Editing Representativeness heuristic (section)

==Biases attributed to the representativeness heuristic==

===Base rate neglect and base rate fallacy===
{{main|Base rate fallacy}}
The use of the representativeness heuristic will likely lead to violations of [[Bayes' Theorem]]:<ref name="DawesMirels1993">{{cite journal|last1=Dawes|first1=Robyn M.|last2=Mirels|first2=Herbert L.|last3=Gold|first3=Eric|last4=Donahue|first4=Eileen|year=1993|title=Equating inverse probabilities in implicit personality judgments|journal=Psychological Science|volume=4|issue=6|pages=396–400|doi=10.1111/j.1467-9280.1993.tb00588.x|s2cid=143928040}}</ref>
:<math>P(H|D) = \frac{P(D | H)\, P(H)}{P(D)}.</math>
<br />However, judgments by representativeness only look at the resemblance between the hypothesis and the data, thus inverse probabilities are equated:<ref name="DawesMirels1993" />

<math>P(H|D)=P(D|H)</math>

As can be seen, the [[base rate]] P(H) is ignored in this equation, leading to the [[base rate fallacy]]. A base rate is a phenomenon's basic rate of incidence. The base rate fallacy describes how people do not take the base rate of an event into account when solving probability problems.<ref name="Axelsson">{{cite journal|last1=Axelsson|first1=Stefan|title=The base-rate fallacy and the difficulty of intrusion detection|journal=ACM Transactions on Information and System Security|volume=3|issue=3|year=2000|pages=186–205|doi=10.1145/357830.357849|citeseerx=10.1.1.133.3797|s2cid=11421548}}</ref> This was explicitly tested by Dawes, Mirels, Gold and Donahue (1993) who had people judge both the base rate of people who had a particular personality trait and the probability that a person who had a given personality trait had another one. For example, participants were asked how many people out of 100 answered true to the question "I am a conscientious person" and also, given that a person answered true to this question, how many would answer true to a different personality question. They found that participants equated inverse probabilities (e.g., <math>P(conscientious|neurotic)=P(neurotic|conscientious)</math>) even when it was obvious that they were not the same (the two questions were answered immediately after each other).<ref name="DawesMirels1993" /> 

A medical example is described by Axelsson. Say a doctor performs a test that is 99% accurate, and the patient tests positive for the disease. However, the incidence of the disease is 1/10,000. The patient's actual risk of having the disease is 1%, because the population of healthy people is so much larger than the disease. This statistic often surprises people, due to the base rate fallacy, as many people do not take the basic incidence into account when judging probability.<ref name="Axelsson" /> Research by [[Maya Bar-Hillel]] (1980) suggests that perceived relevancy of information is vital to base-rate neglect: base rates are only included in judgments if they seem equally relevant to the other information.<ref name="BH80">{{cite journal|last1=Bar-Hillel|first1=Maya|author1-link=Maya Bar-Hillel|title=The base-rate fallacy in probability judgments|journal=Acta Psychologica|volume=44|issue=3|year=1980|pages=211–233|doi=10.1016/0001-6918(80)90046-3|url=http://ratio.huji.ac.il/sites/default/files/publications/dp732.pdf}}</ref>

Some research has explored base rate neglect in children, as there was a lack of understanding about how these judgment heuristics develop.<ref name="Davidson">{{cite journal|last1=Davidson|first1=Denise|year=1995|title=The representativeness heuristic and the conjunction fallacy effect in children's decision making|journal= Merrill-Palmer Quarterly|volume=41|issue=3|pages= 328–346|jstor=23087893}}</ref><ref name="Jacobs">{{cite journal|last1=Jacobs|first1=Janis E.|last2=Potenza|first2=Maria|title=The Use of Judgement Heuristics to Make Social and Object Decisions: A Developmental Perspective|journal=Child Development|volume=62|issue=1|year=1991|pages=166–178|doi=10.1111/j.1467-8624.1991.tb01522.x}}</ref> The authors of one such study wanted to understand the development of the heuristic, if it differs between social judgments and other judgments, and whether children use base rates when they are not using the representativeness heuristic. The authors found that the use of the representativeness heuristic as a strategy begins early on and is consistent. The authors also found that children use idiosyncratic strategies to make social judgments initially, and use base rates more as they get older, but the use of the representativeness heuristic in the social arena also increase as they get older. The authors found that, among the children surveyed, base rates were more readily used in judgments about objects than in social judgments.<ref name="Jacobs" /> After that research was conducted, Davidson (1995) was interested in exploring how the representativeness heuristic and conjunction fallacy in children related to children's stereotyping. Consistent with previous research, children based their responses to problems off of base rates when the problems contained nonstereotypic information or when the children were older. There was also evidence that children commit the conjunction fallacy. Finally, as students get older, they used the representativeness heuristic on stereotyped problems, and so made judgments consistent with stereotypes. There is evidence that even children use the representativeness heuristic, commit the conjunction fallacy, and disregard base rates.<ref name="Davidson" /> 

Research suggests that use or neglect of base rates can be influenced by how the problem is presented, which reminds us that the representativeness heuristic is not a "general, all purpose heuristic", but may have many contributing factors.<ref name="GigerenzerHell1988">{{cite journal|last1=Gigerenzer|first1=Gerd|last2=Hell|first2=Wolfgang|last3=Blank|first3=Hartmut|title=Presentation and content: The use of base rates as a continuous variable|journal=Journal of Experimental Psychology: Human Perception and Performance|volume=14|issue=3|year=1988|pages=513–525|doi=10.1037/0096-1523.14.3.513|citeseerx=10.1.1.318.6320}}</ref> Base rates may be neglected more often when the information presented is not causal.<ref name="Ajzen1977">{{cite journal|last1=Ajzen|first1=Icek|title=Intuitive theories of events and the effects of base-rate information on prediction|journal=Journal of Personality and Social Psychology|volume=35|issue=5|year=1977|pages=303–314|doi=10.1037/0022-3514.35.5.303}}</ref> Base rates are used less if there is relevant individuating information.<ref name="Koehler1996">{{cite journal|last1=Koehler|first1=Jonathan J.|title=The base rate fallacy reconsidered: Descriptive, normative, and methodological challenges|journal=Behavioral and Brain Sciences|volume=19|issue=1|year=1996|pages=1–17|doi=10.1017/S0140525X00041157|s2cid=53343238 }}</ref> Groups have been found to neglect base rate more than individuals do.<ref name="ArgoteSeabright1986">{{cite journal|last1=Argote|first1=Linda|author1-link= Linda Argote |last2=Seabright|first2=Mark A|last3=Dyer|first3=Linda|title=Individual versus group use of base-rate and individuating information|journal=Organizational Behavior and Human Decision Processes|volume=38|issue=1|year=1986|pages=65–75|doi=10.1016/0749-5978(86)90026-9}}</ref> Use of base rates differs based on context.<ref name="ZukierPepitone1984">{{cite journal|last1=Zukier|first1=Henri|last2=Pepitone|first2=Albert|title=Social roles and strategies in prediction: Some determinants of the use of base-rate information|journal=Journal of Personality and Social Psychology|volume=47|issue=2|year=1984|pages=349–360|doi=10.1037/0022-3514.47.2.349}}</ref> Research on use of base rates has been inconsistent, with some authors suggesting a new model is necessary.<ref name="MedinEdelson1988">{{cite journal|last1=Medin|first1=Douglas L.|last2=Edelson|first2=Stephen M.|title=Problem structure and the use of base-rate information from experience|journal=Journal of Experimental Psychology: General|volume=117|issue=1|year=1988|pages=68–85|doi=10.1037/0096-3445.117.1.68|pmid=2966231 }}</ref>

===Conjunction fallacy===
{{main|Conjunction fallacy}}
A group of undergraduates were provided with a description of Linda, modelled to be representative of an active feminist. Then participants were then asked to evaluate the probability of her being a feminist, the probability of her being a bank teller, or the probability of being both a bank teller and feminist. Probability theory dictates that the probability of being both a bank teller and feminist (the [[Logical conjunction|conjunction]] of two sets) must be less than or equal to the probability of being either a feminist or a bank teller. A conjunction cannot be more probable than one of its constituents. However, participants judged the conjunction (bank teller and feminist) as being more probable than being a bank teller alone.{{sfn|Tversky|Kahneman|1983}} Some research suggests that the conjunction error may partially be due to subtle linguistic factors, such as inexplicit wording or semantic interpretation of "probability".<ref name="Fiedler1988">{{cite journal|last1=Fiedler|first1=Klaus|title=The dependence of the conjunction fallacy on subtle linguistic factors|journal=Psychological Research|volume=50|issue=2|year=1988|pages=123–129|doi=10.1007/BF00309212|s2cid=144369350}}</ref><ref name="Politzer">{{cite journal|last1=Politzer|first1=Guy|last2=Noveck|first2=Ira A.|title=Are conjunction rule violations the result of conversational rule violations?|journal=Journal of Psycholinguistic Research|volume=20|issue=2|year=1991|pages=83–103|doi=10.1007/BF01067877|s2cid=143726019}}</ref> The authors argue that both logic and language use may relate to the error, and it should be more fully investigated.<ref name="Politzer" />

===Disjunction fallacy===
From probability theory the disjunction of two events is at least as likely as either of the events individually. For example, the probability of being either a physics or biology major is at least as likely as being a physics major, if not more likely. However, when a personality description (data) seems to be very representative of a physics major (e.g., having a [[pocket protector]]) over a biology major, people judge that it is more likely for this person to be a physics major than a natural sciences major (which is a superset of physics).{{sfn|Tversky|Kahneman|1983}} 

Evidence that the representativeness heuristic may cause the disjunction fallacy comes from Bar-Hillel and Neter (1993). They found that people judge a person who is highly representative of being a statistics major (e.g., highly intelligent, does math competitions) as being more likely to be a statistics major than a social sciences major (superset of statistics), but they do not think that he is more likely to be a Hebrew language major than a humanities major (superset of Hebrew language). Thus, only when the person seems highly representative of a category is that category judged as more probable than its superordinate category. These incorrect appraisals remained even in the face of losing real money in bets on probabilities.{{sfn|Tversky|Kahneman|1983}} 

===Insensitivity to sample size===
{{main|Insensitivity to sample size}}
Representativeness heuristic is also employed when subjects estimate the probability of a specific parameter of a sample. If the parameter highly represents the population, the parameter is often given a high probability. This estimation process usually ignores the impact of the sample size. 

A concept proposed by Tversky and Kahneman provides an example of this bias in a problem about two hospitals of differing size.<ref name=":0">{{Cite journal|last1=AlKhars|first1=Mohammed|last2=Evangelopoulos|first2=Nicholas|last3=Pavur|first3=Robert|last4=Kulkarni|first4=Shailesh|date=2019-04-10|title=Cognitive biases resulting from the representativeness heuristic in operations management: an experimental investigation|url=https://www.dovepress.com/cognitive-biases-resulting-from-the-representativeness-heuristic-in-op-peer-reviewed-fulltext-article-PRBM|access-date=2021-04-28|website=Psychology Research and Behavior Management|volume=12 |pages=263–276 |doi=10.2147/PRBM.S193092 |doi-access=free |pmid=31040729 |language=English}}</ref>

{{quote|
Approximately 45 babies are born in the large hospital while 15 babies are born in the small hospital. Half (50%) of all babies born in general are boys. However, the percentage changes from 1 day to another. For a 1-year period, each hospital recorded the days on which >60% of the babies born were boys. The question posed is: Which hospital do you think recorded more such days?

* The larger hospital (21)
* The smaller hospital (21)
* About the same (that is, within 5% of each other) (53)
}}

The values shown in parentheses are the number of students choosing each answer.<ref name=":0" />

The results show that more than half the respondents selected the wrong answer (third option). This is due to the respondents ignoring the effect of sample size. The respondents selected the third option most likely because the same statistic represents both the large and small hospitals. According to statistical theory, a small sample size allows the statistical parameter to deviate considerably compared to a large sample.<ref name=":0" /> Therefore, the large hospital would have a higher probability to stay close to the nominal value of 50%.

===Misconceptions of chance and gambler's fallacy===
{{excerpt|Gambler's fallacy}}

===Regression fallacy===
{{excerpt|Regression fallacy}}