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Does providing a subtle reasoning hint remedy the conjunction fallacy?
Umeå University, Faculty of Social Sciences, Department of Psychology.
2015 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Humans are in general poor at making judgments that adhere to the logical principles of probability theory. One demonstration of this is termed the “conjunction fallacy”: judging a conjunction (A&B) as being more probable than its constituent (A). Systematic commitment of the conjunction fallacy has been shown in numerous studies on probability judgments. Different actions to remedy the fallacy have been suggested. According to the nested-sets hypothesis, when the nested-set structure of a problem becomes clear (i.e. the relation between categories and subcategories), then the conjunction fallacy is remedied. However, previous demonstrations of this remediation have provided very explicit task-related information and it can be questioned whether it is trivial that such information leads to more correct judgments. The primary aim of this study was to test the nested- sets hypothesis in two different formats of a probability judgment task, by more subtly hinting about the nested-set structure. Twenty-nine participants were randomly divided into two groups, one Probability condition and one Informed probability condition, where participants in the latter condition were provided with the hint. The second aim was to investigate whether the Informed probability condition was performed more slowly, potentially due to the time-cost of more elaborated judgments. The results show that a subtle hint about the nested-set structure was able to remedy the conjunction fallacy in a forced-choice probability judgment task but not statistically reliably in a probability estimation task. No response-time differences were observed between the conditions. The results support the nested-sets hypothesis and imply that even a subtle reasoning hint clarifying the relation between categories and subcategories might remedy one of the most robust probability judgment fallacies. 

Abstract [sv]

Människor är i allmänhet dåliga på att göra bedömningar som följer principer för sannolikhetsteori. En indikation på det är ”konjunktionsfelet”: att bedöma en konjunktion (A&B) som mer sannolik än sin konstituent (A). Konjunktionsfelet har påvisats i flera studier på sannolikhetsbedömningar. Olika sätt att avhjälpa felet har föreslagits. Enligt nested-set hypotesen föreslås att när nested-set strukturen av ett problem blir tydlig (dvs. relationen mellan kategorier och subkategorier), minskas benägenheten att begå konjunktionsfelet. Däremot har tidigare demonstrationer av den här minskningen angett väldigt explicit uppgifts-relaterad information och det kan ifrågasättas om det är trivialt att sådan information leder till mer korrekta bedömningar. Studiens primära syfte var att testa nested-set hypotesen i två olika sannolikhetsbedömningsformat, genom att subtilt antyda om nested-set strukturen. Tjugonio deltagare delades slumpmässigt in i två grupper, en Sannolikhetsbetingelse och en Informerad sannolikhetsbetingelse, där den senare betingelsen fick den extra informationen. Det andra syftet var att undersöka om Informerad sannolikhetsbetingelsen skulle utföras långsammare, potentiellt på grund av tids-kostnaden av mer elaborerade bedömningar. Resultatet visar att en subtil antydan om nested-set strukturen minskade konjunktionsfelet i en fler-vals uppgift på sannolikhetsbedömningar men inte statistiskt pålitligt i en sannolikhetsestimeringsuppgift. Inga responstidsskillnader hittades mellan betingelserna. Resultat stödjer nested-set hypotesen och antyder att även en subtil antydan som klargör relationen mellan kategorier och underkategorier kan åtgärda ett av de mest robusta tankefel som observerats vid sannolikhetsbedömningar. 

Place, publisher, year, edition, pages
2015. , 14 p.
Keyword [en]
Conjunction fallacy, reasoning hint, nested sets
National Category
URN: urn:nbn:se:umu:diva-104823OAI: diva2:821296
Educational program
Programme in Cognitive Science
Available from: 2015-08-12 Created: 2015-06-15 Last updated: 2015-08-12Bibliographically approved

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