PERSONALITY AND THE BRAIN

1
PERSONALITY AND THE BRAIN
Professor Glenn Wilson, Gresham College, London
2
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).
3
LEVELS OF PERSONALITY

• Personality has antecedents (genes and
  biological structures) and consequences
  (laboratory and social behaviour). (Eysenck, 1997)

4
FACTOR ANALYSIS

• Statistical 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.

5
MAIN 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).

6
EYSENCKS DIMENSIONS

• Eysencks 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.

7
EYSENCKS THIRD DIMENSION (P)
Psychoticism conceived as independent of E and N.
Includes Impulsivity, Psychopathy,
Tough-mindedness, Risk taking, Bizarre thinking.
8
EPQ SAMPLE ITEMS

• Extraversion
• Can you get a party going?
• Do you have many different hobbies?
• Neuroticism
• Do you suffer from your nerves?
• Are you often troubled by feelings of guilt?
• Psychoticism
• Would you take drugs which may have strange or
  dangerous effects?
• Would it upset you to see a child or animal
  suffer? (-ve)
• Lie
• Are all your habits good and desirable ones?
• As a child were you ever cheeky to your parents?

9
EPQ SUBFACTORS

• For 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.

10
REINFORCEMENT SENSITIVITY THEORY
Grays theory rotates E N diagonally to Anxiety
(Behavioural Inhibition) and Impulsivity
(Behavioural Activation)
11
GENETIC FACTORS

• Stable temperament observed from birth (e.g.
  activity, sociability, emotional reactivity).
• MZ twins more similar than DZ twins.
• MZ twins reared apart are still very alike.
• Roughly half of variance is genetic rest
  mostly non-shared environment family environment
  seems rather unimportant.
• Gene loci now being discovered -connect with
  neurotransmitters, e.g. dopamine
  (novelty-seeking) serotonin (neuroticism).

12
PERSONALITY GENETICS

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

13
PHINEAS 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).

14
DAMAGE TO GAGES BRAIN

• Van Horn et al (2012) estimated that 4 of
  Gages cortex was destroyed and 11 of white
  matter in the frontal lobe.
• This included tracts connecting the frontal
  cortex to limbic (emotional) areas. Gages
  behaviour was described at the time as fitful,
  irreverent, impatient and unrestrained.

15
E AND CORTICAL AROUSAL

• Eysenck 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.

16
EXTRAVERSION IN THE BRAIN

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

17
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)

18
BRAIN-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.

19
ANATOMY 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.

20
N 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)

21
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)

22
ANXIETY IN THE PREFRONTAL CORTEX
Behavioural Inhibition is associated with high
resting EEG in the right posterior dorsolateral
prefrontal cortex (Shackman et al, 2009).
23
INHIBITING BRAIN WAVES

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

24
ADDICTIVE PERSONALITY

• Addictive 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).

25
DOPAMINE IMPULSIVITY

• Impulsivity 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)

26
COSTS AND BENEFITS

• Personality 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).

27
MIGRATION NOVELTY-SEEKING

• Genes associated with novelty-seeking (DRD4) are
  more common with distance out of Africa (Matthews
  Butler, 2011).

28
BIRTH ORDER EFFECTS

• Sibling 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.

29
MACHIAVELLIANISM SCORES OF MEN WOMEN (Online
survey, N 4814)
30
THE MARS-VENUS GAP

• Men 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.

31
EMPATHY IN CHIMPS

• Chimps 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.

32
DIGIT RATIO RESEARCH
33
EMPATHY vs SYSTEMATISING

• Baron-Cohen (2005) describes men as
  systematisers (relating to things/principles),
  women as empathisers (people/examples).
• Aspergers autistic people are hypermale in
  both respects and show evidence of high
  exposure to pre-natal testosterone.

34
SOCIAL 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.

35
EPIGENETICS

• The 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).