week 6 Flashcards
twin studies on personality traits
Riemman et al (1997) compared 1,000 monozygotic and dizygotic twins on the big five. Correlations as follows
falconers formula
Heritability can be calculated as: h2 = 2 (rmz-rdz) where r mz and r dz are the correlations
adoption studies on personality
Loehlin et al (1985): Higher correlations between children and biological parents than adoptive parents on traits.
Hershberger et al (1995): No difference in correlations for extraversion and neuroticism in identical twins reared together or apart; difference observed for openness.
Bergeman et al (1993): Substantial genetic influence on openness (40%) and conscientiousness (29%), weak for agreeableness (12%), little evidence for shared rearing environment.
issues with heritability estimates
Heritability assesses genetic variation in a population.
Additive assumption in heritability estimation can be problematic.
Additive genetic actions involve independent gene effects.
Dominant genetic actions involve suppression of recessive genes.
Epistatic genetic actions determine whether other genes are expressed or suppressed.
eysencks biological model to personality
- in 1967, proposed two neural mechanisms in the human brain: excitatory (keeping alert and active) and inhibitory (causing inactivity).
- Arousal is regulated by two independent circuits: reticulo-cortical for extraversion and reticulo-limbic for introversion.
Introverts are over-aroused - emotionally, while extraverts respond to external stimuli.
Neurotics are emotionally aroused, while emotionally stable individuals are less aroused. - Geen (1984) found that extraverts chose higher noise levels during a task, supporting Eysenck’s theory.
-Kehoe et al (2012) noted a complex link between neuroticism and arousal, associating it with increased reactivity around emotional arousal and positive stimuli.
grays reinforcement sensitivity theory
Behavioral Approach System (BAS): Motivates approach behaviors, sensitivity to potential rewards, and seeking.
Behavioral Inhibition System (BIS): Motivates avoidance based on conditioned sensitivity to potential punishment or non-rewarding stimuli.
Fight/Flight/Freeze System: Responds to threats with a tendency.
Gray (1990) proposed two independent dimensions: sensitivity to reward and punishment.
Suggested Eysenck’s E and N dimensions be rotated for more efficient axes of punishment sensitivity (anxiety) and reward sensitivity (impulsivity).
Explains why introverts are more aroused (punishment sensitive/anxious), while extraverts are reward-sensitive (impulsive).
cloinger psychobiological model
Proposed a psychobiological model of personality with four temperament and three character dimensions.
Temperament dimensions are independently heritable, manifest early in life, and involve individual differences in associative learning in response to novelty, danger, or punishment and reward.
Four temperament dimensions: Novelty Seeking, Harm Avoidance, Reward Dependence, and Persistence.
These dimensions are organized as independent brain systems and linked to neurotransmitters regulating behavior and responses to rewards.
Character dimensions mature in adulthood, influencing personal and social effectiveness through insight learning and social concepts.
problems with psycho biological theory
- Inadequate empirical support, only some parts of the theory supported by research evidence
- Relation between neuroticism and arousal was much less well supported than that between extraversion and arousal
- Stewart et al (2004) found that items measuring clonigers traits more closely resemble ffm and eyesenck model
- May be oversimplified
neural correlates of extraversion
Extraversion, revealed in fMRI studies, associates with neural activation in dopaminergic neurons of the reward network, leading to a positive response to pleasant stimuli.
Dopamine manipulation effects vary by extraversion; extraverts respond more positively to stimuli paired with dopamine drug experiences.
Extraversion is positively related to the volume and glucose metabolism in the medial OFC, a region monitoring the reward value of stimuli.
Neuroticism is often linked to the amygdala, modulating attention and sympathetic nervous system arousal in response to danger signals.
It’s also associated with the medial prefrontal cortex (mPFC) and dorsolateral prefrontal cortex (dlPFC), both regulating negative emotions.
Systems implicated in neuroticism are modulated by serotonin, and pharmacological serotonin modulation correlates with a decline in neuroticism, although the relationship is complex.
neural correlates of agreeableness
Empathy research focuses on mentalizing and mirroring in neuroscience.
Mentalizing engages the default network, while mirroring involves the insula and midcingulate cortex.
Agreeable individuals show increased reward circuit activity when a charity receives payment.
Agreeableness is negatively linked to testosterone and positively associated with serotonin.
neural correlates of openness
Openness is associated with individual differences in dopamine function, DeYoung (2013).
Extraversion is linked to encoding stimulus value and functional connectivity between dopaminergic neurons and the nucleus accumbens and caudate nucleus.
Openness correlates with encoding stimulus salience and functional connectivity between dopaminergic neurons and the dorsolateral prefrontal cortex (dlPFC).
Beaty et al. (2016) found that openness is connected to information processing in the default network.
The default network, more active during rest than cognitive tasks, is responsible for self-generated thoughts, internal goal-oriented tasks, and contemplation of the past and future.
neural correlates of consciousness
Structural MRI studies show positive associations between conscientiousness and volume in dlPFC.
The dlPFC is part of the goal priority network, influencing goal determination and attention reorientation.
These associations may be related to serotonin levels, though evidence is inconclusive.
Rueter et al. (2018) found positive associations between conscientiousness and functional connectivity in the goal priority network using resting-state fMRI.
Activation in dlPFC, insula, and ACC, along with their connectivity, is significantly linked to conscientiousness, indicating their role in determining goal priority.
evaluation of neural correlates
- Increasing number of research findings on neural correlates instantations of personality in the brain
However, - A lot of individual pieces of evidence
No intergrative view on personality as hardwired in the brain
three laws of behaviour genetics
The current perspective posits that personality is influenced by gene-environment interactions.
According to Turkheimer (2000), the nature-nurture debate is settled, stating that everything is heritable.
Turkheimer proposes three laws of behavior genetics:
All human behavioral traits are heritable.
The impact of being raised in the same family is smaller than the effect of genes.
A significant portion of the variation in human behavioral traits is not explained by genes or family effects.
nature via nurture
Personality variance is 20%-50% explained by heritability, with minimal impact from shared environment.
Unexplained variance is attributed to the non-shared environment, including unique aspects of parenting and peer influence.
Genetic effects are more detectable than environmental ones because individuals shape their environments.
Barlow (2020) suggests genes influence how we perceive and react to the social world.
Kendler (1997) found genes account for 43–75% of variance in reported social support, with minimal shared environment effects.
Genes partly “cause” environment through self-selection, known as niche building.
