The dove counterbalance intelligence test

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?

303

Intelligence

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Chapter 9304

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.

BRIDGES

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

Intelligence tests

Modern intelligence tests are widely used to measure cognitive abilities. When properly administered, such tests provide an operational definition of intelligence.

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• 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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Intelligence 305

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.

BRIDGES

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

Y

B

A

X

Driver

• 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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Chapter 9306

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.

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Intelligence 307

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?

Perceptual Reasoning

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.

Working Memory

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?

Processing Speed

Symbol Search Match symbols appearing in separate groups.

NO

NO

NO

Symbol Search

Coding Fill in the symbols: 3 21244 1 31 2 3 4

X III I 0

■ TABLE 9.1

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Chapter 9308

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?

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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

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Intelligence 309

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.)

MA CA

� 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:

12 15

� 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.)

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Chapter 9310

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

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• 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?

Self-Reflect

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.

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Intelligence 311

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

Pe rc

en t

Intellectually disabled

Borderline

40 60 80 100 120 140 160 180

Mean = 101.8 IQ

20

16

12

8

24

4

Dull normal

Average

Bright normal

Superior

Very superior

• Figure 9.4 Distribution of Stanford-Binet Intelligence Test scores for 3184 children. (Adapted from Terman & Merrill, 1937/1960.)

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Chapter 9312

(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).

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Intelligence 313

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.

BRIDGES

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.

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Chapter 9314

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

IQ Range

Degree of Intellectual Disability

Educational Classification

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).