Methods in Behavior Genetics

Question 1

what is selective dog breeding?

Answer 1

For centuries, dogs have been bred for behaviors and temperament as well as physical characteristics

Question 2

what was the russian fox experiment (1959)?

Answer 2

the best known experimental study in animal domestication
* Tamest foxes were bred for about 40 generations and are now a popular house pet in Russia
* Foxes are notoriously wary of humans Dmitriy Belyaev and some of his tame foxes

Question 3

what were the laboratory breeding experiments?

Answer 3

open field mice
- High active bred with high active
- Low active bred with low active
(Over many generations see increasingly more and less active mice lines)

Question 4

what were the inbred strain studies?

Answer 4

Start with different strains, and then mate brothers & sisters for several generations
* By about the 6th generation within strains individuals are nearly genetically identical
* Between strains, individuals differ genetically from one another

Question 5

what are select/rearing environment studies?

Answer 5

Select for a behavior and and then expose individuals of the same strain to different environments

Question 6

what happened during the select/rearing studies?

Answer 6

Maze-bright vs maze-dull mice reared in impoverished vs enriched environments compared on their ability to learn a maze

Question 7

results of select/rearing studies?

Answer 7

• See small difference between groups reared in an enriched environment
• But large difference between groups when reared in an impoverished environment

Question 8

results of inbred strain studies?

Answer 8

• We see differences on open-field activity between inbred strains reared in same laboratory environment
• This reflects genetic influence because environment is controlled

Question 9

what happens during transgenic animal studies?

Answer 9

we are altering the animals genome

Question 10

“knock in” transgenic animal study?

Answer 10

Adding gene segment that might enhance certain behaviors
(EX: Insert a gene that makes mice completely fearless)

Question 11

knock out transgenic animal study?

Answer 11

Deleting a gene segment to assess for phenotypic change
(EX: deleting a gene that contributes to male sexual behavior in mice makes them interested in males rather than females)

Question 12

in human studies we must rely on?

Answer 12

Must rely on naturally occurring events, like adoption and twinning

Question 13

adoption studies?

Answer 13

Adoption/twinning provide the basis for all human heritability studies
- Also produces family members who share family environment but are not genetically related
* Adoption creates pairs of genetically related individuals who do not share family environment

Question 14

adoption studies show for most psychological traits that?

Answer 14

that genetic and environmental influence is apparent
- ex: genetic relatives (r = .24 (parent-child, siblings)
- ex; environmental relatives (r = .20, .32)

Question 15

what are the two sources of environmental influence?

Answer 15

1. Shared environment: environmental factors or experiences that we share with our siblings
2. Non-shared environment: the things we experience that our siblings do not

Question 16

what are some potential problems w/ adoption studies?

Answer 16

Fewer children adopted today = more difficult to conduct, smaller sample size

Question 17

what is selective placement of adopted children?

Answer 17

• Occurs when agencies try to place adoptees with adoptive parents who resemble genetic parents (e.g., same race/ethnicity, education)
• If information is available on genetic parents, researchers can statistically control for selective placement effects (e.g., education level)

Question 18

what is twin design? (monozygotic: MZ)

Answer 18

monozygotic twins can have different uterine environments

Question 19

what is a monozygotic twin?

Answer 19

identical twins result from a single fertilized ovum and therefore share all genes

Question 20

what is a dizygotic twin?

Answer 20

two eggs fertilized by two sperm - no more alike genetically than any other sibling pair

Question 21

equal environments assumption?

Answer 21

Environment does not make identical twins more similar to each than environment makes fraternal twins similar to each other

Question 22

evidence of equal environments?

Answer 22

1. Misclassified twins (when parents think their twins are DZ but are really MZ, or the reverse)
2. MZ twins are intentionally treated more individually
3. MZ reared apart are more similar than fraternal twins reared apart—most compelling evidence

Question 23

combination of twin and adoption studies?

Answer 23

‣ U of Minnesota Twin Family Study (MTFS)
‣ Swedish Twin Registry Sibling Interaction and Behavior Study (SIBS)

Question 24

family of MZ twin studies?

Answer 24

• With IQ, cousins are nearly as similar to one another as are half-siblings
• Nephews and uncles are nearly as similar as fathers and sons

Question 25

what is the genetic effect size?

Answer 25

How much genetics contributes to a trait

Question 26

Genetic effect size applies to individual differences for a trait in the entire _____?

Answer 26

population

Question 27

what is heritability?

Answer 27

The statistic that estimates the genetic effect size

Question 28

heritability = _____?

Answer 28

the amount of variation in a trait that can be accounted for by genetic variation among individuals.

Question 29

heritability needs to be?

Answer 29

• Must be a phenotype & genotype that varies
• If no variation in genotype/phenotype, then no heritability
• Computed using correlations among individuals who vary by kinship and rearing conditions
• Ranges from 0.0 (genes do not contribute at all) to 1.0 (genes are the only reason for individual differences)

Question 30

Environmentability = ______?

Answer 30

1.0 - heritability (or the proportion of
phenotypic variance attributable to environmental variance)

Question 31

heritability describes the ____?

Answer 31

contribution of genetic differences
to phenotypes among individuals in a particular population at a particular time (can change based on allele frequencies)