalism is the theory in
philosophy 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.
[22]
The history of epiphenomenalism goes back to the post-Cartesian attempt to solve the riddle of
Cartesian dualism, i.e., of how mind and body could interact.
La Mettrie,
Leibniz and
Spinoza
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 by
Cabanis (1802), and was further explicated by
Hodgson (1870) and
Huxley (1874).
[23][24]
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
1900s
scientific behaviorists such as
Ivan Pavlov,
John B. Watson, and
B. 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 of
eliminativism or mental
fictionalism,
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 the
cognitive revolution. Participants in that revolution, such as
Jerry Fodor,
reject epiphenomenalism and insist upon the efficacy of the mind. Fodor
even speaks of "epiphobia"—fear that one is becoming an
epiphenomenalist.
Thomas Henry Huxley defends in an essay titled
On 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".
[25] To this
William James objects in his essay
Are 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 of
natural 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.
[26][27] Karl Popper develops in the book
The Self and Its Brain a similar evolutionary argument.
[28]
Animal ethics
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.
[29]
In his interactions with scientists and other veterinarians, Rollin was
regularly asked to prove animals are conscious and provide
scientifically acceptable grounds for claiming they feel pain.
[29]
Academic reviews of the topic are equivocal, noting that the argument
that animals have at least simple conscious thoughts and feelings has
strong support,
[30] but some critics continue to question how reliably animal mental states can be determined.
[31][32] A refereed journal
Animal Sentience[33] launched in 2015 by the Institute of Science and Policy of
The Humane Society of the United States is devoted to research on this and related topics.
Defining consciousness
About forty meanings attributed to the term
consciousness can be identified and categorized based on
functions and
experiences. The prospects for reaching any single, agreed-upon, theory-independent definition of consciousness appear remote.
[34]
“
”
Consciousness is an elusive concept that presents many difficulties when attempts are made to define it.
[35][36]
Its study has progressively become an interdisciplinary challenge for
numerous researchers, including ethologists, neurologists, cognitive
neuroscientists, philosophers, psychologists and psychiatrists.
[37][38]
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".
[39] In 2004, eight neuroscientists felt it was still too soon for a definition. They wrote an apology in "Human Brain Function":
[40]
-
- "We have no idea how consciousness emerges from the physical
activity of the brain and we do not know whether consciousness can
emerge from non-biological systems, such as computers... At this point
the reader will expect to find a careful and precise definition of
consciousness. You will be disappointed. Consciousness has not yet
become a scientific term that can be defined in this way. Currently we
all use the term consciousness in many different and often
ambiguous ways. Precise definitions of different aspects of
consciousness will emerge ... but to make precise definitions at this
stage is premature."
Consciousness is sometimes defined as the quality or state of being aware of an external object or something within oneself.
[3][41] It has been defined somewhat vaguely as:
subjectivity,
awareness,
sentience, the ability to
experience or to
feel, wakefulness, having a sense of
selfhood, 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 and Susan Schneider wrote in
The 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."
[42]
Related terms, also often used in vague or ambiguous ways, are:
- Awareness: the state or ability to perceive, to feel, or to be conscious of events, objects, or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of something. In biological psychology, awareness is defined as a human's or an animal's perception and cognitive reaction to a condition or event.
- Self-awareness: the capacity for introspection and the ability to reconcile oneself as an individual separate from the environment and other individuals.
- Self-consciousness: an acute sense of self-awareness. It is a preoccupation with oneself, as opposed to the philosophical state of self-awareness,
which is the awareness that one exists as an individual being; although
some writers use both terms interchangeably or synonymously.[43]
- Sentience: the ability to be aware (feel, perceive, or be conscious)
of one's surroundings or to have subjective experiences. Sentience is a
minimalistic way of defining consciousness, which is otherwise commonly
used to collectively describe sentience plus other characteristics of
the mind.
- Sapience: often defined as wisdom, or the ability of an organism or entity to act with appropriate judgment, a mental faculty which is a component of intelligence or alternatively may be considered an additional faculty, apart from intelligence, with its own properties.
- Qualia: individual instances of subjective, conscious experience.
Sentience (the ability to feel, perceive, or to experience
subjectivity) is not the same as self-awareness (being aware of oneself
as an individual). The
mirror 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.
[44][45] It remains debatable whether recognition of one's mirror image can be properly construed to imply full self-awareness,
[46] particularly given that robots are being constructed which appear to pass the test.
[47][48]
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...".
[49] However, this view has been criticized because consciousness has yet to be shown to be a process,
[50] and the so-called
"hard problem" of relating consciousness directly to brain activity remains elusive.
[51]
Scientific approaches
Since
Descartes's proposal of
dualism, it became a general consensus that the mind had become a matter of
philosophy
and that science was not able to penetrate the issue of consciousness -
that consciousness was outside of space and time. However, over the
last 20 years, many scholars have begun to move toward a science of
consciousness.
Antonio Damasio and
Gerald 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,
[52][53]
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 from neural
computation.
[54][55] In his research on this problem, Edelman has developed a theory of consciousness, in which he has coined the terms
primary consciousness and
secondary consciousness.
[56][57]
Eugene Linden, author of
The 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.
[58]
Philosopher
Daniel Dennett counters that:
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.[59]
Consciousness in mammals (including humans) is an aspect of the mind generally thought to comprise qualities such as
subjectivity,
sentience, and the ability to
perceive the relationship between
oneself and one's
environment. It is a subject of much research in
philosophy of mind,
psychology,
neuroscience, and
cognitive science. Some philosophers divide consciousness into
phenomenal
consciousness, which is subjective experience itself, and access
consciousness, which refers to the global availability of information to
processing systems in the brain.
[60] Phenomenal consciousness has many different experienced qualities, often referred to as
qualia. Phenomenal consciousness is usually consciousness
of something or
about something, a property known as
intentionality in philosophy of mind.
[60]
In humans, there are three common methods of studying consciousness,
i.e. verbal report, behavioural demonstrations, and neural correlation
with conscious activity. Unfortunately these can only be generalized to
non-human taxa with varying degrees of difficulty.
[61]
Mirror test
Elephants can recognize themselves in a mirror.
[62]
The sense in which animals (or human infants) can be said to have
consciousness or a
self-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 the
mirror test devised by
Gordon G. Gallup,
in which the skin of an animal (or human infant) is marked, while it is
asleep or sedated, with a mark that cannot be seen directly but is
visible in a mirror. The animal is then allowed to see its reflection in
a mirror; if the animal spontaneously directs grooming behaviour
towards the mark, that is taken as an indication that it is aware of
itself.
[63][64]
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:
Apes
Other land mammals
Cetaceans
Birds
Until recently it was thought that self-recognition was absent from animals without a
neocortex,
and was restricted to mammals with large brains and well developed
social cognition. However, in 2008 a study of self-recognition in
corvids reported significant results for magpies. Mammals and birds inherited the same brain components from their last common
ancestor
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-less
magpies
are capable of understanding that a mirror image belongs to their own
body. The findings show that magpies respond in the mirror and mark test
in a manner similar to apes, dolphins and elephants. This is a
remarkable capability that, although not fully concrete in its
determination of self-recognition, is at least a prerequisite of
self-recognition. This is not only of interest regarding the convergent
evolution of social intelligence; it is also valuable for an
understanding of the general principles that govern cognitive evolution
and their underlying neural mechanisms. The magpies were chosen to study
based on their empathy/lifestyle, a possible precursor for their
ability of self-awareness.
[64]
However even in the chimpanzee, the species most studied and with the
most convincing findings, clear-cut evidence of self-recognition is not
obtained in all individuals tested. Occurrence is about 75% in young
adults and considerably less in young and old individuals.
[72]
For monkeys, non-primate mammals, and in a number of bird species,
exploration of the mirror and social displays were observed. However,
hints at mirror-induced self-directed behavior have been obtained.
[73]
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 the
olfactory sense in dogs.
[74][75][76] A study in 2015 showed that the
“sniff test of self-recognition (STSR)” provides evidence of
self-awareness in dogs.
[76]
Language
Another approach to determine whether a non-human animal is conscious derives from passive speech research with a macaw (see
Arielle).
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's
crib speech by Weir (1962) and in investigations of early speech in children by Greenfield and others (1976).
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.
[77]
Pain or suffering
Further arguments revolve around the ability of animals to feel
pain or
suffering.
Suffering implies consciousness. If animals can be shown to suffer in a
way similar or identical to humans, many of the arguments against human
suffering could then, presumably, be extended to animals. Others have
argued that pain can be demonstrated by adverse reactions to negative
stimuli that are non-purposeful or even maladaptive.
[78] One such reaction is
transmarginal inhibition, a phenomenon observed in humans and some animals akin to
mental breakdown.
Carl Sagan, the American cosmologist, points to reasons why humans have had a tendency to deny animals can suffer:
Humans – who enslave, castrate, experiment on, and fillet other
animals – have had an understandable penchant for pretending animals do
not feel pain. A sharp distinction between humans and 'animals' is
essential if we are to bend them to our will, make them work for us,
wear them, eat them – without any disquieting tinges of guilt or regret.
It is unseemly of us, who often behave so unfeelingly toward other
animals, to contend that only humans can suffer. The behavior of other
animals renders such pretensions specious. They are just too much like
us.[79]
John Webster, a professor of animal husbandry at Bristol, argues:
People have assumed that intelligence is linked to the ability to
suffer and that because animals have smaller brains they suffer less
than humans. That is a pathetic piece of logic, sentient animals have
the capacity to experience pleasure and are motivated to seek it, you
only have to watch how cows and lambs both seek and enjoy pleasure when
they lie with their heads raised to the sun on a perfect English
summer's day. Just like humans.[80]
However, there is no agreement where the line between organisms that can feel pain and those that cannot should be drawn.
Justin Leiber, a philosophy professor at
Oxford University writes that:
Montaigne
is ecumenical in this respect, claiming consciousness for spiders and
ants, and even writing of our duties to trees and plants. Singer and Clarke
agree in denying consciousness to sponges. Singer locates the
distinction somewhere between the shrimp and the oyster. He, with rather
considerable convenience for one who is thundering hard accusations at
others, slides by the case of insects and spiders and bacteria, they
pace Montaigne, apparently and rather conveniently do not feel pain. The
intrepid Midgley, on the other hand, seems willing to speculate about the subjective experience of tapeworms ...Nagel ... appears to draw the line at flounders and wasps, though more recently he speaks of the inner life of cockroaches.[81]
There are also some who reject the argument entirely, arguing that
although suffering animals feel anguish, a suffering plant also
struggles to stay alive (albeit in a less visible way). In fact, no
living organism 'wants' to die for another organism's sustenance. In an
article written for the
New York Times, Carol Kaesuk Yoon argues that:
When a plant is wounded, its body immediately kicks into protection
mode. It releases a bouquet of volatile chemicals, which in some cases
have been shown to induce neighboring plants to pre-emptively step up
their own chemical defenses and in other cases to lure in predators of
the beasts that may be causing the damage to the plants. Inside the
plant, repair systems are engaged and defenses are mounted, the
molecular details of which scientists are still working out, but which
involve signaling molecules coursing through the body to rally the
cellular troops, even the enlisting of the genome itself, which begins
churning out defense-related proteins ... If you think about it, though,
why would we expect any organism to lie down and die for our dinner?
Organisms have evolved to do everything in their power to avoid being
extinguished. How long would any lineage be likely to last if its
members effectively didn't care if you killed them? [82]
Cognitive bias and emotion
Is the glass half empty or half full?
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.
[83] Individuals create their own "subjective social reality" from their perception of the input.
[84] 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.
[85][86][87]
The neuroscientist
Joseph LeDoux advocates avoiding terms derived from human subjective experience when discussing brain functions in animals.
[88]
For example, the common practice of calling brain 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.
[89]
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.
[90][91]
Neuroscience
Neuroscience is the scientific study of the
nervous system.
[92] It is a highly active
interdisciplinary science that collaborates with many other fields. The scope of neuroscience has broadened recently to include
molecular,
cellular,
developmental,
structural,
functional,
evolutionary,
computational, and
medical aspects of the nervous system. Theoretical studies of
neural networks are being complemented with techniques for
imaging sensory and motor tasks in the
brain.
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.
[93]
They found that subjects who were not neuroscience experts "judged that
explanations with logically irrelevant neuroscience information were
more satisfying than explanations without.
[93]
Neural correlates
The
neural correlates of consciousness constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious
percept.
[94] Neuroscientists use empirical approaches to discover
neural correlates of subjective phenomena.
[95] The set should be
minimal
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.
Visual sense and representation was reviewed in 1998 by
Francis Crick and
Christof Koch. They concluded
sensory neuroscience
can be used as a bottom-up approach to studying consciousness, and
suggested experiments to test various hypotheses in this research
stream.
[96]
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.
[97]
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.
[98]
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.
Neocortex
The
neocortex is a part of the brain of mammals. It consists of the
grey matter, or neuronal cell bodies and
unmyelinated fibers, surrounding the deeper
white matter (
myelinated axons) in the
cerebrum. The neocortex is smooth in
rodents and other small mammals, whereas in
primates
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 into
frontal,
parietal,
occipital, and
temporal lobes, which perform different functions. For example, the occipital lobe contains the
primary visual cortex, and the temporal lobe contains the
primary auditory cortex. Further subdivisions or areas of neocortex are responsible for more
specific cognitive processes. The neocortex is the newest part of the
cerebral cortex to evolve (hence the prefix "neo"); the other parts of the cerebral cortex are the
paleocortex and
archicortex, collectively known as the
allocortex. In humans, 90% of the cerebral cortex is neocortex.
Researchers have argued that consciousness arises in the neocortex,
and therefore 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."
[99] Recently that view has been challenged, and many researchers now believe that animal consciousness can arise from
homologous subcortical brain networks.
[1]
Attention
Attention is the
cognitive 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.
[100]
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.
[101]
Most experiments show that one
neural 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 the
EEG. Many animals, including humans, produce
gamma waves (40–60 Hz) when focusing attention on a particular object or activity.
[102]
Extended consciousness
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 by
Antonio Damasio and is used in
biological psychology. Extended consciousness is said to arise in structures in the
human brain described as
image spaces and
dispositional spaces. Image spaces imply areas where
sensory impressions of all types are processed, including the focused awareness of the
core 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.
[103][104]
Metacognition
Metacognition is defined as "
cognition about cognition", or "knowing about knowing."
[105]
It can take many forms; it includes knowledge about when and how to use
particular strategies for learning or for problem solving.
[105] It has been suggested that metacognition in some animals provides evidence for cognitive self-awareness.
[106] There are generally two components of metacognition: knowledge about cognition, and regulation of cognition.
[107] Writings on metacognition can be traced back at least as far as
De Anima and the
Parva Naturalia of the Greek philosopher
Aristotle.
[108] Metacognologists believe that the ability to consciously think about thinking is unique to
sapient species and indeed is one of the definitions of sapience.
[citation needed] There is evidence that
rhesus monkeys and apes can make accurate judgments about the strengths of their memories of fact and monitor their own uncertainty,
[109] while attempts to demonstrate metacognition in birds have been inconclusive.
[110] A 2007 study provided some evidence for metacognition in
rats,
[111][112][113] but further analysis suggested that they may have been following simple
operant conditioning principles,
[114] or a behavioral economic model.
[115]
Mirror neurons
Mirror neurons are
neurons that
fire both when an animal acts and when the animal observes the same action performed by another.
[116][117][118]
Thus, the neuron "mirrors" the behavior of the other, as though the
observer were itself acting. Such neurons have been directly observed in
primate and other species including
birds.
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 the
common coding theory).
[118]
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 to
theory of mind skills,
[119][120] while others relate mirror neurons to
language abilities.
[121]
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 as
empathy.
[118][122] Vilayanur S. Ramachandran has speculated that mirror neurons may provide the neurological basis of self-awareness.
[123][124]
Evolutionary psychology
Consciousness is likely an evolved
adaptation since it meets
George Williams' criteria of species universality, complexity,
[125] and functionality, and it is a
trait that apparently increases
fitness.
[126] Opinions are divided as to where in biological
evolution
consciousness emerged and about whether or not consciousness has
survival value. It has been argued that consciousness emerged (i)
exclusively with the first humans, (ii) exclusively with the first
mammals, (iii) independently in mammals and birds, or (iv) with the
first reptiles.
[127] Donald Griffin suggests in his book
Animal Minds a gradual evolution of consciousness.
[10] Each of these scenarios raises the question of the possible survival value of consciousness.
In his paper "Evolution of consciousness,"
John Eccles argues that special anatomical and physical adaptations of the mammalian
cerebral cortex gave rise to consciousness.
[128]
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 social
and natural environments by providing an energy-saving "neutral" gear in an otherwise energy-expensive motor output machine.
[129]
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 by
Bernard J. Baars.
[130] Richard Dawkins suggested that humans evolved consciousness in order to make themselves the subjects of thought.
[131]
Daniel Povinelli suggests that large, tree-climbing apes evolved
consciousness to take into account one's own mass when moving safely
among tree branches.
[131] Consistent with this hypothesis,
Gordon Gallup found that chimps and orangutans, but not little monkeys or terrestrial gorillas, demonstrated
self-awareness in mirror tests.
[131]
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.
[131]
Neural Darwinism
Neural Darwinism is a large scale theory of brain function initially proposed in 1978 by the American biologist
Gerald Edelman.
[132] Edelman distinguishes between what he calls primary and secondary consciousness:
- Primary consciousness: is the ability, found in humans and some animals, to integrate observed events with memory to create an awareness
of the present and immediate past of the world around them. This form
of consciousness is also sometimes called "sensory consciousness". Put
another way, primary consciousness is the presence of various subjective sensory contents of consciousness such as sensations, perceptions,
and mental images. For example, primary consciousness includes a
person's experience of the blueness of the ocean, a bird's song, and the
feeling of pain. Thus, primary consciousness refers to being mentally
aware of things in the world in the present without any sense of past
and future; it is composed of mental images bound to a time around the
measurable present.[133]
- Secondary consciousness:
is an individual's accessibility to their history and plans. The
concept is also loosely and commonly associated with having awareness of
one's own consciousness. The ability allows its possessors to go beyond the limits of the remembered present of primary consciousness.[56]
Primary consciousness can be defined as simple awareness that includes
perception and
emotion.
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 and
metacognition.
[56][134]
Edelman's theory focuses on two
nervous system organizations: the
brainstem and
limbic systems on one side and the
thalamus and
cerebral 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 learn
adaptive behaviors.
[133]
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 from
sensors and
receptors,
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 the
thalamic,
hippocampal,
orbitofrontal,
insula, and
midbrain sites are the key to consciousness of thirst.
[135]
These scientists also point out that the cortex might not be as
important to primary consciousness as some neuroscientists have
believed.
[135]
Evidence of this lies in the fact that studies show that systematically
disabling parts of the cortex in animals does not remove consciousness.
Another study found that children born without a cortex are conscious. Instead of cortical mechanisms, these scientists emphasize brainstem
mechanisms as essential to consciousness.
[135]
Still, these scientists concede that higher order consciousness does
involve the cortex and complex communication between different areas of
the brain.
While animals with
primary 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 with
semantic capabilities, such as the four
great apes. It is present in its richest form in the human species, which is unique in possessing complex
language made up of
syntax
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 of
reptiles into mammals and then into
birds, the
embryological development of large numbers of new reciprocal connections allowed rich
re-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.
[56]
The ability of an animal to relate a present complex scene to its 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 conceptual
memory systems. This development enabled the emergence of secondary consciousness.
[136][137]
Ursula Voss of the
Universität Bonn believes that the theory of
protoconsciousness[138]
may serve as adequate explanation for self-recognition found in birds,
as they would develop secondary consciousness during REM sleep.
[139]
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.
[140]
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, the
mirror test (see above) has been used as an indicator of
self-awareness.
Cambridge Declaration on Consciousness
Cambridge Declaration on Consciousness
The absence of a
neocortex
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 exhibit
intentional behaviors. Consequently, the weight of evidence indicates 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 neurological substrates.
[141]
“
”
In 2012, a group of neuroscientists attending a conference on "Consciousness in Human and non-Human Animals" at the
University of Cambridge in the UK, signed
The Cambridge Declaration on Consciousness (see box on the right).
[1][142]
In the accompanying text they "unequivocally" asserted:
[1]
- "The field of Consciousness research is rapidly evolving. Abundant
new techniques and strategies for human and non-human animal research
have been developed. Consequently, more data is becoming readily
available, and this calls for a periodic reevaluation of previously held
preconceptions in this field. Studies of non-human animals have shown
that homologous
brain circuits correlated with conscious experience and perception can
be selectively facilitated and disrupted to assess whether they are in
fact necessary for those experiences. Moreover, in humans, new
non-invasive techniques are readily available to survey the correlates of consciousness."[1]
- "The neural substrates of emotions do not appear to be confined to cortical structures. In fact, subcortical
neural networks aroused during affective states in humans are also
critically important for generating emotional behaviors in animals.
Artificial arousal of the same brain regions generates corresponding
behavior and feeling states in both humans and non-human animals.
Wherever in the brain one evokes instinctual emotional behaviors in
non-human animals, many of the ensuing behaviors are consistent with
experienced feeling states, including those internal states that are
rewarding and punishing. Deep brain stimulation of these systems in
humans can also generate similar affective states. Systems associated
with affect are concentrated in subcortical regions where neural homologies abound. Young human and non-human animals without neocortices retain these brain-mind functions. Furthermore, neural circuits
supporting behavioral/electrophysiological states of attentiveness,
sleep and decision making appear to have arisen in evolution as early as
the invertebrate radiation, being evident in insects and cephalopod
mollusks (e.g., octopus)."[1]
- "Birds appear to offer, in their behavior, neurophysiology, and neuroanatomy a striking case of parallel evolution of consciousness. Evidence of near human-like levels of consciousness has been most dramatically observed in grey parrots.
Mammalian and avian emotional networks and cognitive microcircuitries
appear to be far more homologous than previously thought. Moreover,
certain species of birds have been found to exhibit neural sleep patterns similar to those of mammals, including REM sleep and, as was demonstrated in zebra finches, neurophysiological patterns previously thought to require a mammalian neocortex. Magpies in particular have been shown to exhibit striking similarities to humans, great apes, dolphins, and elephants in studies of mirror self-recognition."[1]
- "In humans, the effect of certain hallucinogens appears to be associated with a disruption in cortical feedforward
and feedback processing. Pharmacological interventions in non-human
animals with compounds known to affect conscious behavior in humans can
lead to similar perturbations in behavior in non-human animals. In
humans, there is evidence to suggest that awareness is correlated with
cortical activity, which does not exclude possible contributions by
subcortical or early cortical processing, as in visual awareness.
Evidence that human and non-human animal emotional feelings arise from
homologous subcortical brain networks provide compelling evidence for
evolutionarily shared primal affective qualia."[1]
Examples
A common image is the
scala naturae, the ladder of nature on which animals of different species occupy successively higher rungs, with humans typically at the top.
[143]
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.
[144][145]
Mammals
Dogs
Dogs were previously listed as non-self-aware animals. Because, traditionally, self-consciousness was evaluated via the
mirror test,
scientists can confirm that an animal species possess some sense of
self. But dogs, as many other animals, are not visually oriented. In
2015 a study showed that the “
sniff test of self-recognition (STSR)”
provides significant evidences of self-awareness in dogs, and can play a
crucial role in showing that this capacity is not a specific feature of
only great apes, humans and a few other animals, but it depends on the
way in which researchers try to verify it.
[76]
According to the biologist Roberto Cazzolla Gatti, "the innovative
approach to test the self-awareness with a smell test highlights the
need to shift the paradigm of the anthropocentric idea of consciousness
to a species-specific perspective".
[146]
Birds
Grey Parrots
Research with captive
grey parrots, especially
Irene Pepperberg's work with an individual named
Alex,
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 human
toddlers.
[147] Another notable African grey is
N'kisi, which in 2004 was said to have a vocabulary of over 950 words which she used in creative ways.
[148] For example, when
Jane 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.
[149]
In 2011, research led by Dalila Bovet of
Paris 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.
[150]
Corvids
It was recently thought that self-recognition was restricted to
mammals with large brains and highly evolved social cognition, but
absent from animals without a
neocortex. However, in 2008, an investigation of self-recognition in
corvids
was conducted revealing the ability of self-recognition in the magpie.
Mammals and birds inherited the same brain components from their last
common
ancestor
nearly 300 million years ago, and have since independently evolved and
formed significantly different brain types. The results of the mirror
test showed that although
magpies
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 in the mirror test in a manner similar to apes, dolphins, killer
whales, pigs and elephants. This is a remarkable capability that,
although not fully concrete in its determination of self-recognition, is
at least a prerequisite of self-recognition. This is not only of
interest regarding the convergent evolution of social intelligence, it
is also valuable for an understanding of the general principles that
govern cognitive evolution and their underlying neural mechanisms. The
magpies were chosen to study based on their empathy/lifestyle, a
possible precursor for their ability of self-awareness.
[64]
Invertebrates
Octopus travelling with shells collected for protection
Octopuses are highly intelligent, possibly more so than any other order of
invertebrates. The level of their intelligence and learning capability are debated,
[151][152][153][154] but maze and
problem-solving studies show they have both
short- and
long-term memory. Octopus have a highly complex
nervous system, only part of which is localized in their
brain. Two-thirds of an octopus'
neurons are found in the nerve cords of their arms. Octopus arms show a variety of complex
reflex actions that persist even when they have no input from the brain.
[155] Unlike vertebrates, the complex motor skills of octopuses are not organized in their brain using an internal
somatotopic map of their body, instead using a non-somatotopic system unique to large-brained invertebrates.
[156] Some octopuses, such as the
mimic octopus, move their arms in ways that emulate the shape and movements of other
sea creatures.
In laboratory studies, octopuses can easily be trained to distinguish
between different shapes and patterns. They reportedly use
observational learning,
[157] although the validity of these findings is contested.
[151][152] Octopuses have also been observed to
play: repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them.
[158] Octopuses often escape from their aquarium and sometimes enter others. They have boarded
fishing boats and opened holds to eat crabs.
[153] At least four specimens of the veined octopus (
Amphioctopus marginatus) have been witnessed retrieving discarded
coconut shells, manipulating them, and then reassembling them to use as shelter.
[159][160]
The left optic nerve and the optic tracts.
Coronal section of lateral and 3rd ventricles.
Dissection showing the ventricles of the brain.
Section of brain showing upper surface of temporal lobe.
Horizontal section of right cerebral hemisphere.
Mesal aspect of a brain sectioned in the median sagittal plane.
Schematic representation of the chief ganglionic categories (I to V).
Deep dissection of brain-stem. Lateral view.
Deep dissection of brain-stem. Ventral view.
Coronal section of brain immediately in front of pons.
Coronal section of brain through intermediate mass of third ventricle.
Human brain frontal (coronal) section
Thalamus
Ventricles of brain and basal ganglia. Superior view. Horizontal section. Deep dissection
Ventricles of brain and basal ganglia. Superior view. Horizontal section. Deep dissection
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