Biological domain

• phenotype variance is the observable individual differences
• genotypic variance is the individual differences in a total collection of genes\
• A heritability of .5 = 50% of observed phenotypic variation is attributed to genotypical variation
• The equal environments assumption is a flaw in twin studies which assumes that the environments experienced by twins are no different
• Adoption studies can help get around the equal environments assumption because it examines the correlation between the adopted children, their environment vs their parents
• Extraversion and neuroticism are found to have a .51 correlation for gene expression in monozygotic twins and a .21 for fraternal twins
• The Minnesota Twin study showed that traditionalism is highly heritable
• the heritability of personality is heavily responsible for the fact that personality traits are stable over time
• A Monozygotic twin who smokes iswho 16 times more likely to have a twin that also smokes in comparison to those who did not smoke or drink
• Genes influence the propensity to marry or stay single based on personality. Men who stay married are higher in social potency and achievement.
• Physiological psychologists believe people who are introverts have an overly sensitive nervous system
• Parsimony in research is the ability to explain a good amount of behaviour with few constructs
• Gambling is linked with impulsiveness and sensation seeking. The risk of developing a gambling problem may be explained by dopamine receptors and impairment in inhibitory control
• Hebb's theory of Optimal Level of Arousal states that people are motivated to reach an optimal level of arousal
• People differ in their optimal level of arousal. There are also correlations between extraversion and sensation seeking
• Monoamine oxidase maintains the proper levels of neurotransmitters. If there is an excess, it will break down too much of the neurotransmitter. High sensation seekers are though to have lower level of monoamine oxidase in the blood
• Zuckerman's theory of sensation seeking is that people who are high in sensation seeking are more likely to engage in risky behaviours and seek novel situations to maintain their optimal level of arousal
• According to Eysenck's theory, introverts have a higher level of activity in the brain's ascending reticular activity system (ARAS). The ARAS is a structure in the brain stem controlling overall cortical arousal
• In Hebb's optimal level of arousal theory, introverts have a higher baseline of arousal, meaning they are more easily overaroused.
• Eysenck's theory suggests that introverts may prefer quieter environments as they can become quickly overwhelmed by stimuli
• The Reinforcement Sensitivity Theory hypothesizes that there are 2 systems in the brain that are responsible for the sensitivity to rewards and punishments: the Behavioural activation system (BAS), and the Behavioural inhibition system (BIS).
• The behavioural activation system (BAS) is responsive to cues of rewards.
• The behavioural inhibition system (BIS) is responsive to cues of punishment and frustration. It ceases and inhibits behaviour.
• In the Reinforcement sensitivity theory, people differ in sensitivity of BAS and BIS. Those who are high in BIS are more sensitive to punishment, frustration, anxiety, and fear. It is responsible for anxious personalities
• People with high BAS response are sensitive to rewards and it is responsible for impulsive personalities
• The Reinforcement sensitivity theory coincides with Gray's theory that the sensitivity to reward and punishment are linked with various behaviours from being anxious/neurotic and impulsive/extraverted
• Serotonin is associated with depression and anxiety
• Norepinephrine is responsible for activating the sympathetic nervous system for flight or fight response.
• In the Tridimensional personality model, novelty seeking is associated with low levels of dopamine, whereas harm avoidance is an abnormal serotonin in metabolism. Reward dependence is associated with low norepinephrine.
• The DRD4 dopamine gene is associated with high levels of novelty seeking
• Cloninger's Theory explains various types of addictions. It says that alcoholics drink because they are low on dopamine and harm avoidance.
• Gray's theory on novelty seeking and reward sensitivity talks about brain systems involved in learning through rewards and punishments