Limitations of Twin Studies
• Limited to “ACE” model• No test of assumptions of twin design• C biased by assortative mating, passive rGE,
stratification• C and D tend to cancel• Cannot separate components of C: vertical cultural
inheritance, extra-familial shared environment, special C in twins, parent-child interaction
• Twin pairs are same age
Extensions: Design
• Twins and Parents (TAP)• Longitudinal Twins and Parents (LTAP)• Children of Twins (COT)• Spouses of Twins (SPOT)• Siblings of Twins • The Full Monty: Extended Twin Kinship Design
E.T. (AKA “Stealth”, “Cascade”).
Extensions: Assessment
• MEASURE THE ENVIRONMENT• MEASURE THE GENOTYPE• MEASURE THE ENDOPHENOTYPE AND
EPIGENOME• DYADIC ASSESSMENT (interactions of relative
pairs).
Parents of Twins
• Anticipate “adult outcome” of child phenotype (quick and dirty developmental study)
• Provide environment for offspring (parent-child interaction)
• Spousal resemblance• Clue to non-additive genetic effects
Siblings of Twins
• “Are twins special? Funny? Different?”• Sibling interaction effects, confluence, density,
family size (also non-twin singletons)• Age-moderation of family resemblance (are
different genes/environments expressed at different ages – GxAge interaction).
Children of Twins
• Resolve effects of maternal and offspring genotype on offspring behavior
• Resolve genetic and non-genetic components of parent-child resemblance
The mediating effect of parental neglect on adolescent and young
adult anti-sociality: A longitudinal study of twins
and their parents (LTAP).
Lindon Eaves, Liz Prom, Judy Silberg
So: Does neglect cause childhood antisocial
behavior (“environmentally”)?
OR
Is it a result of the fact that neglect is an expression of (genetic?) anti-social behavior in
the parents?
OR BOTH.
Polychoric correlations between anti-social behavior of (adult) parents and adult and juvenile anti-social behavior of their offspring.
Genetic effects of assortment andPassive rGE
Significant assortment doesn’t do much genetically (here)Not much passive rGE even though parental ASP geneticand affects child’s environment
Children of Twins (COT)
Unraveling the effect of genes and environment in the transmission of parental
antisocial behavior to children’s conduct disturbance, depression, and hyperactivity.
Judy Silberg, Hermine Maes, Lindon Eaves
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