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 non- redundant.

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.