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Genetics vs. Environment

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Genetics vs. Environment Their Role in Intelligence Nature vs. Nurture in IQ Is a person s intelligence due more to genes or to environment? – PowerPoint PPT presentation

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Title: Genetics vs. Environment


1
Genetics vs. Environment
  • Their Role in Intelligence

2
Nature vs. Nurture in IQ
  • Is a persons intelligence due more to genes or
    to environment?
  • Both genes intelligence crucial for any trait
  • Environmental factors determines which genes get
    switched on.
  • Example of nutrition effecting you reaching your
    genetic potential in height.

3
Heredity and Environment
  • Heritability
  • The variation within a group caused by genetic
    factors
  • Thought to be about 50
  • Environment
  • Degree to which variation is due to environmental
    rather than genetic differences
  • Environmental Factors can be early intervention,
    schooling and family life

4
Twin Studies Family Influence Thomas Bouchard
the Minnesota Twins studies
  • If trait genetic
  • closely related more similar than less closely
    related
  • Many close relatives share environments too
  • Types of studies to separate effects
  • monozygotic twins reared together
  • monozygotic twins reared apart
  • siblings/dizygotic reared together
  • siblings/dizygotic reared apart
  • adoptive siblings reared together

5
Twin Studies
6
Data Analysis
  • The data show that both genetics and environment
    have an effect on IQ scores.
  • The more closely two individuals are related
    genetically, the more similar their IQ scores
  • Identical twins reared together are more alike
    than are fraternal twins reared together.
  • Also show the importance of environmental
    influences
  • Identical twins reared together are more alike
    than are identical twins reared apart
  • siblings who are reared together are more alike
    than are siblings reared in different homes.

7
Both genetics and environment have an effect on
IQ scores
8
Adoption Studies
Children's verbal ability scores became modestly
more like their biological parents' scores.
(Adapted from Plomin DeFries, 1998.)
9
Group Differences in Intelligence Test Scores
10
Group Differences in Testing
  • A number of studies show scoring differences
    between different racial, ethnic, and gender
    groups.
  • Are these differences due to nature or to
    nurture?
  • Studies suggest environment is playing a heavy
    role.
  • Heredity and environment interact to produce
    intelligence in individuals.

11
Why do Japanese and Chinese students perform
better than Americans on intelligence and
achievement tests?
  • They score the same before school but once school
    starts they begin to show more gains. This due
    to
  • Spending more time in school
  • More time doing homework
  • Pressure and support from parents to achieve
    academically

12
Group DifferencesAustralian aborigine white
scores on IQ tests
  • Play Intelligence and Culture (402) Module 4
    from The Brain Teaching Modules (2nd edition).
  • Are the differences in scores the result of
    environment or genes?
  • Which theory of intelligence does this example
    prove? Gardners Multiple Intelligences or
    Spearmans g factor?

13
Racial Difference in IQ
  • Racial difference in average IQ among different
    racial groups can be measured
  • More variation in IQ scores within a particular
    group than between groups
  • Stereotype Threat When members of a particular
    group fear they are being thought of or evaluated
    according to a negative stereotype, they fear
    that they may confirm the stereotype leading to
    self-doubt and anxiety resulting in poor
    performance. (see Box 7.4 on pg. 311)

14
Effects of Discrimination on Intelligence
  • Burakumin people of Japan are severely
    discriminated against.
  • Despite being genetically similar to Japanese
    people
  • Their IQ scores are 10 to 15 points lower than
    normal Japanese people.

15
Seed Analogy Argument for Environment
16
Within and Between Group Differences
  • Each corn field planted from same package of
    genetically diverse seeds
  • One field is quite fertile, the other is not
  • Within each field, differences due to genetics
  • Between each field, differences due to
    environment (fertility)
  • Unless the environments of two racial groups are
    totally identical, it is impossible to estimate
    the overall genetic differences between the two
    groups.

17
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18
Are IQ Tests Culturally Biased?
  • If IQ test reflects white, middle-class cultural
    knowledge and values it could result in poor
    scores by minorities.
  • Test will favor the people from the culture in
    which it was developed.
  • Factors like test-taking behavior, motivation,
    attitudes towards the test and previous
    experiences with tests can affect performance.
  • Try some culturally biased tests yourself
  • Robert Williams IQ Test the Dove Counterbalance
    Test
  • Chitling Intelligence Test
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