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The Digital News Report 2021, a key study published annually by the Reuters Institute, reveals that people are primarily concerned about falsehoods spread by politicians and the media. In the case of COVID-19, 42% of Spanish respondents expressed concern about misinformation and misleading content disseminated by governments, political parties, and politicians. This is followed by concerns about falsehoods spread by the media and journalists (11%), foreign governments (11%), activists (10%), and ordinary people online (9%). But who, in contrast, worries about the falsehoods our own brains lead us to believe? Who is truly aware of the cognitive biases that we all have?

Our brain constantly makes countless decisions at incredible speed. To conserve cognitive energy, it sometimes switches to “low battery mode”, simplifying processes and taking shortcuts. In psychology, this is known as «heuristics». However, these shortcuts can sometimes lead us to mistakes, and when that happens, we experience what we call «cognitive biases». Begoña Díaz, psychologist, PhD in Cognitive Science and Language, and professor at UIC Barcelona, explains how they work: «Cognitive biases always lead us to favor certain types of responses over others. We don’t evaluate all the information available to us, nor do we even question whether we have enough information. Instead, they provide us with mental shortcuts. This, in turn, causes us to make systematic errors».

Xavier Oriol Granado, a researcher in the Department of Psychology at the University of Girona, adds: «Our brain adapts to its environment and creates mental shortcuts to become more efficient. Cognitive biases are adaptations the brain makes to maximize, in some way, survival, reproduction, and social life».  Helena Matute, Professor of Experimental Psychology at the University of Deusto in Bilbao and author of Our Mind Deceives Us: Cognitive Biases and Errors We All Make, describes cognitive biases as: «The errors we all make in a more or less systematic way, as if we were programmed (in fact, we are) to make the same mistake». In the book, Matute emphasizes: «Our mind deceives us, and the sooner we become aware of it, the better. These adaptations are not about accurately perceiving and remembering reality, but rather about perceiving and remembering what helps us make better decisions to increase our chances of survival.».

Here, we list some of the most well-known cognitive biases that play a role in both information processing and disinformation:

When we seek information, we often look for ways to confirm our existing beliefs because it makes us feel good. This is known as “confirmation bias”. Professor Begoña Díaz from UIC Barcelona explains: “We are thinking machines that believe we are always right, that we cannot be wrong.” Both journalists and audiences are influenced by this bias. Díaz states: “We tend to seek only information that aligns with our beliefs. We also frame our questions in a biased way.” For example, a journalist might design a questionnaire that confirms a pre-existing idea rather than digging deeper to uncover the full picture. This bias leads us to consistently buy newspapers that align with our worldview; search for information on Google in a way that validates what we already believe. Moreover we tend to trust misinformation more easily if it aligns with our opinions.

Our brain simplifies reality by categorizing people into two major groups: “us” and “them”. The «us», which we belong to, is perceived as good—to put it simply—while the «them» group, which we don’t identify with, is seen as bad, mistaken, or even threatening. This bias makes us more likely to believe misinformation that reinforces the idea that the others are wrong or dangerous, while we are right and good.

Do you believe every TikTok or Instagram video featuring someone in a white coat? Do you ever question whether they are real doctors or just wearing a white coat to appear credible? Authority bias occurs when we attribute credibility and authority to someone who doesn’t actually have it. For example, we might trust an influencer with no scientific background when they talk about nutrition or climate change. This bias is also widely used in advertising, where we associate quality with a product just because a celebrity promotes it. Authority bias can lead us to believe false information if it comes from someone we admire or from someone pretending to be an expert.

When a ship drops anchor, it stays in place. Our brain works the same way. “The first piece of information we receive shapes our opinion. Later, we might encounter contradicting information, but we tend to ignore it”, explains Díaz. This bias is particularly problematic in today’s fast-paced world, where immediacy is everything. The media rush to be the first to report a story, but if they make a mistake, corrections rarely reach the same audience. Anchoring bias also explains why false initial information spreads much further than its correction. This is why fact-checkers work on pre-bunking,  which it is considered  more effective than debunking. If the correction reaches you first, you are less likely to believe the falsehood later.

This bias implies we tend to believe information that seems true, simply because it feels familiar. We tend to trust things we’ve heard repeatedly, which is why conspiracy theories and viral hoaxes spread so easily. Illusory truth bias also explains why we fall for lies that involve identity theft, when someone impersonates a person, company, or institution. Deepfakes exploit this bias. Social media platforms like Twitter, WhatsApp, and YouTube further reinforce this effect, making false information feel familiar and, therefore, more believable.

“It’s about making us believe that everyone thinks the same about the topic being presented. This is widely used in political meetings,” says Díaz. This bias can have a significant impact on public opinion, as people tend to align themselves with what they perceive as the majority opinion. For example, when media coverage of elections prioritizes polls, it can influence voters to support the leading candidate. On social media, we are more likely to believe what is widely shared within our community.

This bias leads us to focus only on information that interests us or aligns with our beliefs. It strongly influences how we seek and process information, but it also affects journalists and the way they shape narratives about reality. For example, people who believe that genetically modified foods are harmful are less likely to pay attention to studies or reports that suggest otherwise.

Both Matute, Granado, and Díaz agree: it’s difficult. But we can try it. There are strategies and research efforts aimed at reducing bias, a process known as “debiasing” (from the English word bias). Díaz explains that these studies have focused on explaining cognitive biases and encouraging people to consider different perspectives when making decisions. “Changing these mechanisms is difficult because they are highly automatic. Switching to an anti-bias mode requires a significant cognitive effort,” continues the UIC Barcelona professor. Despite the challenge, minimizing bias in decision-making requires us to be aware, take our time and seek out diverse sources.

Granado, for his part, advocates for teaching critical thinking: “We need to explain in schools that consuming information too quickly carries a significant emotional impact. We must also highlight the challenges this creates for us as human beings. We should strive to analyze news and information much more critically. It’s difficult to do when, in reality, society is moving in the opposite direction.” Díaz reflects:”Staying well-informed requires a lot of energy, but it’s worth it.”

Although journalism is based on facts and data, the way we consume information is often emotional. And so is disinformation. One of the key reasons disinformation spreads so effectively is that it triggers fear, explains Díaz: “When disinformation appeals to our fears, there’s little we can do. It taps into a fundamental emotion: survival. We are made to survive”. Regarding infodemia or the overabundance of information, the UdG researcher explains: “Our brain has not evolved to process such a massive amount of information, and we tend to rely heavily on headlines and short messages”. Granado adds that when we consume news today through platforms like Twitter or Facebook, we process it in a much more emotional way. In contrast, decades ago, information was consumed more rationally (what is known as Daniel Kahneman’s theory of System 1 and System 2 thinking. Kahneman was a psychologist and Nobel Prize winner in Economics 2002).

The UdG researcher criticizes the polarization promoted by social media platforms: “When your team scores a goal, it creates a sense of collective euphoria. In social psychology, we call this ’emotional contagion.’ Historically, it has always been observed in collective rituals. It used to happen in groups that were physically together in a specific place and time; now, this space is virtual and can be infinite. But our brain is wired to function in small groups. This is one of humanity’s greatest challenges today.”

Granado believes that polarization “is a very tribal behavior that we had, in some way, tried to overcome after World War II, but social media is bringing it back again.”