6: Genetics and personality Flashcards
Behavioral genetics is the study of what?
Both the study of the effects of genes but also the effect of the environment
Behavioral genetics does not address the all effects of the genes or the environment. How is it limited?
It is limited to the study of how genes and the environment lead to variation in traits
MZ twins?
Monozygotic twins - Come from a single fertilized egg that divides into two at some point. Always the same sex
DZ twins?
Dizygotic twins - Comes from eggs that are separately fertilized
What is the genotype?
The DNA pattern specific to an individual
What is phenotype?
The physical form and behavioral patterns of the individual
What is heritability?
The percentage of phenotypic variation that is due to genetic variation
Which of the following have high and which have low heritability? # of eyes is not genetic Visual acuity Eye color Sexual orientation Sociosexual orientation Verbal intelligence
# of eyes is not genetic Visual - high heritability Eye color - high Sexual orientation - low Sociosexual orientation - high Verbal intelligence - high
Does variation refer to a population or an individual?
It refers to a population NOT an individual
The difference between you and other members of the population = heritability.
When a difference in a population is due to genetics
“How much” studies uses what method?
quantitative behavioral genetics - quantifies the importance of genes by identifying how much phenotypic similarity on a trait can be predicted by genetic similarity (often twin studies)
“Which” studies uses what method?
Molecular genetics - identifies particular versions of the genes which are found more frequently among those with different phenotypes
EX: the DRD4 gene - the novelty gene
On the genes that very between people identical twins will be similar on how many %?
100%
On the genes that very between people siblings and fraternal twins will be similar on how many %?
50%
On the genes that very between people adoptive children and their adoptive parents will be similar on how many %?
0%
How come that people and chimps are 98% genetically similar?
When you’re using the molecular metrics - when you are looking at a basepair on a basepair basis you get a really high degree of similarities - BUT this is not what personality psychologist are intereseted in - they look at quantitative - genes that VARY between people
Heritability accounts for how much when it comes to height?
0.9
Heritability accounts for how much when it comes to depression?
0.60-0.70
What is a gene-environment correlation (rGE)
When a given gene is found more often in people who are in certain environmental contexts
There are 3 different types of gene-environment correlation (rGE), what are those?
Passive (when parents provide book environment)
reactive/evocative (The child is evocing a response that makes the environment and genes match - parents gives the child more books)
active (control of own environment by buying books yourself)
What is a passive gene-environment correlation?
When parent provide both genes and the environment to the children yet the child does nothing to obtain the environment
EX: parents who are verbally inclined pass on genes to their children that make them verbally inclined. However, because the parents are highly verbal, they buy a lot of books. Thus, there is a correlation between the children’s verbal ability and the number of books in their home, but it is passive in the sense that the child has done nothing to cause the books to be there
What is reactive gene-environment correlation?
When parents respond to children differently, depending on the child’s genotypes.
This is achieved because people react to children differently, based in part on the children’s heritable dispositions.
What is an active gene-environment correlation?
When a person with a particular genotype creates or seeks out a particular environment
EX: High sensation seekers, for example, expose themselves to risky environments: skydiving, motorcycle jumping and drug taking
The personality trait of the biological parent can predict the behaviour of the adoptive parent, how?
The trait in the adoptive child (from the biological parents) - shape the behavior of the adoptive parents
“Corne pone”- theory
Parents provide their children with moral, poltical and religious beliefs
Indirectly: by raising them within organizations that reflects their beliefs
Directly: By discussing their opinions with the child
The idea is that the political party that you vote for is determined by the discussions at the dinner table
What happens to the political beliefs of the child, when it leaves the household?
Once we move out, we start to become more our own people who are more influenced by genetic influence and not the environment
So the political beliefs are no longer influenced by your parent’s belief
When we talk about heritability for both politics and IQ, what do we have to pay attention to?
You always have to consider the age
When talking about gene-environment correlation, which one of these matters most?
We can’t say!
We can’t be sure if the environment matters or it is the genes that cause the environment to matter
When do genes matter most?
When the individual is most able to act on their dispositions
What is genome?
the total collection of about 3.2 billion base pairs, the ‘string of letters’ (ACTG) of the DNA
What are alleles?
different versions of the same gene
Phenotypic variance
observed individual differences, such as in height, weight or personality.
Environmentality
the proportion of phenotypic variance that isnotattributable to genetic variance
Can heritability be applied to a single individual?
NO!!
Is heritability a constant?
NO! It applies only to a population at one time and in a particular environment. Heritability is ONLY a statistic
At the population level, we can partition the differences into 3 sources - which?
- Differences in genes
- Differences in environment
- The interaction between the genes and environment
What are the 4 most common behavioral genetics methods?
- Selective breeding with aminals
- Family studies
- Twin studies
- Adoption studies
Why can’t result from family studies not be viewed as definitive?
Because family members who share the same genes also typically share the same environment.Two members of a family might be similar to each other not because a given personality characteristic is heritable but, rather, because of a shared environment
What is the main advantage of adoption studies?
They allow us to get around the equal environments assumption, which must be made in twin studies
What is the most powerful behavioral genetic design?
One that combines the strengths of twin and adoption studies at the same time by studying twins reared apart
What are the most commonly studied personality traits in behavioral genetics?
extraversion and neuroticism
Does heritability play a role in alcohol consumption?
Yes - Most studies find moderate heritability (0.21-0.56) for drinking
Alcohol consumption patterns in adults are stable, and the genetic contributions are largely responsible
What is the heritability for marrige?
The heritability for marriage turned out to be 68%
-Getting divorced is also genetically influenced. This could be linked to specific personal traits
Molecular genetics?
techniques designed to identify the specific genes associated with personality traits
The DRD4-gene codes for what? And what is this gene associated with?
This codes for a protein called dopamine receptor. Respond to the presence of dopamine.
Novelty seeking
- Individuals with so-called long repeat versions of the DRD4 gene were found to be higher on novelty seeking than individuals with so-called short repeat versions of this gene.
BUT - A recent critical review noted that there is still no clear consensus about which genes are associated with which personality traits
What is shared environmental influences?
Features of the environment that siblings share
Ex: the number of books in the home, having a TV in the home or not
What is non-shared environmental influences?
Features of the environment that siblings don’t share
EX: They might have different groups of friends,
different sports
What impact does the shared environment have on personality variables?
For most personality variables, the shared environment has either little or no discernible impact
Genotype-environment interaction
Individual differences ininteractionswith the environment that affects performance
EX: An introvert and an extrovert might react differently to the same situation ex: noise in the room
genotype-environment correlations can be positive or negative - how so?
the environment can encourage the expression of the disposition or it can discourage its expression
Environmentalist view
the view that personality was determined by socialization practices, such as parenting style
