Genetics%20vs.%20Environment

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 are crucial for any
  trait
• Environmental factors determines which genes get
  switched on.
• Example nutrition affecting you reaching your
  genetic potential in height.

3
Heredity and Environment

• Heritability

• Environment

• The variation within a group caused by genetic
  factors
• Thought to be about 50

• 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

5
Twin Studies Family Influence Thomas Bouchard
the Minnesota Twins studies

• 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

6
Twin Studies
7
Data Analysis-Genetic Factors

• 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.

8
Data Analysis-Environmental Factors

• 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.

9
Both genetics and environment have an effect on
IQ scores
10
Adoption Studies
Children's verbal ability scores became modestly
more like their biological parents' scores.
(Adapted from Plomin DeFries, 1998.)
11
Group Differences in Intelligence Test Scores
12
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.

13
Socioeconomic Differences

• A childs ability is influenced by genetic
  factors and perhaps by the effects of the
  parents occupation and education on the home
  environment.
• Also, higher-income families may encourage a
  higher level of motivation to succeed.

14
Ethnic Differences

• There is variation in average IQ scores between
  ethnic groups, but MORE variation within groups.
• Research indicates that differences in IQ among
  ethnic groups may be due to differences in
  socioeconomic environment, parental education,
  nutrition, health care, and schools.

15
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

16
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

17
Racial Difference in IQ

• Stereotype Threat When members of a particular
  group fear they are being thought of or evaluated
  according to a negative stereotype,
• fear that they may confirm the stereotype leading
  to self-doubt and anxiety resulting in poor
  performance.

18
Stereotype ThreatRace
19
Stereotype ThreatGender
20
Effects of Discrimination on Intelligence

• The 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.

21
Seed Analogy Argument for Environment
22
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)
• What can be concluded?
• Unless the environments of two racial groups are
  totally identical, it is impossible to estimate
  the overall genetic differences between the two
  groups.

23
Are IQ Tests Culturally Biased?

• Test will favor the people from the culture in
  which it was developed.
• Ex If IQ test reflects white, middle-class
  cultural knowledge and values it could result in
  poor scores by minorities.

24
Are IQ Tests Culturally Biased?

• 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

25
Conditions that Can Raise IQ Scores
26
Conditions That Can Raise IQ Scores

• Enrichment programs such as Head Start can cause
  at least temporary gains in IQ scores.
• Spending time in projects such as Head Start may
  cause a child to be more motivated and have a
  better attitude toward school.