Personality

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Biological Basis of Personality
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Which Theories?

• Eysenck
• Cloninger
• Zuckerman
• Gray

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Eysencks Model

• Biological basis - two neural systems
• Introversion/Extraversion differences are based
  upon levels of activity of the cortico-reticular
  loop
• This includes the cerebral cortex, and the
  ascending reticular activating system.
• The reticular formation contains several
  populations of neurons
• Functions include arousal, attention, cardiac
  reflexes, motor functions, regulates awareness
  and sleep
• Reticular formation is a group of nerve fibres
  located inside the brainstem
• Ascending reticular activating system is the
  attention center in the brain
• It is a complex collection of neurons which
  receives information from neurons from the spinal
  cord (the ascending sensory tracts) and runs into
  the midbrain
• It is involved in pain, eye movements and
  alertness
• It has connections to sensory, motor and
  autonomic neurons

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Eysencks model Extraversion/Introversion

• Introverts have higher levels of activity than
  extraverts and are therefore chronically over
  aroused.
• What would this mean in terms of behaviour?

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Eysencks modelNeuroticism

• Neuroticism is related to the activity of the
  visceral brain / limbic system
• Limbic system a system of functionally related
  neural structures that are involved in emotional
  behaviour
• Incorporates the hippocampus, amygdala, singulum,
  septum and hypothalamus
• Regulates emotional states such as sex, fear and
  aggression
• Has interconnections to the cerebral cortex
• Activity of the visceral brain produces autonomic
  arousal
• Is responsible for the fight or flight response
  in the face of danger

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Neuroticism

• High N scorers are more likely to become agitated
  when faced with stressful situations
• Those who score high on N are more likely than
  low scorers to become autonomically aroused
• Heart rate, blood pressure, skin conductance,
  sweating, breathing rate are thought to be
  indices of the activation levels of the limbic
  system

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Eysencks summary

• Biological theory attractive in that it is
  testable
• However test situation!
• Individuals who are already high on arousal
  (introverts) or autonomically aroused will react
  to a situation differently
• If a situation is particularly arousing or
  stressful it can mediate the results

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Alternative to Eysencks

• Grays alternative model
• Behavioural inhibition system (BIS) links to
  punishment sensitivity, anxiety high N, low E.
• Activated by fear and novelty stimuli and signals
  of punishment and non-reward
• Functions to inhibit on-going behaviour and to
  increase arousal and attention
• BIS system is more easily activated in the
  anxious individual
• Anxiolytic drugs?
• Behavioural activation system (BAS) links to
  reward sensitivity, impulsivity high N, high E,
  high P
• Sensitive to signals of reward and non-punishment
• Controls approach behaviour
• BAS system is more active in the impulsive
  individual
• Dopaminergic?

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Cloningers Three Dimensions

• Harm Avoidance, Reward Dependence and Novelty
  Seeking
• Biologically based
• Relate to monoamine system Serotonin,
  noradrenaline and dopamine

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Zuckerman

• One of the leading figures in the biological
  basis of personality
• Criticises both Gray and Eysenck for assuming
  isomorphism a one to one correspondence between
  personality traits and brain systems
• Suggests any personality trait may relate to more
  than one brain system
• A brain system may be related to more than one
  personality trait

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Theories and Evidence?

• So how do we test these theories
• How can we assess whether personality has a
  biological basis?

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Assessments

• Genetics
• Twin studies
• Adoption studies
• Molecular Genetic Studies
• Animal studies
• Electrophysiological studies
• Neurochemistry studies
• Normal controls
• Patients populations
• Animal studies

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Genetic Determinants of Behaviour

• Behaviour in all organisms is shaped by the
  interaction of genes and environment
• The relative importance varies
• Traditionally divided into two categories
• Innate
• Learned

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Can Behaviours be inherited?

• Traditionally a resistance to the notion that
  behaviour can be inherited in particular human
  behaviour
• Accept imprinting in chicks
• But mental disorder in humans?
• The expression of inherited factors almost always
  depends on an interaction of genetic and
  environmental factors
• For instance you may have the genes for being
  tall but have a poor diet

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Species Specific Behaviours

• Instinctive behaviours are now often called
  species-specific behaviours
• Animals may respond to a specific stimuli for
  instance a sign stimulus or releaser.
• Red belly of stickleback
• Fixed action patterns more complex than a
  simple reflex

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Complex Behavioural Traits

• Personality
• Mental Disorders
• Obesity
• Evidence of hereditary

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Genes
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What is the Nature of Genes?

• Chromosomes
• threadlike genetic structures
• consist of matched strands of deoxyribonucleic
  acid (DNA) found in the cell nucleus
• they occur in matched pairs
• humans have 23 pairs in each of their body cells
• each strand of DNA consists of a sequence of four
  nucleotide bases
• adenine, thymine, guanine, and cytosine
• the two strands of DNA that form each chromosome
  are coiled around each other in a double-helix
  (spiral) pattern.

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Genetics

• Mendel (18221884)
• A monk from central Europe
• Studied Pea Plants
• Found that pea flowers occurred in offspring
  without any intermediate colours
• That is - no blending
• What controls this?

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Mendelian Genetics

• dominant gene
• recessive gene
• a gene being defined as the smallest discrete
  unit that is inherited by offspring intact,
  without being broken up or blended (Buss, 1999,
  p. 10)
• genotype
• the underlying genetic potential
• phenotype
• observable traits or characteristics.

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Sexual Reproduction

• Meiosis
• the chromosomes divide, with one chromosome of
  each pair forming a separate gamete
• sperm cell and an egg cell combine to form a
  zygote
• meiosis is very important, because it plays a
  major role in human genetic diversity
• Pinel (1997)
• human beings can produce gametes with 8,388,608
  differing combinations of chromosomes.
• Mitosis
• the number of chromosomes doubles
• followed by a division of the cell to create two
  cells
• involves re-creating huge numbers of copies of
  the original zygote.

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Behavioural Genetics

• Genetic similarity between family members
• children share 50 of the genes of each parent
• siblings share 50 of their genes
• children share 25 of their grandparents genes
• first cousins share 12.5 of their genes
• monozygotic twins (identical twins) have the same
  genetic make-up
• dizygotic twins (fraternal twins) share 50 of
  their genetic make-up.

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Heritability

• The extent to which individual differences in a
  given characteristic or trait are determined by
  heredity.
• It is NOT a measure of genetic determination
• Children who are severely malnourished may show
  less heritability of IQ than others because
  malnutrition or extreme deprivation can place
  constraints on intellectual potential as assessed
  by IQ tests and thus the potential impact of
  hereditary differences. Westen (1996, p. 111).

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Twin Studies

• Twin studies allow study of the effects of
  genes and environment
• If MZ twins are more alike that DZ twins on a
  personality trait, this suggests that the trait
  has a genetic component
• Two types of studies
• Twins raised together
• Twins raised apart

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Adoption Studies

• Children who dont share genes with parents or
  siblings raised in common environment
• Children who share genes but not environment with
  biological parents
• Examination of correlations gives indication of
  relative contribution of genes, shared
  environment and non-shared environment

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Evidence??
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Definitions

• Chromosomes
• threadlike genetic structures
• consist of matched strands of deoxyribonucleic
  acid (DNA) found in the cell nucleus
• Gene
• A segment of DNA found on a chromosome that codes
  for a particular protein, a unit of heredity
• Allele
• is a form of a gene.

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Twin Studies

• Twin studies give personality questionnaires or
  assess personality in MZ and DZ twins
• Examine the twin pair correlation for different
  personality traits
• If personality could be measured without error
  and the genetic contribution was 100 percent -
  What would you expect the correlation to be for
• MZ twin pairs
• DZ twin pairs

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Contributions to personality differences

• Genetic single gene or polygenetic?
• Environmental
• Shared or common environmental factor
• Unshared environmental factor

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Some studies

• Pedersen, Plomin, McClearn, and Friberg 1988
• Assessed Extraversion and Neuroticism
• 95 MZ twin pairs reared apart
• 150 MZ twin pairs reared together
• 220 DZ twin pairs reared apart
• 204 DZ twin pairs reared together

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Evidence for Extraversion and Neuroticism

• extraversion
• MZ twins brought up together 0.54
• DZ twins brought up together 0.06
• MZ twins brought up apart 0.3
• DZ twins brought up apart 0.04
• neuroticism
• MZ twins brought up together 0.41
• DZ twins brought together 0.24
• MZ twins brought up apart 0.24
• DZ twins brought up apart 0.28

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Non-additive Genetic Variance

• Additive genetic assumption - There is a linear
  increase in trait similarity as the proportion of
  genes shared increases
• HOWEVER this may not be true
• Possible explanations
• Genetic Dominance
• MZ will share 100 of the gene dominance effects
• DZ only 25 not 50
• Epistasis
• the interaction between two or more genes to
  control a single phenotype
• MZ genes will be identical but DZ twins unlikely
  to share many of the possible multigene
  configurations
• Therefore likely that MZ twins will be more than
  twice as similar than DZ twins

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Epistasis
RRpp X rrPP RrPP RrPp Rrpp
rrPp rrPP
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Rose
Pea
Parents
Offspring
Single
Walnut
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Shared environment is it really shared?

• Why may the assumption that those who grow up in
  the same household have similar shared
  environments be flawed?

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Shared Environment

• Identical twins may have more similar
  environments eg similar clothes
• Other points
• Those with a more similar personality/temperament
  may be treated more similarly
• Those who look more alike may be treated more
  similarly
• Does similar treatment in childhood relate to
  adult personality scores?

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Genes and the Environment

• Genotype-environment interaction
• Genotype-environment correlation
• Effects which look like nonshared environment may
  well be active G-E correlation in this view MZ
  twins reared apart acquire similar personalities
  because they select similar environments.
• Assessing nonshared environment and G-E
  correlations are major challenges. Environments
  are hard to measure. Existing measures are often
  retrospective and subjective, and may well
  measure genetic effects.

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Summary of results from twin and adoption studies

• All personality traits show some degree of
  heritability (approx 40).
• Shared environment effects are small/zero
  especially in adulthood.
• Non-shared environmental effects are large.
• Evidence for non-additive genetic effects due
  to configurations of multiple genes acting
  together.
• Findings are similar for self- and peer-reports.

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Molecular Genetics

• A polymorphism is a genetic variant that appears
  in at least 1 of a population.
• Phenotypic characteristics can be associated with
  a specific variation at a specific site on a
  given chromosome
• The variation is called a polymorphism
• Examples
• the human ABO blood groups
• the human Rhesus factor

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Psychiatric Diseases

• Schizophrenia
• Depression
• Bi-polar illness
• Autistic Spectrum Disorders
• All show some evidence but these disorders do not
  have clear phenotypic characteristics

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Two main approaches

• Find a candidate gene and compute an association
  between that loci and the characteristic
• Family studies may help
• Conduct a genome sweep
• Very labour intensive

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Alleles

• An allele is a form of a gene. 
• Alleles are located at the same position (locus)
  on homologous chromosomes and are separated from
  each other during meiosis. 
• We always have two alleles for every trait (even
  if the trait is expressed by multiple alleles
• We get one allele from our mother and one from
  our father.

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Papers

• Ebstein, R. P., Novick, O., Umansky, R., et al
  (1996) Dopamine D4 receptor (D4DR) exon III
  polymorphism associated with the human
  personality trait of novelty seeking. Nature
  Genetics, 12, 78-80.
• Benjamin, J., Li, L., Patterson, C., et al (1996)
  Population and familial association between the
  D4 dopamine receptor gene and measures of novelty
  seeking. Nature Genetics, 12, 81-84.
• Lesch, K.-P., Bengel, D., Heils, A., et al (1996)
  Association of anxiety-related traits with a
  polymorphism in the serotonin transporter gene
  regulatory region. Science, 274, 1527-1531.

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Consistency

• However, these associations are prone to false
  positives
• Need replication
• Also look to the body of evidence -
  psychopharmacology

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Psychophysiology

• Link personality traits to neural systems
• Brain structures
• Neurotransmitters
• Hormones
• Behavioural functions of key systems

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Extraversion and Psychophysiology

• Psychophysiological measures
• EEG. Technique of recording the electrical
  activity of the brain through the skull
• ERP Brain response linked to an event.
• Skin conductance indicator of autonomic activity
  of arousal.
• Heart rate, and increase in response to stress
  linked to Anxiety.
• Brain imaging

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Theory - EEG

• Eysenck proposed that introversion/extraversion
  differences are based on levels of activity of
  the cortico-reticular loop
• Introverts have higher levels of activity than
  extraverts
• EEG is one method by which this can be tested

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Interpretation of EEG

• EEG reading involves the interpretation of wave
  forms
• Frequency
• Morphology
• EEG can be split into different frequency bands.
  The most commonly used in EEG spectral analysis
  these
• Delta 0.53 - 4.22 Hz
• Theta 4.4 - 7.9 Hz
• Alpha 8.1 - 13.01 Hz
• Beta1 13.2 - 17.9 Hz
• Beta2 18.1 - 29.9 Hz

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Expectation - EEG

• What do we expect?
• Theory states that Introverts have higher levels
  of activity than extraverts
• So from the theory what differences would you
  expect?

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Evidence - EEG

• Weak positive correlations between Extraversion
  and slow-wave activity
• At moderate arousal levels introverts exhibit
  faster wave activity than extraverts

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Issues with Arousal and Personality

• The level of arousal of the testing situation is
  crucial
• Introverts and extraverts may react differently
• Need to test across different environments
• Has great face validity but results are weak and
  at times difficult to interpret

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Neurotransmitters and personality

• Dopamine and Extraversion (Depue et al)
• Dopamine and Novelty Seeking Cloninger
• Neuroticism and Serotonin
• Neuroticism and mood
• Neuroticism and depression
• SSRIs and personality
• - personality as a predictor of treatment
• - antidepressants in healthy volunteers
• Serotonin and other Traits

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Neurochemistry, personality and animal behaviour

• Researchers have attempted to find correlates of
  human behaviour in animal behaviour
• What aspects of human behaviour do you think
  could be paralleled in animal behaviour?
• What are the problems?

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Extraversion and Novelty Seeking

• Cloninger proposes that Novelty Seeking is the
  heritable tendency toward intense exhilaration
• The individual will explore actively in pursuit
  of potential rewards
• Will actively avoid monotonous behaviour or
  punishment
• Extraversion also avoid monotonous tasks and
  are sensitive to signals of reward
• Depue and Collins (1999) characterise
  Extraversion as having two central
  characteristics
• Interpersonal engagement
• Impulsivity

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Extraversion, Novelty Seeking and Dopamine

• Cloninger (1987) proposed that dopamine is the
  major neuromodulator of Novelty Seeking
• From dopamines role in exploratory behaviour in
  animals
• Role in stimulation of euphoria in humans
• A similar argument would be equally justified for
  Extraversion

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Extraversion, Novelty Seeking and Dopamine II

• Research in this area has been based on reward
  mechanisms and has stemmed from animal research.
• Typically this involves assessing the
  self-administration of drugs during different
  circumstances.

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Open field maze
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Summary of Evidence for Biological Basis of
Extraversion

• Electrophysiological
• Small effects
• Interaction between traits and testing
  environment
• Neurochemical
• To date have relied too heavily on work with
  animals
• Need more work on humans
• Genetic
• Twin studies have identified a genetic component
• Molecular genetic techniques have suggested
  various alleles however there needs to be
  replication and consistency

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PERSONALITY ASSESSMENT
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What do you know so far?
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Personality Tests

• Four main measures
• questionnaires
• Ratings of behaviour
• objective tests
• projective tests

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Questionnaires

• Self-report questionnaires.
• Limitations
• social desirability bias.
• aquiescence
• Personality tests
• Cattells 16PF
• Eysencks EPQ.

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Questionnaires II

• Criterion-keying approach
• the criterion method of test construction.
  Items are administered to subjects and selected
  if they can discriminate a criterion group eg
  anxious group versus non-anxious group

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Advantages of Questionnaires

• Reliability internal consistency and
  test-retest reliability
• Validity
• Ease of use
• Standardisation

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Ratings

• Observers provide information about other
  peoples behaviour.
• Rate different types of behaviours.
• Raters can be trained and assess over long
  periods of time
• However, ratings usually take place over short
  time, and in one or two situations
• What might be the problem with this approach?

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Objective Tests

• Assess behaviour typically in a laboratory.
• Example
• ask participant to blow up a balloon until it
  bursts as a measure of timidity
• the extent to which people sway when standing on
  tiptoe as a measure of anxiety.
• Reaction of autonomic nervous system to stimuli
• Free from deliberate distortion.
• However, it is difficult to design suitable
  objective tests for personality that are reliable
  and valid.
• Objective tests are often used in ability testing

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Projective Tests

• Participants are given an unstructured task to
  perform
• devising a story to fit a picture
• describing what can be seen in an ink blot.
• Rorschach Inkblot Test.
• The Thematic Apperception Test

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Projective Tests

• Richness of data
• Uniqueness
• Theory? individuals project their inner
  conflicts and anxieties on to the stimuli
• However this is not psychoanalytical projection
• Difficult to interpret
• Difficult to replicate
• Responses may be affected by the context
• Valid?

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A Stimulus from the Rorschach Inkblot Test
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Holtzman Inkblot Test

• Subjects choose a response to each card
• More standardised approach
• Scoring is more reliable
• There is a parallel form can achieve a test
  retest coefficient
• Valid?

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Thematic Apperception Test

• Murray (1938)
• Cards which portray people in ambiguous
  situations
• Expressions and feelings of people are also
  ambiguous
• Stimulate stories or descriptions about
  relationships or social situations
• Motivations, drives, conflicts

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Repertory Grid Technique

• Element - an individual within their life eg
  brother, mother, partner
• Psychological way in which elements differ from
  each other not physical features or background
• How are each of the elements construed? rate
  the elements on a five point scale

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Example of a repertory grid
Father Mother Self
Mean 1 4 5 Generous
Happy 4 5 1 Miserable
Lively 5 4 2 Quiet
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The analysis of repertory grids

• Possibilities are endless
• Eyeballing give a general picture
• Most analysis
• Patterns of similarities between the constructs
• Similarities between the elements

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Questions?

• Model is very descriptive
• Difficult to test how can we assess whether or
  not individuals are forming constructs
• How can we make sense of someone elses
  constructs?
• What do they mean?

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Q-Sort

• Can be used to assess the self concept, the
  impact of person-centred therapy, explore a
  particular issue.
• The items or statements can be made up by a
  sensitive clinician, they can be from a standard
  personality questionnaire but the tendency is to
  use a standard set of items (the California
  Q-set) to cover most of the standard feelings
  about the self.
• Items are self-referent statements e.g I usually
  like people, I dont trust my emotions, I am
  afraid of what other people may think of me.

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Next Week

• Personality Disorders