Chapter 9: Intelligence and Psychological Testing
1. List and describe the principal categories of psychological tests.
• Mental ability test
Intelligence test: measure general mental ability. Intended to assess intellectual
potential rather than previous learning or accumulated knowledge.
Aptitude tests: assess specific types of mental abilities. Designed to measure potential
more than knowledge but break mental ability into separate components
Achievement tests: gauge a person’s mastery and knowledge of various subjects.
Have a specific focus but are supposed to measure previous learning instead of
• Personality Test: measure various aspects of personality, including motives, interests,
values and attitudes
2. Explain the concepts of standardization and test norms.
• Standardization: refers to the uniform procedures used in the administration and scoring of a test.
• Test norms: provide information about where a score on a psychological test ranks in relation to
other scores on that test.
3. Explain the meaning of test reliability and how it is estimated.
• Reliability: refers to the measurement consistency of a test (or other kinds of measurement
• Test-retest reliability: estimated by comparing subjects’ scores on two administrations of a test.
• Correlation Coefficient: is a numerical index of the degree of relationship between two variables
4. Explain the three types of validity and how they are assessed.
• Validity: refers to the ability of a test to measure what it was designed to measure.
Content validity: refers to the degree to which the content of a test is representative of
the domain it’s supposed to cover. Evaluated with logic more than with statistics. 2
Criterion-related Validity: is estimated by correlating subjects’ scores on a test with
their scores on an independent criterion (another measure) of the trait assessed by the
Construct validity: the extent to which there is evidence that a test measures a
particular hypothetical construct (abstract qualities like creativity, intelligence,
extraversion or independence)
5. Summarize the contributions of Galton and Binet to the evolution of intelligence testing.
• Sir Francis Galton (late 19 century)
studied family trees and found that success and eminence appeared consistently in some
families over generations.
Wrote “Hereditary Genius” with the conclusion that success runs in families because of great
intelligence that is passed down from generation to generation through genetic inheritance
(Galton was half-cousin to Charles Darwin)
Assumed that the contents of the mind are built out of elementary sensations and he
hypothesized that exceptionally bright people should exhibit exceptional sensory acuity
Tried to assess innate mental ability by measuring simple sensory processes, sensitivity to
high-pitched sounds, colour perception and reaction time
Coined the phrase “nature versus nurture” to refer to the hereditary-environment issue
Invented the concepts of correlation and percentile test scores
• Alfred Binet (1904)
Commissioned by France on education to devise a test to identify mentally subnormal
children (wanted to single out youngsters in need of special training and avoid
complete reliance on teachers’ evaluations which is often subjective and biased)
1905, along with colleague Theodore Simon, published the first useful test of general
mental ability. Loaded with items that required abstract reasoning skills, rather than the
sensory skills Galton had measured. A success because it was inexpensive, easy to
administer, objective and capable of predicting children’s performance in school fairly
Binet-Simon scale expressed a child’s score in terms of “mental level” or “mental
age”—indicated that he or she displayed the mental ability typical of a child of that
chronological (actual) age.
6. Summarize the contributions of Terman and Wechsler to the evolution of intelligence
• Lewis Terman (1916)
Terman and colleagues at Stanford University worked on a major expansion and
revision of Binet’s test which led to the publication of the Stanford-Binet Intelligence
Scale which included the “Intelligence Quotient” (IQ)—is a child’s mental age divided
by chronological age, multiplied by 100
• David Wechsler (1939)
Chief psychologist at New York’s Bellevue Hospital, charged with overseeing the
psychological assessment of thousands of adult patients but found the Stanford-Binet
somewhat unsatisfactory for this purpose.
Published the first high-quality IQ test designed specifically for adults, which came to
be known as the Wechsler Adult Intelligence Scale (WAIS)
Made his scales less dependent on subjects’ verbal ability than the Stanford-Binet by
including many items that required nonverbal reasoning. To highlight the distinction
between verbal and nonverbal ability, he formalized the computation of separate
scores for verbal IQ, performance (nonverbal) IQ, and full-scale (total) IQ
Discarded the intelligent quotient in favour of a new scoring scheme based on the
7. Summarize evidence about the structure of intelligence, including correlations among
biological and cognitive factors.
• Factor analysis— invented by Charles Spearman, a complicated statistical procedure, correlations
among many variables are analyzed to identify closely related clusters of variables. 4
• Scholastic Aptitude Test (SAT)—proposed by L.L. Thurstone, an American psychologist who
concluded that intelligence involves multiple abilities. Seven independent factors called “primary
mental abilities”: word fluency, verbal comprehension, spatial ability, perceptual speed, numerical
ability, inductive reasoning and memory
• Fluid intelligence—involves reasoning ability, memory capacity, and speed of information
• Crystallized intelligence—involves ability to apply acquired knowledge and skills in problem
8. Explain the meaning of an individual’s score on a modern intelligence test.
• Normal distribution—is a symmetric, bell-shaped curve that represents the pattern in which many
characteristics are dispersed in the population
• Deviation IQ scores—locates subjects precisely within the normal distribution, using the standard
deviation as the unit of measurement
• Mean distribution is set at 100
• Standard deviation (SD) is set at 15
9. Discuss the reliability and validity of modern IQ test scores.
• In comparison to most other types of psychological tests, IQ tests are exceptionally reliable
• They sample behaviour which may lead an unrepresentative score.
• Low motivation or high anxiety may drag a person’s score down on a particular occasion
• IQ test are valid when measure academic work but if used to assess intelligence in a broader
sense, then it is questionable
• 3 categories of Intelligent behaviour: verbal intelligence, practical intelligence and social
• IQ tests focus on cognitive abilities but do not predict rational thinking and effective decision
making in the real world
10. Discuss how well intelligence tests predict vocational success. 5
• People who score high on IQ tests are more likely than those who score low to end up in high-
• Research suggests that (predictors of performance within a particular occupation):
There is a substantial correlation (about 0.50) between IQ scores and job
This correlation varies somewhat depending on the complexity of a job’s
requirements but does not disappear even for low-level jobs
This association holds up even when workers have more experience at their jobs
Measures of specific mental abilities and personality traits are much less predictive
of job performance than measures of intelligence
11. Discuss the use of IQ tests in non-Western cultures.
• IQ tests are not widely used in most non-western cultures
• Different cultures have different conceptions of what intelligence is and value different mental
12. Describe how intellectual disability is defined and divided into various levels.
• Intellectual disability—refers to the subnormal general mental ability accompanied by deficiencies
in adaptive skills, originating before age 18
Conceptual skills—managing money, writing a letter
Social skills—making friends, coping with others’ demands
Practical skills—preparing meals, using transportation, shopping
• Levels of intellectual disability:
Mild—51-70 IQ Range; Grade 6 (maximum) by late teens; special education helpful;
can be self-supporting in nearly normal fashion if environment is stable and supportive;
may need help with stress
Moderate—36-50 IQ Range; Grade 2-4 by late teens; special education necessary;
can be semi-independent in sheltered environment; needs help with even mild stress 6
Severe—20-35 IQ Range; limited speech; toilet habits, and so forth with systematic
training; can help contribute to self-support under total supervision
Profound—below 20 IQ Range; little or no speech; not toilet-trained; relatively
unresponsive to training; requires total care
13. Discuss what is known about the causes of intellectual disability.
• Down syndrome—marked by distinctive physical characteristics (slanted eyes, stubby limbs, and
thin hair); carry an extra chromosome
• Fragile X Syndrome (FXS)—FRM 1 gene causes hereditary intellectual disability where FXS is
mutated in the inherited gene; characterized by an inhibitory control deficit which may lead to
activation of neural connections irrelevant to the context or task facing the individual
• Phenylketonuria—a metabolic disorder (due to an inherited enzyme deficiency) that can lead to
intellectual disability if it is not caught and treated in infancy
• Hydrocephaly—an excessive accumulation of cerebrospinal fluid in the skull destroys brain tissue
and causes retardation
• More apparent in children in lower socioeconomic class due to marital instability, parental
neglect, inadequate nutrition and medical care, and lower-quality schooling
• Savant syndrome—Kim Peek: born with enlarged head, malformed cerebellum, left
hemisphere damage and complete absence of the corpus callosum; diagnosed with
autism; have excellent memory; no known causes and characteristics
14. Discuss the role of IQ tests in the identification of gifted children.
• Giftedness should not be equated with high intelligence and that schools should not rely heavily
on IQ tests to select gifted children
• Efforts to identify gifted children focus almost exclusively on IQ scores and rarely consider
qualities such as creativity, leadership, or special talent
• Upper 2-3 percent of the IQ distribution to be gifted. Minimum IQ for gifted programs is around 130
15. Describe the characteristics of gifted individuals and factors relating to adult
achievement by the gifted. 7
• Ellen Winner—profoundly gifted children (above 180 IQ) are often introverted and socially isolated
and that the incidence of interpersonal and emotional problems is twice as high as in other
• Gifted youngsters typically become very successful. Most however do not make genus-level
contributions because such achievements depend on a combination of high intelligence, creativity
• “drudge theory”—suggests that determination, hard work, and intensive training are the key to
• Extraordinary achievement also requires rare, innate talent
16. Summarize empirical evidence that heredity affects intelligence.
• Twin Studies—identical twins tend to be similar in intelligence (0.86) and fraternal twins also tend
to be similar in intelligence but noticeably less so than identical twins (0.60) Therefore IQ is
inherited to a considerable degree and that the influence of heredity increases with age.
• Adoption Studies—there is more than chance similarity between adopted children and their
17. Discuss estimates of the heritability of intelligence and their limitations.
• Heritability ratio—is an estimate of the proportion of trait variability in a population that is
determined by variations in genetic inheritance. For example, the heritability of height is estimated
to be around 90% while the heritability of weight is around 85%
• Heritability of IQ is as high as 80% (Arthur Jensen) but in recent years, the consensus estimates
Heritability estimate is a group statistic—based on studies of trait variability within a
specific group—therefore cannot be applied meaningfully to individuals
A specific trait’s heritability may vary from one group to another depending on a
variety of factors
It is crucial to understand that “there really is no single fixed value that represents
any true, constant value for the heritability of IQ or anything else” 8
18. Describe various lines of research that indicate that environment affects intelligence.
• Adoption studies
Adopted children show some resemblance to their adoptive parents in IQ
Siblings reared together are more similar in IQ than siblings reared apart. This is true
even for identical twins
Entirely unrelated children who are raised in the same home also show a significant
resemblance in IQ
• Environmental Deprivation and Enrichment
“Cumulative deprivation hypothesis”- studied children consigned to understaffed
orphanages and children raised in the poverty and isolation of the back hills of the