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Human intelligence is the
intellect In the study of the human mind, intellect refers to, describes, and identifies the ability of the human mind to reach correct conclusions about what is true and what is false in reality; and how to solve problems. Derived from the Ancient Gre ...
ual capability of humans, which is marked by complex
cognitive Cognition refers to "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 the reason for which humans and other animals initiate, continue, or terminate a behavior at a given time. Motivational states are commonly understood as forces acting within the agent that create a disposition to engage in goal-dire ...
and
self-awareness In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifest ...
. High intelligence is associated with better outcomes in life. Through
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. More generally, it can ...
, humans possess the
cognitive Cognition refers to "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 ...
abilities to
learn Learning is the process of acquiring new understanding, knowledge, behaviors, skills, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of l ...
, form concepts,
understand Understanding is a psychological process related to an abstract or physical object, such as a person, situation, or message whereby one is able to use concepts to model that object. Understanding is a relation between the knower and an object of ...
, apply
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from prem ...
and
reason Reason is the capacity of consciously applying logic by drawing conclusions from new or existing information, with the aim of seeking the truth. It is closely associated with such characteristically human activities as philosophy, science, lang ...
, including the 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 objective to do something. It is commonly understood as a temporal set of intended actions through which one expects to achieve a goal. ...
,
innovate Innovation is the practical implementation of ideas that result in the introduction of new goods or services or improvement in offering goods or services. ISO TC 279 in the standard ISO 56000:2020 defines innovation as "a new or changed entity ...
, solve problems, make decisions, retain information, and use
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...
to
communicate Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inqu ...
. There are conflicting ideas about how intelligence is measured, ranging from the idea that intelligence is fixed upon birth, or that it is malleable and can change depending on an individual's mindset and efforts. Several subcategories of intelligence, such as emotional intelligence or social intelligence, are heavily debated as to whether they are traditional forms of intelligence. They are generally thought to be distinct processes that occur, though there is speculation that they tie into traditional intelligence more than previously suspected.


History


Correlates

As a construct and measured by intelligence tests, intelligence is considered to be one of the most useful concepts in
psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic discipline of immens ...
, because it correlates with many relevant variables, for instance the probability of suffering an accident, salary, and more. ; Education: According to a 2018
metastudy A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
of educational effects on intelligence, education appears to be the "most consistent, robust, and durable method" known for raising intelligence. ; Myopia: A number of studies have shown a correlation between IQ and
myopia Near-sightedness, also known as myopia and short-sightedness, is an eye disease where light focuses in front of, instead of on, the retina. As a result, distant objects appear blurry while close objects appear normal. Other symptoms may includ ...
. Some suggest that the reason for the correlation is environmental, whereby people with a higher IQ are more likely to damage their eyesight with prolonged reading, or the other way around whereby people who read more are more likely to reach a higher IQ, while 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 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 polymorphisms in human DNA are correlated with intelligence. ; Motivation: Motivation is a factor that influences the results of the IQ test. People with higher motivation tend to obtain higher IQ scores.


Theories


Relevance of IQ tests

In
psychology Psychology is the science, scientific study of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, including feelings and thoughts. It is an academic discipline of immens ...
, human intelligence is commonly assessed by IQ scores that are determined by IQ tests. However, while IQ test scores show a high degree of inter-test reliability, and predict certain forms of achievement rather 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 Beck ...
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 a phenomenon whereby something new and valuable is formed. The created item may be intangible (such as an idea, a scientific theory, a musical composition, or a joke) or a physical object (such as an invention, a printed lit ...
and
social intelligence Social intelligence is the capacity to know oneself and to know others. Social intelligence is learned and develops from experience with people and learning from success and failures in social settings. Social intelligence is the ability to underst ...
. 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's theory of multiple intelligences is based on studies not only of normal children and adults, but also of gifted individuals (including so-called "
savant Savant syndrome () is a rare condition in which someone with significant mental disabilities demonstrates certain abilities far in excess of average. The skills that savants excel at are generally related to memory. This may include rapid calc ...
s"), of persons who have suffered brain damage, of experts and
virtuoso A virtuoso (from Italian ''virtuoso'' or , "virtuous", 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 a ...
s, and of individuals from diverse cultures. Gardner breaks intelligence down into at least a number of different 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 human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Linguis ...
, spatial, musical,
kinesthetic Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense". Proprioception is mediated by proprioceptors, mechanosensory neurons ...
,
interpersonal The concept of interpersonal relationship involves social associations, connections, or affiliations between two or more people. Interpersonal relationships vary in their degree of intimacy or self-disclosure, but also in their duration, in t ...
, and intrapersonal. In a second edition of this book, 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 refers to specialized fields within psychology and education devoted to testing, measurement, assessment, and ...
(IQ) tests address only linguistic and logical plus some aspects of spatial intelligence. Article in Wikipedia: Intelligence: Knowns and Unknowns A major 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 is a standard of evaluation of scientific theories and hypotheses that was introduced by the Philosophy of science, philosopher of science Karl Popper in his book ''The Logic of Scientific Discovery'' (1934). He proposed it as t ...
. Others (e.g. Locke, 2005) have suggested 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 (2004) 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 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 Professor of Human Development at Cornell University. Sternberg has a BA from Yale University and a PhD from Stanford University, under advisor ...
proposed the
triarchic theory of intelligence The Triarchic Theory of Intelligence or Three Forms of Intelligence, formulated by psychometrician Robert Sternberg, aims to go against the psychometric approach to intelligence and take a more cognitive approach, which leaves it to the category ...
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 in 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 fully understood. More recently, the triarchic theory has been updated and renamed as the Theory of Successful Intelligence by Sternberg. Intelligence is now defined 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 Alexander Romanovich Luria (russian: Алекса́ндр Рома́нович Лу́рия, p=ˈlurʲɪjə; 16 July 1902 – 14 August 1977) was a Soviet neuropsychologist, often credited as a father of modern neuropsychology. He develope ...
's (1966)Luria, A. R. (1966). Higher cortical functions in man. New York: Basic Books. seminal work on the modularization of brain function, and supported by decades of neuroimaging research, the PASS Theory of IntelligenceDas, J. P., Naglieri, J. A., & Kirby, J. R. (1994). Assessment of cognitive processes. Needham Heights, MA: Allyn & Bacon. (Planning/Attention/Simultaneous/Successive) proposes that cognition is organized in three systems and four processes. The first process is the Planning, which involves executive functions responsible for controlling and organizing behavior, selecting and constructing strategies, and monitoring performance. The second is the Attention process, which is responsible for maintaining arousal levels and alertness, and ensuring focus on relevant stimuli. The next two are called Simultaneous and Successive processing and they involve encoding, transforming, and retaining information. 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 to both Luria (1966, 1973Luria, A. R. (1973). The working brain: An introduction to neuropsychology. New York.), and 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 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 theory deals with the nature of ...
the focus is not on mental abilities but rather on a child's mental models of the world. As a child develops, increasingly more accurate models of the world are developed which enable the child to interact with the world better. One example being object permanence where the child develops a model where 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-2yrs); * pre-operational stage (2yrs-7rs); * concrete operational stage (7rs-11yrs); and * formal operations stage (11yrs-16yrs)Piaget, J. (2001). Psychology of intelligence. Routledge. Degree of progress through these stages are correlated, but not identical with psychometric IQ.Elkind, D., & Flavell, J. (1969). ''Studies in cognitive development: Essays in honor of Jean Piaget''. New York: Oxford University Press Piaget conceptualizes intelligence as an activity more than 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. By the end of this experiment several results were found. First, younger children have a discriminative ability that shows the logical capacity for cognitive operations exists earlier than acknowledged. This study also reveals that 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 5 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 for the age of appearance of a new model of the world, such as object permanence, being dependent on how the testing is done (see the article on object permanence). 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 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 structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incr ...
studies, Jung and Haier (2007) proposed that the biological basis of intelligence stems from how well the
frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
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 Cattell–Horn–Carroll theory (commonly abbreviated to CHC), is a psychological theory on the structure of human cognitive abilities. Based on the work of three psychologists, Raymond B. Cattell, John L. Horn and John B. Carroll, the Catte ...
, the tests of intelligence most often used in the relevant studies include measures of fluid ability (Gf) and crystallized ability (Gc); that differ in their trajectory of development in individuals. 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. This is a discipline that develops classifications (taxonomies) of psychological individual differences. This is distingui ...
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. It is essential to highlight that the investment theory suggests that personality traits affect 'actual' ability, and not scores on an IQ test. In association, 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 (a term first coined by Wood and Englert, 2009) states that individuals who are comparatively less intelligent work harder, more methodically, 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 careful, or diligent. Conscientiousness implies a desire to do a task well, and to take obligations to others seriously. Conscientious people tend to be efficient and organized as opposed 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 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. The justification being 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''. Thus, attributing the previous findings to the bias in selecting samples with individuals 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 it is no longer viewed as a fixed property held by an individual. Instead, the current perspective describes it as a general capacity, 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. The link between intelligence and success has been bridged 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. Self-efficacy affects every area of human end ...
. Bandura's theory identifies the difference between possessing skills and being able to apply them in challenging situations. Thus, 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 stimuli that is unclear and ambiguous. To learn the relevant concepts, individuals must be able to rely on the 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. To summarize, 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 it to an insufficient aptitude. On the other hand, persons with high levels of self-efficacy hold a task-diagnostic aim 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 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, P.L. (1995, August). Personality, intelligence, motivation, and interests: Implications for overlapping traits. Address presented at the annual meeting of the American Psychological Association, New York. Ackerman describes the difficulty of distinguishing process from knowledge, as content cannot be eliminated from any ability test. Personality traits have not shown to be 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 Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most anim ...
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 Latent inhibition (LI) is a technical term in classical conditioning, where a familiar stimulus takes longer to acquire meaning (as a signal or conditioned stimulus) than a new stimulus. The term originated with Lubow and Moore in 1973. The LI ef ...
, the phenomenon of familiar stimuli having a postponed reaction time than unfamiliar stimuli has a positive correlation with
creativity Creativity is a phenomenon whereby something new and valuable is formed. The created item may be intangible (such as an idea, a scientific theory, a musical composition, or a joke) or a physical object (such as an invention, a printed lit ...
.


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 technologies used to change the genetic makeup of cells, including ...
could be used to enhance the intelligence, a process sometimes called
biological uplift In science fiction, uplift is a developmental process to transform a certain species of animals into more intelligent beings by other, already-intelligent beings. This is usually accomplished by cultural, technological, or evolutional intervention ...
in
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...
. Experiments on mice have demonstrated superior ability in learning and memory in various behavioral tasks.


Child care

A 2021 study showed that the Abecedarian Early Intervention Project resulted in significant changes in midlife brain structure in males. MRI scans showed that several brain region and total brain volumes were substantially larger in participants of the child care program than in
the control group The Control Group is an independent record label, founded by Nabil Ayers in Seattle, Washington in 2002. Notable artists who have released albums on The Control Group include El Perro del Mar, Lykke Li, Cate Le Bon, Alice Boman and Wildbird ...
.


Education

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 ) (colloquial: smart drugs and cognitive enhancers, similar to adaptogens) are a wide range of natural or synthetic dietary supplement, supplements or drugs and other substances that are claimed to improve cognitive function ...
s. A meta analysis shows omega 3 fatty acids improves 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 mental 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 animal t ...
* Quality of
sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited Perception, sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefuln ...


Digital tools


Digital media


Brain training

Attempts to raise IQ with
brain training Brain training (also called cognitive training) is a program of regular activities purported to maintain or improve one's cognitive abilities. The phrase “cognitive ability” usually refers to components of fluid intelligence such as executive ...
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 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 memory, ...
– 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'' (stylized as ''WIRED'') is a monthly American magazine, published in print and online editions, that focuses on how emerging technologies affect culture, the economy, and politics. Owned by Condé Nast, it is headquartered in San ...
''. 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 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. It ...
(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

On the philosophical front, conscious 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 el, νεῦρον (neûron), "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 brain, the spinal c ...
disease and enhancing the human brain, and how wealth impacts access to
neurotechnology Neurotechnology encompasses any method or electronic device which interfaces with the nervous system to monitor or modulate neural activity. Common design goals for neurotechnologies include using neural activity readings to control external devi ...
. 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 which advocates the enhancement of the human condition by developing and making widely available sophisticated technologies that can greatly enhance longevity and cognition. Transhuma ...
theorists study the possibilities and consequences of developing and using techniques to enhance human abilities and aptitudes.
Eugenics Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior o ...
is a social philosophy which 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 (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...
in
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
.


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 refers to specialized fields within psychology and education devoted to testing, measurement, assessment, and ...
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. The abbreviation "IQ" was coined by the psychologist William Stern for the German term ''Intelligen ...
(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. It ...
, 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. The original WAIS (Form I) was published in February 1955 by David Wechsler, as a revision of the ...
and the
Kaufman Assessment Battery for Children The Kaufman Assessment Battery for Children (KABC) is a clinical instrument (psychological diagnostic test) for assessing cognitive development. Its construction incorporates several recent developments in both psychological theory and statistical ...
. 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 ACT, the GRE, the MCAT, the
LSAT The Law School Admission Test (LSAT; ) is a standardized test administered by the Law School Admission Council (LSAC) for prospective law school candidates. It is designed to assess reading comprehension as well as logical and verbal rea ...
, and the GMAT. 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 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 mediums and sources. It excludes specialized learning that can only be obtained with extensive training and information confined to a single medium. General kn ...
). 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 observed ...
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 statistic ...
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 The ''g'' factor (also known as general intelligence, general mental ability or general intelligence factor) is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarize ...
". 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. It ...
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.


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 refers to specialized fields within psychology and education devoted to testing, measurement, assessment, and ...
. 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 The Cattell–Horn–Carroll theory (commonly abbreviated to CHC), is a psychological theory on the structure of human cognitive abilities. Based on the work of three psychologists, Raymond B. Cattell, John L. Horn and John B. Carroll, the Catte ...
. 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; sometimes referred to as "response time") is meas ...
. 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.


Controversies

While not necessarily a dispute about the psychometric approach itself, there are several controversies regarding the results from psychometric research. One criticism has been against the early research such as
craniometry Craniometry is measurement of the cranium (the main part of the skull), usually the human cranium. It is a subset of cephalometry, measurement of the head, which in humans is a subset of anthropometry, measurement of the human body. It is dis ...
.''The Mismeasure of Man'', Stephen Jay Gould, Norton, 1996 A reply has been that drawing conclusions from early intelligence research is like condemning the auto industry by criticizing the performance of the
Model T The Ford Model T is an automobile that was produced by Ford Motor Company from October 1, 1908, to May 26, 1927. It is generally regarded as the first affordable automobile, which made car travel available to middle-class Americans. The relati ...
. Several critics, such as
Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Goul ...
, have been critical of ''g'', seeing it as a statistical artifact, and that IQ tests instead measure a number of unrelated abilities. The 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 is a minority one.


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 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. For example, in the domain of w ...
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 Cognitive flexibility is an intrinsic property of a cognitive system often associated with the mental ability to adjust its activity and content, switch between different task rules and corresponding behavioral responses, maintain multiple con ...
– 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 importance relative to each other. In the context of medical evaluation it is the establishment of the importance or the urgency of actions that are necessary to prese ...
and goal-selection * Direct measures of brain activity and other
neuroimaging intelligence testing Neuroimaging intelligence testing concerns the use of neuroimaging techniques to evaluate human intelligence. Neuroimaging technology has advanced such that scientists hope to use neuroimaging increasingly for investigations of brain function relat ...
– partly investigated in the neuroscience of intelligence


Non-human intelligence

Human intelligence could be distinguished from potential other types of intelligences which may include those of (some may belong to multiple or be impossible): * Extraterrestrials *
Non-human animals Personhood or personality is the status of being a person. Defining personhood is a controversial topic in philosophy and law and is closely tied with legal and political concepts of citizenship, equality, and liberty. According to law, only a l ...
(such as that of bonobos and chimpanzees) *
Artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech ...
s (including novel types of learning machines such as semi-synthetic
wetware computer A wetware computer is an organic computer (which can also be known as an artificial organic brain or a neurocomputer) composed of organic material " wetware" such as "living" neurons. Wetware computers composed of neurons are different than conve ...
s or digitized minds) * Chimerics (or hybrids) created with the use of biotechnologies (including
humanzee The humanzee (sometimes chuman, manpanzee or chumanzee) is a hypothetical hybrid of chimpanzee and human, thus a form of human–animal hybrid. Serious attempts to create such a hybrid were made by Soviet biologist Ilya Ivanovich Ivanov in the 1 ...
s,
humanized mice A humanized mouse is a mouse carrying functioning human genes, cells, tissues, and/or organs. Humanized mice are commonly used as small animal models in biological and medical research for human therapeutics. A humanized mouse or a humanized mouse ...
or rats with human brain cells/organoids) * Future
posthuman Posthuman or post-human is a concept originating in the fields of science fiction, futurology, contemporary art, and philosophy that means a person or entity that exists in a state beyond being human. The concept aims at addressing a variety of ...
s (e.g.
cyborg A cyborg ()—a portmanteau of ''cybernetic'' and ''organism''—is a being with both organic and biomechatronic body parts. The term was coined in 1960 by Manfred Clynes and Nathan S. Kline.
s including cyborgs with biological augmentations) *
Archaic humans A number of varieties of '' Homo'' are grouped into the broad category of archaic humans in the period that precedes and is contemporary to the emergence of the earliest early modern humans (''Homo sapiens'') around 300 ka. Omo-Kibish I (Omo I) f ...
(including
Neanderthals Neanderthals (, also ''Homo neanderthalensis'' and erroneously ''Homo sapiens neanderthalensis''), also written as Neandertals, are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While ...
– see also: genetic factors of recent brain evolution) Such intelligences, if they exist and are considered "intelligent", could be very different from human intelligences. Research may e.g. investigate differences between different types or profiles or aspects of intelligences, such as between modern humans and archaic humans.


Intelligence across cultures

Psychologist A psychologist is a professional who practices psychology and studies mental states, perceptual Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the pre ...
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 Professor of Human Development at Cornell University. Sternberg has a BA from Yale University and a PhD from Stanford University, under advisor ...
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. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
. 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 in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, 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 mental process of drawing deductive inferences. An inference is deductively valid if its conclusion follows logically from its premises, i.e. if it is impossible for the premises to be true and the conclusion to be fal ...
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. The abbreviation "IQ" was coined by the psychologist William Stern for the German term ''Intelligen ...
(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 problems and injustices of society". While our conscience is related to moral conduct in our day-to-day lives with respect to individuals, social conscience is concerned with th ...
, accept others for who they are, and be able to give advice or
wisdom Wisdom, sapience, or sagacity is the ability to contemplate and act using knowledge, experience, understanding, common sense and insight. Wisdom is associated with attributes such as unbiased judgment, compassion, experiential self-knowledg ...
.''Intelligence and Culture'', Robert Serpell, Handbook of Intelligence, Cambridge University Press, 2000, pp. 549-578.


See also

* Evolution of human intelligence *
Flynn effect The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially stand ...
*
Genius Genius is a characteristic of original and exceptional insight in the performance of some art or endeavor that surpasses expectations, sets new standards for future works, establishes better methods of operation, or remains outside the capabili ...
*
Intellect In the study of the human mind, intellect refers to, describes, and identifies the ability of the human mind to reach correct conclusions about what is true and what is false in reality; and how to solve problems. Derived from the Ancient Gre ...
* Neuroscience and intelligence § Humans * Outline of human intelligence * Self-test of Intelligence *
Sex differences in intelligence Sex differences in human intelligence have long been a topic of debate among researchers and scholars. Most psychologists now believe that there are no significant sex differences in general intelligence, although ability in particular types of ...
*
Superintelligence A superintelligence is a hypothetical agent that possesses intelligence far surpassing that of the brightest and most gifted human minds. "Superintelligence" may also refer to a property of problem-solving systems (e.g., superintelligent languag ...
* Theory of multiple intelligences *
Volition (psychology) Volition or will is the cognitive process by which an individual decides on and commits to a particular course of action. It is defined as purposive striving and is one of the primary human psychological functions. Others include affect (feelin ...


References


Sources

* * * * *


Further reading

* 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. {{Psychology Intelligence Brain