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Flashcards in Genetics and Personality Deck (41):

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.


Heritability: technical issues-

similarity among adoptive families, same culture reduces variability; plus, adoption and its circumstances a confounding variable


True or False: If there is a genetic influence, a trait (or other outcome) is inevitable



True or False:If a characteristic is genetically influenced, it cannot be modified



True or False:If there is a genetic influence, it must be directly responsible for behavior



True or False: genetics and environment are mutually influential



True or False: Genes interact with one another



How do you account for interactions?

Still difficult to statistically account for interactions; You can’t use heritability to determine what percent of a trait is determined by genetics and by the environment.
Traits with little variation will have heritabilities close to zero.


There must be ______ in order for there to be ________

Environment, Behavior


Genes are not causal:

they code for the material


Next steps:

understanding how the development of specific aspects of the nervous system interacts with environmental experience to affect behavior; because genes and the environment interact


Environments can affect heritabilities:

Nutrition and height (heritability will be higher when all children have the same level of nutrition, but lower when nutrition differs and therefore contributes differently to height); intellectual stimulation /educational opportunities and IQ


Genetic expression and social environment:

height and teasing


What are Gene-Environment Interactions

Choice of environment to be consistent with genetic
tendencies: sensation seeking and criminal environments
• The same environment can affect different individuals in different ways: responses to stressful or boring experiences
• Environments can determine how or whether a gene is expressed: A genetic predisposition for stress, anxiety, or aggression may only influence behavior in a stressful environment. The 5-HTT gene and culture


What is epigenetics?

nongenetic influences on a gene’s expression
(stress, nutrition); experience, especially early in life, can influence how or whether a gene is expressed during development; most research has been with rats (stress response differs as a function of early maternal care)


What is a Biological reductionism?

Everything about the mind can be reduced to biology.



We do not know enough about biology, but we do know that
the brain is “built” to interact with itself and with the world.
Biology leaves out most of psychology and does not ask many important psychological questions: What are people thinking? How are people influenced by the environment, including other people?


How do genes effect behavior?

by influencing the propensities or tendencies toward certain behaviors.