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Revision as of 07:12, 15 December 2004 by Drummond (talk | contribs) (→References)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Intelligence is a general mental capability that involves the ability to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn. In psychology, the study of intelligence is closely related to the study of personality. While the definition and importance of intelligence is an issue of some controversy, especially in the popular press, a consensus opinion exists among intelligence researchers on many issues.
When considering animal intelligence, a more general definition of intelligence might be applied: the "ability to adapt effectively to the environment, either by making a change in oneself or by changing the environment or finding a new one" (Encyclopædia Britannica).
Intelligence tests are often used to quantify human intelligence. This is not without controversy; see below for more information.
Some thinkers have explored the idea of collective intelligence, arising from the coordination of many people. Computer science has developed the field of artificial intelligence, which seeks to make computers act in increasingly intelligent ways. Many people have also speculated about the possibility of extraterrestrial intelligence.
Intelligence tests
Intelligence, narrowly defined, can be measured by intelligence tests (see IQ). They are among the most accurate (reliable and validity (psychometric)) psychological tests, but they are not intended to measure creativity, personality, character, or wisdom. Intelligence tests take many forms, but the common tests (Stanford-Binet, Raven's Progressive Matrices, Wechsler Adult Intelligence Scale (WAIS), Wechsler-Bellevue I, and others) all measure the same intelligence. The general factor measured by intelligence tests is known as g (see g theory).
While the concept of intelligence as a single-factor dominates among experts (Gottfredson 1998), some researchers have proposed that intelligence is not a single quantity or concept, but really consists of a set of relatively independent abilities. Yale psychologist Robert J. Sternberg has proposed a Triarchic Theory of Intelligence. Harvard psychologist Howard Gardner's theory of multiple intelligences, for example, breaks intelligence down into the seven different components: logical, linguistic, spatial, musical, kinesthetic, intra-personal and inter-personal intelligences. Daniel Goleman and several other researchers have developed the concept of emotional intelligence and claim it is at least as important as more traditional sorts of intelligence.
Proponents of multiple-intelligence theories often claim that g is, at best, a measure of academic ability. Other types of intelligence, they claim, might be just as important outside of a school setting. One theory even suggests the existence of two types of g (see Fluid and crystallized intelligence).
In response, g theorists have argued that relevance, and even the existence, of multiple intelligences have not been borne out when actually tested (Hunt 2001), while g has been repeatedly demonstrated to exert a substantial impact on personal affairs.
Practical importance
Intelligence plays an important role many valued life outcomes. In addition to academic success, intelligence correlates with job performance (see below), socioeconomic advancement (e.g., level of education, occupation, and income), and social pathology (e.g., adult criminality, poverty, unemployment, dependence on welfare, children outside of marriage). Recent work has demonstrated links between intelligence and health, longevity, and functional literacy. Correlations between g and life outcomes are pervasive, but interestingly there is no correlation between IQ and happiness. IQ/g correlates highly with school performance and job performance, less so with occupational prestige, moderately with income, and only to a small degree with law-abidingness.
Intelligence or IQ (in the literature typically called "cognitive ability") is the best predictor of job performance by the standard measure, validity. Validity is the correlation between score (in this case cognitive ability, as measured, typically, by a paper-and-pencil test) and outcome (in this case job performance, as measured by a range of factors including supervisor ratings, promotions, training success, and tenure), and ranges between -1.0 (the score is perfectly wrong in predicting outcome) and 1.0 (the score perfectly predicts the outcome). See validity (psychometric). The validity of cognitive ability for job performance tends to increase with job complexity and varies across different studies, ranging from 0.2 for unskilled jobs to 0.8 for the most complex jobs.
A large meta-analysis (Hunter and Hunter, 1984) which pooled validity results across many studies encompassing thousands of workers (32,124 for cognitive ability), reports that the validity of cognitive ability for entry-level jobs is 0.54, larger than any other measure including job tryout (0.44), experience (0.18), interview (0.14), age (-0.01), education (0.10), and biographical inventory (0.37).
Because higher test validity allows more accurate prediction of job performance, companies have a strong incentive to use cognitive ability tests to select and promote employees. Economically, this is the foundation of the practical importance of IQ. The utility of using a one measure over another is proportional to the difference in their validities, all else equal. This is one economic reason why companies use job interviews (validity 0.14) rather than randomly selecting employees (validity 0.0). Legal barriers, most prominently the 1971 United States Supreme Court decision Griggs vs. Duke Power Co., have prevented American employers from directly using cognitive ability tests to select employees, despite their high validity, because different racial groups have different mean scores on tests of cognitive ability (see race and intelligence).
The correlations discussed above are well-established. However, their interpretation is not. Some maintain that cognitive ability/IQ is a product of the privileged classes, used to maintain their privilege. Others maintain that IQ/g is a useful tool in performing life tasks. These two explanations can be distinguished because they make opposite predictions about what would happen if people were given equal opportunities to succeed. The first predicts that equal treatment would destroy the correlations, and the second predicts that it would create them. Several pieces of data can address these predictions. Adoption studies show that by adolescence adopted siblings are no more similar than strangers, and the gap between full siblings is 2/3 of that size. Conversely, monozygotic twins raised separately are highly similar, more so than dizygotic twins raised together. According to some studies the heritability of IQ increases with age, such that differences in family advantage are lost by adolescence.
Controversies
Researchers in the field of human intelligence have encountered a considerable amount of public concern and criticism; much more than many scientists would be accustomed to or comfortable with. Some of the controversial topics include:
- the relevance of psychometric intelligence to the common sense understanding of the topic
- the importance of intelligence in everyday life
- the genetic and environmental contributions to individual variation in intelligence (see Nature versus nurture).
- differences in average measured intelligence between racial groups and sexes; and the source and meaning of these differences (see Race and intelligence).
References
- Gottfredson, L.S. (1998). The general intelligence factor. Scientific American Presents, 9(4):24-29. PDF
- Hunt, E. (2001). Multiple views of multiple intelligence. Contemporary Psychology, 46:5-7.
- Hunter, J.E. and Hunter, R.F. (1984). Validity and utility of alternate predictors of job performance. Psychological Bulletin, 96(1):72-98.