Chapter 10 Intelligence

2. 10-1 Measuring Intelligence Intelligence is defined as the mental abilities necessary to adapt to and shape the environment (Grossman & Kaufman, 2002; Neisser et al., 1996). Psychometrics is the measurement of intelligence, personality, and other mental processes. The psychological tests developed by psychometricians assess the individual differences that exist between people on a wide variety of abilities interests, and personality traits.

3. 10-1a Early Intelligence Testing Was Shaped by Racial and Cultural Stereotypes Francis Galton: Quantifying intelligence Galton reasoned that if traits are inherited, then similar levels of intelligence should consistently appear in families over generations. He fostered the idea of eugenics, which is the practice of encouraging supposedly superior people to reproduce, while discouraging or even preventing those judged inferior to do so. Galton measured intelligence by testing sensory abilities and reaction time, as well as by measurement of head size and muscle strength Galton�s tests did not correlate well with each other.

4. 10-1a Early History of Intelligence Testing Was Shaped by Racial and Cultural Stereotypes (cont.) Alfred Binet: The �father� of intelligence testing Binet reasoned that general mental ability can be calculated by comparing children�s mental age with their chronological age. Unlike Galton, Binet made no assumptions about why intelligence differences exist, and he believed that intellectual ability could be increased through education. Binet realized that his test merely sampled intelligence and did not measure all intellectual aspects. He warned that since the test was developed in France using children with similar cultural backgrounds, it may not accurately measure intelligence in other countries.

5. 10-1a Early History of Intelligence Testing Was Shaped by Racial and Cultural Stereotypes (cont.) IQ testing in America Henry Goddard was the first to translate and use Binet�s test in the United States. Unlike Binet, Goddard believed that the Binet-Simon Test measured inherited intelligence. Goddard�s testing of intelligence was used to help pass the Immigration Act of 1924, which dramatically restricted the admittance of certain �undesirable� ethnic groups, especially those from eastern and southern Europe (Sedgwick, 1995).

6. 10-1b Modern Tests of Mental Abilities Measure Either Aptitude or Achievement When describing mental abilities tests, psychologists generally place them into two different categories (Wasserman, 2003): Aptitude tests are tests designed to predict a person�s capacity for learning. Achievement tests are tests designed to assess what a person has learned.

7. 10-1b Modern Tests of Mental Abilities Measure Either Aptitude or Achievement (cont.) The Stanford-Binet Intelligence Test Lewis Terman revised the Binet-Simon Test so that it could be used on American children. The resulting Stanford-Binet Intelligence Test employed a new scoring system known as the intelligence quotient (IQ). The intelligence quotient (IQ) was originally the ratio of mental age to chronological age multiplied by 100 (MA/CA x 100). Today, it is calculated by comparing how a person�s performance deviates from the average score of her or his same-age peers, which is 100.

8. 10-1b Modern Tests of Mental Abilities Measure Either Aptitude or Achievement (cont.) The Wechsler Intelligence Scales David Wechsler developed the deviation IQ score and today�s most widely used set of intelligence tests, Wechsler Intelligence Scales. The Wechsler Intelligence Scales contain both verbal and performance (nonverbal) subscales. Three separate types of Wechsler Intelligence Scales can be used, each based on the age of the individual: Wechsler Adult Intelligence Scale (WAIS) Wechsler Preschool and Primary Scale of Intelligence (WPPSI) Wechsler Intelligence Scale for Children (WISC)

9. 10-1b Modern Tests of Mental Abilities Measure Either Aptitude or Achievement (cont.) Group-administered tests While the Stanford-Binet and the Wechsler tests are administered individually to people, group-administered tests can assess hundreds or thousands of people simultaneously. Scholastic Assessment Test (SAT): College entrance exam that measures learned verbal and mathematical skills Tests used to assess students� potential for postgraduate training include: Graduate Record Exam (GRE) Graduate Management Admission Test (GMAT) Medical College Admission Test (MCAT) Law School Aptitude Test (LSAT)

10. 10-1c Psychological Tests Must Be Standardized, Reliable, and Valid All psychological tests, including intelligence tests, are measurement instruments that must have three basic characteristics: Standardization: The process of establishing uniform procedures for administering a test and for interpreting its scores Reliability: The degree to which a test yields consistent results Validity: The degree to which a test measures what it is designed to measure

11. 10-1c Psychological Tests Must Be Standardized, Reliable, and Valid (cont.) Standardization Standardized test results often show a roughly normal distribution. Normal distribution: The bell-shaped appearance of standardized tests when individual scores are placed in a graph. Most scores cluster around the average score, and fewer scores are found far from the average. Periodically, the Stanford-Binet and the Wechsler IQ tests are restandardized to maintain the mean score of 100. This restandardization is necessary due to the Flynn effect. Flynn effect: The tendency for people�s performance on IQ tests to improve from one generation to the next

12. Figure 10-3 The Normal Distribution

13. 10-1c Psychological Tests Must Be Standardized, Reliable, and Valid (cont.) Reliability The most common type of technique to estimate reliability is: Test-retest reliability involves checking to see how people score on the same test on two separate occasions. One drawback to this technique is that people tend to remember the test items when they take the test again. A solution to the problems encountered with test-retest reliability would be to use alternate-forms reliability. Alternate forms reliability is when slightly different versions of the test are given to people on two separate occasions. While the items on the two test versions are similar in format, they are different enough in content so that the test-taker�s performance will not be influenced by familiarity.

14. Figure 10-4 Determining Both Test-Retest and Alternate-Forms Reliability For test-retest reliability and alternate-forms reliability, people�s scores at time 1 are depicted on the left, and their scores at time 2 are depicted on the right. Condition (a): When people obtain similar scores on both occasions, the test has high reliability. Condition (b): When people obtain very different scores, the test has low reliability.

15. 10-1c Psychological Tests Must Be Standardized, Reliable, and Valid (cont.) Validity Researchers determine whether an intelligence test is valid by analyzing different aspects of the test (Daneman & Hannon, 2001; Ukrainetz & Blomquist, 2002). Content validity is the degree to which the items on a test are related to the characteristics the test supposedly measures. Predictive validity is the degree to which a test predicts other observable behavior related to the characteristic the test supposedly measures (also known as criterion validity).

16. 10-1d Intelligence Tests Are Not �Culture-Free� Intelligence tests measure people�s developed abilities at a particular point in time. As such, they detect not only innate difference in intellectual abilities, but also differences due to cultural learning and experiences. Some of the test items on the most frequently used IQ tests in the United States are still based on the vocabulary and experiences of the dominant middle-class culture. The question of cultural bias in intelligence testing is an issue when attempting to assess and compare the intellectual abilities of people in different cultures around the world.

18. 10-2a Early Factor-Analytic Studies Led to Conflicting Conclusions about �General Intelligence� Based on his factor analytic research, Charles Spearman (1927) concluded that intelligence was determined by a general intelligence factor, or g. Factor analysis is a statistical technique that allows researchers to identify clusters of variables or test items that correlate with one another. General Intelligence (g) is a general intelligence factor that Spearman and other researchers believed underlies all mental abilities

19. 10-2b Cattell Distinguished between Crystallized and Fluid Intelligence Cattell (1963, 1971) agreed with Spearman�s idea of general intelligence, but his own factor analysis suggested the existence of two kinds of g, which he labeled crystallized and fluid. Crystallized intelligence is the knowledge acquired through experience, such as the acquisition of facts and the ability to use and combine them. People with high crystallized intelligence are adept at using previously learned information to solve familiar problems.

20. 10-2b Cattell Distinguished between Crystallized and Fluid Intelligence (cont.) Fluid intelligence is the mental capacity to learn or invent new strategies for dealing with new kinds of problems. People with high fluid intelligence have the ability to understand the relationship between things without having had past experience or practice with them. Research both supports and undermines Cattell�s theory.

21. 10-2c Gardner�s Theory of Multiple Intelligences Broadens the Concept of Intelligence Howard Gardner proposed a theory of multiple intelligence. Gardner�s theory contends that there are at least eight distinct and relatively independent intelligences (linguistic or verbal, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalist), all of which are differently developed in each of us (Gardner, 1998; Gardner et al., 1996). Recently, he has also proposed a possible ninth intelligence�existential intelligence (Gardner, 1999, 2003). Linguistic, logical, and mathematical are the most highly valued in Western culture and are the ones measured by conventional intelligence tests.

22. 10-2c Gardner�s Theory of Multiple Intelligences Broadens the Concept of Intelligence (cont.) The existence of prodigies, or individuals who easily master skills in one intellectual area, supports Gardner�s theory. Even greater intellectual variance can be found among savants. Savants are individuals who demonstrate exceptional ability in specific intellectual areas, while having very limited mental abilities in all other areas (Detterman et al., 2000; Treffert, 1992).

23. 10-2d Sternberg�s Triarchic Theory Identifies Three Sets of Mental Abilities Sternberg�s triarchic theory of intelligence asserts that human intelligence can be more simply described as comprising three sets of mental abilities. The triarchic theory does not define intelligence according to our skill in all three aspects combined. Sternberg (1997) suggests that people learn best if they are taught in a way that is compatible with their strongest type of intelligence.

24. Figure 10-7 Sternberg�s Triarchic Theory of IntelligenceAccording to Robert Sternberg, intelligence consists of analytical, creative, and practical abilities.

25. 10-2e Emotional Intelligence Allows Us to Understand and Regulate Our Emotional and Social Lives Social intelligence is believed to be part of our primate evolutionary heritage (Byrne, 1995), which affects interpersonal coordination and planning, thereby increasing the survival of our ancestors. An important aspect of social intelligence is what various researchers have called emotional intelligence.

26. 10-2e Emotional Intelligence Allows Us to Understand and Regulate Our Emotional and Social Lives (cont.) Emotional intelligence is the ability to recognize and regulate our own and other�s emotions (Gohm, 2003; Mayer & Salovey, 1997). Individuals with high emotional intelligence are attentive to their own feelings, can accurately discriminate between them, and can use this information to guide their own thinking and actions (Mayer et al., 2000; Salovey et al., 2003). Emotionally intelligent people are also aware of the emotional states of others (Goleman, 1995).

27. 10-3a Neuroscientists Try to Link Differences in Intelligence to Dissimilarities in People�s Brains Brain anatomy Francis Galton believed that intelligence was related to the size of a person�s head. More recent studies have found a small correlation (r = +.15) between head size and intelligence scores. Yet, because there is more inside the skull than just brain tissue, skull size is not a very accurate measure of brain size. When magnetic resonance imaging (MRI) scans directly measure brain volume, the resulting brain size and IQ score correlation increases to a moderately high +.44.

28. 10-3a Neuroscientists Try to Link Differences in Intelligence to Dissimilarities in People�s Brains (cont.) What explains the +.44 correlation between brain size and IQ score? People with bigger brains are known to have more neurons (Pakkenberg & Gunderson, 1997), and the greater number of neural connections may result in a correspondingly greater cognitive capacity (Vernon et al., 2000). However, men on average have about 4 billion more neurons than women, but they do not outscore them on IQ tests (Pakkenberg & Gunderson, 1997). Archeological records indicate that Neanderthals had larger brains than modern humans, but no scientist has suggested that our extinct hominid cousins were more intelligent.

29. 10-3a Neuroscientists Try to Link Differences in Intelligence to Dissimilarities in People�s Brains (cont.) Brain size-IQ correlation could be related to different levels of myelin in the brain (Miller, 1994). Scientific research suggests that intelligence is associated with specific areas of the brain and not the brain as a whole.

30. 10-3a Neuroscientists Try to Link Differences in Intelligence to Dissimilarities in People�s Brains (cont.) Brain functioning Intelligence might be related to myelin. IQ scores tend to be correlated with the complexity of electrical activity in the brain. When responding to simple stimuli, high scorers have more complex brain patterns than low scorers (Barrett & Eysenck, 1992; Caryl, 1994). The speed at which neural impulses travel is positively correlated with IQ (+.40). This finding suggests that intelligent people are literally more quick-witted than less intelligent people (McGarry-Roberts et al., 1992; Vernon & Mori, 1992).

31. 10-3a Neuroscientists Try to Link Differences in Intelligence to Dissimilarities in People�s Brains (cont.) Smarter brains are not only quick and complex, but are also efficient (Jausovek & Jausovek, 2003). While working on problem-solving tasks, intelligent participants� brains consumed less glucose (Haier et al., 1992, 1995). The brains of intelligent people become more efficient with practice than the brains of those with less intelligence (Haier et al., 1992, 1995).

32. Figure 10-8 An Inspection Time Task

33. 10-3b Intelligence Becomes More Stable with Age, but It Is Far from Fixed Joseph Fagan (1992) has devised an indirect intellectual assessment technique that tests infants� preferences for visual novelty. Findings indicate that babies between the ages of 2 and 7 months who spend more time looking at the novel stimuli later tend to score higher than others on childhood intelligence tests (McCall & Carriger, 1993). Although this simple measure of infant attention and processing is not a true intelligence test in the classic sense, it does appear useful in identifying children who are later likely to score very high or very low on conventional intelligence tests.

34. Figure 10-9 The Stabilization of IQ Scores with Age When IQ scores obtained at age 17 are plotted with IQ scores obtained at earlier ages, the correlations before the ages of 5 or 6 are far below .50, but they rise in the range of .70 to .80 by the time children are 7 and 8 years old.

35. 10-3b Intelligence Becomes More Stable with Age, but It Is Far from Fixed (cont.) Most contemporary researchers believe that intelligence is pliable and that the thinking skills associated with IQ scores can be improved through learning. One of the more impressive intellectual-skills training programs ever developed was Project Intelligence, which was implemented in Venezuela during the 1980s.

36. 10-3c The �Challenged� and the �Gifted� Are the Two Extremes of Intelligence Mental retardation A diagnostic category used for people who not only have an IQ score below 70 but also have difficulty adapting to the routine demands of independent living (Detterman et al., 2000). According to the American Psychiatric Association (1994), only about 1 to 2 percent of the population meets both criteria for inclusion in the mental retardation category.

37. 10-3c The �Challenged� and the �Gifted� Are the Two Extremes of Intelligence (cont.) In about 25 percent of cases, doctors are able to identify a specific organic cause of retardation (Yeargin-Allsopp et al., 1997). Organic conditions are infections or malnutrition of the pregnant mother or infant, poisoning of the developing fetus or infant child by harmful substances (such as alcohol or lead), premature birth, and trauma to the child�s head. Also included among organic causes are genetic disorders, the most common being Down syndrome. Down syndrome is a form of mental retardation caused by an extra chromosome in one�s genetic makeup.

38. 10-3c The �Challenged� and the �Gifted� Are the Two Extremes of Intelligence (cont.) Mental giftedness Some psychologist define �gifted� as those individuals whose IQ is above 130 or 135. Other psychologists supplement this criterion with other requirements, such as exceptional school or career achievement. U.S. federal law designates that giftedness should be based on superior potential in any of the following six areas (Callahan, 2000): General intelligence Specific aptitudes Performing arts Athletics Creativity Leadership

39. 10-3c The �Challenged� and the �Gifted� Are the Two Extremes of Intelligence (cont.) One concern regarding gifted students has been that they are not adequately challenged by the regular school curriculum (Gottfried et al., 1994; Keen & Howard, 2002). To address this concern, educators have developed two separate intervention strategies: Acceleration involves early admission to school and encouraging gifted students to skip grades. Enrichment involves keeping gifted students in their normal grade level, but supplementing their course-work with advanced material, independent study projects, and other special learning experiences.

40. 10-4a Twin and Adoption Studies Indicate That Both Genes and Environment Influence Intelligence Psychologists and behavior geneticists who study the heritability of intelligence express the degree to which heredity determines intelligence within a particular human group in terms of a heritability coefficient. The heritability coefficient is a statistical coefficient, ranging from 0 to 1, that estimates the degree to which heredity determines intelligence within a particular human group.

41. 10-4a Twin and Adoption Studies Indicate That Both Genes and Environment Influence Intelligence (cont.) Twin studies Fraternal twins have more similar IQ scores than do other siblings. In addition, nontwin siblings raised together have more similar IQs (r = .47) than siblings raised apart (r = .24). Genetically oriented researchers respond that identical twins raised apart still have higher IQ correlations (r = .72) than fraternal twins raised together (r = .60). Perhaps the high IQ correlations among identical twins separated at birth are due to early shared environment, as well as to shared genes.

42. Figure 10-10 Studies of IQ Similarity: The Nature-Nurture Debate The results of over 100 studies correlating the IQ scores for people with different genetic and environmental backgrounds found that the most genetically similar people had the most similar IQ scores.

43. 10-4a Twin and Adoption Studies Indicate That Both Genes and Environment Influence Intelligence (cont.) Adoption studies Given the competing ways in which twin study findings can be interpreted as supporting either genetic or environmental effects on IQ, researchers turned to adoption studies to determine if nature or nurture influenced intelligence. Children who were adopted within two weeks to one year of birth were later found to have higher IQ correlations with their biological parents (Horn, 1983; Scarr & Weinberg, 1983; Turkheimer, 1991). Other adoption studies have found that when lower-class children are adopted by upper-class parents, IQ scores for these children range between 104 and 111, whereas the average score for their brothers and sisters who remained in the lower-class household ranged between 92 and 95 (Capron & Duyme, 1989; Schiff et al., 1978).

44. Figure 10-11 Reaction RangeReaction range indicates the extent to which the environment can raise or lower IQ scores, given the preexisting hereditary limits. People who grow up in enriched environments should score at the top of their reaction range. People who grow up in impoverished settings should score closer to the bottom of their range.

45. 10-4b There Are Group Differences in IQ Scores Gender differences Females tend to do better on verbal aptitude tests, such as naming synonyms and verbal fluency (Law et al., 1993; Stanley, 1993). Males tend to do better on visual-spatial tests, such as mental rotation and tracking a moving object (Law et al., 1993; Stanley, 1993). On the 60-item SAT math test, male high school seniors tend to average about four more correct answers than their female counterparts (Halpern, 2000; Held et al., 1993), and many more males score in the highest ranges. Although the gender differences in verbal and spatial abilities are substantial, the math differences are relatively small and disappearing (Feingold, 1992; Hyde et al., 1990; Masters & Sanders, 1993).

46. 10-4b There Are Group Differences in IQ Scores (cont.) Racial differences In the United States, African Americans score between 10 and 15 points lower on intelligence tests than White Americans, whose IQ averages are about 100 (Bracken et al., 1993; Williams & Ceci, 1997). Asian Americans score about 5 points higher than Whites (Lynn, 1996; McShane & Plas, 1984). The average intelligence scores of Hispanic Americans fall between the African-American scores and the White and Asian scores (Lynn, 1996; McShane & Plas, 1984).

47. Figure 10-13 Racial Differences in IQ ScoresAs you can see by examining the graph, the IQ variation within these groups is much greater than the differences among their average IQ scores.

48. 10-4b There Are Group Differences in IQ Scores (cont.) Arthur Jensen claims that between one-half and three-fourths of the average IQ difference found between African Americans and White Americans is attributable to genetic factors (Jensen, 1973, p. 363). Sandra Scarr and Richard Weinberg (1976) found that adopted African-American children had an average IQ of over 20 points higher than children who were raised in their original lower-class homes.

49. 10-4c Genetic Explanations of Group IQ Score Differences Remain Highly Controversial Richard Herrnstein and Charles Murray published The Bell Curve: Intelligence and Class Structure in American Life in 1994. Based on their review of other researchers� work, these authors claimed the following: Intelligence is largely inherited. Intelligence overwhelmingly determines socioeconomic status. The nation�s intelligence level is declining because low-IQ people are having more children than high-IQ people. Intellectual-training programs will do little to help the poor.

50. 10-4c Genetic Explanations of Group IQ Score Differences Remain Highly Controversial (cont.) Herrnstein and Murray�s proposals were strongly challenged by many psychologists, who charged that a great deal of The Bell Curve reasoning was flawed and based on selective review of past research. Critics argue that a fatal flaw in Herrnstein and Murray�s group heritability estimates of racial differences in intelligence is that they are based on the heritability estimates derived from twin studies. As the analogy in Figure 10-14 illustrates, the fact that IQ differences within groups are partly, or even completely, caused by genetic variation does not mean that average IQ differences between groups are due to genetics (Block, 2002).

51. Figure 10-14 Between-Group and Within-Group VariationsIn our corn seed analogy, all the variation in plant height within each field is due to genetics, but the overall height difference between the corn plants in the fertile field and the barren field is due to the environment.

52. 10-4c Genetic Explanations of Group IQ Score Differences Remain Highly Controversial (cont.) In the United States, African Americans and Hispanics do not generally grow up in the same environments as Whites. Due to the dissimilarity in environments, critics of The Bell Curve correctly argue that it is a mistake to assume that IQ differences between Whites and different minority groups stem from genetic factors.

53. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences Voluntary minorities are people who have freely come to the United States. Voluntary minorities include immigrants from Africa, the Caribbean, Mexico, South America, China, India, Japan, and Korea. Involuntary minorities are people who are a part of the United States because their ancestors were conquered, colonized, or enslaved. Involuntary minorities include Native Americans, most African Americans, early Mexicans in the Southwest, native Hawaiians, Alaskan natives, and Puerto Ricans.

54. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences (cont.) Numerous studies indicate that involuntary minorities in the United States achieve lower IQ scores than voluntary minorities (Brand, 1996; Suzuki & Gutkin, 1994a, 1994b). Primary causes may be: Persisting negative cultural stereotypes within the dominant culture concerning involuntary minorities� intellectual abilities (Ogbu, 2002; Serpell, 2000; Shimahara et al., 2001) The self-protective defensive reaction many involuntary minority members subsequently develop against the rejecting mainstream culture (Ogbu, 2002; Serpell, 2000; Shimahara et al., 2001)

55. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences (cont.) Oppositional identities Anthropologist John Ogbu (1986, 1993, 2002) believes that some members of involuntary minority groups respond to negative stereotypes and discrimination by developing an oppositional ethnic identity and cultural frame of reference that defensively opposes the rejecting dominant culture. One of the most immediate benefits is that an oppositional identity can psychologically insulate a person from some of the negative effects of social injustice, such as loss of self-esteem. On the negative side, however, immersion in an identity that defines itself in terms of opposition to the larger culture will likely constrict your personal identity.

56. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences (cont.) Stereotype threat is the realization that your performance on some task might confirm the negative stereotype. According to Steele, when highly motivated African-American students take an intelligence test while simultaneously worrying that a low score will confirm that they fit the �mentally inferior� stereotype, this added pressure is often sufficient to significantly hinder their performance. When a test was presented as a measure of ability, Blacks performed worse than Whites. However, when it was not associated with ability, no significant racial differences were found.

57. Figure 10-15 African-American Intellectual Test Performance and Stereotype Threat

58. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences (cont.) Valuing academic achievement Elementary schoolchildren in Taiwan and Japan outscore American children by about 15 points in math ability and, to a lesser extent, in reading skills. Interviews with the parents of these children found that the Chinese and Japanese parents downplayed the importance of innate intellectual ability, and instead stressed hard work (Stevenson et al., 1986). These same parents also considered doing well in school the most important goal for their children.

59. 10-4d Cultural and Social Psychological Factors May Explain Group IQ Differences (cont.) In contrast, American parents were more likely to believe that intelligence is genetically determined, and they assigned academic achievement as a much lower-valued goal for their children. Follow-up studies found that the achievement differences between Asian and American children persisted through high school (Stevenson et al., 1993).

60. 10-4e Intellectual Ability Can Be Shaped by Self-Fulfilling Prophecies In 1948, the sociologist Robert Merton introduced the concept of the self-fulfilling prophecy to describe a situation in which someone�s expectations about a person or group actually lead to the fulfillment of those expectations. Research indicates that behavior changes due to self-fulfilling prophecies can be permanent and can markedly change the course of an individual�s life (Smith et al., 1999).

61. Figure 10-16The Development of a Self-Fulfilling Prophecy