Transcript Personality 1: Trait Theories and Measurement

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
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.
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.
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.
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.
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.
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.
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.
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 nonredundant.
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.
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.
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.
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.
Predictive Value of Traits
• Are personality traits consistent across
situations or are they specific to particular
situations?
• Are personality traits stable through time?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Validity (1)
• Refers to the meaning of the scores
• Does the test measure what it is supposed to
measure?
• Measured with a validity coefficient.
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 test’s scores
with scores on existing measures.