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y1 personality and individual differences > Genetic and environmental basis of intelligence > Flashcards

Genetic and environmental basis of intelligence Flashcards

1
Q

What are inherited characteristics? (examples)

A

Controlled by biological structures (genes) passed to us by biological parents
eg:
- blood type
- hair colour
- eye colour
- intelligence(?)

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2
Q

What is a genotype?

A

genetic component, coded in DNA inherited from parents

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3
Q

What is a phenotype?

A

outward manifestations of the individual

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4
Q

What is heritability? (ref to phenotypes)

A

The proportion of phenotypic variance due to genetic differences.
100% = differences in intelligence is entirely inherited
0% = differences in intelligence not related to heritability

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5
Q

How can family environment be a significant environmental influence?

A

Children raised in the same home will be more similar. However, even children raised in the same home will have different experiences growing up

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6
Q

What are some examples of environmental influences?

A
  • Socioeconomic status
  • prenatal health
  • birth order
  • family size
  • culture
  • education
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7
Q

What did Galton (1865) study?

A

the relationship between eminence and families
boys adopted by eminent men and raised in privilege were less likely to be eminent than natural-born privileged sons of eminent men - genetic link?

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8
Q

What did Galton conclude?

A

Intelligence is genetically determined and fixed at birth

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9
Q

What is an example of early animal research into intelligence?

A

Tolman (1924) and Tyron (1940) selectively bred two strains of rats
- “maze bright” - quickly run around maze and find food
- “maze dull” - much slower at learning to find food in maze

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10
Q

What are the 3 main methods for investigating the influence of genetics/environment on intelligence in humans?

A
  • twin studies
  • adoption studies
  • family studies
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11
Q

How are family studies used in the context of intelligence?

A

Investigate the similarity of family members in respect of intelligence

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12
Q

What is the genetic similarity of first-degree relatives? (parents, siblings, children)

A

50% genetic similarity

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13
Q

What is the genetic similarity of second-degree relatives? (grandparents, grandchildren, aunts, uncles, nephews, nieces)

A

25% genetic similarity

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14
Q

What is the genetic similarity of third-degree relatives? (great-grandparents, great-aunds/uncles, 1st cousins)

A

12.5% genetic similarity

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15
Q

What is the hierarchy of similarity?

A
  1. siblings
  2. aunt-niece
  3. cousins
  4. stepmother-stepchild
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16
Q

What are monozygotic twins?

A

identical twins
identical genotype
100% genetic similarity

17
Q

What are dizygotic twins?

A

Fraternal twins
Genetically no more alike than other siblings
50% genetic similarity

18
Q

What is the assumption of twin studies?

A

Environments are matched but MZ more genetically similar than DZ
- if environment is most important, MZ and DZ will be equally similar
- if genetics are most important, MZ will be more similar than DZ

19
Q

What are the correlation coefficients for MZ and DZ twins (Eysenck, 1994)? What does this tell us about heritability of intelligence?

A

MZ = 0.87
DZ = 0.53
Genetics are important but not the only factor of intelligence

20
Q

What is the issue with environment for MZ and DZ twins that makes it hard to make conclusions about the influence of genetics?

A

MZ twins are often treated in a more similar way than DZ twins (dressed the same, play more together, spend more time together) so their environments are more similar than DZ - cannot conclude that genetics are the main influence

21
Q

How could the influence of genetics be investigated more accurately?

A

Control genes - manipulate environment of MZ twins (adoption studies)

22
Q

Who was Cyril Burt, what was he interested in and how did investigate it?

A
  • British educational psychologist
  • Interested in heretidy of intelligence - attributed difference in intelligence to genetics
  • Investigated via study of MZ twins reared apart
23
Q

Why did Burt’s work cause controversy?

A
  • Claimed he had fabricated his data and research assistants
  • raw data could not be found
24
Q

What is a criticism of Burt’s work related to correlations?

A

Too much similarity in his correlations
1943 - 15 sets r=.770
1955 - 21 sets r=.771
1966 - 53 sets r=.771
would expect to see greater variance in correlations as additional twin sets were added.
AND - was it possible to find that many MZ twins reared apart? no other study managed to identify as many

25
Q

What are some recent research supporting Burt’s conclusions?

A

Bouchard and McGue (1981) MZ twins reared apart r=.72
Ridley (1999) MZ twins reared apart r=.76

26
Q

What was the Minnesota study?

A

100 sets of DZ and MZ twins/triplets separated early on in life, reared apart and then reunited as adults

General intelligence strongly influenced by genetics = MZ twins r=.70

27
Q

What are some limitations fo separated twin studies?

A
  • Some MZ twins actually found to be living in different branches of same family
  • ppts difficult to recruit
  • selective placement (adoption agencies try to place children in an environment that matches as closely as possible to birth environment)
  • what about prenatal environment? - Majority of twin studies focused on middle class samples
  • are twins representative of general population?
28
Q

How could researchers control the environment and manipulate genes?

A

same age unrelated siblings - virtual twins
- no genetic link but reared in same environment
- 21 pairs of virtual twins tested, reared together in same home before age of 1 yr
- mean correlation between children .17 - lower than MZ and DZ twins and siblings who all share proportion of genetic similarity

29
Q

What was the Fullerton Virtual twin study?

A
  • adopted by 1yr old
  • sibling age difference 9mo or less
  • same grade at school
  • absence of any birth events that may affect development
  • current age of 4+yrs
  • same and mixed sex pairs
    Completed subscales from WISC-III
    Correlations .30 at time one and .11 at time 2 - modest relationship to no relationship
    Importance of shared genes over shared environment increases over time.
30
Q

What was the Texas adoption study?

A

300 families who had adopted children from a home for unwed mothers
Initially, correlations between adopted parents and children similar to correlations with biological children
- environment influences intelligence when children are small but as they develop, the influence of environment decreases and genetics increases

y1 personality and individual differences (11 decks)

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