President Donald Trump has just declared a national emergency after signing a bipartisan spending bill to fund the government and avoid another shutdown.

The national emergency declaration, which will allow Trump to bypass Congress and free up more money for border wall construction, comes more than a month after Trump first proposed the idea of using an emergency order to fund the wall that he said Mexico would pay for.

Just two days ago, Trump told reporters that construction of the border wall was already well underway. It is not. But now, he wants you to believe that he needs to declare a national emergency to build the wall that he just said was already being built.

Is your head spinning yet? No one could blame you for saying yes.

Our brains have limited cognitive resources, and Trump’s constant drumbeat of misinformation quickly overburdens our ability to effectively parse truth from fiction.

When evaluating information, our brains rely on mental shortcuts to help us form judgments and make decisions without having to stop and think about each step along the way. While these heuristics allow us to sort through the constant flow of information we encounter, they also leave us vulnerable to cognitive biases and poor decision-making.

Trump may not be a great dealmaker, but he is quite effective at tapping into these vulnerabilities and exploiting them to his benefit. No issue demonstrates this more clearly than immigration, and perhaps no event demonstrates this more clearly than the National Emergency declaration, which was issued in response to a crisis that doesn’t actually exist.

When Trump tells a lie, he tells it repeatedly. When he wanted people to believe that the border wall was being built, he returned to the claim on a near-daily basis, just like he peddles the same falsehoods about immigration and crime at all of his rallies.

Who could be running against Trump in 2020? Show all 23 1 /23 Who could be running against Trump in 2020? Who could be running against Trump in 2020? Joe Biden The former vice president - poised to be a frontrunner - has announced his run. He recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well AFP/Getty Who could be running against Trump in 2020? Bernie Sanders The 2016 runner-up has announced that he will be running again in 2020 Getty Who could be running against Trump in 2020? Hillary Clinton The 2016 Democratic presidential candidate and former Secretary of State says she is “still considering” whether she will run again. Getty Who could be running against Trump in 2020? Pete Buttigieg The Indiana mayor and war veteran will be running for president. If elected, he would be the first openly LGBT+ president in American history. Getty Who could be running against Trump in 2020? Kamala Harris The former California attorney general will be running for president in 2020. Introduced to the national stage during Jeff Sessions’ testimony, she has endorsed Medicare-for-all and proposed a major tax-credit for the middle class. AP Who could be running against Trump in 2020? Elizabeth Warren The Massachusetts Senator has formally launched her bid for president in 2020. A progressive Democrat, she is a major supporter of regulating Wall Street. AP Who could be running against Trump in 2020? Beto O’Rourke The former Texas congressman told Oprah Winfrey that he “has been thinking about running for presidency”, but stopped short of formally announcing his bid to run in 2020. AFP/Getty Who could be running against Trump in 2020? Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam has announced his bid. He intends to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord. Vice News Who could be running against Trump in 2020? Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege.” Getty Who could be running against Trump in 2020? Cory Booker The New Jersey Senator has announced that he will be running for the presidency in 2020. If he secures the nomination he said finding a female vice president would be a priority. Getty Who could be running against Trump in 2020? John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017. AP Who could be running against Trump in 2020? Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US. Getty Who could be running against Trump in 2020? Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but is likely to face tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad. Getty Who could be running against Trump in 2020? Andrew Yang The entrepreneur has announced his presidential candidacy, and has pledged that he would introduce a universal basic income of $1,000 a month to every American over the age of 18. AFP/Getty Who could be running against Trump in 2020? Marianne Williamson The author and spiritual advisor has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful. Getty Who could be running against Trump in 2020? John Kerry The former secretary of state has said he is still thinking about whether to run. Getty Who could be running against Trump in 2020? Michael Bloomberg The entrepreneur and former New York mayor– with a net worth of around $50bn – has said he will decide by the end of February whether to seek the presidency. AFP Who could be running against Trump in 2020? Howard Schultz Former Starbucks CEO Howard Schultz has not yet ruled out running for president in 2020, despite criticism that his bid could help re-elect Mr Trump by dividing the Democrat vote. AP Who could be running against Trump in 2020? Eric Holder The former attorney general has said he will decide in “the next month or so” whether to run as a 2020 presidential candidate. AP Who could be running against Trump in 2020? Eric Swalwell The California congressman said he is “ready to do this” and will decide before April whether to run. MSNBC Who could be running against Trump in 2020? Terry McAuliffe The former Virginia governor, who worked to elect Democratic governors during 2018 midterms, said there was a “50 per cent” chance he would run. AP Who could be running against Trump in 2020? Sherrod Brown The Ohio senator is still undecided about whether to run for president in 2020. Who could be running against Trump in 2020? Mitch Landrieu The former New Orleans mayor said he doesn’t think he will run for president, but “never say never”. AP Photo/Jacquelyn Martin

Even when we know the information we’re hearing is false, being exposed to the same statement repeatedly has been shown to increase its acceptance as true. This is due in part to a phenomenon known as the “illusory truth effect,” whereby people rate statements as more truthful and believable when they have encountered them previously than when they are new statements.

Unfortunately, the same effect makes us susceptible to repetition of any kind—including the restatement of false claims during the process of fact-checking. Yes, you read that correctly: The more times a falsehood is repeated, even for the purpose of refuting it, the more likely it is to be accepted as true.

Research also shows that people tend to perceive messages from multiple sources to be more credible than those from a single source. As a result, hearing the same thing from multiple people or groups increases the likelihood that it will be accepted as true, even if it’s not.

Trump has been able to tap into that vulnerability, too, thanks to the assistance of other members of his administration, as well as agencies like the Department of Homeland Security (DHS), which has repeatedly backed his false claims about new border wall construction.

Furthermore, because agencies like DHS are perceived as authoritative sources of information, hearing Trump’s lies repeated by such a source makes it more likely that the false claims will be accepted as true and passed along to others.

On top of that, messages that create emotional arousal like fear or disgust are far more likely to be passed on, whether or not they are true. It’s not a coincidence, in other words, that fear-mongering is a key feature at Trump’s rallies.

Finally, Trump’s supporters may be particularly susceptible to believing his lies because the falsehoods confirm pre-existing beliefs about immigrants, crime, and the need to do something about it.