Illusory correlation: why two events happening close together make the brain think one causes the other

What is illusory correlation?

Illusory correlation is a psychological phenomenon in which a person perceives a relationship between two variables, usually people, events or behaviours, even when no such relationship actually exists. This mistaken connection can form because rare or novel occurrences stand out more, and therefore draw the observer's attention more than everyday occurrences do.

The term was coined by Loren Chapman in 1967, originally to describe people's tendency to overestimate the relationship between two groups when presented with distinctive and unusual information. The concept has also been used to question objectivity in clinical psychological diagnosis, through Chapman and Chapman's rejection of many of the Wheeler signs that clinicians of the time widely used to identify homosexuality on the Rorschach test.

Why does the brain create illusory correlations?

Most explanations for illusory correlation involve psychological heuristics, that is, the information-processing shortcuts that underlie many human judgements. One of these is availability: how easily an idea comes to mind. Availability is often used to estimate the likelihood or frequency of an event. This can lead to illusory correlation, because certain pairs of events can come to memory easily and vividly, even though they do not occur frequently at all.

Martin Hilbert (2012) proposed an information-processing mechanism, assuming that the transformation from objective observation to subjective judgement always involves noise. He defined noise as the blending of observations during retrieval from memory. Under this model, the subjective perceptions or judgements beneath are identical to the noise or the objective observations, which can lead to overconfidence or conservative bias: when asked about behaviour, participants underrate the majority or larger group and overrate the minority or smaller group. These results are precisely illusory correlation.

The role of working memory

In an experimental study by Eder, Fiedler and Hamm-Eder (2011), the influence of working memory capacity on illusory correlation was examined. First, they looked at individual differences in working memory, then tested whether this affected the formation of illusory correlation. They found that individuals with higher working memory capacity viewed minority group members more positively than those with lower working memory capacity. In the second experiment, the authors investigated the influence of memory load in working memory on illusory correlation. They found that increased memory load in working memory led to an increase in the prevalence of illusory correlation. The experiment was designed specifically to test working memory rather than significant stimulus memory, meaning that the development of illusory correlation is caused by a shortage of central cognitive resources brought about by working memory load, not by selective retrieval.

What was the Hamilton and Gifford experiment of 1976?

David Hamilton and Robert Gifford (1976) conducted a series of experiments demonstrating how stereotyped beliefs about minority groups can arise from the process of illusory correlation. To test their hypothesis, Hamilton and Gifford had participants read a series of sentences describing desirable or undesirable behaviours, assigned to Group A (the majority group) or Group B (the minority group). Abstract groups were used so that no pre-existing stereotypes would influence the results. Most of the sentences were attached to Group A, the rest to Group B.

Each group had the same proportion of positive and negative behaviours, so there was no real connection between behaviour and group membership. The study's results showed that positive, desirable behaviours were not perceived as distinctive, so participants judged the relationship accurately. By contrast, when undesirable behaviours, which are distinctive, appeared in the sentences, participants overestimated the extent to which the minority group displayed those behaviours.

A parallel effect occurs when people assess whether two events, such as pain and bad weather, correlate with each other. They rely heavily on the relatively small number of instances in which the two events occurred together. People pay relatively little attention to the other categories of observation, for example no pain or good weather.

How is illusory correlation related to prejudice?

Illusory correlation is one of the ways prejudice is formed and maintained. Hamilton and Rose (1980) found that prejudice can lead people to expect that certain groups and certain characteristics go together, and then to overestimate the frequency with which they co-occur. These prejudices can be learned and passed on without any actual contact taking place between the person holding the prejudice and the group it is directed at.

The attention theory of learning holds that the characteristics of the majority group are learned first, and only then those of the minority group. This leads to an effort to distinguish the minority group from the majority group, which makes these differences learned faster. Attention theory also argues that instead of forming a single stereotype about the minority group, two stereotypes are formed: one for the majority group and one for the minority group.

When does illusory correlation form?

Johnston and Jacobs (2003) ran two experiments with second-grade and fifth-grade students to see how early in life illusory correlation forms. Children in the second and fifth grades were exposed to a typical illusory correlation model to see whether negative attributes became attached to the minority group. The authors found that both groups formed illusory correlation.

Another study also found that children produce illusory correlation. In their experiment, children in grades 1, 3, 5 and 7, as well as adults, all viewed the same illusory correlation model. The study found that children did produce significant illusory correlation, but these correlations were weaker than in adults. In a second study, groups of shapes with different colours were used. The formation of illusory correlation still continued, showing that social stimuli are not necessary to produce these correlations.

How do explicit and implicit attitudes differ?

Two studies by Ratliff and Nosek examined whether explicit and implicit attitudes influence illusory correlation. In one study, Ratliff and Nosek had two groups: a majority group and a minority group. They then had three groups of participants, all of whom read about these two groups. One group of participants received readings favouring the majority group overwhelmingly, one group received readings favouring the minority group, and one group received neutral readings. The groups that received readings favouring the majority and the minority groups both favoured their respective group both explicitly and implicitly. The group that received neutral readings favoured the majority group explicitly, but did not favour it implicitly. The second study was similar, but instead of readings, images of behaviours were presented, and participants wrote a sentence describing the behaviour they saw in the images presented. The findings of both studies supported the authors' argument that the difference between explicit and implicit attitudes is the result of interpreting covariation and making judgements based on those interpretations (explicit), rather than simply registering the covariation (implicit).

Can the structure of the experimental model itself create illusory correlation?

Berndsen and colleagues (1999) wanted to determine whether the structure of testing for illusory correlation could itself lead to the formation of illusory correlation. The hypothesis put forward was that identifying the test variables as Group A and Group B could lead participants to look for differences between the groups, leading to the creation of illusory correlation. An experiment was set up in which one group of participants was told the groups were Group A and Group B, while another group was labelled as 1993 or 1994 graduates. This study found that illusory correlation was more likely to be created when the groups were called Group A and B, compared with students of the class of 1993 or the class of 1994.

Does learning reduce illusory correlation?

Some studies suggest that illusory correlation can be reduced when people understand the conditions that make them prone to misperceiving a connection, but the evidence on the effectiveness of education remains thin.

What is apophenia and its connection to illusory correlation?

Apophenia is the tendency to perceive meaningful connections between things that are unrelated. The term (German: Apophänie, from the Greek verb ἀποφαίνειν) was coined by the psychiatrist Klaus Conrad in his 1958 work on the onset phase of schizophrenia. He defined it as "the seeing of unmotivated connections, accompanied by a special feeling of abnormal meaningfulness". He described the early stages of delusional thinking as excessive self-referential interpretations of actual sensory perceptions, as opposed to hallucinations.

Apophenia can be regarded as an ordinary effect of brain function. However, when pushed to an extreme, it can be a symptom of psychiatric disorder, for example in paranoid schizophrenia, when patients see hostile patterns (such as a plot to harm them) in ordinary actions. Apophenia is also typical of conspiracy theories, where coincidences can be woven into a clear conspiracy.

What is pareidolia?

Pareidolia is a type of apophenia involving the perception of images or sounds in random stimuli. A common example is seeing a face in an inanimate object: the headlights and grille of a car can appear to be "smiling". People all over the world see the "Man in the Moon". Sometimes people see the face of a religious figure in a slice of toast or in wood grain. There is strong evidence that hallucinogenic drugs tend to cause or enhance pareidolia. Pareidolia usually occurs because the fusiform face area, the part of the brain responsible for seeing faces, misinterprets an object, shape or configuration that has some "face-like" features as a face.

How is gambling related to illusory correlation?

Gamblers may imagine that they see patterns in the numbers that come up in lotteries, card games or roulette wheels, where no such patterns exist. A common example of this is the gambler's fallacy.

Does statistics cause illusory correlation?

In statistics, apophenia is an example of a type I error, that is, falsely identifying patterns in data. It can be compared with what are called false positives in other testing situations.

What is the clustering illusion?

The clustering illusion is a type of cognitive bias in which a person sees a pattern in a sequence of random numbers or events. Many theories have been rejected because this bias was highlighted. One case investigated in 2006 and 2007 was a cluster of breast cancer cases among female staff at the ABC broadcasting site in Toowong, Brisbane (Queensland), with 10 cases between 1994 and 2006. One study found that the rate of breast cancer at these studios was six times higher than in the rest of Queensland. An investigation found no correlation between the elevated incidence rate and any factor related to the location, nor any genetic or lifestyle factor among the staff.

What are the pattern recognition models and the causes of apophenia?

Although no confirmed reason exists for why apophenia occurs, there are several respected theories. Pattern recognition is a cognitive process involving the retrieval of information from long-term, short-term or working memory and matching it with information from stimuli. There are three different ways this can happen and go wrong, leading to apophenia.

What is template matching?

The stimulus is compared with templates, that is, abstract representations or partial representations of previously seen stimuli. These templates are stored in long-term memory as a result of learning or past educational experience. For example, D, d, D, d, D and d are all recognised as the same letter. The processes of template matching, when applied to more complex data sets (such as a painting or data clusters), can lead to mismatching of templates. A false positive finding will lead to apophenia.

What is prototype matching?

This is similar to template matching, except that prototypes are complete representations of a stimulus. A prototype is not necessarily something that has been seen before, for example, it could be an average or blend of previous stimuli. What matters is that an exact match is not required. An example of prototype matching is that when looking at an animal such as a tiger, instead of recognising that it has features matching the definition of a tiger (template matching), we recognise that it resembles a specific mental image of a tiger (prototype matching). This type of pattern recognition can lead to apophenia because the brain is not looking for an exact match; it can seize on some features of a match and assume that it fits.

What is feature analysis?

The stimulus is first broken down into its features and then processed. This pattern recognition model holds that processing goes through four stages: detection, pattern dissection, comparison of features in memory and recognition.

What is the evolutionary perspective on illusory correlation?

One of the explanations offered by evolutionary psychologists for apophenia is that it is not a defect in the cognition of the human brain but something that emerged over many years of evolution. This field of study is called error management theory, associated with the names of Haselton and Buss (2000). An experiment often cited when discussing how animals learn behaviours that do not actually produce results is Skinner's (1948) experiment with pigeons. This experiment placed a hungry pigeon in a box and released food at regular 15-second intervals, regardless of what the bird was doing. The pigeon received a pellet of food while performing some action, and instead of attributing the arrival of the pellet to chance, the pigeon repeated that action and kept doing so until another pellet dropped. As the pigeon increased the number of times it performed the action, it gained the impression that it was also increasing the number of times it was "rewarded" with a pellet, although the release of food in fact had nothing to do with its behaviour.

What are the practical applications and how can illusory correlation be reduced?

Illusory correlation and apophenia can affect many areas of life, from medical diagnosis and financial decision-making to how people are judged at work and in social life. When a person believes that two events have a causal connection simply because they occurred close together in time, they may make decisions based on mistaken evidence.

Some studies suggest that illusory correlation can be reduced when people understand the conditions that make them prone to misperceiving a connection, but the evidence on the effectiveness of education remains thin. This suggests that awareness of the bias is the first step towards reducing its influence. Beyond that, collecting complete data and testing it statistically with care can help distinguish between a real correlation and a correlation that exists only in perception.

What different viewpoints exist on illusory correlation?

It should be noted that in psychology there are many different approaches to explaining illusory correlation. Some researchers emphasise the role of availability and information-processing heuristics, while others focus on the mechanism of noise in information processing or on working memory capacity. These theories are not mutually exclusive but complementary, each highlighting a different aspect of this complex phenomenon. This article presents the main viewpoints based on the available reference sources, and readers should consult a range of different materials for a comprehensive view.