Lecture 4: Genetics and Peronsality Flashcards
What is a Genome?
Genome refers to the complete set of genes an organism possesses. The human genome contains between 20,000 and 30,000 genes. All these genes are located on 23 pairs of chromosomes. Each person inherits one set of each pair of chromosomes from the mother and one set from the father
What is the human genome project?
is designed to sequence the entire human genome—i.e., identify the particular sequence of DNA molecules in the human species . But identifying sequence of DNA molecules does not mean identifying the function of each molecule.
Are most genes the same or different for humans?
- Most genes in a human genome are the same for all humans
- Small number of genes are different for different individuals, including genes that indirectly code for physical traits and for personality traits
What do behavioural geneticists do?
Behavioral geneticists attempt to determine the degree to which individual differences in personality are caused by genetic and environmental differences
What is highly controversial about studying genes and personality?
- Ideological concerns about findings being misused (Many people worry that findings from behavioural genetics will be used (or misused) to support particular political agendas. If individual differences in thrill seeking, for example, are caused by specific genes, then does this mean that we should not hold juvenile delinquents responsible for stealing cars for joy rides?)
- Concerns about renewed interest in eugenics (Many people are concerned that findings from genetic studies might be used to support programs intended to prevent some individuals from reproducing or, even worse, to bolster the cause of those who would advocate that some people be eliminated in order to create a “master race.”)
What is the important take home message about studying personality and genes?
Finding that a personality trait has a genetic component does not mean the environment is powerless to modify trait
What are the 2 goals of behavioural genetics?
1) Determine % of individual differences in a trait that can be attributed to :genetic differences, environmental differences
2) Determine the ways in which genes and environment interact and correlate with each other to produce individual differences
What is Heritability?
Proportion of observed variance in group of individuals that can be explained or accounted for by genetic variance. Proportion of the phenotypic variance that is attributable to genotypic variance
What is environmentality?
- Proportion of observed variance in group of individuals attributable to (non-genetic) environmental variance.
- If heritability of a personality trait is .70, then genes account for 70% of observed (phenotypic) variation, and environment accounts for 30%
What are some misconceptions about heritability?
-Heritability CANNOT be applied to single individual
(Only relevant for discussion of group-level variation)
-Heritability is NOT constant or immutable (can change over time and can be different in different populations)
-Heritability is NOT a precise statistic (Based on correlations, which by nature have degree of imprecision and fluctuation across samples)
What are the 4 behavioural genetics methods?
1) Selective Breeding
2) Family Studies
3) Twin Studies*
4) Adoption Studies
What is selected breeding?
- Cannot be ethically conducted with humans
- occurs by identifying the dogs that possess the desired characteristic and having them mate only with other dogs that also possess the characteristic.
- Selective breeding studies of ….
- Can only occur if a desired trait is heritable
What are family studies?
- Correlates the degree of genetic overlap among family members with the degree of similarity in personality trait
- If a trait is highly heritable, family members with greater genetic relatedness should be more similar to one another on the trait than family members who are less closely genetically related
What is the problem with family studies?
- Members of a family who share the same genes also usually share the same environment—confounds genetic with environmental influences
- Thus, family studies are never definitive
What are twin studies?
- Estimates heritability by gauging whether identical (monozygotic or MZ) twins, who share 100% of genes, are more similar than fraternal (dizygotic or DZ) twins, who share only 50% of genes
- If MZ twins are more similar than DZ twins, this provides evidence of heritability
What are the two assumptions of the twin method?
- Equal environments assumption: environments experienced by identical twins are no more similar than those experienced by fraternal twins. Assumption has largely been supported; sometimes violated
- Representativeness assumption (twins = rest of pop.). Questionable in some ways (prematurity, low birth weight)
What are adoption studies?
- Positive correlations on traits between adopted children and adoptive parents provide evidence of environmental influence
- Positive correlations between adopted children and genetic parents provide evidence of genetic influence
What are the assumptions of adoption studies?
- Adoption studies are powerful because they get around the equal environments assumption (no need for this assumption)
- But, assumption that adopted children and their adoptive and genetic parents are representative of the general population
What is a potential issue of adoption studies?
Potential issue if selective placement of adopted children. Research suggests this is not occurring
What is an ideal design?
- Design that combines strengths of twin and adoption studies = Twins Separated at Birth
- Correlation between identical twins reared apart is a direct index of heritability.
What are the advantages of each of the behavioural genetics methods?
- Selective breeding: can infer heritability if breeding works
- Family studies: provide heritability estimates
- twin studies: provide both heritability and environmentality estimates
- Adoption studies: provide both heritability and environmentality estimates; get around the problem of equal environments assumption
What are the limitations of each of the behavioural genetic methods?
- Selective breeding: is unethical to conduct on humans
- Family studies: Violate equal environments assumption
- Twin studies: sometimes violate equal assumptions
- Adoption studies: adopted kids may not be representative; selected placement may be a problem if it occurs
What are some of the areas of major research findings?
- personality traits
- attitudes and preferences
- drinking and smoking
What does behavioral genetic research show about personality traits?
- Summaries of behavioral genetic data show heritability estimates for major personality traits (Big 5 traits) of ~ 50%
- Moderately heritable
- Heritability of personality is heavily responsible for fact that personality is stable over time
- But, 50% heritability also means that substantial portion of variance in personality is related to the environment
Is TV watching heritable?
- TV watching is heritable
- Research is still understanding the underlying traits that interact to produce the behavior
Is Divorce heritable?
- Divorce is heritable too
- If 1 + relatives have been divorced, then increased likelihood you will divorce (even if you never met those relatives)
- 1 or more genetically influenced traits are relevant to divorce
What is the behavioral genetic research on drinking and smoking?
- Behavioral manifestations of personality traits such as sensation seeking, extraversion, neuroticism
- Drinking alcohol and smoking cigarettes are stable over time
- Both show some evidence of heritability. Mixed for alcohol drinking, but most show moderate heritability (.36 to .50)
- Higher heritability for alcoholism (.50 across the board)
What is the heritability of happiness?
-Study of 2,310 middle-aged twins (MZ and DZ). Happiness = subjective well-being (SWB)
-Single assessment, re-tested after 4.5 yrs. and 10 yrs.
Findings: Heritability of Stable SWB ~ 80%, Momentary heritability ~ 50%
What do studies that show heritability also suggest?
- Same studies that suggest moderate heritability also provide good evidence of the importance of environmental influences
- Personality characteristics show heritability ranging from 30–50%; So, showing substantial degree of environmentality (50–70%)
What are the two key types of environmental influences?
- Shared: In family environment, features of the environment shared by siblings (e.g., # of books in home, shared routines)
- Nonshared: In family environment, features of the environment that differ across siblings (e.g., different friends, different teachers, treated differently by parents)
What type of environment has has more influence on personality?
-For most personality traits, the environment has major influence, but this influence is primarily in the form of non-shared variables
-For most personality traits, the shared environment has little impact
-We do not know which non-shared experiences (e.g., peers, teachers) have a key impact on personality
More research is needed
Why are psychologists particularly interested in physiology?
Psychologists are particularly interested in causal physiological mechanisms of behavior and the way the environment can interact with these mechanisms.
How many neurons does the brain have, on average?
The average brain has around 100 billion neurons
How much energy ford the brain consume and what are some important parts of it?
Consumes 20% of energy and is only 2% of total body weight. Hypothalamus (it secretes hormones and hormones affect body functioning which can have significant behavioural effects/manifestations). Hippocampus (responsible for the formation of memories). Neocortex and cortex (outer wrinkly brain mass. Right vs. left hemispheric activity)
What physiological measures are most commonly used in personality research?
- Electrodermal Activity (Skin Conductance)
- Cardiovascular activity
- Brain Activity
- Other measures:Biochemical analyses of blood and saliva
What is electrodermal activity (EDA): skin conductance?
- Sensors placed on the skin surface
- Due to increased sweat with arousal, skin conductance of electricity increases
- Some people show EDA in the absence of external stimuli—associated with anxiety and neuroticism
- Advantage: Noninvasive, no discomfort
- Disadvantage: Movement constrained
What is cardiovascular activity?
-Blood pressure: Measure of stress reactivity
-Heart rate: Increases with anxiety, fear, arousal, cognitive effort
-Cardiac reactivity: Associated with Type A personality—impatience, competitiveness, hostility.
Cardiac reactivity (and Type A) associated with coronary heart disease
What is measuring brain activity?
- Brain spontaneously produces small amounts of electrical activity
- Can be measured by electrodes on scalp—electroencephalograph (EEG)
- Evoked potential technique—uses EEG, but the participant is given a stimulus and the researcher assess specific brain response to stimulus
- Brain imaging techniques—map structure and function of brain: Positron emission tomography (PET), Functional magnetic resonance imaging (fMRI)
What have we found using pictures from fMRI
- Neuroticism correlated with increased frontal brain activation to negative images
- Extraversion correlated with increased frontal brain activation to the positive images
What do we find in biochemical analyses of blood and saliva?
Hormones
- Testosterone: aggression, risk taking, competition
- Cortisol: stress, anxiety
- Oxytocin: trustworthiness and morality
What neurotransmitters are associated with personality?
Dopamine: Associated with pleasure
Serotonin: Associated with depression and other mood disorders
Norepinepherine: Associated with fight or flight response
