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.

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.

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.

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.

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.

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 test’s scores with scores on existing measures.