Post-Truth: The Dark Side of the Brain

A growing number of politicians are talking nonsense with impunity. False information is proliferating. What’s worse, the human brain loves it

It may seem surprising that after being elected president, Donald Trump continued to insist that the elections were rigged. Or that he accused his predecessor of having tapped his phone—without any proof. Or that one of his advisers claimed that the inauguration ceremony had shattered the record for attendance, which clearly it had not. But that would underestimate the new and baffling phenomenon of “post-truth,” of which Trump is the most striking example.

Post-truth triumphed the day after the U.K. voted in favor of Brexit. That’s when its defenders acknowledged that they had misled the public about the health care benefits of leaving Europe. It triumphed again when François Fillon’s center-right campaign for the French presidency rushed to exaggerate the number of supporters who turned out for a campaign rally in the Place du Trocadéro in Paris. And again when the Spanish government expressed pride in having strategically placed many researchers abroad in scientific collaborations, when in fact they had left as a result of relentless budget cuts. Further examples include the Turkish government, which complains of being censored in Europe—while imprisoning its journalists. And Russia, which supplies the whole world with dubious information through clever use of media propaganda.

Leaving aside politicians, “alternative facts” are created and disseminated at all levels. It is this planetary tsunami of false information that has driven many experts to refer to the era of “post-truth.” But what exactly is it? Derived from the title of a book published by journalist Ralph Keyes in 2004, the term achieved its 15 minutes of fame after being selected in 2016 as the Oxford Dictionaries Word of the Year. The Oxford Dictionaries defines post-truth as an adjective “relating to or denoting circumstances in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief.” This definition reflects a profound lack of confidence in the “legitimate” dispensers of facts (particularly the media and experts), making any truth, or any claim to the truth, suspect. Falsehood, in all its forms, thus takes on a routine character, becomes omnipresent and overwhelming, and enjoys virtually complete immunity. The sciences, unfortunately, are not spared, as shown by the climate controversy and the categorical rejection of vaccines by a segment of the population. Some people will even assert (as former NBA player Shaquille O’Neal did recently) that Earth is flat and defend their right to say it.

The term “post-truth,” however, is not without its detractors. Some observers point out that the phenomenon of disinformation has always existed and that, consequently, there is nothing new or “post” under the sun. Because when have we ever really known an “era of truth”? Or been perfectly and impartially informed? Or bothered to listen to points of view contrary to ours and argued solely on the basis of facts? Others dispute the idea that “truth” is even a relevant concept, given that it most often is left to certain dominant elites to determine what is false and what is true, according to their own interests.

The lack of consensus notwithstanding, there does seem to be something new about the current phenomenon. Many experts see it as the monstrous fruit of the encounter between our ancestral psychological propensities and technological progress.

In fact, our good old Homo sapiens brain is not as concerned with objectivity as one might think. Its priority is rather to safeguard its own regime of truth. The “argumentative theory of reasoning” of French researchers Hugo Mercier and Dan Sperber postulates that our very ability to reason is constrained and shaped by our need to be right and to convince. This explains our numerous errors of reasoning, which far from being anarchic or random, often stroke our ego. Thus, we more readily accept and retain information that suits us and that reinforces our beliefs—a tendency known as confirmation bias. According to a recent study by Jonas Kaplan of the University of Southern California and his colleagues, an entire cerebral network is involved in ego representation (called the default mode network). This network is activated when we receive information contrary to our political ideas, as if our very identity were being attacked.

In another study, Micah Edelson of the Weizmann Institute in Rehovot, Israel, and his colleagues showed that changing one’s mind depends on increased activity in a small region called the anterior lateral prefrontal cortex. Yet this activity is inhibited by the combined action of the amygdala and the hippocampus, or the centers of emotion and memory, respectively. The memories and beliefs recorded in our brain appear to have the power to prevent us from changing our mind, especially if they are emotionally laden.

Yet another factor—this one sociopolitical—is involved in maintaining false beliefs: economic progress goes hand in hand with a rise in individualism. This link was recently shown by Henri Santos of the University of Waterloo in Ontario and his colleagues. The researchers looked at data from 77 countries over 51 years, using behavioral criteria (such as the percentage of people living alone) and values associated with individualism (for example, using data from surveys assessing the importance of independence). In an individualist society, personal expression and forming opinions are highly valued. Truth and memory are thus perceived less as a common, shared legacy than in traditional societies and more as strictly sacrosanct, private goods.

Consequently, when partisans of François Fillon or Donald Trump believed they saw larger crowds than were truly present, their brain is blocking both the information that contradicts their beliefs and the brain regions that would allow them to change their mind. The sociopolitical context then reinforces their right to maintain their beliefs—a perverse outcome of what begins as a positive impulse, namely, to form an individual opinion.

But individual blindness is hardly the whole story. Another key characteristic of the era of post-truth is the way in which false information spreads. Here is where new technologies, and in particular social networks, come into play: the ability to share and disseminate makes it possible for any belief to turn into “information,” especially as the distinction between them tends to disappear. Walter Quattrociocchi and his team at the IMT School for Advanced Studies in Lucca, Italy, showed how Facebook amplifies the confirmation bias through its “personalized” algorithms. In fact, these algorithms lead to the creation of isolated communities that tend to become polarized, ones whose beliefs are reinforced and become ever more extreme.

A study done in 2017 shows how much our lack of ancestral concern for objectivity is reflected on social networks. Using functional MRI, researchers at the University of Pennsylvania analyzed the brain activity of subjects reading New York Times articles and then asked them to rate their likelihood of sharing the articles later. The question the researchers wanted to answer was: Does this brain activity predict whether information will become viral on social networks? By comparing the number of actual sharing generated by the article with the participants’ fMRI scans, the researchers concluded that this was indeed the case. The key was the activity of a “judgment system” comprising the ventral striatum and the ventromedial prefrontal cortex: the more these regions were activated during reading, the more success the article had on the Internet. The ventral striatum is involved in motivation and pleasure, and the ventromedial prefrontal cortex in self-representation and social cognition.

These results suggest that the choice of sharing an article is based on anticipating the reactions of others (“Will my social network like it and respond?”) and on the hope for increased personal prestige (being picked up and “liked” is a reward in itself that undoubtedly contributes to the success of social networks). It is not, however, based on the veracity of the information.

Consequently, even information that is false spreads. Conditions seem ripe for a threshold effect: drowning in a mess of falsehoods and vagaries, the truth loses all prescriptive power to lay out a course of action. This is an unprecedented situation that leaves observers perplexed. How can we fight against post-truth when there is no recognition of the difference between objective reality and personal opinion? Fortunately, remedies are at hand: never before have we seen so much analysis and fact-checking. Even sales of 1984 by George Orwell, a forerunner in the denunciation of disinformation, are surging.

But to what effect? Unfortunately, post-truth possesses formidable self-defense mechanisms. Disseminating corrective updates, however factual they may be, often reinforces false information, simply because it is thus repeated and propagated. Attacking an alternative fact also gives it weight, making it more credible and memorable than it deserves. Another difficulty arises from the fact that “official” sources evoke a certain degree of mistrust. Vaccination campaigns therefore tend to reinforce the hostility of people who oppose vaccines—in other words, precisely those whose behavior should be changed (the so-called boomerang effect). Why? Because they feel that their convictions are being attacked, one of which is that an unnamed “they” seeks to silence them by any means.

Worse, a recent study shows that even if we succeed in changing false beliefs, this does not guarantee a change in behavior. Briony Swire of the Massachusetts Institute of Technology and her collaborators interviewed subjects of all political stripes during the presidential campaign of 2016, before Trump was elected. They were asked to rate whether the billionaire’s statements were true or false. Not surprisingly, Trump’s supporters were more likely to believe them. After they were presented with corrections of objectively false statements, however, an amazing thing happened: participants reduced their belief in the falsehoods, regardless of the source of the explanation—whether from a pro- or anti-Trump expert—but they did not change their voting preferences.

In short, all signs indicate that we expect to be lied to and that deep down many of us find it normal or hardly realize it. As the authors concluded, “Something other than the truth [of his statements] accounted for his success.”

In principle, being directly contradicted by the facts should create a form of dissonance, an uncomfortable cognitive state that must be resolved one way or another, at the very least by acknowledging bad faith—basic postulates of a theory put forward by psychologist Leon Festinger in the mid-1950s. Here, too, we may be looking at an unprecedented phenomenon deserving of study: post-truth could be killing cognitive dissonance, which had the virtue at least of signaling some kind of incoherence.

How, then, are we to resist? Tried-and-true methods are obviously of paramount importance: to reestablish truth in all circumstances, to gain confidence by being rigorous and impartial, to teach critical thinking at school. Yet perhaps the truth is ill equipped to win this battle alone. Perhaps it is also worth rehabilitating fiction by invoking its distinctiveness: after all, “post-truth” could well imply a “post-fiction” world. Today the boundaries are blurred: Trump was, after all, a champion of reality TV, the genre that introduced the idea that one could film unscripted day-to-day life and live a fairy tale. In this context, Françoise Lavocat, professor of comparative literature at the New Sorbonne University, Paris, advocates reestablishing a clear distinction between truth and fiction. As a species, we are particularly fond of stories. Of that there is no doubt. But it only increases the urgency of resolving to defend truth and facts. We are at a critical juncture. It may never be more important to make the most of our extraordinary ability to invent alternative worlds and to learn to enjoy them without confusing them with reality.

• Many political leaders have recently taken to making fanciful statements. These assertions combine with the mass of false information circulating on the Internet and influence public opinion. People no longer seem to care about objective reality. We have gotten to the point where experts now refer to the era of post-truth.

• Although “truth” is discussed all the time, it has never had as little currency as it does now. Researchers explain this development as the product of our ancestral brain encountering modern individualism and new technologies. Studies show that what we find interesting about information is not so much its veracity as the social prestige it brings, especially on social networks.

• The phenomenon is difficult to control because it is armed with formidable mechanisms of self-defense. But fact-checking and education in critical thinking initiatives must continue to develop. We may also need to rehabilitate fiction, emphasizing its capacity to give us pleasure without needing to make it into reality.


Sebastian Dieguez is a postdoctoral researcher in cognitive neuroscience in the Laboratory of Cognitive and Neurological Sciences at the University of Fribourg in Switzerland. This article originally appeared in Cerveau & Psycho.

Dieguez, S. (2017). Post-Truth: The Dark Side of the Brain. Scientific American Mind, 28(5), 43-48.


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