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Fake News and the Illusory Truth Effect

Research reveals how simply re-reading fake news makes it more convincing.

Source: igorstevanovic/Shutterstock

To say that we have access to an abundance of information is an understatement. For example, in 1995, there were 23,500 websites. In 2019, there are around 186 million—and we’re only talking about active sites. And let’s not even get started with how much Facebook has changed (well okay, we’ll go into it a little). From its creation in 2004, in 2019 in the United States alone, 69 percent of people use it, with most of those folks (74 percent) checking it out daily. And over 40 percent (43, to be exact) of people in the United States rely on Facebook for news updates. In other words, its reach is immense and frequent.

Understandably, it might be pretty tempting to think that most of us could mindfully sift through news stories and thoughtfully discern which ones have a foothold in reality and which ones are bogus. Yet research points to the sorry truth that we’re not quite as perceptive as we’d like to believe.

A team of psychological investigators conducted research on what makes fake news compelling. To define “fake news,” they drew from a definition in the journal Science, which describes it as "fabricated information that mimics news media content in form but not in organizational process or intent.” The researchers showed people headlines that had appeared on Facebook, some of which were truthful and some of which were fabricated.

Importantly, the investigators showed people some headlines (both factual and phony ones) once and others twice, with the goal of finding out whether people would find a headline more credible simply by having read it before. To prevent political bias in their study, they showed people an equal number of headlines that favored Democrats versus Republicans. And because the researchers wanted to examine whether a person’s political outlook would affect how they responded to headlines, they also assessed each person’s political viewpoints.

Now you might be wondering, “Why would researchers be interested in the impact of repetition on our tendency to trust statements in the first place?" It’s because of something that scientists have referred to as the “illusory truth effect,” which is our human tendency to find an assertion more compelling if we’ve come across it before. The reason why researchers generally believe this happens is because when we’ve perceived an idea or comment once, it takes less effort for our brains to grasp it when we encounter it again. And this greater bit of mental comfort we enjoy as we’re taking in an idea again leads us to treat it as more plausible.

There were two key findings from this research. First, even though we do see factual sentences as more believable than invented ones, the illusory truth effect nevertheless applies to sentences that are pretty unlikely, including the kinds of fictionalized headlines that appear in platforms such as Facebook. So even if a headline is cooked up, we’re apt to find it more believable just by having read it once before—and we don’t have to remember seeing it for the effect to happen.

Additionally, our political views don’t seem to matter either, as people in the study judged the false headlines they saw before as more convincing, regardless of whether those headlines fit their political beliefs or not. On top of that, fake news has some mental staying power. Even when the people in the study had seen the false headlines one week prior, they still found them to be more persuasive, no matter their political ideas.

So what does this mean for all of us as we encounter political headlines and information? The science on what we can do as individual consumers to protect ourselves from the influence of fake news is not yet entirely clear. One step may be in recognizing that not all sources of information are equal and consulting trustworthy outlets or sites that engage in careful fact-checking.

Another possible step comes from new research that's coming out in 2020, which suggests that we might want to pause when we read a headline and think about how it stacks up against the knowledge we already have. The researchers in this 2020 study showed people a series of false sentences and asked them to decide how valid they were, which interfered with the illusory truth effect. This worked by encouraging people to use information they already possessed as a guide in deciding whether to believe each sentence, rather than relying on how smooth it felt to mentally take in the information.

But it should be said that this only worked when people had knowledge they could recall and draw upon in the first place. As the study's authors noted, if we don’t already have information at our memory’s disposal, we may need to do the work (e.g., an online search) to seek it out, which can be challenging in daily life. You certainly don’t need me or anyone else to tell you that the hours of the day aren’t an infinite resource!

To summarize an argument that appeared in Science, countering the reach of fake news isn’t only up to us as consumers. It’s also likely going to require the willingness of platforms to actively work with independent researchers to more fully understand and improve their efforts to disrupt the promotion of falsehoods masquerading as legitimate news. Here’s hoping that will happen.

Thank you for reading.


Brashier, N. M., Eliseev, E. D., & Marsh, E. J. (2020). An initial accuracy focus prevents illusory truth. Cognition, 194, 104054.

Lazer, D. M., Baum, M. A., Benkler, Y., Berinsky, A. J., Greenhill, K. M., Menczer, F., ... & Schudson, M. (2018). The science of fake news. Science, 359, 1094-1096.

Pennycook, G., Cannon, T.D., & Rand, D.G. (2018). Prior Exposure Increases Perceived Accuracy of Fake News. Journal of Experimental Psychology: General, 147, 1865-1880.

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