- How intelligence is measured
- The characteristics of a good measure of intelligence
- The benefits of testing for intelligence
- The criticism of intelligence testing
Contrast intelligence theories, from early theories to more contemporary ideas on intelligence.
Format your presentation consistent with APA guidelines.
Gateway THEME Measuring intelligence is worthwhile, but tests provide limited definitions of intelligent behavior.
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Unlike other species, humans owe their success more to thinking abilities and intelligence than to physical strength or speed. That’s why our species is called Homo sapiens (from the Latin for man and wise). Our intelligence makes us highly adaptable creatures. We live in deserts, jungles, mountains, frenzied cities, placid retreats, and space stations.
Consider Stephen Hawking. He can’t walk or talk. When he was 13, Lou Gehrig’s disease began to slowly destroy nerve cells in his spinal cord, short-circuiting messages between his brain and muscles. Today, he is confined to a wheelchair and “speaks” by manually controlling a speech syn- thesizer. Yet, despite his severe disabilities, his brain is unaffected by the disease and remains fiercely active. He can still think. Stephen is a theoretical physicist and one of the best-known sci- entific minds of modern times. With courage and determination, he has used his intellect to advance our understanding of the universe.
What do we mean when we say that a person like Stephen Hawking is “smart” or “intelligent”? Can intelligence be measured? Can intelligence tests predict life success? What are the conse- quences of having extremely high or low intelligence? These questions and others concerning intelligence have fascinated psychologists for more than 100 years. Let’s see what has been learned and what issues are still debated.
Gateway QUESTIONS 9.1 How do psychologists define intelligence? 9.2 What are typical IQ tests like? 9.3 How do IQ scores relate to sex, age, and
occupation? 9.4 What does IQ tell us about genius?
9.5 What causes intellectual disability? 9.6 How do heredity and environment affect
intelligence? 9.7 Are there alternate views of intelligence? 9.8 Is there a downside to intelligence testing?
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Defining Intelligence— Intelligence Is … You Know, It’s …
Gateway Question 9.1: How do psychologists define intelligence? Like many important concepts in psychology, intelligence cannot be observed directly. Nevertheless, we feel certain it exists. Let’s compare two children:
When she was 14 months old, Anne wrote her own name. She taught her- self to read at age 2. At age 5, she astounded her kindergarten teacher by bringing an iPad to class—on which she was reading an encyclopedia. At 10, she breezed through an entire high school algebra course in 12 hours.
Billy, who is 10 years old, can write his name and can count, but he has trouble with simple addition and subtraction problems and finds multipli- cation impossible. He has been held back in school twice and is still incapa- ble of doing the work his 8-year-old classmates find easy.
Anne is considered a genius; Billy, a slow learner. There seems little doubt that they differ in intelligence.
Wait! Anne’s ability is obvious, but how do we know that Billy isn’t just lazy? That’s the same question that Alfred Binet faced in 1904 (Benjafield, 2010; Jarvin & Sternberg, 2003). The French minister of education wanted to find a way to distinguish slower students from the more capable (or the capable but lazy). In a flash of bril- liance, Binet and an associate created a test made up of “intellec- tual” questions and problems. Next, they learned which questions an average child could answer at each age. By giving children the test, they could tell whether a child was performing up to his or her potential (Kaplan & Saccuzzo, 2009; Kaufman, 2000).
Binet’s approach gave rise to modern intelligence tests. At the same time, it launched an ongoing debate. Part of the debate is related to the basic difficulty of defining intelligence (Sternberg, Grigorenko, & Kidd, 2005).
Defining Intelligence Isn’t there an accepted definition of intelligence? Traditionally, yes. Intelligence is the global capacity to act purposefully, to think rationally, and to deal effectively with the environment (Wechsler, 1939). The core of intelligence is usually thought to consist of a small set of general mental abilities (called the g-factor) in the areas of reasoning, problem solving, knowledge, memory, and successful adaptation to one’s surroundings (Barber, 2010; Sternberg, 2004).
Intelligence has traditionally been considered a cognitive, not an emotional, capacity. Is there such a thing as emotional intelligence? To find out, see Chapter 10, pages 363–364.
Beyond this, however, there is much disagreement. In fact, many psychologists simply accept an operational definition of intelligence by spelling out the procedures they use to measure it (Neukrug & Fawcett, 2010). Thus, by selecting items for an intel- ligence test, a psychologist is saying in a very direct way, “This is
what I mean by intelligence.” A test that measures memory, reason- ing, and verbal fluency offers a very different definition of intelli- gence than one that measures strength of grip, shoe size, length of the nose, or the person’s best Guitar Hero score (Goldstein, 2011).
Aptitudes As a child, Hedda displayed an aptitude for art. Today, Hedda is a successful graphic artist. How does an aptitude like Hedda’s differ from general intelligence? An aptitude is a capacity for learning certain abilities. Persons with mechanical, artistic, or musical apti- tudes are likely to do well in careers involving mechanics, art, or music, respectively (• Figure 9.1).
Are there tests for aptitudes? How are they different from intelli- gence tests? Aptitude tests measure a narrower range of abilities than do intelligence tests (Kaplan & Saccuzzo, 2009). For example, special aptitude tests predict whether you will succeed in a single
RANGE OF ABILITIES
Multiple aptitude tests
Special aptitude tests
Modern intelligence tests are widely used to measure cognitive abilities. When properly administered, such tests provide an operational definition of intelligence.
• Figure 9.1 Special aptitude tests measure a person’s potential for achieve- ment in a limited area of ability, such as manual dexterity. Multiple aptitude tests measure potentials in broader areas, such as college work, law, or medicine. Intelli- gence tests measure a very wide array of aptitudes and mental abilities.
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9781285519517, Introduction to Psychology: Gateways to Mind and Behavior with Concept Maps and Reviews, Thirteenth Edition, Coon/Mitterer – © Cengage Learning. All rights reserved. No distribution allowed without express authorization.
Intelligence An overall capacity to think rationally, act purposefully, and deal effectively with the environment.
g-factor A general ability factor proposed to underly intelligence; the core of general intellectual ability that involves reasoning, problem-solving ability, knowledge, and memory.
Operational definition The operations (actions or procedures) used to measure a concept.
Aptitude A capacity for learning certain abilities. Special aptitude test Test to predict a person’s likelihood of succeeding in
a particular area of work or skill. Multiple aptitude test Test that measures two or more aptitudes. General intelligence test A test that measures a wide variety of mental
abilities. Psychometric test Any scientific measurement of a person’s mental
functions. Reliability The ability of a test to yield the same score, or nearly the same
score, each time it is given to the same person. Validity The ability of a test to measure what it purports to measure. Objective test A test that gives the same score when different people
correct it. Test standardization Establishing standards for administering a test and
interpreting scores. Norm An average score for a designated group of people.
area, such as clerical work or computer programming (• Figure 9.2). Multiple aptitude tests measure two or more types of ability. These tests tend to be more like intelligence tests. The well-known SAT Reasoning Test (SAT), which measures aptitudes for language, math, and reasoning, is a multiple aptitude test. So are the tests required to enter graduate schools of law, medicine, business, and dentistry. The broadest aptitude measures are general intelligence tests, which assess a wide variety of mental abilities (Cohen & Swerdlik, 2005).
Psychologists use a variety of aptitude tests to select people for employment and to advise people about choosing careers. For more information, see Chapter 18, pages 608–611.
Reliability and Validity Whether it is an intelligence test or aptitude test or, for that matter, any other kind of psychometric test—any measurement of a per- son’s mental functions—there will always be two questions you should ask about the test: “Is it reliable?” and “Is it valid? ”
To what does reliability refer? If you weigh yourself several times in a row, a reliable bathroom scale gives the same weight each time. Likewise, a reliable psychometric test must give approximately the same score each time a person takes it (Kaplan & Saccuzzo, 2009). In other words, the scores should be consistent and highly corre- lated. It is easy to see why unreliable tests have little value. Imagine a medical test for pregnancy or breast cancer, for instance, which gives positive and negative responses for the same woman on the same day.
To check the reliability of a test, we could give it to a large group of people. Then, each person could be tested again a week later to establish test-retest reliability. We also might want to know whether scores on one half of the test items match scores on the other half (split-half reliability). If two versions of a test are avail-
able, we could compare scores on one version to scores on the other (equivalent-forms reliability).
Just because a psychometric test is reliable, however, does not mean that it should be trusted; test validity is also important. To see why this is the case, try creating an IQ test with ten questions only you could possibly answer. Your test would be very reliable. Each time you give the test, everyone scores zero, except you, who scores 100 percent (so you thereby proclaim yourself the only human with any intelligence). Even though we all have days when it seems we are the only smart person left on the planet, it should be obvious this is a silly example. A test must also have validity; it should measure what it claims to measure (Neukrug & Fawcett, 2010). By no stretch of the imagination could a test of intelligence be valid if the person who wrote it is the only one who can pass it.
How is validity established? Validity is usually demonstrated by comparing test scores to actual performance. This is called criterion validity. For example, scores on a test of legal aptitude might be com- pared with grades in law school. If high test scores correlate with high grades, or some other standard (criterion) of success, the test might be valid. Unfortunately, many “free” tests you encounter, such as those found in magazines and on the Internet, have little or no validity.
Objective Testing Let’s return to your “I’m the Smartest Person in the World IQ Test” for a final point. Is your test objective? Actually, it might be. If your IQ test gives the same score when corrected by different people, it is an objective test. However, objectivity is not enough to guaran- tee a fair test. Useful tests must also be standardized (Neukrug & Fawcett, 2010).
Test standardization refers to two things. First, it means that standard procedures are used in giving the test. The instructions, answer forms, amount of time to work, and so forth, are the same for everyone. Second, it means finding the norm, or average score,
1. If the driver turns in the direction shown, which direction will wheel Y turn? A B
2. Which wheel will turn the slowest? Driver X Y
• Figure 9.2 Sample questions like those found on tests of mechanical apti- tude. (The answers are A and the Driver.)
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made by a large group of people like those for whom the test was designed. Without standardization, we couldn’t fairly compare the scores of people taking the test at different times. And without norms, there would be no way to tell whether a score is high, low, or average.
Later in this chapter, we will address the question of whether intelligence tests are valid. For now, let’s take a practical approach and learn about some popular standardized IQ tests.
Testing Intelligence—The IQ and You
Gateway Question 9.2: What are typical IQ tests like? American psychologists quickly saw the value of Alfred Binet’s test. In 1916, Lewis Terman and others at Stanford University revised it for use in North America. After more revisions, the Stanford-Binet Intelligence Scales, Fifth Edition (SB5) continue to be widely used. The original Stanford-Binet assumed that a child’s intellectual abilities improve with each passing year. Today, the Stanford-Binet (or SB5) is still primarily made up of age-ranked questions. Naturally, these questions get a little harder at each age level. The SB5 is appropriate for people from age 2 to 85� years and scores on the test are very reliable (Raid & Tippin, 2009; Roid, 2003).
Five Aspects of Intelligence The SB5 measures five cognitive factors (types of mental abilities) that make up general intelligence. These are fluid reasoning, knowl- edge, quantitative reasoning, visual-spatial processing, and working memory. Each factor is measured with verbal questions (those involving words and numbers), and nonverbal questions (items that use pictures and objects). Let’s see what each factor looks like.
Fluid Reasoning Questions like the following are used to test Fluid Reasoning:
How are an apple, a plum, and a banana different from a beet? An apprentice is to a master as a novice is to an ____________. “I knew my bag was going to be in the last place I looked, so I
looked there first.” What is silly or impossible about that?
Other items ask people to fill in the missing shape in a group of shapes, and to tell a story that explains what’s going on in a series of pictures.
Knowledge The Knowledge factor assesses the person’s knowledge about a wide range of topics.
Why is yeast added to bread dough? What does cryptic mean? What is silly or impossible about this picture? (For example, a
bicycle has square wheels.)
Quantitative Reasoning Test items for Quantitative Reasoning measure a person’s ability to solve problems involving numbers. Here are some samples:
If I have six marbles and you give me another one, how many marbles will I have?
Given the numbers 3, 6, 9, 12, what number would come next? If a shirt is being sold for 50 percent of the normal price, and
the price tag is $60, what is the cost of the shirt?
Visual-Spatial Processing People who have visual-spatial skills are good at putting picture puzzles together and copying geometric shapes (such as triangles, rectangles, and circles). Visual-Spatial Processing questions ask test takers to reproduce patterns of blocks and choose pictures that show how a piece of paper would look if it were folded or cut. Verbal questions can also require visual-spatial abilities:
Suppose that you are going east, then turn right, then turn right again, then turn left. In what direction are you facing now?
Working Memory The Working Memory part of the SB5 measures the ability to use short-term memory. Some typical memory tasks include the following:
Correctly remember the order of colored beads on a stick. After hearing several sentences, name the last word from each
sentence. Repeat a series of digits (forward or backward) after hearing
them once. After seeing several objects, point to them in the same order as
they were presented.
If you were to take the SB5, it would yield a score for your general intelligence, verbal intelligence, nonverbal intelligence, and each of the five cognitive factors (Bain & Allin, 2005). For another per- spective on the kinds of tasks used in the SB5, see “Intelligence— How Would a Fool Do It?”
The Wechsler Tests Is the Stanford-Binet the only intelligence test? Many other IQ tests have been developed. Psychologist David Wechsler (1939) designed one widely used alternative. Whereas the original Stanford-Binet was better suited for children and adolescents, the first Wechsler test was specifically designed to test adult intelligence. The current version is the Wechsler Adult Intelli- gence Scale—Fourth Edition (WAIS-IV). With newer versions of the Stanford-Binet and a children’s version of the Wechsler scales (currently the Wechsler Intelligence Scale for Children— Fourth Edition or WISC-IV; see Baron, 2005), both alternatives are now widely used across all ages.
Performance intelligence Intelligence measured by solving puzzles, assembling objects, completing pictures, and other nonverbal tasks.
Verbal intelligence Intelligence measured by answering questions involving vocabulary, general information, arithmetic, and other language- or symbol-oriented tasks.
Individual intelligence test A test of intelligence designed to be given to a single individual by a trained specialist.
Group intelligence test Any intelligence test that can be administered to a group of people with minimal supervision.
Like the Stanford-Binet, the Wechsler tests yield a single overall intelligence score. In addition, these tests also separate scores for performance (nonverbal) intelligence and verbal (language- or symbol-oriented) intelligence. The abilities measured by the Wechsler tests and some sample test items are listed in ■ Table 9.1.
Group Tests The SB5 and the Wechsler tests are individual intelligence tests, which are given to a single person by a trained specialist. In con- trast, group intelligence tests can be given to a large group of people with minimal supervision. Group tests usually require people to read, to follow instructions, and to solve problems of logic, reasoning, mathematics, or spatial skills. The first group intelligence test was the Army Alpha, developed for World War I military inductees. As you can see in ■ Table 9.2, intelligence test- ing has come a long way since then.
Scholastic Aptitude Tests If you’re wondering if you have ever taken an intelligence test, the answer is probably yes. As mentioned earlier, the SAT Reasoning Test is a multiple aptitude test. So are the American College Test (ACT) and the College Qualification Test (CQT). Each of these group tests is designed to predict your chances for success in col-
Adapted from Wechsler, D. (2008). Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV). San Antonio, TX: Pearson.
Sample Items Similar to Those Used on the WAIS-IV
Verbal Comprehension Sample Items or Descriptions
Similarities In what way are a wolf and a coyote alike?
In what way are a screwdriver and a chisel alike?
Vocabulary The test consists of asking, “What is a ____________?” or “What does ____________ mean?” The words range from more to less familiar and difficult.
Information How many wings does a butterfly have?
Who wrote Romeo and Juliet?
Block Design Copy designs with blocks (as shown at right).
Matrix Reasoning Select the item that completes the matrix.
Visual Puzzles Choose the pieces which go together to form a figure.
Digit Span Repeat from memory a series of digits, such as 8 5 7 0 1 3 6 2, after hearing it once.
Arithmetic Four girls divided 28 jellybeans equally among themselves. How many jellybeans did each girl receive?
If 3 peaches take 2 minutes to find and pick, how long will it take to find and pick a dozen peaches?
Symbol Search Match symbols appearing in separate groups.
Coding Fill in the symbols: 3 21244 1 31 2 3 4
X III I 0
■ TABLE 9.1
Intelligence—How Would a Fool Do It?Human Diversity
You have been asked to sort some objects into categories. Wouldn’t it be smart to put the clothes, containers, implements, and foods in separate piles? Not necessarily. When members of the Kpelle culture in Libe- ria were asked to sort objects, they grouped them together by function. For example, a potato (food) would be placed together with a knife (implement). When the Kpelle were asked why they grouped the objects this way, they often said that was how a wise man would do it. The researchers finally asked the Kpelle, “How would a fool do it?” Only then did the Kpelle sort the objects into the nice, neat categories that we Westerners prefer.
This anecdote, related by cultural psy- chologist Patricia Greenfield (1997), raises serious questions about general definitions of intelligence. For example, among the Cree of northern Canada, “smart” people are the ones who have the skills needed to find food on the frozen tundra (Darou, 1992). For the Puluwat people in the South Pacific, smart means having ocean-going naviga- tion skills necessary to get from island to is- land (Sternberg, 2004). And so it goes, as each culture teaches its children the kinds of “intelligence” valued in that culture— how the wise man would do it, not the fool (Barber, 2010; Correa-Chávez, Rogoff, & Arauz, 2005).
How important do you think the mental abilities assessed in modern intelligence tests are to this Bushman hunter in Africa’s Kalahari Desert?
Items from the Army Alpha Subtest on “Common Sense”
The Army Alpha was given to World War I army recruits in the United States as a way to identify potential officers. In these sample questions, note the curious mixture of folk wisdom, scientific information, and moralism (Kessen & Cahan, 1986). Other parts of the test were more like modern intelligence tests.
1. If plants are dying for lack of rain, you should
h water them
h ask a florist’s advice
h put fertilizer around them
2. If the grocer should give you too much money in making change, what is the right thing to do?
h buy some candy for him with it
h give it to the first poor man you meet
h tell him of his mistake
3. If you saw a train approaching a broken track you should
h telephone for an ambulance
h signal the engineer to stop the train
h look for a piece of rail to fit in
4. Some men lose their breath on high mountains because
h the wind blows their breath away
h the air is too rare
h it is always cold there
5. We see no stars at noon because
h they have moved to the other side of the earth
h they are much fainter than the sun
h they are hidden behind the sky
■ TABLE 9.2
Copyright © 2013 Cengage Learning, Inc.
Mental age The average mental ability displayed by people of a given age. Chronological age A person’s age in years. Intelligence quotient (IQ) An index of intelligence defined as mental age
divided by chronological age and multiplied by 100. Deviation IQ An IQ obtained statistically from a person’s relative standing
in his or her age group; that is, how far above or below average the person’s score was relative to other scores.
lege. Because the tests measure general knowledge and a variety of mental aptitudes, each can also be used to estimate intelligence.
Intelligence Quotients What is an “IQ”? Imagine that a child named Yuan can answer intelligence test questions that an average 7-year-old can answer. We could say that 7 is her mental age (average intellectual perfor- mance). How smart is Yuan? Actually, we can’t say yet, because we don’t know how old Yuan is. If she is 10, she’s not very smart. If she’s 5, she is very bright. Thus, although mental age is a good measure of actual ability, it says nothing about whether overall intelligence is high or low, compared with other people of the same age.
Thus, to estimate a child’s intelligence, we also need to know her chronological age (age in years). Then, we can relate mental age to chronological age. This yields an IQ, or intelligence quotient. A quotient results from dividing one number into another. When the Stanford-Binet was first used, IQ was defined as mental age (MA) divided by chronological age (CA) and multiplied by 100. (Multi- plying by 100 changes the IQ into a whole number rather than a decimal.)
� 100 � IQ
An advantage of the original IQ was that intelligence could be compared among children with different chronological and mental ages. For instance, 10-year-old Justin has a mental age of 12. Thus, his IQ is 120:
1MA2 12 1CA2 10
� 100 � 120 (IQ)
Justin’s friend Suke also has a mental age of 12. However, Suke’s chronological age is 12, so his IQ is 100:
1MA2 12 1CA2 12
� 100 � 100 (IQ)
The IQ shows that 10-year-old Justin is brighter than his 12-year- old friend Suke, even though their intellectual skills are about the same. Notice that a person’s IQ will be 100 when mental age equals chronological age. Therefore, an IQ score of 100 is defined as aver- age intelligence.
Then does a person with an IQ score below 100 have below average intelligence? Not unless the IQ is well below 100. Average intelli- gence is usually defined as any score from 90 to 109. The impor- tant point is that IQ scores will be over 100 when mental age is higher than age in years. IQ scores below 100 occur when a per- son’s age in years exceeds his or her mental age. An example of this situation would be a 15-year-old with an MA of 12:
� 100 � 80 (IQ)
Deviation IQs Although the preceding examples may give you insight into IQ scores, it’s no longer necessary to directly calculate IQs. Instead, modern tests use deviation IQs. Tables supplied with the test are used to convert a person’s relative standing in the group to an IQ score. That is, they tell how far above or below average the person’s score falls. For example, if you score at the 50th percentile, half the people your age who take the test score higher than you and half score lower. In this case, your IQ score is 100. If you score at the 84th percentile, your IQ score is 115. If you score at the 97th per- centile, your IQ score is 130. (For more information, see the Statis- tics appendix near the end of this book.)
OK, so how does Stephen Hawking score? When Hawking was once asked about his IQ, he claimed he didn’t know and joked, “People who boast about their IQ are losers.”
The Stability of IQ How old do children have to be before their IQ scores become stable? IQ scores are not very dependable until about age 6 (Schuerger & Witt, 1989). IQ scores measured at age 3 correlate poorly with those measured at age 27. In other words, knowing a child’s IQ at age 3 tells us very little about what his or her IQ will be 24 years later. (Recall that a perfect correlation is 1.00 and a correlation of 0.00 occurs when scores are unrelated.) However, IQs do become more reliable as children grow older. Knowing a child’s IQ at age 11 is a good predictor of his or her IQ later in life (Gow et al., 2010). After middle childhood, a person’s IQ scores usually change very little from year to year (Canivez & Watkins, 1998; Gow et al., 2010; Larsen, Hartmann, & Nyborg, 2008). (See • Figure 9.3).
Variations in Intelligence— The Numbers Game
Gateway Question 9.3: How do IQ scores relate to sex, age, and occupation? IQ scores are classified as shown in ■ Table 9.3. A look at the per- centages reveals a definite pattern. The distribution (or scattering) of IQ scores approximates a normal (bell-shaped) curve. That is, most
15 27 39 51
0.6 3 63 75 87
• Figure 9.3 The stability or reliability of IQ scores increases rapidly in early childhood. Scores are very consistent from early adulthood to late middle age. (Adapted from Gow et al., 2010; Larsen, Hart- mann, & Nyborg, 2008; Schuerger & Witt, 1989.)
Distribution of Adult IQ Scores on the WAIS-IV
IQ Description Percent
Above 130 Very superior 2.2
120–129 Superior 6.7
110–119 Bright normal 16.1
90–109 Average 50.0
80–89 Dull normal 16.1
70–79 Borderline 6.7
Below 70 Intellectually disabled 2.2
■ TABLE 9.3
Derived from Wechsler, D. (2008). Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV). San Antonio, TX: Pearson.
Knowledge Builder Intelligence Tests
RECITE 1. The first successful intelligence test was developed by
__________________________________. 2. If we define intelligence by the obtained score on a written test, we
are using a. a circular definition b. an abstract definition c. an operational
definition d. a chronological definition 3. Place an “R” or a “V” after each operation to indicate whether it would
be used to establish the reliability (R) or the validity (V) of a test. a. Compare score on one half of test items to score on the other
half. ( ) b. Compare scores on test to grades, performance ratings, or other
measures. ( ) c. Compare scores from the test after administering it on two sepa-
rate occasions. ( ) d. Compare scores on alternate forms of the test. ( )
4. Establishing norms and uniform procedures for administering a test are elements of standardization. T or F?
5. The WAIS-IV is a group intelligence test. T or F? 6. IQ was originally defined as __________________ times 100. 7. Scores on modern intelligence tests are based on one’s deviation
IQ (relative standing among test takers) rather than on the ratio between mental age and chronological age. T or F?
REFLECT Think Critically
8. How well do you think a member of Kpelle culture in Liberia would score on the SB5?
If you were going to write an intelligence test, what kinds of questions would you ask? How much would your questions resemble those on standard intelligence tests? Would you want to measure any mental skills not covered by established tests?
Answers: 1. Alfred Binet 2. c 3. a. (R), b. (V), c. (R), d. (R) 4. T 5. F 6. MA/CA 7. T 8. You are right if you suspect the answer is most likely “poorly.” The more important question is what this means. Is the person “slow” or might there be some question about the test itself (Gardner, 2008; Hen- rich, Heine, & Norenzayan, 2010)? Stay tuned for more on this important issue.
Normal curve A bell-shaped curve characterized by a large number of scores in a middle area, tapering to very few extremely high and low scores.
Fluid intelligence The ability to solve novel problems involving perceptual speed or rapid insight.
Crystallized intelligence The ability to solve problems using already acquired knowledge.
scores fall close to the average and very few are found at the extremes. • Figure 9.4 shows this characteristic of measured intelligence.
IQ and Sex On average, do males and females differ in intelligence? IQ scores cannot answer this question because test items were selected to be equally difficult for both sexes. However, whereas males and females do not appear to differ in overall intelligence, general intel- ligence tests allow us to compare the intellectual strengths and weaknesses of men and women (Hyde, 2007). For decades, women, as a group, performed best on items that require verbal ability, vocabulary, and rote learning. Men, in contrast, were best at items that require spatial visualization and math (Clements et al., 2006; Calvin et al., 2010). Today, such male-female differences have almost disappeared among children and young adults. The small differences that remain appear to be based on a tendency for par- ents and educators to encourage males, more than females, to learn math and spatial skills (Ceci & Williams, 2010).
IQ and Age How much are IQs affected by age? Don’t be confused by • Figure 9.3. The rising curve in that figure indicates that the consistency of IQ scores from year to year increases with age. Actual IQ test scores stay relatively stable as people age with a small, gradual increase until about age 40 and a small slow decline therafter (Larsen, Hart- mann, & Nyborg, 2008; Thompson & Oehlert, 2010).
This trend, of course, is an average. Actual IQs reflect a person’s education, maturity, and experience, as well as innate intelligence. Some people make fairly large gains in IQ, whereas others have siz- able losses. How do the two groups differ? In general, those who gain in IQ are exposed to intellectual stimulation during early adulthood. Those who decline typically suffer from chronic ill- nesses, drinking problems, or unstimulating lifestyles (Honzik, 1984; Nisbett, 2009a,b).
After middle age, the picture gets a bit more complex. Intellec- tual skills involved in fluid intelligence—solving novel problems
involving perceptual speed or rapid insight—decline rapidly after middle age (Brody, 1992; Lawrence, Myerson, & Hale, 1998). By way of compensation, crystallized intelligence—solving prob- lems using already acquired knowledge —can actually increase or, at least, decline very little until advanced age. In other words, younger people are generally “quick learners” (fluid intelligence) but tend to be “wet behind the ears” (lack experience or crystalized intelligence). Older people might be a little “slower on the uptake” but tend to “know the ropes.” Since IQ tests such as the SB5 and WAIS test for components of both fluid intelligence and crystal- lized intelligence, overall, age-related losses are small for most healthy, well-educated individuals (Rindermann, Flores-Mendoza, & Mansur-Alves, 2010; Weintraub 2003).
IQ and Achievement How do IQ scores relate to success in school, jobs, and other endeav- ors? IQ differences of a few points tell us little about a person. But if we look at a broader ranges of scores, the differences do become meaningful. For example, a person with an IQ of 100 would probably struggle with college, whereas one with an IQ of 120 would do just fine.
The correlation between IQ and school grades is at least .50—a sizable association (Calvin et al., 2010; Mayes et al., 2009). If grades depended solely on IQ, the connection would be even stronger. However, motivation, special talents, off- campus educational opportunities, and many other factors influ- ence grades and school success. The same is true of “real world” success beyond school (Strenze, 2007). IQ is also not a good predictor of success in art, music, writing, dramatics, science, and leadership. Tests of creativity are much more strongly related to achievement in these areas (Kaufman, 2009; Preckel, Holling, & Wiese, 2006).
As you might expect, IQ is also related to job status. Persons holding white-collar, professional positions average higher IQs than those in blue-collar settings. For example, accountants, lawyers, and engineers average about 125 in IQ. In contrast, miners and farm workers average about 90 (Brody, 1992). It is important to note, however, that a range of IQ scores can be found in all occupations. Many people of high intelligence, because of choice or circumstance, have “low-ranking” jobs.
Does the link between IQ and occupation show that professional jobs require more intelligence? Not as clearly as you might think. Higher status jobs often require an academic degree. As a result, hiring for professional jobs is biased in favor of a particular type of intelligence, namely, the kind measured by intelligence tests
40 60 80 100 120 140 160 180
Mean = 101.8 IQ
• Figure 9.4 Distribution of Stanford-Binet Intelligence Test scores for 3184 children. (Adapted from Terman & Merrill, 1937/1960.)
(McClelland, 1994; Neisser et al., 1996). This bias probably inflates the apparent association between professional jobs and IQ. The more IQ-like tests are used to select people for jobs, the stronger the association between IQ and job status. In fact, it can be argued that high status groups use such tests to protect their “territory” (Tittle & Rotolo, 2000).
When IQs are extreme—below 70 or above 140—their link to an individual’s potential for success becomes unmistakable. Only about 3 percent of the population falls in these ranges. Nevertheless, millions of people have exceptionally high or low IQs. Discussions of the intellectually gifted and intellectually disabled follow.
The Intellectually Gifted—Smart, Smarter, Smartest
Gateway Question 9.4: What does IQ tell us about genius? How high is the IQ of a genius? Only 2 people out of 100 score above 130 on IQ tests. These bright individuals are usually described as “gifted.” Less than one-half of one percent of the population scores above 140. These people are certainly gifted or perhaps even “geniuses.” However, some psychologists reserve the term genius for people with even higher IQs or those who are exceptionally creative (Hallahan, Kauffman, & Pullen, 2011).
Gifted Children Do high IQ scores in childhood predict later ability? To directly answer this question, Lewis Terman selected 1,500 children with IQs of 140 or more. Terman followed this gifted group (the “Ter- mites,” as he called them) into adulthood. By doing so, Terman corrected several popular misconceptions about high intelligence (Dai, 2010; Reis & Renzulli, 2010; Shurkin, 1992).
Misconception: The gifted tend to be peculiar, socially backward people. Fact: On the contrary, Terman’s gifted subjects, and gifted people in
general, are socially skilled and above average in leadership (Feldhusen & Westby, 2003).
Misconception: Early ripe means later rot; the gifted tend to fizzle out as adults.
Fact: This is false. When they were retested as adults, Terman’s subjects again scored in the upper IQ ranges.
Misconception: The very bright are physically inferior “eggheads,” “nerds,” or weaklings.
Fact: As a group, the gifted were above average in height, weight, and physical appearance.
Misconception: Highly intelligent persons are more susceptible to mental illness (“Genius is next to insanity”).
Fact: Terman demonstrated conclusively that the gifted enjoy better than average mental health and a greater resistance to mental illness. In general, the highly gifted tend to be very well adjusted psychologically (Dai, 2010; Garland & Zigler, 1999).
Misconception: Intelligence has little to do with success, especially in practical matters.
Fact: The success of Terman’s subjects was striking. Far more of them than average completed college, earned advanced degrees, and held pro- fessional positions. As a group, the gifted produced dozens of books, thou- sands of scientific articles, and hundreds of short stories and other publications (Shurkin, 1992; Terman & Oden, 1959). As noted earlier, IQ scores are not generally good predictors of real-world success. However, when scores are in the gifted range, the likelihood of outstanding achieve- ment does seem to be higher.
Giftedness and Achievement Were all the Termites superior as adults? No. Remember that high IQ reveals potential. It does not guarantee success. As adults, some of Terman’s gifted subjects committed crimes, were unemployable, or were unhappy misfits. Nor does a lower IQ guarantee failure. Nobel prize-winning physicist Richard Feynman, whom many regard as a genius, had an IQ of 122 (Michalko, 2001).
How did Terman’s more successful Termites differ from the less successful? Most of them had educated parents who valued learning and encouraged them to do the same. In general, successful gifted persons tend to have strong intellectual determination—a desire to know, to excel, and to persevere (Winner, 2003). Gifted or not, most successful persons tend to be persistent and motivated to learn (Reis & Renzulli, 2010). No one is paid to sit around being capable of achievement. What you do is always more important than what you should be able to do. That’s why a child’s talents are most likely to blossom when they are nurtured with support, encouragement, education, and effort (Callahan, 2006).
Identifying Gifted Children How might a parent spot an unusually bright child? Early signs of giftedness are not always purely “intellectual.” Giftedness can be either the possession of a high IQ or of special talents or aptitudes. The following signs may reveal that a child is gifted: a tendency to seek out older children and adults; an early fascination with expla- nations and problem solving; talking in complete sentences as early as 2 or 3 years of age; an unusually good memory; precocious talent in art, music, or number skills; an early interest in books, along with early reading (often by age 3); showing of kindness, understanding, and cooperation toward others (Dai, 2010; Distin, 2006).
Notice that this list goes beyond straight g-factor, or general “academic” intelligence. Children may be gifted in ways other than having a high IQ. In fact, if artistic talent, mechanical aptitude, musical aptitude, athletic potential, and so on are considered, many children have a special “gift” of one kind or another. Limiting giftedness to high IQ can shortchange children with special talents or potentials. This is especially true of ethnic minority children, who may be the victims of subtle biases in standardized intelligence tests. These children, as well as children with physical disabilities, are less likely to be recognized as gifted (Castellano & Frazier, 2011; Ford & Moore, 2006).
Giftedness Either the possession of a high IQ or special talents or aptitudes.
Intellectual disability (formerly mental retardation) The presence of a developmental disability, a formal IQ score below 70, or a significant impairment of adaptive behavior.
GATE Programs Being exceptionally bright is not without its problems. Usually, parents and teachers must make adjustments to help gifted chil- dren make the most of their talents ( Jolly et al., 2011). The gifted child may become bored in classes designed for average children. This can lead to misbehavior or clashes with teachers who think the gifted child a show-off or smart aleck. Extremely bright chil- dren may also find classmates less stimulating than older children or adults. In recognition of these problems, many schools now provide special Gifted and Talented Education (GATE) classes for gifted children. Such programs combine classroom enrich- ment with fast-paced instruction to satisfy the gifted child’s appetite for intellectual stimulation (Dai, 2010). Since 1988, the federally funded Jacob K. Javits Gifted and Talented Children and Youth Education Act has provided ongoing funds for research into gifted and talented education programs (Reis & Renzulli, 2010).
All children benefit from enriched environments. For a discussion of enrichment and some guidelines for parents, see Chapter 3, pages 87–88.
In the next section, we will discuss intellectual disability.
Intellectual Disability— A Difference That Makes a Difference
Gateway Question 9.5: What causes intellectual disability? Before you begin, take a few moments to read “Meet the Rain Man,” in which you will find information about a remarkable mixture of brilliance and intellectual disability. And please keep Kim Peek in mind as you read on. There is usually much more to intellectually disabled people than can be shown by the results of IQ testing (Treffert, 2010). It is especially important to realize that intellectu- ally disabled persons have no handicap when feelings are concerned. They are easily hurt by rejection, teasing, or ridicule. Likewise, they respond warmly to love and acceptance. They have a right to self- respect and a place in the community (Montreal Declaration on Intellectual Disabilities, 2004). This is especially important during childhood, when support from others adds greatly to the person’s chances of becoming a well-adjusted member of society.
Levels of Intellectual Disability A person with mental abilities far below average is termed intel- lectually disabled (the former term, mentally retarded, is now regarded by many as offensive). According to the current definition
It is wise to remember that there are many ways in which a child may be gifted. Many schools now offer Gifted and Talented Edu- cation programs for students with a variety of special abilities—not just for those who score well on IQ tests.
These youngsters are participants in the Special Olympics—an athletic event for the intellectually disabled. It is often said of the Special Olympics that “everyone is a winner—participants, coaches, and spectators.”
listed in the American Psychiatric Association’s Diagnostic and Sta- tistical Manual of Mental Disorders (DSM-IV), intellectual disabil- ity begins at an IQ of approximately 70 or below and is classified as shown in ■ Table 9.4 (American Psychiatric Association, 2000). The listed IQ ranges are approximate because IQ scores normally vary a few points. The terms in the right-hand column are listed only to give you a general impression of each IQ range. Currently, a person’s ability to perform adaptive behaviors (basic skills such as dressing, eating, communicating, shopping, and working) also fig- ures into evaluating this disability (American Psychiatric Associa- tion, 2000; Hallahan, Kauffman, & Pullen, 2011).
A new edition of the DSM, the DSM-5, is scheduled for pub- lication in 2012. It is quite likely that the new definitions of levels
of intellectual disability will deemphasize IQ and focus more heavily on impairment of adaptive behaviors (American Psychiat- ric Association, 2010). After all, why label someone with fairly good adaptive skills “severely intellectually disabled” just because his or her IQ falls within a prescribed range? The end result of such labels is, too often, a placing of needless limitations on the educational goals of intellectually disabled persons (Harris, 2010; Kirk et al., 2011).
Are the intellectually disabled usually placed in institutions? No. Total care is usually only necessary for the profoundly disabled (IQ below 25). Many of these individuals live in group homes or with their families. Those who are severely disabled (IQ of 25–40) and moderately disabled (IQ of 40–55) are capable of mastering basic language and self-help skills. Many become self-supporting by working in sheltered workshops (special simplified work environ- ments). The mildly disabled (IQ of 55–70) make up about 85 per- cent of all those affected. This group can benefit from carefully structured education. As adults, these persons, as well as the bor- derline disabled (IQ 70–85), are capable of living alone and they may marry. However, they tend to have difficulties with many of the demands of adult life (Zetlin & Murtaugh, 1990).
Causes of Intellectual Disability What causes intellectual disability? In 30 to 40 percent of cases, no known biological problem can be identified. In many such instances, the degree of disability is mild, in the 50–70 IQ range.
Levels of Intellectual Disability
Degree of Intellectual Disability
Required Level of Support
50–55 to 70 Mild Educable Intermittent
35–40 to 50–55 Moderate Trainable Limited
20–25 to 35–40 Severe Dependent Extensive
Below 20–25 Profound Life support Pervasive
■ TABLE 9.4
(Adapted from American Psychiatric Association, 2000.)
Meet the Rain ManThe Clinical File
Meet Kim Peek, the model for Dustin Hoff- man’s character in the Academy Award– winning movie Rain Man (Peek & Hanson, 2007). Kim began memorizing books at 18 months of age. By the time of his death in 2009, he could recite from memory more than 9,000 books. He knew all the ZIP codes and area codes in the United States and could give accurate travel directions be- tween any two major U.S. cities. He could also discuss hundreds of pieces of classical music in detail and could play most of it quite well. Amazingly, though, for someone with such skills, Kim had difficulty with ab- stract thinking and tests of general intelli- gence. He was poorly coordinated and couldn’t button his own clothes (Treffert, 2010; Treffert & Christensen, 2005).
Kim Peek had savant syndrome, in which a person of limited intelligence shows exceptional mental ability in one or more narrow areas, such as mental arithmetic, cal-
endar calculations, art, or music (Crane et al., 2010; Young, 2005).
Do savants have special mental powers not shared by most people? According to one the- ory, many savants have suffered some form of damage to their left hemispheres, freeing them from the “distractions” of language, concepts, and higher-level thought. This al- lows them to focus with crystal clarity on music, drawing, prime numbers, license plates, TV commercials, and other specific in- formation (Young, 2005). Another theory holds that the performances of many sa- vants result from intense practice (Miller, 1999). Perhaps each of us harbors embers of mental brilliance that intense practice could fan into full flame (Snyder et al., 2006; Tref- fert, 2010).
Although savant syndrome hasn’t been fully explained, it does show that extraordi- nary abilities can exist apart from general intelligence.
Once, four months after reading a novel, Kim was asked about a character. He immediately named the character, gave the page number on which a description appeared, and accurately recited several paragraphs about the character (Treffert & Christensen, 2005).
Savant syndrome The possession of exceptional mental ability in one or more narrow areas, such as mental arithmetic, calendar calculations, art, or music by a person of limited general intelligence.
Familial intellectual disability Mild intellectual disability associated with homes that are intellectually, nutritionally, and emotionally impoverished.
Down Syndrome A genetic disorder caused by the presence of an extra chromosome; results in intellectual disability.
Fragile X syndrome A genetic form of intellectual disability caused by a defect in the X chromosome.X
Often, other family members are also mildly disabled. Familial intellectual disability, as this is called, occurs mostly in very poor households, in which nutrition, intellectual stimulation, medical care, and emotional support may be inadequate. This suggests that familial intellectual disability is based largely on an impoverished environment. Thus, better nutrition, education, and early childhood enrichment programs could prevent many cases of intellectual disability (Beirne-Smith, Patton, & Shan- non, 2006).
About half of all cases of intellectual disability are organic, or related to physical disorders (Das, 2000). These include birth injuries (such as lack of oxygen during delivery), and fetal damage (prenatal damage from disease, infection, or drugs). Metabolic disorders, which affect energy production and use in the body, also cause intellectual disability. Some forms of intel- lectual disability are linked to genetic abnormalities, such as missing genes, extra genes, or defective genes. Malnutrition and exposure to lead, PCBs, and other toxins early in childhood can also cause organic intellectual disability (Beirne-Smith, Patton, & Shannon, 2006). Let’s briefly look at several distinctive problems.
Down Syndrome In 1 out of 800 babies, the disorder known as Down syndrome causes moderate to severe intellectual disability and a shortened life expectancy of around 49 years. It is now known that Down syndrome children have an extra 21st chromosome. This condi- tion, which is called trisomy-21, results from flaws in the par- ents’ egg or sperm cells. Thus, although Down syndrome is genetic, it is not usually hereditary (it doesn’t “run in the family”).
The age of parents is a major factor in Down syndrome. As people age, their reproductive cells are more prone to errors dur- ing cell division. This raises the odds that an extra chromosome will be present. As you can see in the following figures, the older a
woman is, the greater the risk (National Institute of Child Health and Human Development, 2010):
Mother’s age Incidence of Down syndrome Under 30 1/11000 Early 40s 1/105 Late 40s 1/12
Fathers, and possibly especially older fathers, also add to the risk; in a small percentage of cases, the father is the source of the extra chromosome (National Institute of Child Health and Human Development, 2010). Older adults who plan to have children should carefully consider the odds shown here.
There is no “cure” for Down syndrome. However, these chil- dren are usually loving and responsive, and they make progress in a caring environment. At a basic level, Down syndrome children can do most of the things that other children can, only slower. The best hope for Down syndrome children, therefore, lies in specially tai- lored educational programs that enable them to lead fuller lives.
Fragile X Syndrome The second most common form of genetic intellectual disability (after Down syndrome) is fragile X syndrome (Hallahan, Kauff- man, & Pullen, 2011). Unlike Down syndrome, fragile X syn- drome is hereditary—it does run in families. The problem is related to a thin, frail-looking area on the X (female) chromosome. Because fragile X is sex linked (like color-blindness), boys are most often affected, at a rate of about 1 out of every 3800 (National Fragile X Foundation, 2011).
Fragile X males generally have long, thin faces and big ears. Physically, they are usually larger than average during childhood, but smaller than average after adolescence. Up to three-fourths of all fragile X males suffer from hyperactivity and attention disor- ders. Many also have a peculiar tendency to avoid eye contact with others.
Fragile X males are only mildly intellectually disabled during early childhood, but they are often severely or profoundly intel- lectually disabled as adults. When learning adaptive behaviors, they tend to do better with daily living skills than with language and social skills (Hallahan, Kauffman, & Pullen, 2011).
Phenylketonuria (PKU) The problem called phenylketonuria (FEN-ul-KEET-uh-NURE- ee-ah) is a genetic disease. Children who have PKU lack an impor- tant enzyme. This causes phenylpyruvic (FEN-ul-pye-ROO-vik)
This young woman exhibits the classical features of Down syndrome: Distinctive features of this problem are almond-shaped eyes, a slightly protruding tongue, a stocky build, and stubby hands with deeply creased palms.
ce l J
acid (a destructive chemical) to collect within their bodies. PKU is also linked to very low levels of dopamine, an important chemical messenger in the brain. If PKU goes untreated, severe intellectual disability typically occurs by age 3.
PKU can be detected in newborn babies by routine medical testing. Affected children are usually placed on a diet low in phe- nylalinine, the substance the child’s body can’t handle. Carefully following this diet will usually prevent intellectual disability (Grosse, 2010). (Phenylalinine is present in many foods. You might be interested to know that it is also found in Aspartame, the artificial sweetener in diet colas.)
Microcephaly The word microcephaly (MY-kro-SEF-ah-lee) means small- headedness. The microcephalic person suffers a rare abnormality in which the skull is extremely small or fails to grow. This forces the brain to develop in a limited space, causing severe intellectual dis- ability (Szabó et al., 2010). Although they are typically institution- alized, microcephalic persons are usually affectionate, well-behaved, and cooperative.
Hydrocephaly Hydrocephaly (HI-dro-SEF-ah-lee: “water on the brain”) is caused by a buildup of cerebrospinal fluid within brain cavities. Pressure from this fluid can damage the brain and enlarge the head. Hydro- cephaly is not uncommon—about 10,000 hydocephalic babies are born each year in the United States and Canada. However, thanks to new medical procedures, most of these infants will lead nearly normal lives. A surgically implanted tube drains fluid from the brain into the abdomen and minimizes brain damage. Although affected children usually score below average on mental tests, severe intellectual disability usually can be prevented (Rourke et al., 2002).
Cretinism Cretinism (KREET-un-iz-um) is another type of intellectual disabil- ity that appears in infancy. It results from an insufficient supply of thyroid hormone. In some parts of the world, cretinism is caused by a lack of iodine in the diet (the thyroid glands require iodine to func- tion normally). Iodized salt has made this source of intellectual dis- ability rare in developed nations. Cretinism causes stunted physical and intellectual growth that cannot be reversed. Fortunately, cretin- ism is easily detected in infancy. Once detected, it can be treated with thyroid hormone replacement, before permanent damage occurs.
Heredity and Environment— Super Rats, Family Trees, and Video Games
Gateway Question 9.6: How do heredity and environment affect intelligence? Is intelligence inherited? This seemingly simple question is loaded with controversy. Some psychologists believe that intelligence is strongly affected by heredity. Others feel that environment is dominant. Let’s examine some evidence for each view.
In a classic study of genetic factors in learning, Tryon (1929) managed to breed separate strains of “maze-bright” and “maze-
Knowledge Builder Variations in Intelligence
RECITE 1. The distribution of IQs approximates a _________________________
(bell-shaped) curve. 2. Differences in the intellectual strengths of men and women have
grown larger in recent years. T or F?
3. The association between IQ and high-status professional jobs proves that such jobs require more intelligence. T or F?
4. Only about 6 percent of the population scores above 140 on IQ tests. T or F?
5. An IQ score below 90 indicates intellectual disability. T or F? 6. Many cases of intellectual disability without known organic causes
appear to be ______________________________. Match: 7. ____ PKU A. Too little thyroid hormone 8. ____ Microcephaly B. Very small brain 9. ____ Hydrocephaly C. 47 chromosomes 10. ____ Cretinism D. Lack of an important enzyme 11. ____ Down syndrome E. Excess of cerebrospinal fluid 12. ____ Fragile X F. Abnormal female chromosome
G. Caused by a lack of oxygen at birth
REFLECT Think Critically
13. Lewis Terman took great interest in the lives of many of the “Ter- mites.” He even went so far as to advise them about what kinds of careers they should pursue. What error of observation did Terman make?
If you measure the heights of all the people in your psychology class, most people will be clustered around an average height. Very few will be extremely tall or extremely short. Does this ring a bell? Do you think it’s normal? (It is, of course; most measured human characteristics form a normal curve, just as IQs do.)
Do you think that giftedness should be defined by high IQ or having special talents (or both)? To increase your chances of succeeding in today’s society, would you prefer to be smart or talented (or both)? How about smart, talented, motivated, and lucky!?
As a psychologist you are asked to assess a child’s degree of intellec- tual disability. Will you rely more on IQ or the child’s level of adaptive behavior? Would you be more confident in your judgment if you took both factors into account?
Answers: 1. normal 2. F 3. F 4. F 5. F 6. familial 7. D 8. B 9. E 10. A 11. C 12. F 13. Terman may have unintentionally altered the behavior of the people he was studying. Although Terman’s observations are generally regarded as valid, he did break a basic rule of scientific observation.
Phenylketonuria A genetic disease that allows phenylpyruvic acid to accumulate in the body.
Microcephaly A disorder in which the head and brain are abnormally small.y Hydrocephaly A buildup of cerebrospinal fluid within brain cavities. Cretinism Stunted growth and intellectual disability caused by an
insufficient supply of thyroid hormone. Eugenics Selective breeding for desirable characteristics. Fraternal twins Twins conceived from two separate eggs. Identical twins Twins who develop from a single egg and have identical
dull” rats (animals that were extremely “bright” or “stupid” at learning mazes). After several generations of breeding, the slowest “super rat” outperformed the best “dull” rat. This and other studies of eugenics (selective breeding for desirable characteristics) sug- gest that some traits are highly influenced by heredity.
That may be true, but is maze-learning really a measure of intel- ligence? No, it isn’t. Tryon’s study seemed to show that intelligence is inherited, but later researchers found that the “bright” rats were simply more motivated by food and less easily distracted during testing. When they weren’t chasing after rat chow, the “bright” rats were no more intelligent than the supposedly dull rats. Thus, Try- on’s study did demonstrate that behavioral characteristics can be influenced by heredity. However, it was inconclusive concerning intelligence. Because of such problems, animal studies cannot tell us with certainty how heredity and environment affect intelli- gence. Let’s see what human studies reveal.
Hereditary Influences Most people are aware of a moderate similarity in the intelligence between parents and their children, or between brothers and sis- ters. As • Figure 9.5 shows, the closer two people are on a family tree, the more alike their IQs are likely to be.
Does that indicate that intelligence is hereditary? Not necessarily. Brothers, sisters, and parents share similar environments as well as similar genes (Grigorenko, 2005). To separate heredity and envi- ronment, we need to make some selected comparisons.
Twin Studies Notice in • Figure 9.5 that the IQ scores of fraternal twins are more alike than those of ordinary brothers and sisters. Fraternal twins come from two separate eggs fertilized at the same time. They are no more genetically alike than ordinary siblings. Why, then, should the twins’ IQ scores be more similar? The reason is environmental: Parents treat twins more alike than ordinary sib- lings, resulting in a closer match in IQs.
More striking similarities are observed with identical twins, who develop from a single egg and have identical genes. At the top of • Figure 9.5 you can see that identical twins who grow up in the same family have highly correlated IQs. This is what we would expect with identical heredity and very similar environments. Now, let’s consider what happens when identical twins are reared apart. As you can see, the correlation drops, but only from .86 to .72. Psychologists who emphasize genetics believe figures like these show that differences in adult intelligence are roughly 50 percent hereditary ( Jacobs et al., 2008; Neisser et al., 1996).
How do environmentalists interpret the figures? They point out that some separated identical twins differ by as much as 20 IQ points. In every case in which this occurs, there are large educa- tional and environmental differences between the twins. Also, separated twins are almost always placed in homes socially and educationally similar to those of their birth parents. This would tend to inflate apparent genetic effects by making the separated
twins’ IQs more alike. Another frequently overlooked fact is that twins grow up in the same environment before birth (in the womb). If this environmental similarity is taken into account, intelligence would seem to be less than 50 percent hereditary (Devlin, Daniels, & Roeder, 1997; Turkheimer et al., 2003).
Identical twins also tend to have similar personality traits. This suggests that heredity contributes to personality as well as intelligence. For more information, see Chapter 12, pages 425–427.
Environmental Influences Some evidence for an environmental view of intelligence comes from families having one adopted child and one biological child. As • Figure 9.6 shows, parents contribute genes and environment
Parents and children
No data available
.1 1.0.2 .3 .4 .5 .6 .7 .8 .9
• Figure 9.5 Approximate correlations between IQ scores for persons with varying degrees of genetic and environmental similarity. Notice that the correla- tions grow smaller as the degree of genetic similarity declines. Also note that a shared environment increases the correlation in all cases. (Adapted from Bouchard, 1983; Henderson, 1982.)
• Figure 9.6 Comparison of an adopted child and a biological child reared in the same family. (Adapted from Kamin, 1981.)
to their biological child. With an adopted child they contribute only environment. If intelligence is highly genetic, the IQs of bio- logical children should be more like their parents’ IQs than the IQs of adopted children are. However, studies show that children reared by the same mother resemble her in IQ to the same degree. It doesn’t matter whether they share her genes (Kamin, 1981; Weinberg, 1989).
IQ and Socioeconomic Status How much can environment alter intelligence? It depends on the quality of the environment (Turkheimer et al., 2003). One way to look at environmental effects is to compare children adopted by parents of high or low socioeconomic status (SES). As you might predict, children who grow up in high SES homes develop higher IQs than those reared by lower SES parents. Presumably, the higher SES homes provide an enriched environment, with better nutrition, greater educational opportunities, and other advantages (Capron & Duyme, 1992).
More importantly, children adopted out of low SES environ- ments can experience great relative gains in intelligence. That is, the IQs of low SES children may be more dramatically infuenced by environmental factors than the IQs of high SES children (Hen- rich, Heine, & Norenzayan, 2010). In one study, striking increases in IQ occurred in 25 children who were moved from an orphanage and were eventually adopted by parents who gave them love, a fam- ily, and a stimulating home environment. Once considered intel- lectually disabled and unadoptable, the children gained an average of 29 IQ points. A second group of initially less intellectually dis- abled children, who stayed in the orphanage, lost an average of 26 IQ points (Skeels, 1966).
A particularly dramatic environmental effect is the fact that 14 nations have shown average IQ gains of from 5 to 25 points during the last 30 years (Dickens & Flynn, 2001; Flynn, 2007).
Referred to as the Flynn effect, after New Zealand psychologist James Flynn, these IQ boosts, averaging 15 points, occurred in far too short a time to be explained by genetics. It is more likely that the gains reflect environmental forces, such as improved education, nutrition, and living in a technologically complex society (Barber, 2010; Johnson, 2005). If you’ve ever tried to play a computer game or set up a wireless network in your home, you’ll understand why people may be getting better at answering IQ test questions (Neis- ser, 1997). The highlight “You Mean Video Games Might Be Good for Me?” explores this idea further.
If environment makes a difference, can intelligence be taught? The traditional answer is “No.” Brief coaching, for instance, has little positive effect on aptitude and intelligence test scores (Brody, 1992). More encouraging results can be found in early childhood education programs, which provide longer-term stimulating intel- lectual experiences for disadvantaged children (Kirk et al., 2011). In one study, children from low-income families were given enriched environments from early infancy through preschool. By age 2, their IQ scores were already higher than those in a control group. More important, they were still 5 points higher 7 years later (Campbell & Ramey, 1994). High-quality enrichment programs such as Head Start can prevent children from falling behind in school (Barnet & Barnet, 1998; Ramey, Ramey, & Lanzi, 2001).
Later schooling can also have an impact on IQ. Stephen Ceci found that people who leave school lose up to 6 points in IQ per year. Dropping out of school in the eighth grade can reduce a per- son’s adult IQ by up to 24 points. Conversely, IQ rises as people spend more time in school (Ceci, 1991). Israeli psychologist Reuven Feuerstein (FOY-er-shtine) and his colleagues have devel- oped a program they call Instrumental Enrichment. Through hundreds of hours of guided problem solving, students learn to avoid the thinking flaws that lower IQ scores (Feuerstein et al., 1986). Feuerstein and others have shown that such training can
You Mean Video Games Might Be Good for Me?Critical Thinking
Even though the Flynn effect suggests that environmental factors influence intelli- gence (Flynn, 2007; Schooler, 1998), we are left with the question “Which factors?” Psy- chologist Steven Johnson (2005) believes that contemporary culture is responsible. Although he agrees that much popular media content is too violent or sexual in nature, he points out that video games, the Internet, and even television are becoming more complex. As a result, they demand ever greater cognitive effort from us. In other words, it is as important to understand how we experience the environment as it is to understand what we experience.
For example, early video games, such as Pong or PacMan, offered simple, repetitive visual experiences. In contrast, today’s best- selling games, such as Call of Duty or The Sims, offer rich, complicated experiences that can take 40 or more hours of intense problem-solving to complete. Furthermore, players must usually figure out the rules by themselves. Instructions for completing popular games, which have been created by fans, are typically much longer than chapters in this textbook. Only a complex and engag- ing game would prompt players to use such instructions, much less write them for others to use (Johnson, 2005).
According to Johnson, other forms of popular culture have also become more complex, including the Internet and com- puter software. Even popular television has become more cognitively demanding. For example, compared with television dramas of the past, modern dramas weave plot lines and characters through an entire sea- son of programs. In the end, popular cul- ture may well be inviting us to read, reflect, and problem-solve more than ever before (Jaeggi et al., 2008). (Before you uncritically embrace video games, read “You Mean Video Games Might Be Bad for Me?” in Chapter 6.)
Early childhood education program Programs that provide stimulating intellectual experiences, typically for disadvantaged preschoolers.
Reaction time The amount of time a person must look at a stimulus to make a correct judgment about it.
improve thinking abilities and even raise IQs (Feuerstein et al., 2004; Skuy et al., 2002; Tzuriel & Shamir, 2002).
With our growing understanding of how people think and with the tireless aid of computers, it may become common in schools to “teach intelligence.” Most importantly, improved education and training in thinking skills can improve the intellectual abilities of all children, regardless of what their IQ scores are (Hallahan, Kauffman, & Pullen, 2011; Hunt, 1995). Even if “teaching intelli- gence” doesn’t raise IQ scores, it can give children the abilities they need to think better and succeed in life (Perkins & Grotzer, 1997).
Summary To sum up, few psychologists seriously believe that heredity is not a major factor in intelligence, and all acknowledge that environment affects it. Estimates of the impact of heredity and environment continue to vary. But ultimately, both camps agree that improving social conditions and education can raise intelligence.
There is probably no limit to how far down intelligence can go in an extremely poor environment. On the other hand, hered- ity does seem to impose upper limits on IQ, even under ideal conditions. It is telling, nevertheless, that gifted children tend to come from homes in which parents spend time with their chil- dren, answer their questions, and encourage intellectual explora- tion (Dai, 2010).
Impoverished and unstimulating environments can severely restrict mental development during early childhood. See Chapter 3, pages 87–88, for more information.
The fact that intelligence is partly determined by heredity tells us little of any real value. Genes are fixed at birth. Improving the environments in which children learn and grow is the main way in which we can assure that they reach their full potential (Ormrod, 2011; Turkheimer, 1998).
As a final summary, it might help to think of inherited intel- lectual potential as a rubber band that is stretched by outside forces. A long rubber band may be stretched more easily, but a shorter one can be stretched to the same length if enough force is applied. Of course, a superior genetic gift may allow for a higher maximum IQ. In the final analysis, intelligence reflects develop- ment as well as potential, nurture as well as nature (Grigorenko, 2005; Kalat, 2009).
Beyond Psychometric Intelligence—Intelligent Alternatives to “g”
Gateway Question 9.7: Are there alternate views of intelligence? Until now, we have treated intelligence psychometrically, as a qual- ity that can be measured, like height or weight. Other approaches share the goal of understanding intelligence in more detail. Specifi-
cally, let’s have a look at four other approaches to the study of intelligence:
• Some psychologists are investigating the neural basis for intelli- gence. How, they ask, does the nervous system contribute to differences in IQ?
• A second approach views intelligent behavior as an expression of thinking skills. Cognitive psychologists believe that the nervous system is like a fast computer—it’s of little value unless you know how to use it.
• Speaking of computers, would it make sense to understand human intelligence by programming computers? That is one goal of the field of artificial intelligence.
• A fourth trend involves newer, broader definitions of intelli- gence. Many psychologists have begun to question the narrow focus on analytic thinking found in traditional IQ tests.
The Intelligent Nervous System Do more intelligent people have superior nervous systems? It is natural to assume that intelligence, like other human abilities, can be local- ized in the nervous system. But where and how does Steven Hawk- ing’s nervous system allow him to be so intelligent? This is cur- rently a vibrant research field (Banich & Compton, 2011). We can only briefly explore a few threads here.
One possibility is that intelligent people have faster nervous systems. Maybe Steven Hawking’s brain is just faster than the rest of us. To investigate this possibility, researchers measure how fast people process various kinds of information (Bates, 2005). For example, psychologists have looked at people’s reaction time, the time it takes people to respond to a stimulus (see • Figure 9.7). The flurry of brain activity that follows exposure to a stimulus can also be recorded. Such studies attempt to measure a person’s
• Figure 9.7 Stimuli like those used in reaction time tasks. The participant views stimulus (a) followed almost immediately by (b), ensuring that (a) is only briefly visible. The participant’s task is to press one key if the left-hand segment of (a) is shorter and another if it is longer. Participants with higher IQs are generally faster and more accurate at tasks like this (Bates, 2005; Petrill et al., 2001).
speed of processing, which is assumed to reflect the brain’s speed and efficiency (Reed, Vernon, & Johnson, 2004; Waiter et al., 2009). In general, people higher in measured IQ perform faster on reaction time tasks like that shown in • Figure 9.7 (McCrory & Cooper, 2005). In addition, brain areas that control higher mental abilities usually become more active during reaction time testing (Deary et al., 2001; Waiter et al., 2009). Such observa- tions suggest that having a quick nervous system is part of what it means to be quick, smart, swift, or brainy.
Which brain areas control higher mental abilities? You may recall from Chapter 2 that the frontal lobes and especially pre- frontal cortex are related to more complex behaviors. Maybe those parts of Steven Hawking’s brain are just bigger than the rest of us.
Although brain imaging studies confirm the role the frontal lobes play in intelligence, there is more to the story. As you can see in • Figure 9.8, even though these brain images reveal that parts of frontal cortex are larger in people with higher IQs, the same is true for other parts of cortex (Haier et al, 2004). Perhaps we shouldn’t be surprised that a function as complex as intelli- gence relies on activity of many different brain areas. Also, noticeable differences between younger (UNM) and older (UCI) participants suggest that the way the brain expresses intelligence changes as we age. Clearly, we do not yet have a complete picture of the relationship between the nervous system and intelligence.
Intelligent Information Processing Much intelligent behavior is an expression of good thinking skills. Cognitive psychologist David Perkins believes that how smart you are depends on three factors:
• Relatively fixed neural intelligence (the speed and efficiency of the nervous system);
• Experiential intelligence (specialized knowledge and skills acquired over time);
• Reflective intelligence (an ability to become aware of one’s own thinking habits).
Little can be done to change neural intelligence. However, by add- ing to personal knowledge and learning to think better, people can become more intelligent (Perkins, 1995; Ritchhart & Perkins, 2005). The effects of Feuerstein’s Instrumental Enrichment pro- gram (described earlier) are a good example of how reflective intel- ligence can be improved.
Many psychologists now believe that to make full use of innate intelligence a person must have good metacognitive skills. Meta means “beyond,” so metacognitive skills go above and beyond ordi- nary thinking. Such skills involve an ability to manage your own thinking and problem solving. Typically this means breaking prob- lems into parts, establishing goals and subgoals, monitoring your progress, and making corrections. Learning metacognitive skills is the surest avenue to becoming more intelligent (Hunt, 1995; Ku & Ho, 2010).
Metacognitive skills are a large part of what it means to be a reflective thinker. See the “Psychology of Studying,” pages 1–8, to remind yourself (You did read it, right?) how to sharpen your metacognitive skills to become a better student.
Artificial Intelligence Whereas most efforts have focused on measuring intelligence in humans, a small group of psychologists and computer scientists have taken an entirely different approach. Their basic idea is to build machines that display artificial intelligence (AI). This usu- ally refers to creating computer programs capable of doing things that require intelligence when done by people (Russell & Norvig, 2003). As computer scientist Aaron Sloman explains it, “Human brains don’t work by magic, so whatever it is they do should be
UNM Gray Matter UCI Gray Matter UNM White Matter UCI White Matter
• Figure 9.8 MRI identification of cortical areas whose size is correlated with IQ. The left hemisphere is shown in the top row; the right is on the bottom. Participants were drawn from two universities, a younger group from the University of New Mexico (UNM) and an older group from the University of California at Irvine (UCI). Brain areas pictured in red and yellow are larger in people with higher IQs. (From Haier et al., 2004).
Speed of processing The speed with which a person can mentally process information.
Neural intelligence The innate speed and efficiency of a person’s brain and nervous system.
Experiential intelligence Specialized knowledge and skills acquired through learning and experience.
Reflective intelligence An ability to become aware of one’s own thinking habits.
Metacognitive skills An ability to manage one’s own thinking and problem solving efforts.
Artificial intelligence (AI) Refers to both the creation of computer programs capable of doing things that require intelligence when done by people, and to the resulting programs themselves.
doable by machine” (Brooks, 2009). The resulting programs can then help us understand how people do those same things.
Consider, for example, IBM’s “Watson” supercomputer, which outperforms even expert humans at playing the television game Jeopardy (Markoff, 2011). Similarly, Aaron Sloman’s robot, the “Cubinator,” does a spiffy job of solving Rubik’s Cube puzzles. Slo- man hopes the Cubinator’s expertise will help him better under- stand how humans do mathematics (Sloman, 2008).
How smart are computers and robots? Don’t worry, they are not very smart yet. Let’s say you are exchanging instant messages with someone you don’t know. You are allowed to make any comments and ask any questions you like, for as long as you like. In reality, the “person” you are communicating with is a computer. Do you think a computer could fool you into believing it was human? If it did, wouldn’t that qualify it as “intelligent”? You may be surprised to learn that, to date, no machine has come close to passing this test (Moor, 2003).
The problem computers face is that we humans can mentally “shift gears” from one topic to another with incredible flexibility. In contrast, machine “intelligence” is currently “blind” outside its underlying set of rules (D’Mello, Graesser, & King, 2010). As a tiny example, u cann understnd wrds thet ar mizpeld. Computers are very literal and easily stymied by such errors.
Regardless, AI has been successful at very specific tasks (such as playing chess or solving a Rubik’s Cube). Much of current AI is based on the fact that many tasks—from harmonizing music to diagnosing disease—can be reduced to a set of rules applied to a collection of information. AI is valuable in situations in which speed, vast mem- ory, and persistence are required. In fact, AI programs are better at
some tasks than humans are. An example is world chess champion Garry Kasparov’s loss, in 1997, to a computer called “Deep Blue.”
Artificial Intelligence and Cognition Although AI is a long way from duplicating general human intel- ligence, AI systems like the Cubinator offer a way to probe some of our specific cognitive skills, or intelligences. For instance, com- puter simulations and expert systems provide good examples of how AI is used as a research tool.
Computer simulations are programs that attempt to duplicate specific human behaviors, especially thinking, decision making, and problem solving. Here, the computer acts as a “laboratory” for testing models of cognition. If a computer program behaves as humans do (including making the same errors), then the program may be a good model of how we think.
Expert systems are computer programs that respond as a human expert would (Giarratano & Riley, 2005; Mahmoodabadi et al., 2010). They have demystified some human abilities by converting complex skills into clearly stated rules a computer can follow. Expert systems can predict the weather, analyze geological forma- tions, diagnose disease, play chess, read, tell when to buy or sell stocks, and perform many other tasks.
Eventually, AI will almost certainly lead to robots that recognize voices and that speak and act “intelligently” in specific areas of abil- ity. To achieve this, should intelligence be directly programmed into computers? Or should computers be designed to learn from experi- ence, like the human brain does? (Sporns, 2011). Only time will tell.
Multiple Intelligences Defining intelligence as a g-factor (general ability) has been contro- versial. For example, consider William, a grade-school student two years behind in reading, who shows his teacher how to solve a dif- ficult computer-programming problem. Or what about his class- mate, Malika, who is poor in math but plays intricate pieces of piano music? Both of these children show clear signs of what we earlier referred to as aptitudes. And, as we have seen, autistic savants like Kim Peek have even more extreme intellectual strengths and weaknesses. Such observations have convinced many psychologists that it is time to forge new, broader definitions of intelligence. Their basic goal is to better predict “real-world” success—not just the likelihood of success in school (Sternberg & Grigorenko, 2006).
The “Cubinator” solving a Rubik’s Cube at the 2007 Rubik’s Cube World Champi- onships. The winner, in 10 seconds, was a person. The Cubinator took 26 seconds. To what extent is the way the Cubinator comes up with solutions helpful for understanding how humans do it?
Knowledge Builder Heredity, Environment, and Alternate
Views of Intelligence RECITE 1. Selective breeding for desirable characteristics is called
______________________________. 2. The closest similarity in IQs would be observed for
a. parents and their children b. identical twins reared apart c. frater- nal twins reared together d. siblings reared together
3. Most psychologists believe that intelligence is 90 percent hereditary. T or F?
4. Except for slight variations during testing, IQ cannot be changed. T or F? 5. Reaction time has been used as a measure of ___________________
intelligence. a. experiential b. neural c. reflective d. analytical
6. According to Howard Gardner’s theory, which of the following is not measured by traditional IQ tests? a. intrapersonal skills b. spatial skills c. logical skills d. linguistic skills
REFLECT Think Critically
7. Dropping out of school can lower tested IQ and attending school can raise it. What do these observations reveal about intelligence tests?
8. Is it ever accurate to describe a machine as “intelligent”?
Frames of Mind One such psychologist is Howard Gardner of Harvard University. Gardner (2003, 2004, 2008) theorizes that there are actually eight distinctly different kinds of intelligence. These are different mental “languages” that people use for thinking. Each is listed below, with examples of pursuits that make use of them.
1. Language (linguistic abilities)—writer, lawyer, comedian. 2. Logic and math (numeric abilities)—scientist, accountant,
programmer. 3. Visual and spatial (pictorial abilities)—engineer, inventor,
artist. 4. Music (musical abilities)—composer, musician, music critic. 5. Bodily-kinesthetic (physical abilities)—dancer, athlete, surgeon. 6. Intrapersonal (self-knowledge)—poet, actor, minister. 7. Interpersonal (social abilities)—psychologist, teacher,
politician. 8. Naturalist (an ability to understand the natural environ-
ment)—biologist, medicine man, organic farmer.
To simplify a great deal, people can be “word smart,” “number smart,” “picture smart,” “music smart,” “body smart,” “self smart,” “people smart,” and/or “nature smart.”
Most of us are probably strong in only a few types of intelli- gence. In contrast, geniuses like Albert Einstein seem to be able to use nearly all of the intelligences, as needed, to solve problems.
If Gardner’s theory of multiple intelligences is correct, tradi- tional IQ tests measure only a part of real-world intelligence— namely, linguistic, logical-mathematical, and spatial abilities. A further implication is that our schools may be wasting a lot of human potential (Campbell, Campbell, & Dickinson, 2003). For
example, some children might find it easier to learn math or read- ing if these topics were tied into art, music, dance, drama, and so on. Already, many schools are using Gardner’s theory to cultivate a wider range of skills and talents (Campbell, Campbell, & Dickin- son, 2003; Kornhaber & Gardner, 2006).
A Look Ahead As promised earlier, the Psychology in Action section of this chapter addresses questions concerning the validity of intelligence tests and their fairness to various groups. The issues raised go to the heart of the question “What is intelligence?” In addition to being highly interesting and culturally relevant, this topics should round out your understanding of intelligence.
According to Howard Gardner’s theory, bodily-kinesthetic skills reflect one of eight distinct types of intelligence.
Why do you think studies of hereditary and environmental influences on intelligence have provoked such emotional debate? Which side of the debate would you expect each of the following people to favor: teacher, parent, school administrator, politician, medical doctor, liberal, conserva- tive, bigot?
Would you rather have your own intelligence measured with a speed of processing test or a traditional IQ test? Why?
Here’s a mnemonic: New experiences reflect three kinds of intelligence. Can you define neural, experiential, and reflective intelligence in your own words?
Make your own list of specialized intelligences. How many items on your list correspond to the 8 intelligences identified by Gardner?
Answers: 1. eugenics 2. b 3. F 4. F 5. b 6. a 7. Such observations remind us that intelligence tests are affected by learning and that they measure knowledge as well as innate cognitive abilities. 8. Rule-driven expert sys- tems may appear “intelligent” within a narrow range of problem solving. However, they are idiots at everything else. This is usually not what we have in mind when discussing human intelligence.
Multiple intelligences Howard Gardner’s theory that there are several specialized types of intellectual ability.
you may actually know what your IQ is. If not, the following self-administered test will provide a rough estimate of your IQ. Most people are curious about how they would score on an intelligence test. Why not give the Dove test a try?
If you scored 14 on this exam, your IQ is approximately 100, indicating average intelli- gence. If you scored 10 or less, you are intel- lectually disabled. With luck and the help of a special educational program, we may be able to teach you a few simple skills!
Isn’t the Dove Test a little unfair? No, it is very unfair. It was written in 1971 by African- American sociologist Adrian Dove as “a half serious attempt to show that we’re just not talking the same language.” Dove tried to slant his test as much in favor of urban, Afri- can American culture as he believes the typi- cal intelligence test is biased toward a Euro- pean American, middle-class background ( Jones, 2003). (Because of its age, the test is probably now also unfair even for younger African Americans.)
Dove’s test is a thought-provoking reply to the fact that African American children score an average of about 15 points lower on stan- dardized IQ tests than European American children. By reversing the bias, Dove has shown that intelligence tests are not equally valid for all groups. Psychologist Jerome Kagan once remarked, “If the Wechsler and Binet scales were translated into Spanish, Swahili, and Chinese and given to every 10-year-old in Latin America, East Africa, and China, the majority would obtain IQ scores in the mentally retarded range.”
Culture-Fair Testing Certainly we cannot believe that children of different cultures are all intellectually dis- abled. The fault must lie with the test (White, 2006). Cultural values, traditions, and experi- ences can greatly affect performance on tests designed for Western cultures (Sternberg & Grigorenko, 2005; Neisser et al., 1996). For example, our culture places a high value on logic and formal reasoning. Other cultures regard intuition as an important part of what it means to be smart (Norenzayan et al., 2002). Imagine giving the Stanford-Binet to a
Intelligent Intelligence Testing—User Beware!Psychology in Action
Gateway Question 9.8: Is there a downside to intelligence testing? During their lifetimes, most people take an intelligence test, or one of the closely related scholastic aptitude tests. If you have ever taken an individually administered IQ test,
Time limit: 5 minutes. Circle the correct answer. 1. T-bone Walker got famous for playing
what? a. trombone b. piano c. T-flute
d. guitar e. “hambone” 2. A “gas head” is a person who has a a. fast-moving car. b. stable of “lace.”
c. “process.” d. habit of stealing cars. e. long jail record for arson
3. If you throw the dice and 7 is showing on the top, what is facing down? a. 7 b. snake eyes c. boxcars d. little
joes e. 11 4. Cheap chitlings (not the kind you
purchase at a frozen-food counter) will taste rubbery unless they are cooked long enough. How soon can you quit cooking them to eat and enjoy them? a. 45 minutes b. 2 hours c. 24 hours
d. 1 week (on a low flame) e. 1 hour
5. Bird or Yardbird was the jacket jazz lovers from coast to coast hung on a. Lester Young b. Peggy Lee
c. Benny Goodman d. Charlie Parker e. Birdman of Alcatraz
6. A “handkerchief head” is a. a cool cat. b. a porter. c. an Uncle
Tom. d. a hoddi. e. a preacher 7. Jet is
a. an East Oakland motorcycle club. b. one of the gangs in West Side Story. c. a news and gossip magazine. d. a way of life for the very rich
Dove Counterbalance Intelligence Test
8. “Bo Diddley” is a a. game for children. b. down-home
cheap wine. c. down-home singer. d. new dance. e. Moejoe call
9. Which word is most out of place here? a. splib b. blood c. gray d. spook
e. black 10. If a pimp is uptight with a woman who
gets state aid, what does he mean when he talks about “Mother’s Day”?
a. second Sunday in May b. third Sunday in June c. first of every month d. none of these e. first and fifteenth of every month
11. Many people say that “Juneteenth” ( June 10th) should be made a legal holiday because this was the day when
a. the slaves were freed in the United States. b. the slaves were freed in Texas. c. the slaves were freed in Jamaica. d. the slaves were freed in California. e. Martin Luther King was born. f. Booker T. Washington died
12. If a man is called a “blood,” then he is a a. fighter b. Mexican-American
c. Black d. hungry hemophile e. red man or Indian
13. What are the Dixie Hummingbirds? a. a part of the KKK b. a swamp
disease c. a modern gospel group d. a Mississippi Negro paramilitary strike force e. deacons
14. The opposite of square is a. round. b. up c. down d. hip
Answers: 1. d 2. c 3. a 4. c 5. d 6. c 7. c 8. c 9. c 10. c 11. b 12. c 13. c 14. d
Chapter 9324 Chapter 9324
in St. Louis and found that the African Amer- ican group averaged 36 points higher than the European American group.
Second, it is no secret that as a group African Americans are more likely than European Americans to live in environments that are physically, educationally, and intel- lectually impoverished. When unequal edu- cation is part of the equation, IQs may tell us little about how heredity affects intelligence (Sternberg, Grigorenko, & Kidd, 2005; Suzuki & Aronson, 2005). Indeed, one study found that placing poor African American children into European American adoptive families increased the children’s IQs by an average of 13 points, bringing them into line with those of European American children (Nisbett, 2005). That is, providing African American children with the same environ- mental experiences available to European American children erased IQ differences.
A tantalizing hint that lower African American IQ scores are not genetic is pro- vided by Ray Friedman and his colleagues at Vanderbilt University who administered a 20-item test to African American and Euro- pean American students. Before the election of Barack Obama, African American stu- dents performed more poorly than European American students. During the election, African American students performed just as well as their European American counter- parts. Apparently, President Obama is pro- viding a role model, inspiring better academic performance in African American students (Tite, 2009).
Further, although IQ predicts school per- formance, it does not predict later career suc- cess (McClelland, 1994). In this regard, “street smarts,” or what psychologist Robert Sternberg calls practical intelligence (Stemler & Sternberg, 2006), is often seen by minority cultures as more important than “book learn- ing,” or what Sternberg calls analytic intelli- gence (Sankofa et al., 2005).
Most psychologists have concluded that there is no scientific evidence that group dif- ferences in average IQ are based on genetics. In fact, studies that used actual blood group testing found no significant correlations between ethnic ancestry and IQ scores. This is because it does not even make genetic sense to talk about “races” at all—obvious external markers, like skin color, have little to do with underlying genetic differences (Bonham et al., 2005; Sternberg, 2007). Group differences in
IQ and Race Historically, African American children in the United States scored an average of about 15 points lower on standardized IQ tests than European-American children. As a group, Japanese American children scored above average in IQ. Could such differences be genetic? One persistent claim is that Afri- can Americans score below average in IQ because of their “genetic heritage” and because they are genetically incapable of climbing out of poverty (Hernstein & Mur- ray, 1994; Rushton & Jensen, 2005). Psy- chologists have responded to such claims with a number of counterarguments.
First, psychologists reiterate the point made by the Dove Test. The assumptions, biases, and content of standard IQ tests do not always allow meaningful comparisons between ethnic, cultural, or racial groups (White, 2006). As Leon Kamin (1981) says, “The important fact is that we cannot say which sex (or race) might be more intelligent, because we have no way of measuring ‘intelli- gence.’ We have only IQ tests.”
Kamin’s point is that the makers of IQ tests decided in advance to use test items that would give men and women equal IQ scores. It would be just as easy to put together an IQ test that would give African Americans and European Americans equal scores. Differ- ences in IQ scores are not a fact of nature, but a decision by the test makers. That’s why European Americans do better on IQ tests written by European Americans, and African Americans do better on IQ tests devised by African Americans. Another example of this fact is an intelligence test made up of 100 words selected from the Dictionary of Afro-American Slang. Williams (1975) gave the test to 100 African American and 100 European American high school students
young Bushman hunter. If tracking prey is what he values and is good at, then what would it mean if (when?) he got a low IQ score? (Feel free to reread “Intelligence— How Would a Fool Do It?” near the begin- ning of this chapter.)
To avoid this problem, some psychologists have tried to develop culture-fair tests that do not disadvantage certain groups. A culture- fair test is designed to minimize the impor- tance of skills and knowledge that may be more common in some cultures than in oth- ers. (For a sample of culture-fair test items, see • Figure 9.9.)
Culture-fair tests attempt to measure intelligence without, as much as possible, being influenced by a person’s verbal skills, cultural background, and educational level. Their value lies not just in testing people from other cultures. They are also useful for testing children in the United States who come from poor communities, rural areas, or ethnic minority families (Stephens et al., 1999). However, no intelligence test can be entirely free of cultural influences. For instance, our culture is very “visual,” because children are constantly exposed to television, movies, video games, and the like. Thus, compared with children in developing countries, a child who grows up in the United States may be better prepared to take both nonverbal tests and traditional IQ tests.
Since the concept of intelligence exhibits diversity across cultures, many psychologists have begun to stress the need to rethink the concept of intelligence itself (Greenfield, 1997; Sternberg & Grigorenko, 2005). If we are to find a truly culture-fair way to measure intelli- gence, we first need to identify those core cog- nitive skills that lie at the heart of human intel- ligence the world around (Gardner, 2008; Henrich, Heine, & Norenzayan, 2010).
1 2 3 4 5 1 2 3 4 5
(a) Sample series problem (b) Sample matrix problem
• Figure 9.9 Sample items like those often found on culture-fair intelligence tests. (a) Sample series problem. Which pattern correctly continues the series of patterns shown at the top left? (Number 4.) (b) Sample matrix problem. Which pattern fits best completes the matrix of patterns shown at the top right? (Number 1.) The idea is that the ability to read and the mastery of culturally relevant knowledge should not be necessary to do well. Nev- ertheless, do you think illiterate street orphans from Sao Paulo, Brazil, or Aboriginals living in the desert of the Aus- tralian outback would find these items as easy to complete as you did? If not, can you think of any alternative truly culture-fair ways to test intelligence across different cultures?
, I nc
Intelligence 325 Intelligence 325
Culture-fair test A test designed to minimize the importance of skills and knowledge that may be more common in some cultures than in others.
tests, overuse of class time to prepare students for the tests (instead of teaching general skills), and in the case of intelligence tests, the charge that tests are often biased. Also, most standardized tests demand passive rec- ognition of facts, assessed with a multiple- choice format. They do not, for the most part, test a person’s ability to think critically or creatively or to apply knowledge to solve problems. Various “high-stakes tests,” which can make or break a person’s career could be improved by: (1) removing all questions that favor one group over another; (2) using digi- tal video-based testing, when possible, to reduce the importance of verbal skills; and (3) providing a pre-test orientation for all test takers, so that people who can afford coach- ing won’t have an unfair advantage (Sackett et al., 2001).
High Stakes Testing Intelligence tests are a double-edged sword; we have learned much from their use yet they have the potential to do great harm. In the final analysis, it is impor- tant to remember—as Howard Gardner has pointed out—that creativity, motivation, physical health, mechanical aptitude, artistic ability, and numerous other qualities not mea- sured by intelligence tests contribute to the achievement of life goals. Also, remember that IQ is not intelligence. IQ is an index of intelligence (as narrowly defined by a particu- lar test). Change the test and you change the score. An IQ is not some permanent number stamped on the forehead of a child that for- ever determines his or her potential. The real issue is what skills people have, not what their test scores are (Hunt, 1995).
The Whole Human: Wisdom In the final analysis, intelligence reflects devel- opment as well as potential, nurture as well as nature (Grigorenko, 2005). Moreover, the fact that intelligence is partly determined by heredity tells us little of any real value. Genes are fixed at birth. Improving the environ- ments in which children learn and grow is the
group of college students with straight A’s to another group with poor grades, he found no differences in later career success (McClelland, 1994).
Standardized Testing In addition to IQ tests, 400 to 500 million standardized multiple-choice tests are given in schools and workplaces around the nation each year. Many, like the SAT Reasoning Test, may determine whether a person is admitted to college. Other tests—for employment, licensing, and certification—directly affect the lives of thousands by qualifying or dis- qualifying them for jobs.
Widespread reliance on standardized intel- ligence tests and aptitude tests raises questions about the relative good and harm they do. On the positive side, tests can open opportunities as well as close them. A high test score may allow a disadvantaged youth to enter college, or it may identify a child who is bright but emotionally disturbed. Test scores may also be fairer and more objective than arbitrary judg- ments made by admissions officers or employ- ment interviewers. Also, tests do accurately predict academic performance. The fact that academic performance does not predict later success may call for an overhaul of college course work, not an end to testing.
On the negative side, mass testing can occasionally exclude people of obvious abil- ity. In one case, a student who was seventh in his class at Columbia University, and a mem- ber of Phi Beta Kappa, was denied entrance to law school because he had low scores on the Law School Admissions Test. Other com- plaints relate to the frequent appearance of bad or ambiguous questions on standardized
IQ scores are based on cultural and environ- mental diversity, as much as on heredity (Neisser et al., 1996; Nisbett, 2005). To con- clude otherwise reflects political beliefs and biases, not scientific facts.
Questioning IQ—Beyond the Numbers Game African Americans are not the only segment of the population with reason to question the validity of intelligence testing and the role of heredity in determining intelligence. The clarifications they have won extend to others as well.
Consider the 9-year-old child confronted with this question on an intelligence test: “Which of the following does not belong with the others? Roller skates, airplane, train, bicycle.” If the child fails to answer “airplane,” does it reveal a lack of intelligence? It can be argued that an intelligent choice could be based on any of these alternatives: Roller skates are not typically used for transporta- tion; an airplane is the only nonland item; a train can’t be steered; a bicycle is the only item with just two wheels. The parents of a child who misses this question may have reason to be angry since educational systems tend to classify children and then make the label stick.
Court decisions have led some states to outlaw the use of intelligence tests in public schools. Criticism of intelligence testing has also come from the academic community. Har- vard University psychologist David McClel- land believes that IQ is of little value in predict- ing real competence to deal effectively with the world. McClelland concedes that IQ predicts school performance, but when he compared a
“Yes We Can.” President Obama’s intelligence is inspiring millions of Americans and others around the world to aspire to greater aca- demic success. His example is particularly important to African Americans.
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convergent thinking, intelligence, and reason, spiced with creativity and originality (Meeks & Jeste, 2009). People who are wise approach life with openness and tolerance (Helson & Srivastava, 2002).
tests may make a total mess of her life. Like- wise, people can be intelligent without being creative; and clear, rational thinking can lead to correct, but uninspired, answers (Solomon, Marshall, & Gardner, 2005). In many areas of human life, wisdom represents a mixture of
main way in which we can ensure that they reach their full potential (Grigorenko & Sternberg, 2003; White, 2006).
Perhaps most importantly, people can be intelligent without being wise. For example, a person who does well in school and on IQ
Chapter in Review Gateways to Intelligence
9.1 How do psychologists define intelligence? 9.1.1 Intelligence refers to the general capacity (or g-factor)
to act purposefully, think rationally, and deal effectively with the environment.
9.1.2 In practice, intelligence is operationally defined by intelligence tests, which provide a useful but narrow estimate of real-world intelligence.
9.1.3 General intelligence is distinguished from specific aptitudes. Special aptitude tests and multiple aptitude tests are used to assess a person’s capacities for learning various abilities. Aptitude tests measure a narrower range of abilities than general intelligence tests do.
9.1.4 To be of any value, a psychological test must be reliable (give consistent results). A worthwhile test must also have validity, meaning that it measures what it claims to measure. Widely used
intelligence tests are also objective (they give the same result when scored by different people) and standardized (the same procedures are always used in giving the test, and norms have been established so that scores can be interpreted).
9.2 What are typical IQ tests like? 9.2.1 The first practical intelligence test was assembled by
Alfred Binet. A modern version of Binet’s test is the Stanford- Binet Intelligence Scales—Fifth Edition (SB5).
9.2.2 A second major intelligence test is the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV). Wechsler’s children’s version is the Wechsler Intelligence Scale for Children—Fourth Edi- tion (WISC-IV).
9.2.3 The SB5, WAIS-IV, and WISC-IV measure both ver- bal and performance intelligence.
Gateway QUESTIONS REVISITED
Knowledge Builder Intelligence Testing in Perspective
RECITE 1. The WAIS-IV, Stanford-Binet 5, and Dove Test are all culture-fair intel-
ligence scales. T or F? 2. The claim that heredity accounts for racial differences in average IQ
ignores environmental differences and the cultural bias inherent in standard IQ tests. T or F?
3. IQ scores predict school performance. T or F? 4. IQ is not intelligence; it is one index of intelligence. T or F?
REFLECT Think Critically
5. Assume that a test of memory for words is translated from English to Spanish. Would the Spanish version of the test be equal in difficulty to the English version?
Do you think it would be possible to create an intelligence test that is uni- versally culture-fair? What would its questions look like? Can you think of any type of question that wouldn’t favor the mental skills emphasized by some culture, somewhere in the world?
Funding for schools in some states varies greatly in rich and poor neighborhoods. Imagine that a politician opposes spending more money on disadvantaged students because she believes it would “just be a waste.” What arguments can you offer against her assertion?
In your own opinion, what are the advantages of using standardized tests to select applicants for college, graduate school, and professional schools? What are the disadvantages?
Answers: 1. F 2. T 3. T 4. T 5. Probably not, because the Spanish words might be longer or shorter than the same words in English. The Spanish words might also sound more or less alike than words on the original test. Translating an intelligence test into another language can subtly change the meaning and difficulty of test items.
9.2.4 In addition to individual tests, intelligence tests have also been produced for use with groups. A group test of historical interest is the Army Alpha. The SAT, the ACT, and the CQT are group scholastic aptitude tests. Although narrower in scope than IQ tests, they bear some similarities to them.
9.2.5 Intelligence is expressed in terms of an intelligence quotient (IQ). IQ is defined as mental age (MA) divided by chronological age (CA) and then multiplied by 100. An “average” IQ of 100 occurs when mental age equals chronological age.
9.2.6 Modern IQ tests no longer calculate IQs directly. Instead, the final score reported by the test is a deviation IQ.
9.2.7 IQ scores become fairly stable at about age 6, and they become increasingly reliable thereafter.
9.3 How do IQ scores relate to sex, age, and occupation? 9.3.1 The distribution of IQ scores approximates a normal
curve. 9.3.2 There are no overall differences between males and
females in tested intelligence. However, very small sex differences may result from the intellectual skills our culture encourages males and females to develop.
9.3.3 On average, IQ scores continue to gradually increase until middle age. Later intellectual declines are moderate for most people until their 70s. Aging also involves a shift from fluid intel- ligence to crystallized intelligence.
9.3.4 IQ is related to school grades and job status. The sec- ond association may be somewhat artificial because educational credentials are required for entry into many occupations.
9.4 What does IQ tell us about genius? 9.4.1 People with IQs in the gifted or “genius” range of
above 140 tend to be superior in many respects. 9.4.2 By criteria other than IQ, a large proportion of chil-
dren might be considered gifted or talented in one way or another. Intellectually gifted children often have difficulties in average classrooms and benefit from special accelerated programs.
9.5 What causes intellectual disability? 9.5.1 People with the savant syndrome combine intellectual
disability with exceptional ability in a very limited skill. 9.5.2 The term intellectually disabled is applied to those
whose IQ falls below 70 or who lack various adaptive behaviors. 9.5.3 Current classifications of intellectual disability are:
mild (50–55 to 70), moderate (35–40 to 50–55), severe (20–25 to 35–40), and profound (below 20–25). Chances for educational success are related to the degree of intellectual disability.
9.5.4 Many cases of subnormal intelligence are thought to be the result of familial intellectual disability, a generally low level
of educational and intellectual stimulation in the home, coupled with poverty and poor nutrition.
9.5.5 About 50 percent of the cases of intellectual disabil- ity are organic, caused by birth injuries, fetal damage, metabolic disorders, or genetic abnormalities. The remaining cases are of undetermined cause.
9.5.6 Six distinct forms of organic intellectual disability are Down syndrome, fragile X syndrome, phenylketonuria (PKU), microcephaly, hydrocephaly, and cretinism.
9.6 How do heredity and environment affect intelligence? 9.6.1 Studies of eugenics in animals and familial relation-
ships in humans demonstrate that intelligence is partially deter- mined by heredity. However, environment is also important, as revealed by changes in tested intelligence induced by schooling and stimulating environments.
9.6.2 There is evidence that some elements of intelligence can be taught. Intelligence, therefore, reflects the combined effects of both heredity and environment in the development of intellec- tual abilities.
9.7 Are there alternate views of intelligence? 9.7.1 Some psychologists are investigating the neural basis
for intelligence, especially the speed of processing various kinds of information and the size of brain areas related to intelligence.
9.7.2 Cognitive psychologists believe that successful intelli- gence depends on thinking and problem solving skills. Metacogni- tive skills, in particular, contribute greatly to intelligent behavior.
9.7.3 Artificial intelligence refers to any artificial system that can perform tasks that require intelligence when done by people. Two principal areas of artificial intelligence research on particular human skills are computer simulations and expert systems.
9.7.4 Many psychologists have begun to forge new, broader definitions of intelligence. Howard Gardner’s theory of multiple intelligences is a good example of this trend.
9.8 Is there a downside to intelligence testing? 9.8.1 Traditional IQ tests often suffer from a degree of cul-
tural bias. 9.8.2 African Americans are unfairly stigmatized because of
historically poor performance on standardized IQ tests. 9.8.3 It is wise to remember that IQ is merely an index of
intelligence and that intelligence is narrowly defined by most tests. 9.8.4 The use of standard IQ tests for educational place-
ment of students (especially into special education classes) has been prohibited by law in some states. Whether this is desirable and beneficial to students is currently being debated.
Fragile X Find out more about autism and fragile X syndrome from the National Fragile X Foundation.
Mind vs. Machine Read an amusing article about the Loebner Prize, one of the holy grails of artificial intelligence.
RuBot II, The Cubinator – A Rubik’s Cube Solving Robot Watch a robot solve a Rubik’s cube.
Multiple Intelligences in Education Learn more about Gardner’s theory of multiple intelligences and how it is being applied in education.
Be Careful of How You Define Intelligence An article about cross- cultural differences in intelligence.
The Bell Curve Flattened An article that summarizes objections to The Bell Curve.
The Genographic Project Trace your own ancestry.
The Knowns and Unknowns of Intelligence From the APA, what is known about intelligence and intelligence tests.
Web Resources Internet addresses frequently change. To find an up-to-date list of URLs for the sites listed here, visit your Psychology CourseMate.
IQ Tests Provides links to a number of IQ tests.
American Mensa Mensa is an international society that has one qualification only for membership: an IQ score in the top 2 percent of the population on a standardized intelligence test.
Gifted Children Learn more about giftedness from the National Association for Gifted Children.
Helping Your Highly Gifted Child Advice for parents of gifted children.
Intellectual Disabilities Learn more about intellectual disability from the American Association on Intellectual and Developmental Disabilities (AAIDD).
Down Syndrome Find out more about Down syndrome from the National Down Syndrome Society.
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