Neuroscience of personality

Behavior and physiology

-Previously it was thought that our physiology (biological functioning) could not be affected by behavior-New research studying meditation (mindfulness) suggests our behavior can change our physiology-Davidson et al. (2003) randomly assigned people to meditation group or control groupResults showed those in the meditation group demonstrated less anxietyAlso showed greater brain activation on the left prefrontal cortex both at rest and when responding to positive and negative events (left is thought to be more involved in establishing positive emotions vs. right more involved in negative emotions)Depressed people have trouble setting goals to achieve reward and trouble believing goals are possible-Also showed better immune system functioning

Brain Structure and activity

-Brain structure can be looked at via CT (x-rays) or MRI(radio frequency waves)These tests only capture static pictures of the brain-Brain activity can be looked at via EEG (electrodes placed on the scalp to measure electrical activity in the brain), can also use evoked potential (EP), where we measure activity in response to a specific stimulusAlso the PET scan (slightly radioactive glucose injected into the brain) - active regions of the brain use up more glucose

fMRI =

brain activity is monitored over time by tracing blood oxygen levels in the brain (gives different color scans of the brain)= cellular level-Images can be taken while a person is engaged in some cognitive activity or viewing stimuli-Problems with fMRI in personality research = thoughts react within milliseconds vs. 2 seconds for blood flow, also expensive so small sample sizes, time of day, nervousness, and nonindependence error (selection bias)

Transcranial magnetic stimulation (TMS) =

brief electrical current passes through a coil placed on the head-The magnetic field disrupts neuronal activity, sometimes impairing, sometimes enhancing-Has been used to treat depression, fibromyalgia-Not sure how useful would be for personality research

Biochemical activity


Neurological theories of personality


Zuckerman (2005) Three primary temperaments


Eysenck's Pen model

-Believed that differences in personality are genetic and biologicalEvidence to support his view included:- cross-cultural universality in traits - this consistency suggests a strong biological component-There is tremendous consistency in traits over time, despite changing environments-Responses and habits may change, traits do not-PEN all show moderate heritability

Neurology of extraversion Eysenck

Thought the main difference between introverts and extroverts was arousal (either arousal level or arousability)-Introverts were thought to have an overaroused baseline, so are more likely to act more restrained and inhibited, seeking conditions that will not aggravate the overstimulation-Extroverts let in too little stimulationThus, they both seek to find their optimal level of arousal-Ascending reticular activating system (ARAS) = a pathway that transmits signals from the limbic system and hypothalamus to the cortex, processes the cerebral aspects of arousal and emotion-No difference in arousal level between extraverts and introverts, though sig. difference in how they respond to moderate stimulation (so, arousability or sensory reactivity)

Neurology of extraversion

People's noise preferences and performance outcomes depend on their optimal level of arousal as determined by their personality (Geen, 1984)-Introverts and extroverts engaged in cognitive reasoning task (learning a rule)-Exposed to white noise - 3 conditions - 1. choice = select volume "right for you" 2. assigned same = volume matched 3. assigned different = volume was oppositeIntroverts showed greater arousal in which condition?

Neurology of neuroticism

Eysenck thought that N had to do with stability or instability of the sympathetic nervous system (extrasensitive emotional or drive system)-Extraversion is marked by positive arousal (excitement, energy) vs. negative arousal (fear and anxiety)-People high in N show increase in heart rate in response to intense stimuli, and greater startle response to fearful pics, so more sensitive to negative emotions, not just arousing situations

Reinforcement sensitivity theory

RST = proposed by Jeffrey Gray = personality is the variation in the functioning of the brain-Wanted to identify brain-behavior systems that accounted for important differences among individual and link these systems to standard measures of personality-After 40 years of research, evidence suggests there are three important behavioral systems that do not exactly map onto any existing measure of personality

Systems are presumed to exist based on evidence from neurology, physiology, behavior and personality


Behavioral approach system(BAS) =

organizes reactions to "appetitive stimuli" (enticing, pleasurable, and rewarding)Personality factor related is optimism, impulsiveness, and the emotion of "anticipatory pleasure", can lead to addictive behaviors, high-risk impulsive behaviors, and mania

Behavioral inhibition system (BIS) =

involved in resolving conflicts (choices between things), also activated when there is conflict within one of the other systemsConflict needs to be resolved or may experience anxiety, rumination, hypervigilance which may lead to OCD or GADWhen activated, people are more sensitive to punishment and more cautious (too little = risk proneness, too much = risk aversion and GAD)

BAS similar to Extraversion, BIS to Neuroticism


Evidence for the three systems


How quickly do people learn from rewards and punishments?

-Strong BAS=more sensitive to reward, so will learn more quickly by responding than by withholding a response-Strong BIS=more sensitive to punishment, so will learn more quickly by withholding a response than by responding-People with a reactive BAS learn correct responses faster from reacting-People with high scores on a mixed FFFS/BIS scale, or high scores on anxiety scale learn faster from withholding-Which statement describes you better?"Nothing ventured nothing gained" vs. "Better be safe than sorry

Historical perspective

-Franz Joseph Gall (1790's)created phrenology, he reasoned that certain functions of the brain were localized in parts of the cerebral cortex (also believed that the size, shape, and location and size of bumps on scalp were related to specific characteristics)Although not true, spurred research which eventually led to the development of the fMRI-Wilhelm Wundt (1884)was critical of both phrenology and brain localizationTheories of localization fail to account for the connectivity of ideas in the mind, and the complex interaction of brain systems

The various parts and systems of the brain work together to impact behavior

Diffusion Tensor Imaging (DTI) = special type of fMRI that traces the diffusion of water in cells, can highlight connections between cortical and subcortical regions

A key difference between E and N is in how emotions are experienced


The Cortex and the amygdala


E and N are both correlated with activity in the temporal (emotions) and frontal (control consciousness and emotion) parts of the cortex

However it differs in that extraverts show more activity in response to what type of stimuli? Vs. people high in N??

Left-right asymmetry

-The right frontal and prefrontal cortexes are more active than the left during negative emotions and vice versa-People differ in how large these relative differences are in responding to pos and neg emotions, and these differences are present as early as the first year of life-People with greater left asymmetry report more pos emotions when exposed to specific stimuli (neg = more right asymmetry)-High N, shy, inhibited children and depressed adults show greater_____ asymmetry?-How can we help ourselves? Meditation is associated with greater left asymmetry-Though not sure if its actually the meditation associated or other aspects of people who are likely to practice meditation

The amygdala


Biochemical Differences

-Remember, introverts have greater sensitivity to sensory stimulation (arousability)-They are also more sensitive to fluctuations in dopamine as a result of sensory input (might explain preference for quiet and solitude)-Extraverts have greater dopamine activity in general (dopamine system connects with the amygdala)-May have more extensive dopamine pathways or greater responsiveness to dopamine in general-Serotonin and parts of the brain sensitive to serotonin are involved with mood regulation, depression and anxiety disorders (low levels)-High N are more likely than emotionally stable people to have the short allele of a serotonin transporter (less serotonin in their system, places at risk for developing mood and anxiety disorders

Impulsivity and sensation seeking

seeking of varied novel, complex, and intense sensations and experiences, and the willingness to take physical, social, legal, and financial risks for the sake of such experiences" (Zuckerman, 1994, p.27)-Not so much into the danger part, more the fun part-More willing to volunteer for studies involving unusual experiences-Measured by the sensation-seeking scaleExperience seeking - measures the desire for moderate arousal through different kinds of experiences (mind and senses), "I would like to explore strange places" (similar to O)Boredom susceptibility - measures need for change and variety, aversion to routine and sameness, "I prefer friends who are excitingly unpredictable

Thrill and adventure seeking -

measures arousal seeking through physical sensations produced by speed, height, danger, and unique experiences, "I like to do frightening things"Disinhibition - the extent to which people have lowered social inhibitions (letting loose), "I like wild parties", -Men score higher than women, young people higher than older (peaks in late teens and early 20's)-Higher score = more likely to engage in risky sexual behavior, more partners, earlier age, smoke more, drug and alcohol use-Greater marital satisfaction when partners are similar, higher divorce rate for both low in sensation seeking

Sensation seekers differ in how they react to novel stimuli


In general, we know about 40% of variance in a personality trait is genetic, the rest is environmental?

But we just discussed how our thoughts and behaviors can affect our physiology.....