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Theoretical and measurement issues in trait psychology

Chapter Outline

Theoretical and Measurement Issues in Trait Psychology

Meaningful Differences Between Individuals

There are meaningful differences between individuals (traits psychology is also called differential psychology)

People differ in amounts of traits, and differences can be accurately measured
According to trait psychologists, every personality is the product of a combination of a few basic, primary traits

Research indicates consistency over time for broad traits
Although consistent over time, how a trait is manifested in behavior might change over time
How can there be consistency in a trait if it is known to change with age (e.g., impulsivity)? Focus on the rank order differences between people

Trait psychologists traditionally assumed cross-situation consistency
If situations mainly control how people behave, then the existence or relevance of traits questionable
Hartshorne and May (1928): Low cross-situation consistency is in honesty, helpfulness, self-control
Mischel (1968): Personality psychologists should abandon their efforts to explain behavior with traits, focusing instead on situations
Situationism: If behavior varies across situations, then situational differences and not personality traits determine behavior
Mischel's (1968) critique encouraged debate in personality psychology about the importance of traits compared to situations in causing behavior
Both sides tempered views: Trait psychologists acknowledged the importance of situation, and situationists acknowledged the importance of traits
Debate led to two lasting changes: Focus on person-situation interaction and practice of aggregation

Two possible explanations for behavior:

Behavior is a function of personality traits
Behavior is a function of situation

Integration: Personality and situation interact to produce behavior

Differences between people make a difference only under certain circumstances
Situational specificity: Certain situations can provoke behavior that is out of character for an individual
Strong situation: Situations in which most people react in a similar way (e.g., grief following loss of loved one)
When situations are weak or ambiguous, personality has its strongest influence

Three additional ways in which personality and situation interact to produce behavior

Selection: Tendency to choose or select situations in which one finds oneself, as a function of personality
Evocation: Certain personality traits may evoke specific responses from others
Manipulation: Various means by which people influence the behavior of others; tactics of manipulation vary with personality

Longer tests are more reliable than shorter ones and are better measures of traits
Single behavior or occasion may be influenced by extenuating circumstances unrelated to personality
Aggregation implies that traits are only one influence on behavior
Aggregation also implies that traits refer to the person's average level
Thus, personality psychologists will never be good at predicting single acts or single occasions

Measurement Issues

Trait approach relies on self-report surveys to measure personality
Personality psychologists assume that people differ in the amounts of various traits, and so a key measurement issue is determining how much of trait person has
Traits are often represented as dimensions along which people differ
Trait psychologists are aware of and address circumstances that affect accuracy, reliability, validity, and utility of self-report trait measures

Method for detecting such problems is an infrequency scale embedded in test
Infrequency scale contains items that most people answer in a particular way
If a participant answers differently than most, this suggests carelessness
Another method for detecting carelessness is to include duplicate items spaced far apart in the survey—if the person answers the same item differently, this suggests carelessness

"Fake goodÓ: Attempt to appear better off or better adjusted than one is
"Fake badÓ: Attempt to appear worse off or less adjusted than one is
Method to detect is to a devise scale that, if answered in particular way, suggests faking

Extreme responding: Tendency to give endpoint responses
Social desirability: Tendency to answer items in such a way so that one comes across as socially attractive or likable
Two views on social desirability:

Represents distortion and should be eliminated or reduced

Resolved by (1) measuring and statistically removing, (2) designing surveys that are less susceptible to this response set, or (3) using forced-choice format

Valid part of other desirable personality traits, such as agreeableness, and should be studied

Self-deceptive optimism versus impression management

Personality and Prediction

Whether someone does well in an employment setting may be determined, in part, by whether a person's personality traits mesh with job requirements
Personality traits may predict who is likely to do well in particular job, so it makes sense to select people for employment based on measures of traits
But using tests to select employees has limitations and potential liabilities
Lawsuits have challenged the use of tests on the grounds ranging from discrimination, to invasion of privacy, to freedom of religion
Most employers receive overall test scores, however, not the applicant's answers to specific questions
In 1978, the EEOC standardized federal guidelines for the use of tests in employment selection
Two main concerns that the employer must satisfy to use for employment selection

Test must predict performance on a specific job or jobs like the one people are being selected for
Test must not be biased or have "undue impactÓ on persons from protected groups, such as women and minorities

Personality tests frequently used to screen out "wrongÓ individuals from a pool of applicants for police officers

Most graduate schools require applicants to take the GRE, and most schools use GRE scores to some degree in deciding whom to accept into program
GRE is an aptitude test, thought to reflect intelligence or the capacity to learn
Many studies have been conducted to assess the degree to which GRE scores predict success in psychology graduate school
Meta-analyses reveal that GRE scores do predict success in graduate school, but correlations are only modest (.15 to .40)
Four arguments for why GRE scores can be useful, even though they only modestly predict success in graduate school

Even small increments in predictability above chance can be useful
Costs of failing to select the right people into graduate school can be high
GRE scores can be useful if used with appropriate criterion (i.e., what want to predict)

Criterion problem: Concerns how we define and measure the criterion we want to predict
Validity of GRE depends on which criterion used to define success in graduate school—if defined as obtaining Ph.D., GRE scores are valid predictors

Research indicates that, without range restriction, correlations between GRE scores and success in graduate school are high, ranging from .30 to .70

Range restriction affects correlation

When two variables are correlated with each other, the size of correlation depends, in part, on whether each variable spans full range in the sample
Violation occurs when participants are selected on the basis of one score, and then that score is correlated with another variable on which participants have been measured
Correlation between two variables will shrink as the range of scores on one (or both) variables is restricted

Integrity tests are surveys designed to assess whether a person is generally honest or dishonest; replaced polygraph
When assessed against the "big fiveÓ personality traits, integrity is the combination of high conscientiousness, high agreeableness, and low neuroticism
Integrity tests can be a valuable addition to other measures used in employment selection

Summary and Evaluation

Hallmark of trait perspective is the emphasis on the differences between people
Traits psychologists assume that people will be relatively constant over time and across situations in behaviors, because of their differences in various traits
Traits are more likely to influence a person's behavior when the situation is weak and ambiguous and doesn't push for conformity from all people
Personality traits refer to the average tendencies in behavior
Trait psychologists are interested in the accuracy of measurement
Interest in measurement and prediction has led trait psychologists to apply these skills to the selection or screening of job applicants and other situations where personality might make a difference

2002 McGraw-Hill Higher Education

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