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Unit 11 Intelligence

Testing and Individual Differences



Today, intelligence is generally considered to be the ability to learn from experience, solve problems, and adapt to new situations. Psychologists debate whether intelligence is one general ability or several specific abilities. Some theorists have expanded the definition of intelligence to include social intelligence, especially emotional intelligence. Psychologists have linked people’s intelligence to brain anatomy and functioning as well as to cognitive processing speed.

Modern intelligence testing began more than a century ago in France when Alfred Binet developed questions that helped predict children’s future progress in the Paris school system. Lewis Terman of Stanford University used Binet’s ideas to develop the Stanford-Binet intelligence test. German psychologist William Stern derived the formula for the famous intelligence quotient, or IQ.

Modern aptitude and achievement tests are widely accepted only if they are standardized, reliable,and valid. Aptitude tests tend to be highly reliable, but they are weak predictors of success in life. One way to test the validity of a test is to compare people who score at the two extremes of the normal curve: the challenged and the gifted.

Studies of twins, family members, and adopted children point to significant genetic determinants of intelligence test scores. These and other studies also indicate that environment significantly influences intelligence test scores. Psychologists debate evolutionary and cultural explanations of gender differences in aptitudes and abilities. Environmental differences are perhaps entirely responsible for racial gaps in intelligence.

Aptitude tests, which predict performance in a given situation, are necessarily “biased” in the sense that they are sensitive to performance differences caused by cultural experiences. However, the major tests are not biased in that they predict as accurately for one group as for another.Stereotype threat can adversely affect performance and sometimes appears in intelligence testing among some minorities and women.


What Is Intelligence?


As a socially constructed concept, intelligence varies from culture to culture. Thus, most psychologists now define intelligence as the ability to learn from experience, solve problems, and use knowledge to adapt to new situations. To reify something is to view an abstract, immaterial concept as if it were a concrete thing. Thus, to reify IQ is to treat the intelligence quotient as if it were a fixed and objectively real trait, such as height, rather than as a score received on an intelligence test.


Psychologists agree that people have specific abilities, such as verbal and mathematical aptitudes. However, they debate whether a general intelligence (g) factor runs through them all, as proposed by Charles Spearman. Factor analysis has identified several clusters of mental abilities, including verbal intelligence, spatial ability, and reasoning ability. Still, there seems to be a tendency for
those who excel in one of the clusters to score well on others, as suggested by the results of L. L. Thurstone’s ranking of people’s primary mental abilities. Some psychologists today agree with Spearman’s notion that we have a common level of intelligence that can predict our abilities in all other academic areas.


Evidence that brain damage may diminish one ability but not others, as well as studies of savant syndrome, led Howard Gardner to propose his theory of multiple intelligences. These include linguistic, logical-mathematical, musical, spatial, bodily-kinesthetic, intrapersonal, interpersonal, and naturalist. Robert Sternberg also proposes a triarchic theory of multiple intelligences in which he distinguishes among analytical (academic problem solving), practical, and creative intelligences.


Distinct from academic intelligence is social intelligence, an aspect of which is emotional intelligence. The four components of emotional intelligence are (1) the ability to perceive emotions (to recognize them in faces, music, and stories), (2) to understand emotions (to predict them and how they change and blend), (3) to manage emotions (to know how to express them in varied situations), and (4) to use emotions to enable adaptive or creative thinking. Those who are emotionally smart often succeed in careers, marriages, and parenting where other academically smarter (but emotionally less intelligent) people fail. Critics of the idea of emotional intelligence argue that we
stretch the idea of intelligence too far when we apply it to emotion.


Several studies report a positive correlation (+.33) between brain size (adjusted for body size) and intelligence score. Moreover, as adults age, brain size and nonverbal intelligence test scores fall in concert. Some studies suggest that highly educated people die with more synapses. The direction of the relationship between brain size and intelligence remains unclear. Larger brain size may
enable greater intelligence, but it is also possible that greater intelligence leads to experiences that exercise the brain and build more connections, thus increase its size. Or, some third factor may be at work. Some evidence suggests that highly intelligent people differ in their neural plasticity.


People who score high on intelligence tests tend to retrieve information from memory more quickly. Research also suggests that the correlation between intelligence score and the speed of taking in perceptual information tends to be about +.3 to +.5. Those who perceive quickly are especially likely to score higher on tests based on perceptual rather than verbal problem solving. The brain waves of highly intelligent people register a simple stimulus, such as a flash of light, more quickly and with greater complexity. The evoked brain response also tends to be slightly faster when people with high intelligence rather than low intelligence scores perform a simple task, such as pushing
a button when an X appears on the screen. As yet, psychologists have no firm idea of why fast reactions on simple tasks should predict intelligence test performance.



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Assessing Intelligence



The modern intelligence-testing movement started at the turn of the twentieth century when French psychologist Alfred Binet began assessing intellectual abilities. Together with Théodore Simon, Binet developed an intelligence test containing questions that assessed mental age and helped predict children’s future progress in the Paris school system. The test sought to identify
French schoolchildren needing special attention. Binet and Simon made no assumption about the origin of intelligence.


Lewis Terman believed that intelligence was inherited. Like Binet, he believed that his test, the Stanford-Binet, could help guide people toward appropriate opportunities. William Stern derived the intelligence quotient, or IQ, for Terman’s test. The IQ was simply a person’s mental age divided by chronological age multiplied by 100. During the early part of the twentieth century, intelligence tests were sometimes used in ways that, in hindsight, even their designers regretted—“documenting” a presumed innate inferiority of ethnic and immigrant groups not sharing an Anglo-Saxon heritage.


Aptitude refers to the capacity to learn, and thus aptitude tests are those designed to predict a person’s future performance. Achievement tests are designed to assess what a person has learned. TheWechsler Adult Intelligence Scale (WAIS) is the most widely used intelligence test. David Wechsler developed a version for school-age children (the Wechsler Intelligence Scale for Children [WISC]), and another for preschool children. The WISC consists of 11 subtests and yields not only an overall intelligence score but also separate verbal comprehension, perceptual organization, working memory, and processing speed scores. Striking differences between these scores can provide clues to cognitive strengths that a teacher or therapist might build on. Other comparisons can help clinicians identify a possible reading or language disability.


Because scores become meaningful only when they can be compared with others’ performance, they must be defined relative to a pretested group, a process called standardization. Obviously, the group on which a test is standardized must be representative of those who will be taking the test in the future. Standardized test results typically form a normal distribution, a bell-shaped pattern of
scores that forms the normal curve. Most scores cluster around the average, and increasingly fewer are distributed at the extremes. Intelligence test scores form such a curve, but in the past several decades the average score has risen, a phenomenon known as the Flynn effect. The cause of this increase remains a mystery.


Reliability refers to the extent to which a test yields consistent scores. Consistency may be assessed by comparing scores on two halves of the test (split-half), on alternative forms, or on test-retest. A test can be reliable but not valid. Validity refers to the extent to which a test measures or predicts what it is supposed to. Content validity is determined by assessing whether the test taps the pertinent behavior, or criterion. For example, road tests for a driver’s license should measure driving ability. Predictive validity is determined by computing the correlation between test scores and the criterion behavior. Aptitude tests have predictive validity if they can predict future achievement. The predictive power of aptitude scores diminishes as students move up the educational ladder.



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The Dynamics of Intelligence



The stability of intelligence test scores increases with age. By age 4, children’s performance on intelligence tests begins to predict their adolescent and adult scores. After about age 7, intelligence scores, though certainly not fixed, stabilize.


At one extreme of the normal distribution are people whose intelligence scores fall below 70. To be labeled as having an intellectual disability (formerly referred to as mental retardation), a child must have both a low test score and difficulty adapting to the normal demands of living independently. Intellectual disability sometimes results from known physical causes, such as Down syndrome,
a disorder of varying severity that is attributed to an extra chromosome in the person’s genetic makeup. Most mentally challenged adults can, with support, live in mainstream society.


At the other extreme are the “gifted.” Contrary to the popular myth that they are frequently maladjusted, research suggests that high-scoring children are healthy, well adjusted, and academically successful. Controversy surrounds “gifted child” programs in which the “gifted” are segregated and given academic enrichment not available to the masses. Critics note that tracking by aptitude sometimes creates a self-fulfilling prophecy: Those implicitly labeled “ungifted” can be influenced to become so. Denying lower-ability students opportunities for enriched education can widen the achievement gap between ability groups and increase their social isolation from one another.

Genetic and Environmental Influences on Intelligence


Studies of twins, family members, and adopted children together point to a significant genetic contribution to intelligence scores. For example, the test scores of identical twins reared separately are similar enough to lead one researcher to estimate that “about 70 percent” of intelligence score variation “can be attributed to genetic variation.” Furthermore, the most genetically similar people have the most similar scores ranging from +.85 for identical twins raised together, to about +.33 for unrelated individuals raised together.


Heritability refers to the extent to which differences among people are attributable to genes. To say that the heritability of intelligence is 50 percent does not mean that half of an individual’s intelligence is inherited. Rather, it means that we can attribute to heredity 50 percent of the variation of intelligence among those studied.


Studies of twins, family members, and adopted children also provide evidence for environmental influences on intelligence. The intelligence test scores of fraternal twins raised together are more similar than those of other siblings, and the scores of identical twins raised apart are less similar than the scores of identical twins raised together. Studies of children reared in extremely neglectful or enriched environments also indicate that life experiences significantly influence intelligence test scores. For example, research indicates that schooling and intelligence contribute to each other (and that both enhance later income). Programs such as Head Start increase school readiness and
provide at least a small boost to emotional intelligence.


Although gender similarities far outnumber gender differences, we find the differences in abilities more interesting. Research indicates that, compared with males, females are better spellers; are more verbally fluent; are better at remembering and locating objects; are more sensitive to touch, taste, and color; and are better emotion detectors. Males’ mental ability scores vary more than
females’, and thus boys outnumber girls at both the low extreme and the high extreme. Boys outperform girls in spatial ability tests and at math problem solving, but they underperform them in math computation. According to different perspectives, these differences may be explained as evolutionarily adaptive for each gender or as the result of social expectations and divergent opportunities.


American Blacks average about 10 points lower than White Americans on intelligence tests. European New Zealanders outscore native Maori New Zealanders, Israeli Jews outscore Israeli Arabs, and most Japanese outscore the stigmatized Japanese minority. Research suggests that environmental differences are largely responsible for these group differences. Consider: (1) genetics research indicates that the races are remarkably alike under the skin; (2) race is not a neatly defined biological category; (3) Asian students outperform North American students on math achievement and aptitude tests; (4) intelligence test performance of today’s better-fed, better educated,
and more test-prepared population exceeds that of the 1930s population by the same margin that the score of the average White today exceeds that of the average Black; (5) White and Black infants tend to score equally well on tests measuring preferences for looking at novel
stimuli—a predictor of future intelligence; and (6) in different eras, different ethnic groups have experienced periods of remarkable achievement.


Intelligence tests are “biased” in the sense that they are sensitive to performance differences caused by cultural experience. However, tests are not biased in that they predict as accurately for one group as they do for another. For example, the predictive validity is roughly the same for men and women, for Blacks and Whites, and for rich and poor. Stereotype threat is a self-confirming concern that one will be evaluated based on a negative stereotype. The phenomenon sometimes appears in intelligence testing among African-Americans and among women of all colors.


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*Work Cited:  All summary notes come from *Myers Pyschology for AP, Lecture Guides (2011 Worth Publishers)

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