Illusory correlation

Illusory correlation is the phenomenon of perceiving a relationship between variables (typically people, events, or behaviors) even when no such relationship exists. A common example of this phenomenon is the formation of a false association between membership in a statistical minority group (e.g., African-Americans) and a rare, typically negative, behavior (e.g., drug abuse). This false association is formed because rare or novel occurrences are more salient and therefore tend to capture one's attention. This is one way stereotypes form and endure.Hamilton & Rose (1980) found that stereotypes can lead people to expect certain groups and traits to fit together, and then to overestimate the frequency with which these correlations actually occur.

"Illusory correlation" was originally coined by Chapman and Chapman (1967) to describe people's tendencies to overestimate relationships between two groups when distinctive and unusual information is presented. The concept was used to question claims about objective knowledge in clinical psychology through the Chapmans' refutation of many clinicians' widely used Wheeler signs for homosexuality in Rorschach tests.

David Hamilton and Robert Gifford (1976) conducted a series of experiments that demonstrated how stereotypic beliefs regarding minorities could derive from illusory correlation processes. To test their hypothesis, Hamilton and Gifford had research participants read a series of sentences describing either desirable or undesirable behaviors, which were attributed to either Group A or Group B. Abstract groups were used so that no previously established stereotypes would influence results. Most of the sentences were associated with Group A, and the remaining few were associated with Group B. The following table summarizes the information given.

Each group had the same proportions of positive and negative behaviors, so there was no real association between behaviors and group membership. Results of the study show that positive, desirable behaviors were not seen as distinctive so people were accurate in their associations. On the other hand, when distinctive, undesirable behaviors were represented in the sentences, the participants overestimated how much the minority group exhibited the behaviors.

A parallel effect occurs when people judge whether two events, such as pain and bad weather, are correlated. They rely heavily on the relatively small number of cases where the two events occur together. People pay relatively little attention to the other kinds of observation (of no pain or good weather).

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