When we say “anecdote” we usually mean a short, humorous story about an event or person, and in a broader sense, it is any story about an event that may not even be true. However, anecdotal evidence is a way of supporting our thesis, a way of arguing that we are not referring to facts but to a story that may or may not have happened.
In fact, references to anecdotal evidence is intentional or unintentional error in reasoning, and the consequences of such argumentation can be serious. At the same time, anecdotal evidence of can be a good foundation for science, the initiator of research into a phenomenon about which we do not have enough information.

You heard that…

You must have already come across stories like this in your daily life – you have heard that someone was healed using a folk remedy, or that a child from a friend’s aunt had severe consequences after vaccination. In our country there is also “evidence” that a cold breeze, combined with wet hair, can lead to brain inflammation and partial paralysis of the face.

Simply, one’s experience, and a told-story tale of truth and importance, usually outweighs scientific evidence and scientific discourse.
All this annoys those who advocate science because a lot of energy is spent on presenting the truth and evidence based on, perhaps not perfect, but pretty good methods for it all to fall into the water because of a friend’s aunt. In doing so, anecdotal evidence is spreading very quickly and no one is checking to see if a friend has an aunt, and what actually happened to some child.

People often build a picture of the world based on stories like this, which is rather unusual, because we are not the type known for learning from others’ experiences. But we love to tell stories. Namely, for thousands of years we have survived telling each other stories, inventing new narratives and listening. Telling and listening to stories reinforces a sense of community and this connection is much older than the beginnings of rational and critical thinking, skepticism and individualism.

Experience as a measure of truthfulness

The signs of skepticism and individualism in literature are found in Michel de Montaigne, in his book Essais of 1580, where the author describes himself very honestly and without beautification. His contemporary, Francis Bacon, begins an era of empiricism, the philosophical direction toward which knowledge comes from sensory experience. Only later comes to the development of rationalism, the idea of which the main figures were Descartes, Spinoza and Leibniz, according to which the ratio main source of the knowledge. However, experience remains a good and significant source of cognition to this day, and we rely heavily on it in our lives.

Direction of thinking in which experience is the main source of knowledge, reached its limits in anecdotal evidence, as often seen on social networks, represents light, it is a drinkable form that is easy to adopt as truth.

So, if making inferences based on experience is one way of understanding the world around you, why is anecdotal evidence a kind of logical fallacy? This is very important to understand because it is precisely anecdotal evidence that feeds our fears, our irrational being, which is very much a part of us, but inference on the basis of anecdotal evidence can be, and often is, the path to bad decisions.

The anecdotal evidence is, in fact, a complete distortion of principles of empiricism, especially cognition that comes a priori. Why? Quite simply – anecdotal evidence is not a personal experience, it is not something we have experienced, touched, felt by other senses. It is a story that we identify with because it brings an emotional narrative line, a situation in which we can imagine ourselves and fear that might happen to us. However, it is the story of one’s experience that may or may not be true.

But, even if the anecdotal evidence is based on truth, it is still not valid for making conclusions and decisions, especially not important decisions, such as our own or others’ health. Even experience sometimes did not measure truthfulness: deja vu or mirage and we can perceive these optical deceptions as real, but they are delusions of our mind.
On the other hand, we have a whole world of elementary particles, which we cannot see, feel, smell, we can not perceive them experientially, but which is very real. We prove it in theory and with mathematical models.

What’s wrong with anecdotal evidence?

The basic thing about anecdotal evidence is that it is based on a small sample, usually made from a single case or anomaly .
For example, the side effects of vaccination against measles, rubella and mumps vaccine indicate that serious complications can occur. But it is something that happens at a billion or even 100 billion doses and is actually so rare that experts can’t accurately estimate how often it is. However, it is possible to “pick up” only one known case of such a complication and present it as a general law, precisely through anecdotal evidence.
This way of “picking up” evidence that presents only cases that favor the thesis of the one who uses anecdotal evidence also has its English term, “cherry picking.” And it is just that – you have a cherry tree, full of fruit, but you pick the reddest, sweetest or the nearest fruit. You choose the fruits that suits you best. Not every cherry picking may be anecdotal evidence, but most do.

To make a conclusion based on anecdotal evidence is to say that just because some citizens of one country go to very expensive tourist sites, it means that all citizens of that country are rich and to conclude that they are all very high, just based on the height of the members the basketball team of that country.
Science does not neglect individual cases – there are so-called “case studies” in which extremely rare and unusual cases, such as rare hereditary diseases, syndromes, specificities, are studied. However, in the two cases, although well done, may be of inestimable value, they are in fact the weakest form of evidence, and usually each new case is very important because it represents a strengthening of the evidence.
Animal studies are also not exactly the best evidence because often the metabolism of laboratory animals and their physiology and genetics do not reflect the best of human physiology and genetics, and what worked for animals, such as a drug, may not be effective on humans. The highest level of evidence, the strongest evidence comes after extensive metastudies and systematic studies covering a large number of cases.
Another problem with anecdotal evidence is that they are usually subjective. These are not data, nor the statistics. Third – if the event did happen, it does not mean that it will happen again under the same conditions. For example, if someone suffocated by eating fish because the fish bone was stuck to their throats, this does not mean that the same will happen to us.

Furthermore, anecdotal evidence is highly unpredictable. This means that there are very many variables which could affect certain developments that have created an anecdote, but as these variables are not scientifically observable nor measured, anecdotal evidence does not provide the insight into why something happened.

There is no “black box” of data or measurements of observable positive changes in therapy during the anecdote itself. We only have a zero state – before the event, which is based on tell-tale, and a new state, after the event, which, again, is based on tell-tale.
However, as a species, we are more inclined to believe the narrative, – because if someone told us that there is a predator in the area, or a source of water or food – believing in a narrative was evolutionary advantage.



Jelena Kalinić, MA in comparative literature and graduate biologist, science journalist and science communicator, has a WHO infodemic manager certificate and Health metrics Study design & Evidence based medicine training. Winner of the 2020 EurekaAlert (AAAS) Fellowship for Science Journalists. Short-runner, second place in the selection for European Science journalist of the year for 2022.