Making an argument or a case is a challenging task. It requires critical and rational thinking, patience, and knowledge of fallacies to avoid them. Anecdotal evidence is one of the most common fallacies.
What is anecdotal evidence?
Anecdotal evidence arises from claims that something is a universal truth based on an individual’s own personal experience. Emotion and subjectivity drive this type of evidence, not factual information. This post reviews it in further detail.
To understand anecdotal evidence, one must first understand logical fallacies. A logical fallacy is a reasoning error that undermines the logic of your argument.
These fallacies can be irrelevant points or illegitimate arguments — they lack evidence that supports the claim.
What are examples of these logical fallacies?
- Circular argument: This fallacy restates an argument instead of proving it. For example: “The Earth is flat because ships disappear sometimes.” Why is the Earth flat? Because ships disappear sometimes. Why do ships disappear sometimes? Because the Earth is flat.
- Either/or: This fallacy concludes and oversimplifies an argument by reducing it to two choices. For example: “We either use electric cars or destroy the environment.” It excludes other potential alternatives.
- Ad hominem: This fallacy attacks the argument based on the speaker. For example: “That new policy cannot be effective because Trump is the author.”
Fallacies can be:
- Formal: There is a flaw in the logical structure of an argument.
- Informal: There is a flaw in one or more premises of an argument.
Anecdotal Evidence Is an Informal Fallacy
So, anecdotal evidence is an informal fallacy (flaws lie within the premises) where personal experiences are enough to support a position or argument. People tend to use their own personal observation as evidence, even when they know it does not mean anything.
Humans rely on a phenomenon known as cognitive economics. According to the Dictionary of Psychology, the cognitive economy is “the tendency to minimize processing effort and resources.”
People store default assumptions in their memory. For example, everyone knows that pedestrians must walk on the sidewalk for safety reasons. People do not actively decide whether to walk on the sidewalk or the road every day.
Cognitive economics saves time and resources. Humans tend to make assumptions instead of searching for specific evidence. Daniel Kahneman explains in his book Thinking, Fast and Slow that people use two systems when thinking: 1 and 2.
System 1 is quicker and makes assumptions, while System 2 considers and analyzes evidence to make data-driven decisions. People tend to use System 1 to save resources. And that lies the key to anecdotal evidence.
Usually, anecdotal evidence comes from individuals who are not subject area experts. They make an inference and generalize an isolated experience. Everyday examples of this fallacy include:
- I took a supplement and lost weight. This pill definitely works.
- My brother smoked for two decades and didn’t face any health issues. Smoking is not bad.
- Two dogs bit me. All dogs are evil and dangerous.
As one can observe, this type of evidence is not to be trusted. Though it is widely accepted that anecdotal evidence does not equal truth, most people still resort to recommendations about restaurants, hotels, movies, and more. Why?
Humans are likely to remember extraordinary, dramatic personal stories. Emotion sells (one can observe such a phenomenon in marketing), and anecdotal evidence picks the best stories.
A content creator explaining a top-rated product was terrible in their personal experience is a story people remember more easily.
The same goes for the positive. Maybe a restaurant has a 2-star rating, but if your friend claims it is the best restaurant he has ever visited, you are likely to believe him, even when everyone else complains about the place.
One tip to avoid this fallacy is to remember that correlation does not equal causation. Someone can claim that a pill caused weight loss, but did it? That person might be doing other things to lose weight, such as exercising or cutting off calories.
Anecdotal evidence cannot be taken as empirical evidence or proof.
Can Anecdotal Evidence Be Used in Court?
Anecdotal pieces of evidence are, perhaps, the least reliable argument in court. Barry Beyerstein wrote: “anecdotal evidence leads us to conclusions that we wish to be true, not conclusions that actually are true.”
Anecdotal reports can be misleading, which is something to avoid in court. Even when A and B are true, that does not mean the conclusion is true.
- A: My friend got vaccinated against COVID-19.
- B: My friend died a few months after.
- Conclusion: Therefore, the vaccine killed my friend.
Though A and B are true, the conclusion is misleading. There is no way to scientifically prove that A caused B (or vice-versa in another case). Anecdotal information can lead to confirmation bias and does not constitute scientific study or evidence based medicine.
Furthermore, studies of human memory show that one cannot trust a memory one hundred percent. Anecdotal information depends on the accurate perception of the witnesses, often in situations where stress and emotions play tricks on them.
The defense or prosecution cannot phrase an argument as: “Based on my knowledge and experience…” because that does not mean anything.
Another professional can draw an opposite conclusion, even when assuming the same facts. That is why scientific evidence and data deduced from detailed scientific inquiry are preferred forms of evidence.
However, anecdotal evidence can sometimes help in investigations to grasp the bigger picture. It can help make connections and understand what happened better. But it cannot, under any reason, serve as a valid argument in court.
One of the reasons is that people tend to present exclusively anecdotes that support their conclusions, leaving other stories out of the question.
Humans Are Not Rational
Human beings try to be as logical and rational as possible, but that is simply impossible due to emotion, cognitive bias, perception of the world, previous individual experience, and more.
Anecdotal evidence can be a fun way of deciding whether to try a new restaurant, hotel, or video game. They make great stories to share at the dinner table on a Saturday evening.
But a hasty generalization is not the way to go for witness testimony when one aims to prove something or make an argument for a case.