Intelligence Research Paper

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Abstract

For centuries, persons making significant contributions to science, industry, art, politics, or even criminal pursuits were viewed as intelligent, whereas those who failed in school, at work, or as a member of society were thought to represent the lower end of the ability distribution. The ancient Chinese as well as the ancient Greeks recognized the importance of individual differences in ability for the selection of soldiers and civil servants. As part of modern Western culture, children and adults routinely test their abilities (intelligence) against peers via school grades, extracurricular activities (e.g., debate clubs), games of skill (e.g., chess), and even party games (e.g., Trivial Pursuit) and television shows (e.g., Jeopardy). Although the subjective assessment of intelligence has been going on since the dawn of civilization and will continue in perpetuity, the formal measurement of the construct dates to the latter part of the 19th century. This research paper addresses the topic of human intelligence by expounding on its history, contemporary explanatory theories, controversial issues, practical applications, and future trends in the field.

History

From the time of Aristotle, philosophers and academics have debated and discussed the construct of human intelligence. The ancient Greeks and Chinese, for example, were interested in identifying highly “intelligent” individuals who could learn quickly, benefit from formal education, and function successfully within complex social and military systems. Around 2200 BCE, Chinese emperors were actually using competitive written civil service examinations to select employees for their government bureaucracies. Although attempts to identify differences in ability among people have been taking place for thousands of years, the scientific study of intelligence is a relatively recent event, one that began in the latter part of the 1800s.

Sir Frances Galton, a British scientist and scholar, believed intelligence was mainly inherited and that the human race could be improved by selectively breeding the healthiest, brightest, and most physically capable individuals. In order to identify the “best” people, he established the first anthropometric laboratory in 1884. Galton assumed that he could use tests of physical and sensory ability to measure intelligence. He reasoned that if information about the world comes to us via sensory processes, then more intellectually capable persons will perform better than less capable people on separate tasks of reaction time, strength of movement, visual discrimination, kinesthetic discrimination, and auditory discrimination.

James McKeen Cattell, who earned his PhD at the University of Leipzig under Wilhelm Wundt in 1886, shared Galton’s interest in identifying individual differences using sensory-motor tasks, which he believed measured intellectual functions. After completing postdoctoral studies under Galton, he returned to the United States in 1888 as professor of psychology at the University of Pennsylvania. He immediately founded a psychological laboratory at Penn, began collecting sensory-motor data on healthy volunteers, and coined the term “mental tests” to describe his procedures. In 1891 he moved to Columbia University and, in addition to assuming administrative duties as the department head, continued collecting sensory-motor information on entering freshmen for almost a decade. One of Cattell’s graduate students, Clark Wissler, designed his dissertation research to test the hypothesis that sensory-motor tests are valid measures of intellectual ability. Using college student data, Wissler reported that Cattell’s sensory-motor tests did not correlate meaningfully with one another, nor did they show significant associations with academic performance. Conversely, academic grades in various subjects (e.g., Latin and mathematics) produced significant intercorrelations. These findings suggested that Cattell’s tests lacked validity as measures of intelligence and, in the opinion of some writers (Sokal, 1987), served as the terminal blow to the viability of the anthropometric testing movement.

At the dawn of the 20th century, policies requiring compulsory school attendance for all children were instituted in Western Europe and the United States. To help the Parisian public schools comply with the directive, Alfred Binet and his colleague Theodore Simon were recruited by the French government to develop quantitative techniques for the assessment of school-age children. Unlike Galton and Cattell, who thought that sensory-motor tasks measured intelligence, Binet was convinced that accurate assessment required items tapping higher mental processes (e.g., abstraction, memory, and novel problem solving) in addition to those that measure sensory-motor functions. In 1905 Binet and Simon published a 30-item age-scale that allowed one to determine if an examinee was functioning below, at, or above the level of the average child of the same chronological age. Sattler (2001) describes the 1905 scale as the first practical intelligence test because it provided instructions for administration and was composed of items that were arranged according to difficulty levels. For example, to pass the first item the child followed a light with his eyes, whereas the last question required the examinee to distinguish between the concepts of “sad” and “bored.” The original scale was revised and expanded in 1908 (which introduced the concept of mental age, or MA) and again in 1911. The scales were interpreted as follows: mental age < 2 = idiot, 2 to 7 years = imbecile, and > 8 years = moron (Watson, 1963). Henry H. Goddard translated the 1905 and 1908 editions into English and standardized the latter using 2,000 American children. To insure that interpretation of mental age simultaneously considered the examinee’s chronological age, William Stern introduced the concept of the mental quotient in 1912 (Sattler, 2001). This value is calculated by dividing MA by chronological age (CA) to reflect overall intelligence. For example, a seven-year-old child with an MA of nine has a mental quotient of 1.28.

Perhaps one of the most important contributions to the field of mental testing occurred when Lewis Terman, a professor at Stanford University, published the 1916 Stanford Revision of the Binet-Simon scale. Terman expanded upon Binet’s ideas, developed new test items, collected normative data on 1,400 children and adults living in California, and converted the mental quotient to an intelligence quotient or IQ (mental age – chronological x 100). Terman also devised a system for classifying intelligence in terms of IQ. On the American version of the scale, the previously mentioned seven-year-old child with an MA of nine years would have an IQ of 128 (MA/CA x 100), a value falling within the superior range of intellectual functioning. The 1916 revision, which was popularly known as the Stanford-Binet Intelligence Scale, quickly became the standard for intelligence assessment throughout the United States. Although researchers have revised and modified the scale numerous times (1937, 1960, 1972, 1986, and 2003), its popularity began declining in the 1940s and 1950s because of serious limitations when used to evaluate adolescents and adults with a variety of psychiatric or neurological conditions.

David Wechsler (1939) was one of many psychological practitioners who recognized that the Stanford-Binet was unsuitable in a variety of clinical situations. For example, the scale was designed for children and lacked face validity with older examinees. There were also problems with an overemphasis on verbal ability and utilization of the MA construct for calculating IQs. The latter concern was due to the underlying assumption of the 1916 Stanford-Binet that MA ceased to increase after 16 years of age (Kaplan & Saccuzzo, 1997). Thus, an examinee who takes the test with a CA of 16 years and earns an MA of 16 years receives an IQ of 100 (16 – 16 x 100 = 100). However, if the examinee is retested two years later and obtains the same MA, the resulting IQ will show a marked and clearly misleading decline (16 – 18 x 100 = 89). To control for this problem, the highest CA that could be used in calculating IQ values on the 1916 scale was 16 years. Although the 1937 revision of the Stanford-Binet was a much-improved instrument, suitability of the scale for use with adults and problems with reliance on the MA for derivation of ratio IQs remained. It is also noted that the standardization sample for the 1937 revision included only examinees in the age range 18 months to 18 years.

As chief psychologist at Bellevue Hospital in New City, Wechsler was acutely aware of the need for an intelligence measure that corrected the problems associated with the Stanford Binet. Drawing on his extensive background and knowledge of the World War I military testing program, everyday clinical assessment, and the scientific literature, he was able to organize a number of previously published and well-known tests into a composite instrument. His new test, which was called the Wechsler-Bellevue Intelligence Scale-Form I (W-B I; Wechsler, 1939), contains 10 standard subtests and one supplementary subtest that yield separate Verbal Scale and Performance Scale

IQs as well as a global intelligence estimate called the Full Scale IQ. The W-B I is a point scale that groups test items according to content, whereas the first seven editions of the Binet scales grouped items by age level, regardless of content. To solve the problems associated with the MA and ratio IQ, Wechsler eliminated the former concept entirely and replaced the ratio IQ with the deviation IQ. On the W-B I and subsequent editions of the scale, the deviation IQ involves transforming raw scores to standard scores with a designated mean of 100 and standard deviation of 15. The W-B I standardization sample consisted of 1750 males and females, with raw score-to-IQ conversion tables covering the age ranges 10 years to 59 years on the Verbal and Full Scales and 10 years to 49 years on the Performance Scale.

In the United States, the W-B I rapidly became the preferred instrument for assessing adolescent and adult intelligence. The scale was revised and expanded in 1946, 1955, 1981, and 1997, with the latest edition being designated the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997). The constant process of scale revision also produced a series of tests for children in the age range 6 years to 16 years, including the Wechsler Intelligence Scale for Children (WISC; Wechsler, 1949), WISC-R, WISC-III, and WISC-IV. For younger children there is the Wechsler Preschool and Primary Scale of Intelligence (Wechsler, 1967) and its newer derivatives, the WPPSI-R and the WPPSI-III. Recent surveys have demonstrated that in the United States the Wechsler Scales are, for all practical purposes, the most frequently used tests of intelligence for children and adults (Rabin, Bar, & Burton, 2005).

Theories Of Intelligence

The activities just described took place in the absence of a generally accepted definition or theory of intelligence. Although a number of symposia and conferences were held over the years to resolve this situation, to date a consensus has not been achieved. Thus, the following discussion covers four theories of intelligence that this writer feels have the most adherents and would be of interest to the present readership.

Charles E. Spearman (1923) proposed the two-factor theory of intelligence. It is based on the observation that persons who excel on one type of intellectual task (e.g., mathematics) tend also to perform well on others (e.g., defining words). Spearman noted that when individuals were given ability tests tapping a variety of content (e.g., numerical problems and visual spatial designs), the resulting test scores consistently yielded positive intercorrelations. According to the theory, a general factor “g” reflects the component that is shared with all conceivable measures of intellectual functioning, and a specific factor “s” represents the unique component of each test. The two-factor theory provides a reasonable foundation for the measurement of intelligence with tests such as the Binet and Wechsler because they provide an aggregate or composite MA and/ or IQ score that is based on items and subtests of diverse manifest content.

Today some experts consider “g” to be a variable accounting for differences in IQ scores across individuals, with each person occupying one of the levels of ” g” (Borsboom & Dolan, 2006). High “g” individuals demonstrate a plethora of generic abilities, including efficient and rapid learning and good reasoning, problem-solving, and conceptual skills. However, IQ scores are not pure measures of ” g” as evidenced by the fact that the construct accounts for only 50 percent of the variance in the WAIS-III Full Scale IQ (Sattler & Ryan, 2001). Nevertheless, when the IQ is used as a measure of general intelligence it proves to be a highly practical piece of information for predicting favorable outcomes such as job performance, educational attainment, socioeconomic status, and longevity (Gottfredson & Deary, 2004). General intelligence as reflected in IQ scores also predicts unfavorable outcomes, including poverty, welfare use, incarceration, and cause of death (Gottfredson, 2002).

Raymond B. Cattell (1963) postulated that Spearmen’s ” g” could be divided into two separate components, which he labeled crystallized and fluid ability. The former construct reflects the influence of formal education and acculturation. It represents well-learned facts and cognitive operations and may be assessed with tests of vocabulary, general information, and academic achievement. Individuals can increase their levels of crystallized ” g” throughout the life span via formal education, personal reading, socialization, and other activities that require new learning and novel problem solving. Conversely, fluid ” g” is akin to innate ability that reflects the biological integrity of the central nervous system. Fluid ability peaks in adolescence or young adulthood and declines with advancing age and/or neurological disease or insult involving the brain. Fluid ability is not related to education or acculturation and is assessed by tests of working memory, matrices, and concept formation. From a practical standpoint it appears that fluid ability plus motivation begets crystallized ability and achievement. Cattell’s theory has been modified and expanded (see Carroll, 1997) and stands today as the most comprehensive and well-validated description of human cognitive abilities. The work of Cattell, Horn, and Carroll, which is today referred to as the Cattell-Horn-Carroll Theory (CHC), has had a profound influence on the field of intelligence assessment. For instance, the WAIS-III and WISC-IV for the first time include a matrix reasoning subtest designed specifically to measure fluid intelligence, and the Woodcock-Johnson Test of Cognitive Abilities-Third Edition, Stanford-Binet Intelligence Scale-V, and Kaufman Assessment Battery for Children-Second Edition each provide summary scores measuring crystallized and fluid intelligence.

A theory of multiple intelligences (MI) was introduced by Howard Gardner in 1983. He posits the existence of at least eight intelligences that are relatively independent of one another and are unrelated to “g ” with two possible exceptions . The intelligences conceptualized by Gardner are as follows:

Linguistic: The capacity to use language effectively and to learn new languages. This is characteristic of many groups including attorneys, writers, and poets. Because of its linguistic nature, this domain is likely to show an association with “g. “
Spatial: The capacity to visually perceive the world and discriminate patterns. This ability is important for airplane pilots, surgeons, and sculptors, among others.
Logical-Mathematical: The ability to learn higher mathematics, display logical thinking, and design and carry out scientific experiments. Occupations requiring a good deal of this ability include mathematician, scientist, and logician. This domain is likely to show an association with “g.”
Interpersonal: This involves sensitivity to the feelings, motivations, and intentions of other people. This capacity characterizes successful politicians, salespeople, and therapists.
Intrapersonal: The capacity to understand oneself in terms of personal fears, motivations, and capacities. This ability is demonstrated by persons who are effective self-monitors and who can properly utilize their intellectual assets.
Naturalistic: This capacity involves the ability to recognize and classify different species and to recognize natural patterns. Successful biologists, farmers, and gardeners demonstrate these abilities.
Musical: The ability to appreciate music and to demonstrate talent regarding the discrimination of tones in terms of melody, intensity, and rhythmic patterns. Groups with musical intelligence include singers, composers, and musicians.
Body-Kinesthetic: This refers to the ability to use the whole body to create products or solve problems. Successful surgeons, dancers, and athletes are likely to possess this capacity.

MI theory has been embraced by many professionals within the educational community, partly because of Gardner’s unusual approach to assessing intelligence and partly because of his argument that assessments must test examinees’ proficiencies in completing culturally valued tasks. For example, in his work with preschool children Gardner has evaluated Logical-Mathematical, Body-Kinesthetic, and Spatial intelligences by having examinees disassemble and reassemble everyday items such as doorknobs and pencil sharpeners (Visser, Ashton, & Vernon, 2006). As interesting as this approach may appear, neither Gardner nor any test publisher has yet to produce a single standardized instrument based on MI theory. Moreover, empirical research has contradicted Gardner’s contentions by demonstrating that when tests that appear to measure the various intelligences are simultaneously subjected to statistical analyses, many are substantially intercorrelated and show strong loadings on a “g” factor. Visser et al. (2006) imply that it is (a) premature to employ MI theory as a basis of curriculum development and (b) unlikely that MI theory provides any new information about the structure of intellect that is not already contained in the Spearman and CHC models discussed above.

Another model of intelligence is the triarchic theory of Robert J. Sternberg (1985, 1997). This model emphasizes “practical intelligence” along with distinctions among analytic abilities, creative abilities, and practical abilities. Sternberg claims that these constructs differ from “g” and predict real-world success as well as or better than do traditional IQ measures. The intelligences in the triarchic theory are as follows:

Analytic—The ability to solve complex problems, analyze information, think critically, acquire new concepts, and successfully utilize academic knowledge. This ability is similar to what conventional IQ tests purport to measure. This is the componential part of the theory that associates internal mental processes with intelligence.
Creative—The ability to generate ideas, identify problem-solving options, determine which problems need to be solved, and deal effectively with novelty. This is the experiential part of the theory that is thought to relate intelligence to the individual’s internal and external worlds.
Practical—The ability to deal effectively with real-world problems using tacit knowledge. The latter concept refers to information and skills that reflect “knowing how to do things” within a specific culture or environment. Tacit knowledge is not typically taught in school or explicitly verbalized. This is the contextual dimension of the theory and reflects the application of analytic and creative intelligences to achieve personal goals within a specific environment.

The triarchic theory assumes that ” g” is related only to analytic abilities and that the analytic, creative, and practical intelligences are independent of one another. However, when researchers administered the Sternberg Triachic Abilities Test (STAT) and a conventional mea-sure of ” g” to a sample of gifted students, highly significant correlations emerged between ” g” and the three intelligences, which were also significantly intercorrelated (Brody, 2003). Thus, the three triachic abilities are not independent of one another and ” g” is a component of each. Although Sternberg’s theory is both interesting and highly creative, it would be premature to embrace this approach uncritically. Additional research is needed to demonstrate that the three intelligences represent useful constructs and that they provide information that is not already provided by other theories and methods (Gottfredson, 2003a, 2003b).

Controversial Issues

An important concern for anyone interested in the field of human intelligence is the failure of scientists and practitioners to produce a universally accepted definition of the construct. Nevertheless, standardized tests such as the Wechsler Scales and the Stanford-Binet are frequently administered in schools, clinics, and industry and provide useful information about the cognitive functioning of individual examinees, especially when interpreted in conjunction with scores from other tests (e.g., language and memory) and information on educational attainment, social adaptation, and medical status. Because IQ scores carry significant implications for the future of the examinee (e.g., placement in a gifted program) or his/her current situation (e.g., competency to stand trial for a legal offense), it would be helpful to know whether the experts who administer intelligence tests and those who rely on test scores when making decisions about people share similar opinions on the nature of intelligence. Snyderman and Rothman (1987) conducted a survey of over 750 experts (e.g., professors, psychologists, and educational specialists) and asked each participant whether he or she felt that there was a consensus among trained professionals as to the types of behaviors and characteristics that are designated “intelligent.” While 53 percent agreed that there was a consensus, 39.5 percent felt that a consensus had not been achieved. The next question required respondents to review a list of 13 descriptors and to check all that they felt were important elements of intelligence. They were also asked to indicate whether or not current intelligence tests adequately measure each descriptor. Respondents were provided with space to write down any additional descriptors they felt had been omitted from the original list.

Results of the survey are presented in Table 44.1 and suggest that there is a good deal of consensus among experts concerning the key elements defining intelligence. However, characteristics such as adaptation to the environment and mental speed are clearly not measured adequately by intelligence tests that were in use at the time of the survey.

Any discussion of intelligence and its assessment would be incomplete without mentioning the heritability of general intelligence and its contemporary marker, the IQ score. When all is said and done, this controversial topic boils down to determining the relative contributions of nature (genetics) versus nurture (environmental influences) in explaining individual and group differences in “g” and in intelligence test performance. This is a topic of interest because it has been reported that in terms of average IQ, Jewish Americans perform best followed in order by Asian, white, Latino, and African Americans (Herrnstein & Murray, 1994). The discussion that follows draws heavily on the work of Brody (1992), Gottfredson (2005), Nisbett (2005), Reynolds (2000), and Rushton and Jensen (2005). Three basic positions that address the nature versus nurture controversy are presented:

Culture-only theory: Differences among whites, blacks, Hispanics, Asians, and other groups result exclusively from dissimilarities in environmental and cultural experiences that reflect inequalities across groups in terms of educational, nutritional, economic, and social opportunities. This hypothesis, which may be attributed in part to the work of the behavioral psychologist J. B. Watson, predicts that gaps between the groups on measures of “g,” standardized intelligence scales, and academic achievement tests, to mention only a few of the possible indicators, will increase or decease depending on the degree of similarity or dissimilarity of environmental and cultural opportunities. Genetic heritage is, for the majority of people, irrelevant.

Table 44.1 Descriptors of human intelligence

In the United States over the past 80 years, whites have consistently earned IQs that are about 15 points higher than those of blacks (mean IQs of 100 and 85, respectively). However, there is evidence that this disparity has declined in recent decades and may actually be eliminated within 20 years. One can only speculate as to why this change is occurring, but it supports the culture-only hypothesis. Advocates of this position attribute the finding to improved nutrition, education, and socioeconomic status among African Americans, along with reduced discrimination and prejudice toward blacks on behalf of the government and majority population. Examination of mean IQs from the WISC-IV, which was published in 2003, reveals a clear rank ordering of the racial groups in the standardization sample as follows: Asians (106.5), whites (103.2), Hispanics (93.1), and African Americans (91.7). These data indicate that the IQ gap between whites and blacks on this highly regarded measure of intelligence has narrowed by .23 of a standard deviation (Weiss, Saklofske, Prifitera, & Holdnack, 2006).

Additional support for the culture-only hypothesis is cited in Nisbett (2005) and involves a comparison of IQs from German children fathered by African American military personnel with German children fathered by white American solders. The groups of fathers demonstrated theexpected white-black IQ disparity on tests of intelligence. However, the children of white GIs and black GIs had average IQs of 97 and 96.5, respectively. This finding suggests that the black-white IQ gap seen in American samples is not genetically determined.

Hereditarian theory: Differences across racial groups are due to an interaction of genetic and environmental influences that are roughly 50 percent genetic and 50 percent environmental. In part, this hypothesis may be attributed to Charles Darwin and Sir Frances Galton and predicts that average group differences in measured “g” and other ability tests will remain, albeit somewhat diminished, if all racial groups are treated equally and have identical environmental and cultural opportunities. Evidence supporting this position comes from adoption studies, investigations of mono-zygotic and dizygotic twin pairs, and studies demonstrating that “g” and IQ are rooted substantially in biology.

In one investigation, researchers obtained IQ scores on three groups of participants: biological fathers whose sons were adopted, stepfathers, and adult sons. The intelligence tests were administered during military induction of the fathers, stepfathers, and sons. The correlation between biological fathers and their adult sons was .20, whereas the association between IQ scores of adoptive fathers and their adult stepsons was a nonsignificant .02. This finding suggests that adopted children, even after reaching adulthood, are more likely to resemble their biological (genetic influences) fathers than their adoptive fathers (environmental influences).

Monozygotic twins develop from a single egg and have the same genetic makeup (identical twins). Conversely, dizygotic pairs originate from two eggs and have the genetic similarity of siblings (fraternal twins). If IQ and ” g” are influenced by genetics, monozygotic twins should be more alike in terms of performance on ability measures than are dizygotic twins. This appears to be the case because the IQs of identical twins reared together correlate .86, whereas the correlation is .55 for fraternal twins reared together. For twin pairs reared apart, the IQ correlations are .76 and .35 for identical and fraternal twins, respectively. These patterns and levels of association, which are reported in Sattler (2001), suggest that, as far as IQ is concerned, genetic factors account for a major proportion of the variance.

There is a large body of research demonstrating that general intelligence and biological characteristics are significantly associated. In a recent meta-analysis involving 37 samples with a total of 1530 individuals, Mc Daniel (2005) reported that brain volume and intelligence as measured by standardized ability tests are correlated .41 for adult women and .38 for adult men. A reasonable conclusion from this line of research is that bigger brains are more efficient because they contain more neurons and synapses than smaller brains. There are at least two studies reviewed by Brody (1992) of significant associations (rs = .40 and .42) between IQ and conduction velocities in the median nerve of the arm. This measure of peripheral nervous system function is purely biological and involves no cognitive activity on the part of the study participants. Finally, inspection time (IT; time required to become aware of a stimulus by varying exposure time) in undergraduate students correlates -.74 with a popular test of fluid intelligence, suggesting that IT reflects a neural-processing aspect of intellectual functioning (Osmon & Jackson, 2002).

Test bias theory: This position assumes that intelligence scales and other ability tests (e.g., Scholastic Aptitude Test [SAT]) systematically underestimate the knowledge, aptitudes, and skills of minority members because they are poorly designed and culturally loaded in favor of middle-class persons of Euro-American descent. This position is a variant of the culture-only hypothesis and lacks empirical support. Nevertheless, it is so frequently asserted by critics of intelligence testing that it is worthy of independent discussion. Critics of psychometric assessment base their claims of test bias on mean score differences across racial, ethnic, and socioeconomic groups or the presence of individual items within a test that appear to be unfair or insulting to minority members.

The “mean score difference” definition of test bias has been widely researched and found to be without merit. Although groups of interest may differ in level of performance, studies of intelligence measures such as the Wechsler scales have repeatedly found little or no differences across ethnic/racial/sociocultural groups in terms of item order difficulty levels, internal consistency, and patterns of scoring determined by computation of the factorial structure of the test. Another approach to assessing bias in an IQ test is to evaluate its ability to predict academic achievement (or some other relevant variable such as job performance) for different ethnic, racial, and/ or sociocultural groups. This is typically accomplished by first generating regression lines to predict academic achievement scores on the basis of IQ for each group and than comparing these lines statistically. Numerous investigations have demonstrated that widely used ability tests, including the Wechsler scales and Stanford-Binet, in most instances predict achievement scores in an effective and unbiased manor. However, an IQ test is said to be biased against a specific ethnic group if it systematically under-predicts academic achievement and performance for those individuals. If the test score in question is used to deny placement in a gifted program or admission to college, this would be an unacceptable situation since, if given the opportunity, these examinees are likely to perform better than expected based on the test scores alone. However, the only instances where bias in prediction has emerged involved overpredicting the achievement of minority persons. When researchers compared whites and minorities, the actual achievement of the latter individuals was often lower than predicted using a regression equation developed using both groups together.

The most common claim of test bias involves subjective examination of individual test items. This approach may identify potentially offensive content but it is ineffective for selecting biased items. Subjective examination is simply a matter of opinion as to whether an item is unfair, offensive, or biased for one or more groups in the population. A number of investigations have demonstrated that “expert” representatives from the majority and minority communities performed at no better than chance levels, and in some cases below chance levels, when they attempted to identify biased test items. A classic example of “expert” judgmental error involves an item taken from the Wechsler Intelligence Scales for Children. The child is asked what one should do if a much smaller child starts to fight with you. It was the opinion of some “experts” that this item was biased against African Americans because they felt that urban black children are taught by their parents and friends to strike smaller children who are showing aggression toward them. Statistical analysis of item difficulty levels for African American and Euro-American children who were asked this question indicated that the former group found the item easier than did the latter group. In a second study with an entirely new sample of participants, the “fight” item was passed by 73 percent of African American children and by 71 percent of Euro-American children (Sattler, 2001). Obviously, subjective inspection of test content is ineffective for identifying which items are more difficult for one ethnic group compared to another. However, review of test items by “experts” is worthwhile if it succeeds in eliminating insensitively worded or offensive items from future tests.

Applications

There is little doubt that the construct of human intelligence and its assessment has had a major impact on societies as well as on individuals. For example, Lynn and Vanhanen (2002) proffered the view that IQ is one of the more important determinants of national economic development. They took the well-established fact that IQ and socioeconomic status are positively and significantly correlated for individuals and extended this idea to nations. After deriving IQ scores (from the average of various intelligence tests) for 81 countries, they reported highly significant associations between IQ and measures of per capita gross domestic product (GDP). Although the nations with the lowest IQs also had the lowest GDPs, the picture was more variable for high-IQ countries. Those with GDPs lower than expected on the basis of their IQs typically had a history of imposed economic regulation (e.g., recent or current Communist political structure). Information of this type may prove useful to world leaders who are constantly trying to identify and eliminate problems associated with globalization.

For individuals, the construct of intelligence and its measurement has a great deal of importance because ability tests are utilized in numerous settings such as schools, hospitals, clinics, and employment offices. Based on a survey of 277 clinical psychologists (Harrison, A. S. Kaufman, Hickman, & N. L. Kaufman, 1988), the foremost reason for administering an intelligence test was to estimate the person’s potential or cognitive capacity. Three additional purposes for giving an intelligence test include (a) the need to obtain clinically relevant information about cognitive strengths and weaknesses, (b) assessing the functional integrity of the brain, and (c) assisting in determining appropriate vocational or educational placement. Today, adolescents and adults referred for cognitive evaluation will almost certainly be given the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). Because the WAIS-III is one of the most thoroughly researched and frequently administered individual intelligence tests (Kaufman & Lichtenberger, 2006), a brief description of the scale is provided in Table 44.2.

Trained examiners must administer, score, and interpret the WAIS-III, with testing times ranging from approximately 60 to 120 minutes. Administration time varies depending on the overall level of ability of the examinee and whether a neurological or psychiatric disorder is part of the clinical picture. The WAIS-III is typically administered as part of a test battery. For example, if an examinee is referred for vocational assistance, tests of occupational interests and specific aptitudes (e.g., mechanical, dental, etc.) may supplement the WAIS-III. For examinees with a neurological disorder involving the brain (e.g., suspected Alzheimer’s disease or history of significant head injury), measures of memory, constructional praxis, and executive functions are likely to be included in the test battery.

Future Trends

In the future, although no universal definition of intelligence will be formulated, it is certain that basic research will continue unabated, as will standardized testing in educational, clinical, and employment settings. Interest in the biological and sensory-motor correlates of human ability, reminiscent of Galton and associates, will reemerge as a scientifically respectable line of research. As popular tests are revised and updated, there will be attempts to link research, theory (especially from cognitive psychology), and practice. Traditional IQs will be further deemphasized, but the old standards of general information, attention-concentration, vocabulary knowledge, abstract thinking, and various forms of nonverbal problem solving and processing speed will continue to be assessed. The WAIS-IV will follow the WISC-IV and drop both the Verbal and Performance IQs when it is published sometime between 2008 and 2010.

Although the WAIS-IV Full Scale IQ will remain, it will be deemphasized and attention will be given to Indexes that measure separate capacities of intelligence within a theoretical framework. Future tests will likely include components or subtests that assess effective intelligence, both within and independent of dominant cultural influences. Finally, it is hoped that the major test publishers will include measures in their scales that tap variables not traditionally viewed as relevant. Lykken (2005) noted that extraordinary mental energy is a characteristic of great intellects (e.g., Galton, Picasso, Napoleon, and Einstein) and that it is an essential component of any formula for exceptional accomplishment. If a valid and reliable measure of mental energy were devised and included as part of standard test administration, the product of intelligence (e.g., Full Scale IQ) and mental energy might be a better predictor of academic and occupational success than IQ alone.

Table 44.2 Description of the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III)

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