Intelligence has been defined in many ways: the capacity for
abstraction
Abstraction is a process where general rules and concepts are derived from the use and classifying of specific examples, literal (reality, real or Abstract and concrete, concrete) signifiers, first principles, or other methods.
"An abstraction" ...
,
logic
Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
,
understanding,
self-awareness,
learning
Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, Attitude (psychology), attitudes, and preferences. The ability to learn is possessed by humans, non-human animals, and ...
,
emotional knowledge,
reasoning,
planning,
creativity
Creativity is the ability to form novel and valuable Idea, ideas or works using one's imagination. Products of creativity may be intangible (e.g. an idea, scientific theory, Literature, literary work, musical composition, or joke), or a physica ...
,
critical thinking
Critical thinking is the process of analyzing available facts, evidence, observations, and arguments to make sound conclusions or informed choices. It involves recognizing underlying assumptions, providing justifications for ideas and actions, ...
, and
problem-solving. It can be described as the ability to perceive or infer
information and to retain it as
knowledge
Knowledge is an Declarative knowledge, awareness of facts, a Knowledge by acquaintance, familiarity with individuals and situations, or a Procedural knowledge, practical skill. Knowledge of facts, also called propositional knowledge, is oft ...
to be applied to adaptive behaviors within an environment or context.
The term rose to prominence during the early 1900s. Most
psychologist
A psychologist is a professional who practices psychology and studies mental states, perceptual, cognitive, emotional, and social processes and behavior. Their work often involves the experimentation, observation, and explanation, interpretatio ...
s believe that intelligence can be divided into various domains or competencies.
Intelligence has been long-studied in
human
Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
s, and across numerous disciplines. It has also been observed in the
cognition of non-human animals.
Some researchers have suggested that
plants
Plants are the eukaryotes that form the kingdom Plantae; they are predominantly photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars f ...
exhibit forms of intelligence, though this remains controversial.
Etymology
The word ''
intelligence'' derives from the Latin
noun
In grammar, a noun is a word that represents a concrete or abstract thing, like living creatures, places, actions, qualities, states of existence, and ideas. A noun may serve as an Object (grammar), object or Subject (grammar), subject within a p ...
s ''
intelligentia'' or ''
intellēctus'', which in turn stem from the verb ''
intelligere'', to comprehend or perceive. In the
Middle Ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, the word ''intellectus'' became the scholarly technical term for understanding and a translation for the Greek philosophical term ''nous''. This term, however, was strongly linked to the
metaphysical
Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of h ...
and
cosmological theories of
teleological scholasticism, including theories of the immortality of the soul, and the concept of the
active intellect (also known as the active intelligence). This approach to the study of nature was strongly rejected by
early modern philosophers such as
Francis Bacon,
Thomas Hobbes
Thomas Hobbes ( ; 5 April 1588 – 4 December 1679) was an English philosopher, best known for his 1651 book ''Leviathan (Hobbes book), Leviathan'', in which he expounds an influential formulation of social contract theory. He is considered t ...
,
John Locke, and
David Hume, all of whom preferred "understanding" (in place of "''intellectus''" or "intelligence") in their English philosophical works. Hobbes for example, in his Latin ''
De Corpore'', used "''intellectus intelligit''", translated in the English version as "the understanding understandeth", as a typical example of a logical
absurdity. "Intelligence" has therefore become less common in English language philosophy, but it has later been taken up (with the scholastic theories that it now implies) in more contemporary
psychology
Psychology is the scientific study of mind and behavior. Its subject matter includes the behavior of humans and nonhumans, both consciousness, conscious and Unconscious mind, unconscious phenomena, and mental processes such as thoughts, feel ...
.
Definitions
There is controversy over how to define intelligence. Scholars describe its constituent abilities in various ways, and differ in the degree to which they conceive of intelligence as quantifiable.
A consensus report called ''
Intelligence: Knowns and Unknowns'', published in 1995 by the Board of Scientific Affairs of the
American Psychological Association, states:
Psychologists and
learning
Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, Attitude (psychology), attitudes, and preferences. The ability to learn is possessed by humans, non-human animals, and ...
researchers also have suggested definitions of intelligence such as the following:
Human
Human intelligence is the intellectual power of humans, which is marked by complex
cognitive feats and high levels of
motivation
Motivation is an mental state, internal state that propels individuals to engage in goal-directed behavior. It is often understood as a force that explains why people or animals initiate, continue, or terminate a certain behavior at a particul ...
and
self-awareness. Intelligence enables humans to remember descriptions of things and use those descriptions in future behaviors. It gives humans the cognitive abilities to
learn,
form concepts,
understand, and
reason, including the capacities to
recognize patterns, innovate,
plan,
solve problems, and employ
language
Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...
to
communicate. These cognitive abilities can be organized into frameworks like
fluid vs. crystallized and the Unified Cattell-Horn-Carroll model,
which contains abilities like fluid reasoning, perceptual speed, verbal abilities, and others.
Intelligence is different from
learning
Learning is the process of acquiring new understanding, knowledge, behaviors, skills, value (personal and cultural), values, Attitude (psychology), attitudes, and preferences. The ability to learn is possessed by humans, non-human animals, and ...
. Learning refers to the act of retaining facts and information or abilities and being able to recall them for future use. Intelligence, on the other hand, is the cognitive ability of someone to perform these and other processes.
Intelligence quotient (IQ)
There have been various attempts to quantify intelligence via
psychometric testing. Prominent among these are the various
Intelligence Quotient
An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. Originally, IQ was a score obtained by dividing a person's mental age score, obtained by administering ...
(IQ) tests, which were first developed in the early 20th century to screen children for
intellectual disability.
Over time, IQ tests became more pervasive, being used to screen immigrants, military recruits, and job applicants. As the tests became more popular, belief that IQ tests measure a fundamental and unchanging attribute that all humans possess became widespread.
An influential theory that promoted the idea that IQ measures a fundamental quality possessed by every person is the theory of
General Intelligence, or ''g'' factor. The ''g'' factor is a construct that summarizes the
correlations observed between an individual's scores on a range of cognitive tests.
Today, most psychologists agree that IQ measures at least some aspects of human intelligence, particularly the ability to thrive in an academic context.
However, many psychologists question the
validity of IQ tests as a measure of intelligence as a whole.
There is debate about the
heritability of IQ, that is, what proportion of differences in IQ test performance between individuals are explained by
genetic or
environmental factors.
The scientific consensus is that genetics does not explain
average differences in IQ test performance between racial groups.
Emotional
Emotional intelligence is thought to be the ability to convey
emotion
Emotions are physical and mental states brought on by neurophysiology, neurophysiological changes, variously associated with thoughts, feelings, behavior, behavioral responses, and a degree of pleasure or suffering, displeasure. There is ...
to others in an understandable way as well as to read the emotions of others accurately.
Some theories imply that a heightened emotional intelligence could also lead to faster generating and processing of emotions in addition to the accuracy. In addition, higher emotional intelligence is thought to help us manage emotions, which is beneficial for our problem-solving skills. Emotional intelligence is important to our
mental health
Mental health is often mistakenly equated with the absence of mental illness. However, mental health refers to a person's overall emotional, psychological, and social well-being. It influences how individuals think, feel, and behave, and how t ...
and has ties to social intelligence.
Social
Social intelligence is the ability to understand the
social cues and motivations of others and oneself in social situations. It is thought to be distinct from other types of intelligence, but has relations to emotional intelligence. Social intelligence has coincided with other studies that focus on how we make judgements of others, the accuracy with which we do so, and why people would be viewed as having positive or negative
social character. There is debate as to whether or not these studies and social intelligence come from the same theories or if there is a distinction between them, and they are generally thought to be of two different
schools of thought.
Moral
Moral intelligence is the capacity to understand right from wrong and to behave based on the value that is believed to be right.
[']
The Step-By-Step Plan to Building Moral Intelligence
Retrieved 28 April 2016. It is considered a distinct form of intelligence, independent to both emotional and cognitive intelligence.
Book smart and street smart
Concepts of "book smarts" and "street smart" are contrasting views based on the premise that some people have knowledge gained through academic study, but may lack the experience to sensibly apply that knowledge, while others have knowledge gained through practical experience, but may lack accurate information usually gained through study by which to effectively apply that knowledge.
Artificial intelligence
Artificial intelligence (AI) is the capability of computer, computational systems to perform tasks typically associated with human intelligence, such as learning, reasoning, problem-solving, perception, and decision-making. It is a field of re ...
researcher
Hector Levesque has noted that:
Nonhuman animal

Although humans have been the primary focus of intelligence researchers, scientists have also attempted to investigate animal intelligence, or more broadly, animal cognition. These researchers are interested in studying both mental ability in a particular
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, and comparing abilities between species. They study various measures of problem solving, as well as numerical and verbal reasoning abilities. Some challenges include defining intelligence so it has the same meaning across species, and
operationalizing a measure that accurately compares mental ability across species and contexts.
Wolfgang Köhler
Wolfgang Köhler (; 21 January 1887 – 11 June 1967) was a German psychologist and phenomenologist who, like Max Wertheimer and Kurt Koffka, contributed to the creation of Gestalt psychology.
During the Nazi regime in Germany, he pro ...
's research on the intelligence of apes is an example of research in this area, as is Stanley Coren's book, ''
The Intelligence of Dogs''. Non-human animals particularly noted and studied for their intelligence include
chimpanzee
The chimpanzee (; ''Pan troglodytes''), also simply known as the chimp, is a species of Hominidae, great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close rel ...
s,
bonobo
The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee (less often the dwarf chimpanzee or gracile chimpanzee), is an endangered great ape and one of the two species making up the genus ''Pan (genus), Pan'' (the other bei ...
s (notably the language-using
Kanzi) and other
great apes,
dolphins,
elephant
Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s and to some extent
parrot
Parrots (Psittaciformes), also known as psittacines (), are birds with a strong curved beak, upright stance, and clawed feet. They are classified in four families that contain roughly 410 species in 101 genus (biology), genera, found mostly in ...
s,
rats and
ravens.
Cephalopod intelligence provides an important comparative study.
Cephalopod
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
s appear to exhibit characteristics of significant intelligence, yet their
nervous system
In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...
s differ radically from those of backboned animals. Vertebrates such as
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s,
bird
Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s,
reptile
Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...
s and
fish have shown a fairly high degree of intellect that varies according to each species. The same is true with
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s.
''g'' factor in non-humans
Evidence of a general factor of intelligence has been observed in non-human animals. First described in
humans, the ''g'' factor has since been identified in a number of non-human species.
[Reader, S. M., Hager, Y., & Laland, K. N. (2011). "The evolution of primate general and cultural intelligence". ''Philosophical Transactions of the Royal Society'' B: Biological Sciences, 366(1567), 1017–1027.]
Cognitive ability and intelligence cannot be measured using the same, largely verbally dependent, scales developed for humans. Instead, intelligence is measured using a variety of interactive and observational tools focusing on
innovation
Innovation is the practical implementation of ideas that result in the introduction of new goods or service (economics), services or improvement in offering goods or services. ISO TC 279 in the standard ISO 56000:2020 defines innovation as "a n ...
,
habit reversal,
social learning, and responses to
novelty. Studies have shown that ''g'' is responsible for 47% of the individual variance in cognitive ability measures in
primates and between 55% and 60% of the variance in
mice (Locurto, Locurto). These values are similar to the accepted variance in
IQ explained by ''g'' in humans (40–50%).
Plant
It has been argued that plants should also be classified as intelligent based on their ability to sense and model external and internal environments and adjust their
morphology,
physiology and
phenotype accordingly to ensure self-preservation and reproduction.
A counter argument is that intelligence is commonly understood to involve the creation and use of persistent memories as opposed to computation that does not involve learning. If this is accepted as definitive of intelligence, then it includes the artificial intelligence of robots capable of "machine learning", but excludes those purely autonomic sense-reaction responses that can be observed in many plants. Plants are not limited to automated sensory-motor responses, however, they are capable of discriminating positive and negative experiences and of "learning" (registering memories) from their past experiences. They are also capable of communication, accurately computing their circumstances, using sophisticated
cost–benefit analysis and taking tightly controlled actions to mitigate and control the diverse environmental stressors.
Artificial
Scholars studying artificial intelligence have proposed definitions of intelligence that include the intelligence demonstrated by machines. Some of these definitions are meant to be general enough to encompass human and other animal intelligence as well. An
intelligent agent
In artificial intelligence, an intelligent agent is an entity that Machine perception, perceives its environment, takes actions autonomously to achieve goals, and may improve its performance through machine learning or by acquiring knowledge r ...
can be defined as a system that perceives its environment and takes actions which maximize its chances of success.
Kaplan and Haenlein define artificial intelligence as "a system's ability to correctly interpret external data, to learn from such data, and to use those learnings to achieve specific goals and tasks through flexible adaptation".
Progress in artificial intelligence can be demonstrated in benchmarks ranging from games to practical tasks such as
protein folding. Existing AI lags humans in terms of general intelligence, which is sometimes defined as the "capacity to learn how to carry out a huge range of tasks".
Mathematician
Olle Häggström defines intelligence in terms of "optimization power", an agent's capacity for efficient cross-domain
optimization
Mathematical optimization (alternatively spelled ''optimisation'') or mathematical programming is the selection of a best element, with regard to some criteria, from some set of available alternatives. It is generally divided into two subfiel ...
of the world according to the agent's preferences, or more simply the ability to "steer the future into regions of possibility ranked high in a preference ordering". In this optimization framework,
Deep Blue has the power to "steer a chessboard's future into a subspace of possibility which it labels as 'winning', despite attempts by
Garry Kasparov to steer the future elsewhere."
Hutter and
Legg, after surveying the literature, define intelligence as "an agent's ability to achieve goals in a wide range of environments". While cognitive ability is sometimes measured as a one-dimensional parameter, it could also be represented as a "
hypersurface in a multidimensional space" to compare systems that are good at different intellectual tasks. Some skeptics believe that there is no meaningful way to define intelligence, aside from "just pointing to ourselves".
See also
References
Further reading
*
Gleick, James, "The Fate of Free Will" (review of
Kevin J. Mitchell, ''Free Agents: How Evolution Gave Us Free Will'', Princeton University Press, 2023, 333 pp.), ''
The New York Review of Books'', vol. LXXI, no. 1 (18 January 2024), pp. 27–28, 30. "
Agency is what distinguishes us from machines. For biological creatures,
reason and
purpose come from acting in the world and experiencing the consequences. Artificial intelligences – disembodied, strangers to blood, sweat, and tears – have no occasion for that." (p. 30.)
*
Hughes-Castleberry, Kenna, "A Murder Mystery Puzzle: The literary puzzle ''
Cain's Jawbone'', which has stumped humans for decades, reveals the limitations of natural-language-processing algorithms", ''
Scientific American'', vol. 329, no. 4 (November 2023), pp. 81–82. "This murder mystery competition has revealed that although NLP (
natural-language processing) models are capable of incredible feats, their abilities are very much limited by the amount of
context they receive. This
..could cause
ifficultiesfor researchers who hope to use them to do things such as analyze
ancient languages. In some cases, there are few historical records on long-gone
civilization
A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
s to serve as
training data for such a purpose." (p. 82.)
*
Immerwahr, Daniel, "Your Lying Eyes: People now use A.I. to generate fake videos indistinguishable from real ones. How much does it matter?", ''
The New Yorker
''The New Yorker'' is an American magazine featuring journalism, commentary, criticism, essays, fiction, satire, cartoons, and poetry. It was founded on February 21, 1925, by Harold Ross and his wife Jane Grant, a reporter for ''The New York T ...
'', 20 November 2023, pp. 54–59. "If by '
deepfakes' we mean realistic videos produced using artificial intelligence that actually deceive people, then they barely exist. The fakes aren't deep, and the deeps aren't fake.
..A.I.-generated videos are not, in general, operating in our media as counterfeited evidence. Their role better resembles that of
cartoons, especially smutty ones." (p. 59.)
*
Press, Eyal, "In Front of Their Faces: Does facial-recognition technology lead police to ignore contradictory evidence?", ''
The New Yorker
''The New Yorker'' is an American magazine featuring journalism, commentary, criticism, essays, fiction, satire, cartoons, and poetry. It was founded on February 21, 1925, by Harold Ross and his wife Jane Grant, a reporter for ''The New York T ...
'', 20 November 2023, pp. 20–26.
*
Roivainen, Eka, "AI's IQ:
ChatGPT aced a
tandard intelligencetest but showed that intelligence cannot be measured by
IQ alone", ''
Scientific American'', vol. 329, no. 1 (July/August 2023), p. 7. "Despite its high IQ,
ChatGPT fails at tasks that require real humanlike reasoning or an understanding of the physical and social world.... ChatGPT seemed unable to reason logically and tried to rely on its vast database of... facts derived from online texts."
*
Cukier, Kenneth, "Ready for Robots? How to Think about the Future of AI", ''
Foreign Affairs
''Foreign Affairs'' is an American magazine of international relations and foreign policy of the United States, U.S. foreign policy published by the Council on Foreign Relations, a nonprofit organization, nonprofit, nonpartisan, membership or ...
'', vol. 98, no. 4 (July/August 2019), pp. 192–98.
George Dyson, historian of computing, writes (in what might be called "Dyson's Law") that "Any system simple enough to be understandable will not be complicated enough to behave intelligently, while any system complicated enough to behave intelligently will be too complicated to understand." (p. 197.) Computer scientist
Alex Pentland writes: "Current
AI machine-learning algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
s are, at their core, dead simple stupid. They work, but they work by brute force." (p. 198.)
*
Domingos, Pedro, "Our Digital Doubles: AI will serve our species, not control it", ''
Scientific American'', vol. 319, no. 3 (September 2018), pp. 88–93. "AIs are like
autistic savants and will remain so for the foreseeable future.... AIs lack
common sense and can easily make errors that a human never would... They are also liable to take our instructions too literally, giving us precisely what we asked for instead of what we actually wanted." (p. 93.)
*
Marcus, Gary, "Am I Human?: Researchers need new ways to distinguish artificial intelligence from the natural kind", ''
Scientific American'', vol. 316, no. 3 (March 2017), pp. 61–63. Marcus points out a so far insuperable stumbling block to artificial intelligence: an incapacity for reliable
disambiguation. "
rtually every sentence
hat people generateis
ambiguous, often in multiple ways. Our brain is so good at comprehending
language
Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...
that we do not usually notice." A prominent example is the "pronoun disambiguation problem" ("PDP"): a machine has no way of determining to whom or what a
pronoun in a sentence—such as "he", "she" or "it"—refers.
*
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External links
*
History of Influences in the Development of Intelligence Theory and Testing . Developed by
Jonathan Plucker at
Indiana University.
The Limits of Intelligence: The laws of physics may well prevent the human brain from evolving into an ever more powerful thinking machine By Douglas Fox in ''
Scientific American'', 14 June 2011.
A Collection of Definitions of Intelligence
{{Authority control
Developmental psychology
Psychological testing
Differential psychology