Transcript personality and brain

PERSONALITY AND THE BRAIN
Professor Glenn Wilson, Gresham College, London
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 PERSONALITY
Personality has antecedents (genes and biological
structures) and consequences (laboratory and social
behaviour). (Eysenck, 1997)
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.
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).
EYSENCK’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 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?
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 selfesteem, depression,
anxiety, guilt,
obsessionality, etc.
REINFORCEMENT SENSITIVITY THEORY
Gray’s theory rotates E & N diagonally to Anxiety (Behavioural
Inhibition) and Impulsivity (Behavioural Activation)
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).
PERSONALITY GENETICS
The contribution of genetics to personality is revealed in twin
studies. Ids are much more similar than frats on Big 5
dimensions.
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).
DAMAGE TO GAGE’S BRAIN
Van 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 AROUSAL
Eysenck proposed that
introverts had a reticulocortical 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 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
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 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 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 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
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)
ANXIETY IN THE PREFRONTAL CORTEX
Behavioural Inhibition is associated with high resting
EEG in the right posterior dorsolateral prefrontal cortex
(Shackman et al, 2009).
INHIBITING BRAIN WAVES
High levels of
alpha
oscillations, and
low delta, are
associated with
inhibitory
personality
(neuroticintroversion)
Knyazev (2010).
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).
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)
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).
MIGRATION & NOVELTY-SEEKING
Genes associated with novelty-seeking (DRD4) are
more common with distance out of Africa
(Matthews & Butler, 2011).
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.
MACHIAVELLIANISM SCORES OF MEN &
WOMEN (Online survey, N = 4814)
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.
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.
DIGIT RATIO RESEARCH
EMPATHY vs SYSTEMATISING
Baron-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 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.
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).