PERSONALITY AND THE BRAINPERSONALITY AND THE BRAIN

Professor Glenn Wilson, Gresham College, London

WHAT IS PERSONALITY?WHAT IS PERSONALITY?Study of individual differences – what makes one person different from another.

Given the same situation people react differently.

Personality = consistent patterns of behaviour that differentiate people .

Traits are stable and enduring (c.f., states).

LEVELS OF PERSONALITYLEVELS OF PERSONALITYPersonality has antecedents (genes and biological structures) and consequences (laboratory and social behaviour). (Eysenck, 1997)

FACTOR ANALYSISFACTOR ANALYSISStatistical classification method used in modern test

construction.Reduces matrix of intercorrelations to main factors

underlying it.Tells how many factors needed to explain a field.Loadings on items give clues as to content (and

appropriate name) for factor.

MAIN SYSTEMSMAIN SYSTEMS

H.J.Eysenck 3-factor solution (Extraversion,

Neuroticism, Psychoticism).Big 5

E, N, Agreeableness, Conscientiousness, Openness.

J.A.Gray E & N rotated to Anxiety &

Impulsiveness = Behavioural inhibition system (BIS) vs Behavioural activation system (BAS).

EYSENCK’S DIMENSIONSEYSENCK’S DIMENSIONS

Eysenck’s initial personality system comprised two independent dimensions, (E and N)

Compared with the ancient Greek classification of the “four humours”.

Later added a third (orthogonal dimension) called Psychoticism (P). This included bizarre, impulsive & anti-social tendencies.

EYSENCK’S THIRD DIMENSION (P)Psychoticism conceived as independent of E and N. Includes Impulsivity, Psychopathy, Tough-mindedness, Risk taking, Bizarre thinking.

EPQ SAMPLE ITEMSEPQ SAMPLE ITEMSExtraversionCan you get a party going?Do you have many different hobbies?

NeuroticismDo you suffer from your “nerves”?Are you often troubled by feelings of guilt?

PsychoticismWould you take drugs which may have strange or

dangerous effects?Would it upset you to see a child or animal suffer? (-ve)

LieAre all your habits good and desirable ones?As a child were you ever cheeky to your parents?

EPQ SUBFACTORSEPQ SUBFACTORSFor some purposes, research or clinical, it is useful to subdivide the 3 major factors into more specific subtypes.e.g., N may be separated into self-esteem, depression, anxiety, guilt, obsessionality, etc.

REINFORCEMENT SENSITIVITY THEORY Gray’s theory rotates E & N diagonally to Anxiety (Behavioural Inhibition) and Impulsivity (Behavioural Activation)

GENETIC FACTORSGENETIC FACTORSStable temperament observed from birth (e. g. act ivi ty, sociabi l i ty, emotional react i vi ty) .MZ twi ns more similar than DZ twins.MZ twi ns r eared apart are st i l l very al i ke.Roughly hal f of vari ance is genet ic – rest most l y non-shared envi ronment; f ami ly envir onment seems rat her unimpor tant .Gene loci now bei ng discovered -connect wit h neurot ransmit t ers, e. g. dopami ne ( novel ty-seeki ng) serot onin (neurot icism).

PERSONALITY GENETICSPERSONALITY GENETICSThe contribution of genetics to personality is revealed in twin studies. Ids are much more similar than frats on Big 5 dimensions.

PHINEAS GAGEPHINEAS GAGE

Daguerreotype of railway worker P. Gage holding the iron bar that, in 1848, blew upward through his brain. He was taken away still conscious and made a remarkable recovery, living 11 more years, though his personality was changed. He appeared as emotionally disinhibited (c.f. leucotomy patients).

DAMAGE TO GAGE’S BRAINDAMAGE TO GAGE’S BRAINVan Horn et al (2012) estimated that 4% of Gage’s cortex was destroyed and 11% of white matter in the frontal lobe. This included tracts connecting the frontal cortex to limbic (emotional) areas. Gage’s behaviour was described at the time as “fitful, irreverent, impatient and unrestrained”.

E AND CORTICAL AROUSALE AND CORTICAL AROUSALEysenck proposed that

introverts had a reticulo-cortical system that led to higher arousal levels in the cerebral cortex.

Many experimental observations support this:

Introverts more reactive to standard stimulus (e.g. lemon drop).

Require more sedative/analgesia to produce same effect.

Stimulants make people more introvert; sedatives make them extravert.

Skin conductance higher in introverts across the day.

EXTRAVERSION IN THE BRAINEXTRAVERSION IN THE BRAIN

Extraverts show lower levels of resting fMRI activity than introverts in several brain regions predicted by Eysenck’s theory.Extraverts’ arousal shifts more during a memory task.Colour depicts strength of correlation of resting signal intensity with E. (Kumari et al, 2004)

EXTRAVERSION & BRAIN VOLUME EXTRAVERSION & BRAIN VOLUME Extraverts have less white matter in areas that include ascending projections to parts of the cortex concerned with behavioural control (colours show negative correlation of E with brain volume).

Es also have less gray matter in various parts of the cortex, esp. right prefrontal and right temporo-parietal areas concerned with restraint, introspection & social intelligence.(Forsman et al, 2012)

BRAIN-DAMAGE IN PSYCHOPATHSBRAIN-DAMAGE IN PSYCHOPATHS

Psychopaths often have structural and functional impairments to the connections between emotional areas (e.g., amygdala) and brain areas controlling decision-making and conscience (prefrontal cortex).

Diagram from Motzkin et al, (2011) shows reduced connectivity in psychopaths as indexed by fMRI.

ANATOMY OF PERSONALITYANATOMY OF PERSONALITY

DeYoung (2010) found MRI brain structure correlates of Big 5 personality traits.

E = vol. in medial orbitofrontal cortex (reward processing).

C = vol. in lateral prefrontal area (planning/control).

N = vol. in various threat/punishment regions.

A = vol. in “mind reading” areas.

N AND STARTLE RESPONSESN AND STARTLE RESPONSES

The startle response (e.g., eyeblink amplitude) measures anxiety. When people watch frightening film-clips, high N individuals usually show greater SR. However, when material is disgusting and inescapable, high N individuals show defensive blunting (inhibited response).(Wilson et al, 2000)

BLUNTING IN THE BRAIN BLUNTING IN THE BRAIN

Although N goes with higher fear ratings, fMRI activity in many brain regions is actually reduced in high N individuals in “shock” vs “safe” trials.(Kumari et al, 2007)

Behavioural Inhibition is associated with high resting EEG in the right posterior dorsolateral prefrontal cortex (Shackman et al, 2009).

ANXIETY IN THE PREFRONTAL CORTEX

INHIBITING BRAIN WAVESINHIBITING BRAIN WAVES

High levels of alpha oscillations, and low delta, are associated with inhibitory personality (neurotic-introversion)Knyazev (2010).

ADDICTIVE PERSONALITYADDICTIVE PERSONALITYAddictive behaviours are predicted by negative emotionality (anxiety, anger, inability to cope with stress) and lack of constraint (disregarding rules, risk-taking).(Slutske et al, 2005).

DOPAMINE & IMPULSIVITYDOPAMINE & IMPULSIVITYImpulsivity is associated with greater amphetamine-induced DA release in the striatum and reduced DA receptor binding in the mid-brain.Apparently, impulsive people get more of a “high” because their brains do not bind DA so readily. This may help explain addictiveness.(PET-scans by Buckholtz et al, 2010)

COSTS AND BENEFITSCOSTS AND BENEFITSPersonality extremes have survival advantages and disadvantages.Neuroticism has psychiatric implications (e.g. anxiety, phobias, OCD) but helps to avoid danger.Extraversion promotes meeting and mating, while introversion makes for better parenting.Psychopathy thrives when reliability and trust are normative within the population (deceit less anticipated).

MIGRATION & NOVELTY-SEEKINGMIGRATION & NOVELTY-SEEKINGGenes associated with novelty-seeking (DRD4) are more common with distance out of Africa (Matthews & Butler, 2011).

BIRTH ORDER EFFECTSBIRTH ORDER EFFECTSSibling position is one form of non-shared environment.1st born : serious, studious, responsible.Later born: more outgoing, relaxed, thrill-seeking.Middle-born: economically deprived & resentful.Effects small & not reliably detected but illustrate

possibility of niche-dependent personality differences.

MACHIAVELLIANISM SCORES OF MEN & MACHIAVELLIANISM SCORES OF MEN & WOMEN (Online survey, N = 4814)WOMEN (Online survey, N = 4814)

THE MARS-VENUS GAPTHE MARS-VENUS GAPMen are typically more competitive, cold & risk-taking, women more emotional, warm & sensitive.Data below from study of 10,262 US adults using 16PF Test (Giudice et al 2012). Multivariate effect size is substantial.

EMPATHY IN CHIMPSEMPATHY IN CHIMPSChimps show consolation behaviour when another is upset, suggesting emotional empathy.

This is more common in females than males and has been shown to reduce stress in the recipient.

DIGIT RATIO RESEARCHDIGIT RATIO RESEARCH

EMPATHY vs SYSTEMATISINGEMPATHY vs SYSTEMATISINGBaron-Cohen (2005) describes men as systematisers (relating to things/principles), women as empathisers (people/examples). Asperger’s & autistic people are hypermale in both respects – and show evidence of high exposure to pre-natal testosterone.

SOCIAL PERCEPTION AND THE SGSOCIAL PERCEPTION AND THE SG

Using MRI, Wood et al (2008) found that part of the frontal cortex, the straight gyrus (SG) (in purple) was 10% larger in women than men.Its volume also correlated with feminine personality traits like social awareness.

EPIGENETICSEPIGENETICSThe genes/environment distinction is now known to be oversimplified.Sex differences and personality are impacted by epigenetics – factors determining whether genes will be expressed (switched on or off). These are believed to include maternal stressors, diet and toxins, and may be carried over from previous generations.This is why MZ twins are not always identical. They may even be opposite (e.g., in handedness or sex orientation).