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Biological Approach to Personality - Coggle Diagram

- - - - A dominant bodily fluid (“humour”) is associated with a personality type:
        
        Phlegm: Phlegmatic, quiet, unemotional
        
        Yellow bile: Choleric, impulsive, easily angered, irritable
        
        Blood: Sanguine, lively, optimistic, courageous
        
        Black bile: Melancholic, sad, depressive, pessimistic
        -> Perfect temperament would be balanced when all four exist equally
  - - - Phrenology → personality traits are found to be localised and related to different brain structures, which vary in their volume (DeYoung et al., 2010)
  - - - Criminal personality → People are likely to differentiate criminal faces from non-criminal faces (Valla et al., 2011)
  - - - 3 different body types:
        
        Ectomorphs - thin, leaner fragile bodies, introverted, self-conscious
        
        Mesomorphs - muscular and rectangular body, aggressive, courageous
        
        Endomorphs - well rounded bodies, tolerant, pleasant, likeable, want others to like them
- - - - Amygdala - overactive amygdala associated with:
        
        Anxiety, fear
        
        Neuroticism
        
        BPD
        
        Negative emotions such as anger and fear
        
        Important role in computing the degree to which a stimulus offers impending threat or reward
      - Phineas Gage:
        
        1848 railroad supervisor stood in the wrong place and a 3-foot rod was sent through his left cheek, into the frontal lobes of his brain and out through the top of his head
        
        Lived for another 15 years
        
        Retained some degree of mental functioning
        
        However, his personality was fundamentally changed
        
        Became irrevent, impateint, rude, obstinate
        
        Inability to understand the emotions of others, and to appropriately regulate own impulses and feelings
      - Elliot:
        
        Reported headaches and had a suspected brain tumour
        
        Had surgery to remove tumour which removed a good deal of his cerebral cortex
        
        Like Gage could speak clearly and no memory impairment
        
        However, had serious judgment impairmnet
        
        Lacking in rational decisionmaking
        
        Inability to use emotional reactions
        
        Finding from both:
        Feelings tie the body to the brain. Without the ability to connect emotions to thinking, Gage and Elliot lost not only an important part of life's expereince, but also a crucial component of the ability to make decisions
        
        Somatic marker hypothesis
        Damasio (1994); emotions enable people to make decisions that maximise good outcomes and minimise bad ones, and to focus on what is really important
        
        The frontal lobes are centres of cognitive control, serving to anticipate the future and plan for it
    - - DeYoung et al. (2010)
        Tested whether the volume of different brain regions would correlate with the Big 5 traits (influence of phrenology)
        
        Assumed:
        “A greater-than-average volume of a specific brain structure may signify greater-than-average power to carry out specific functions associated with that structure, on the assumption that larger populations of neurons can produce larger outputs and can therefore be more influential than smaller populations of neurons.”
        
        Method
        
        116 participants
        
        Big 5 measure by Costa and McCrae
        
        Structural brain scans to determine which parts of the brain are more or less developed
        
        Findings
        Significant relationships between different brain regions and personality traits
        
        Neuroticism - associated with a few different areas e.g. posterior hippocampus and dorsomedial PFC, many regions appear to be involved in emotion regulation, threat, and punishment sensitivity
        
        Conscientiousness - middle frontal gyrus was more developed among people who were high in conscientiousness
        
        Similar for extraversion
        
        Agreeableness - associated with less volume in posterior CC (on the right) and more volume on the STS (left)
  - - - Testosterone - male sex hormone. Associated with aggression, dominance, anti-social behavioiur
        
        Oversimplication to conclude it causes aggression
        
        Seems to play a role in the control and inhibition of aggressiveness and sexuality - including normal assertiveness and perhaps even general activity level - as well as the normal range of sexual function and responsiveness in both sexes
        
        Cortisol - stress hormone. Associated with neuroticism, anxiety, depression
        
        Chronically high levels of cortisol with people who have stress, anxiety, and depression
        
        Chronically low levels of cortisol are associated with PTSD
        
        Oxytocin - love hormone. Associated with less agression
        
        Another hormone in the stress-response cascade
        
        In females, promotes nurturant and sociable behaviour along with relaxation and reduction of fear (the opposite of fight or flight)
        
        Causes people to be less fearful
    - - Dopamine - helps our brains control how we move our body but also related to rewards
        
        Associated with extraversion, impulsivity, sensation seeking, openness
        
        Severe lack of dopamine is the basis of Parkinson's disease
        
        One recent theory proposes that two fundamental dimensions of personality - stability and plasticity - organise the traits of the Big Five into two groups.
        A large amount of evidence suggests that the dopaminergic system is the foundation of plasticity, defined as a "general tendency to explore and engage with possibilities"
      - Serotonin - inhibits behavioural impulses, when depleted is associated with depression
        
        Low serotonin associated with neuroticism and sensation seeking
        
        Plays a role in the inhibition of behavioural impulses (stopping yourself from doing something unattractive yet dangerous)
        
        Norepinephrine - fight or flight responses
        
        Is both a neurotransmitter and a hormone but mainly acts as a neurotransmitter
        
        Associated with neuroticism
        
        Brain concentrated on source of threat in fight or flight - with higher levels of norepinephrine we are more likely to be neurotic
        
        Market for SSRIs may be more than $20bn per year in the US
        
        These pills are not 'happy pills' but seem to make negative emotions less severe whilst leaving positive emotions unaffected
    - - Correlation ≠ causation
        Research suggests changes in the environment and life experiences can affect changes in biochemistry
        e.g. increase in testosterone in women with 'male dominated' jobs
  - - - Twin study method
        
        Self-report measures
        
        Heritability coefficient → identical twins are given a particular self report test, both twins score that test, for pairs of twins you calculate the correlation coefficient between scores of twins, subtract them and then multiply by 2
        
        Interpretation of hertiability is debateable. Not really just about nature vs. nurture
        
        Basically the value is showing there is a genetic cause of a trait and there are some personality and other traits, if they are more similar in identical and not non-identical twins it points out there is a genetic cause
        
        For most traits:
        
        The estimates of heritability garnered from studies of family resemblance that don't include twins average about 20% or half the average heritability estimed from twin studies
        
        That is, estimates of heritability based on twin studies assume that individual genes and the environment act independently to influence personality, and these influences can simply be added up
        
        But, genes can operate differently depending on the other genes that are present - genes will express themselves in different ways in different environments
        
        As a result, while heritability estimates based on twins may be too high, those based on broader family relationships may be too low
        
        Bouchard (2004) Heritability of Big 5
        
        Highest is openness to experience - 0.57
        
        Extraversion - 0.54
        
        Conscientiousness - 0.49
        
        Neuroticism - 0.48
        Agreeableness - 0.42
        
        Major meta-analysis concluded that the environment shared by siblings growing up was important in the development of several types of psychopathology during the period between childhood and adolescence:
        
        Including conduct disorder, rebelliousness, anxiety, and depression
        
        Only exception was ADHD which for the shared family environment did not seem to matter
    - - A) Candidate gene approach
        
        Explores the prevalence of specific genes in a population high or low on a particular trait
        
        Not replicable results
        
        DRD4 - affects dopamine
        Approach-related personality traits → extraversion, sensation seeking, novelty seeking
        
        Associated with risk for ADHD which makes sense given the association between dopamine and regulation of cognition and behaviour as well as realted personality trait of impulsivity
        
        DRD2 - also related to dopamine
        Impulsivity, obesity, substance abuse
        
        COMT - encodes a protein that breaks down the neurotransmitters dopamine, epinephrine, and norepinephrine
        Extraversion and reasoning abilities
        
        Related to increased dopamine in PFC which leads to increased extraversion and reasoning ability
        
        Thousands of different genes are probably involved in complex traits such as sensation seeking or proneness to anxiety. The chance of finding a single gene that has a simple, direct, and easily understood effect on impulsiveness, anxiety or any other aspect of personality is virtually nil
      - B) Genome-wide associations
        
        Much more promising than approach A)
        
        Needs very large samples to identify small effects (as the effect of a single gene is very low)
        
        Investigates relationships between millions of DNA variants, which are called single nucleotide polymorphisms (SNPs) and phenotypic (personality) traits in very large samples
        
        Many SNPs are combined into genome-wide polygenic scores (GPS)
        
        GPS (in relation to a particular trait) is an individual score that can be used to predict genetic influences on personality traits - e.g. find out scores for different kinds of GPS e.g. neuroticism which can then be correlated with a measure for neuroticism
        
        Genetic variants have been found to be associated with traits related to happiness, depression, and anxiety
    - - Genes tend to interact with the environment
        
        Epigenetic influences are important
        Genes most certainly affect personality, and personality modifies, creates, and selects environments, which in turn may shape our personality during our life - impossible to disentangle personality from our environment
        
        Caspi et al. (2003)
        Pioneer in exploring implications of gene-environment interactions
        
        Followed group of children in NZ for decades
        
        Assessed SES status and other environmental factors and then whether they experienced depression at the end of a 5 year period (between 21 to 25)
        
        Short allelle of 5HTT gene were more likely to experience depressoin after stressful experiences than those without this allele
        
        But, no difference in outcome between those with the long allele and those with the short allele if they had not suffered any stress
        
        Perfect example of genotype-environment interaction: the genotype is important, but only for people who have experienced a certain kind of environment
        
        Active person environment = 'niche picking' people tend to select and create environments that are compatible with and may magnify their genetically influences tendencies
        Reactive person environment = the same environments that promoe good outcomes for some people can promote bad outcomes for others and vice versa
    - - If there are different genes underlying different personalities, then this has a survival value (at least thats what evolutionary theory tells us)
        
        Evolutionary psychologists believe that those characteristics that helped humans survive are more likely to be present in future generations
        
        Adaptive value is context dependent
        
        Certain personality traits are adaptive in certain contexts but not in others