Cherry picking (fallacy)
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Cherry picking, suppressing evidence, or the fallacy of incomplete evidence is the act of pointing to individual cases or data that seem to confirm a particular position, while ignoring a significant portion of related cases or data that may contradict that position. It is a kind of fallacy of selective attention, the most common example of which is the confirmation bias. Cherry picking may be committed intentionally or unintentionally. This fallacy is a major problem in public debate.
The term is based on the perceived process of harvesting fruit, such as cherries. The picker would be expected to only select the ripest and healthiest fruits. An observer who only sees the selected fruit may thus wrongly conclude that most, or even all, of the fruit is in such good condition. A less common type of cherry picking is to gather only fruit that is easy to harvest, ignoring quality fruit higher up the tree. This can also give a false impression of the quality of the fruit (since it's only a sample).
Cherry picking can be found in many logical fallacies. For example, the "fallacy of anecdotal evidence" tends to overlook large amounts of data in favor of that known personally, "selective use of evidence" rejects material unfavorable to an argument, while a false dichotomy picks only two options when more are available. Cherry picking can refer to the selection of data or data sets so a study or survey will give desired, predictable results which may be misleading or even completely contrary to actuality.
Choosing to make selective choices among competing evidence, so as to emphasize those results that support a given position, while ignoring or dismissing any findings that do not support it, is a practice known as "cherry picking" and is a hallmark of poor science or pseudo-science.— Richard Somerville, Testimony before the US House of Representatives Committee on Energy and Commerce Subcommittee on Energy and Power, March 8, 2011.
Rigorous science looks at all the evidence (rather than cherry picking only favorable evidence), controls for variables as to identify what is actually working, uses blinded observations so as to minimize the effects of bias, and uses internally consistent logic."— Steven Novella, April 26, 2011
In a 2002 study, researchers "reviewed 31 antidepressant efficacy trials to identify the primary exclusion criteria used in determining eligibility for participation. Their findings suggest that patients in current antidepressant trials represent only a minority of patients treated in routine clinical practice for depression. Excluding potential clinical trial subjects with certain profiles means that the ability to generalize the results of antidepressant efficacy trials lacks empirical support, according to the authors."
In argumentation, the practice of "quote mining" is a form of cherry picking, in which the debater selectively picks some quotes supporting a position (or exaggerating an opposing position) while ignoring those that moderate the original quote or put it into a different context.
- Biased sample
- Confirmation bias
- Proof by example
- Fallacy of quoting out of context
- Hasty generalization
- Parkinson's law of triviality
- Informal fallacy
- Selection bias
- The Internet Encyclopedia of Philosophy, "Fallacies", Bradley Dowden (2010)
- Cherry Picking
- Klass, Gary. Just Plain Data Analysis: Common Statistical Fallacies in Analyses of Social Indicator Data. Department of Politics and Government, Illinois State University. Statlit.org. ~2008. Accessed March 25, 2014. http://www.statlit.org/pdf/2008KlassASA.pdf.
- Goldacre, Ben (2008). Bad Science. HarperCollins Publishers. pp. 97–99. ISBN 978-0-00-728319-4.
- "Devious deception in displaying data: Cherry picking", Science or Not, April 3, 2012, retrieved 16 February 2015
- Steven Novella, "Science-Based Medicine", A Skeptic In Oz, retrieved 16 February 2015
- "Typical Depression Patients Excluded from Drug Trials; exclusion criteria: is it "cherry picking"?". The Brown University Psychopharmacology Update (Wiley Periodicals) 13 (5): 1–3. May 2002. ISSN 1068-5308. Based on the studies:
- Posternak, MA; Zimmerman, M; Keitner, GI; Miller, IW (February 2002). "A reevaluation of the exclusion criteria used in antidepressant efficacy trials". The American journal of psychiatry 159 (2): 191–200. PMID 11823258.
- Zimmerman, M; Mattia, JI; Posternak, MA (March 2002). "Are subjects in pharmacological treatment trials of depression representative of patients in routine clinical practice?". The American journal of psychiatry 159 (3): 469–73. PMID 11870014.