Illusory Correlation

What Is Illusory Correlation?

Sometimes we see uncorrelated events as correlated because we tend to see the world in line with our expectations, which often lead us to see a correlation between two events when in reality no such association exists—a phenomenon called illusory correlation.

Illusory correlation refers to an erroneous inference about the relationship between two categories of events. It involves the tendency to see a correlation between two events when in reality, no such association exists (Hamilton & Gifford, 1976).

For example, athletes often believe that they perform better when they follow some ritual. Basketball legend Michael Jordan wore his college shorts under his professional uniform. Would an objective test of his superstitious behavior have shown that he would have performed just as well without the college shorts? Psychologists suspect so.

Loren Chapman (1967) introduced the concept of illusory correlation to refer to “the report by observers of a correlation between two classes of events which, in reality, (a) are not correlated, or (b) are correlated to a lesser extent than reported” (p.151).

In a test to demonstrate the role of expectancies in illusory correlations, Loren Chapman (1967) asked participants to read a series of word pairs (bacon–notebook, blossoms–tiger, etc.), which were presented several times. Some of the word pairs consisted of commonly associated words, such as bacon-eggs and lion-tiger, whereas other pairs combined unrelated words, such as bacon-tiger and lion-eggs.

The commonly associated words pairs (the expected pairings) were not presented any more often than the unrelated word pairs. When subjects were asked to estimate the frequency of various word pairings, however, they overestimated the frequency of the expected pairings. For example, they tended to overestimate the frequency with which bacon and eggs or lion and tiger had been paired in the trials.

Chapman suggested that these illusory correlations occurred because the expected pairings were more likely to be noticed and thus were easier to retrieve from memory.

Seeing What We Expect to See

Why or when do illusory correlations occur? As noted by Chapman (1967), people are especially likely to notice events that confirm their expectancies, which leads them to overestimate the frequency of such confirmation. People tend to see what they expect to see.

For example, some individuals who believe in astrology might read their daily horoscope every morning. Chapman would suggest that if something happens that is congruent with the individual’s horoscope for that day, s/he is more likely to notice than if nothing happens to confirm the horoscope. Therefore, those days when something confirmatory happened will be recalled better than those days when nothing happened, and the person will overestimate the accuracy of the horoscopes.

Another factor that contributes to this error is our tendency to see two relatively rare attributes as associated, even if we have no expectation that these things should go together (Johnson & Mullen, 1994).

A correlation exists when two variables are associated with one another, such as height and weight or class attendance and exam performance. Correlations do not necessarily reflect cause, although causal relations between the variables may sometimes account for some or all of the correlation (e.g., class attendance definitely improves exam performance).