Repetition boosts belief in climate-skeptical claims, even among climate science endorsers

Climate science supporters rated climate-skeptical statements as “truer” after just a single repetition, according to a study published in the journal PLOS ONE. The results held true even for the strongest climate science supporters surveyed.

What the researchers say: “Amidst the influx of content that a person consumes each day, the principle of motivated cognition suggests they are likelier to find truth in the statements that mirror their own beliefs,” the scientists explained. “However, a second phenomenon, the illusory truth effect, suggests that just one repeated exposure to an idea — regardless of what it is — can elevate its perceived validity.”

The researchers examined these ideas in the arena of climate science, questioning how self-identified climate science supporters might react when repeatedly exposed to climate-skeptical claims. Would repetition have an effect despite the conviction of their own beliefs?

The researchers fashioned two similar experiments, the first including 52 participants and the second 120. At least 90% of participants across both experiments endorsed climate science: the scientific evidence of human-caused climate change.

Participants reviewed a series of statements classified as climate-skeptical, climate-science, or weather-related filler statements. After 15 minutes, they reviewed a second series of claims, half of which were repetitions of the previous statements. They rated the claims from “Definitely True” to “Definitely False” on a six-point scale. In Experiment 2, the participants also classified each claim as scientist- or skeptic-aligned and defined their own climate views.

In the climate science endorsers, the repetition did increase perceived validity of all claim types — including the ones participants flagged retrospectively as antithetical to their own beliefs. This held true even for the strongest climate science supporters, those participants who self-identified as “Alarmed” by climate change.

These results reinforce the benefits of amplifying truth by repetition and the risks of spreading false information, the researchers write. They suggest that further studies include non-climate issues (e.g., immigration, education, healthcare, etc.), experiment with time spans and rounds of repetition, and invert the experiment to study how climate skeptics are affected by repetition of claims supporting climate science.

“People find claims of climate skeptics more credible when they have been repeated just once. Surprisingly, this increase in belief as a result of repetition occurs even when people identify as a strong endorser of climate science,” the lead author added.

So, what? Climate change is one of the six existential threats that we face (along with inequality, contagion (think mpox), unregulated generative AI, unregulated human genetic engineering and war). That only one repetition of disinformation can increase the danger of passivity in the face of threat is alarming. A larger, more comprehensive, study is urgently needed.