Theresa is 31, single, outspoken and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice. She also participated in anti-nuclear demonstrations.

Which is more likely? Theresa is...

A. A bank teller
B. A bank teller active in
the feminist movement.
Click button to answer  

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The conjunction fallacy

The conjunction fallacy occurs when we assume that specific conditions are more probable than a single general one. Academicians Rajeev Gowda and Jeffrey C. Fox explained how many people choose answer two, although the probability of two events occurring together is always smaller than either one occurring alone. Psychologists Amos Tversky and Daniel Kahneman argued that we make this error because the second answer seems more ‘representative’ of Theresa, although it is less likely.

This bias is sometimes used in politics to make an unlikely event more credible for voters by adding specific details. One example is President Trump’s assertion that millions voted illegally in the 2016 presidential election, causing him to lose the popular vote. Trump has claimed that between 3 million and 5 million people voted illegally, mainly in states like California, Virginia or New Hampshire, and that people were brought in on buses from Massachusetts to vote in the latter.
The American Civil War took place from 1861 to 1865.

What year did Congress hold its first session in the Capitol?

You say: 1780
Drag to select a year

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Anchoring bias

The first session of Congress in the Capitol happened in 1800, and that fact is totally unrelated to the Civil War. Anchoring bias happens because, in our decision-making, we rely too heavily on the first piece of information that is given to us, even if it is not related to the same issue.

For example, one of Barack Obama’s major promises as president was to have the most transparent administration in history. The creation of an open data portal, his open-data policy and related executive actions created an impression of openness that was not translated to other important matters, like his administration’s more punitive treatment of whistleblowers.
All cherry trees are plants. Some plants fade quickly. Therefore, some cherry trees fade quickly.

Is the last sentence TRUE or FALSE?

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Cognitive ease: Illusory truth effect

Cognitive ease makes us feel more favorable toward things that are familiar and easy to understand. Our brain is wired to accept what is familiar. That can make us resistant to new assessments, even when presented with reliable facts. The illusory truth effect is a consequence of this cognitive bias. It is the tendency to believe information because it is repeated often. Our minds need to make quick judgments, so we take shortcuts. Relying on how often you’ve heard something to judge the truth of something is just one strategy.

During the Obama administration, many of Obama’s opponents claimed the president was Muslim. They used details, like the fact that his middle name is Hussein, or that he lived in Indonesia (a majority Muslim country) as proof of his religious beliefs. Obama is a practicing Christian, but enemies tried to use this bias to convince some that the President had a secret agenda.
Tina: Intelligent - industrious - impulsive - critical - stubborn - envious
Telma: Envious - stubborn - critical - impulsive - industrious - intelligent

Which one do you see more favorably?

A. Tina
B. Telma
C. Neither

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Halo effect

Both descriptions are the exact same words in a different order. The halo effect relies on the weight of the first impression. It is also the phenomenon whereby we assume that because people are good at doing A, they will be good at doing B, C and D, whatever B, C or D is. This is why many people believe that beautiful people are better at their jobs.

A Washington Post-ABC poll in January 2017 found that 61 percent of American voters expected President Trump to do an excellent or good job handling the economy, higher than for many other issues. Because Trump didn't have any governing or political experience at that time, these expectations may have been rooted in his reputation as a successful businessman. People may have believed that his private-sector experience would translate to effective handling of economic policy, although these roles involve different expertise.
Hector thought of a rule for a sequence of three numbers.
The numbers are 3, 9 and 81.

Try to guess the rule by proposing three sequences of the three numbers. We’ll tell you if your sequences follow the same rule.

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Confirmation bias

Confirmation bias is the tendency to look for and favor information that confirms our beliefs. In this example, you may have been biased toward believing that the question was hard, thereby overcomplicating your answer.

In politics, this bias can lead us to believe in anything that supports our beliefs, even if no facts are given or the facts given are incorrect. When a politician tells supporters what they want to hear, they’re leveraging this bias. Post Opinion writer David Ignatius wrote about this issue in his column “Why facts don’t matter to Trump’s supporters”, but politicians from all sides make use of it.


These are just five of the multiple cognitive biases we experience daily.
Tversky and Kahneman introduced these concepts in 1972, proving that we are not completely rational individuals. Cognitive biases lead to a distorted perception of reality, causing us to make judgments inaccurately, make illogical interpretations and come to irrational conclusions. These same biases allow us to make optimal and quick decisions in everyday tasks.

Politicians and marketing professionals understand and utilize these biases in their daily work. Being aware that these biases exist can help us be smarter and more critical of our initial reactions.

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