In public discourse, we devote much of our collective energy to debating the veracity of facts. We fact-check politicians, monitor misinformation on social media, and prioritize data-driven decision-making in our workplaces. This approach is vital; The distinction between truth and falsehood is the basis of a functional society.
However, by focusing so much on the veracity of facts, we risk overlooking another fundamental distinction: the difference between a fact and an opinion.
A statement of fact is relatively easy to verify: it is true or not. But the objectivity of a claim—is it a verifiable objective claim or a subjective expression of belief?—is much more complex. Therefore, our minds process and encode opinions in a fundamentally different way than facts.
The challenges of objectivity
Objectivity is not a mere linguistic nuance; It is the basis of important political and legal debates. For example, in defamation suits against American media figures such as Tucker Carlson and Sidney Powell, legal defenses focused on whether the statements could “reasonably be construed as fact” or were simply “opinions.”
Similarly, social media platforms have had difficulty verifying posts labeled as opinions, a policy that has recently complicated efforts to combat climate change denialism.
The distinction is important because it defines how we disagree. When a statement is clearly an opinion—for example, “the current administration is failing the working class”—we can agree or disagree, but we understand that there is room for disagreement and that neither side is right or wrong.
However, a factual statement—”The official poverty rate in the US was 10.6% in 2024″—leaves little room for debate. It requires the existence of a source and an objectively correct answer.
As a result, beliefs about the objectivity of claims can stifle receptivity to conflicting perspectives. This, in turn, fuels interpersonal conflicts and fosters political polarization.
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The information we value
Despite these important challenges, research on the cognitive implications of objectivity in assertions is limited. In a recent series of 13 pre-registered experiments with 7,510 participants, conducted with Stephen Spiller of the University of California, Los Angeles (UCLA), and published in the Journal of Consumer Research, we investigated how objectivity in statements affects a specific and crucial type of memory: source memory.
Our findings suggest that the human mind does not treat facts and opinions equally. When it comes to remembering who said what, objective facts are at a distinct disadvantage.
We can illustrate this with an example. One doctor correctly claims that “the measles vaccine prevented approximately 56 million deaths between 2000 and 2021.” Another doctor might say something similar, but giving an opinion instead of data: “I think vaccination is a simple way to prevent unnecessary suffering.”
In our research, we tested this dynamic using medical statements about a fictitious illness to control for prior knowledge. We found that people are significantly more likely to remember the original source of an opinion than that of a fact.
Critically, this is not simply because opinions are more attractive or easier to remember in general. In all 13 experiments, we also measured “recognition memory”: the ability to remember that a statement was made. We did not find consistent differences in recognition memory between facts and opinions. Participants recalled seeing factual statements and opinions with equal accuracy. However, they struggled to link factual claims to the correct source.
Source encoding
Why does this disconnection occur? Source memory is a form of associative memory. It is based on the brain’s ability to link the different components of an experience (what was said and who said it) into a coherent network of interconnected elements during the initial encoding of information.
We propose that the strength of this link depends on one thing: what the statement tells us about its source.
Both facts and opinions provide information about the source, but they do so to different degrees. If a political candidate says, “The United States Agency for International Development (USAID) was created by the Foreign Assistance Act of 1961,” we learn that he knows legislative history. But if that same candidate says, “I think the closure of USAID has been a moral catastrophe for our nation and the world,” we learn a lot more about him. We learn about his values, his priorities, and his stance on America’s role in the world.
Since opinions generally provide more information about the speaker than facts, our brains encode stronger links between sources and opinions than between sources and facts. Studies in developmental psychology and neuroscience support this. Research has found that encoding opinions, compared to facts, produces greater activation in brain regions involved in theory of mind: the ability to represent the thoughts and mental states of others.
When we listen to an opinion, we build a more complete mental model of the sender. This additional social information strengthens the associative bonds that form during encoding.
But what happens when opinions tell us nothing about a source? We tested this mechanism by presenting participants with book reviews. When participants believed that the sources were the authors of the reviews, they remembered the sources of the opinions much better than the facts. However, when we told participants that the sources were simply “reinventors” who read randomly selected reviews, the source memory advantage for opinions disappeared, yielding performance similar to that for facts.
We also test source memory for facts that reveal something about a source, such as personal statements such as “I was born in Virginia.” In these cases, the source’s memory was as accurate as for opinions such as “Chocolate ice cream tastes better than vanilla ice cream.” It was also more precise than for general facts about the world, such as “Stockholm is the capital of Sweden.”
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The paradox of visibility
These findings represent a great challenge for experts and leaders. Authorities are often advised to stick to the facts to maintain credibility, but our findings suggest that by presenting only facts, experts risk being forgotten as sources of important information.
This can pose a problem for the credibility of information: in an era of widespread misinformation and increasing polarization, remembering who said what is increasingly important to avoid conflict and ensure accuracy.
For experts, the goal is usually to anchor facts in reality. Our research suggests that opinion sharing can help people accurately attribute relevant information to credible sources. By sharing what they believe about the data, rather than just the data itself, experts can provide the social cues our brains need to more firmly link information to its source. While facts play an important role in the fight against misinformation, opinions can be just as crucial, and they don’t go unnoticed.
*Daniel Mirny is an assistant professor of Marketing at IESE Business School (University of Navarra).
This text was originally published in The Conversation
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