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Chapter 8: Intelligence & Individual Differences in Cognition
WHAT IS INTELLIGENCE?
• Intelligence encompasses an individual’s ability to understand complex ideas, to adapt effectively to the
environment, to learn from experience, to engage in various forms of reasoning, and to overcome
obstacles through mental effort
• Psychometricians are psychologists who specialize in measuring psychological characteristics such
as intelligence and personality. This begins by administering a test to many individuals to look for
patterns in performance by correlation – if changes in performance on one factor are accompanied by
changes in another, one assumes the two are due to the same attribute or factor.
• General Intelligence (Spearman): Created factor analysis of s factors for specific abilities, skills and
talents. General intelligence applicable to various situations, tasks, or problems so performance tends to
be consistent. Spearman believe the general factor for intelligence, g, was responsible for performance
on all mental tests.
• John Carroll: Hierarchical theory of intelligence with both general and specific components. For
example, general intelligence can be divided into 8 broad categories of intellectual skill.
• Raymond Cattell: Fluid intelligence, the ability to perceive relations among stimuli; and crystallized
intelligence, which consists of culturally-influenced accumulated knowledge and skills, such as reading
• Crystallized intelligence continues to increase with age and is dependent on education, while fluid
intelligence is more innate and peaks at 20-25. These two factors are separable especially when
comparing children with differences in experience – fluid intelligences similar, while crystallized
intelligence differs a lot.
• Other Carroll’s categories include: Memory (memory span, associative memory), visual perception
(visualization, spatial relations), auditory perception (speech sound discrimination), retrieval ability
(creativity), cognitive speediness, and processing speed (reaction time)
Gardner’s Theory of Multiple Intelligences
• Howard Gardner: Using not just test scores, Gardner looked at research in child development,
neuropsychology of brain-damaged individuals, and studies of gifted people to identify nine distinct
intelligences, the first 3 of which are in psychometric theories. These are considered to be biologically-
• However, studies were conducted in adults, while popular in education there is little good research in
• 1) Linguistic: Knowing word meanings, ability to use words to understand ideas and convey ideas to
• 2) Logical-Mathematical: Understanding relations between objects, logical and mathematical
• 3) Spatial: Perceiving objects accurately in the “mind’s eye”, including before and after transformations
• 4) Musical: Comprehending and producing sounds varying in pitch, rhythm, and emotional tone
• 5) Bodily-Kinesthetic: Using one’s body in highly differentiated ways, e.g. dancers and athletes
• 6) Interpersonal: Identifying feelings, moods, motivations and intentions in others
• 7) Intrapersonal: Understanding one’s emotions, strengths, weaknesses, etc.
• 8) Naturalistic: Recognizing and distinguishing among members of a group (species) and describing
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• 9) Existential: Considering ultimate issues such as purpose of life and nature of death
• Each of these intelligences has a unique developmental history, e.g. linguistic intelligence develops
much earlier than the other eight.
• Each intelligence is regulated by distinct regions of the brain, shown from studies of brain-damaged
persons, e.g. spatial intelligence is regulated by particular regions of brain-damaged persons.
• Each intelligence has special cases of talented individuals. Savants are individuals with mental
retardation who are extremely talented in one domain, often musical intelligence.
• Emotional intelligence, the ability to use one’s own and others’ emotions effectively for problem
solving and living happily, is another non-traditional type of intelligence. EI includes perceiving emotions
accurately, and regulating one’s emotions. People with high EI tend to have higher self-esteem and are
Implications for Education
• Schools should foster all intelligences, rather than just traditional linguistic and logical-mathematical
intelligences, and teachers should capitalize on the strongest intelligences of individual children
• Engage as many intelligences as possible when teaching a topic, this allows a much richer
understanding of the topic by all students
Sternberg’s Theory of Successful Intelligence
• Sternberg defines successful intelligence as using one’s abilities skillfully to achieve one’s personal
goals, which can be both short-term and long-term. These include 3 kinds of abilities.
• Analytic ability involves analyzing problems and generating different solutions, information-processing
– this is what IQ tests consider, academic skills
• Creative ability involves dealing adaptively with novel situations and problems, ability to invent,
discover, suppose or theorize (experimental)
• Practical ability involves knowing what solution or plan will actually work, succeeding in spite of
hardships and adapting to the environment
• If this is the case, scores from tests that measure these distinct abilities should be unrelated to each
other. On the other hand, if these abilities are in fact all the same or stem from the same origin, such as
general intelligence g, then correlation between test scores should be 1.
• In reality, correlation was midway – they are related, but not perfectly.
• Successful intelligence is revealed in pursuit of goals, but goals differ between individuals and cultures.
Binet & Development of Intelligence Testing
• Intelligence tests were originally devised to address a changed school population in the early 20th
century, to identify children who would most benefit from schooling and those who would have difficulties.
• Alfred Binet and Theophile Simon selected simple tasks such as naming colours, counting
backwards, and remembering numbers and identified difficulties appropriate to each age. This was the
concept of mental age (MA), the difficulty of problems that children could solve correctly.
• Mental age was used to distinguish “bright” from “dull” children – a bright child would have MA higher
than their actual age, a dull child lower MA.
• Binet himself believed that children who were behind were just slow, not retarded, and was worried
about this test excluding them from the education system – original tests did not include aspect of time
• Lewis Terman revised this test to be standardized to the Stanford-Binet.
• Intelligence quotient (IQ) is the ratio of mental age to chronological age: IQ = MA/CA * 100. This can
thus be used to compare children of different ages – not applicable to adults. Page 266-293, 27 pages Page 3 of8
o At any age, children who are perfectly average will have
an IQ of 100, mental age equals chronological age. IQ
distribution follows a standard curve, with 67% scoring
85 – 115, and 95% 70 – 130
o A standard deviation is 15 IQ points. Can also be
thought of using percentile rank, the % of same-age
children a child is performing better than (at IQ 100, 50th
o However, did not give sufficient information about lag in
development – a 4 year old who has MA of 3 and an 8
year old with MA of 6 would have same IQ, but face
• Today, IQ scores are computed by comparing test performance to others of the same age, average
• The Stanford-Binet is still administered today, consists of various cognitive and motor tasks ranging in
difficulty. It can be used for individuals 2 years old to adulthood, but test items change depending on age.
• The Wechsler Intelligence Scale for Children (WISC-III) is also used, which includes practical
performance skills in addition to verbal skills. This
includes picture completion tasks (what part is
missing?) and arranging pictures to tell a coherent
• Intelligence tests often able to identify areas of
intellectual disabilities well; children with autism
perform better on non-verbal than verbal sections of
• Examples of items in the Stanford-Binet & WISC:
o Verbal: Basic information (what is the capital
of France?), vocabulary (define poet), arithmetic,
comprehension (why are we tried by a jury of our
peers – often very sociocultural dependent),
similarities (in what way are inch and mile alike?)
o Performance: Short-term memory (recall a
series of digits backwards), picture completion,
block design, object assembly, picture
arrangement (tell a story)
• The Stanford-Binet and WISC-III cannot be used to test intelligence in infants. Rather, the Bayley
Scales of Infant Development is used for children 1 to 42 months, covering cognitive, language, motor,
social-emotional, and adaptive behaviour.
Do Tests Work?
• A test is reliable if it yields scores which are consistent, such as test-retest and interrater reliability.
• In general, scores from infancy are not related to IQ scores obtained later in childhood, adolescence, or
adulthood. Children must be at least 18-24 months old for Bayley scores to be predictive.
• Why? Infant tests measure different abilities than tests for older children – more emphasis on
sensorimotor skills, less on cognitive processes. But Bayley scales still used to diagnose developmental
pace. Page 266-293, 27 pages Page 4 of8
• Habituation is actually a better measure of information processing, more predictive of IQ – correlation
of about 0.5. E.g. 6 month olds who habituate to visual stimuli more rapidly tend to have higher IQs later.
• Correlations of IQ obtained during childhood to in adulthood steadily increase with age – intelligence is
one of the most stable traits from early childhood on. However, on an individual level, this is not always
• Increasing IQ scores typically arise when parents deliberately trained the child’s intellectual and motor
• Validity refers to the extent that a test really measures what it claims to measure. This is usually
determined by concurrent validity: scores on a test correlate positively with scores on another, similar
test said to measure the same construct. For example, to measure validity of a test of extroversion, look
at children in a social setting and see if tests correlated with those observations.
• For intelligence, most correlate IQ scores with measures of school performance – this is around 0.4 to
0.6, a positive correlation but far from perfect
• Higher IQ is also correlated with academic and career success, particularly crystallized intelligence;
however, success also affected by motivation, health, creativity, social skills, and socioeconomic status.
Education is even more predictive of later success, and is a gatekeeper of IQ.
Increasing Validity with Dynamic Testing
• Most IQ tests measure knowledge and skills accumulated up to point of testing, not potential for
future learning: unsaid assumption that child who has learned more in past will learn more in the future
• Dynamic testing measures a child’s learning potential by having a child learn something completely
new in the presence of the examiner, with interactive examiner’s help. Then looks at performance on
transfer activity, of this skill or knowledge generalized to a new problem.
• This is based on Vygotsky’s ideas of zone of proximal development and scaffolding. Learning potential
estimated by how much child learns during interaction, and from amount of help needed.
• Found Ethiopian immigrant children and Israeli children’s scores were nearly equal postteaching and
transfer, whereas there was large deficiency in Ethiopian children preteaching.
Hereditary & Environmental Factors
• Genes influence intelligence: identical twins have more similar IQ test scores (correlation around 0.8),
while fraternal twins’ IQ scores would be less similar (0.6) – but more similar than scores of children and
adopted siblings (0.3). Overall, heritability quotient of 0.5 – keep in mind problems with adoption
• Heredity also influences developmental profiles for IQ scores – if one identical twin gets higher IQ
scores with age, the other twin almost certainly will, too.
• Throughout childhood and adolescence, correlation between adopted children’s IQ and their biological
parents’ IQ is greater than correlation to adoptive parents’ IQ. This correlation increases with age.
o Active effect: family environment has great influence early in life, but effect diminishes over time.
• Environment is also important. Many characteristics of parents’ behaviour and home environments are
related to intelligence, such as amount of play materials (enrichment), and differences for each child in
• Flynn Effect: IQ test scores have risen dramatically over the last century, which cannot be accounted