Why we remember the source of an opinion better than the source of a fact

In public discourse, we spend a great deal of collective energy debating the accuracy of facts. We fact-check politicians, monitor social media for misinformation, and prioritise data-driven decision-making in our workplaces. This focus is vital; the distinction between truth and falsehood is the bedrock of a functioning society.

However, by focusing so intently on factual accuracy, 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 either true or not. But a claim’s objectivity – is it a verifiable objective statement or a subjective expression of belief? – is far more complex. This is why our minds process and encode opinions in a fundamentally different way to facts.

The stakes of objectivity

Objectivity is not a mere linguistic nuance; it lies at the foundation of important policy and legal debates. For instance, in defamation lawsuits against US media figures like Tucker Carlson and Sidney Powell, legal defences have hinged on whether statements could “reasonably be interpreted as facts” or were merely “opinions.” Similarly, social media platforms have struggled with whether to fact-check posts labelled as opinions, a policy that has recently complicated efforts to combat climate change denialism.

The distinction matters because it frames how we disagree. When a claim is clearly an opinion – for instance, “the current administration is failing the working class” – one may agree or disagree, but we understand that there is room for disagreement and neither side is inherently right nor wrong.

However, a factual statement – “The official US poverty rate was 10.6% in 2024” – leaves little room for debate. It necessitates the existence of a source, and an objectively correct response.

As a result, beliefs about claim objectivity can stifle receptiveness to conflicting perspectives. This, in turn, fuels interpersonal conflict and drives political polarisation.

The information we value

Despite these high stakes, there has been limited research on the cognitive implications of claim objectivity. In a recent series of 13 pre-registered experiments involving 7,510 participants, conducted with UCLA Anderson’s Stephen Spiller and published in the Journal of Consumer Research, we investigated how claim objectivity 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. A doctor makes the factual claim that “the measles vaccine prevented an estimated 56 million deaths between 2000 and 2021.” Another doctor might say something similar, but give an opinion instead of data: “I believe vaccination is an easy way to prevent unnecessary suffering.”

In our research, we tested this dynamic, using medical claims about a fictitious disease 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.

Crucially, this is not because opinions are simply “catchier” or easier to remember in general. Across all 13 of our experiments, we also measured “recognition memory” – the ability to remember that a statement was made at all. We found no consistent difference in recognition memory between facts and opinions. Participants remembered seeing factual claims and opinions equally well. However, they struggled to link the factual claims back to the correct source.

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Encoding the source

Why does this disconnect occur? Source memory is a form of associative memory. It relies on the brain’s ability to bind distinct components of an experience – what was said and who said it – into a coherent web of interconnected elements during the initial encoding of information.

We propose that the strength of this binding depends on one thing: what the claim 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 they know about legislative history. But if that same candidate says, “I believe shuttering USAID has been a moral catastrophe for our nation and the world,” we learn far more about them. We learn about their values, their priorities, and their stance on America’s role in the world.

Because opinions generally provide more information about the speaker than facts do, 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 when encoding opinions compared to facts, there is greater activation in the brain regions involved in theory of mind – the ability to represent the thoughts and mental states of others.

When we hear an opinion, we are building a richer mental model of the speaker. This additional social information strengthens the associative links formed during encoding.

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But what happens when opinions tell us nothing about a source? We tested this mechanism by presenting participants with book reviews. When participants believed the sources were the authors of the reviews, they remembered the sources of opinions far better than facts. However, when we told participants the sources were merely “re-tellers” reading randomly selected reviews, the source memory advantage for opinions disappeared, performing on par with facts.

We also tested source memory for facts that reveal something about a source, such as personal statements like “I was born in Virginia”. In these cases, source memory was just as accurate as it was for opinions like “chocolate ice cream tastes better than vanilla”. It was also more accurate than for general facts about the world, such as “Stockholm is the capital of Sweden”.

The visibility paradox

These findings present a major 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 the sources of important information.

This may pose a problem for the credibility of information – in an age of rampant misinformation and growing polarisation, remembering who said what is increasingly important to avoid conflict and ensure accuracy.

For experts, the goal is often to anchor facts in reality. Our research suggests that sharing opinions can help people to 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 that our brains need to more strongly bind the information to its source. While facts play an important role in the battle against misinformation, opinions may be just as critical – and they don’t go unnoticed.

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This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Daniel Mirny, IESE Business School (Universidad de Navarra)

This research was conducted in part thanks to the generous support of the UCLA Anderson Morrison Center for Marketing and Data Analytics.