Transcript Intelligence - University of Toronto

Intelligence
Josée L. Jarry, Ph.D., C.Psych.
Introduction to Psychology
Department of Psychology
University of Toronto
July 14, 2003
Intelligence Testing
• has existed for nearly 100 years
• what do the tests really measure?
• are they valid predictors of scholastic
ability?
• do individual differences in scores
arise from genetic differences?
• or from differences in opportunity and
experience?
Defining Intelligence
• Psychologists and educators define
intelligence as the capacity for:
– abstract reasoning, problem solving, and
the capacity to acquire new knowledge
– memory, adaptation to one's
environment, mental speed, linguistic
competence, mathematical competence,
general knowledge, and creativity
– sensory acuity, goal directedness, and
achievement motivation.
Mental Quickness & Acuity
• Sir Francis Galton (1822-1911)
• Hereditary Genius (1869)
– the capacity for high intellectual
achievement is inherited
– intelligence is the speed and accuracy
with which one can detect and respond to
environmental stimuli
– invented the correlation coefficient.
Intelligence: a Collection of Abilities
• Alfred Binet (1857-1911)
– Binet-Simon Intelligence Scale (1905)
– intelligence is a collection of various higher
order mental abilities only loosely related to
one another
– intelligence is nurtured through interaction
with the environment
– the goal of schooling is to increase intelligence
– introduced “Mental age” in 1908.
Intelligence & Factor Analysis
• Charles Spearman (1863-1945)
– developed a new battery of mental tests
and factor analysis
– found two separate factors
– G for general intelligence
– S for specific ability
– a person's score on any given test
depends on the combination of G & S
– assumed that general intelligence
represents biologically endowed ability.
Fluid & Crystallized Intelligence
• Raymond Cattell (1905-)
• Fluid intelligence
– the ability to perceive relationships
independently of previous practice or
instructions
– peaks at age 22 to 25 and then declines
gradually
• Crystallized intelligence
– a mental ability derived directly from
previous experience
– continues to increase until about age 50.
Testing Fluid & Crystallized
Intelligence
• Fluid Intelligence
– Soon is to Never as Near is to: a) not far,
b) seldom, c) nowhere, d) widely?
• Crystallized Intelligence
– Runner is to Marathon as Oarsman is to
a) boat, b) regatta, c) fleet,d)
tournament?
Introduction of IQ
• Lewis Terman
– adapted the Binet-Simon test to NorthAmerican standards in 1916
– "Stanford-Binet" after Stanford University
– adapted the scoring modification developed
by Stern (1912) who introduced the notion
of IQ
– IQ = MA/CA X 100
– as chronological age increases, IQ has to
decrease.
Adult Intelligence Testing
• David Wechsler
– developed an intelligence tests for adults
inspired by the Binet-Simon
– made the notion of mental age obsolete
by using the average score for a norm
group and establishing norms for
different ages
– the average IQ is 100
– performance above or below average
results in an IQ above or below 100
– results in a normal distribution of IQs.
The Validity of IQ Tests
• If intelligence tests measure intellectual
ability, then IQ scores should correlate
with other indices of intellectual ability
• The correlation between IQ and school
grades ranges from .30 to .70
• The correlation between IQ and
performance in job requiring high
intellectual ability ranges between .20
and .40
IQ: Nature or Nurture
• Nature
– refers to the person’s biological inheritance
• Nurture
– refers to the entire set of environmental
conditions to which the person is exposed
• Are psychological differences among people
primarily the result of differences in their
genes (nature) or in their environment
(nurture)?
IQ Heritability
• Twins studies
– Identical twins are genetically identical
– Fraternal twins are like non-twin siblings and are only
50 % related to one another
– The correlation between IQs of identical twins is
considerably greater than for fraternal twins
– This indicates that genes play an important role in IQ
– The correlation between fraternal twins’ IQs in
adulthood drops, but that of identical twins does not.
Identical Twins Raised Apart
– identical twins share 100% of their genes, but their
environments is no more similar to each other than
are the environments of any two members of the
study population taken randomly
– the average correlation coefficients between the IQ
of identical twins raised apart is .73
– fluid and crystallized intelligence are equally
heritable
– fluid intelligence influences the acquisition and
recall of facts.
Influence of The Family on IQ
• pairs of adoptive sibling who are genetically
unrelated but are raised together are studied
• correlation greater than “0” between IQs must be
due to shared environments
• when unrelated siblings are still children, their IQs
correlate positively: .25
• the correlation is completely lost in adulthood
• the correlation between IQs of genetically unrelated
adults who have been raised in the same family is .01
IQ, Race & Culture
• Blacks in the US score on average 15 points
lower than whites on standard IQ tests
• Heritability studies explore IQ differences
within groups, not between groups
• Differences within one group tell us nothing
of the differences between groups.
Racial Differences Explained
• if whites are genetically superior to blacks in IQ,
mixed race individuals should have intermediate IQs
• one study identified a sample of black children in
Chicago who had IQs in the superior range (125 or
better)
• the proportion of European ancestry in the high IQ
black children was neither more nor less than that in
the black population at-large
• modern biochemical methods show no relationship
between ancestry and IQ.
Social Designation and IQ (1)
• Autonomous minorities
– are groups who have deliberately separated
themselves from the mainstream and are proud
of their heritage
• Immigrants minorities
– are groups who integrate in hopes of bettering
themselves
– are relatively detached of the majority’s
appraisal of them.
Social Designation and IQ (2)
• Involuntary minorities or castelike
minorities
– are groups who did not choose their minority
status
– are routinely judged as inferior by the dominant
majority
– castelike minorities everywhere perform more
poorly in school and score on average 10 to 15
points lower on IQ tests than the dominant
majority.
Varieties of Intelligence
• Left vs. right hemisphere intelligence
– left hemisphere lesions in the language area can
completely abolish a person's ability to speak or to
think in words without affecting the ability to read
maps or to solve spatial puzzles
– A right hemisphere lesion in a specific location can
have just the opposite effect
– lesions in the left hemisphere tend to depress
people's scores on tests that measure verbal
knowledge and verbal reasoning while leaving
performance on other tests intact.
Extreme Intellectual Specialists
• Retarded savants
– severely impaired in most intellectual realms
– but develop superior ability in one intellectual realm
such as music, arts, or mental arithmetic
– savants use rules, not just memory
• Confirms that ultimately, intelligence is a
collection of relatively unrelated abilities
• These abilities appear related in normal
individuals.