Friday, April 4, 2014

Why stories are not evidence: Anecdotal Fallacy

The anecdotal fallacy is committed when someone rejects or discounts extensive evidence in favor of an isolated or personal experience. If the audience wants to believe in something, they will often cling to anecdotes as evidence even if there is no other evidence or documentation for the phenomenon (consider Urban Legends). This fallacy is partly due to the availability heuristic which causes people to overestimate how common something is based on how easily they can think of an example. People are more prone to remembering exceptional events, and thus, by definition, anecdotes are more often the exception and not the rule. In addition, most people don’t take into consideration the vast numbers of “unexceptional” stories that are more in line with reality because they rarely hear about them or, if they do, they don’t remember them because they are so typical. (Other names include the "I know a person who" fallacy.)

How it applies: People often use this fallacy in dismissing science. For the general population, it is often easier to believe a testimonial of someone “just like you” than the nuances of dozens of complex scientific studies that have been accumulating for years. Even though science is significantly more reliable than anecdotes because of the rigorous amount of testing and peer-review it has to go through for it to be accepted, people will tend to accept a relatable isolated example, often cherry-cherry picked for its adherence to a particular belief, over statistical data backed up by extensive evidence. Often people use anecdotal evidence to confirm their belief or unbelief in a supernatural being: If you pray to God to heal your grandmother, and she gets better, that is not proof that God intervened; likewise, if she doesn’t get better, that doesn’t mean that God doesn’t exist.


  • I thought about my grandmother and a few minutes later she called. That proves telepathy is a fact.
  • There's abundant proof that God exists and is still performing miracles today. Just last week I read about a girl who was dying of cancer. Her whole family went to church and prayed for her, and she was cured.
  • Yeah, I’ve read the health warnings on those cigarette packs and I know about all that health research, but my brother smokes, and he says he’s never been sick a day in his life, so I know smoking can’t really hurt you.
  • According to statistics, smoking causes you to die young. But my Grandmother Sally smoked like a chimney and lived until she was 95, so clearly the statistics are wrong.
  • My uncle Chet told me once that he used to get welfare even though he had a good job. Therefore, we need to get rid of the welfare system because it's being defrauded way too much.
  • My cousin was in a car accident and wasn’t wearing his seatbelt. He was thrown from the car and walked away without any injuries. So we don’t really need seatbelts.

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