Communicating scientific uncertainties can weaken support for public policies, study finds

Study with over 1,100 participants finds that a lack of scientific consensus affects support for regulatory policies on microplastics

Editorial staff

Black-and-white photograph of an elderly man sitting in a subway car, reading a newspaper that covers his face. In the background, other passengers appear out of focus in their seats. It is an everyday urban setting.

Uncertainty is part of the scientific process, but communicating it to the public is often challenging. It can be toned down or omitted for the sake of clarity and to avoid unintended effects, such as loss of credibility or confusion.

A study conducted by researchers in Austria, Norway, and the Netherlands investigated whether, and to what extent, communicating scientific uncertainties influences risk perception and support for policies related to the impacts of microplastics on human health. The findings, published in January in the journal Public Understanding of Science, indicate that revealing uncertainties or the lack of scientific consensus can slightly reduce risk perception and, consequently, support for regulatory measures by reducing the credibility of the message. The effects, however, are marginal.

How to communicate scientific uncertainties

1. Consensus uncertainty is the riskiest.: Informing the public that experts are divided can create room for denialist positions, unlike simply indicating a lack of data.
2. Credibility is the weakest link.: The reduction in support for public policies is not direct: it occurs through the loss of credibility of the message, which in turn lowers risk perception.
3. The profile of the public matters.: Those who already understand science as a process of open debate react differently—and more constructively—to the communication of uncertainties.
4. Transparency can be an asset.: Scientists who recognize the limits of their own knowledge tend to be perceived as more trustworthy, not less.
5. Effects are marginal, but real.: The impacts found are small—which does not mean they should be ignored, especially in contexts of high polarization or misinformation.

Methodology: three groups, one fictitious article

A total of 1,126 individuals aged 18 or older, all residents of Austria, participated in the study. They first answered questions about their knowledge and prior perceptions of the topic, as well as their beliefs and attitudes toward science. They were then randomly assigned to three groups: consensus uncertainty, deficit uncertainty, and a control group.

They all read a fictitious article, in the format of an online newspaper, about microplastics in food and beverages. The text explained what microplastics are, their main sources, and how they enter the food chain, as well as mentioning the benefits of using plastics in the food and beverage sector to provide a balanced perspective.

Next, the researchers presented all participants with a scientific study indicating that microplastics could have negative health effects. The difference was in the framing: the control group received no information about limitations or knowledge gaps; the consensus uncertainty group was informed that there were disagreements within the scientific community regarding the possible impacts; and the deficit uncertainty group received information about existing knowledge gaps and the need for further research.

Results: a small but significant effect

In general, communicating uncertainty led to a slightly lower risk perception in the two experimental groups compared with the control group, but the effect was small. The researchers found no statistically significant differences between the two types of uncertainty when compared directly.

By comparing each condition with the control group, they observed that only consensus uncertainty led to a statistically significant reduction in risk perception. The authors hypothesize that, unlike other types of uncertainty, consensus uncertainty signals that there are experts or evidence that challenge the original claim, which can create room for dissenting or denialist positions.

“Exposure to this type of uncertainty does not necessarily reduce support for public policies, but it affects the credibility of the message. This loss of credibility, indeed, reduces risk perception, one of the main factors sustaining support for policies,” the authors say.

The role of public beliefs

In addition to the characteristics of the message, the researchers analyzed how public beliefs and attitudes toward science are associated with the effects of communicating uncertainty. They observed that the participants who view science as a process of debate reported higher risk perception, regardless of the type of information they received.

“Our findings indicate that the characteristics of the public influence the effects of communicating uncertainty, but in a more complex and subtle manner than previously assumed,” the researchers note.

In this sense, the authors argue that promoting the view of science as a process of debate and strengthening trust in scientists can help the public deal in a more constructive way with topics marked by uncertainty, but which require preventive actions, as is the case with microplastic pollution.

“When scientists are transparent about the limits of their knowledge, they tend to be perceived as more intellectually humble—a characteristic associated with greater public trust and willingness to follow their recommendations,” the researchers state.

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