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Personality 1: Trait Theories and Measurement

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Personality 1: Trait Theories and Measurement Jos e L. Jarry, Ph.D., C.Psych. Introduction to Psychology Department of Psychology University of Toronto – PowerPoint PPT presentation

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Title: Personality 1: Trait Theories and Measurement


1
Personality 1 Trait Theories and Measurement
  • Josée L. Jarry, Ph.D., C.Psych.
  • Introduction to Psychology
  • Department of Psychology
  • University of Toronto
  • July 21, 2003

2
Personality Definition
  • Refers to the person's general style of
    interaction with the world
  • People differ from one another in their style of
    behaviour, in ways that are at least relatively
    consistent across time and situations
  • The study of personality focuses on differences
    between people.

3
Traits
  • The most central concept in personality
    psychology
  • Relatively stable predisposition to behave in a
    certain way
  • Part of the person, not part of the environment
  • The actual manifestation of traits in the form of
    behaviour usually requires some perceived cue or
    trigger in the environment.

4
Traits and States
  • States of motivation and emotions are, like
    traits, defined as inner entities that can be
    inferred from observed behaviour
  • However traits are enduring, states are temporary
  • A trait might be defined as an enduring attribute
    that describes one's likelihood of entering
    temporarily into a particular state.

5
Trait Theories
  • The goal of trait theories is to specify a
    manageable set of distinct personality dimensions
    that can be used to summarize the fundamental
    psychological differences among individuals
  • Traits are not explanations of individual
    differences
  • Traits are inferred from behaviour.

6
Hierarchical Organization of Traits
  • Behaviours and traits are linked to one another
    in a hierarchical fashion
  • Specific behaviours are at the bottom of the
    hierarchy
  • Surface traits are linked directly to a set of
    related behaviours
  • Central traits link related surface traits to one
    another
  • Central traits are the fundamental dimensions of
    personality.

7
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8
Elements of Trait Theories
  • The set of central traits that is deemed most
    useful for describing the psychological
    differences among individuals
  • The surface traits that are linked to each
    central traits
  • Objective means of measuring the surface and
    central traits
  • Usually involves a questionnaire, in which the
    person describes his or her own behaviour.

9
Building a Trait Theory (1)
  • Bottom up process
  • collect a large amount of data about the specific
    behaviours of a large number of people
  • statistical means to determine which classes of
    behaviours correlate most strongly with one
    another, indicating surface traits
  • and which surface traits correlate most strongly
    with one another, indicating central traits
  • generate a hierarchical set of proposed traits
    and give them names.

10
Building a Trait Theory (2)
  • develop a questionnaire that can be used reliably
    to measure the degree to which any given person
    manifests each of the traits specified by the
    theory
  • the primary goal of any trait theory is to
    account for the greatest amount of variation
    among individuals, while minimizing the number of
    separate central-trait dimensions used
  • In the ideal theory, the central traits are
    non-redundant.

11
Cattell's 16 PF (1)
  • Raymond Cattell (1950)
  • began his research by condensing 18,000 English
    adjectives describing personality, down to about
    170 that are logically different from one another
  • these were his initial set of surface traits
  • large numbers of people rated themselves on each
    of the surface traits
  • used factor analysis to determine which surface
    traits correlated most with one another.

12
Cattell's 16 PF (2)
  • identified a preliminary set of central traits by
    finding clusters of surface traits that
    correlated strongly with one another within the
    clusters but not across the clusters
  • developed various questionnaires aimed at
    assessing these traits
  • used the questionnaire results to modify the set
    of central traits
  • identified 16 central traits
  • developed a questionnaire called the 16 PF
    Questionnaire to measure them.

13
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14
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15
The Eysenck Personality Inventory
  • Hans Eysenck (1952)
  • Introversion-extroversion
  • is related to the person's tendency to avoid or
    seek excitement in the external environment
  • Neuroticism-stability
  • pertains to one's tendency to become emotionally
    upset
  • Psychoticism-nonpsychoticism
  • pertains to a lack of concern for others vs.
    peaceableness and empathy.

16
The Big-Five Theory
  • Cattell's 16 factor theory is overly complex,
    with redundant factors
  • Eysenck's three-dimensional theory is
    oversimplified
  • Researchers conducting factor analytic studies in
    various country, in several languages, find
    consistent results
  • The most efficient set of central traits for
    describing personality consists of 5 traits.

17
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18
Predictive Value of Traits
  • Are personality traits consistent across
    situations or are they specific to particular
    situations?
  • Are personality traits stable through time?

19
The Stability of Personality Measures Over Time
  • Studies in which people rate themselves or are
    rated by others on personality questionnaires
  • At widely separated times in their lives
  • The results indicate high stability of
    personality throughout adulthood
  • Correlation coefficients on repeated measures of
    the Big Five typically range from .50 to .70
  • Even with time spans between the first and second
    test of 30 or 40 years.

20
Consistency Across Situations (1)
  • Walter Mischel (1968, 1984)
  • describing personality in situations specific
    terms is more useful in predicting behaviour than
    are global traits statements
  • Social learning approach
  • personality characteristics are learned habits of
    thinking and behaving, which are acquired and
    manifested in particular social situations.

21
Consistency Across Situations (2)
  • Hugh Hartshorne and Mark May (1928)
  • conducted a classic study of morality involving
    thousands of schoolchildren
  • children were provided with opportunities to be
    dishonest in a wide variety of situations
  • the results showed high correlations within any
    given type of situation,
  • but low correlations across different situations.

22
Consistency Across Situations (3)
  • Mischel and Peake (1982)
  • assessed repeatedly by direct observation 19
    different forms of behaviour presumed to be
    related to the trait of conscientiousness
  • they found high consistency within any one of
    these measures,
  • but relatively low consistency across measures.

23
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24
Reanalysis of the Mischel Peake Study
  • Factor analysis showed that the measures
    clustered in separate traits
  • Within these traits, there was high correlation
    across situations,
  • but not necessarily between the traits
  • The lack of correlations between behaviours
    supposed to measure conscientiousness meant that
    these behaviours clustered in different traits
    rather than in one global trait.

25
Reanalysis of the Hartshorne May Study
  • Little consistency was found when the behaviours
    related to dishonesty were measured within one
    individual, between situations
  • When comparisons were made between children,
    averaging situations within individuals,
  • Large differences existed between individuals,
    larger than would be accounted for by chance.

26
Biological Foundations of Traits
  • Eysenck
  • proposed that individual differences in
    extroversion-introversion stem from differences
    in how easily the higher parts of the brain are
    aroused by sensory input
  • all people seek an optimal level of brain arousal
  • but to achieve that level, extroverts require
    more stimulation than do introverts
  • introverts avoid stimulating environments to
    prevent their arousal level from exceeding the
    optimum.

27
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28
The Heritability of Traits
  • Twin studies
  • standard personality questionnaires are
    administered to identical and fraternal twins
  • identical twins are much more similar than are
    fraternal twins raised together on every
    personality dimension measured
  • same results are found for twins raised apart
  • even trait that logically should be influenced by
    learning are found to be heritable.

29
Reliability (1)
  • Refers to the stability of the scores
  • Does the test measure consistently what it is
    supposed to measure?
  • The capacity of the test to yield the same or
    comparable scores on different testing occasions
    on a given population
  • Measured with the Reliability Coefficient.

30
Reliability (1)
  • Test-retest reliability
  • assesses the stability of the scores over time
  • administer the same test to the same population
    twice
  • Parallel-form reliability
  • administer similar forms of the test to the same
    population twice
  • Split-half reliability
  • measure of internal consistency
  • administer the test once
  • split the items in two and perform a correlation.

31
Validity (1)
  • Refers to the meaning of the scores
  • Does the test measure what it is supposed to
    measure?
  • Measured with a validity coefficient.

32
Validity (2)
  • Predictive or criterion validity
  • consists of comparing the performance of the test
    with a real world measure of the trait
  • Construct validity
  • related to the theory underlying the test
  • does the test measure the theoretical construct
    it is supposed to measure?
  • can be done by deriving a network of predictions
    from the theory
  • can be done by correlating the new tests scores
    with scores on existing measures.
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