Clustering Illusion
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The clustering illusion is the tendency to erroneously consider the inevitable "streaks" or "clusters" arising in small samples from random distributions to be non-random. The illusion is caused by a human tendency to underpredict the amount of variability likely to appear in a small sample of random or pseudorandom data.


Examples

Thomas Gilovich Thomas Dashiff Gilovich (born January 16, 1954) an American psychologist who is the Irene Blecker Rosenfeld Professor of Psychology at Cornell University. He has conducted research in social psychology, decision making, behavioral economics, an ...
, an early author on the subject, argued that the effect occurs for different types of random dispersions, including two-dimensional data such as clusters in the locations of impact of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
V-1 flying bombs on maps of London; or seeing patterns in stock market price fluctuations over time. Although Londoners developed specific theories about the pattern of impacts within London, a statistical analysis by R. D. Clarke originally published in 1946 showed that the impacts of
V-2 rocket The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develop ...
s on London were a close fit to a random distribution.


Similar biases

Using this cognitive bias in causal reasoning may result in the Texas sharpshooter fallacy, in which when differences in data are ignored and similarities are overemphasized. More general forms of erroneous pattern recognition are ''
pareidolia Pareidolia (; ) is the tendency for perception to impose a meaningful interpretation on a nebulous stimulus, usually visual, so that one sees an object, pattern, or meaning where there is none. Common examples are perceived images of animals, ...
'' and '' apophenia''. Related biases are the ''
illusion of control The illusion of control is the tendency for people to overestimate their ability to control events. It was named by U.S. psychologist Ellen Langer and is thought to influence gambling behavior and belief in the paranormal. Along with illusory supe ...
'' which the clustering illusion could contribute to, and ''
insensitivity to sample size Insensitivity to sample size is a cognitive bias that occurs when people judge the probability of obtaining a sample statistic without respect to the sample size. For example, in one study subjects assigned the same probability to the likelihood of ...
'' in which people don't expect greater variation in smaller samples. A different cognitive bias involving misunderstanding of chance streams is the gambler's fallacy.


Possible causes

Daniel Kahneman Daniel Kahneman (; he, דניאל כהנמן; born March 5, 1934) is an Israeli-American psychologist and economist notable for his work on the psychology of judgment and decision-making, as well as behavioral economics, for which he was award ...
and
Amos Tversky Amos Nathan Tversky ( he, עמוס טברסקי; March 16, 1937 – June 2, 1996) was an Israeli cognitive and mathematical psychologist and a key figure in the discovery of systematic human cognitive bias and handling of risk. Much of his ...
explained this kind of misprediction as being caused by the
representativeness heuristic The representativeness heuristic is used when making judgments about the probability of an event under uncertainty. It is one of a group of heuristics (simple rules governing judgment or decision-making) proposed by psychologists Amos Tversky and D ...
(which itself they also first proposed).


See also

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Apophenia Apophenia () is the tendency to perceive meaningful connections between unrelated things. The term (German: ' from the Greek verb ''ἀποφαίνειν'' (apophaínein)) was coined by psychiatrist Klaus Conrad in his 1958 publication on the ...
*
Alignments of random points Alignments of random points in a plane can be demonstrated by statistics to be counter-intuitively easy to find when a large number of random points are marked on a bounded flat surface. This has been put forward as a demonstration that ley lin ...
*
Complete spatial randomness Complete spatial randomness (CSR) describes a point process whereby point events occur within a given study area in a completely random fashion. It is synonymous with a ''homogeneous spatial Poisson process''.O. Maimon, L. Rokach, ''Data Mining and ...
*
Confirmation bias Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms or supports one's prior beliefs or values. People display this bias when they select information that supports their views, ignoring ...
*
List of cognitive biases Cognitive biases are systematic patterns of deviation from norm and/or rationality in judgment. They are often studied in psychology, sociology and behavioral economics. Although the reality of most of these biases is confirmed by reproducible ...
*
Numeracy bias Precision bias also known as numeracy bias is a form of cognitive bias in which an evaluator of information commits a logical fallacy as the result of confusing accuracy and precision. More particularly, in assessing the merits of an argument, a me ...
*
Poisson distribution In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time or space if these events occur with a known co ...
*
Statistical randomness A numeric sequence is said to be statistically random when it contains no recognizable patterns or regularities; sequences such as the results of an ideal dice roll or the digits of π exhibit statistical randomness. Statistical randomness does ...


References


External links


Skeptic's Dictionary: The clustering illusion

Hot Hand website: Statistical analysis of sports streakiness
{{Hidden messages Cognitive biases Statistical randomness Illusions Cluster analysis