1. The Moderator Approach to Personality: When Do Traits Predict Behavior Well, and When Don’t They?

2. Theoretical issues Meaningful differences between individuals
Consistency over time
Consistency across situations
Person-situation interaction
Aggregation
Other stable dispositions
Cognitive abilities, attitudes, beliefs, and values, sexual orientation
Is personality real?

3. Assumption 1: There are meaningful differences between individuals
There are meaningful differences between individuals (traits psychology is also called differential psychology)
According to trait psychologists, every person can be characterized in terms of his or her relative standing on a set of human trait dimensions
People differ in their relative position (standing) on various trait dimensions, and these differences can be accurately measured

4. Assumption 2: Personality results in consistency over time
Research indicates consistency over time for broad traits, particularly temperament-relevant traits with high heritabilities
Although the trait itself is assumed to be fairly 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

5. Situations and dispositions both affect behavior Example: the number of smiles in two different situations
Participant
Party
Funeral
Sue 84 17
Eddie 65 15
Carlos 51 11
Anna 46 8
Linda 40 6
John 33 4
Mary 27 3
Frank 22

6. Assumption 3: Personality results in consistency across situations
Trait psychologists traditionally assumed cross-situational consistency
If situations mainly control how people behave, then the existence or relevance of traits is questionable
Hartshorne and May (1928) found low cross-situational consistency in schoolchildren’s traits of honesty, helpfulness, and self-control (average “inter-item” correlation of .20)

7. The situation versus trait controversy: Walter Mischel’s criticisms of the trait approach
Trait measures do not predict relevant behavioral measures well (the presumed .30 to .40 upper range of trait-based prediction).
There is little evidence for cross-situational consistency. Behavior reveals more situational specificity than most trait theorists suggest.
The predictive validity of trait measures does not justify their use in making important decisions about people (e.g., diagnosis and hiring decisions).

8. Consistency across situations
Trait psychologists traditionally assumed cross-situational consistency
If situations mainly control how people behave, then the existence or relevance of traits is questionable
Hartshorne and May (1928) found low cross-situational consistency in schoolchildren’s traits of honesty, helpfulness, and self-control
25 years later, Rushton, Brainerd, and Pressley (1983) noted that Hartshorne and May had also calculated each child’s average level of altruism within each of two sets of situations in which altruism was tested. They found that these two averages correlated over .50, illustrating the value of using aggregated measures of the behavior criteria.

9. Mischel’s (1968) pessimistic conclusions
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

10. Three categories of moderating variables in personality research (Snyder & Ickes, 1985)
Category
Function
Representative Examples
Situational moderating variables
Specify in which types of situations traits will be good versus poor predictors of their trait-relevant behaviors
Psychologically weak versus strong situations
Precipitating versus non-precipitating situations
Personal moderating variables
Specify for which types of people traits will be good versus poor predictors of their trait-relevant behaviors
Private self-consciousness
Self-monitoring
Criterion moderating variables
Specify the types of behaviors that traits will predict either well or poorly
Level of aggregation of the behavioral measure
Prototypicality of the behavioral criterion

11. Responses to Mischel’s criticisms
General traits do predict overall patterns of trait-relevant behavior fairly well. What they don’t predict well are single behaviors measured on a single occasion in a single situation.
Traits can be used to predict trait-relevant behavior in some, but not all, types of situations. In “weak” situations, traits are important in determining behavior. However, in “strong” situations, the influence of traits on behavior can be much more limited.
In general, an isolated trait accounts for about as much variance in a relevant behavior as an isolated situational variable does. The typical correlation in each case is about .20.

12. Outcome of the debate
Mischel’s (1968) critique encouraged debate in personality psychology about the importance of traits compared to situational factors in causing behavior
Both sides tempered their views: Trait psychologists acknowledged the importance of situational factors, and situationists acknowledged the importance of traits
The debate led to two lasting changes: a focus on person-situation interaction and the importance of aggregation

13. Person X situation interaction
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
Example: the situational provocation of anger
Overall, significantly more angry reactions are observed in the provocation situation than in the same situation when the provocation does not occur (effect of the situational variable).
But is personality important as well? And does personality interact with situation to predict the angry behavior?
A closer inspection of the data reveals that people at three different levels of hostility (low, moderate, and high) show three different patterns of response: high hostiles (hot heads), moderates, and lows (cool heads).

14. Aggregation
Longer tests are more reliable than shorter ones and are better measures of traits
A single behavior measured on just one occasion may be influenced by a variety of extenuating circumstances unrelated to personality

15. Aggregation
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 probably never be good at predicting single acts on single occasions