The biology of cultural conflict.

2012·0.17 MB·English

by  Berns, Gregory S.

Phil.Trans.R.Soc.B (2012)367,633–639
doi:10.1098/rstb.2011.0307
Introduction
The biology of cultural conflict
Gregory S. Berns1,* and Scott Atran2
1Center for Neuropolicy, Emory University, Atlanta, GA 30322, USA
2CNRS-Ecole Normale Supe´rieure, Institut Jean Nicod, 29, Rue d’Ulm, 75005 Paris, France
Although culture is usually thought of as the collection of knowledge and traditions that are trans-
mitted outside of biology, evidence continues to accumulate showing how biology and culture are
inseparablyintertwined.Culturalconflictwilloccuronlywhenthebeliefsandtraditionsofonecul-
tural group represent a challenge to individuals of another. Such a challenge will elicit brain
processes involved in cognitive decision-making, emotional activation and physiological arousal
associated with the outbreak, conduct and resolution of conflict. Key targets to understand bio-
cultural differences include primitive drives—how the brain responds to likes and dislikes, how it
discountsthefuture,andhowthisrelatestoreproductivebehaviour—butalsohigherlevelfunctions,
suchashowthemindrepresentsandvaluesthesurroundingphysicalandsocialenvironment.Future
culturalwars,whiletheymaybearfamiliarlabelsofreligionandpolitics,willultimatelybefoughtover
control of our biology and our environment.
Keywords: culture; neuroscience; functional magnetic resonance imaging; religion; politics
1. CULTURAL CONFLICTAND WHY BIOLOGY and an atheist would surely react differently, and this
MATTERS willprobablymanifestasdifferencesinbrainactivation
Inthemostgeneralsense,culturecanbethoughtofas [4]. Similarly, in the US political realm, probing the
the knowledge, customs and traditions of a group of role of government spending could well elicit different
people[1],whichsystematicallydriveandchannelcol- brain activations for Republicans, Democrats and Tea
lectivedispositionsofthoughtsandbehavioursintothe Party members. Second, mere cultural differences in
future. Culture includes social, legal and economic brain activation do not necessarily imply conflict.
institutions, as well as non-institutionalized trends Cultural conflict would be hypothesized to occur
and movements.Culture encompasses technology, lit- only whencertain beliefs and traditions ofone culture
erature and art, as well as disparate political, ethnic representachallengetoindividualsofanotherculture.
and religious beliefs and biases that both infuse and Such a challenge would elicit brain processes involved
connect the higher cognitive functions and emotions in the cognitive decision-making, emotional activation
of individual brains [2]. andphysiologicalarousalassociatedwiththeoutbreak,
Although culture is usually thought of as the collec- conduct and resolution of conflict.
tion of knowledge and traditions that are transmitted Because biological processes govern our percep-
outside of biology, one cannot credibly deny that the tions, interpretations and reactions to cultural events,
thoughts and behaviours of individuals contribute to understandingtheseprocesseswillnotonlyhelpusunder-
the creation of culture,and thatevery person must pro- stand cultural conflicts but also potentially mitigate
cess and react to cultural phenomena. Over 100 years them. In this issue, we have collected a series of papers
ago, William James said it clearly, ‘There is not a single that beginsto tackle issues surrounding cultural conflict
one of our states of mind, high or low, healthy or fromabiologicalperspective.Theculturalthemesrange
morbid, that has not some organic process or con- frompoliticalpartizanshiptosacredvaluesandreligious
dition... They [beliefs] are equallyorganically founded, conflicts,andthetoolsusedtostudythemincludebrain
be theyof religious or non-religious content’ [3, p. 16]. imaging with functional magnetic resonance imaging
Thus,culturalconflictshouldmanifestintwoways. andmeasuresofphysiologicalarousal(skinconductance
First, if there are systemic and substantial cultural responses(SCRs)andeye-tracking).
differences between groups of people, this would
result in different types of processing in individual
brainsthatformthegroup.Take,forexample,religion. 2. PRIMITIVE DRIVES
When presented with a concept like God, a Christian We begin with the most primitive biologic processes
linked to decision-making: good versus bad. Every
animal makes decisions about things that it wants
*Authorforcorrespondence([email protected]). andthingsitavoids.Inhumaneconomics,wedesignate
thesecategoriesas ‘goods’and ‘bads’,butbehaviourally
One contribution of 12 to a Theme Issue ‘The Biology of Cultural
Conflict’. these categories can be mapped out by things that
633 Thisjournalisq2012TheRoyalSociety
634 G. S. Berns & S. Atran Introduction. The biology of cultural conflict
individuals approach or avoid. For humans, there are spectrum are there to mitigate biological sensitivity
certain universals. We generally like (and approach) tounpleasantries.
things linked to survival and prosperity: food, mates Anotherprimitivebiologicalprocessthatallanimals
and money; and we generally dislike (and avoid) things must face is how to value the future. Humans have
linkedtomortalityandloss.Althoughuniversal,cultural extensive cognitive capacity for both remembering
differencesshapetheirrelativeimportancetoindividuals, the past and imagining the future, and how we value
andsowebeginbyexaminingresponsestothesebiologic- the future has ramifications for individuals and
ally primitive drives. For example, which is more societies. When the future is expected to be better
important—seeking out the good things or avoiding the than the present, there is motivation to invest in the
bad?Differencesoverthisbasicdecisionmaycausecon- future. Such investments include having children,
flicts both within and between cultures. Dodd et al. [5] emphasizing their education, investing and building
approachthequestionintermsofpoliticalaffiliation. infrastructure, saving for retirement and adopting
Even within a society, individuals may hold differ- behaviours that prolong and increase the quality of
ent beliefs about politics that lead to cultural life. On the other hand, when the future is expected
conflict. Strictly defined, politics refers to governing to be worse than the present, the incentives move
institutionsandpolicies.However, political affiliations towards living in the present: profligate consumption
often align with other cultural and religious beliefs, so and reduced infrastructure investment.
that when we talk about political differences, these Onewaytomeasurethevalueofthefutureisthrough
may include broad cultural differences even within a an individual’s discount rate. This is the rate at which
society.Thereappearstobeastrongdispositiontocat- timedevaluesfutureexpectedvaluesfor thatindividual.
egorize in terms of binaryoppositions: to dichotomize Kimetal.[8]examinebiologicaldifferencesindiscount
[6], essentialize [7] and thereby deepen outward rates between Koreans and Americans. They find that
differences that may have initially been superficial or Americans have discount rates over twice that of
arbitrary. Ever since the French Revolution, it is Koreans, and that these differences are mirrored in the
common to divide secular political camps into the activity of the ventral striatum—a brain structure well-
‘left’ and ‘right’. The left/right division has different known to be associated with value-based decisions.
meanings in different countries but generally maps These findings lay the groundwork for understanding
onto bigger or smaller roles of government. In the differences in culturally situated beliefs towards savings
USA, it is liberals and conservatives, or Democrats and and investment, which may be a source of conflict.
Republicans. In the UK, Labourand Conservative par- Another biological primitive, which may also relate
ties; in France, left (e.g. Socialist Party) and right (e.g. to future discounting, is reproductive behaviour.
RPR); in Germany, the left (SPD) and the right Henrich et al. [9] examine the cultural conditions
(CDU/CSU); in Spain, the left (PSOE) and the that foster and inhibit monogamous marriage. Like
right (PP); in Israel, Laborand Likud, and so on. discount rates, a society’s institutions for marriage
Do such divisions of left and right on the political provide a window into how the culture values the
spectrum merely reflect the human tendency to cat- future. Fundamentally, marriage is a framework that
egorize, or might there be fundamentally two allows society to recognize reproductive rights, and
contrasting types of politically relevant cognitive and secondarily, to provide for an orderly passing of prop-
social dispositions that differentially characterize indi- erty to offspring. Although marriage is a cultural
viduals in every culture? Dodd et al. [5] provide institution, reproduction is generally expected to be a
physiological evidence for the latter. Using SCRs, consequence of the arrangement, and therefore, inter-
which are a measure of physiological arousal, they twined with biology. Given that males can reproduce
find significant differences between people on the left with relatively low cost, and that historically 85 per
and the right. Importantly, the differences appear cent of societies have allowed men to have multiple
only when subdivided into ‘good’ and ‘bad’ provoca- wives, how could monogamy ever be adaptive?
teurs. Those on the right show arousal responses to Henrich et al. [9] suggest a theory with a simple
pictures of aversive stimuli like maggot-ridden meat premise: polygamy creates a residual pool of males
and angry mobs, while those on the left show arousal with no possibility of having a wife. With limited pro-
responses to positive pictures like rabbits and happy spects of future reproductive success, these males
children. A follow-up study using eye-tracking to should have steeper discount rates (substantially
measureattentionconfirmedthatattentionandarousal higher valuation of the present), which is associated
areyokedtogetheralongthesesamedimensions. withmoreimpulsivebehaviours:criminalactivity,vio-
Thesefindingsmayhelptoexplaindifferentialsupport lence anddrug use. Henrich etal. [9]arguethatthese
forpolicydifferencesbetweenthepoliticalleftandright. are destabilizing influences in a society. Adopting
Individualsonthepoliticalrightappeartobemoresensi- monogamy as the cultural norm ensures a mate for
tiveandattunedtotheunpleasantthingsinlife.AsDodd everyone,andcrimeandviolencedecrease,benefitting
etal.[5]note,‘thisresponsiveness,inturn,isconsistent all. In contrast, polygamous societies will have a large
with the fact that right-of-centre policy positions are pool of males with no hope for reproduction. These
oftendesignedtoprotectsocietyfromout-groupthreats males can be channelled into armies and sacrifice
(e.g. by supporting increased defence spending and their genes for ‘their brothers’.
opposing immigration) and in-group norm violators Carrying the theme of conflict forward to violent
(e.g.bysupportingtraditionalvaluesandsternpenalties means, there is considerable historical, cross-cultural
for criminal behaviour)’. If true, then the rules and and psychological evidence that males and females
policies advocated by the two poles of the political differ in aggressive tendencies, especially in the most
Phil.Trans.R.Soc.B(2012)
Introduction. The biology of cultural conflict G. S. Berns & S. Atran 635
violent behaviours of aggravated assault and homicide pros and cons for advancing material interests at all,
[10], war and terrorism [11]. McDonald et al. [12] but rather using a moral logic of ‘sacred values’—
propose an evolutionary-based argument for why this convictions that trump all other considerations—that
is the case. It has been suggested that females are a cannot be quantified in straightforward ways [20].
resource for which males aggressively compete. How- Inpotentiallyviolentsituationsofintergroupconflict,
ever, ‘this competition need not take the form of sacred values appear to operate as moral imperatives
direct contests for instances of sexual access, but that generate actions independently, or out of pro-
may include conflicts over feeding territories, nest portion, to their evident or likely results, because it is
sites and more intangible resources, such as social the right thing to do whatever the consequences [21].
influence, power and status—resources that can be For example, regardless of the utilitarian calculations
converted into reproductive opportunities over time’. of terror-sponsoring organizations, suicide terrorists
They suggest that intergroup conflict has affected the appear willing to make extreme sacrifices that use a
social psychologies of men and women differently. ‘logicofappropriateness’ratherthanacalculusofprob-
Because men are the more common perpetrators and able costs and benefits [22]. Or consider the American
victims of intergroup aggression, coalitional psycho- revolutionaries who, despite belonging to a society that
logy is likely to be more pronounced among men. had the highest standard of living in the world, defied
From this, McDonald et al. [12] argue that selection the greatest empire, army and navy of the age in pled-
has favoured the evolution of cognitive processes for ging ‘our lives, our fortunes, our sacred honour’ for
‘the formation of male coalitions capable of planning, the cause of ‘liberty or death’, where the desired out-
initiatingandexecutingattacksonout-groupswiththe come was highly improbable by any measure of
aimofacquiringorprotectingreproductiveresources’, manpower or available means of material warfare [23].
which is referred to as the ‘male warrior hypothesis’. Theproblemwithsacredvalues,fromanexperimen-
talpointofview,isthattheyaredifficulttostudyinthe
laboratory. Berns et al. [24] describe a novel paradigm
3. ‘GIVE ME LIBERTY OR GIVE ME DEATH’ in which they use integrity as a proxy for the strength
In The Origin of Species, Charles Darwin considered of an individual’s commitment to a particular cultural
adaptations—including warlike and altruistic behaviour value. Integrity refers to an individual’s consistency of
in humans—only for the individual’s own use in its values and actions. For example, although we cannot
struggle to gain resources to produce offspring: ‘good test whether an individual is willing to kill an innocent
foritself’,but‘never...fortheexclusivegoodofothers’ human being (a common cultural taboo), we can test
[13, p. 230]. Later, however, he puzzled over the their willingness to sign a document that says they
problem of how self-interest alone could account for would. Although signing such a document does not
humankind’s aptitude for self-sacrifice to the point of bind the person to that action, it creates an inconsist-
giving up one’s life—the totality of a person’s self ency between value and action that signals a loss of
interests—for tribe, nation, religion or for humanity. integrity. It is reasonable to assume that if something
The puzzle led Darwin to modify his view that natural is truly sacred, then an individual would maintain
selection only produces selfish individuals. In The their integrity for that value and not sign such a docu-
DescentofMan,hesuggestedthathumanshaveanatur- ment. What if they were offered money to sign? It
ally selected propensity to the virtue of ‘morality’, that then becomes a trade-off between the monetary gain
is, a willingness to sacrifice self-interest in the cause of and the cost in personal integrity.
group interests. This includes heroism in battle, and If sacred values are represented in a utilitarian
martyrdom, where prospects for personal survival are manner, then prior neuroeconomic research suggests
very low but somewhat higher for those in the group that they should be associated with increased neural
who may be neither kin nor kith. Groups possessing an activity in brain regions associated with the calcu-
abundance of individuals with such moral virtue, lation of utility; alternatively, if sacred values are
Darwin argued, would be better endowed in history’s represented as deontic rules, then brain regions
spirallingcompetitionforsurvivalanddominance[14]. associated with the processing of moral permissibility
Thenatureofmoralvaluesis,inlargepart,definedby (rights and wrongs). Interestingly, Berns et al. [24]
the culture in which individuals engage them in find evidence for the deontic processing of sacred
decisions, but virtue theory suggests two very different values. Moreover, they find that the stronger the
ways in which moral values might be processed [15]. deontic processing in brain regions associated with
Moral values could be either deontological in nature theengagementofrules,themoreactiveanindividual
[16]ortheycouldbeutilitarian[17].Deonticprocessing tends to be in group organizations. This suggests that
isdefinedbyanemphasisonabsoluterightsandwrongs, groups carry and inculcate cultural rules in the brains
whereas utilitarian processing is characterized by costs of individuals.
and benefits. Models of rational behaviour predict Cultural conflict is likely to emerge when the rules
many of society’s patterns, such as favoured strategies and values of one cultural group are substantially
for maximizing profit or likelihood for criminal behav- different from another, and members of the cultures
iour in terms of opportunity costs [18]. But the come in contact with each other. How individuals
prospectsofcripplingeconomicburdensandhugenum- react depends greatly on the specific context, but the
bersofdeathsdonotnecessarilyswaypeoplefromtheir findings inthis issue point togeneric biological mech-
positions on whethergoingtowar,oroptingfor revolu- anisms.AsBernsetal.[24]show,theamygdala—akey
tionorresistance,istherightorwrongchoice[19].One structure for physiological arousal—is activated when
possible explanation is that people are not weighing the individuals are presented with statements contrary to
Phil.Trans.R.Soc.B(2012)
636 G. S. Berns & S. Atran Introduction. The biology of cultural conflict
their own personal sacred values. Although amygdala framework suggests ways in which one might measure
activation is not specific for a particular emotional how culture affects individual decision-making.
state, it is consistent with heightened arousal. But in Alongtheselines,thewaycultureaffectstheindividual
aconflictsituation,itismostlikelyanegativeemotion- canbemeasuredinthelaboratorybycontrollingspecific
al stateofhigh arousal. This is important becausethis elementsofculture.Kishidaetal.[31]doexactlythisby
is the physiological state associated with ‘fight or creating an experimental culture in which status is
flight’. Confronting individuals’ sacred cultural values definedbyperformanceonanintelligencetest.Inmany
with conflicting ones, places the individuals in a state cultures, intellectual achievement is a marker of status
in which they are more likely to experience ‘moral and success, and so this is a reasonable place to start.
outrage’ and engage in violence [25]. Specifically, they explore the neural effects of publicly
One constellation of values that appears to acquire broadcastingthisstatusmarker.Behaviourally,theyfind
sacred status in a variety of different cultural settings, thatbroadcastingranksofintelligencegloballydepressed
and whose violation often generates moral outrage that everyone’sperformance,andonlyasubsetofindividuals
can lead to extreme violence, concerns the conception wereabletorecover.Theimplicationisthatbroadcasting
of‘honour’[26].Gelfandetal.[27]discusstheimport- socialrank,whetherbyintelligenceorsomeothermetric,
ance of honour in Middle Eastern countries. They find is a powerful tool to both reward and punish culturally
that in Middle Eastern cultures honour is not only a sanctioned behaviours. Kishida et al. [31] shows that
status indicator for individuals, but that it is a transfer- the biological effect of cultural enforcement may lie in
able resource to immediate family members. Moreover, the amygdala. Individuals who are able to inhibit the
honour is a shared resource with ‘ripple effects on the amygdala, through activation of the left prefrontal
extended family, friends and social circles, the commu- cortex, may be relatively immune to cultural norms. If
nity, neighbourhood, tribe and organizations’. When so,thismayultimatelyshedlightonwhattypesofindivid-
honour is lost through the actions of an individual, the uals comply with cultural norms, resist them or react
extended community suffers. Thus, there is a strong violentlywhenthenormsarethreatened.
incentive for the establishment of cultural rules that
treat honour as a sacred value. Any perceived violation
of the code of honour by those outside the society may 5. FROM DIFFERENCES TO CONFLICT
begroundsfor violenceandevenwar[28],whereasvio- Justbecauseculturesaredifferentdoesnotnecessarily
lation by individuals within a culture of honour may be meantheywillendupinconflict.Thus,whilecultural
considered an attack upon the moral foundation of the differences may be a facilitating condition for conflict
society that merits extreme punishment [29]. to occur, differences alone are insufficient. The same
logic applies to biological differences: the mere dem-
onstration of biological differences between cultural
4. ENFORCEMENT OF CULTURAL RULES groups does not mean that a conflict will follow. As
Social groups that affirm and maintain their identity notedabove,culturesmanifestavarietyofmechanisms
through cultural rules must also have the means to to instill and maintain their internal set of beliefs,
enforce compliance. Like the primitive drives noted which,whenchallenged,setinmotionaseriesofphys-
earlier, enforcement mechanisms must be either iological responses that prime individuals for violent
rewarding or punishing in nature. Rewards for group action. Who engages in violence and who approaches
membership can be explicit through recognition and conflict from the standpoint of negotiation?
conferring of status vis-a`-vis titles; through conspicu- Two papers in this issue examine brain responses
ous displays of status in the form of material wealth across cultural groups already in conflict and provide
or number of children, for example; or indirectly important new insights into the cognitive processes
through reciprocal relationships with other members evoked when individuals are forced to consider the
of the group—for example, business deals or mar- perspectives and beliefs of someone that, in other
riages. Punishments, on the other hand, diminish circumstances, might be considered an enemy.
social status by taking away the opportunity to reap Theadvantageofstudyingmembersofgroupsalready
these rewards. Punishments can be explicit and in conflict is that they provide a cross-sectional
public, e.g.prisonorcorporalpunishment, or implicit snapshot of both cognitive and emotional responses
through shunning and loss of relationships within the to established in- and out-groups.
community, which closes the opportunity to do Bruneau et al. [32] suggest that when groups arein
business or have a spouse. conflict, cultural biases serve to further drive the
Huettel & Kranton [30] address this relationship groupsapartandpreventreconciliation.Theytheorize
between individuals and their social groups by that these biases inhibit the individual’s capacity to
suggesting a new framework based on ‘identity neuro- either mentalize about the states of mind of someone
economics’. They adapt the standard expected utility from the conflicting culture or empathize with their
model of decision-making to include a cultural term pain. Using Arab and Israeli subjects, they examine
that interacts with individual utility. In this model, theneuralcircuitsassociatedwithprocessingpoignant
‘identity utility’ depends on the extent to which one’s stories of members of the corresponding in- and out-
own and others’ actions match prescribed behaviour. groups. If these longstanding cultural conflicts have
Identity utility also depends on the status of one’s resulted in an inability to empathize the pain of the
social group, and the match between the individual’s opposing group, then, as Bruneau et al. [32] suggest,
attributes to the ideal of the social group. Whether it this should lead to blunted responses in the brain’s
is honour or status or material markers of status, their pain matrix to depictions of pain in the opposing
Phil.Trans.R.Soc.B(2012)
Introduction. The biology of cultural conflict G. S. Berns & S. Atran 637
group. Although a variety of behavioural metrics are to the expected value of outcomes, growing evidence
consistent with warmer feelings towards the in-group, suggests that the striatum also signals the salience of
and less empathy for the out-group, the neuroimaging the action itself[35]. This isconsistent with Bruneau’s
results suggest a more nuanced explanation. findings that groups in conflict with each other are
Responses inbrainregions associated with mentaliz- highly salient to each other.
ing were equally large for both Arab and Israeli
participants reading about Israeli and Arab targets,
but less so for a distant, third-party group (South 6. WHAT DOES IT MEAN?
Americans). This suggests that the brain processes The 50 years following World War II were a period of
associated with mentalizing have more to do with the modern history that was unprecedented for its con-
salience and proximity of the group rather than stancy in terms of the bipolar rivalry between global
‘friend’ or ‘enemy’ labels. More than these labels, secular ideologies, and the dominance of a ‘rational
empathic responses may be driven by personal signifi- actor’ paradigm for dealing with that rivalry. It seems
cance. This dovetails with Gelfand’s results, suggesting increasingly obvious that such an era is over. As we
thatpersonalsaliencecanbeamplifiedbytheconstruct noted earlier, cultural differences do not always lead to
of honour, especiallyas it can be shared. conflict, but several factors on both a local and global
Another testbed of cultural conflict can be found scale have increased the likelihood of conflict. Avastly
in the USA between Democrats and Republicans, increased population means more people competing for
especially those who have strong party affiliations. As limited resources, and the globalization of the economy
Dodd et al. [5] showed, skin conductance measures means that local conflicts ripple throughout the world,
suggest differences in arousal to good and bad stimuli, affecting markets and distribution of raw materials.
thussettingthestageforabiologicallymediatedconflict Modern communication through text messaging, social
between Democrats and Republicans. Examining the networking and new Internet technologies ensure that
issue directly, Falk et al. [33] focus on brain responses news of conflict spreads almost instantly. Thus, where
in Democrats and Republicans in the months leading geographical remoteness previously had a strong role in
up to the 2008 presidential election. As they note, keepingconflictslocal,wearenowinthesituationwhere
the election provides a focal point that increases the riotsinGreeceorMumbai,forexample,haveimmediate
personal salience of whatever conflict is perceived global consequences. Consequently, the two basic
between members of the two parties. Thus, whatever requirements for the initiation of cultural conflict—
differences exist between Democrats and Republicans, substantialdifferencesinbeliefsandactivechallengesto
an election forces them into conflict because only one thosebeliefs—arenowdoneelectronically.Physicalproxi-
canwin.Falketal.[33]hadDemocratsandRepublicans mityisnolongeranecessaryconditionfortheengagement
considerissuesfromthestanceoftheirownparty’scan- ofthebiologicalrequirementsforconflict.
didateor theother(McCainandObama).Interestingly, Culturalconflictsarenotsimplytheresultofdiffer-
they find that regions associated with mentalizing ent traditions. The proverbial ‘clash of civilizations’
functions, especially the medial prefrontal cortex, were may be less appropriate as a characterization of post-
more active when taking the perspective of one’s own Cold War conflicts throughout the world than a
candidate.Moreover,theeffectwasexaggeratedinindi- crisis, or even collapse, of traditional territorial cul-
viduals who measured higher on scales of perspective tures. Vertical, generation-to-generation forms of
taking. One of the presumed impasses to negotiation socialstructureandinformationhierarchiesarebreak-
between conflicted groups is the inability to see things ing downandmany,especially theyoung,areforming
fromtheotherside.AsFalketal.[33]note,evenindivid- their identities in global, media-driven political cul-
uals who exhibit temperaments that are more empathic tures through horizontal peer-to-peer relationships
may deploy this ability selectively—an effect that was that ignore historical and spatial constraints [36].
amplified as the election grew closer. But whereas Internet communication and revivalist
Ifthe ability toempathizewith, or take the perspec- religious ideologies may increasingly serve as facilita-
tive of, someone from an out-group is reflected in the tors and vehicles for conflict, root causes may remain
responsiveness of prefrontal circuits, then what about primitive and biologic. Fundamentally, people want
trusting them? Stanley et al. [34] examine neural to survive, prosper and create a better future for
responses in a ‘trust game’ and how these responses their children and those they care for, including gen-
are affected by the race of the individual to be trusted. etic strangers that form part of primary reference
Inthetrustgame,participantsaregivenanendowment groups,beittheir tribe,nation,religion orconception
ofmoney,fromwhichtheycansharewithatrustee.Any of ‘humanity’. When these basic goals are threatened,
money sent to the trustee is quadrupled, and then the conflict is more likely.
trustee can either keep it or split the proceeds 50/50. Manyofthepapersinthisspecialissuedealwiththe
The exchanges are anonymous, except that the parti- way in which cultural differences map onto biological
cipant is shown a picture of the partner’s face before differences in the brain. We will set aside the question
deciding how much to send. Racial bias can be of causality and take these observations at face value.
measured by the difference in amounts of money sent For example, biological differences in discount rates
to black versus white trustees. Stanley finds that the have direct implications for behaviour. All things
ventral striatum activity correlates with the individual’s being equal, a society in which individuals tend to
race bias: this structure was more active when making have steeper discount rates will behave more impul-
decisions about individuals from whichever race they sively. Because the future is worth relatively little, such
trustedless.Althoughstriatalactivityistypicallyrelated cultures would resist investing in infrastructure; would
Phil.Trans.R.Soc.B(2012)
638 G. S. Berns & S. Atran Introduction. The biology of cultural conflict
tendtodevalueeducation;wouldengageinmorerapid relationships, the better position humankind will be in
depletion of their resources; and would generally ‘live to mitigate these looming conflicts.
for the moment’.
Justbecausetherearebiologicaldifferencesdoesnot
mean they are immutable. We know, for example, that We aregrateful to Michael J. Prietula forcomments on this
individual discount rates can be altered by drugs. manuscript. Funding support was provided by grants from
the National Science Foundation (NSF) and the Air Force
Unfortunately, most of the documented effects of
Office of Scientific Research (AFOSR) through the Office
drugs, such as tobacco, are associated with increased
ofNaval Research (ONR).
discountrates,making individuals even moreimpulsive
[37].However,givenevidenceforthecloselinkbetween
discount rates and foraging behaviour in animals, it is
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