The Biological Basis
Eysenck’s Model of Personality
- Personality traits determined by Biological and environmental factors
- 2 Aspect to biological: heritability and physiological substrates
- Substrates: hormones and cortical arousal
- Used criterion analysis, with the goal of having a small number of factors
- Broken down to 3 traits: extroversion, neuroticism, pscychoticism
- Developed around the same time as the Big-Five Model
- Argued that there are a healthier people and a less healthy population, based on reaction to stress
- Problem: problematic research method, leading to racism confusion regarding genetic IQ differences
Biopsycholoscial Theory
By Jeffery Gray, critical to Eysenck’ theory
- Not focused on personality, related to approach and avoid motivation
- Critical of Eysenck’s view of extroversion with relation to arousal
- Instead Gray sees as “opposite” system that can be activated in different situations
Behavioural Activation System (BAS)
- Focused on gaining reward, extroversion and impulsively
- Extroversion experience more positive emotion
- Related to approach motivation
- Negative behaviour: mental disorders (ADHD) and substance abuse
- Positive behaviour: goal oriented
Behavioural Inhibition System (BIS)
- Focused on punishment (avoid punishment)
- Responds to negative cues in one’s environment
- Related to avoidance motivation
- Anxiety based and neuroticism
Fight or Flight System
- Repose to threat
- Fear based
- Connected to the automatic nevus system
Reinforcement Sensitivity Theory
- BAS: handles reaction to all rewarding stimuli; associated with extroversion
- BIS: handles conflict between FFFS (avoidance) and BAS (approach); which underlie anxiety
- FFFS: added “freeze” as a response; handles reaction to all aversive stimuli
Genetic Studying Method
- Genes: does having a particular variant of a gene explain the likelihood of being high or low for a particular trait
- Heritability coefficient
- Neuroscience: is there a relationship between specific brain regions or networks and personality
- FMRI imaging, EEG
- Physiology: is there relationship between autonomic nervous system responses or euro endocrine responses and personality
- Synthetic branches
Heritability
The difference between an inherited trait (average rate) and the heritability (variability) of a trait
- Trait and behavioral variation are almost always about gene and environment interactions
Twin Studies
Monozygotic (identical) Twins Dizygotic (fraternal) Twins Environment Same Same Genetic Same Different
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Criticism:
- Did not consider epigenetic
- Assumption of similar environmental factors are the same with identical and fraternal twins
- Identical twins looks similar, and share the same sex, thus, they are treated more similarity then the fraternal twins
- Shared placenta with some twins, where others did not
- Pregnancy behaviour (environmental) factors are not considered for adoption cases
Epigenetic
- Epigenetic: the study of heritable changes in gene expression or cellular phenotype caused by mechanism other than changes in the underlying DNA sequence
- DNA methylation: biological process by which methyl groups are added to the DNA molecule
- Histone modification: can modify to open or closed chromatin states and thus activation or repression
- Environmental factors ^b5aa24
- Maternal behaviour and gene expression
- Childhood maltreatment and DNA Methylation
- Chronic social defeat stress found to decrease expression of genetic are implicated in normal emotion processing
Genotyping
- Genotype: the genetic composition of al living being
- Identify gene associated with behaviour
- Polygentic: multiple gene are associated with behaviour
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Criticism
- The association might exit, it they are relatively low ()
- Might be too tunnel visioned in a particular gene
Neurology
The most common way of studying neurology is fMRI
- Allow to see brain activity and volume of brain
Extroversion: brain region involved in processing reward information- Connect to Behavioural Activation System (BAS)
Neuroticism: brain regions associated with threat, punishment, and negative affect- Connect to Behavioural Inhibition System (BIS)
Agreeableness: brain regions that process information about the intentions and mental states of other individuals- Compassion is a big part of of agreeableness and social interactions
Conscientiousness: brain region involved in planning and the voluntary control of behaviour- Planning is a big part of conscientiousness
Physiology
- The autonomic nervous system
- Blood pressure; heart rate; galvanic skin response
- Hormones
- Cortisol; testosterone; oxytocin