"I was totally against the war in Iraq. You can look at Esquire magazine from '04. You can look at before that."

Donald Trump made this statement at a forum on national security in New York City on September 7, 2016. It’s true that in an interview in _Esquire magazine more than a year after the war began, in August 2004, Donald Trump said some negative things about the Iraq war. Yet that is a very different thing from being “totally against the war in Iraq.” Following Trump’s words to look “before that” reveals that in a radio interview with Howard Stern before the war started, in September 2002, Trump was asked whether he supported the invasion of Iraq, to which Trump replied "Yeah, I guess so." Thus, Trump’s statement at the forum in 2016 was a lie.

From a political perspective, it is no mystery why Trump chose to lie in later years about whether and when he had supported or opposed the Iraq War. According to a Quinnipiac Poll in May 2015, about 59 percent of respondents believed that going to war in Iraq in 2003 had been the wrong thing for the US to do. Only 32 percent believed it was the right thing, with 8 percent not sure. By claiming that he was “totally against” the Iraq war, Trump used deception to appeal to the many anti-war voters.

Numerous media venues and fact-checkers, such as CNN, The Washington Post, The New York Times, Politifact, Los Angeles Times, Snopes, Politico, The Atlantic, and many others, called Trump out on this particular lie. After all, an important role of mainstream media is to serve as a referee in our public sphere. In this case, at least, they were performing that function, blowing the referee’s whistle when a high-profile lie on an important national issue came to light.

Yet instead of following the long-established “rules of the game” and backing down when caught, Trump doubled down on his deception. This was no one-time exception: it followed a pattern that’s characteristic of the political methods that are increasingly known, for rather obvious reasons, as “post-truth.”

On September 8th, 2016, the day after uttering his lie at the forum in New York City forum on September 7, 2016, Trump gave a speech in Cleveland where he said: “Iraq is one of the biggest differences in this race. I opposed going in and I did oppose it, despite the media saying no… I see the lies last night that Donald Trump was always in favor of the war in Iraq, and that’s why I have to do this, because the media is so dishonest, so terribly dishonest. I just had to set the record straight because there’s so much lying going on.”

This example was only one of many instances where Trump made false claims, and was called out by the media. In this as in other such cases, Trump responded not by withdrawing his false claims, but by attacking the media’s credibility. He did so through reinforcing his deceptive attacks on the media by repetition, as can be seen in the statement above, where he keeps calling the media dishonest without providing any additional evidence for his claim.

The Science of the Illusory Truth Effect

Why did Trump continue to lie even though he was again and again caught and condemned for doing so by the media? Trump’s strategy was every bit as effective, as it was dishonest and in bad faith. It relied for its impact on what behavioral science knows as the illusory truth effect. This flawed mental pattern causes our brains to perceive something to be true when we hear it repeated frequently and persistently, without additional evidence provided for the claim. In other words, just because something is repeated several times, we perceive it as more believable, regardless of whether it is objectively true or not based on evidence supporting it!

The illusory truth effect is well-supported by scientific research, as shown by an analysis of 51 academic studies on this phenomenon published in Personality and Social Psychology Review. Regardless of whether a statement is false or true, the more we hear it, the more likely we are to believe it. According to research by Hal Arkes, et. al., the illusory truth effect applies both to statements of minor importance, such as “some spiders have 12 eyes,” and to political and social evaluations, such as whether Trump “always opposed” the Iraq war or whether vaccines cause autism. All this was perhaps not news to leading propagandists over the years; but research shows that the illusory truth effect is shockingly powerful.

Perhaps the most troubling finding is that “Knowledge Does Not Protect Against Illusory Truth,” which is the title and topic of a peer-reviewed article published in the Journal of Experimental Psychology in 2015. Understandably, most scholars had previously assumed that the illusory truth effect resulted from people being unaware of factual reality. Yet the 2015 study demonstrated that repetition of falsehoods increased the perception of how true a claim is even for claims that people already knew were false.

In this study by Lisa Fazio et. al., participants rated 176 statements for truthfulness, using a scale labeled “1-definitely false, 2-probably false, 3-possibly false, 4-possibly true, 5-probably true, and 6-definitely true.” The experimenters found that some study participants correctly answered the question “What is the name of the short pleated skirt worn by Scots?” (a kilt). The subjects then rated the truth of the statement that a “sari is the name of the short pleated skirt worn by Scots,” giving it a low truth rating. Those subjects were then asked to read a number of statements, including that a “sari is the name of the short pleated skirt worn by Scots.” After some time passed, they were asked to again rate the truth of that statement. Surprisingly, despite knowing that the pleated skirt is called a kilt, not, a sari, they still rated the truth value of the statement as higher than they did initially.

Advertisers rely heavily on the illusory truth effect. Research published in the Journal of Advertising shows that the advertising industry motivates people to buy products by repeating the claimed benefits of a product, rather than by providing strong evidence that the product has the claimed benefits. For instance, commercials for cleaning detergents such as “Tide” do not focus on providing additional evidence of the product’s benefit, but simply repeating, a number of times, how well it works. The same pattern can be seen with any other commercials - because this is how our brain works. Moreover, the illusory truth effect is magnified by advertisements that prime consumers to trust their feelings, rather than their reason. In view of this, it’s no wonder that Trump encouraged his followers to rely on their instincts, as in a January 30, 2013 Tweet, where he proclaimed: “go with your gut.”

This phenomenon is not limited to politics and advertising: we see it in daily life all around us. For example, many parents will be familiar with the seemingly strange phenomenon that when kids (even teenagers) are caught in a deception, and are confronted about it, they will frequently keep lying. They will deny they lied, despite being confronted with clear evidence of the deception. They do so because they have learned over time that such tactics work well on the human mind, with parents sometimes starting to doubt themselves, and avoiding pressing onward.

More recently, the illusory truth effect has been studied in the specific context of fake news stories. Danielle Polage at Central Washington University ran an experiment where participants read fake news stories, which the researchers depicted as true. After five weeks, these same participants were tested again by reading the same fake stories. Not surprisingly, these repeat participants rated the stories as more truthful than participants who read the fake stories for the first time.

Additionally, some repeat participants formed false memories about the stories’ origins, forgetting that the stories originated from the experiment. Thus, repeating fake news stories not only leads people to perceive these stories as true; it can also obscure in their minds the original source of the stories. For example, people might misremember that they learned about a news story through a social network, which are notoriously plagued by fake news, and believe the story came from watching the more credible nightly news on TV.

This drastic impact of the illusory truth effect relates, in large part, to processing fluency, a concept referring to how easily our minds process information. The more often we hear a statement, the less effort it takes to process it. The less effort it takes to process, the more comfortable with it we become. The more comfortable we become, the more truthful the statements seems to us on a gut level. Again we find that the problem stems from a fundamental mistake our brains tend to make, of equating truth with comfort.

Trump’s Illusory Truths

Given Trump’s background in marketing and advertising, it’s plausible that he is consciously aware of the illusory truth effect. However, whether consciously or not, he certainly took keen advantage of this hard-wired error in people’s thinking.

Trump’s post-truth political approach was dominated by combining repetition and deceit to his advantage. Another example is given by Trump’s deceptive statement, in the first presidential debate with Hillary Clinton, that the North American Free Trade Agreement (NAFTA) “is the worst trade deal maybe ever signed anywhere, but certainly ever signed in this country.” Trump falsely claimed that NAFTA cost Americans millions of manufacturing jobs, saying that “go to new England, Ohio, Pennsylvania, you go anywhere you want, Secretary Clinton, and you will see devastation where manufacturing is down 30, 40, sometimes 50 percent.” As a political marketer, Trump aimed to appeal to the voters of the Rust Belt states - Ohio, Pennsylvania, Michigan, Wisconsin, and other manufacturing-oriented states - that have suffered from manufacturing automation and outsourcing.

Since that statement was made, his claims have been roundly disproved by prominent economists - people who have thoroughly studied NAFTA and know far more about its impact than Trump, or politicians in general. According to Alan Deardorff, an economist at the Gerald R. Ford School of Public Policy at the University of Michigan, "It's just nonsense to say NAFTA is responsible for the decline of manufacturing jobs in the U.S." The Congressional Research Service, a nonpartisan research arm of Congress, found in its research report that "NAFTA did not cause the huge job losses feared by the critics or the large economic gains predicted by supporters,” and that instead the "net overall effect of NAFTA on the U.S. economy appears to have been relatively modest," with overall a small and positive impact. Despite being condemned by mainstream newspapers, fact-checkers, economists, and non-partisan researchers for lying about NAFTA, Trump stubbornly repeated his claims, while attacking, with little appeal to fact, the media and experts who disputed his false claims.

Trump continued this pattern of behavior after winning the election: it was not solely for electoral advantage. On November 27, 2016, Trump Tweeted: “I won the popular vote if you deduct the millions of people who voted illegally.” He added in a subsequent Tweet that day: “Serious voter fraud in Virginia, New Hampshire and California - so why isn't the media reporting on this? Serious bias - big problem!” No evidence whatsoever exists to suggest that millions of people voted illegally. The political motivation for Trump to make this false claim stems from a desire to claim a political mandate to pass legislation. Clinton won the popular vote by nearly 3 million, undercutting Trump’s ability to claim that he represents the voice of the public. However, by positioning himself as the true winner of the popular vote, Trump - if successful in that deception - would give himself more leeway to shape public policy as President.

After being challenged to come up with evidence to support these claims, the Trump team failed to do so. Numerous media venues, such as CNN, The New York Times, Politifact, Slate, blew the whistle on Trump’s deception. Following his usual form, Trump simply denied that he lied, and continued to repeat his false claims, aggressively attacking anyone calling him out on his deception. He is doing so despite the fact that his lawyers, when filing a court case in Trump’s name opposing the recount efforts of former Green Party presidential nominee Jill Stein, stated that "All available evidence suggests that the 2016 general election was not tainted by fraud or mistake."

Trump is surrounding himself with allies who promote similar lies. For instance, we know that Trump’s pick for Attorney General has tried to suppress voting through prosecuting African-American activists for voter fraud, unsuccessfully, and more broadly promoting the false idea of widespread voter fraud among African-Americans and other minority groups. Moreover, he is using the powers of the Presidency to promote this lie, by launching an investigation into the alleged voter fraud.

Fortunately, some prominent Republicans also called out Trump on this lie. For instance, Speaker of the House Paul Ryan stated on January 25, 2017, that he has “seen no evidence” of mass voter fraud. In turn, Senator Lindsey Graham said on January 24, 2017 “I am begging the president, share with us the information you have about this or please stop saying it.”

Adding to his arsenal of deception, Trump also amplified and propagated fake news stories created by others. Trump boosted the false claim, entirely unsupported by evidence, that the hundreds of thousands of US citizens who protested his election were paid by Clinton backers. In November 10, 2016, Trump Tweeted that “professional protesters, incited by the media, are protesting. Very unfair!” Earlier, he also spread the false claim that many thousands of American Muslims were cheering on the terrorist attacks on New York on 9/11, a hoax spread by websites with a history of spreading politically-motivated fake news. At a 2015 rally in Birmingham, Alabama, Trump claimed that “I watched when the World Trade Center came tumbling down. And I watched in Jersey City, N.J., where thousands and thousands of people were cheering as that building was coming down." There is no record that any such event occurred. Jersey City local government authorities later stated that Trump’s claim was false, and indeed Trump had not been at Jersey City at all at the time. Nevertheless, Trump kept repeating his untruthful message relentlessly.

In another example of the same pattern of behavior Trump first gained significant political prominence as a leader of the “birther” movement, by repeating lies about President Obama allegedly being a secret Muslim, and not being born in the United States. These lies continued to gain credibility after Trump repeated them on well-known shows, such as Fox News’ “The O’Reilly Factor” on March 30, 2011.

The Effect of Illusory Truths

The available evidence shows that these bald-faced lies convinced a large portion of the population.

A mid-December 2016 Qualtrics poll showed that over half of Republican voters believed that Trump won not only the Electoral College vote, but also the popular vote. Mitigating this very bad news, the good news is that a college education helps guard against falling victim to the illusory truth effect: while 60 percent of Republicans without any college education believed that Trump won the popular vote, only 37 percent of Republicans with a college degree believed that lie.

Trump’s deceptive statements on NAFTA, among other lies about economic issues, also had a big effect on public beliefs. For instance, according to a poll by Public Policy Polling poll on December 9th, 2016, 67 percent of Trump voters wrongly believed that unemployment had increased during Barack Obama’s presidency. In reality, when Obama took office in January 2009, unemployment was at 8 percent and rising due to the crisis in the financial system in 2007-2008. By the time of the December 2016 poll, unemployment had dropped below 5 percent, but a huge reduction from 2009. Similarly, while the stock market gained 11.8 percent during the Obama Presidency, only 41 percent of those who voted for Trump were aware that the stock market went up. According to 39 percent of those who voted for Trump, the stock market had fallen during those years.

Although Trump and his team were not the original source of the false claim that Clinton supporters such as George Soros paid people to protest against Trump’s election, he and his team certainly helped spread this fake news story. The Public Policy Polling poll shows that a staggering 73 percent of Trump voters held the false belief that Soros made such payments, and only 6 percent were aware that it was false. In turn, evidence shows that a large number of people who care strongly about peace, and typically vote for the Democratic Party, supported Trump in this election because they received him as the anti-war candidate.

The Illusory Truth Effect Around the Globe

Trump’s actions are a case study in how post-truth politicians around the globe have exploited the illusory truth effect for their own gain.

Vladimir Putin claimed multiple times that protesters against his authoritarian government style in Russia were paid to do so, a strategy aimed to delegitimize them. During his December 15, 2011 annual televised question-and-answer session, he said the following about the widespread protests that followed the parliamentary elections, which international observers widely condemned as rigged: "I know that students were paid some money" to protest. He also attributed such payments to foreign powers, and placed blame on then-Secretary of State Hillary Clinton for these actions, as part of supposed American efforts to weaken Russia. Putin provided no evidence to support his oft-repeated claims, and the state-controlled media in Russia, unsurprisingly, did not challenge his assertions. Putin’s earlier tactic was echoed in and may well have helped inspire the false claims made by Trump and members of his administration that protesters against his election received payments from George Soros, a lie believed by the vast majority of Trump’s supporters.

Similarly, the “Vote Leave” campaign in the UK Brexit referendum repeated many claims, even after they were denounced as fake. One prominent example is the lie that the UK was sending £350 million per week to the European Union, and that this money would instead be going to the UK National Health Service if the “Vote Leave” campaign won. This campaign claim played a vital role in the “Vote Leave” message. It was painted on the side of the “Vote Leave” campaign bus. The political motivation behind this lie was a desire to convince voters that leaving the EU would enable the country to spend more of its money domestically, especially on health care. During the Brexit campaign, the statistics watchdog of the UK, known as the UK Statistics Authority, first privately conveyed to the “Vote Leave” campaign that this £350 million figure was false. After the “Vote Leave” campaign continued to use this deceitful number, the chair of the UK Statistics Authority, Sir Andrew Dilnot, in a very unusual move, made a public statement revealing that the “Vote Leave” campaign was “misleading and undermines trust in official statistics… The UK Statistics Authority is disappointed to note that there continue to be suggestions that the UK contributes £350m to the EU each week, and that this full amount could be spent elsewhere.”

Despite that strong rebuke, which was picked up and reported in numerous media venues, the “Vote Leave” campaign continued to repeat its lie. Showing the power of the illusory truth effect, a mid-June 2016 poll from Ipsos MORI found widespread belief in the false claim that £350 million per week went from the UK to the EU. Of respondents, 47 percent believed the claim, while only 39 percent recognized it as false.

The “Vote Leave” campaign repeated many other lies as well. For instance, “Vote Leave” posters claimed that “Turkey is joining the EU,” and that “the UK has no border controls whilst in the EU.” The political aim of these posters focused on appealing to anti-immigrant sentiment, which motivated many of the pro-leave voters. Both of these statements are demonstrably false. Despite newspapers and fact-checkers blowing the whistle, the “Vote Leave” campaign continued to make these false claims. While we have no polls on this topic, anecdotal evidence shows that many supporters of the “Vote Leave” campaign bought into these lies about immigration.

Breaking the Illusions of Illusory Truths

In the case of the Brexit campaign in the UK, the lies began to unravel soon after the “Vote Leave” campaign won. Shortly after the victory, “Vote Leave” leaders began to back away from the claim that £350 million per week would go to the National Health Service. Nigel Farage, one of the most prominent leaders of the “Vote Leave” campaign and leader of the UK Independence Party, gave an interview on Good Morning Britain immediately after the vote, where he said that promising to spend that money on the National Health Service “was one of the mistakes that I think the Leave campaign made."

They also began to back away from claims that there would be immigration from the EU after Brexit. Soon after the vote, another prominent “Vote Leave” advocate, Nigel Evans, told BBC radio that while the UK would have better control of immigration after leaving EU, the number of immigrants would not necessarily fall. Boris Johnson, another prominent “Vote Leave” advocate, wrote a piece in the Telegraph newspaper on June 26, 2016, after the “Vote Leave” campaign won, trying to reassure British people that they “will still be able to go and work in the EU; to live; to travel; to study; to buy homes and to settle down.” However, such rights for the British implied equivalent rights for EU citizens, thus undermining the claim that the UK would have less immigrants from the EU. There was, in reality, no possibility that UK citizens could in future have the rights in the EU that Johnson claimed, if EU citizens were not granted the same rights reciprocally in the UK.

Given these broken promises, it is not surprising that according to a poll taken by the British Election Study in October 2016, only 4 months after the vote, 6 percent of those who voted to leave expressed regret for their vote, and 4 percent were uncertain. Of those who voted to remain, only 1 percent regretted their vote, and 1 percent was uncertain. Yet the “Vote Leave” campaign already won the vote, and the results could not be changed. We see a similar pattern of broken promises with Trump.

After promising his supporters he would prosecute Hillary Clinton after becoming President, Trump renounced that commitment shortly after the election. In a November 22, 2016 interview with The New York Times, Trump stated “I don't want to hurt the Clintons, I really don't.” After Trump’s promises throughout his campaign to appoint a special prosecutor to investigate Clinton’s emails and the Clinton Foundation, his announcement came as a shock to many of his supporters. The conservative news website Breitbart, which serves as one of the leading proponents of Trump, and whose previous head Stephen Bannon is a prominent member of Trump’s administration, ran a story about Trump’s failure to keep his commitment with the headline "Broken Promise." The liberal news website Vox ran an op-ed “I voted for Donald Trump, and I already regret it,” whose author talked about how Trump’s backtracking on that promise “shook me to my core. I realized in that moment that I had voted for a demagogue. And it was sickening.” In the same interview, Trump signaled an openness to the idea that human actions might be contributing to climate change, despite denying this vigorously on the campaign trail. He also began to back away from his previous commitment to torture terrorism suspects. Of course, his voters have no way to go back and change their votes based on Trump’s reversals - no matter how much some of them might now regret their previous choice.

Conclusion

Combining the research on the illusory truth effect, with the evidence of its impact in the US election campaign, and on the UK Brexit referendum campaign, leaves little doubt that that intentional and systematic deception exploiting the illusory truth effect is disturbingly effective. Democracies around the world are vulnerable to post-truth politicians who will learn from the success of Trump and Brexit, and will exploit the illusory truth effect to achieve their goals. Many of those who will vote for these politicians will likely regret their decisions, after the broken promises become all too obvious, but would not have a way to turn back time.

How can we fight the abusive exploitation of the illusory truth effect in politics? First, we can promote a mental habit in ourselves and others of noticing, and highlighting to others, the repetition of claims that are not backed by factual evidence. Our emotions predispose us to be increasingly comfortable with such repeated claims, and as a result they will feel subjectively true, despite not being objectively true. By noticing such repetitions, we and others can be empowered to apply our own intentional reasoning to avoid being fooled.

This approach is informed by the broader research-based approach of de-anchoring, a method of combating false intuitions. The idea of de-anchoring is to push back against our subjective feelings when they steer us to evaluate reality inaccurately, and push back harder than seems intuitive to us, as we cannot trust our own intuitions, which are anchored toward comfort instead of reality.

Second, we can use the illusory truth effect against itself, and against those who abusively exploit it. By highlighting, repeatedly, the adverse consequences - sometimes grave ones - of buying into these lies, we can resurrect the credibility of the news sources that have been providing truthful information. Many UK citizens who voted to leave the EU because they believed that the UK National Health Service would get £350 million per week, or that immigration would decrease, came to regret their votes soon afterward. The same was true of a number of Trump voters who expressed outrage over him backing away from his promise to prosecute Clinton and make Mexico pay for the wall. Highlighting such negative outcomes can help encourage people to take seriously the dangers associated with allowing themselves to be abusively manipulated using the illusory truth effect.

References

Alice Dechêne, Christoph Stahl, Jochim Hansen, and Michaela Wänke. “The Truth About the Truth: A Meta-Analytic Review of the Truth Effect.”Personality and Social Psychology Review 14, no. 2 (2010): 238-257.

Hal R. Arkes, Catherine Hackett, Larry Boehm. “The Generality of the Relation Between Familiarity and Judged Validity.” Journal of Behavioral Decision Making 2, no. 2 (1989): 81–94.

Lisa K. Fazio, Nadia M. Brashier, B. Keith Payne, and Elizabeth J. Marsh. “Knowledge Does Not Protect Against Illusory Truth.” Journal of Experimental Psychology 144, no. 5 (2015): 993–1002.

Aparna Sundar, Frank R. Kardes, and Scott A. Wright. “The Influence of Repetitive Health Messages and Sensitivity to Fluency on the Truth Effect in Advertising.” Journal Of Advertising 44, no. 4 (2015): 375-387.

Polage, Danielle. “Making up History: False Memories of Fake News Stories.”Europe's Journal of Psychology 8. No. 2 (2012): 245–250.