Copyright © 1999 Massachusetts Institute of Technology
Intelligence may be defined as the ability to adapt to, shape, and select environments, although over the years many definitions of intelligence have been offered (e.g., see symposia in Journal of Educational Psychology 1921; Sternberg and Detterman 1986). Various approaches have been proposed in attempts to understand it (see Sternberg 1990). The emphasis here will be on cognitive-scientific approaches.
Historically, two major competing approaches to understanding intelligence were offered, respectively, by Sir Francis Galton in England and Alfred Binet in France. Galton (1883) sought to understand (and measure) intelligence in terms of psychophysical skills, such as an individual's just noticeable difference (JND) for discriminating weights or the distance on the skin two points needed to be separated in order for them to be felt as having occurred in distinct locations. Binet and Simon (1916), in contrast, conceptualized intelligence in terms of complex judgmental abilities. Binet believed that three cognitive abilities are key to intelligence: (1) direction (knowing what has to be done and how it should be done), (2) adaptation (selection and monitoring of one's strategies for task performance), and (3) control (the ability to criticize one's own thoughts and judgments). The "metacognitive" emphasis in this conception is apparent. Binet's views have had more impact, both because his theory seemed better to capture intuitive notions of intelligence and because Binet devised a test of intelligence that successfully predicted children's performance in school.
Charles Spearman (1923) was a forerunner of contemporary cognitive approaches to intelligence in suggesting three information processes underlying intelligence: (1) apprehension of experience, (2) eduction of relations, and (3) eduction of correlates. Spearman used the four-term ANALOGY problem (A : B :: C : D) as a basis for illustrating these processes, whereby the first process involved encoding the terms; the second, inferring the relation between A and B; and the third, applying that relation from C to D.
The early part of the twentieth century was dominated by psychometric approaches to intelligence, which emphasized the measurement of individual differences but had relatively less to say about the cognitive processing underlying intelligence (see Sternberg 1990 for a review). These approaches for the most part used factor analysis, a statistical technique for discovering possible structures underlying correlational data. For example, Spearman (1927) believed that a single factor, g (general ability), captured most of what is important about intelligence, whereas Thurstone (1938) believed in a need for seven primary factors. More recently, Carroll (1993) has proposed a three-tier hierarchical model that is psychometrically derived, but is expressed in information-processing terms, with g at the top and successively more narrow cognitive skills at each lower level of the hierarchy.
A change in the field occurred when Estes (1970) and Hunt, Frost, and Lunneborg (1973) proposed what has come to be called the cognitive-correlates approach to intelligence, whereby relatively simple information-processing tasks used in the laboratories of cognitive psychologists were related to scores on conventional psychometric tests of intelligence. Hunt and his colleagues found correlations of roughly - .3 between parameters of rate of information processing in tasks such as a letter-identification task (Posner and Mitchell 1967) -- where participants had to say whether letter pairs like A A, A a, or A b were the same either physically or in name -- and scores on psychometric tests of verbal abilities. This approach continues actively today, with investigators proposing new tasks that they believe to be key to intelligence, such as the inspection time task, whereby individuals are assessed psychophysically for the time it takes them accurately to discern which of two lines is longer than the other (e.g., Deary and Stough 1996).
An alternative, cognitive-components approach was proposed by Sternberg (1977), who suggested that intelligence could be understood in terms of the information-processing components underlying complex reasoning and problem-solving tasks such as analogies and syllogisms. Sternberg used information-processing and mathematical modeling to decompose cognitive task performance into its elementary components and strategies. Some theorists, such as Hunt (1974) and Carpenter, Just, and Shell (1990), have used computer-simulation methodology in order to identify such components and strategies in complex tasks, such as the Raven progressive matrices.
Building on his earlier work, Sternberg (1985) proposed a triarchic theory of intelligence, according to which these information-processing components are applied to experience to adapt to, shape, and select environments. Intelligence is best understood in terms of performance on either relatively novel cognitive tasks or in terms of automatization of performance on familiar tasks. Sternberg argued that intelligence comprises three major aspects: analytical, creative, and practical thinking.
Howard Gardner (1983, 1995), in contrast, has suggested that intelligence is not unitary, but rather comprises eight distinct multiple intelligences: linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalist. Each of these intelligences is a distinct module in the brain and operates more or less independently of the others. Gardner has offered a variety of kinds of evidence to support his theory -- including cognitive-scientific research -- although he has not conducted research directly to test his model.
Other theorists have tried directly to link information processing to physiological processes in the brain. For example, Haier and his colleagues (Haier et al. 1988; Haier et al. 1992) have shown via POSITRON EMISSION TOMOGRAPHY (PET) scans that brains of intelligent individuals generally consume less glucose in doing complex tasks such as Raven matrices or the game of TETRIS , suggesting that the greater expertise of intelligent people enables them to expend less effort on the tasks. Vernon and Mori (1992), among others, have attempted directly to link measured speed of neural conduction to intelligence, although there is some question as to the replicability of the findings (Wickett and Vernon 1994).
The field of intelligence has many applied offshoots. For example, a number of cognitive tests have been proposed to measure intelligence (see Sternberg 1993), and a number of different programs have been developed, based on cognitive theory, to modify intelligence (see Nickerson 1994). Some investigators have also argued that there are various kinds of intelligence, such as practical intelligence (Sternberg et al. 1995) and emotional intelligence (Goleman 1995; Salovey and Mayer 1990). The field is an active one today, and it promises to change rapidly as new theories are proposed and new data collected. The goal is not to choose among alternative paradigms, but rather for them to work together ultimately to help us produce a unified understanding of intellectual phenomena.
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Copyright © 1999 Massachusetts Institute of Technology