PSYC 2740 Lecture Notes - Barnum Effect, Test Validity, Differential Psychology
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January 23, 2013
Theoretical & Measurement Issues in Trait Psychology
1) Meaningful individual differences: traits describe how people meaningfully
differ from one another. Using the taxonomies (particularly the Big Five), you
can either have very little of a trait or a lot of a trait. There is tremendous
variability from person to person. In psychology, because trait psychologists
are so interested in scoring trait differences, trait psychology can
occasionally be referred to as “differential psychology”.
2) Stability over time: when we say that traits are relatively enduring, we are
referring to the fact that on average, we can be characterized by these traits.
3) Consistency across situations.
Stability over time
Traits are consistent over time. However, if we were to look at introversion, it may
not appear to be the same over a lifetime. Therefore, a manifestation of a trait may
vary over time.
How is there consistency if a trait is known to change with age?
Some traits do change with age; some traits will go up or down with age. We know
they’re consistent because of something called rank order: with a change in a given
trait, a relative difference remains between individuals.
Rank Order example: Impulsivity
In this example, someone who rates high in impulsivity in adolescence may show a
decrease in this trait as they age. However, somebody who scored low in impulsivity
will also show a decrease in this trait as they age. Therefore, in comparison, the
person with higher impulsivity will continue to demonstrate higher levels of
impulsivity than others, hence the trait is consistent over time.
Consistency across situations:
Traits very often affect our behavior, however, it is not the only factor. The situation
(situationalism) or context also has an effect on how we behave. It has been found
that it is the interaction between the trait and situation that causes behavior.
Strong situation: refers to a situation in which almost all people will react similarly.
Situational Specificity: specific reaction to a specific situation. This is where the
interplay between trait and situation comes into play. For example, someone may be
very laid-back for the most part, but when suddenly faced with an exam two days
away, may find themselves very anxious.
Selection: people with specific traits will select activities or situations that
emphasize these traits.
Evocation: how we act or what we say also evokes certain situations. Therefore, it
can be said that our personality also attracts certain kinds of situations and
Manipulation: different people will try to manipulate other people for a variety of
reasons. Sometimes it’s not for noble purposes; occasionally people will manipulate
others to meet their own needs. However, this does not mean that manipulation is
not always a bad thing. For example, parents may manipulate their children to keep
them from engaging in risky or life-threatening behaviours.
Consistency Across Situations: Aggregation (an example)
Aggregation takes a measure (or an average) of how often a specific trait occurs
over time. Aggregation, in other words, is the average tendency, which is why
personality is referred to as an average tendency.
Some people may be misreading the question, or may only be skimming the true
nature of the question, and therefore their response will not be indicative of their
Researchers have tried to identify two key ways in which we can determine whether
people are answering truly.
Infrequency scales: questions where all participants will answer the same. If the
person is truly not paying attention to the questions, they may answer this the
Duplicate questions: ask the same question in different ways, and compare their
responses to see if they’re giving the same answers for the same questions.
2) Faking on questionnaires
There are many different reasons why people may fake their answers on a
questionnaire. One reason may be that they want to appear good (or will answer
according to how they think you want them to). Other people may try to make
themselves look worse, or not well-adjusted. One way to deal with this is to give
them a survey beforehand as a warning of how they may try to present themselves.
Limitations of this approach: false negative (somebody is telling the truth, but you
believe they are lying so you discount their data); and false positive (somebody is
lying, but you believe they are telling the truth so you include their data).
These statements pertain to test interpretation. These are generalities that apply to
Personality in Employment
Personality is used to predict:
1) Personnel Selection: only people who have appropriate training or traits that
align with the job description will often be chosen
2) Integrity Testing: often times you don’t want someone who is dishonest or
antisocial, and many times jobs require people to have good people skills, so
you can test for this.
3) Concerns about Negligent Hiring: you don’t want to hire someone who could
harm your employees or clients.
Balancing Issues in Employment
There are sex & racial norms that must be considered. For example, some tests may
not take culture into account. Also, there must be a good rationale for using the test.
People do have a right to privacy, and it is illegal to partake in disability
discrimination. Employers need to also look at the test validity and reliability.
Theoretical issues: meaningful individual differences: traits describe how people meaningfully differ from one another. Using the taxonomies (particularly the big five), you can either have very little of a trait or a lot of a trait. There is tremendous variability from person to person. However, if we were to look at introversion, it may not appear to be the same over a lifetime. Therefore, a manifestation of a trait may vary over time. Some traits do change with age; some traits will go up or down with age. We know they"re consistent because of something called rank order: with a change in a given trait, a relative difference remains between individuals. In this example, someone who rates high in impulsivity in adolescence may show a decrease in this trait as they age. However, somebody who scored low in impulsivity will also show a decrease in this trait as they age.