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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.
Thomas Gilovich, an early author on the subject, argued that the effect occurs for different types of random dispersions. Some might perceive patterns in
Skeptic's Dictionary: The clustering illusion
Hot Hand website: Statistical analysis of sports streakiness
{{Hidden messages Cognitive biases Statistical randomness Illusions Cluster analysis
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.
Thomas Gilovich, an early author on the subject, argued that the effect occurs for different types of random dispersions. Some might perceive patterns in stock market
A stock market, equity market, or share market is the aggregation of buyers and sellers of stocks (also called shares), which represent ownership claims on businesses; these may include ''securities'' listed on a public stock exchange a ...
price fluctuations over time, or clusters in two-dimensional data such as the locations of impact of World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
V-1 flying bomb
The V-1 flying bomb ( "Vengeance Weapon 1") was an early cruise missile. Its official Reich Aviation Ministry () name was Fieseler Fi 103 and its suggestive name was (hellhound). It was also known to the Allies as the buzz bomb or doodlebug a ...
s on maps of London. 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 V2 (), with the technical name ''Aggregat (rocket family), Aggregat-4'' (A4), was the world's first long-range missile guidance, guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was developed during the S ...
s on London were a close fit to a random distribution.
Similar biases
Using thiscognitive bias
A cognitive bias is a systematic pattern of deviation from norm (philosophy), norm or rationality in judgment. Individuals create their own "subjective reality" from their perception of the input. An individual's construction of reality, not the ...
in causal reasoning may result in the Texas sharpshooter fallacy, in which 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 (physiology), stimulus, usually visual, so that one detects an object, pattern, or meaning where there is none. Pareidolia is a specific bu ...
'' and '' apophenia''. Related biases are the '' illusion of control'' which the clustering illusion could contribute to, and '' insensitivity to sample size'' 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
The gambler's fallacy, also known as the Monte Carlo fallacy or the fallacy of the maturity of chances, is the belief that, if an event (whose occurrences are Independent and identically distributed random variables, independent and identically dis ...
.
Possible causes
Daniel Kahneman
Daniel Kahneman (; ; March 5, 1934 – March 27, 2024) was an Israeli-American psychologist best known for his work on the psychology of judgment and decision-making as well as behavioral economics, for which he was awarded the 2002 Nobel Memor ...
and Amos Tversky
Amos Nathan Tversky (; 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 early work concerned th ...
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 being representational in character and essence of a known prototypical event. It is one of a group of heuristics (simple rules governing judgment or ...
(which itself they also first proposed).
See also
* Apophenia * Alignments of random points * Complete spatial randomness *Confirmation bias
Confirmation bias (also confirmatory bias, myside bias, or congeniality bias) is the tendency to search for, interpret, favor and recall information in a way that confirms or supports one's prior beliefs or Value (ethics and social sciences), val ...
* List of cognitive biases
* Numeracy bias
* Poisson clumping
* Poisson distribution
* Statistical randomness
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