CHAPTER 10: Intelligence
1. How did Galton and Binet differ in their approaches to measuring mental abilities?
Galton showed through the study of family trees that eminence and genius seemed to occur within
certain families. He pioneered the study of intelligence with his studies of hereditary genius.
Galton's research convinced him that eminent people had “inherited mental constitutions” that made
them more fit for thinking than their less successful counterparts. Exhibiting his own belief bias, Galton
dismissed the fact that the more successful people he studied almost invariably came from privileged
Galton then attempted to demonstrate a biological basis for eminence by showing that people who were
more socially and occupationally successful would also perform better on a variety of laboratory tasks
thought to measure the “efficiency of the nervous system.” He developed measures of reaction speed,
hand strength, and sensory acuity. He even measured the size of people's skulls, believing that skull
size reflected brain volume and hence intelligence.
In time, Galton's approach to mental-skills measurement fell into disfavor because his measures of
nervous-system efficiency proved unrelated to socially relevant measures of mental ability, such as
academic and occupational success. Nonetheless, Galton's work created an interest in the measurement
of mental abilities, setting the stage for the pioneering work ofAlfred Binet.
Alfred Binet developed the first intelligence test to assess the mental skills of French school children.
His test launched the modern intelligence-testing movement.
In developing his tests, Binet made two assumptions about intelligence: First, mental abilities develop
with age. Second, the rate at which people gain mental competence is a characteristic of the person and
is fairly constant over time. In other words, a child who is less competent than expected at age 5 should
also be lagging at age 10.
To develop a measure of mental skills, Binet asked experienced teachers what sorts of problems
children could solve at ages 3, 4, 5, and so on, up through the school years. He then used their answers
to develop a standardized interview in which an adult examiner posed a series of questions to a child to
determine whether the child was performing at the correct mental level for his or her age (Table 10.1).
The result of the testing was a score called the mental age. For instance, if an 8-year-old child could
solve problems at the level of the average 10-year-old, the child would be said to have a mental age of
10. For the French school system, the practical implication was that educational attainment could be
enhanced if placement in school were based at least in part on the child's mental age.An 8-year-old
child with a mental age of 6 could hardly be expected to cope with the academic demands of a normal
classroom for 8-year-olds.
2. Why do intelligence tests no longer use the concept of mental age? How is the IQ now
Today's tests no longer use the concept of mental age.Although the concept works pretty well for
children, many of the basic skills measured by intelligence tests are acquired by about age 16 through
normal life experiences and schooling, so that Stern's quotient is less useful for adults. Moreover, some
intellectual skills show an actual decline at advanced ages. If we applied Stern's definition of IQ to a
20-year-old who performed at the typical level of an 80-year-old, we would have to say that the 20-
year-old's IQ was 400! To deal with these problems, today's intelligence tests provide an “IQ” score
that is not a quotient at all. Instead, it is based on a person's performance relative to the scores of other
people the same age, with a score of 100 corresponding to the average performance of that age group 3. Differentiate between crystallized and fluid intelligence, and indicate their relation to
types of memory.
Fluid intelligence is the capacity to think logically and solve problems in novel situations, independent
of acquired knowledge. It is the ability to analyze novel problems, identify patterns and relationships
that underpin these problems and the extrapolation of these using logic. It is necessary for all logical
problem solving, e.g., in scientific, mathematical and technical problem solving. Fluid reasoning
includes inductive reasoning and deductive reasoning. Fluid intelligence is related to short-term
memory and brain regions relating to attention.
Crystallized intelligence is the ability to use skills, knowledge, and experience. It does not equate to
memory or knowledge, but it does rely on accessing information from long-term memory.
Crystallized intelligence is one’s lifetime or intellectual achievement, as demonstrated largely through
one's vocabulary and general knowledge. T