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Human intelligence is the
intellectual An intellectual is a person who engages in critical thinking, research, and Human self-reflection, reflection about the nature of reality, especially the nature of society and proposed solutions for its normative problems. Coming from the wor ...
capability of
humans 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 ...
, which is marked by complex
cognitive Cognition is the "mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, thought, ...
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 In philosophy of self, philosophy, self-awareness is the awareness and reflection of one's own personality or individuality, including traits, feelings, and behaviors. It is not to be confused with consciousness in the sense of qualia. While ...
. Using their
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. It can be described as t ...
, humans are able to
learn 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 ...
, form concepts, understand, and apply
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 ...
and
reason Reason is the capacity of consciously applying logic by drawing valid conclusions from new or existing information, with the aim of seeking the truth. It is associated with such characteristically human activities as philosophy, religion, scien ...
. Human intelligence is also thought to encompass their capacities to recognize patterns,
plan A plan is typically any diagram or list of steps with details of timing and resources, used to achieve an Goal, objective to do something. It is commonly understood as a modal logic, temporal set (mathematics), set of intended actions through wh ...
, innovate, solve problems, make decisions, retain information, and use
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 Communication is commonly defined as the transmission of information. Its precise definition is disputed and there are disagreements about whether unintentional or failed transmissions are included and whether communication not only transmit ...
. There are conflicting ideas about how intelligence should be conceptualized and measured. In
psychometrics Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and rela ...
, human intelligence is commonly assessed by
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, although the validity of these tests is disputed. Several subcategories of intelligence, such as
emotional intelligence Emotional intelligence (EI), also known as emotional quotient (EQ), is the ability to perceive, use, understand, manage, and handle emotions. High emotional intelligence includes emotional recognition of emotions of the self and others, using ...
and
social intelligence Social intelligence (SI), sometimes referenced as social intelligence quotient or (SQ), is the ability to understand one's own and others' actions. Social intelligence is learned and develops from experience with people and learning from success an ...
, have been proposed, and there remains significant debate as to whether these represent distinct forms of intelligence. There is also ongoing debate regarding how an individual's level of intelligence is formed, ranging from the idea that intelligence is fixed at birth to the idea that it is malleable and can change depending on a person's mindset and efforts.


History


Correlates

As a construct and as measured by
intelligence tests 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 ...
, intelligence is one of the most useful concepts in
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 ...
, because it correlates with many relevant variables, for instance the probability of suffering an accident, or the amount of one's salary. Other examples include: ; Education: According to a 2018 metastudy of educational effects on intelligence, education appears to be the "most consistent, robust, and durable method" known for raising intelligence. ; Personality: A landmark set of meta-analyses synthesizing thousands of studies including millions of people from over 50 countries found that many personality traits are intricately related to cognitive abilities. Neuroticism-related traits display the most negative relations, whereas traits like activity, industriousness, compassion, and openness are positively related to various abilities. ; Myopia: A number of studies have shown a correlation between IQ and
myopia Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. ...
. Some suggest that the reason for the correlation is environmental: either people with a higher IQ are more likely to damage their eyesight with prolonged reading, or people who read more are more likely to attain a higher IQ; others contend that a genetic link exists. ; Aging: There is evidence that aging causes a decline in cognitive functions. In one cross-sectional study, various cognitive functions measured declines by about 0.8 in
z-score In statistics, the standard score or ''z''-score is the number of standard deviations by which the value of a raw score (i.e., an observed value or data point) is above or below the mean value of what is being observed or measured. Raw scores ...
from age 20 to age 50; the cognitive functions included speed of processing, working memory, and long-term memory. ; Genes: A number of
single-nucleotide polymorphism In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a ...
s in human
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
are correlated with higher IQ scores.


Theories


Relevance of IQ tests

In
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 ...
, human intelligence is commonly assessed by IQ scores that are determined by IQ tests. In general, higher IQ scores are associated with better outcomes in life. However, while IQ test scores show a high degree of inter-test
reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), a property of some disk arrays in computer storage * Reliability (computer networking), a category used to des ...
, and predict certain forms of achievement effectively, their
construct validity Construct validity concerns how well a set of indicators represent or reflect a concept that is not directly measurable. ''Construct validation'' is the accumulation of evidence to support the interpretation of what a measure reflects.Polit DF Bec ...
as a holistic measure of human intelligence is considered dubious. While IQ tests are generally understood to measure some forms of intelligence, they may fail to serve as an accurate measure of broader definitions of human intelligence inclusive of
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 ...
and
social intelligence Social intelligence (SI), sometimes referenced as social intelligence quotient or (SQ), is the ability to understand one's own and others' actions. Social intelligence is learned and develops from experience with people and learning from success an ...
. According to psychologist Wayne Weiten, "IQ tests are valid measures of the kind of intelligence necessary to do well in academic work. But if the purpose is to assess intelligence in a broader sense, the validity of IQ tests is questionable."


Theory of multiple intelligences

Howard Gardner Howard Earl Gardner (born July 11, 1943) is an American developmental psychologist and the John H. and Elisabeth A. Hobbs Research Professor of Cognition and Education at Harvard University. He was a founding member of Harvard Project Zero in 1967 ...
's
theory of multiple intelligences The theory of multiple intelligences (MI) posits that human intelligence is not a single general ability but comprises various distinct modalities, such as linguistic, logical-mathematical, musical, and spatial intelligences. Introduced in Howar ...
is based on studies of normal children and adults, of gifted individuals (including so-called "
savant Savant syndrome ( , ) is a phenomenon where someone demonstrates exceptional aptitude in one domain, such as art or mathematics, despite significant social or intellectual impairment. Those with the condition generally have a neurodevel ...
s"), of persons who have suffered brain damage, of experts and
virtuoso A virtuoso (from Italian ''virtuoso'', or ; Late Latin ''virtuosus''; Latin ''virtus''; 'virtue', 'excellence' or 'skill') is an individual who possesses outstanding talent and technical ability in a particular art or field such as fine arts, ...
s, and of individuals from diverse cultures. Gardner breaks intelligence down into components. In the first edition of his book ''Frames of Mind'' (1983), he described seven distinct types of intelligence: logical-mathematical,
linguistic Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...
, spatial, musical,
kinesthetic Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...
,
interpersonal In social psychology, an interpersonal relation (or interpersonal relationship) describes a social association, connection, or affiliation between two or more people. It overlaps significantly with the concept of social relations, which are ...
, and
intrapersonal Intrapersonal communication (also known as autocommunication or inner speech) is communication with oneself or self-to-self communication. Examples are thinking to oneself "I will do better next time" after having made a mistake or imagining a ...
. In a second edition, he added two more types of intelligence: naturalist and existential intelligences. He argues that
psychometric Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and rela ...
(IQ) tests address only linguistic and logical plus some aspects of spatial intelligence. A criticism of Gardner's theory is that it has never been tested, or subjected to peer review, by Gardner or anyone else, and indeed that it is
unfalsifiable Falsifiability (or refutability) is a deductive standard of evaluation of scientific theories and hypotheses, introduced by the philosopher of science Karl Popper in his book '' The Logic of Scientific Discovery'' (1934). A theory or hypothesi ...
. Others (e.g. Locke, 2005) suggest that recognizing many specific forms of intelligence (specific aptitude theory) implies a political—rather than scientific—agenda, intended to appreciate the uniqueness in all individuals, rather than recognizing potentially true and meaningful differences in individual capacities. Schmidt and Hunter suggest that the predictive validity of specific aptitudes over and above that of general mental ability, or "g", has not received empirical support. On the other hand,
Jerome Bruner Jerome Seymour Bruner (October 1, 1915 – June 5, 2016) was an American psychologist who made significant contributions to human cognitive psychology and cognitive learning theory (education), learning theory in educational psychology. Bruner was ...
agreed with Gardner that the intelligences were "useful fictions", and went on to state that "his approach is so far beyond the data-crunching of mental testers that it deserves to be cheered."


Triarchic theory of intelligence

Robert Sternberg Robert J. Sternberg (born December 8, 1949) is an American psychologist and psychometrician. He is a Professor of Human Development at Cornell University. Sternberg has a BA from Yale University and a PhD from Stanford University, under adviso ...
proposed the
triarchic theory of intelligence The triarchic theory of intelligence or three forms of intelligence, formulated by psychologist Robert Sternberg, aims to go against the psychometrics, psychometric approach to intelligence and take a more cognitive sciences, cognitive approach, wh ...
to provide a more comprehensive description of intellectual competence than traditional differential or cognitive theories of human ability. The triarchic theory describes three fundamental aspects of intelligence: # Analytic intelligence comprises the mental processes through which intelligence is expressed. # Creative intelligence is necessary when an individual is confronted with a challenge that is nearly, but not entirely, novel or when an individual is engaged in automatizing the performance of a task. # Practical intelligence is bound to a sociocultural milieu and involves adaptation to, selection of, and shaping of the environment to maximize fit in the context. The triarchic theory does not argue against the validity of a general intelligence factor; instead, the theory posits that general intelligence is part of analytic intelligence, and only by considering all three aspects of intelligence can the full range of intellectual functioning be understood. Sternberg updated the triarchic theory and renamed it to the Theory of Successful Intelligence. He now defines intelligence as an individual's assessment of success in life by the individual's own ( idiographic) standards and within the individual's sociocultural context. Success is achieved by using combinations of analytical, creative, and practical intelligence. The three aspects of intelligence are referred to as processing skills. The processing skills are applied to the pursuit of success through what were the three elements of practical intelligence: adapting to, shaping of, and selecting of one's environments. The mechanisms that employ the processing skills to achieve success include utilizing one's strengths and compensating or correcting for one's weaknesses. Sternberg's theories and research on intelligence remain contentious within the scientific community.


PASS theory of intelligence

Based on A. R. Luria's (1966) seminal work on the modularization of brain function, and supported by decades of neuroimaging research, the PASS Theory of Intelligence (Planning/Attention/Simultaneous/Successive) proposes that cognition is organized in three systems and the following four processes: # Planning involves executive functions responsible for controlling and organizing behavior, selecting and constructing strategies, and monitoring performance. # Attention is responsible for maintaining arousal levels and alertness, and ensuring focus on relevant stimuli. # Simultaneous processing is engaged when the relationship between items and their integration into whole units of information is required. Examples of this include recognizing figures, such as a triangle within a circle vs. a circle within a triangle, or the difference between "he had a shower before breakfast" and "he had breakfast before a shower." # Successive processing is required for organizing separate items in a sequence such as remembering a sequence of words or actions exactly in the order in which they had just been presented. These four processes are functions of four areas of the brain. Planning is broadly located in the front part of our brains, the frontal lobe. Attention and arousal are combined functions of the frontal lobe and the lower parts of the cortex, although the parietal lobes are also involved in attention as well. Simultaneous processing and Successive processing occur in the posterior region or the back of the brain. Simultaneous processing is broadly associated with the occipital and the parietal lobes while Successive processing is broadly associated with the frontal-temporal lobes. The PASS theory is heavily indebted both to Luria and to studies in cognitive psychology involved in promoting a better look at intelligence.


Piaget's theory and Neo-Piagetian theories

In
Piaget's theory of cognitive development Piaget's theory of cognitive development, or his genetic epistemology, is a comprehensive theory about the nature and development of human intelligence. It was originated by the Swiss developmental psychologist Jean Piaget (1896–1980). The the ...
the focus is not on mental abilities but rather on a child's mental models of the world. As a child develops, the child creates increasingly more accurate models of the world which enable the child to interact with the world more effectively. One example is
object permanence Object permanence is the understanding that whether an object can be sensed has no effect on whether it continues to exist. This is a fundamental concept studied in the field of developmental psychology, the subfield of psychology that addres ...
with which the child develops a model in which objects continue to exist even when they cannot be seen, heard, or touched. Piaget's theory described four main stages and many sub-stages in the development. These four main stages are: # sensorimotor stage (birth–2 years) # pre-operational stage (2–7 years) # concrete operational stage (7–11 years) # formal operations stage (11–16 years) Progress through these stages is correlated with, but not identical to psychometric IQ. Piaget conceptualizes intelligence as an activity more than as a capacity. One of Piaget's most famous studies focused purely on the discriminative abilities of children between the ages of two and a half years old, and four and a half years old. He began the study by taking children of different ages and placing two lines of sweets, one with the sweets in a line spread further apart, and one with the same number of sweets in a line placed more closely together. He found that, "Children between 2 years, 6 months old and 3 years, 2 months old correctly discriminate the relative number of objects in two rows; between 3 years, 2 months and 4 years, 6 months they indicate a longer row with fewer objects to have 'more'; after 4 years, 6 months they again discriminate correctly". Initially younger children were not studied, because if at the age of four years a child could not conserve quantity, then a younger child presumably could not either. The results show however that children that are younger than three years and two months have quantity conservation, but as they get older they lose this quality, and do not recover it until four and a half years old. This attribute may be lost temporarily because of an overdependence on perceptual strategies, which correlates more candy with a longer line of candy, or because of the inability for a four-year-old to reverse situations. This experiment demonstrated several results. First, younger children have a discriminative ability that shows the logical capacity for cognitive operations exists earlier than previously acknowledged. Also, young children can be equipped with certain qualities for cognitive operations, depending on how logical the structure of the task is. Research also shows that children develop explicit understanding at age five and as a result, the child will count the sweets to decide which has more. Finally the study found that overall quantity conservation is not a basic characteristic of humans' native inheritance. Piaget's theory has been criticized on the grounds that the age of appearance of a new model of the world, such as object permanence, is dependent on how the testing is done (see the article on
object permanence Object permanence is the understanding that whether an object can be sensed has no effect on whether it continues to exist. This is a fundamental concept studied in the field of developmental psychology, the subfield of psychology that addres ...
). More generally, the theory may be very difficult to test empirically because of the difficulty of proving or disproving that a mental model is the explanation for the results of the testing.
Neo-Piagetian theories of cognitive development Neo-Piagetian theories of cognitive development criticize and build upon Jean Piaget's theory of cognitive development. Overview The neo-Piagetian theories aim to correct one or more of the following weaknesses in Piaget's theory: * Piaget's de ...
expand Piaget's theory in various ways such as also considering psychometric-like factors such as processing speed and working memory, "hypercognitive" factors like self-monitoring, more stages, and more consideration on how progress may vary in different domains such as spatial or social.


Parieto-frontal integration theory of intelligence

Based on a review of 37
neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the neuroanatomy, structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive ...
studies, Jung and Haier proposed that the biological basis of intelligence stems from how well the frontal and parietal regions of the brain communicate and exchange information with each other. Subsequent neuroimaging and lesion studies report general consensus with the theory. A review of the neuroscience and intelligence literature concludes that the parieto-frontal integration theory is the best available explanation for human intelligence differences.


Investment theory

Based on the Cattell–Horn–Carroll theory, the tests of intelligence most often used in the studies include measures of fluid ability (''gf'') and crystallized ability (''gc''); that differ in their trajectory of development in people. The "investment theory" by Cattell states that the
individual differences Differential psychology studies the ways in which individuals differ in their behavior and the processes that underlie it. It is a discipline that develops classifications ( taxonomies) of psychological individual differences. This is distinguish ...
observed in the procurement of skills and knowledge (''gc'') are partially attributed to the "investment" of ''gf'', thus suggesting the involvement of fluid intelligence in every aspect of the learning process. The investment theory suggests that personality traits affect "actual" ability, and not scores on an IQ test. Hebb's theory of intelligence suggested a bifurcation as well, Intelligence A (physiological), that could be seen as a semblance of fluid intelligence and Intelligence B (experiential), similar to crystallized intelligence.


Intelligence compensation theory (ICT)

The intelligence compensation theory states that individuals who are comparatively less intelligent work harder and more methodically, and become more resolute and thorough (more conscientious) in order to achieve goals, to compensate for their "lack of intelligence" whereas more intelligent individuals do not require traits/behaviours associated with the personality factor
conscientiousness Conscientiousness is the personality trait of being responsible, :wikt:careful, careful, or :wikt:diligent, diligent. Conscientiousness implies a desire to do a task well, and to take obligations to others seriously. Conscientious people tend to ...
to progress as they can rely on the strength of their cognitive abilities as opposed to structure or effort. The theory suggests the existence of a causal relationship between intelligence and conscientiousness, such that the development of the personality trait of conscientiousness is influenced by intelligence. This assumption is deemed plausible as it is unlikely that the reverse causal relationship could occur; implying that the negative correlation would be higher between fluid intelligence (''gf'') and conscientiousness. This is justified by the timeline of development of ''gf'', ''gc'', and personality, as crystallized intelligence would not have developed completely when personality traits develop. Subsequently, during school-going ages, more conscientious children would be expected to gain more crystallized intelligence (knowledge) through education, as they would be more efficient, thorough, hard-working, and dutiful. This theory has recently been contradicted by evidence that identifies ''compensatory sample selection'' which attributes the findings to the bias that comes from selecting samples containing people above a certain threshold of achievement.


Bandura's theory of self-efficacy and cognition

The view of cognitive ability has evolved over the years, and , comprising not only cognitive, but motivational, social, and behavioural aspects as well. These facets work together to perform numerous tasks. An essential skill often overlooked is that of managing emotions and aversive experiences that can compromise one's quality of thought and activity. Bandura bridges the link between intelligence and success by crediting individual differences in
self-efficacy In psychology, self-efficacy is an individual's belief in their capacity to act in the ways necessary to reach specific goals. The concept was originally proposed by the psychologist Albert Bandura in 1977. Self-efficacy affects every area of hum ...
. Bandura's theory identifies the difference between possessing skills and being able to apply them in challenging situations. The theory suggests that individuals with the same level of knowledge and skill may perform badly, averagely, or excellently based on differences in self-efficacy. A key role of cognition is to allow for one to predict events and in turn devise methods to deal with these events effectively. These skills are dependent on processing of unclear and ambiguous stimuli. People must be able to rely on their reserve of knowledge to identify, develop, and execute options. They must be able to apply the learning acquired from previous experiences. Thus, a stable sense of self-efficacy is essential to stay focused on tasks in the face of challenging situations. Bandura's theory of self-efficacy and intelligence suggests that individuals with a relatively low sense of self-efficacy in any field will avoid challenges. This effect is heightened when they perceive the situations as ''personal threats''. When failure occurs, they recover from it more slowly than others, and credit the failure to an insufficient aptitude. On the other hand, persons with high levels of self-efficacy hold that leads to effective performance.


Process, personality, intelligence and knowledge theory (PPIK)

Developed by Ackerman, the PPIK (process, personality, intelligence, and knowledge) theory further develops the approach on intelligence as proposed by Cattell, the
Investment theory Investment is traditionally defined as the "commitment of resources into something expected to gain value over time". If an investment involves money, then it can be defined as a "commitment of money to receive more money later". From a broade ...
, and Hebb, suggesting a distinction between ''intelligence as knowledge'' and ''intelligence as process'' (two concepts that are comparable and related to ''gc'' and ''gf'' respectively, but broader and closer to Hebb's notions of "Intelligence A" and "Intelligence B") and integrating these factors with elements such as personality, motivation, and interests. Ackerman describes the difficulty of distinguishing process from knowledge, as content cannot be eliminated from any ability test. Personality traits are not significantly correlated with the ''intelligence as process'' aspect except in the context of psychopathology. One exception to this generalization has been the finding of sex differences in cognitive abilities, specifically abilities in mathematical and spatial form. On the other hand, the ''intelligence as knowledge'' factor has been associated with personality traits of Openness and Typical Intellectual Engagement, which also strongly correlate with verbal abilities (associated with crystallized intelligence).


Latent inhibition

It appears that Latent inhibition, the phenomenon of familiar stimuli having a postponed reaction time when compared with unfamiliar stimuli, has a positive correlation with
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 ...
.


Improving


Genetic engineering

Because intelligence appears to be at least partly dependent on brain structure and the genes shaping brain development, it has been proposed that
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the genet ...
could be used to enhance intelligence, a process sometimes called biological uplift in
science fiction Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...
. Genetic enhancement experiments on mice have demonstrated superior ability in learning and memory in various behavioral tasks.


Education

Higher IQ leads to greater success in education, but independently, education raises IQ scores. A 2017 meta-analysis suggests education increases IQ by 1–5 points per year of education, or at least increases IQ test-taking ability.


Nutrition and chemicals

Substances which actually or purportedly improve intelligence or other mental functions are called
nootropic Nootropics ( or ) (colloquially brain supplements, smart drugs, cognitive enhancers, memory enhancers, or brain boosters) are chemical substances which purportedly improve cognitive functions, such as attention, memory, wakefulness, and self ...
s. A meta analysis shows omega-3 fatty acids improve cognitive performance among those with cognitive deficits, but not among healthy subjects. A meta-regression shows omega-3 fatty acids improve the moods of patients with major depression (major depression is associated with cognitive nutrient deficits).


Activities and adult neural development

* Exercise enhances cognition for healthy and non healthy subjects * Which (e.g. "intellectually demanding work") and how one does
work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking ** Working animal, an ani ...
* Quality of
sleep Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain Sensory nervous system, sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with th ...


Digital tools


Digital media


Brain training

Attempts to raise IQ with brain training have led to increases on aspects related with the training tasks – for instance
working memory Working memory is a cognitive system with a limited capacity that can Memory, hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term m ...
– but it is yet unclear if these increases generalize to increased intelligence per se. A 2008 research paper claimed that practicing a dual n-back task can increase fluid intelligence (''gf''), as measured in several different standard tests. This finding received some attention from popular media, including an article in ''
Wired Wired may refer to: Arts, entertainment, and media Music * ''Wired'' (Jeff Beck album), 1976 * ''Wired'' (Hugh Cornwell album), 1993 * ''Wired'' (Mallory Knox album), 2017 * "Wired", a song by Prism from their album '' Beat Street'' * "Wired ...
''. However, a subsequent criticism of the paper's methodology questioned the experiment's validity and took issue with the lack of uniformity in the tests used to evaluate the control and test groups. For example, the progressive nature of Raven's Advanced Progressive Matrices (APM) test may have been compromised by modifications of time restrictions (i.e., 10 minutes were allowed to complete a normally 45-minute test).


Philosophy

Efforts to influence intelligence raise ethical issues. Neuroethics considers the ethical, legal, and social implications of neuroscience, and deals with issues such as the difference between treating a human
neurological Neurology (from , "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the s ...
disease and enhancing the human brain, and how wealth impacts access to neurotechnology. Neuroethical issues interact with the ethics of
human genetic engineering Human genetic enhancement or human genetic engineering refers to human enhancement by means of a genetic modification. This could be done in order to cure diseases (gene therapy), prevent the possibility of getting a particular disease (similarly ...
.
Transhumanist Transhumanism is a philosophical and intellectual movement that advocates the human enhancement, enhancement of the human condition by developing and making widely available new and future technologies that can greatly enhance longevity, cogni ...
theorists study the possibilities and consequences of developing and using techniques to enhance human abilities and aptitudes.
Eugenics Eugenics is a set of largely discredited beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter the frequency of various human phenotypes by inhibiting the fer ...
is a social philosophy that advocates the improvement of human hereditary traits through various forms of intervention. Eugenics has variously been regarded as meritorious or deplorable in different periods of history, falling greatly into disrepute after the defeat of
Nazi Germany Nazi Germany, officially known as the German Reich and later the Greater German Reich, was the German Reich, German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a Totalit ...
in
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
.


Measuring

The approach to understanding intelligence with the most supporters and published research over the longest period of time is based on
psychometric Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and rela ...
testing. It is also by far the most widely used in practical settings.
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 include the Stanford-Binet,
Raven's Progressive Matrices Raven's Progressive Matrices (often referred to simply as Raven's Matrices) or RPM is a non-verbal test typically used to measure general human intelligence and abstract reasoning and is regarded as a non-verbal estimate of fluid intelligence. I ...
, the
Wechsler Adult Intelligence Scale The Wechsler Adult Intelligence Scale (WAIS) is an IQ test designed to measure intelligence and cognitive ability in adults and older adolescents. For children between the ages of 6 and 16, Wechsler Intelligence Scale for Children (WISC) is com ...
and the Kaufman Assessment Battery for Children. There are also psychometric tests that are not intended to measure intelligence itself but some closely related construct such as scholastic aptitude. In the United States examples include the SSAT, the
SAT The SAT ( ) is a standardized test widely used for college admissions in the United States. Since its debut in 1926, its name and Test score, scoring have changed several times. For much of its history, it was called the Scholastic Aptitude Test ...
, the ACT, the GRE, the
MCAT The Medical College Admission Test (MCAT; ) is a computer-based standardized examination for prospective medical students in the United States, Canada, Australia, and the Caribbean Islands. It is designed to assess problem solving, critical ...
, the LSAT, and the
GMAT The Graduate Management Admission Test (GMAT ( ())) is a computer adaptive test (CAT) intended to assess certain analytical, quantitative, verbal, and data literacy skills for use in admission to a graduate management program, such as a Mast ...
. Regardless of the method used, almost any test that requires examinees to reason and has a wide range of question difficulty will produce intelligence scores that are approximately
normally distributed In probability theory and statistics, a normal distribution or Gaussian distribution is a type of continuous probability distribution for a real number, real-valued random variable. The general form of its probability density function is f(x ...
in the general population. Intelligence tests are widely used in educational, business, and military settings because of their efficacy in predicting behavior. IQ and ''g'' (discussed in the next section) are correlated with many important social outcomes—individuals with low IQs are more likely to be divorced, have a child out of marriage, be incarcerated, and need long-term welfare support, while individuals with high IQs are associated with more years of education, higher status jobs and higher income. Intelligence as measured by Psychometric tests has been found to be highly correlated with successful training and performance outcomes (e.g., adaptive performance), and IQ/''g'' is the single best predictor of successful job performance; however, some researchers although largely concurring with this finding have advised caution in citing the strength of the claim due to a number of factors, these include: statistical assumptions imposed underlying some of these studies, studies done prior to 1970 which appear inconsistent with more recent studies, and ongoing debates within the Psychology literature as to the validity of current IQ measurement tools.


General intelligence factor or ''g''

There are many different kinds of IQ tests using a wide variety of test tasks. Some tests consist of a single type of task, others rely on a broad collection of tasks with different contents (visual-spatial, verbal, numerical) and asking for different cognitive processes (e.g., reasoning, memory, rapid decisions, visual comparisons, spatial imagery, reading, and retrieval of
general knowledge General knowledge is information that has been accumulated over time through various media and sources. It excludes specialized learning that can only be obtained with extensive training and information confined to a single medium. General know ...
). The psychologist
Charles Spearman Charles Edward Spearman, FRS (10 September 1863 – 17 September 1945) was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient. He also did seminal work on mod ...
early in the 20th century carried out the first formal
factor analysis Factor analysis is a statistical method used to describe variability among observed, correlated variables in terms of a potentially lower number of unobserved variables called factors. For example, it is possible that variations in six observe ...
of
correlation In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics ...
s between various test tasks. He found a trend for all such tests to correlate positively with each other, which is called a ''positive manifold''. Spearman found that a single common factor explained the positive correlations among tests. Spearman named it ''g'' for " general intelligence factor". He interpreted it as the core of human intelligence that, to a larger or smaller degree, influences success in all cognitive tasks and thereby creates the positive manifold. This interpretation of ''g'' as a common cause of test performance is still dominant in psychometrics. (Although, an alternative interpretation was recently advanced by van der Maas and colleagues. Their ''mutualism model'' assumes that intelligence depends on several independent mechanisms, none of which influences performance on all cognitive tests. These mechanisms support each other so that efficient operation of one of them makes efficient operation of the others more likely, thereby creating the positive manifold.) IQ tests can be ranked by how highly they load on the ''g'' factor. Tests with high ''g''-loadings are those that correlate highly with most other tests. One comprehensive study investigating the correlations between a large collection of tests and tasks has found that the
Raven's Progressive Matrices Raven's Progressive Matrices (often referred to simply as Raven's Matrices) or RPM is a non-verbal test typically used to measure general human intelligence and abstract reasoning and is regarded as a non-verbal estimate of fluid intelligence. I ...
have a particularly high correlation with most other tests and tasks. The ''Raven's'' is a test of inductive reasoning with abstract visual material. It consists of a series of problems, sorted approximately by increasing difficulty. Each problem presents a 3 x 3 matrix of abstract designs with one empty cell; the matrix is constructed according to a rule, and the person must find out the rule to determine which of 8 alternatives fits into the empty cell. Because of its high correlation with other tests, the Raven's Progressive Matrices are generally acknowledged as a good indicator of general intelligence. This is problematic, however, because there are substantial gender differences on the ''Raven's'', which are not found when ''g'' is measured directly by computing the general factor from a broad collection of tests. Several critics, such as
Stephen Jay Gould Stephen Jay Gould ( ; September 10, 1941 – May 20, 2002) was an American Paleontology, paleontologist, Evolutionary biology, evolutionary biologist, and History of science, historian of science. He was one of the most influential and widely re ...
, have been critical of ''g'', seeing it as a statistical artifact, and that IQ tests instead measure a number of unrelated abilities.''The Mismeasure of Man'', Stephen Jay Gould, Norton, 1996 The 1995 American Psychological Association's report " Intelligence: Knowns and Unknowns" stated that IQ tests do correlate and that the view that ''g'' is a statistical artifact was a minority one.


General collective intelligence factor or ''c''

A recent scientific understanding of collective intelligence, defined as a group's general ability to perform a wide range of tasks, expands the areas of human intelligence research applying similar methods and concepts to groups. Definition, operationalization and methods are similar to the psychometric approach of general individual intelligence where an individual's performance on a given set of cognitive tasks is used to measure intelligence indicated by the general intelligence factor ''g'' extracted via factor analysis. In the same vein, collective intelligence research aims to discover a ''c'' factor' explaining between-group differences in performance as well as structural and group compositional causes for it.


Historical psychometric theories

Several different theories of intelligence have historically been important for
psychometrics Psychometrics is a field of study within psychology concerned with the theory and technique of measurement. Psychometrics generally covers specialized fields within psychology and education devoted to testing, measurement, assessment, and rela ...
. Often they emphasized more factors than a single one like in '' g factor''.


Cattell–Horn–Carroll theory

Many of the broad, recent IQ tests have been greatly influenced by the Cattell–Horn–Carroll theory. It is argued to reflect much of what is known about intelligence from research. A hierarchy of factors for human intelligence is used. ''g'' is at the top. Under it there are 10 broad abilities that in turn are subdivided into 70 narrow abilities. The broad abilities are:IQ Testing 101, Alan S. Kaufman, 2009, Springer Publishing Company, *Fluid intelligence (Gf): includes the broad ability to reason, form concepts, and solve problems using unfamiliar information or novel procedures. *Crystallized intelligence (Gc): includes the breadth and depth of a person's acquired knowledge, the ability to communicate one's knowledge, and the ability to reason using previously learned experiences or procedures. *Quantitative reasoning (Gq): the ability to comprehend quantitative concepts and relationships and to manipulate numerical symbols. *Reading & writing ability (Grw): includes basic reading and writing skills. *Short-term memory (Gsm): is the ability to apprehend and hold information in immediate awareness and then use it within a few seconds. *Long-term storage and retrieval (Glr): is the ability to store information and fluently retrieve it later in the process of thinking. *Visual processing (Gv): is the ability to perceive, analyze, synthesize, and think with visual patterns, including the ability to store and recall visual representations. *Auditory processing (Ga): is the ability to analyze, synthesize, and discriminate auditory stimuli, including the ability to process and discriminate speech sounds that may be presented under distorted conditions. *Processing speed (Gs): is the ability to perform automatic cognitive tasks, particularly when measured under pressure to maintain focused attention. *Decision/reaction time/speed (Gt): reflect the immediacy with which an individual can react to stimuli or a task (typically measured in seconds or fractions of seconds; not to be confused with Gs, which typically is measured in intervals of 2–3 minutes). See
Mental chronometry Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; also referred to as "response time") is measured ...
. Modern tests do not necessarily measure of all of these broad abilities. For example, Gq and Grw may be seen as measures of school achievement and not IQ. Gt may be difficult to measure without special equipment. ''g'' was earlier often subdivided into only Gf and Gc which were thought to correspond to the nonverbal or performance subtests and verbal subtests in earlier versions of the popular Wechsler IQ test. More recent research has shown the situation to be more complex.


Insufficiency of measurement via IQ

A study suggested that intelligence is composed of distinct cognitive systems, each of which having its own capacity and being (to some degree) independent of other components, with the cognitive profile being emergent from anatomically distinct cognitive systems (such as brain regions or neural networks). For example, IQ and reading-/language-related traits/
skill A skill is the learned or innate ability to act with determined results with good execution often within a given amount of time, energy, or both. Skills can often be divided into domain-general and domain-specific skills. Some examples of gen ...
s appear to be influenced "at least partly ydistinct genetic factors". Various types of potential measures related to some definitions of intelligence but not part of IQ measurement include: * Cognitive flexibility – abilities in switching between different concepts, or to adapt behaviour in novel or changing environments * Moral intelligence *
Prioritization Prioritization is the activity that arranges items or activities in order of urgency. In the context of medical evaluation it is the establishment of the importance or the urgency of actions that are necessary to preserve the welfare of clien ...
and goal-selection * Direct measures of brain activity and other neuroimaging intelligence testing – partly investigated in the neuroscience of intelligence


Intelligence across cultures

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 have shown that the definition of human intelligence is unique to the culture that one is studying.
Robert Sternberg Robert J. Sternberg (born December 8, 1949) is an American psychologist and psychometrician. He is a Professor of Human Development at Cornell University. Sternberg has a BA from Yale University and a PhD from Stanford University, under adviso ...
is among the researchers who have discussed how one's culture affects the person's interpretation of intelligence, and he further believes that to define intelligence in only one way without considering different meanings in cultural contexts may cast an investigative and unintentionally egocentric view on the world. To negate this, psychologists offer the following definitions of intelligence: # Successful intelligence is the skills and knowledge needed for success in life, according to one's own definition of success, within one's sociocultural context. # Analytical intelligence is the result of intelligence's components applied to fairly abstract but familiar kinds of problems. # Creative intelligence is the result of intelligence's components applied to relatively novel tasks and situations. # Practical intelligence is the result of intelligence's components applied to experience for purposes of adaption, shaping and selection. Although typically identified by its western definition, multiple studies support the idea that human intelligence carries different meanings across cultures around the world. In many Eastern cultures, intelligence is mainly related with one's social roles and responsibilities. A Chinese conception of intelligence would define it as the ability to empathize with and understand others — although this is by no means the only way that intelligence is defined in
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. In several African communities, intelligence is shown similarly through a social lens. However, rather than through social roles, as in many Eastern cultures, it is exemplified through social responsibilities. For example, in the language of Chi-Chewa, which is spoken by some ten million people across central
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
, the equivalent term for intelligence implies not only cleverness but also the ability to take on responsibility. Furthermore, within American culture there are a variety of interpretations of intelligence present as well. One of the most common views on intelligence within American societies defines it as a combination of problem-solving skills,
deductive reasoning Deductive reasoning is the process of drawing valid inferences. An inference is valid if its conclusion follows logically from its premises, meaning that it is impossible for the premises to be true and the conclusion to be false. For example, t ...
skills, and
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), while other American societies point out that intelligent people should have a
social conscience A social conscience is "a sense of responsibility or concern for the Social issue, problems and Social justice, injustices of society". While our conscience is related to moral conduct in our day-to-day lives with respect to individuals, social c ...
, accept others for who they are, and be able to give advice or
wisdom Wisdom, also known as sapience, is the ability to apply knowledge, experience, and good judgment to navigate life’s complexities. It is often associated with insight, discernment, and ethics in decision-making. Throughout history, wisdom ha ...
.


Motivational intelligence

Motivational intelligence refers to an individual's capacity to comprehend and utilize various motivations, such as the need for achievement, affiliation, or power. It involves understanding tacit knowledge related to these motivations. This concept encompasses the ability to recognize and appreciate the diverse values, behaviors, and cultural differences of others, driven by intrinsic interest rather than solely to enhance interaction effectiveness. Research suggests a relationship between motivational intelligence, international experiences, and leadership. Individuals with higher levels of motivational intelligence tend to exhibit greater enthusiasm for learning about other cultures, thereby contributing to their effectiveness in cross-cultural settings. However, studies have also revealed variations in motivational intelligence across ethnicities, with Asian students demonstrating higher cognitive cultural intelligence but lower motivational intelligence compared to other groups. Investigations have explored the impact of motivational intelligence on job motivation. A study conducted on employees of Isfahan Gas Company indicated a positive and significant relationship between motivational intelligence and two of its indicators, namely adaptability and social relationship, with job motivation. These findings highlight the potential influence of motivational intelligence on individuals' motivation levels within work contexts. Motivational intelligence has been identified as a strong predictor, superseding knowledge intelligence, behavioral intelligence, and strategic intelligence. It holds a crucial role in promoting cooperation, which is considered the ideal and essential element of motivational intelligence. Therapeutic approaches grounded in motivational intelligence emphasize a collaborative partnership between the therapist and client. The therapist creates an environment conducive to change without imposing their views or attempting to force awareness or acceptance of reality onto the client. Motivational intelligence encompasses the understanding of motivations, such as achievement, affiliation, and power, as well as the appreciation of cultural differences and values. It has been found to impact areas such as international experiences, leadership, job motivation, and cooperative therapeutic interventions.


See also

* * * * * * * * * * *


References


Sources

* * * * *


Further reading

* Cattell, Raymond (1987).
Intelligence: Its Structure, Growth and Action.
' New York: North-Holland. * The second edition of a leading textbook on human intelligence, used in highly selective universities throughout the English-speaking world, with extensive references to research literature. * First edition of a comprehensive textbook by a veteran scholar of human intelligence. * Major review article in a flagship publication of the American Psychological Association, a thorough review of current research. ** * Authoritative handbook for graduate students and practitioners, with chapters by a variety of authors on most aspects of human intelligence. {{Virtues
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human Differential psychology