Genetics and Personality Flashcards
what is behavior genetics?
Attempts to explain how personality traits that differ among individuals are passed from parent to child and shared by biological relatives
Examines how genes influence broad patterns of behavior Controversy lingers from eugenics and racism Controversies around biological determinis
What is a genotype?
an individual’s actual genetic structure (your DNA)
What is a phenotype?
The expression of a given genotype. Influenced by environment and experience (who you become)
What are three traits related to behavior genetics?
Alleles, Autosomal and Polygenic traits
What are polygenic traits?
polygenic traits and behaviors tend toward a normal distribution in the population, versus the either/or of autosomal traits
What are Family Incidence Studies?
ID a proband with a trait and review frequency of that (and/or other) trait within the same family.
Family Incidence studies have…
Higher incidence or shared ranges of a trait within a family (and decreasing incidence with genetic distance) suggests a genetic factor or relationship (sometimes a relationship between traits, e.g., different traits thought to be related, extraversion and openness)
Shared environment a confounding factor (Non-shared environment also a confounding factor)
Monozygotic (MZ) twins are
(aka identical twins) come from a single egg and sperm: 100% shared DNA (they are clones!)
Dizygotic (DZ) twins are
(aka fraternal twins) come from two different eggs and two different sperm: 50% (on average) shared DNA
What is a question asked in twin studies?
are MZs more similar than DZs for a particular disorder (and usually how much more or less similar)?
How are similarities measured in twin studies (Part one of two)
concordance rates if the trait is categorical (yes or no): if one twin has a trait, how often (what percent) does the other twin also have the same trait? (A concordance rate of 50% means half the time both twins have the trait.)
How are similarities measured in twin studies (Part two of two)
correlation coefficients when the trait is continuous or dimensional (more or less, as with personality measures). Correlate scores (on the NEO-PI for instance) between twins.
How do twins score in studies?
If MZs consistently higher, then a genetic component is presumed (assuming equal environmental effects). If a trait is completely genetically determined, then rates should be MZ: 100%; DZ: 50%
What does it mean if the rates are high in twin studies?
If rates are high, and roughly equal, for both then shared environment is presumed influential
What does it mean if the rates are low in twin studies?
Low rates for both implies effects of non-shared environment
What are adoption studies?
Basic design is to compare those who were adopted as infants with their biological and adoptive parents and/or siblings
Sometimes compare twins adopted as infants (“reared apart”) to those who were not (“reared together”)
What do rates mean in adoption studies?
If concordance rates are higher with bio parents than adoptives, biological factor is assumed; if reverse, then environment is accountable
Why do we calculate heritabilites?
To examine how phenotypes may be attributed to variation in genotypes
Compare similarity in personality between people who are and are not related and people who are related to different degrees
Monozygotic (MZ) vs. dizygotic (DZ) twins
• Assumption: Traits and behaviors influenced by genes should be more similar among more closely related people
Concordance rates and the heritability quotient :
{rMZ –rDZ } X 2 (Makes some further assumptions) Average heritability coefficients for many traits for twins is
around .40, and from non-twin studies around .20
• Suggests that the effects of genes are interactive and multiplicative (and many traits are likely polygenic)
What does heritability tell you?
Genes matter: not all of personality comes from experience
Etiology of disorders
Insight into the effects of the environment on personality development
Shared family environment does not seem to matter very much: The average correlation of personality for adopted siblings is only .05.
•Probably more accurate to say that non-shared family environment more important
Heritability: Effects of parent training-
influences behavior and emotional control; affects aggression and personality measured with direct observation.
Heritability: Based on behavior-
Shared family environment affects behavioral outcomes such as juvenile delinquency, aggression, and love styles
Heritability: Research with self-reports-
People may focus more on traits that make them different from their siblings rather than on similarities.
