Anyone can do a simple experiment. Navigate to a search engine that offers suggested completions for what you type, and start typing "scientists believe." When I did it, I got suggestions about the origin of whales, the evolution of animals, the root cause of narcolepsy, and more. The search results contained a long list of topics, like "How scientists believe the loss of Arctic sea ice will impact US weather patterns" or "Scientists believe Moon is 40 million years older than first thought."
What do these all have in common? They're misleading, at least in terms of how most people understand the word "believe." In all these examples, scientists have become convinced via compelling evidence; these are more than just hunches or emotional compulsions. Given that difference, using "believe" isn't really an accurate description. Yet all these examples come from searching Google News, and so are likely to come from journalistic outlets that care about accuracy.
Does the difference matter? A recent study suggests that it does. People who were shown headlines that used subjective verbs like "believe" tended to view the issue being described as a matter of opinion—even if that issue was solidly grounded in fact.
Fact vs. opinion
The new work was done by three researchers at Stanford University: Aaron Chueya, Yiwei Luob, and Ellen Markman. "Media consumption is central to how we form, maintain, and spread beliefs in the modern world," they write. "Moreover, how content is presented may be as important as the content itself." The presentation they're interested in involves what they term "epistemic verbs," or those that convey information about our certainty regarding information. To put that in concrete terms, “'Know' presents [a statement] as a fact by presupposing that it is true, 'believe' does not," they argue.
So, while it's accurate to say, "Scientists know the Earth is warming, and that warming is driven by human activity," replacing "know" with "believe" presents an inaccurate picture of the state of our knowledge. Yet, as noted above, "scientists believe" is heavily used in the popular press. Chueya, Luob, and Markman decided to see whether this makes a difference.
They were interested in two related questions. One is whether the use of verbs like believe and think influences how readers view whether the concepts they're associated with are subjective issues rather than objective, factual ones. The second is whether using that phrasing undercuts the readers' willingness to accept something as a fact.
To answer those questions, the researchers used a subject-recruiting service called Prolific to recruit over 2,700 participants who took part in a number of individual experiments focused on these issues. In each experiment, participants were given a series of headlines and asked about what inferences they drew about the information presented in them.
Beliefs vs. facts
All the experiments were variations on a basic procedure. Participants were given headlines about topics like climate change that differed in terms of their wording. Some of them used wording that implied factual content, like "know" or "understand." Others used terms that implied subjective opinion, like "believe" or "think." In some cases, the concepts were presented without attribution, using verbs like "are" (i.e., instead of "scientists think drought conditions are worsening," these sentences simply stated "drought conditions are worsening").
In the first experiment, the researchers asked participants to rate the factual truth of the statement in the headline and also assess whether the issue in question was a matter of opinion or a statement of fact. Both were rated on a 0–100 scale.
In the first experiment, participants were asked to rate both truthfulness and fact versus opinion for each headline. This showed two effects. One, using terms that didn't imply facts, like "believe," led to people rating the information as less likely to be true. Statements without attribution were rated as the most likely to be factual.
In addition, the participants rated issues in statements that implied facts, like "know" and "understand," as more likely to be objective conclusions rather than matters of opinion.
Climate headlines
Many of the experiments were focused on headlines related to climate change, and there was some good news here. People were generally better at recognizing headlines that contained misinformation about the climate.
The researchers also noted that right-wing news sources, which tend to cast doubt on the reality of climate change, were more likely to avoid language that implied the existence of facts, like "know" and "understand."
However, the design of the experiment made a difference to one of those outcomes. When participants were asked only one of these questions, the phrasing of the statements no longer had an impact on whether people rated the statements as true. Yet it still mattered in terms of whether they felt the issue was one of fact or opinion. So, it appeared that asking people to think about whether something is being stated as a fact influenced their rating of the statement's truthfulness.
In the remaining experiments, which used real headlines and examined the effect of preexisting ideas on the subject at issue, the impact of phrasing on people's ratings of truthfulness varied considerably. So, there's no indication that using terminology like "scientists believe" causes problems in understanding whether something is true. But it consistently caused people to rate the issue to be more likely to be a matter of opinion.
Opinionated
Overall, the researchers conclude that the use of fact-implying terminology had a limited effect on whether people actually did consider something a fact—the effect was "weak and varied between studies." So, using something like "scientists believe" doesn't consistently influence whether people think that those beliefs are true. But it does influence whether people view a subject as a matter where different opinions are reasonable, or one where facts limit what can be considered reasonable.
While this seems to be a minor issue here, it could be a problem in the long term. The more people feel that they can reject evidence as a matter of opinion, the more it opens the door to what the authors describe as "the rise of 'post-truth' politics and the dissemination of 'alternative facts.'" And that has the potential to undercut the acceptance of science in a wide variety of contexts.
Perhaps the worst part is that the press as a whole is an active participant, as reading science reporting regularly will expose you to countless instances of evidence-based conclusions being presented as beliefs.
PNAS, 2024. DOI: 10.1073/pnas.2314091121
