Methods in Behavior Genetics Flashcards
what is selective dog breeding?
For centuries, dogs have been bred for behaviors and temperament as well as physical characteristics
what was the russian fox experiment (1959)?
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
what were the laboratory breeding experiments?
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)
what were the inbred strain studies?
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
what are select/rearing environment studies?
Select for a behavior and and then expose individuals of the same strain to different environments
what happened during the select/rearing studies?
Maze-bright vs maze-dull mice reared in impoverished vs enriched environments compared on their ability to learn a maze
results of select/rearing studies?
- See small difference between groups reared in an enriched environment
- But large difference between groups when reared in an impoverished environment
results of inbred strain studies?
- We see differences on open-field activity between inbred strains reared in same laboratory environment
- This reflects genetic influence because environment is controlled
what happens during transgenic animal studies?
we are altering the animals genome
“knock in” transgenic animal study?
Adding gene segment that might enhance certain behaviors
(EX: Insert a gene that makes mice completely fearless)
knock out transgenic animal study?
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)
in human studies we must rely on?
Must rely on naturally occurring events, like adoption and twinning
adoption studies?
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
adoption studies show for most psychological traits that?
that genetic and environmental influence is apparent
- ex: genetic relatives (r = .24 (parent-child, siblings)
- ex; environmental relatives (r = .20, .32)
what are the two sources of environmental influence?
- Shared environment: environmental factors or experiences that we share with our siblings
- Non-shared environment: the things we experience that our siblings do not
what are some potential problems w/ adoption studies?
Fewer children adopted today = more difficult to conduct, smaller sample size
what is selective placement of adopted children?
- 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)
what is twin design? (monozygotic: MZ)
monozygotic twins can have different uterine environments
what is a monozygotic twin?
identical twins result from a single fertilized ovum and therefore share all genes
what is a dizygotic twin?
two eggs fertilized by two sperm - no more alike genetically than any other sibling pair
equal environments assumption?
Environment does not make identical twins more similar to each than environment makes fraternal twins similar to each other
evidence of equal environments?
- Misclassified twins (when parents think their twins are DZ but are really MZ, or the reverse)
- MZ twins are intentionally treated more individually
- MZ reared apart are more similar than fraternal twins reared apart—most compelling evidence
combination of twin and adoption studies?
‣ U of Minnesota Twin Family Study (MTFS)
‣ Swedish Twin Registry Sibling Interaction and Behavior Study (SIBS)
family of MZ twin studies?
- 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
what is the genetic effect size?
How much genetics contributes to a trait
Genetic effect size applies to individual differences for a trait in the entire _____?
population
what is heritability?
The statistic that estimates the genetic effect size
heritability = _____?
the amount of variation in a trait that can be accounted for by genetic variation among individuals.
heritability needs to be?
- 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)
Environmentability = ______?
1.0 - heritability (or the proportion of
phenotypic variance attributable to environmental variance)
heritability describes the ____?
contribution of genetic differences
to phenotypes among individuals in a particular population at a particular time (can change based on allele frequencies)
