Anecdotal evidence is a term referring to evidence that is collected in a non-scientific manner and supported by isolated, specific instances of an event. It relies on personal testimonies rather than on scientific evidence and, consequently, is considered the weakest type of evidence.
In the world of advertising and marketing, anecdotal evidence is known as testimonials.
The anecdotal fallacy is a logical fallacy that occurs when someone argues on the basis of anecdotal evidence. It’s an extremely common type of error found in a wide variety of arguments. Moreover, it is often committed due to a lack of argumentation skills, however, it can be used intentionally as a debate tactic.
As such, taking the time to learn how this error in logic works and when exactly it is committed can be useful to almost anyone: it can improve one’s argumentation and decision-making by helping to identify and counter the misuse of anecdotal evidence.
This logical fallacy is also known as the “Volvo fallacy”, “proof by selected instances,” and the “person who fallacy”.
What Is an Anecdotal Fallacy?
The fallacy of anecdotal evidence arises when someone uses proof that relies on personal testimonies, such as a story based on someone’s individual experience, in order to support or refute a claim.
In other words, this means that the speaker draws a general conclusion based on a limited number of examples that are collected in an informal way (and often cherry-picked in favor of the argument).
A typical logical form for such an argument is either:
- Y occurred once when X.
- Therefore, Y will occur every time when X.
- Person Y told me that he saw/heard X.
- Therefore, X must be true.
👉 An example of anecdotal fallacy would be:
“My grandfather was a heavy smoker most of his life, but he lived to be 90 years old. Therefore, smoking is not harmful to people.”
Here, the notion that a single individual lived to old age despite smoking is anecdotal evidence and, in reality, does not prove that smoking is harmless. In such issues, there will be exceptions to the rule, and simply pointing out one of those exceptions doesn’t disprove the rule; only statistical evidence can show us how typical something is.
Another problem with anecdotal evidence is that the way it is collected and presented is subject to cognitive biases. For instance, someone may be affected by the confirmation bias and bring up only those instances that are in support of their existing beliefs, or they may put unwarranted credibility to a particular claim due to our innate tendency, known as the bandwagon effect, to adopt something because a lot of other people are doing it.
👉 Here’s a list of examples of the anecdotal fallacy:
- “Self-driving cars are too dangerous to be used on public roads. Just last week, I read about a case where a self-driving car caused a fatal crash.”
- “Why aren’t we treating cancer with broccoli? My friend told me that there have been a few cases where a cancer patient was cured after they switched to a broccoli-based diet.”
- “There is plenty of evidence that God exists: I’ve heard from many sources that people have become religious after God spoke to them personally.”
- “My aunt has been on a low-fat diet for 2 months now, and she has lost several kilograms. She says it’s definitely the best diet out there.”
- “Many people have experienced something they can only describe as paranormal experience, so it really must be true.”
Arguments from anecdotal evidence are frequently involved with the post hoc fallacy, which is the false assumption that one event must have caused another event because it happened before the other.
As seen in one of the examples above, if someone claims that a certain change in the diet must have been the cause of a later event – such as getting cancer-free – solely based on the fact that they occurred consecutively, they are falling prey to post hoc reasoning.
This reasoning is fallacious since, even though events that occur in succession may well be causally related, they can also (and often are) be completely unrelated apart from the fact that the other happened after the other.
This is a logical fallacy that arises when one draws a conclusion on the grounds of too few examples rather than looking at more reliable statistics.
The main difference between the topic of this article and hasty generalization is that in the former, the given examples are specifically selected to support the claim, but in the latter one, the conclusion is drawn from a too small sample size that was available to the arguer.