Chapter 8: Intelligence and Academic Achievement
What is Intelligence?
o Intelligence can be described at three levels of analysis: as one thing, as a few things, or as
o Intelligence as a Single Trait
Some researchers view intelligence as a simple entity that influences all aspects of
g (general intelligence): the part of intelligence that is common to all intellectual
Measures of g correlate positively with school grades and achievement test
G correlates with information-processing speed, with speed of neural transmission,
and with brain volume.
o Intelligence as a Few Basic Abilities
There are two types of intelligence:
Fluid intelligence: ability to think on the spot to solve novel problems.
o Ex. Drawing inferences and understanding relations between
concepts that have not been encountered previously.
o Related to:
Brain size- size of the cortex
Amount of activation of specific brain areas- prefrontal
cortex and the parietal area, on tasks that require attention
and problem solving.
o Peaks in early adulthood, around 20, and slowly declines thereafter
Crystallized intelligence: factual knowledge about the world
o Ex. Word meanings, state capitals, answers to arithmetic problems,
o Reflects long-term memory for prior experiences and is closely
related to verbal ability
o Hippocampus is the crucial brain region
o Increases steadily from early in life to old age
Distinction between fluid and crystallized intelligence is supported by the
fact that tests of each type correlate more highly with each other than they
do with tests of the other type.
Primary mental abilities: seven abilities said by Thurstone to be crucial to
o Word fluency, verbal meaning, reasoning, spatial visualization,
numbering, rote memory, perceptual speed.
o Intelligence as Numerous Processes
Viewing intelligence as “many things” allows more precise specification on the
processes involved in intelligent behavior. o A Proposed Resolution
Three-stratum theory of intelligence: Carroll’s model of intelligence, including g at
the top of the hierarchy, eight moderately general abilities in the middle, and many
specific processes at the bottom
Generalized intelligence influences all of the moderately general abilities, and both
general intelligence and the moderately general abilities influence the specific
All three levels of analysis are necessary to account for the totality of facts about
o Binet- the best way to measure intelligence is by observing people’s actions on tasks that
require a variety of types of intelligence: problem solving, memory, language
comprehension, spatial reasoning, and so on.
o The Contents of Intelligence Tests
Wechsler Intelligence Scale for Children (WISC): a widely used test designed to
measure the intelligence of children 6 years and older
General ability, several moderately general abilities, and a large number of
o The Intelligence Quotient (IQ)
IQ (intelligence quotient): a summary measured used to indicate a child’s intelligence
relative to that of other children of the same age
Normal distribution: a pattern of data in which scores fall symmetrically around a
mean value, with most scores falling close to the mean and fewer and fewer scores
farther from it
Standard deviation: a measure of the variability of scores in a distribution; in a
normal distribution, 68% of scores fall within 1 standard deviation of the mean and
95% of scores fall within 2 standard deviations.
Continuity of IQ Scores
Changes are due to in part by random variation.
Testing Infants’ Intelligence
Difficult because many abilities that play large roles in later intelligence are
only minimally developed in infancy and cannot be reliably measured.
IQ Scores as Predictors of Important Outcomes
o IQ scores correlate positively and quite strongly with school grades and achievement test
performance, and also with long-term educational achievement.
o There are other predictors of IQ
Self-discipline: the ability to inhibit actions, follow rules, and avoid impulse reactions
Practical intelligence: mental abilities not measured on IQ tests but important for
success in many situations, such as accurately reading other people’s emotions and
intentions and motivating others to work effectively as a team
Characteristics of the environment Genes, Environment, and the Development of Intelligence
o Qualities of the Child
Genetic Contributions to Intelligence
Genes have a substantial influence on intelligence which varies greatly with
o Relatively modest in early childhood and becomes very large by
adolescence and adulthood.
Some genetic processes do not exert their effects on IQ until later childhood
Children’s increasing independence with age allows them greater freedom
to choose environments that are compatible with their own genetically
Environments children encounter are influenced by their genotype, which
involved three types of effects:
o Passive: arise when children are raised by their biological parents
Occur because of the overlap between their parent’s genes
and their own
o Evocative: emerge through children’s eliciting or influencing other
o Active: involve children choosing environments that they enjoy.
o Influences of the Immediate Environment
HOME (Home Observation for Measurement of the Environment)
o Samples various aspects of children’s home life, including the
organization and safety of living space; the intellectual stimulation
offered by parents; whether children have books of their own; the
amount of parent-child interaction; the parents’
o Influence of Society
Flynn effect: the rise in average IQ scores that has occurred over the past 75 years in
Effects of Poverty
The more years children spend in poverty, the lower their IQs tend to be
Negative effects due to:
o Inadequate diet
o Reduced access to health services
o Inadequate parenting
o Insufficient intellectual stimulation
o Insufficient emotional support
Race, Ethnicity, and Intelligence The average IQ scores of children of different racial and ethnic group do
o Asian-American children 3 points higher than Euro-Americans.
o Euro-Americans are 11 points higher than African-Americans
o Latino and American I