https://doi.org/10.1177/1745691618774270

Perspectives on Psychological Science

2018, Vol. 13(6) 770 –788

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DOI: 10.1177/1745691618774270

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PSYCHOLOGICAL SCIENCE

Conspiracy theories are omnipresent among members

of modern and traditional societies (West & Sanders,

2003). A common definition of conspiracy theory is the

conviction that a group of actors meets in secret agree-

ment with the purpose of attaining some malevolent

goal (e.g., Bale, 2007). Contrary to the view that belief

in such theories is pathological (Hofstadter, 1966), large

portions of the human population believe conspiracy

theories. In 2004, 49% of New York City residents

believed the U.S. government to be complicit in the

9/11 terrorist attacks (Sunstein & Vermeule, 2009). In

addition, in a nationally representative sample of the

U.S. population, 37% answered “agree” to the following

statement: “the Food and Drug Administration is delib-

erately preventing the public from getting natural cures

for cancer and other diseases because of pressure from

drug companies.” Another 31% answered “neither agree

nor disagree,” and only 32% disagreed with this state-

ment (Oliver & Wood, 2014). Belief in conspiracy theo-

ries is thus a widespread societal phenomenon and has

increasingly drawn the research attention of social sci-

entists (for overviews, see Brotherton, 2015; Douglas,

Sutton & Cichocka, 2017; van Prooijen, 2018). This

research focused predominantly on the direct, proxi-

mate mechanisms underlying conspiracy beliefs but

ignored the distal, evolutionary roots and functions of

such beliefs. The aim of the current contribution is to

fill this void.

We pursue the following more specific goals. First,

we conceptualize conspiracy theories and identify the

psychological mechanisms that interact to characterize

belief in such theories. Second, to assess the core ques-

tion of why conspiracy theories are widely believed, we

place the key findings of this growing research domain

774270PPS

XXX10.1177/1745691618774270van Prooijen, van VugtConspi

racy Theories

research-article

2018

Corresponding Author:

Jan-Willem van Prooijen, Department of Experimental and Applied

Psychology, VU Amsterdam, Van der Boechorststraat 1, 1081BT

Amsterdam, the Netherlands

E-mail: j.w.van.prooijen@vu.nl

Conspiracy Theories: Evolved Functions

and Psychological Mechanisms

Jan-Willem van Prooijen

1,2

and Mark van Vugt

1,3

Department of Experimental and Applied Psychology, VU Amsterdam;

The Netherlands Institute for the

Study of Crime and Law Enforcement (NSCR); and

Department of Politics and International Relations,

University of Oxford

Abstract

Belief in conspiracy theories—such as that the 9/11 terrorist attacks were an inside job or that the pharmaceutical

industry deliberately spreads diseases—is a widespread and culturally universal phenomenon. Why do so many

people around the globe believe conspiracy theories, and why are they so influential? Previous research focused on

the proximate mechanisms underlying conspiracy beliefs but ignored the distal, evolutionary origins and functions.

We review evidence pertaining to two competing evolutionary hypotheses: (a) conspiracy beliefs are a by-product

of a suite of psychological mechanisms (e.g., pattern recognition, agency detection, threat management, alliance

detection) that evolved for different reasons, or (b) conspiracy beliefs are part of an evolved psychological mechanism

specifically aimed at detecting dangerous coalitions. This latter perspective assumes that conspiracy theories are

activated after specific coalition cues, which produce functional counterstrategies to cope with suspected conspiracies.

Insights from social, cultural and evolutionary psychology provide tentative support for six propositions that follow

from the adaptation hypothesis. We propose that people possess a functionally integrated mental system to detect

conspiracies that in all likelihood has been shaped in an ancestral human environment in which hostile coalitions—

that is, conspiracies that truly existed—were a frequent cause of misery, death, and reproductive loss.

Keywords

conspiracy theories, evolutionary psychology, coalitions, adaptation, by-product

Conspiracy Theories 771

within the context of evolutionary psychology. Through

a synthesis of the empirical literature with theoretical

insights from evolutionary, social, and cultural psychol-

ogy, we put forward two rival hypotheses. The first,

called the by-product hypothesis, argues that conspiracy

theories are a by-product of a suite of cognitive mecha-

nisms (e.g., pattern perception, agency detection) that

evolved for different reasons. The second hypothesis,

which we label the adaptive-conspiracism hypothesis,

stipulates that conspiracy thinking is an adaptive feature

of the human coalitional mind that evolved (a) to alert

ancestral humans to the possibility that others were

forming dangerous coalitions against them and (b) to

stimulate appropriate actions to fend off such threats.

Finally, on the basis of our line of reasoning, we gener-

ate novel predictions about potential mediators and

moderators of conspiracy beliefs.

What Is a Conspiracy Theory?

Although the definition provided above is rather gen-

eral, here we explicate the specific underlying features

of conspiracy theories. We argue that a conspiracy

theory contains at least five critical ingredients. First,

conspiracy theories make an assumption of how peo-

ple, objects, or events are causally interconnected. Put

differently, a conspiracy theory always involves a

hypothesized pattern (see Shermer, 2011; Whitson &

Galinsky, 2008). Second, conspiracy theories stipulate

that the plans of alleged conspirators are deliberate.

Conspiracy theories thus ascribe intentionality to the

actions of conspirators, implying agency (Douglas,

Sutton, Callan, Dawtry, & Harvey, 2016; Imhoff &

Bruder, 2014). Third, a conspiracy theory always

involves a coalition, or group, of actors working in

conjunction. An act of one individual, a lone wolf, does

not fit the definition of a conspiracy theory (van

Prooijen & van Lange, 2014). Fourth, conspiracy theo-

ries always contain an element of threat such that the

alleged goals of the conspirators are harmful or decep-

tive (Hofstadter, 1966). Sometimes, people may suspect

others to conspire toward benevolent goals (e.g.,

secretly preparing a surprise party), but that is not how

conspiracy theories are commonly conceptualized.

Fifth, and finally, a conspiracy theory always carries an

element of secrecy and is therefore often difficult to

invalidate. Conspiracy theories that turn out true—such

as Watergate or the Iran-Contra scandal—are no longer

conspiracy “theories.” Hence, in judging the validity of

conspiracy theories, there is always room for error.

People hold many beliefs that share some of the key

elements of conspiracy theories, such as supernatural

beliefs. Indeed, conspiracy theories and supernatural

beliefs are positively correlated (Darwin, Neave, &

Holmes, 2011; Swami etal., 2011). What distinguishes

conspiracy theories from supernatural beliefs is that

they necessarily involve a coalition element of decep-

tive or potentially dangerous other human beings acting

in unison (Bale, 2007). If one sees a collection of non-

human stimuli grouped together—an unusually shaped

collection of trees, rocks, mountains, stars, or the like—

pattern perception and agency detection may provide

people with mystical experiences, spirituality, religious

revelations, and the desire to perform sacred rituals.

For conspiracy theories to occur, however, these non-

human stimuli need, at the very least, to be connected

to the real or suspected presence of a coordinated

group of deliberate actors. Unlike other forms of beliefs,

a hostile coalition is a prerequisite of any conspiracy

theory (van Prooijen & van Lange, 2014).

Browsing through the Internet, one can find many

lay theories that fit the key ingredients of a conspiracy

theory (patterns, agency, coalitions, threats, secrecy).

They usually involve powerful groups such as societal

leaders, governmental institutions (e.g., secret services),

influential branches of industry (e.g., oil companies,

the pharmaceutical industry), or stigmatized minority

groups (e.g., Muslims, Jews). Besides the context of

citizens’ perception of geopolitical events, conspiracy

theories emerge frequently in the microlevel setting of

organizations, as employees often suspect their manag-

ers of conspiring toward evil goals such as pursuing

their self-interest at the expense of employees and the

organization (van Prooijen & de Vries, 2016). Belief in

conspiracy theories is also common in non-Western

cultures; for instance, in rural parts of various African

countries (e.g., Mozambique, Nigeria, Tanzania), large

portions of citizens believe conspiracy theories that

involve malpractice of societal elites, sorcery or witch-

craft by enemy groups, and hostile Western plots (West

& Sanders, 2003). Furthermore, although the term con-

spiracy theory may sometimes be used to invalidate

legitimate accusations of corruption (for an example,

see Ferguson & Beresin, 2017), not all conspiracy theo-

ries are irrational. Recent history is replete with exam-

ples of actual conspiracies in politics (Watergate),

organizations (e.g., corporate corruption), and science

(e.g., the Tuskegee Syphilis Experiment).

Despite the variety of conspiracy theories, however,

belief in such theories seems to reflect one more gen-

eral conspiratorial mind-set. For instance, belief in one

conspiracy theory is an excellent predictor of belief in

different, unrelated conspiracies (Douglas & Sutton,

2011; Goertzel, 1994; Lewandowski, Oberauer, & Gignac,

2013; Swami etal., 2011; van Prooijen, Krouwel, & Pollet,

2015). Even mutually incompatible conspiracy beliefs—

such as the belief that Princess Diana staged her own

death and the belief that she was murdered—are

772 van Prooijen, van Vugt

positively correlated (.14 < rs < .26 in Wood, Douglas,

& Sutton, 2012). These insights suggest that although

there are many different conspiracy theories, belief in

such theories is grounded in the same underlying

psychology.

Conspiracy Theories as Evolutionary

By-Products

Evolutionary psychologists draw a distinction between

adaptations and by-products as different results of evo-

lutionary processes (Buss, Haselton, Shackleford,

Bleske, & Wakefield, 1998). Adaptations are functional

solutions to problems of survival and reproduction that

evolved through natural selection because they pro-

vided better survival prospects than alternative solu-

tions in ancestral environments. In contrast, by-products

do not solve adaptive problems and have no functional

properties but are carried along with other mechanisms

that do have adaptive features. For instance, the umbili-

cal cord evolved as a solution to the problem of provid-

ing nutrients from the mother to the fetus in her womb;

the belly button is a by-product of this adaptation and

carries no function in and of itself.

Likewise, it may be possible that conspiracy theories

are merely by-product beliefs. A crude version of the

by-product hypothesis suggests that conspiracy theories

are epiphenomena, emerging from a large brain capa-

ble of thinking, reasoning, and gossiping. The more

sophisticated version asserts that the mind consists of

various psychological mechanisms that evolved for dif-

ferent purposes. Recall that conspiracy theories contain

several key components, such as pattern recognition,

agency detection, and threat management. When

assessed separately, each of these mechanisms has

broader functionality than conspiracy detection. Jointly,

however, as by-products, they might cause humans to

be susceptible to conspiracy theories. Here we review

how these mechanisms are empirically related to belief

in conspiracy theories.

Pattern perception

One key element of any conspiracy theory is pattern

perception, an assumption about how people and

events are causally connected (Shermer, 2011; Whitson

& Galinsky, 2008). Pattern recognition is a basic feature

of an adaptive human ability for associative learning.

Understanding the world by identifying cause and effect

helped our ancestors to recognize threats and oppor-

tunities, to foresee the consequences of their actions,

and to strategically adjust their behavior to fit the

demands of the situation. Whereas many of the patterns

that people perceive are real and functional to internal-

ize (e.g., if one eats contaminated food, one might get

ill; if one hits an enemy, that enemy might hit back),

people sometimes mistakenly perceive patterns that do

not exist (Gilovich, Vallone, & Tversky, 1985).

Such illusory pattern perception is a result of the

evolved human tendency to make sense of the world

and, by extension, could produce a sensitivity to con-

spiracy theories. The human mind is equipped to look

for existing patterns because establishing the true

causal relations between people, events, and other

important stimuli is indispensable for survival. The

errors that may occur in this cognitive process—that is,

finding patterns that are in fact illusory—lead to all

kinds of seemingly irrational beliefs. For instance, para-

normal beliefs are associated with a decreased ability

to recognize randomness (for a review, see Wiseman

& Watt, 2006). The relationship between paranormal

beliefs and illusory pattern perception occurs only in

regular population samples, not in highly educated

samples of university students—which in all likelihood

is due to students’ relatively strong analytic-thinking

skills, which may override their intuitions (Blagrove,

French, & Jones, 2006).

Biases in pattern perception are empirically related

to conspiracy theories. For instance, people who believe

in conspiracy theories overestimate the probability that

events are connected (Brotherton & French, 2014). Fur-

thermore, belief in conspiracy theories is associated

with a tendency to perceive patterns in random or

chaotic stimuli, notably random coin flip strings and

unstructured modern art paintings (.22 < rs < .45 in van

Prooijen, Douglas, & De Inocencio, 2018; see also

Whitson & Galinsky, 2008). We should note, however,

that this relationship does not emerge under all circum-

stances (Dieguez, Wagner-Egger, & Gauvrit, 2015),

which may be (as with paranormal beliefs) due to sam-

pling differences (e.g., pattern perception might not

predict conspiracy theories among highly educated

people; see Blagrove etal., 2006). These findings sug-

gest that conspiracy theories may be a nonadaptive

consequence of biases in the evolved cognitive capacity

for pattern perception.

Agency detection

A second psychological mechanism that may produce

conspiracy beliefs is agency detection. Agency detec-

tion refers to humans’ evolved capacity to recognize

the motives and intentions behind others’ actions.

Agency detection is closely associated with theory-of-

mind adaptations—that is, the basic capacity to under-

stand what others are thinking and feeling (Baron-Cohen,

1997). Agency detection, as well as theory of mind,

enabled ancestral humans to understand the (benevo-

lent or hostile) motives behind each other’s actions and

thereby facilitated empathy with tribe members’ mutual

Conspiracy Theories 773

needs and desires, cooperation, and common norms of

conduct. Although agency detection evolved mainly to

regulate the social life of humans, sometimes people

detect agency where none exists. For instance, people

overattribute human motives and intentions to their

pets, plants, and electronic devices (i.e., anthropomor-

phism; Epley, Waytz, & Cacioppo, 2007).

Could a hyperactive agency-detection system pro-

duce conspiracy beliefs as a by-product? Conspiracy

theories assume evil schemes that are intentional and

planned in advance by a group of intelligent actors in

every single detail. Conspiracy theories thereby often

overestimate the power, evil intentions, and capacity of

foresight among the alleged conspirators and underes-

timate the role of accidents, human error, and chance

(e.g., Shermer, 2011). Various studies indeed support a

link between hyperactive agency detection and con-

spiracy theories. For instance, increased conspiracy

belief is associated with increased anthropomorphism

and with related measures assessing people’s tendency

to overascribe intentionality to inanimate objects (.16 <

rs < .42 in Douglas etal., 2016; Imhoff & Bruder, 2014).

Evidence further suggests that theory-of-mind mecha-

nisms predict conspiracy beliefs. Specifically, the ability

to read people’s emotions from their eyes predicts belief

in conspiracy theories, provided that there are threat

cues in the environment (van Prooijen & van Dijk, 2014).

As with pattern perception, agency detection

increases people’s sensitivity to many forms of belief.

Religious beliefs that involve anthropomorphized, mor-

alizing gods are grounded in people’s tendency to make

sense of their social and physical environment through

agency detection (e.g., Atran & Henrich, 2010). In addi-

tion, various other forms of supernatural belief—such

as belief in ghosts and the related belief in the ability

of living people to get into contact with the souls of

deceased people—imply agency detection (Shermer,

2011). Such agency detection can be increased by threat

cues. It has been noted that belief in moralizing, per-

sonified gods increases when people are uncertain

about the future (Hogg, Adelman, & Blagg, 2010). In

sum, when establishing the causes of events, people

have a tendency to detect agency, which may some-

times be accurate and sometimes not. Hyperactive

agency detection may facilitate conspiracy thinking as

a nonfunctional consequence.

Threat management

The by-product hypothesis suggests that conspiracy

theories are nonfunctional consequences of a threat-

management system. Evolutionary models emphasize

that people evolved adaptations to survive, stay healthy,

and reproduce despite the threats that were posed by

the physical and social environment. One implication

is that people have found ways to cope with stimuli in

their environment that pose a direct threat to their well-

being, health, and safety. Specifically, Neuberg, Kenrick,

and Schaller (2011) proposed that people possess a

threat-management system, which enables them to

quickly recognize threatening stimuli in their environ-

ment and cope with these stimuli through a functional

response. Neuberg and colleagues argue that this

threat-management system consists of two subsystems.

One is the disease-avoidance system, which is associ-

ated with cognitions, emotions, and behaviors that are

functional to avoid contact with dangerous pathogens.

The second subsystem is the self-protection system,

which is designed to quickly recognize and anticipate

direct threats to people’s physical integrity.

The threat management system manifests itself in

people’s responses to a range of potentially threatening

stimuli. For instance, people have an inborn fear of

various dangerous animals and quickly recognize them

in their environment. One study reveals that snakes and

spiders are more easily recognized, and more effec-

tively capture people’s attention, than flowers or mush-

rooms (Öhman, Flykt, & Esteves, 2001). Likewise,

people easily recognize angry human faces. This find-

ing is specific, however, to angry male faces, which is

consistent with the assertion that males’ expressions of

anger are stronger diagnostic cues than females’ expres-

sions of anger for possible physical danger to the per-

ceiver (Becker, Kenrick, Neuberg, Blackwell, & Smith,

2007). Besides the dangers of animals or human males,

another possible source of threat comes from poten-

tially hostile coalitions.

After recognizing cooperative alliances, people read-

ily associate such coalitions with danger. Studies reveal

that people more easily associate aversive, dangerous

stimuli with other groups (referred to as “out-groups”

in the psychological literature) as opposed to one’s own

group (e.g., Olsson, Ebert, Banaji, & Phelps, 2005).

Furthermore, danger-cues elicit increased vigilance par-

ticularly in the context of out-group men (McDonald,

Navarrete, & Van Vugt, 2012; Navarrete, McDonald,

Molina, & Sidanius, 2010). Likewise, a conditioned fear

response after associating human faces with unpleasant

stimuli (i.e., mild electric shocks combined with a short

burst of uncomfortable noise) was resistant to extinc-

tion only in the context of out-group male faces—not

in the context of male faces from one’s own group or

female faces (Navarrete etal., 2009). Human beings

have evolved to be vigilant toward all kinds of threats,

and conspiracy theories may be a by-product of this

threat-management system.

774 van Prooijen, van Vugt

Alliance detection

By definition, a conspiracy is a coalition of people

cooperating toward a common goal (Bale, 2007). For

people to detect conspiracies, therefore, they need to

be able to detect coalitions of people that cooperate

with one another. Consistently, evolutionary theorizing

asserts that people evolved an alliance-detection system

to quickly recognize coalitions of mutually cooperating

individuals (Kurzban, Tooby, & Cosmides, 2001). This

alliance-detection system is conceptually broader than

the assertion that people evolved a functional tendency

to believe conspiracy theories about enemy alliances:

The alliance-detection system also evolved to recognize

friendly alliances because these may help in providing

food, shelter, and mates (see also Pietraszewski, Cosmides,

& Tooby, 2014; Tooby & Cosmides, 1988). Nevertheless,

the capacity of human beings to detect which individu-

als are cooperating with one another constitutes an

indispensable element of their tendency to infer con-

spiracy theories when such alliances seem suspect or

dangerous. The by-product hypothesis asserts that as a

nonfunctional extension of human coalitional psychol-

ogy, people sometimes believe that hostile coalitions

are teaming up against them.

Empirical evidence suggests that people indeed auto-

matically detect cooperative coalitions. For instance, in

a political context, people spontaneously categorize

other people on the basis of their party preferences

(Pietraszewski, Curry, Petersen, Cosmides, & Tooby,

2015). Furthermore, cues suggesting that people coop-

erate with one another tend to override many other

salient perceptual cues that frequently form the basis

for social categorizations. A case in point is race:

Whereas in baseline conditions people have a tendency

to classify people according to differences in race, this

tendency is strongly reduced when additional cues sug-

gest interracial cooperative alliances (e.g., verbal alle-

giance cues such as “us” versus “them” or visual

appearance cues such as shared shirt color; see Kurzban

etal., 2001). In sum, people have mental modules in

place that enable them to quickly detect cooperative

alliances, both friendly and hostile ones.

Critical assessment

In the present section, we examined the possibility that

conspiracy theories are by-products of psychological

mechanisms—notably pattern perception, agency

detection, alliance detection, and threat management—

that evolved for different purposes. We have shown

theoretically and empirically that each of these mecha-

nisms is associated with a heightened sensitivity to

conspiracy theories. Does this mean that conspiracy

beliefs are merely epiphenomena, derived from these

evolved psychological mechanisms without having any

functional relevance per se?

We propose that the by-product hypothesis suffers

from one major weakness: Assuming that conspiracy

theories are a by-product of other adaptations implies

that conspiracies either do not exist or did not consti-

tute significant selection pressures influencing ancestral

humans’ genetic fitness. It is well known, however, that

conspiracies often do exist: Throughout history, people

formed coalitions that secretly planned to harm others

and subsequently carried out these plans. One might

reason that actual conspiracies in modern societies—

e.g., corporate corruption, or political conspiracies—often

have no straightforward influence on the reproductive

opportunities of individual citizens, who are shielded

from these power holders in large states and well pro-

tected by a strong rule of law. The central question for

the possible adaptive qualities of conspiracy theories,

however, is how actual conspiracies influenced the lives

of ancient hunter-gatherers during the millennia when

many of these psychological traits evolved. As such,

finding that basic psychological mechanisms facilitate

conspiracy beliefs does not preclude the possibility that

a predisposition to believe such theories is a functional

solution to a specific adaptive problem that humans

have faced throughout evolutionary history: the danger

of real conspiracies forming against them.

Adaptive-Conspiracism Hypothesis

We now explore the alternative hypothesis that believing

in conspiracy theories is an adaptive feature of the human

coalitional mind. The adaptive-conspiracism hypothesis

asserts that the human tendency to believe conspiracy

theories is not a by-product of (a) a large neocortex that

is capable of sophisticated reasoning or (b) psychological

mechanisms such as pattern recognition and agency

detection that evolved for different purposes. Instead,

conspiracy theories uniquely helped ancestral humans to

navigate their social world better and anticipate and over-

come imminent dangers in their environment. Specifi-

cally, we reason that in an environment in which

coalitional violence—that is, violence committed by

actual conspirators occurring both within and between

groups—was a common cause of death and reproductive

loss, it may have been adaptive for people to be suspi-

cious of the possibility that other people were forming

malevolent conspiracies against them or their group.

Detecting and possibly overrecognizing secret conspira-

cies before they strike may motivate a suite of emotional

and behavioral responses to mitigate such threats, includ-

ing taking defensive actions (e.g., migrating elsewhere)

or offensive actions (e.g., a preemptive strike).

Conspiracy Theories 775

Consistent with this line of reasoning, error-manage-

ment theory posits that human beings will be biased in

predictable ways when the costs of false positives are

unequal to the costs of false negatives. Although error-

management theory was initially developed to explain

male and female choices in sexual behavior and com-

mitment in close relationships (Haselton & Buss, 2000),

such an asymmetry also exists in the potential costs

associated with false positives and false negatives in

the context of threats that may exist in people’s physical

environment (Neuberg etal., 2011). Mistaking a stick

for a snake is relatively harmless in that it produces

only unnecessary avoidance behaviors. Mistaking a

snake for a stick, on the other hand, can be lethal.

We propose that the same logic applies to conspiracy

theories specifically, provided that the ancestral envi-

ronment contained sufficient dangerous coalitions to

render overrecognition of hostile conspiracies adaptive.

We depict the logic of error-management theory as

applied to conspiracy theories in Figure 1. Although

conspiracy theories are closely associated with coali-

tional conflict, one distinct feature of conspiracy theo-

ries is secrecy: Perceivers merely suspect a hostile

coalition preparing malevolent action. People may thus

make mistakes by over- or underrecognizing conspira-

cies. Although both types of mistakes involve certain

costs, error-management theory would predict that

underrecognizing conspiracies becomes more costly

(and overrecognizing conspiracies less costly) to the

extent that the dangers of real conspiracies increase.

More specifically, detecting a conspiracy where in

fact none exists may involve a range of possible costs,

including reputation damage, social exclusion, or harm-

ing innocent people that could be useful cooperation

partners. Many of these costs depend on a range of

social parameters, however: For instance, conveying

conspiracy theories has little reputational consequences

if a group majority is willing to believe in them. Fur-

thermore, although spreading false rumors may decrease

the social standing of an individual, social exclusion

would be a less realistic consequence in ancient hunter-

gatherer societies: A deviant group member also needed

to be considered harmful, or at least insufficiently ben-

eficial, to the group (Kurzban & Leary, 2001). Finally,

although in modern times conspiracy theories can carry

a social stigma (Harambam & Aupers, 2015), using the

label “conspiracy theory” does not decrease people’s

belief in it (Wood, 2016). This suggests that the possible

reputational consequences of conspiracy theories do

not discourage people from believing in them.

The costs of overrecognizing conspiracies are com-

plex because they depend on a range of social param-

eters, but the costs of failing to detect a conspiracy that

actually exists can be relatively straightforward. By

definition, actual conspiracies secretly plan to harm

people, for instance by stealing resources or women,

exploitation, raiding, killing, or, at the extreme, geno-

cide. Underrecognizing conspiracies may therefore

translate to major costs for victimized individuals or

groups. Balancing the trade-off between costs of over- and

underrecognizing conspiracies, we tentatively conclude

that, particularly in an environment in which dangerous

conspiracies are omnipresent, error-management theory

would predict an adaptive human predisposition to be

suspicious of possible conspiracy formation even when

this increases the chance of false positives. Put

differently, people err on the side of caution, thus

overrecognizing coalitional dangers through quick

mental calculations gauging the likelihood of hostile

conspiracies.

This line of reasoning would suggest that the psy-

chological processes underlying conspiracy theories are

an integral part of an adaptive human coalitional psy-

chology with the aim of detecting secret and dangerous

coalitions and assessing the costs and benefits of par-

ticular strategies to counter such threats (Tooby &

Cosmides, 2010). If this is true, then conspiracy theories

are reliably triggered by cues in the social environment

that—directly or indirectly—suggest a heightened risk

of coalitional aggression or exploitation. Once a con-

spiracy has been detected, people should then show

adaptive responses to deal with such secret and hostile

coalitions. In short, being suspicious of conspiracies

would have given early humans an edge in the competi-

tion over reproductive resources.

We argue for the adaptive nature of conspiracy

beliefs by evaluating the evidence for a number of

propositions that follow from the assertion that belief

in conspiracy theories is part of an adaptive human

coalitional psychology designed to deal with the real-

istic threat of coalitional violence among ancestral

humans. These propositions are based on common

requirements that a psychological mechanism must

meet to qualify as an adaptation, including its complex-

ity, universality, domain specificity, interactivity, effi-

ciency, and functionality (Schmitt & Pilcher, 2004). In

Conspiracy Detected

Conspiracy Not Detected

Conspiracy

Exists

Conspiracy Does

Not Exist

Correct Observation

False Negative

(Type II Error)

Consequence:

Possible Death

False Positive

(Type I Error)

Consequence:

Conspiracy Theory

Correct Observation

Fig. 1. Error-management theory in the context of belief in con-

spiracy theories.

776 van Prooijen, van Vugt

Table 1, we summarize the propositions and falsifiable

predictions that follow from these requirements if a

tendency to believe conspiracy theories indeed has

been an adaptive feature of ancestral humans.

Regarding the first criterion, a unique feature of a

psychological adaptation is its complexity: Adaptations

are typically complex and sometimes emerge as the

result of the interplay of traits that evolved for different

purposes but work together to deal with novel adaptive

challenges (also referred to as exaptations; see Andrews,

Gangestad, & Matthews, 2002; Schmitt & Pilcher, 2004).

A classic example is bird feathers, which initially

evolved for thermoregulation of the body but later on

obtained a new function, aiding in flight. Likewise, the

psychological mechanisms that we discussed earlier—

pattern perception, agency detection, alliance detec-

tion, and threat management—may have different

functionality than triggering conspiracy beliefs per se.

But once they are in place and working in combination,

natural selection may have contributed to the develop-

ment of a more specialized psychological mechanism

to recognize and manage true conspiracies. Thus, the

fact that these psychological mechanisms initially

evolved for different purposes does not preclude the

possibility that they were subsequently coopted into an

integrated functional system to detect conspiracies.

Indeed, our conceptual definition suggests that beliefs

qualify as conspiracy theories if—and only if—these

mechanisms operate in concert.

If conspiracy theories were adaptive for ancestral

humans, then susceptibility to such theories needs to

be universal among humans. Individual and cultural

variation may exist in the activation of conspiracy

thinking—as is the case with many psychological adap-

tations, from dangerous-animal-detection systems to

mate preferences (Buss, 2009)—but we should find

substantial evidence for conspiracy theorizing across

different human societies, from modern societies to

traditional, small-scale societies (Proposition 1: univer-

sality). In addition, we need to show that actual con-

spiracies were a major liability to the life, safety, and

reproductive opportunities of ancient hunter-gatherers.

Put differently, our model makes assumptions of char-

acteristics of the ancestral environment that would

allow a human psychology specifically designed to

detect and deal with conspiracies to evolve (Proposition

2: domain-specificity).

Furthermore, if susceptibility to conspiracy theories is

an adaptive feature of the human coalitional mind, it fol-

lows that humans must have evolved psychological

mechanisms to swiftly detect conspiracy formation in

their environment. For such a system to work, it must

respond appropriately to cues that were statistically asso-

ciated with the actual presence of dangerous conspiracies

Table 1. Requirements of Psychological Adaptations, Propositions for the Adaptive-Conspiracism Hypothesis, and

Predictions

Requirement Proposition Prediction

Complexity Conspiracy theories emerge from a specific

combination of coopted psychological

predispositions, notably pattern perception,

agency detection, alliance detection, and

threat management.

All four of these psychological predispositions are

empirically related to belief in conspiracy theories.

Universality Conspiracy theories are a universal

phenomenon among human beings.

Historical sources and cross-cultural research should

yield evidence of widespread conspiracy theorizing

among human populations across time and cultures.

Domain specificity Detecting actual conspiracies has given

ancestral humans an edge in survival and

reproduction.

Hostile coalitions (i.e., actual conspiracies) were a

meaningful selection pressure, and hence a frequent

cause of death, among ancestral humans.

Interactivity Specific or diffuse cues suggesting increased

risk for hostile coalitions activate the

conspiracy-detection system.

Perceived intergroup conflict, or socioenvironmental

cues associated with a likelihood of intergroup

conflict, predicts increased belief in conspiracy

theories.

Efficiency Conspiracy detection is rooted in a fast and

efficient mental system.

Belief in conspiracy theories emerges primarily

through System 1 thinking (i.e., heuristic, intuitive,

and emotional), not through System 2 thinking

(i.e., analytical).

Functionality People increase their chances of self-

preservation by removing the threat

associated with the hostile coalition.

Conspiracy theories lead people to display emotions

and behaviors designed either to avoid the

suspected conspiracy (e.g., fear and avoidance) or

to actively confront it (e.g., anger and aggression).

Conspiracy Theories 777

in ancestral environments. Put differently, people should

become more susceptible to conspiracy theories if con-

fronted with either specific (Proposition 3) or diffuse

(Proposition 4) cues suggesting coalitional dangers (i.e.,

interactivity). Moreover, conspiracy detection may be

expected to be a fast and efficient system. This would

imply that heuristic or intuitive thinking (System 1) and

not effortful, deliberative thinking (System 2) should be

associated with increased conspiracy beliefs (Proposition

5: efficiency). Finally, for conspiracy beliefs to be adap-

tive, they need to produce counterstrategies aimed at

dealing effectively with presumed conspiracies (Proposi-

tion 6: functionality). The adaptive-conspiracism hypoth-

esis is summarized in Figure 2. In the following, we

critically examine the evidence for each of these six

propositions.

Before reviewing the evidence, we should stress that

this model does not assert that conspiracy theories are

currently adaptive. The adaptive-conspiracism hypoth-

esis asserts that susceptibility to conspiracy theories

were functional in ancestral human environments in

which there may have been frequent, deadly conspira-

cies at work. That does not mean that conspiracy theo-

ries are of equal benefit to humans in complex, modern

societies. The fast and easy transmission of information

about bad events occurring far away—such as signs of

climate change in the Arctic or a plane crash in Colom-

bia—may set off the conspiracy-detection system even

when there is little evidence that such events actually

threaten a perceiver’s own welfare. Correspondingly, in

modern environments, perceiving conspiracies may

involve different costs and benefits than in ancestral

environments (e.g., different implications for one’s sta-

tus within a group). This idea, the mismatch between

small-scale ancestral environments and large-scale

modern environments (Li, van Vugt, & Colarelli, 2018),

suggests that although conspiracy thinking was func-

tional in an ancestral world, conspiracy theories may

no longer be adaptive, or may sometimes even be mal-

adaptive, in modern, complex environments in which

these conspiracy-detection mechanisms are misfiring.

Are conspiracy theories universal?

The first proposition pertains to the universality of con-

spiracy theories. The available evidence suggests that

conspiracy theories are not restricted to any particular

culture or time period. Although it is perhaps easier

nowadays to find or disseminate specific conspiracy

theories through the Internet, and conspiracy theories

may be subject to cultural transmission over the course

of generations (e.g., anti-Semitic conspiracy theories),

for the present purposes it is relevant to note that con-

spiracy theories have been widespread throughout

human history. For instance, during the times of the

crusades, persecution of Jewish people was frequently

inspired by the belief that there was a conspiracy

between Jews and Muslims to keep Christians out of

the Holy Land (e.g., Pipes, 1997). Even earlier, in 64

C.E., the great fire of Rome took place. A common

conspiracy theory among Roman citizens was that

emperor Nero and his loyal servants had deliberately

initiated the fire in order to rebuild the city according

to his own vision and that Nero was singing while Rome

was burning (Brotherton, 2015). Finally, many wars and

crimes against humanity were fueled by conspiracy

theories (Pipes, 1997).

Empirical research data support the view that con-

spiracy theories were common before people had

access to modern communication technologies. Uscinski

and Parent (2014) analyzed a total of 104,803 letters

sent to the New York Times and the Chicago Tribune

between 1890 and 2010 for conspiratorial content. The

conclusion that emerged from their data was that the

level of conspiratorial content in the letters was remark-

ably stable over time, which speaks against the asser-

tion that conspiracy theories are somehow characteristic

for our modern, digital society.

The vast majority of contemporary research on con-

spiracy theories has been conducted in Western societ-

ies, revealing substantial evidence for conspiracy

theorizing among ordinary, nonpathological citizens

(e.g., Oliver & Wood, 2014; Sunstein & Vermeule, 2009;

Inputs Conspiracy Detection Outputs

Speciﬁc and Diffuse Cues

Suggesting Dangerous Coalitions:

Underlying Psychological

Mechanisms:

• Pattern Perception

• Agency Detection

• Alliance Detection

• Threat Management

Approach-Oriented Responses:

• Anger

• Protest Behaviors

• Hostility and Aggression

• Radicalization

Avoidance-Oriented Responses:

• Fear

• Social Withdrawal

• Tailored Avoidance

• Intergroup Conﬂict

• Fear, Uncertainty, Distressing

Social Events

• Power Differences

• Individual Differences

Fig. 2. The adaptive-conspiracism hypothesis.

778 van Prooijen, van Vugt

Swami etal., 2011; van Prooijen etal., 2015). Yet con-

spiracy beliefs are not limited to Western cultures.

People from different cultures believe different con-

spiracy theories, of course, but evidence for substantial

conspiracy theorizing is found around the globe, such

as in Eastern Europe (Golec de Zavala & Cichocka,

2012), Indonesia (Mashuri & Zaduqisti, 2013), Malaysia

(Swami, 2012), various African countries (West &

Sanders, 2003), and the Muslim world within the Middle

East (Gentzkow & Shapiro, 2004). Thus far, no study

has managed to identify a culture in which conspiracy

beliefs are nonexistent.

Critical assessment

Are some cultures more susceptible to conspiracy theo-

ries than others? Our line of reasoning does not imply

that all individuals or cultures endorse conspiracy theo-

ries to an equal extent. Instead, we expect that the

susceptibility of individuals and cultures to conspiracy

beliefs varies with specific, recurrent cues that serve as

reliable inputs for conspiracy detection, such as the

presence of a sizeable, powerful enemy group that is

deemed to pose a threat to citizens’ well-being. Our

model would predict, on the basis of the interactivity

requirement (to be discussed later), that cultural differ-

ences in susceptibility to conspiracy theories exist, par-

ticularly in the context of coalitional violence,

exploitation, or other forms of intergroup conflict (e.g.,

warfare or civil unrest, high- vs. low-trust cultures,

variations in power distance between elites and masses).

A crucial question is whether conspiracy thinking is

also prevalent in small-scale hunter-gatherer societies,

which are arguably the best models of ancestral human

group life (Buss, 2015; von Rueden & van Vugt, 2015).

Ethnographic evidence indicates that conspiracy theo-

ries are highly prevalent among citizens of third-world

countries (West & Sanders, 2003), and anthropologists

have observed conspiracy theories among current

hunter-gatherers such as the Yanomamö (e.g., allega-

tions that a different tribe committed sorcery to harm

their tribe; Chagnon, 1988). Indeed, witchcraft beliefs

are common among traditional societies, and such

beliefs frequently combine superstition with conspiracy

theories (i.e., witchcraft is often assumed to be com-

mitted in secret, by members of enemy groups; West &

Sanders, 2003).

Nevertheless, we are not aware of research that has

systematically investigated conspiracy theories across

hunter-gatherer societies around the world. Such

research could more explicitly examine the costs and

benefits of believing conspiracy theories in such societ-

ies, the prevalence of conspiracy theories, and the spe-

cific contents of such theories. Quite plausibly, members

of hunter-gatherer societies assume relatively small

conspiracies (e.g., suspicions of enemy villages collud-

ing in secret) compared with citizens of large states

(e.g., grandiose theories of how government agencies

deceive the public). Even in the face of these qualitative

differences, however, we propose that all conspiracy

theories possess the same basic structure: suspicions

that a group of actors secretly colludes to commit harm.

How dangerous were actual

conspiracies in ancestral societies?

For conspiracy beliefs to be adaptive, the domain-

specificity requirement (Proposition 2) assumes that

actual and dangerous conspiracies constituted meaning-

ful selection pressures among ancestral humans. To

examine the validity of this assumption, we start with

the general observation that coalitions are inherent to

the social life of human beings and that coalitions

emerge both within and between human groups (Tooby

& Cosmides, 2010; Van Vugt & Kameda, 2013). Within-

group coalitions are a common feature of traditional

societies. Present-day hunter-gatherers frequently have

a reverse-dominance hierarchy in place that controls

the behavior of dominant individuals. Strong coalitions

keep overbearing individuals in check, and sometimes

they are punished (including death) or excluded

(Boehm, 1993). Coalitions are also formed for between-

group aggression—for example, to go on raids to kill

members of rival groups or steal valuable resources

(e.g., food, women). Coalitions also regulate the social

life of one of our closest genetic cousins, the chimpanzee.

Male chimpanzees sometimes join forces to depose the

alpha, thereby increasing their access to resources and

females. Likewise, coalitions are formed to go on border

patrols to attack members of other groups that encroach

on their territory (Wrangham, 1999).

One central motive for violent intergroup conflict in

humans is establishing dominance over rival groups.

Such intergroup dominance increases the fitness of the

individuals in the stronger groups at the expense of the

weaker group because it increases the dominant group’s

territory, its access to natural resources, and its mating

opportunities (McDonald et al., 2012). Another key

motive for violent intergroup conflict among hunter-

gatherers is revenge. They occasionally attack neighbor-

ing villages with revenge killing raids, inspired by, for

instance, sexual jealousy, revenge for lethal casualties

suffered in the past, allegations of sorcery, and long-

lasting conflicts (i.e., blood feuds) that escalated over

the course of generations (e.g., Chagnon, 1988). These

raids typically take the form of a surprise attack at dawn

by a group of 10 to 20 men, killing the first few inhabit-

ants of the enemy village that they encounter and then

Conspiracy Theories 779

retreating before the victimized group can get orga-

nized and fight back (see also Walker & Bailey, 2013).

As a consequence of this strategy, the risk for casualties

among the attacking coalition is relatively low.

How dangerous were actual conspiracies in ancestral

times? Although it is impossible to answer this question

with complete certainty, various sources of information

suggest that one of the most lethal acts that conspira-

cies can plan in secret—coalitional aggression and vio-

lence—may have been a common cause of death,

selecting for counteradaptations to fend off such threats.

One source of information stems from current hunter-

gatherer societies. In studies of the Yanomamö people

in the Amazon, between 22% of total deaths (Walker &

Bailey, 2013) and approximately 30% of all adult male

deaths (Chagnon, 1988) are reportedly due to coalition-

ary killing, usually in the form of violent raiding groups

attacking a neighboring Yanomamö village. Even more

violent are the Waorani people of Ecuador, where rates

of up to 64% of all deaths within the total population

(i.e., including men, women, and children) have been

ascribed to coalitionary killings—and 42% of all deaths

are caused by coalitions of Waorani killing other Waorani

(Beckerman etal., 2009).

Admittedly, the Waorani constitute a relatively

extreme case, and many foraging societies elsewhere

in the world are more peaceful. There is ongoing debate

among anthropologists regarding the exact level of vio-

lence in traditional societies (Fry & Söderberg, 2013;

Knauft, 1991). Nevertheless, death through coalitional

violence appears to be much more common in hunter-

gatherer societies than in modern societies. Walker and

Bailey (2013) conducted an ethnographic study among

11 traditional societies in South America and found that

an average of 30% of the adult population dies vio-

lently, the majority through raids and ambushes. Other

samples, ones that are not restricted to South America

but include traditional societies around the world, show

a somewhat more moderate picture; even in these data,

however, an average of 14% of the total population of

traditional societies worldwide dies through coalitional

violence (Bowles, 2009).

Of course, ethnographic analyses of contemporary

traditional societies should be interpreted with caution,

given that it is unclear how representative such societ-

ies are for the life of ancient hunter-gatherers. Bowles

(2009), however, compared findings among current

traditional societies using bioarcheology—the scientific

discipline that seeks to investigate the origins of human

behavior by analyzing the skeletal remains of fossilized

hunter-gatherers. The Bowles study reveals that 14% of

deaths within current traditional societies are due to

coalitional violence, and 14% of the skeletal remains

that were found at archeological sites show evidence

of death due to coalitional violence. The percentage

of violent deaths varies substantially per location, and

the prevalence of lethal intergroup conflict depends

on geographical and climatological factors that, for

instance, increase resource scarcity (Lambert, 2002).

These results are compatible with the anthropological

findings described above and suggest that although

the rates of coalitional killings varied widely in

ancient tribes around the world, on average, coali-

tional violence was a frequent cause of death (Van

Vugt, 2009).

For our present purposes, it is noteworthy that

Bowles (2009) calculated, using evolutionary simulation

models, that even in the face of high variability, these

killing rates are statistically sufficient to meaningfully

shape the process of natural selection. Put differently,

in this challenging ancestral environment, (groups of)

people that more effectively managed the dangers of

enemy coalitions would have better prospects of surviv-

ing and reproducing. Although this is often interpreted

as evidence for the evolved function of within-group

cooperation, it is also plausible that a tendency to be

suspicious of the formation of secret and antagonistic

coalitions—that is, conspiracies—could have evolved

in this context. Such a hyperactive conspiracy-detection

system could activate outputs, in terms of emotions or

behaviors that are functionally relevant for mitigating

such threats such as moving elsewhere, forming a coun-

tercoalition, or organizing a preemptive strike (see

Böhm, Rusch, & Gürerk, 2016; Van Vugt, De Cremer, &

Janssen, 2007).

Critical assessment

Any proposition about ancestral life necessarily has to

be examined with secondary sources of evidence, such

as current hunter-gatherers, nonhuman primate societ-

ies, or skeletal remains. This is an unavoidable limita-

tion of this part of our analysis. For instance, it is hard

to establish to what extent within-society versus

between-society coalitional violence (i.e., war) in

ancestral times contributed to the psychological basis

for conspiracy beliefs. Furthermore, anthropologists

have argued that many instances of violence in hunter-

gatherer societies might originate from personal dis-

putes instead of hostile coalitions (Fry & Söderberg,

2013). Personal disputes notwithstanding, however, a

substantial portion of violence among early humans

(Bowles, 2009) as well as chimps (Wrangham, 1999) is

likely due to coalitions, which is consistent with the

idea that conspiracy theories are grounded in an

evolved human coalitional psychology. In the following,

we more directly examine the role of coalitional and

intergroup conflict in conspiracy theories.

780 van Prooijen, van Vugt

Detection of dangerous coalitions

The third proposition is that conspiracy theories should

be strongly associated with recurrent cues that suggest

the realistic presence of a sizeable, powerful, and hos-

tile coalition. One recurrent feature would be inter-

group conflict. The present-day analogy of ancestral

coalitional violence is warfare. Pipes (1997; p. 179)

noted that most, if not all, contemporary wars are char-

acterized by strong mutual suspicion and conspiracy

theories about the enemy group on both sides of the

conflict. Moreover, he noted that conspiracy theories

are particularly characteristic for the extremist, totalitar-

ian regimes that our world has seen in the past century

and that have been responsible for a large portion of

the intergroup violence and killing in recent history.

Consistently, people at the ideological extremes are

more likely than moderates to believe conspiracy theo-

ries (Bartlett & Miller, 2010; van Prooijen etal., 2015).

Social-psychological theories have established two

complementary processes that characterize intergroup

conflict: Strong feelings of cohesion within one’s own

group, as reflected in nationalism and feelings that

one’s own group is superior compared with other

groups, and derogation of different groups, as reflected

in prejudice, hostility, and feelings of intergroup threat

(e.g., Tajfel & Turner, 1979). Both processes have been

associated with conspiracy theories in empirical

research. When a group is under threat, only people

who feel included in the group display increased belief

in conspiracy theories (e.g., van Prooijen, 2016; van

Prooijen & van Dijk, 2014). Furthermore, collective nar-

cissism—that is, the feeling that one’s own group is

superior—inspires conspiracy beliefs about a rival

group (Cichocka, Marchlewska, Golec de Zavala, &

Olechowski, 2016). In addition, studies conducted in

Indonesia reveal that identification with the Muslim

community predicts belief in the conspiracy theory that

the Western world introduced terrorism in Indonesia,

but only among participants who perceived Western

people as threatening to their Islamic identity (Mashuri

& Zaduqisti, 2013). Finally, major predictors of anti-

Semitism are the extent to which Jews are perceived as

threatening to the perceivers’ own country and, cor-

respondingly, belief in conspiracy theories about Jews

(Golec de Zavala & Cichocka, 2012). Taken together,

these findings support the idea that conspiracy theories

are triggered by the presence of powerful out-groups

in combination with a strong group identity (see also

Van Prooijen & Van Dijk, 2014).

The crucial role of intergroup conflict in activating

conspiracy theories is also suggested by research on

relatively powerless, vulnerable groups in society. Con-

sistent with the idea that conspiracy theories are an

adaptive response to the presence of formidable out-

groups, stigmatized minority groups have been found

to be highly susceptible to conspiracy theories. For

instance, African Americans are particularly likely to

believe conspiracy theories that involve a White plot

designed to harm or kill members of the African Ameri-

can community (e.g, Thorburn & Bogart, 2005). Belief

in these conspiracy theories is mediated by perceived

system blame—that is, the extent to which African

Americans attribute the problems that their community

faces to hostile intergroup behavior such as racism and

discrimination (Crocker, Luhtanen, Broadnax, & Blaine,

1999). Apparently, conspiracy theories flourish particu-

larly among cohesive minority groups that are marginal-

ized by the dominant majority coalition. These findings

are consistent with the idea that the existence of a

powerful group increases conspiracy theories among

members of competing, less powerful groups.

Finally, various individual difference-variables link

intergroup conflict to conspiracy theories. Many of the

cues that people encounter in everyday life are ambigu-

ous and may be interpreted in a hostile, neutral, or

benevolent manner depending on stable, internal dis-

positions (Buss, 2009). Thus, individuals who have a

predisposition to link ambiguous social cues to inter-

group conflict—such as social-dominance orientation

or right-wing authoritarianism—are more likely to

believe conspiracy theories. Various studies provide

qualified support for this prediction. Swami (2012)

found that both of these individual-difference variables

predicted belief in conspiracy theories about Jewish

people among Muslims in Malaysia. Abalakina-Paap,

Stephan, and Gregory (1999) found significant relations

of right-wing authoritarianism with belief in specific

conspiracy theories (e.g., about the Kennedy assassina-

tion, the United Nations, and the like), but not with

generalized conspiracy mentality, that is, a stable dis-

position to perceive a world full of conspiracies (see

also Imhoff & Bruder, 2014; Swami, 2012). The dispo-

sitional tendency to perceive intergroup conflict hence

predicts belief in conspiracy theories, but only insofar

as these conspiracy theories describe the specific threat

embodied by identifiable, powerful groups.

Critical assessment

Although the findings in the literature thus far provide

support for the prediction that conspiracy theories are

rooted in perceptions of intergroup conflict, future

research will need to complement these findings with

more sophisticated, preregistered research designs and

openly accessible data. For instance, at present no

study is investigating this prediction through a longitu-

dinal design using a pre- and postconflict measure of

Conspiracy Theories 781

conspiracy theorizing. Moreover, little is known about

the types of conflict that are most likely to instigate

conspiracy theorizing and whether different types of

conflict lead to different conspiracy theories. Although

intergroup conflict implying direct physical danger for

group members (e.g., war) stimulates conspiracy theories

about the antagonistic group (Pipes, 1997), so does con-

flict driven by ideological differences (e.g., Democrats

vs. Republicans; Uscinski & Parent, 2014). These consid-

erations suggest promising research challenges to further

establish the relationship between intergroup conflict

and belief in conspiracy theories.

Socio-ecological conspiracy cues

Our fourth proposition is that, besides direct intergroup

conflict cues, indirect, socio-ecological cues associated

with intergroup conflict also increase conspiracy beliefs.

In ancestral environments, intergroup conflict and

coalitional violence were particularly likely during peri-

ods of adversity, such as food scarcity or extreme cli-

mate conditions, such as droughts or floods (Lambert,

2002). Such resource-threat cues may increase vigilance

toward the possibility of coalitional dangers, in the form

of conspiracy theories. In modern environments, threat-

ening societal circumstances—such as floods or fam-

ines—still increase the likelihood of intergroup conflict

(Hogg, 2007; Tajfel & Turner, 1979). These propositions

are consistent with the insight that conspiracy theories

are the result of a basic sense-making process in uncer-

tain or fearful circumstances (Hofstadter, 1966; see also

Bale, 2007). Particularly in the face of collective threats—

natural disasters, economic crises, and the like—conspiracy

theories will flourish, as these theories help citizens to

make sense of such events by blaming them on the delib-

erate actions of enemy groups.

Empirical research reveals that a high-impact, threat-

ening societal event, such as the assassination of a

president, results in stronger conspiracy beliefs than a

similar but less influential event (e.g., the president

survives an assassination attempt; McCauley & Jacques,

1979). These effects are attributable to people’s sense-

making motivation (van Prooijen & van Dijk, 2014).

More generally, feelings of a lack of control (Whitson

& Galinsky, 2008; van Prooijen & Acker, 2015), feelings

of powerlessness (Abalakina-Paap etal., 1999), or feel-

ings of uncertainty (van Prooijen, 2016; van Prooijen &

Jostmann, 2013) have been found to stimulate the men-

tal sense-making processes that are associated with

conspiracy theories. Consistent with our line of reason-

ing, these sense-making processes predict conspiracy

theories only when hostile coalitions are salient

(Marchlewska, Cichocka, & Kossowska, 2018). These

findings suggest a prominent role for feelings of vulner-

ability when predicting conspiracy theories.

Furthermore, various individual-difference variables

(e.g., paranoia, distrust, and antisocial tendencies) pre-

dispose people to interpret ambiguous social signals as

threatening or hostile (Kramer, 1998). Correspondingly,

research has revealed relationships between conspiracy

beliefs and numerous relevant variables (.10 < |rs| <

.48), including interpersonal paranoia (Darwin etal.,

2011), narcissism (Cichocka, Marchlewska, & Golec de

Zavala, 2016), generalized distrust (Abalakina-Paap

etal., 1999; Goertzel, 1994), trait anxiety (Grzesiak-

Feldman, 2013), disagreeableness (Swami etal., 2011),

and Machiavellianism (i.e., the extent to which people

are willing to exploit others for personal gain; Douglas

& Sutton, 2011). In sum, the research reported here

supports the assertion that conspiracy theories are acti-

vated after diffuse, socio-environmental cues suggesting

an increased likelihood of intergroup conflict.

Critical assessment

At present, little is known about functional differences

between different types of threats. Are some threats

more likely than others to elicit conspiracy theorizing,

and do they elicit different or similar conspiracy theo-

ries than other threats (e.g., wars or natural disasters)?

Although we consider it possible that the type of threat

matters, at present we have insufficient empirical or

theoretical basis to make specific predictions about

how type of threat may activate conspiracy beliefs dif-

ferently. Instead, we propose that threat cues automati-

cally trigger the human coalitional mind to make quick

mental calculations about the likely presence of hostile

conspiracies.

Efficiency of conspiracy beliefs

Our analysis implies that cues suggesting dangerous

coalitions should activate the conspiracy detection sys-

tem automatically, leading to a quick assessment of the

likelihood of dangerous conspiracies in the direct social

environment. Indeed, if a human tendency to believe

in conspiracy theories is adaptive, one may expect it

to be a fast and efficient system (Tooby & Cosmides,

2015). Our fifth proposition therefore is that the pro-

cesses underlying conspiracy detection are triggered

automatically and quickly by specific threats and emo-

tions, without requiring much deliberate thought.

The apparent articulate nature of certain conspiracy

theories notwithstanding, empirical research data sup-

port the idea that conspiracy theories emerge through

heuristics and intuitive mental processes. In a study by

Swami, Voracek, Stieger, Tran, and Furnham (2014),

analytic thinking decreased people’s tendency to believe

conspiracy theories and intuitive thinking predicted

increased belief in conspiracy theories. Likewise, van

782 van Prooijen, van Vugt

Prooijen (2017) found that lower education predicted

increased conspiracy belief, a finding that was partially

mediated by lower analytic-thinking skills. Furthermore,

analytic-thinking skills are not enough to promote skep-

ticism toward conspiracy theories: A deliberate motiva-

tion to be rational and base assumptions on evidence

is also critical (Ståhl & van Prooijen, 2018). The evi-

dence that is currently available suggests that conspir-

acy theories emerge from fast and efficient mental

operations (System 1) and not from complex, deliberate

mental operations (System 2).

Critical assessment

In everyday life, many conspiracy theories seem quite

articulate, which suggests that higher-order cognitive

processes are part of conspiracy theorizing. Once peo-

ple are deeply invested in a specific conspiracy theory

(e.g., the 9/11-truth movement), they typically have a

large number of seemingly persuasive arguments to

support their theories (Clarke, 2002). Integrating this

observation with the empirical findings reviewed here,

we suspect that conspiracy theories initially emerge

from heuristics, intuition, or strong emotions. Once

formed, these suspicious feelings may be rationalized

into sophisticated theories that are difficult to disprove.

Future research may more extensively test the automa-

ticity of human conspiracy detection. For instance, our

line of reasoning would suggest that activation of Sys-

tem 1 processes increases suspicious feelings of other

groups—a hypothesis that is closely associated with the

common finding that cognitive load increases stereotyp-

ing (e.g., Gilbert & Hixon, 1991).

Counterstrategies against conspiracies

Our final proposition stipulates that after detecting a

conspiracy, humans exhibit responses aimed at nullify-

ing the threat. Given the ubiquity and potential impact

of conspiracies, it stands to reason that ancestral

humans would have evolved a suite of strategies to

mitigate conspiracy threats. Such reactions may come

with a specific physiological, emotional, and behavioral

signature. For instance, people suspecting a conspiracy

could effectively cope by showing “approach” reactions

such as anger, hate, or hostility or by developing a more

formidable countercoalition. Alternatively, they could

mitigate the threat of a possible conspiracy by showing

fear and escape responses (avoidance responses). In

the following, we review evidence for these distinct

functional responses to conspiracy theories and when

they are likely to occur.

Avoiding conspiracies. If a conspiracy is being formed,

one self-preserving response is to actively try and avoid

the dangers associated with it. Suspecting powerful con-

spiracies may therefore trigger a host of negative emo-

tions that promote avoidance motivations and behaviors.

In ancestral times, these avoidance-oriented responses

would have been life-saving in the face of an actual con-

spiracy by, for instance, stimulating people to migrate to a

safer area. We therefore expect that powerful conspiracies

trigger avoidance-oriented responses.

One emotion that is typically associated with con-

spiracy belief is fear (e.g, Grzesiak-Feldman, 2013), and

fear generally tends to predict avoidance-oriented

behavioral reactions (Elliot & McGregor, 1999). We

therefore expect that people attempt to escape from

the dangers entailed by the suspected conspiracy. One

source of evidence supporting this comes from studies

showing conspiracy beliefs to be correlated with social

and political withdrawal behaviors. For instance, beliefs

about governmental conspiracies are associated with

feelings of alienation from the government (Abalakina-

Paap etal., 1999; Goertzel, 1994). Jolley and Douglas

(2014b) experimentally manipulated belief in conspir-

acy theories and tested the causal effects of such beliefs

on withdrawal behaviors. In one study, they found that

belief in conspiracy theories shaped withdrawal from

politics, as reflected in a decreased willingness to dis-

play political behaviors (e.g., voting).

In addition, conspiracy theories elicit strategies

designed to avoid the specific conspiracy. In one study,

participants were randomly assigned to conditions in

which they were exposed to information suggesting the

validity or invalidity of antivaccine conspiracy theories.

This manipulation influenced participants’ willingness

to have a fictitious child vaccinated, suggesting a spe-

cific motivation to avoid the dangers entailed by the

suspected conspiracy (Jolley & Douglas, 2014a). Like-

wise, belief in a climate conspiracy decreased partici-

pants’ willingness to reduce their carbon footprints,

suggesting that people’s strategies are functionally

related to the specific threat (Jolley & Douglas, 2014b;

van der Linden, 2015). Finally, a common conspiracy

theory among the African American community in the

United States is that birth control is a form of Black

genocide. Studies reveal a surprisingly high number of

African Americans who believe this conspiracy theory

and who respond by avoiding contraceptives (Thorburn

& Bogart, 2005). Although these latter examples argu-

ably are not functional behaviors from the perspective

of modern society, they do suggest that people actively

attempt to avoid the dangers entailed by the suspected

conspiracy—which is a functional response in an ances-

tral environment characterized by real conspiracies.

Approaching conspiracies. An alternative way of func-

tion ally responding to a suspected conspiracy is to actively

confront it. For instance, one might peacefully try to reason

Conspiracy Theories 783

with the suspected conspiracy, or one might form a counter-

coalition and commit a preemptive strike. These approach-

oriented responses can effectively decrease the dangers

associated with the conspiracy under some circumstances,

such as when one is able to quickly mobilize a counter-

coalition that is at least as strong as the suspected con-

spiracy. Some of these active, approach-oriented reactions

may be relatively peaceful. For instance, conspiracy theo-

ries increase protest intentions in order to change the

status quo (Imhoff & Bruder, 2014). Likewise, conspiracy

theories predict motivations to uncover and expose the

suspected conspiracy, as suggested by an increased sup-

port for democratic principles (Swami etal., 2011) and a

call for greater transparency (Clarke, 2002).

In addition to these relatively benign reactions, how-

ever, conspiracy theories often are associated with

angry, hostile reactions. Hofstadter (1966) noted that

conspiracy theories are mostly believed by people who

show hostility and exaggerated suspiciousness toward

others. Likewise, various authors argued that conspiracy

theories allow people to ventilate their anger by blam-

ing others for their own disadvantaged position

(Abalakina-Paap etal., 1999; Goertzel, 1994). Although

behavioral data are scarce in this research area, it is

likely that belief in conspiracy theories sometimes stim-

ulates aggression. Recall historical observations that

most wars and large-scale intractable conflicts were

characterized, and inspired, by conspiracy theories

about the enemy group at both sides of the conflict

(Pipes, 1997). As a case in point, it is well known that

Josef Stalin regularly ordered people to be executed

because of suspicions that they might be conspiring

against him and his administration.

In addition, conspiracy theories are associated with

ideological belief systems that promote hostility toward

different groups. Specifically, conspiracy theories are

empirically related with populism, political extremism,

and religious fundamentalism (Bartlett & Miller, 2010;

van Prooijen etal., 2015). Although there currently are

no direct causal data available revealing whether con-

spiracy beliefs cause extremism or vice versa, the find-

ings by Bartlett and Miller (2010) suggest that conspiracy

theories contribute to the violent tendencies of various

extremist groups. They specifically reason that con-

spiracy theories are a “radicalizing multiplier” (p. 4) that

influences the internal dynamics of such groups. On

the basis of a qualitative analysis of many radical groups

in society, these authors conclude that conspiracy theo-

ries “hold extremist groups together and push them in

a more extreme and sometimes violent direction”

(p. 5). In sum, the evidence currently available supports

the assertion that conspiracy theories are associated

with approach-oriented reactions as reflected in violent

or nonviolent confrontational actions designed to neu-

tralize the suspected conspiracy.

Critical assessment. Although the research findings

reviewed here are consistent with our model, many of

these findings are correlational, precluding solid state-

ments about cause and effect (e.g., Abalakina-Paap etal.,

1999; Goertzel, 1994; Imhoff & Bruder, 2014; Swami

etal., 2011; van Prooijen etal., 2015). To establish with

more certainty that detecting conspiracies causes functional

approach- or avoidance-oriented responses, researchers

could manipulate belief in conspiracy theories in experi-

mental settings (Jolley & Douglas, 2014b). Examining the

consequences of conspiracy detection should not be

restricted to perceptions or intentions. Behavioral data

are necessary to establish whether belief in conspiracy

theories indeed promotes aggressive, approach-oriented

strategies toward the suspicious coalition or promotes

increased avoidance-oriented behaviors (van der Linden,

2015). Furthermore, physiological data may help deter-

mine whether conspiracy detection elicits the stress

response of the sympathetic nervous system, as well as

the release of stress hormones (e.g., cortisol) that pre-

pares an organism to either freeze, fight, or fly.

Furthermore, research has not yet established what

moderating variables determine these reactions to sus-

pected conspiracies. One could predict that relative

power differences between groups play a role. If a rela-

tively powerless individual faces a powerful conspiracy

(e.g., the pharmaceutical industry), avoidance might be

more likely; however, if one sees opportunities to form

a countercoalition that effectively confronts a suspected

conspiracy (e.g., voting for a populist party that seeks

confrontation with the “corrupt elites”), approach-

oriented responses might be more likely. Finally, it is

possible that people can spread conspiracy theories

strategically to mobilize action against different groups.

Given the current state of affairs in this research domain,

assertions about such moderators remain speculative.

Conclusion

In this section we reviewed the hypothesis that con-

spiracy theories evolved as a functional response to the

presence of real, hostile coalitions in ancestral human

environments. We evaluated evidence for six proposi-

tions that follow from this adaptation hypothesis. Sup-

port for these propositions emerges from multiple

sources, including psychology, anthropology, history,

and political science. We therefore conclude tentatively

that the psychological mechanisms associated with con-

spiracy theories have been coopted in a more special-

ized psychological adaptation that is part of the human

784 van Prooijen, van Vugt

coalitional mind (see Tooby & Cosmides, 2010). Of

course, we must be cautious in our conclusions, because

most of the studies we have cited come from modern

complex societies and have not specifically tested an

adaptationist account of conspiracy beliefs. Neverthe-

less, the evidence that is presently available is consis-

tent with the idea that belief in conspiracy theories is

rooted in an evolved psychology to protect against

powerful and potentially hostile coalitions.

Conclusions, Implications, and

Future Research

The adaptive-conspiracism hypothesis asserts that belief

in conspiracy theories emerges from a natural, inborn

suspiciousness of potentially dangerous coalitions. Con-

sequently, we assume that conspiracy theories have

been directly adaptive for ancestral humans to navigate

their social world, which was characterized by fre-

quently recurring coalitional dangers. Yet we also con-

sidered an alternative by-product hypothesis that (a)

the human tendency to perceive conspiracies is a by-

product of other psychological adaptations and (b)

conspiracy beliefs have no adaptive qualities.

Although it is currently impossible to exclude the

by-product hypothesis with hard empirical data, we

propose that a model assuming directly adaptive quali-

ties of conspiracy theories is more plausible in light of

the evidence reviewed in the current article. The ten-

dency to form groups and coalitions—and engage in

violent conflict with different groups or coalitions—has

characterized human social behavior for more than 2

million years and also characterizes the behavior of

close genetic cousins, such as chimpanzees (Wrangham,

1999). The core question, therefore, is whether the sus-

picious feelings about other groups that are at the root

of conspiracy beliefs may have provided early humans

a selection advantage. Given the realistic dangers of

hostile coalitions in an ancestral environment, along

with the life-saving functionality of detecting conspira-

cies before they strike, conspiracy beliefs are likely to

have been adaptive among ancient hunter-gatherers.

Even when conspiracy theories have been adaptive

in ancestral times, in modern times conspiracy theories

often have harmful consequences, eliciting poor health

choices (e.g., refusing vaccines), climate-change skepti-

cism, intergroup conflict, aggression, and radicalization

(Brotherton, 2015; Douglas etal., 2017; van Prooijen,

2018). Scientific study of this phenomenon is thus nec-

essary because it may inform policymakers and other

societal stakeholders about how to reduce conspiracy

beliefs among the public. Although the scientific study

of conspiracy theories is an emerging research domain

in the social sciences, in terms of theory development,

it is still in its infancy. One of the aims of the current

article was to illuminate the distal, evolutionary roots

and potential functions of conspiracy theories by inte-

grating key findings within this research domain with

insights drawn from evolutionary psychology and

anthropology. In the following, we highlight a number

of unresolved issues and give suggestions for future

research to provide a starting point for an evolutionary

approach to understand the human tendency to believe

conspiracy theories.

Prominence of coalitional dangers

Given that the main assumptions of our model are

based on a link between conspiracy beliefs and the

prominence of coalitional dangers, a future research

program may directly focus on this link. For instance,

it might be reasoned that extensive social networks

mitigate ancestral humans’ vulnerability to hostile coali-

tions because of the capacity to quickly and effectively

organize a countercoalition. Our evolutionary model

thus predicts that strong social networks, network size,

or even organizational skills decrease susceptibility to

conspiracy theories. Moreover, conspiracy beliefs may

be fueled by competence assumptions about the sus-

pected coalition. Although perceivers may rate sus-

pected conspiracies as low on morality, they are likely

to rate them relatively high on agentic traits (e.g., intel-

ligence; power) because coalitions are more dangerous

to the extent that they are more competent.

Likewise, some individuals face threatening coalitions

more realistically than others, at all levels of society. For

instance, societal turmoil and frequent violent conflict

between subgroups are highly likely to stimulate con-

spiracy theories (Pipes, 1997). Our model would suggest

that belief in conspiracy theories is particularly strong

among the relatively “weak” and vulnerable subgroups

because the dangers of the hostile coalition are lower

for the dominant groups. Furthermore, these processes

may also extrapolate to high-power individuals: Dicta-

tors in politically unstable countries are more likely to

face a violent revolution than democratically elected

officials in politically stable countries, and it might thus

be reasoned that dictators entertain stronger conspiracy

beliefs toward their followers than legitimate leaders

who were elected through a democratic process.

Gender

Should we expect gender differences in conspiracy

theorizing? It is hard to predict whether men or women

are more susceptible to conspiracy beliefs. On the one

hand, one might reason that men in particular should

be susceptible to conspiracy theorizing because they

Conspiracy Theories 785

were more likely to be killed by hostile coalitions than

women (Van Vugt, 2009). Likewise, in contemporary

traditional societies, raiding groups are much more

likely to kill men than to kill women (e.g., Walker &

Bailey, 2013). On the other hand, although the majority

of victims of coalitional violence in traditional societies

are male, this does not mean that the female body count

is negligible. In their analysis of 11 South American

traditional societies, Walker and Bailey found that 31%

of the casualties resulting from coalitional violence

were female. Furthermore, coalitional aggression by

other groups often implied an additional predicament

that was unique to women, which was the possibility

of abduction, rape, and forced marriage in an enemy

society (Chagnon, 1988). This creates selection pressure

on women to be suspicious of conspiracies as well. An

important element of female genetic fitness is reproduc-

tive choice, along with committed male partners that

are willing to invest time and resources in their joint

offspring (Trivers, 1972). There is indeed no clear evi-

dence for a gender effect in conspiracy theories: In

most studies that test for the effects of gender, men and

women are about equally likely to believe conspiracy

theories (e.g., Darwin etal., 2011; Douglas etal., 2016;

Jolley & Douglas, 2014b; van Prooijen & Acker, 2015;

van Prooijen etal., 2015).

A number of different predictions about the role of

gender follow from our analysis, however. First, people

are likely to assume that a dangerous conspiracy consists

mostly of men. Recall that people associate danger with

out-group men in particular, not out-group women

(McDonald etal., 2012; Navarrete, McDonald, Molina, &

Sidanius, 2010), and consistently, coalitional aggression

among hunter-gatherers is typically committed by men

(e.g., Chagnon, 1988; Van Vugt etal., 2007). To conduct

a thought experiment in the context of conspiracy theo-

ries, of what subdivision of a national secret service

agency would citizens be more suspicious—a subdivi-

sion that consisted mostly of men or a subdivision that

consisted mostly of women? Although it seems less obvi-

ous to expect gender differences in the extent to which

people detect conspiracies, it is plausible that female

versus male conspiracies are treated differently. Future

research may test this “male conspiracy” hypothesis.

Second, it is likely that men’s and women’s responses

to conspiracy detection are functionally different:

Women may lean more toward avoidance-oriented reac-

tions and men may lean more toward approach-oriented

reactions. This idea is consistent with the insight that

men are more likely than women to engage in inter-

group hostility (i.e., the male-warrior hypothesis; Van

Vugt etal., 2007), suggesting gender-specific responses

to conspiracy beliefs.

Conspiracy theories and pathology

Modern conspiracy theories vary in their plausibility.

Although some conspiracy theories that one can find

on the Internet are theoretically possible, and some-

times even plausible, other conspiracy theories are

highly implausible (e.g., that the world is ruled by alien

lizards disguised as humans). Excessive conspiracy

theorizing is common among paranoid schizophrenics,

a pathology with a genetic basis (Harrison & Weinberger,

2005). What does such genetic pathology imply for our

analysis? Note that the adaptive-conspiracism hypoth-

esis is not designed to explain potential pathologies.

Genetic mutations can be dysfunctional, and pathologi-

cal paranoia is unlikely to be adaptive. More relevant

for our line of reasoning is the empirical finding that

large numbers of ordinary citizens believe in a consistent

set of conspiracy theories with common themes related

to health and safety (Oliver & Wood, 2014; Sunstein &

Vermeule, 2009). The adaptation hypothesis presented

here addresses the question of why conspiracy theories

are a widespread and culturally universal phenomenon

among large groups of citizens that show no sign of

mental illness.

Final conclusions

Modern humans are highly susceptible to conspiracy

theories, even when there is little direct evidence to

support them. Why are conspiracy theories so wide-

spread and influential among regular citizens? The pres-

ent review compared a by-product explanation with an

adaptive explanation. The by-product hypothesis sug-

gests that conspiracy theories originate from the inter-

action between a set of psychological mechanisms that

are nonspecific for conspiracy theories. The adaptive-

conspiracism hypothesis suggests that conspiracy

beliefs have the properties of a psychological adapta-

tion that is functionally designed to deal with specific,

recurrent dangers posed by hostile coalitions in human

evolutionary history. In an ancestral environment in

which humans were frequently confronted with coali-

tional violence, it may have paid to be suspicious of

powerful, potentially hostile coalitions. We propose that

conspiracy theories are widespread because in the evo-

lutionary history of our species, it was adaptive to hold

these beliefs. Whether it is still adaptive for humans in

the modern world to be overly susceptible to con-

spiracy theories remains to be seen.

Action Editor

Timothy McNamara served as action editor and Robert J.

Sternberg served as editor-in-chief for this article.

786 van Prooijen, van Vugt

ORCID iD

Jan-Willem van Prooijen https://orcid.org/0000-0001-

6236-0819

Declaration of Conflicting Interests

The author(s) declared that there were no conflicts of interest

with respect to the authorship or the publication of this article.

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