TL;DR: Confirmation bias is the tendency to seek, interpret, and recall information in ways that reinforce existing beliefs. At a fortune-telling session, we notice and remember the predictions that came true while forgetting or dismissing the ones that did not. This is an ordinary human psychological mechanism, not evidence of prophetic ability.
What is confirmation bias?
Confirmation bias is the tendency to seek out, interpret, prioritise and remember information in ways that reinforce or support beliefs, values or decisions we already hold. According to Nickerson (1998), in Confirmation Bias: A Ubiquitous Phenomenon in Many Guises, Review of General Psychology 2(2): 175-220, confirmation bias is the tendency to seek out, interpret and remember information in ways that reinforce existing beliefs. When we go for a reading, for Tử Vi (Vietnamese astrology) or for any form of prediction, it is this very mechanism that makes us remember the predictions that came true and forget the ones that did not.
Confirmation bias needs to be distinguished from the self-fulfilling prophecy. In a self-fulfilling prophecy, our expectations change our own behaviour, and that in turn produces the expected outcome. Confirmation bias, by contrast, is purely a matter of information processing: we do not make events happen, we simply filter and distort how we take in, interpret and recall those events.
Some psychologists restrict the term to the selective gathering of evidence. Others use it more broadly, to include the tendency to preserve existing beliefs when seeking, interpreting or recalling. According to Nickerson (1998), the common thread is this: it is the result of automatic, unintentional strategies, not of calculated deception.
Why do we remember hits and forget misses?
The answer lies in three mechanisms: biased information search, biased interpretation and biased memory. All three work together to create the feeling that the fortune teller was remarkably accurate.
First, we tend to seek out information that supports the hypothesis we already hold. Once we believe a fortune teller has a special gift, we pay attention to the predictions that came true, store them in memory and retell them to others. The predictions that missed we rarely mention, and may not even remember.
Second, we interpret ambiguous information in a direction that favours our existing belief. A prediction such as "there will be sadness in the family" can match almost any event in the following months. When something sad happens, we attribute it to the reading straight away. When nothing happens, we forget the prediction, or tell ourselves "the time must not have come yet".
Third, our memory does not record events faithfully. We remember what fits our current beliefs and emotions, and we forget or distort what does not. This is why the feeling that "the fortune teller was right" is usually far stronger than the reality.
What is illusory correlation?
Illusory correlation is the phenomenon in which we perceive a relationship between two variables (usually people, events or behaviours) even when no such relationship exists. It happens because rare or novel events stand out and draw our attention more than others do.
The classic example: Hamilton and Gifford (1976), in Illusory correlation in interpersonal perception: A cognitive basis of stereotypic judgments, Journal of Experimental Social Psychology 12(4): 392-407, had participants read statements describing good and bad behaviours, assigned to Group A (the majority) or Group B (the minority). Both groups had the same proportion of good and bad behaviours, so in reality there was no relationship at all between behaviour and group. But when a bad behaviour (distinctive, striking) appeared in the minority group, participants exaggerated how often the minority group performed bad behaviours. Good behaviours made no particular impression, so they were recorded more accurately.
In the context of divination, illusory correlation works like this: a prediction that rarely comes true (because it is specific and striking) gets remembered and linked to the fortune teller. The vague, general or plainly wrong predictions, which make up the majority, leave no impression and are forgotten. The result: we believe the fortune teller has a special gift, even though the hit rate is no better than chance.
This mechanism rests on availability: what is easy to recall and easy to picture is estimated to be more frequent. A prediction that came true leaves a strong, memorable impression, so we assume it happens often. A prediction that missed leaves no impression, so we do not count it.
Related types of confirmation bias
Four psychological effects are often grouped together and often explained through confirmation bias:
- Attitude polarisation: when two sides who disagree are shown the same piece of evidence, their positions become more extreme.
- Belief perseverance: a belief survives even after the evidence for it has been discredited.
- Irrational primacy effect: we rely more heavily on the information we encountered first in a sequence.
- Illusory correlation: we perceive a relationship between two things even when they are unrelated.
These effects explain why a person can believe in fortune telling, Tử Vi or other forms of prediction despite having been disappointed many times. Each disappointment is forgotten, each hit is remembered and retold, and together they build a distorted picture of reality.
Table comparing the forms of bias in fortune telling
| Form of bias | How it shows up in a reading | Consequence |
|---|---|---|
| Biased search | Paying attention only to predictions that came true, ignoring those that missed | Believing the fortune teller has a special gift |
| Biased interpretation | Attributing ambiguous events to the prediction, ignoring other readings | Vague predictions are treated as accurate |
| Biased memory | Remembering hits clearly, forgetting misses | Estimating the hit rate as higher than it is |
| Illusory correlation | Pairing a rare prediction with a striking event | Creating a sense of causation that is not real |
Why do intelligent people still believe?
Shermer (2002), in Smart People Believe Weird Things, Scientific American, September 2002 (the Skeptic column), writes: "Smart people believe weird things because they are skilled at defending beliefs they arrived at for non-smart reasons." Lord, Ross and Lepper (1979), in Biased assimilation and attitude polarization: The effects of prior theories on subsequently considered evidence, Journal of Personality and Social Psychology 37(11): 2098-2109, showed that among supporters and opponents of the death penalty, both sides, reading the same study, judged the research supporting their own view to be of higher quality and the research opposing their view to be less convincing. They produced detailed arguments to defend the position they already held.
What this means is that a high level of education does not protect us from confirmation bias. On the contrary, people with strong reasoning skills can become more effective defenders of what they already believe. In the context of fortune telling, a knowledgeable person can find many ways to explain a missed prediction as "right in some sense", or a vague prediction as "right later on".
What are the limits of confirmation bias?
People are not always biased in one direction. Some studies show that we tend to prefer genuinely diagnostic questions over questions that merely confirm. In one experiment, when given a choice between a biased question and a diagnostic one, participants chose the diagnostic question. This suggests that confirmation bias is not an absolute law but a tendency that can be adjusted when we are prompted, or when we have a reason to think more carefully.
One study suggests that illusory correlation can be reduced when people understand the conditions that make them prone to misperceiving a relationship, though the evidence on how effective such education is remains limited. What that means is that understanding the psychological mechanism can help us be less governed by it, at least in some situations.
How can we test ourselves and reduce the bias?
If we want to check whether a fortune teller or a prediction method is genuinely accurate, we need to do the very thing confirmation bias prevents: look for evidence against, not evidence in favour.
- Write down every prediction, not only the ones that came true. Count the wrong ones and the ones that never happened at all.
- Set clear criteria in advance: what counts as a "hit", what counts as a "miss", and over what period of time.
- Look for counter-evidence: if the fortune teller says "there will be financial good fortune this year", look for years without financial good fortune to compare against.
- Ask someone else to assess it independently, because we usually cannot see our own biases.
These steps are not meant to dismiss every spiritual experience, but to separate subjective feeling from objective reality. The feeling that "the fortune teller was right" can be entirely real, but it does not automatically become scientific evidence.
