UNIT 10: INTELLIGENCE
Heritability
• Heritability: the proportion
of variation among
individuals that we can attribute to genes (Unit 4)
– Never pertains to an individual – only to why people differ from one another
– For intelligence it is about
50%
Heritability
• “In a world of clones,
heritability would be zero.”
• “Heritability of boys raised
in barrels would be 100%.” – Mark Twain
UNIT 10: INTELLIGENCE
Heritability
• Environment enhances
performance:
– If you have a natural aptitude
for academics, you will be more likely to stay in school, read books, and ask questions – all of which will amplify
your cognitive brain power.
Environmental Influences
• Severe deprivation does
leave footprints on the brain
– Romanian and Iranian
orphanages observe children who cannot sit up unassisted at age 2 or walk at age 4
– Extreme deprivation was
bludgeoning native intelligence
UNIT 10: INTELLIGENCE
Environmental Influences
– Language-fostering games
significantly helped orphans
– Among the poor,
environmental conditions can override genetic differences, depressing cognitive development • Less-qualified teachers • Malnutrition • Sensory Deprivation • Social Isolation Environmental Influences
• Can parents “fast-forward”
a normal infant into genius?
– All babies should have normal
exposure to sights, sounds, and speech
– Evidence shows there is little to be gained by extreme
efforts to enhance early intelligence
– See “Mozart effect” and “music-training effect”
UNIT 10: INTELLIGENCE
Schooling and Intelligence
• Schooling and intelligence
both enhance later income
• Project Head Start (1965)
– U.S. Government-funded
preschool program
– Mostly for families below poverty level
Schooling and Intelligence
• Quality programs help:
– Offer individual attention – Increase children’s school
readiness
– Decreases likelihood of
repeating a grade
– Decreases likelihood of being placed in special education programs
UNIT 10: INTELLIGENCE
Schooling and Intelligence
• What we accomplish also
depends on our beliefs and motivation:
– Those with a “growth
mindset” see intelligence as something that can be
modified, and are usually more successful
– Those with a “fixed mindset”
tend to be less successful
Group Differences in Intelligence Scores
• Our gender similarities far
outnumber our gender differences
– In terms of intelligence, the
UNIT 10: INTELLIGENCE
Gender Comparisons
• Females are somewhat
better than males at:
– Spelling
– Verbal fluency and remembering words
– Remembering and locating
objects
– Sensations of touch, taste, and odor
– Emotion detecting
Gender Comparisons
• Males and females are
nearly the same at:
– Math and spatial aptitudes • males are slightly better at
math problem solving
• females are slightly better at math computation
• In western cultures, more
males than females are involved with math on regular basis (Why?)
UNIT 10: INTELLIGENCE
Gender Comparisons
• Males are more likely than
females to overestimate their own test scores
• Both males and females
rate scores of their:
– Father higher than mother
– Brother higher than sister
– Son higher than daughter
Gender Comparisons
• Gender score differences are
sharpest at the extremes
– Among 12- to 14-year olds
scoring extremely high on SAT math, boys outnumber girls 13:1
– Boys have an edge in AP
physics and computer science exams
– 99% of chess grandmasters are
UNIT 10: INTELLIGENCE
Gender Comparisons
• Steven Pinker (2005) sees
both biological and social influences – Life priorities – Risk-taking – Math reasoning – Spatial abilities Gender Comparisons • Elizabeth Spelke (2005)
cautions that male/female comparisons are
oversimplified
– In gender-equal cultures of Iceland and Sweden, there is little gender gap in math
– Males are usually not tested
for their abilities in academic disciplines where they are underrepresented
UNIT 10: INTELLIGENCE
Gender Comparisons
• Greater Male Variability
– Males mental ability scores
vary more than females
– Boys outnumber girls at both the low and high extremes
– More boys than girls are
found in special education programs
– Boys talk later
– Boys stutter more
Ethnic Similarities/Differences
• Racial groups differ in their
average intelligence scores
• High-scoring people (and
groups) are more likely to attain high levels of
UNIT 10: INTELLIGENCE
Ethnic Similarities/Differences
• Bell curve of intelligence
scores is centered for:
– Whites (IQ 100)
– American Blacks (IQ 85)
– Hispanics (IQ roughly 93)
*There are many exceptions to these numbers. They only represent a generalization of statistics.
Ethnic Similarities/Differences
• Ethnic differences are
evident in many other groups around the world, not simply in the U.S.
• Individual differences within
a race are much greater
than differences between races
UNIT 10: INTELLIGENCE
Ethnic Similarities/Differences
• Asian students outperform
North American students on math achievement and
aptitude tests
– Asian students also spend 30% more days per year attending school, and more time out of school studying math
Ethnic Similarities/Differences
• White and Black:
– Infants have scored equally well
on an infant intelligence measure
– Exhibit similar information-
processing skill
• Various ethnic groups have
experienced “golden ages”:
– Greeks, Egyptians, Romans,
Arabs, Aztecs, Asians, etc.
– Difficult to attribute natural
UNIT 10: INTELLIGENCE
Ethnic Similarities/Differences
• Black and Whites:
– High school environments
differ greatly in quality, and therefore the gap grows wider here
– College environments of comparable quality see the gap narrow greatly
The Question of Bias
• Two meanings of bias:
– A test that measures
performance differences caused by cultural
experiences and education
– A test that predicts future behavior only for some groups of test-takers (Ex. males or females )
UNIT 10: INTELLIGENCE
The Question of Bias
• Near consensus among
psychologists is that major U.S. aptitude tests (ACT, SAT) are NOT biased.
Test-Taker’s Expectations
• Stereotype Threat – a self-
confirming concern that
one will be evaluated based on a negative stereotype
– Blacks scored higher when tested by Blacks rather than Whites
– Women have scored higher
when no male test-takers were in the group
UNIT 10: INTELLIGENCE
Test-Taker’s Expectations
– Women’s chess play drops
sharply when they think they are playing a male rather than a female
– Telling students they
probably won’t succeed at something serves to erode test and school performance
– Exercise in self-affirmation can serve to boost test and school performance
Test-Taker’s Expectations
• Are aptitude tests biased:
– Yes – in terms of sensitivity to
performance differences caused by cultural
experiences
– No – in the scientific sense of making valid statistical
predictions for different
UNIT 10: INTELLIGENCE
Test-Taker’s Expectations
• Are aptitude tests
discriminatory?
– Yes – their purpose IS to
discriminate – to distinguish among individuals
– No – they serve to reduce discrimination based on simply hiring the “right kind of person” or “who you
know”
Keep in Mind
• 1) Aptitude tests help
determine who might profit from intervention
• 2) Remain alert to not
misinterpret a test score as a literal meaning of personal worth or potential
• 3) The competence that general intelligence tests sample is
important – it helps enable success in some life paths.
UNIT 10: INTELLIGENCE
Keep in Mind
• 4) Intelligence tests don’t
account for abilities, talent, commitment, creativity, or character – all of which are important in determining who we are as individuals!