by Hugo Mercier
truth. In the face of such motivations, open vigilance mecha-
nisms come to be used, perversely, to identify not the most
plausible but the most implausible views.
From the most intuitive to the most preposterous, if we want
to understand why some mistaken views catch on, we must un-
derstand how open vigilance works.
Uptake
At the end of the book, you should have a grasp on how you de-
cide what to believe and who to trust. You should know more
about how miserably unsuccessful most attempts at mass persua-
sion are, from the most banal— advertising, proselytizing—to
the most extreme— brainwashing, subliminal influence. You
should have some clues about why (some) mistaken ideas man-
in t r o d u c t i o n xix
age to spread, while (some) valuable insights prove so difficult
to diffuse. You should understand why I once gave a fake doctor
twenty euros.
I do hope you come to accept the core of the book’s argument.
But, please, don’t just take my word for it. I’d hate to be proven
wrong by my own readers.
1
THE CASE FOR GULLIBILITY
for millennia, people have accepted many bizarre beliefs
and have been persuaded to engage in irrational be hav iors (or
so it appears). These beliefs and be hav iors gave credence to the
idea that the masses are gullible. In real ity I believe the story is
more complicated (or even completely diff er ent, as we’ll see in
the following chapters). But I must start by laying out the case
for gullibility.
In 425 BCE, Athens had been locked for years in a mutually
destructive war with Sparta. At the Battle of Pylos, the Athenian
naval and ground forces managed to trap Spartan troops on the
island of Sphacteria. Seeing that a significant number of their elite
were among the captives, the Spartan leaders sued for peace, of-
fering advantageous terms to Athens. The Athenians declined
the offer. The war went on, Sparta regained the edge, and when
a (temporary) peace treaty was signed, in 421 BCE, the terms
were much less favorable to Athens. This blunder was only one
of a series of terrible Athenian decisions. Some were morally
repellent— kil ing all the citizens of a conquered city— others
were strategically disastrous— launching a doomed expedition
to Sicily. In the end, Athens lost the war and would never regain
its former power.
1
2 ch ap t er 1
In 1212, a “multitude of paupers” in France and Germany took
the cross to fight the infidels and reclaim Jerusalem for the Catho-
lic Church.1 As many of these paupers were very young, this
movement was dubbed the Children’s Crusade. The youth made
it to Saint- Denis, prayed in the cathedral, met the French king,
hoped for a miracle. No miracle happened. What can be expected
of an army of untrained, unfunded, disor ga nized preteens? Not
much, which is what they achieved: none reached Jerusalem, and
many died along the way.
In the mid- eighteenth century the Xhosa, a pastoralist people
of South Africa, were suffering under the newly imposed British
rule. Some of the Xhosa believed kil ing all their cattle and burn-
ing their crops would raise a ghost army that would fend off the
British. They sacrificed thousands of heads of cattle and set
fire to their fields. No ghost army arose. The British stayed. The
Xhosa died.
On December 4, 2016, Edgar Maddison Welch entered the
Comet Ping Pong pizzeria in Washington, DC, carry ing an as-
sault rifle, a revolver, and a shotgun. He wasn’t there to rob the
restaurant. Instead, he wanted to make sure that no children were
being held hostage in the basement. There had been rumors that
the Clintons— the former U.S. president and his wife, then cam-
paigning for the presidency— were running a sex trafficking
ring, and that Comet Ping Pong was one of their lairs. Welch was
arrested and is now serving a prison sentence.
Blind Trust
Scholars, feeling superior to the masses, have often explained
these questionable decisions and weird beliefs by a human dis-
position to be overly trusting, a disposition that would make the
masses instinctively defer to charismatic leaders regardless of
t he c a se f o r g ul l ib il i t y 3
their competence or motivations, believe what ever they hear or
read irrespective of its plausibility, and follow the crowd even
when doing so leads to disaster. This explanation— the masses
are credulous— has proven very influential throughout history
even if, as will soon become clear, it is misguided.
Why did the Athenians lose the war against Sparta? Starting
with Thucydides, chronicler of the Peloponnesian War, many
commentators have blamed the influence of demagogues such
as Cleon, a parvenu “very power ful with the multitude,” who was
deemed responsible for some of the war’s worst blunders.2 A
generation later, Plato extended Thucydides’s argument into
a general indictment of democracy. For Plato, the rule of the
many unavoidably gives rise to leaders who, “having a mob
entirely at [their] disposal,” turn into tyrants.3
Why would a bunch of youngsters abandon their homes in the
vain hope of invading a faraway land? They were responding to
the calls for a new crusade launched by Pope Innocent III, their
supposed credulity inspiring the legend of the Pied Piper of
Hamelin, whose magic flute grants him absolute power over all
the children who hear it.4 People’s crusades also help explain the
accusations that emerged in the Enlightenment, by the likes of
the Baron d’Holbach, who chastised the Christian Church for
“deliver[ing] mankind into [the] hands of [despots and tyrants]
as a herd of slaves, of whom they may dispose at their
plea sure.”5
Why did the Xhosa kill their cattle? A century earlier, the Mar-
quis de Condorcet, a central figure of the French Enlighten-
ment, suggested that members of small- scale socie ties suffered
from the “credulity of the first dupes,” putting too much faith in
“charlatans and sorcerers.”6 The Xhosa seem to fit this picture.
They were taken in by Nongqawuse, a young prophetess who
had had visions of the dead rising to fight the British, and of a
4 ch ap t er 1
new world in which “nobody would ever lead a troubled life.
People would get what ever they wanted. Every thing would be
available in abundance.”7 Who would say no to that? Apparently
not the Xhosa.
Why did Edgar Maddison Welch risk jail to deliver non ex-
is tent children from the non ex is tent basement of a harmless
pizzeria? He had been listening to Alex Jones, the charismatic
radio host who specializes in the craziest conspiracy theories,
from the great Satanist takeover of Amer ica to government-
sponsored calamities.8 For a time, Jones took up the idea that
the Clintons and their aides led an organ ization trafficki
ng
children for sex. As a Washington Post reporter put it, Jones and
his ilk can peddle their wild theories because “gullibility helps
create a market for it.”9
All of these observers agree that people are often credulous,
easily accept unsubstantiated arguments, and are routinely talked
into stupid and costly be hav iors. Indeed, it is difficult to find an
idea that so well unites radically diff er ent thinkers. Preachers lam-
baste the “credulous multitude” who believe in gods other than
the preachers’ own.10 Atheists point out “the almost superhuman
gullibility” of those who follow religious preachers, what ever
their god might be.11 Conspiracy theorists feel superior to the
“mind controlled sheeple” who accept the official news.12 De-
bunkers think conspiracy theorists “super gul ible” for believing
the tall tales peddled by angry entertainers.13 Conservative writ-
ers accuse the masses of criminal credulity when they revolt,
prodded by shameless demagogues and driven mad by conta-
gious emotions. Old- school leftists explain the passivity of the
masses by their ac cep tance of the dominant ideology: “The in-
dividual lives his repression ‘freely’ as his own life: he desires
what he is supposed to desire,” instead of acting on “his original
instinctual needs.”14
t he c a se f o r g ul l ib il i t y 5
For most of history, the concept of widespread credulity has
been fundamental to our understanding of society. The assump-
tion that people are easily taken in by demagogues runs across
Western thought, from ancient Greece to the Enlightenment,
creating “po liti cal philosophy’s central reason for skepticism
about democracy.”15 Con temporary commenters still deplore
how easily politicians sway voters by “pander[ing] to their gull-
ibility.”16 But the ease with which people can be influenced has
never been so (apparently) well illustrated as through a number
of famous experiments conducted by social psychologists since
the 1950s.
Psychologists of Gullibility
First came Solomon Asch. In his most famous experiment he
asked people to answer a simple question: Which of three lines
(depicted in figure 1) is as long as the first line?17 The three
lines were clearly of diff er ent lengths, and one of them was an
obvious match for the first. Yet participants made a mistake
more than 30 percent of the time. Why would people provide
such blatantly wrong answers? Before each participant was
asked for their opinion, several participants had already re-
plied. Unbeknownst to the actual participant, these other par-
ticipants were confederates, planted by the experimenter. On
some trials, all the confederates agreed on one of the wrong
answers. These confederates held no power over the partici-
pants, who did not even know them, and they were providing
plainly wrong answers. Stil , more than 60 percent of partici-
pants chose at least once to fol ow the group’s lead. A textbook
written by Serge Moscovici, an influential social psychologist,
describes these results as “one of the most dramatic illustra-
tions of conformity, of blindly going along with the group, even
6 ch ap t er 1
A
B
C
Figure 1. The lines in the Asch conformity experiments. Source: Wikipedia.
when the individual realizes that by doing so he turns his back
on real ity and truth.”18
After Solomon Asch came Stanley Milgram. Milgram’s first
famous study was, like Asch’s experiments, a study of conformity.
He asked some of his students to stand on a sidewalk, looking
at a building’s win dow, and counted how many of the people
passing by would imitate them.19 When enough students were
looking in the same direction— the critical group size seemed
to be about five— nearly all those who passed by followed the
students in looking at the building. It was as if people could not
help but follow the crowd.
But Milgram is best known for a later, much more provoca-
tive experiment.20 In this study, participants were asked to take
t he c a se f o r g ul l ib il i t y 7
part in research bearing ostensibly on learning. In the lab, they
were introduced to another participant— who, once again, was
actually a confederate. The experimenter pretended to randomly
pick one of the two— always the confederate—to be the learner.
Participants were then told the study tested whether someone
who was motivated to avoid electric shocks would learn better.
The learner had to memorize a list of words; when he made a
mistake, the participant would be asked to administer an elec-
tric shock.
The participants sat in front of a big machine with a series of
switches corresponding to electric shocks of increasingly high
voltage. The confederate was led slightly away, to an experimen-
tal booth, but the participants could still hear him through a
microphone. At first, the confederate did a good enough job
memorizing the words, but as the task grew more difficult, he
started making mistakes. The experimenter prompted the par-
ticipants to shock the confederate, and all of them did. This was
hardly surprising, as the first switches were marked as deliver-
ing only a “slight shock.” As the confederate kept making
mistakes, the experimenter urged the participants to increase the
voltage. The switches went from “slight shock,” to “moderate
shock,” then “strong shock,” and “very strong shock,” yet all the
participants kept flipping the switches. It was only on the last
switch of the “intense shock” series—300 volts— that a few par-
ticipants refused to proceed. All the while, the confederate ex-
pressed his discomfort. At some point, he started howling in
pain, begging the participants to stop: “Let me out of here! You
can’t hold me here! Get me out of here!”21 He even complained
of heart prob lems. Yet the vast majority of participants kept
going.
When the “extreme intensity shock” series began, a few more
participants stopped. One participant refused to go on when the
8 ch ap t er 1
switches indicated “danger: severe shock.” At this stage, the con-
federate had simply stopped screaming and was begging to be
freed. He then became completely unresponsive. But that didn’t
stop two- thirds of the participants from flipping the last two
switches, 435 volts and 450 volts, marked with an ominous
“XXX.” Milgram had gotten a substantial majority of these or-
dinary American citizens to deliver (what they thought to be)
potentially lethal electric shocks to a fellow citizen who (they
thought) was writhing in pain and begging for mercy.
When learning of these results, and of a litany of historical
cases seemingly attesting to similar phenomena, it is hard not to
agree with the sweeping indictment leveled by po liti cal phi los-
o pher Jason
Brennan: “ Human beings are wired not to seek truth
and justice but to seek consensus. They are shackled by social
pressure. They are overly deferential to authority. They cower
before uniform opinion. They are swayed not so much by rea-
son but by a desire to belong, by emotional appeal, and by sex
appeal.”22 Psychologist Daniel Gilbert and his colleagues con-
cur: “That human beings are, in fact, more gullible than they are
suspicious should prob ably ‘be counted among the first and most
common notions that are innate in us.’ ”23
If you believe that humans are by nature credulous, the natu-
ral question to ask is: Why? Already in 500 BCE Heraclitus, one
of the first recorded Greek phi los o phers, was wondering:
What use are the people’s wits
who let themselves be led
by speechmakers, in crowds,
without considering
how many fools and thieves
they are among, and how few
choose the good?24
t he c a se f o r g ul l ib il i t y 9
Heraclitus was echoed twenty- five hundred years later in a less
poetic but more concise manner by this headline from the BBC:
“Why are people so incredibly gullible?”25
Adaptive Credulity
If social psychologists seem to have been bent on demonstrat-
ing human credulity, anthropologists have, for the most part,
taken it for granted.26 Many have seen the per sis tence of tradi-
tional beliefs and be hav iors as unproblematic: children simply
imbibe the culture that surrounds them, thereby ensuring its
continuity. Logically, anthropologists have devoted little at-
tention to children, who are supposed to be mere receptacles for
the knowledge and skil s of the previous generation.27 Critical
anthropologists have described the assumption that people
absorb what ever culture surrounds them as the theory of “ex-
haustive cultural transmission,”28 or, more pejoratively, as the
“ ‘fax model’ of internalization.”29
For all its simplicity, this model of cultural transmission helps
us understand why people would be credulous: so they learn the
knowledge and skil s acquired by generations of their ancestors.
Biologist Richard Dawkins thus explains the “programmed-in
gullibility of a child” by its “useful[ness] for learning language
and traditional wisdom.”30
While it is easy to think of “traditional wisdom” one would
