Anecdotal evidence (or anecdata[1]) is evidence based on descriptions and reports of individual, personal experiences, or observations,[2][3] collected in a non-systematic manner.[4]
The term anecdotal encompasses a variety of forms of evidence, including personal experiences, self-reported claims,[3] eyewitness accounts of others,[5] and those from fictional sources, making it a broad category that can lead to confusion due to its varied interpretations. Anecdotal evidence can be true or false but is not usually subjected to the methodology of scholarly method, the scientific method, or the rules of legal, historical, academic, or intellectual rigor, meaning that there are little or no safeguards against fabrication or inaccuracy.[2] However, the use of anecdotal reports in advertising or promotion of a product, service, or idea may be considered a testimonial, which is highly regulated in certain jurisdictions.[6]
The persuasiveness of anecdotal evidence compared to that of statistical evidence has been a subject of debate; some studies have argued for the presence a generalized tendency to overvalue anecdotal evidence, whereas others have emphasized the types of argument as a prerequisite or rejected the conclusion altogether.[7][8][9][10][11]
"information passed along by word-of-mouth but not documented scientifically"[13]
"evidence that comes from an individual experience. This may be the experience of a person with an illness or the experience of a practitioner based on one or more patients outside a formal research study"[14]
"the report of an experience by one or more persons that is not objectively documented or an experience or outcome that occurred outside of a controlled environment"[15]
Anecdotal evidence may be considered within the scope of scientific method as some anecdotal evidence can be both empirical and verifiable, e.g., in the use of case studies in medicine. Other anecdotal evidence, however, does not qualify as scientific evidence because its nature prevents it from being investigated by the scientific method, such as in that of folklore or in the case of intentionally fictional anecdotes. Anecdotal evidence is considered the least certain type of scientific information.[16] Researchers may use anecdotal evidence for suggesting new hypotheses but never as validating evidence.[17][18]
Anecdotal evidence can have varying degrees of formality. For instance, in medicine, published anecdotal evidence by a trained observer (a doctor) is called a case report and is subjected to formal peer review.[19] Although such evidence is not seen as conclusive, researchers may sometimes regard it as an invitation to more rigorous scientific study of the phenomenon in question.[20] For instance, one study found that 35 of 47 anecdotal reports of drug side effects were later sustained as "clearly correct."[21]
Where only one or a few anecdotes are presented, they risk being unreliable due to cherry-picking or otherwise non-representative samples of typical cases.[22][23] Similarly, psychologists have found that due to cognitive bias, people are more likely to remember notable or unusual examples rather than typical examples.[24] Thus, even when accurate, anecdotal evidence is not necessarily representative of a typical experience. Accurate determination of whether an anecdote is typical requires statistical evidence.[25] Misuse of anecdotal evidence in the form of argument from anecdote is an informal fallacy[26] and is sometimes referred to as the "person who" fallacy ("I know a person who..."; "I know of a case where..." etc.), which places undue weight on experiences of close peers that may not be typical. If an anecdote illustrates a desired conclusion rather than a logical conclusion, it is considered a faulty generalization.[27]
In the legal sphere, anecdotal evidence, if it passes certain legal requirements and is admitted as testimony, is a common form of evidence used in a court of law. In many cases, anecdotal evidence is the only evidence presented at trial.[29]
For a testimony to be considered evidence, it must be given under oath, where the individual swears that they only testify to their own words and actions; someone intentionally lying under oath is subject to perjury. However, these legal rigors do not make testimony in a court of law equal to scientific evidence. Testimony about another person's experiences or words is called hearsay and is usually not admissible, though there are certain exceptions. However, any hearsay that is not objected to or thrown out by a judge is considered evidence for a jury. This means that trials contain a considerable amount of anecdotal evidence that juries find relevant. Eyewitness testimony, a type of anecdotal evidence, is considered the most compelling form of evidence by a jury.[30]
12Irwig, Les; Irwig, Judy; Trevena, Lyndal; Sweet, Melissa (2008), "The weakness of one", Smart Health Choices: Making Sense of Health Advice, Hammersmith Press, retrieved 2024-10-03
↑Lilienfeld, Scott O.; Lynn, Steven Jay; Lohr, Jeffrey M. (2014). "Initial Thoughts, Reflections, and Considerations". Science and Pseudoscience in Clinical Psychology (2ed.). New York: Guilford Publications. p.9. ISBN9781462517510. Testimonial and anecdotal evidence can be quite useful in the early stages of scientific investigation. Nevertheless, such evidence is almost always much more helpful in the context of discovery (i.e., hypothesis generation) than in the context of justification (i.e., hypothesis testing [...]).
↑Gibson, Rhonda; Zillman, Dolf (1994). "Exaggerated Versus Representative Exemplification in News Reports: Perception of Issues and Personal Consequences". Communication Research. 21 (5): 603–624. doi:10.1177/009365094021005003. S2CID145050644.
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