CHAPTER 10 – Intelligence
- Intelligence is the ability to acquire knowledge, to think and reason
effectively, and to deal adaptively with the environment. Because cultural
environments differ in the skills most important for adaptation, cultural
conceptions of intelligence may differ markedly.
- Galton’s studies of hereditary genius and Binet’s methods for measuring
differences in children’s mental skills were important historical
milestones in the study of intelligence.
- The psychometric approach to intelligence attempts to map the structure
of intellect and establish how many different classes of mental ability
underlie test performance. A newer approach, the cognitive processes
approach, focuses on the specific thought processes that underlie mental
- Factor analysis can be applied to correlations among test scores to
identify clusters of measures that correlate highly with one another and
therefore are assumed to have a common underlying factor, such as
verbal ability or mathematical reasoning.
- Spearman believed that intelligence is determined both by specific
cognitive abilities and by a general intelligence (g) factor that constitutes
the core of intelligence. Thurstone disagreed, viewing intelligence as a
set of specific abilities. Thurstone’s position is best supported by
observed distinctions between verbal and spatial abilities.
- Cattell and Horn differentiated between crystallized intelligence, the
ability to apply previously learned knowledge to current problems, and
fluid intelligence, the ability to deal with novel problem-solving situations
for which personal experience does not provide a solution. They argued
that over our lifespan, we show a progressive shift from using fluid
intelligence to using crystallized intelligence as we attain wisdom.
- Carroll’s three-stratum model is based on re-analyses of hundreds of
data sets. Mental abilities are represented at 3 levels, with general
intelligence (g) at the apex and highly specific cognitive and perceptual skills at its base. Carroll’s model may be the most accurate psychometric
representation of human cognitive abilities.
- Cognitive process theories of intelligence focus on the elementary
information-processing abilities that contribute to intelligence.
Sternberg’s Triarchic theory of intelligence includes a components sub-
theory that addresses the specific cognitive processes that underlie
- Sternberg and Gardner maintain that there are distinct forms of
intelligence beyond the traditional concept. Sternberg differentiates
between analytical, practical, and creative intelligence, and Gardner
proposes 9 different kinds of intelligence. The theory of emotional
intelligence refers to people’s ability to read and respond appropriately to
others’ emotions, to motivate themselves, and to be aware and in control
of their emotions.
- Most modern intelligence tests, such as the Wechsler scales, measure an
array of different mental abilities. In addition to a global, or full-scale, IQ,
they provide scores for each sub-test and summary scores for broader
abilities, such as verbal and performance IQs. Some recent tests are
derived directly from theories of intelligence. The Kaufman scale provides
separate scores for crystallized and fluid intelligence, and Sternberg’s
STAT measures analytical, practical, and creative intelligence.
- Achievement tests measure what has already been learned, whereas
aptitude tests are assumed to measure potential for future learning and
performance. Most intelligence tests measure combinations of
achievement and aptitude, for it is difficult to separate past learning and
future learning potential.
- Three important standards for psychological tests are reliability
(consistency of measurement over time, within tests, and across scorers),
validity (successful measurement of the construct and acceptable
relations with relevant criterion measures), and standardization
(development of norms and standard testing conditions).
- IQ scores successfully predict a range of academic, occupational, and life
outcomes, including how long people live. Such findings indicate that
intelligence tests are measuring important adaptational skills.- The Flynn Effect refers to the notable rise in intelligence test scores over
the past century, possibly due to better living conditions, more schooling,
or more complex environments.
- In dynamic testing, standard test administration is followed by feedback
and suggestions from the examiner and a re-taking of the test, thus
allowing an assessment of how well the person profits from feedback and
how intellectual skills might be coached in the future. Dynamic testing
provides information that static testing does not, and re-test scores
sometimes relate more strongly to criterion measures.
- Intelligence testing in non-Western cultures is a challenge. One approach
is to use tests that are not tied to any culture’s knowledge base. Another
approach is to devise tests of the abilities that are important to
adaptation in that culture. These culture-specific abilities may bear little
relation to the mental skills assessed by Western intelligence tests.
- Recent physiological evidence suggests that the brains of intelligent
people may function more efficiently. Brain size is not significantly
related to intelligence, but the neural networks laid down in the process
of brain development may be extremely important. One current theory is
that differences in brain plasticity may underlie intelligence.
- Intelligence is determined by interacting hereditary and environmental
factors. Genes account for between 50-70% of population variation in IQ.
Shared family environment accounts for perhaps 1/4 to 1/3 of the
variance during childhood, but its effects seem to dissipate as people
age. Educational experiences also influence mental skills. Heredity
establishes a reaction range with upper and lower limits for intellectual
potential. Environment affects the point within that range that will be
- Intervention programs for disadvantaged children have positive effects on
later achievement and life outcomes if they begin early in life and are
applied intensively. They have little effect when applied after school
begins or with middle- or upper-class children.
- Heritability estimates of intelligence can vary, depending on sample
characteristics. In impoverished families, shared environment was more
important than genes, whereas the opposite was found in affluent families. Twin studies also show that heritability effects on intelligence
increase in adulthood.
- Cultural and ethnic differences in intelligence exist (though they may be
narrowing), but the relative contributions of genetic and environmental
factors are still