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LOS ANGELES — In the fight against climate denial, scientists have discovered an unexpected enemy: our own cognitive biases. A new study reveals how easily our minds can be tricked by the simple act of repetition.
Imagine scrolling through your social media feed and encountering a climate-skeptic claim that contradicts everything you know about global warming. You dismiss it, confident in your understanding of the science. But what if you saw that same claim again later? According to this new research, you might find yourself unconsciously viewing it as more credible, despite your strong pro-climate stance.
This phenomenon, known as the “illusory truth effect,” has been demonstrated across various domains. However, this study, led by Mary Jiang of The Australian National University, along with colleagues from the University of Southern California, specifically examined its impact on climate change beliefs.
The research team conducted two experiments, involving 52 participants in the first round and 120 in the second. The vast majority of these participants – about 90% – were believers in and supporters of climate science. They ranged from those merely “concerned” about climate change to those classified as “alarmed,” representing the highest level of engagement and worry about the issue.
Participants were presented with a mix of statements: some aligned with climate science, others reflected skeptic viewpoints, and some were unrelated weather claims. After a short delay, they encountered another set of statements, half of which were repeated from the first round. The task? Rate the truthfulness of each claim on a six-point scale.
The results, published in the journal PLOS ONE, were eye-opening. Regardless of the strength of their climate science convictions, participants rated all repeated claims as more truthful – even those that directly contradicted their beliefs. This effect persisted among the “alarmed” group, who held the strongest pro-climate science views.
“It could take as little as a single repetition to make someone feel as though a claim were true,” explains Norbert Schwarz, a study co-author and provost professor of psychology at USC, in a university release. “It’s certainly concerning, especially when you consider how many people are exposed to both truthful and false claims and either spread them or are persuaded by them to make decisions that might affect the planet.”
This vulnerability to repetition raises concerns about how climate information is communicated, especially in media environments striving for “balanced” coverage. Each repetition of a skeptical claim, even if presented alongside factual information, may incrementally increase its perceived truthfulness.
However, the study also highlights a potential silver lining. The power of repetition works both ways – accurate, science-based claims also became more believable with repeated exposure. This suggests that consistently repeating truthful information about climate change could help reinforce public understanding and acceptance of climate science.
“People find claims of climate skeptics more credible when they have been repeated just once,” says Jiang. “Surprisingly, this increase in belief as a result of repetition occurs even when people identify as a strong endorser of climate science.”
In light of these findings, researchers contend that the responsibility falls on both information consumers and producers to combat the spread of climate misinformation. Awareness of our cognitive biases is the first step towards building a more resilient, truth-oriented public discourse.
Paper Summary
Methodology
The researchers conducted two experiments with similar designs. Participants, primarily those who endorsed climate science, were shown a mix of climate-related statements. Some aligned with scientific consensus, while others reflected skeptical viewpoints. After a 15-minute delay filled with unrelated tasks, participants rated the truthfulness of all statements, including new ones they hadn’t seen before. In the second study, participants were also asked to categorize each claim as aligning with climate science or skepticism. This design allowed the researchers to measure how repetition affected perceived truthfulness for both types of claims.
Key Results
In both experiments, participants rated climate science-aligned statements as more truthful overall. However, repeated exposure increased the perceived truth of all statements, regardless of whether they aligned with or contradicted climate science. This effect was consistent across different levels of climate change concern, including among those most alarmed about climate issues. Even when participants could identify statements as coming from skeptics, they still rated repeated claims as more truthful than new ones.
Study Limitations
The study primarily included participants who endorsed climate science, with few climate skeptics in the sample. This limits the ability to generalize findings to those who are skeptical of climate change. Additionally, the research examined the effects of a single repetition over a short time frame. Further studies could explore how these effects persist over longer periods or with multiple repetitions.
Discussion & Takeaways
The study challenges assumptions about motivated reasoning, which suggests people primarily endorse information aligning with their existing beliefs. Instead, it shows that repetition can influence perceptions of truth even for counter-attitudinal information. This has important implications for climate communication, suggesting that repeating accurate information is beneficial while repeating false claims – even to debunk them – may inadvertently increase their perceived truthfulness.
“In short, this study emphasizes what we have learned over the years, and that is: We should not repeat false information. Instead, we must repeat what is true so that it becomes familiar and more likely to be believed,” Schwarz emphasizes.
Funding & Disclosures
The authors received no specific funding for this work and declared no competing interests. The study was approved by the Human Research Ethics Committee at The Australian National University.
