Assessing Intelligence
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The modern intelligence-testing movement began at the beginning
of the 20th century when France passed a law that all children
must attend school.
Binet and Simon began by assuming that all children follow that
same course of intellectual development, but that some develop
more rapidly. This is quantified as mental age, the level of
performance typically associated with a chronological age.
The purpose was to identify special needs children.
Louis Terman took it otherwise, by creating the Standford-Binet
test. For example, an 8-year-old who can read and write at the
level of a 10-year-old has an intelligence quotient (IQ) of 10/8 x
100 = 125.
Remember this for the exam!
Assessing Intelligence
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Modern IQ tests measure the test-taker's performance
relative to the average performance of others the same age.
Two-thirds of all test-takers fall between 85 and 115.
This led to eugenics, which lead to the 1924 U.S.
Immigration act the reduced Southern and Eastern
European immigrations to 1/5 of those for Northern and
Western Europe, all because their English wasn't so good.
Modern tests divide between achievement and aptitude, or
performance and prediction.
The Wechsler Adult Intelligence Scale (WAIS) has 15
subtests, including: similarities, vocabulary, block design,
and letter-number sequencing. It yields a g factor, plus
verbal comprehension, perceptual organization, working
memory, and processing speed.
Principles of Test Construction
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Test-makers first give their tests to a representative sample, then
measure your performance against that sample. This is
standardization.
If you test enough people (a sample must be greater than 20) with
a valid and reliable test, a normal or bell curve will be generated.
See Fig. 30.2 This is why I say that a class is perfectly normal, if
the class average is 68%; that average will match up to the
normal curve.
Strangely enough, test scores are improving. This is the Flynn
Effect (2010). Fig. 30.3. One answer (among many) is smaller
families and more parental investment. (Sunder et al., 2008).(m
396 c 382)
It may also be due to globalization, leading to 'hybrid vigor'.
(Mingroni, 2007).m 397 c 382)
Statistics of Measurement
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Reliable tests yield consistent scores. If two scores generally
agree, or correlate, the test is reliable. The higher the correlation
between the test-retest or split-half scores, the higher the test's
reliability. The Standford-Binet, the WAIS and the WISC all have
reliabilities of +.9.
Validity is the extent to which a test actually measures or predicts
what it promises.
Content validity shows that the test taps / accesses the pertinent
behavior, or criterion, such as a driver's exam.
Predictive validity is determined by the success with which a test
predicts the behavior it is designed to predict. It is assessed by
computing the correlation between test scores and the criterion
behavior. Also called criterion-related validity.
Predictive Validity?
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Intelligence test scores correlate closely with achievement tests:
+.81 for 70,000 English schoolchildren from 11 to 16. (Deary et
al., 2009).(m 397 c 382)
College entrance exams and graduate school exams correlate
even less: +.5 for the SAT and +.4 for the GRE.
This drop in correlation will be true even if the test has excellent
predictive validity with a more diverse range of students.
So, when we validate a test using a wide range of people but then
use it with a restricted range of people, it loses much of its
predictive validity.
Dynamics of Intelligence
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Cross-Sectional Evidence for Intellectual Decline with Age.
Here, researcher take a 'slice' through a population: all kinds of
people all at once. Wechsler concluded that “the decline of
mental ability with age is part of the general aging process of the
organism as a whole”.
Longitudinal Evidence of Intellectual Stability.
Schaie & Geiwitz (1982) studied intelligence longitudinally, by
tracking a cohort (such as the baby-boomers). Until late in life,
intelligence remained stable. Fig. 30.5 (m 399 c 384)
But, bright healthy people tend to live longer, skewing the data.
Adjusting for the loss of participants, reveals a steeper intelligence
decline, especially after 85. (Bayne et al., 1999).(m 399 c 384)
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In Wisdom tests, older adults hold their own. (Baltes et al., 1999).
(m 399 c 384)
Crystal Vs. Fluid
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This conflicting viewpoints from the same data are an example of
framing.
The solution, part 1: Intelligence is not a single trait, but rather
several distinct abilities. How we assess these is key.
Crystallized intelligence is our accumulated knowledge as reflected
in vocabulary and analogies tests, and it increases up to age 85.
Fluid intelligence, our ability to reason speedily and abstractly,
decreases around age 30. With age we lose recall memory and
processing speed. (Salthouse, 2009).(m 399 c 384)
But...our decisions also become less distorted by negative emotions
such as anxiety, depression or anger. (Blanchard-Fields, 2007).
Older adults show increased social reasoning, such as taking
multiple perspectives. (Grossman et al., 2010). See Fig. 30.6 (m
399 c 384)
When Do We Peak?
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These cognitive differences explain why older adults are less likely
to embrace new technologies.
And this research explains why different people in different careers
peak at different ages.
Mathematicians and scientists produce much of their creative
work during their late twenties and early thirties. Example: Bill
Gates was 21 and Steve Jobs 19 when they became the “Pirates
of Silicon Valley”.
In literature, history and philosophy, people tend to produce their
best work in their forties, fifties and beyond, after accumulating
more knowledge. (Simonton, 1990).(m 400 c 385)
Stability Over The Life Span
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Except for extremely impaired or very precocious children, casual
observation and intelligence tests before age 3 only modestly
predict children's future aptitudes. (Tasbihsazan et al., 2003).(m
400 c 385)
For example, children who are early talkers--speaking in sentences
typical of 3-year-olds at 20 months--are not especially likely to be
reading at age 4 1/2. (Crain-Thoreson & Dale, 1992).(m 400 c 385)
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After age 4, performance begins to predict adolescent and adult
scores.
Angoff, (1988) determined from 23,000 students that verbal scores
from SAT and GRE correlated +.86, and the same for the math
scores. However the verbal and math scores only had a modest
correlation to each other. (m 401 c 386)
The Deary 2004 Study
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Fig. 30.7: When Deary retested 80-year-old Scots, using an
intelligence test they taken as 11-year-olds, their scores across
seven decades correlated +.66. When 207 survivors were again
retested at age 87, the correlation with their age 11 scores was
+.51 (significant). Gow et al., 2011.(m 401 c 386)
Deary (2008) reports 4 possibilities: (1) intelligence means more
education, better jobs, healthier environment; (2) intelligence
encourages healthy living; (3) prenatal events or early childhood
illnesses might have influence both intelligence and health; (4)
genetics, as evidenced by fast reaction speeds, may foster both
intelligence and longevity.(m 401 c 386)
The Low Extreme
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Intellectual disability is defined as a condition of limited
mental ability, indicated by an intelligence score of 70 or
below and difficulty adapting to the demands of life.
The limitations are:
(1) conceptual skills, such as language, literacy, concepts of
money, time and number;
(2) social skills, such as interpersonal skills, social
responsibility, and the ability to follow basic rules and laws
(avoiding being victimized);
(3) practical skills, such as daily hygiene, occupational skills,
and the ability to travel (set itineraries).
Down syndrome is a disorder caused by an extra
chromosome 21.
The High Extreme
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Contrary to the popular notion that intellectually gifted children are
frequently maladjusted, they are healthy, well-adjusted, and
academically successful (Koenen et al., 2009).(m 403 c 388)
Youths who aced the math SAT at age 13--top .25%--at age 33
were twice as likely to have patents as those in the bottom quarter
of the top 1%. (Wai et al., 2005).(m 403 c 388)
1% of Americans complete a Ph.D. But among those scoring in the
top 1 in 10,000--using only a two-hour SAT at age 12 or 13--more
than half have done so. (Lubinski, 2009).(m 403 c 388)
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However, those labelled 'ungifted' may be influenced to become
so. (Lipsey & Wilson, 1993).(m 403 c 389)
By promoting appropriate developmental placement suited to each
child's talents, we can promote both equality and excellence.
(Colangelo et al., 2004). (m 403 c 389)