Chapter 9 Intelligence and Psychological Testing

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Chapter 9Intelligence and Psychological Testing
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Key Concepts in Psychological Testing

• Standardization
• Test norms
• Standardization group
• Reliability
• Correlation coefficient
• Validity
• Content validity
• Criterion-related validity
• Construct validity

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Figure 9.2 Test-retest reliability. Subjects
scores on the first administration of an
assertiveness test are represented on the left,
and their scores on a second administration of
the same test a few weeks later are shown on the
right. If subjects obtain similar scores on both
administrations, as in the left graph, the test
measures assertiveness consistently and has high
test-retest reliability. If they get very
different scores on the second administration, as
in the right graph, the test has low reliability.
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Figure 9.3 Correlation and reliability. As
explained in Chapter 2, a positive correlation
means that two variables covary in the same
direction a negative correlation means that two
variables covary in the opposite direction. The
closer the correlation coefficient gets to either
1.00 or 1.00, the stronger the relationship. At
a minimum, reliability estimates for
psychological tests must be moderately high
positive correlations. Most reliability
coefficients fall between 70 and .95.
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Figure 9.4 Criterion-related validity. To
evaluate the criterion-related validity of a
pilot aptitude test, a psychologist would
correlate subjects test scores with a criterion
measure of their aptitude, such as ratings of
their performance in a pilot training program.
The validity of the test is supported if a
substantial correlation is found between the two
measures. If little or no relationship exists
between the two sets of scores, the data do not
provide support for the validity of the test.
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Figure 9.5 Construct validity. Psychologists
evaluate a scales construct validity by studying
how scores on the scale correlate with a variety
of variables. For example, some of the evidence
on the construct validity of the Expression Scale
from the Psychological Screening Inventory is
summarized here. This scale is supposed to
measure the personality trait of extraversion. As
you can see on the left side of this network of
correlations, the scale correlates negatively
with measures of social introversion, social
discomfort, and neuroticism, just as one would
expect if the scale is really tapping
extraversion. On the right, you can see that the
scale is correlated positively with measures of
sociability and self-acceptance and another index
of extraversion, as one would anticipate. At the
bottom, you can see that the scale does not
correlate with several traits that should be
unrelated to extraversion. Thus, the network of
correlations depicted here supports the idea that
the Expression Scale measures extraversion.
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Principle Types of Psychological Tests

• Mental ability tests
• Intelligence general
• Aptitude tests specific
• Personality scales
• Measure motives, interests, values, and attitudes

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The Evolution of Intelligence Testing

• Sir Francis Galton (1869)
• Hereditary Genius
• Alfred Binet and Theodore Simon (1905)
• Binet-Simon Intelligence Scale
• Mental age
• Lewis Terman (1916)
• Stanford-Binet Intelligence Scale
• Intelligence Quotient (IQ) MA/CA x 100
• David Wechsler (1955)
• Wechsler Adult Intelligence Scale

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Figure 9.7 The normal distribution. Many
characteristics are distributed in a pattern
represented by this bell-shaped curve. The
horizontal axis shows how far above or below the
mean a score is (measured in plus or minus
standard deviations). The vertical axis is used
to graph the number of cases obtaining each
score. In a normal distribution, the cases are
distributed in a fixed pattern. For instance,
68.26 of the cases fall between 1 and 1
standard deviation. Modern IQ scores indicate
where a persons measured intelligence falls in
the normal distribution. On most IQ tests, the
mean is set at an IQ of 100 and the standard
deviation at 15. Thus, an IQ of 130 means that a
person scored 2 standard deviations above the
mean. Any deviation IQ score can be converted
into a percentile score, which indicates the
percentage of cases obtaining a lower score. The
mental classifications at the bottom of the
figure are descriptive labels that roughly
correspond to ranges of IQ scores.
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Figure 9.8 Laypersons conceptions of
intelligence. Robert Sternberg and his colleagues
(1981) asked participants to list examples of
behaviors characteristic of intelligence. The
examples tended to sort into three groups that
represent the three types of intelligence
recognized by the average person verbal
intelligence, practical intelligence, and social
intelligence.
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Reliability and Validity of IQ tests

• Exceptionally reliable correlations into the
  .90s
• Qualified validity valid indicators of
  academic/verbal intelligence, not intelligence in
  a truly general sense
• Correlations
• .40s-.50s with school success
• .60s-.80s with number of years in school
• Predictive of occupational attainment, debate
  about predictiveness of performance

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Extremes of Intelligence Mental Retardation

• Diagnosis based on IQ and adaptive testing
• IQ 2 or more SD below mean
• Adaptive skill deficits
• Origination before age 18
• 4 levels mild, moderate, severe, profound
• Mild most common by far
• Causes
• Environmental vs. Biological

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Figure 9.9 The prevalence and severity of mental
retardation. The overall prevalence of mental
retardation is roughly 1 to 3 of the general
population. The vast majority (85) of the
retarded population is mildly retarded. Only
about 15 of the retarded population falls into
the subcategories of moderate, severe, or
profound retardation.
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Extremes of Intelligence Giftedness

• Identification issues ideals vs. practice
• IQ 2 SD above mean standard
• Creativity, leadership, special talent?
• Stereotypes weak, socially inept, emotionally
  troubled
• Lewis Terman (1925) largely contradicted
  stereotypes
• Ellen Winner (1997) moderately vs. profoundly
  gifted
• Giftedness and high achievement beyond IQ

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Figure 9.27 Estimated prevalence of psychological
disorders among people who achieved creative
eminence. Ludwig (1995) studied biographies of
1004 people who had clearly achieved eminence in
one of 18 fields and tried to determine whether
each person suffered from any specific mental
disorders in his or her lifetime. The data
summarized here show the prevalence rates for
depression and for a mental disorder of any kind
for four fields where creativity is often the key
to achieving eminence. As you can see, the
estimated prevalence of mental illness was
extremely elevated among eminent writers,
artists, and composers (but not natural
scientists) in comparison to the general
population, with depression accounting for much
of this elevation.
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Intelligence Heredity or Environment?

• Heredity
• Family and twin studies
• Heritability estimates
• Environment
• Adoption studies
• Cumulative deprivation hypothesis
• The Flynn effect
• Interaction
• The concept of the reaction range

Launch Video
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Figure 9.15 Reaction range. The concept of
reaction range posits that heredity sets limits
on ones intellectual potential (represented by
the horizontal bars), while the quality of ones
environment influences where one scores within
this range (represented by the dots on the bars).
People raised in enriched environments should
score near the top of their reaction range,
whereas people raised in poor-quality
environments should score near the bottom of
their range. Genetic limits on IQ can be inferred
only indirectly, so theorists arent sure whether
reaction ranges are narrow (like Teds) or wide
(like Chriss). The concept of reaction range can
explain how two people with similar genetic
potential can be quite different in intelligence
(compare Tom and Jack) and how two people reared
in environments of similar quality can score
quite differently (compare Alice and Jack).
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Figure 9.12 Studies of IQ similarity. The graph
shows the mean correlations of IQ scores for
people of various types of relationships, as
obtained in studies of IQ similarity. Higher
correlations indicate greater similarity. The
results show that greater genetic similarity is
associated with greater similarity in IQ,
suggesting that intelligence is partly inherited
(compare, for example, the correlations for
identical and fraternal twins). However, the
results also show that living together is
associated with greater IQ similarity, suggesting
that intelligence is partly governed by
environment (compare, for example, the scores of
siblings reared together and reared apart). (Data
from McGue et al., 1993)
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Figure 9.13 The concept of heritability. A
heritability ratio is an estimate of the portion
of variation in a trait determined by
hereditywith the remainder presumably determined
by environmentas these pie charts illustrate.
Typical heritability estimates for intelligence
range between a high of 70 and a low of 50,
although some estimates have fallen outside this
range. Bear in mind that heritability ratios are
estimates and have certain limitations that are
discussed in the text.
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Cultural Differences in IQ

• Heritability as an Explanation
• Aurthur Jensen (1969)
• Herrnstein and Murray (1994) The Bell Curve
• Environment as an Explanation
• Kamins cornfield analogy

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Figure 9.16 Genetics and between-group
differences on a trait. Kamins analogy (see
text) shows how between-group differences on a
trait (the height of corn plants) could be due to
environment, even if the trait is largely
inherited. The same reasoning presumably applies
to ethnic group differences in the trait of human
intelligence.
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Figure 9.18 Asian Americans academic success. On
various measures of educational success, such as
the high school graduation rates shown here, the
performance of Asian American students tends to
exceed that of other ethnic groups in the United
States. More research is needed on the matter,
but most theorists believe that cultural factors
are responsible for Asian Americans academic
prowess. (Data from Sue Okazaki, 1990)
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New Directions in the Study of Intelligence

• Increased emphasis on specific abilities
• Moving beyond Spearmans g
• Guilfords 150 distinct mental abilities.
• Fluid vs crystallized intelligence
• Biological Indexes of Intelligence
• Reaction time and inspection time
• Cognitive Conceptualizations of intelligence
• Sternbergs triarchic theory

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Figure 9.19 Spearmans g.  In his analysis of the
structure of intellect, Charles Spearman found
that specific mental talents (S1, S2, S3, and so
on) were highly intercorrelated. Thus, he
concluded that all cognitive abilities share a
common core, which he labeled g for general
mental ability.
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Figure 9.20 Guilfords model of mental
abilities.  In contrast to Spearman (see Figure
9.19), J. P. Guilford concluded that intelligence
is made up of many separate abilities. According
to his analysis, people may have as many as 150
distinct mental abilities that can be
characterized in terms of the operations,
contents, and products of intellectual activity.
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Figure 9.23 Sternbergs triarchic theory of
intelligence. Sternbergs model of intelligence
consists of three parts the contextual
subtheory, the experiential subtheory, and the
componential subtheory. Much of Sternbergs
research has been devoted to the componential
subtheory, as he has attempted to identify the
cognitive processes that contribute to
intelligence. He believes that these processes
fall into three groups metacomponents,
performance components, and knowledge-acquisition
components.
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