Realistic Conflict Theory and Evolutionary Approaches

The study of intergroup relations in theory encompasses infinite diversity, from the bloodiest massacres to the most respectful and loving alliances. Research on intergroup relations, however, has mostly focused on groups’ mutual harm-doing, reflecting a general bias against positive psychology, the study of human flourishing and pro-sociality (Halperin et al., Reference Halperin, Hameiri and Littman2023; Noor et al., Reference Noor, Brown, Gonzalez, Manzi and Lewis2008). Psychology as a research area grew in the 20th century, particularly during and after the death of millions in the Second World War. Key researchers sought to understand the origins of war, and the atrocities committed in the Holocaust, and to build a psychology that could contribute to the possibility of peace. The first key models of intergroup relations, realistic conflict theory and evolutionary approaches, speak to this harm-doing and tell us that groups compete over scarce resources and that we are wired neurologically to fear this threat and to mobilise for this contest.

Realistic conflict theory (Bobo, Reference Bobo1983; Jackson, Reference Jackson1993; Sherif, Reference Sherif1966; Sherif et al., Reference Sherif, Harvey, White, Hood and Sherif1961) proposes that intergroup conflict arises when two or more groups have incompatible goals, or when there is a limited resource (or resources) that they each want or need. For example, groups can compete for tangible resources such as territory and money, as in wars between nations or economic competition between companies. In the case of the First World War, European powers including, among others, Germany, France, and England fought for territory, seeking to control colonies and empires that were the foundation for economic wealth and global influence. People can also compete for intangible resources, such as superior status and respect – you may think of sports, science, and arts competitions that showcase this. Sports teams may compete to lift a trophy, or scientific labs may race to publish a new discovery. Realistic conflict theory proposes that when groups compete for goals or resources, they adopt norms supporting conflict, whereas when groups seek common goals, norms that support cooperation are adopted and followed.

Key experimental research supporting this approach was published in Sherif and colleagues’ (Reference Sherif, Harvey, White, Hood and Sherif1961) Robber’s Cave experiment. The researchers hosted children in a summer camp as unwitting participants in an experiment, seeking to explore the factors that contribute to intergroup conflict and cooperation. When the campers, a group of young boys, were divided into teams and set to play competitive games, the boys developed hostility to each other, expressed in scuffles and name-calling. Then when the two teams’ trip into town was interrupted by their shared truck breaking down – an accident staged by the researchers – the boys worked cooperatively together to resolve the situation, and their emotional negativity was reduced. The experiment may seem trivial, but the model aligns with the broader concepts of rational decision-making and cost–benefit analyses (Louis et al., Reference Louis, Taylor and Douglas2005). From this perspective, we can anticipate that conflicts, wars, and systems of oppression will develop because groups seek to acquire limited resources, like water, territory, and oil, and that cooperation, peace, and equality will be fostered when shared goals are embraced, like confronting a common enemy or meeting the challenge of climate change.

The notion that groups cooperate and fight for resources both fostered and received strong intellectual support from evolutionary theories that seek to understand contemporary human behaviour as shaped by our ancestral past: competition and cooperation to survive (Burnstein et al., Reference Burnstein, Crandall and Kitayama1994; Dawkins, Reference Dawkins1976). Scholars in evolutionary theory focus on our human heritage as pack animals and propose that our brains are hard-wired for kin selection: favouring people related to us for pro-social actions and ignoring outsiders or harming them if they pose a threat. By helping our kinship group, our pack, to persist and to thrive, we are helping our shared genes and genetic material. If we help a cousin or sibling, we increase our genes’ survival and reproductive success. In addition, gender differences between men and women are proposed, in some evolutionary theories, to stem in part from different potential roles in parenting and parental investment (e.g. Buss, Reference Buss1989). More broadly, the concept of evolution is that elements that increase survival and reproduction will flourish relative to those that do not (Alexander, Reference Alexander1987; Wilson, Reference Wilson1975). Attributes and behaviours that promote survival to reproductive age and reproductive success (more living children) are reinforced over time and become more prevalent generation by generation. In this approach, evolution shapes not only our biology and neurobiology (e.g. our comparatively large brains) but also aspects of our culture.

All groups face challenges or social dilemmas where they must balance concerns for the group and for individuals, for example when managing common resources over the long term when individuals can profit selfishly in the short term (Komorita, Reference Komorita2019). Cultural concepts such as reciprocity, helping those who help you (Trivers, Reference Trivers1971) and fairness – doing what is right and punishing wrongdoers (Fehr & Fischbacher, Reference Fehr and Fischbacher2004) – are proposed to have originated and spread through human societies because of their utility in uniting groups to acquire new lands and resources, and to resist intergroup competition from invaders. Groups that did not take up these cooperative concepts and values are proposed to have been outcompeted by those that did (Whitehouse, Reference Whitehouse2024).

Less benevolently, intergroup competition and even aggression are sometimes identified as traits that have been selected for in humans both culturally and biologically. Scholars such as van Vugt (Reference Van Vugt2006, Reference Van Vugt2009) propose that groups prone to expansion and resource acquisition have often outcompeted isolationist groups, and groups embracing violence have often outcompeted those that are more peaceful. Evolutionary forces have also been proposed to drive intra-species competition, including differentiation between men and women. In the ‘male warrior hypothesis’ (van Vugt, Reference Van Vugt2006, Reference Van Vugt2009) men’s behaviour is proposed to be fundamentally shaped by men’s ancestral roles as warriors participating in violent intergroup competition. Findings that have been put forward as evidence include studies showing that men (compared to women) often endorse ethnocentric and xenophobic beliefs and behaviours more readily, and identify more strongly with their groups; that men’s cooperation with other members of their own group increases in the presence of between-group competition, whereas women’s cooperation is relatively unaffected; and that men show greater male–male competition and violence (e.g. in homicide statistics; see also Fridel & Fox, Reference Fridel and Fox2019).

A detailed critique of these theories is not focal to our book (interested readers could see, e.g. Wood & Eagly, Reference Wood and Eagly2002), but two key themes from these theories – that real resources matter (see also McCarthy & Zald, Reference McCarthy and Zald1977) and that subgroups within a broader group may experience intergroup relations differently (e.g. Buss, Reference Buss1989) – will be core messages of the chapters to come. At the same time, two other theories of intergroup relations, to which we now turn – relative deprivation and social identity theory – shall focus our attentions on how groups psychologically construct inequality, and the importance of social comparisons and subjective beliefs.

Relative Deprivation Theory: The Role of Social Comparison

In contrast to realistic conflict theory and evolutionary approaches, which focus primarily (but not exclusively) on competition for resources, relative deprivation theory (Runciman, Reference Runciman1966; Walker & Pettigrew, Reference Walker and Pettigrew1984; Walker & Smith, Reference Walker, Smith, Breakwell, Hammond and Fife-Schaw2007) teaches us that groups and group members consistently compare themselves to others, and that they are motivated to resist comparative inequality and inferiority. For this reason, even when people benefit from what, in historical terms, are high levels of security and prosperity, groups will be moved to competition and even aggression if other groups are doing better than they themselves are.

In formulating relative deprivation theory, the scholars of the 1960s were responding to the puzzling phenomenon of mass unrest at the time amid historically unparalleled wealth (e.g. Inglehart, Reference Inglehart1981, Reference Inglehart1997). Despite the economic boom of the 1950s, civil rights movements in the United States and around the world brought people into the streets protesting racism, sexism, homophobia, and war, as well as many other causes (La Macchia & Louis, Reference La Macchia, Louis, McKeown, Haji and Ferguson2016). Why did these groups protest then and not earlier, when their conditions were objectively worse, and their need for resources even higher? Relative deprivation theory put forward a psychological answer: that people are motivated by a perceived gap between their real and ideal societal status. The origin of the latter, the social ideal, is not gauged by objective criteria, but stems from comparing oneself to others.

One insight from relative deprivation theory is that social comparisons become more likely to fuel competition if new technologies (such as radio and television, or social media) and new social referents (people to whom one compares oneself) make more salient the real or perceived status and wealth of others. From this perspective, it is clear that growing social wealth can easily increase social unrest, whenever societal inequality is growing too. If the pie is getting bigger, but my share of the pie in relative terms is shrinking, I am going to be more, not less, upset and more, not less, likely to lash out.

In applying this theory to groups in the 1960s, Runciman (Reference Runciman1966) built on important research in the individual context, drawing from a large-scale study of the American army (Stouffer et al., Reference Stouffer, Suchman, DeVinney, Star and Williams1949). Stouffer and his colleagues reported puzzling discrepancies between working conditions and satisfaction across the different military branches the team studied. Military policemen, it seemed, had fewer, slower promotion opportunities – but they were more satisfied with their slow promotions than were the airmen, who were promoted relatively more rapidly. Similarly, Black soldiers in the American South were more satisfied than Black soldiers based in the North, even though the South in the 1940s was more deeply racist and segregated. The reason for these discrepancies, Stouffer and his team realised, was the social comparison referents of the different soldiers. The military policemen rarely encountered air force personnel – they compared their promotions to those of their colleagues, other policemen. Similarly, Black soldiers in the South compared their personal conditions to those of Black civilians in the South, not to the soldiers in the North, with whom they rarely interacted. In the context of their comparisons of relative advantage, the objectively disadvantaged individuals had every reason to be happy – and they were!

When the unrest of the 1960s broke out, scholars like Runciman (Reference Runciman1966) and Pettigrew (Reference Pettigrew1967, Reference Pettigrew2015) realised the same theory of relative deprivation could be applied on a group level, and would predict changing intergroup relations. Runciman (Reference Runciman1966) developed a distinction between individual (or egoistic) relative deprivation and collective (or fraternal) relative deprivation. If my group is seen to be doing worse than your group, in relative terms, this collective relative deprivation is the critical prompt for social turmoil and protest. For this reason, increased awareness of group inequalities can lead to worse intergroup relations, even when conditions for all groups are improving.

Is it not possible, however, to be aware of inequality without outrage and resentment? Doesn’t intergroup inequality often persist for decades or centuries without intergroup competitiveness and aggression? Of course! Later scholars in relative deprivation found that angry resentment, the emotional component of relative deprivation, is the more powerful determinant of ill-being and competitive responding, rather than cognitive or intellectual awareness of inequality per se (Smith et al., Reference Smith, Pettigrew, Pippin and Bialosiewicz2012). Why might some groups who are aware of being unequal not feel anger? Another theory soon arose that could speak to this phenomenon: social identity theory.

Social Identity Theory

Social identity theory was put forward by Tajfel and Turner (Reference Tajfel, Turner, Austin and Worchel1979), and, like relative deprivation theory, it starts from the premise that individuals and groups compare their status to others, and that perceived inequality is the root cause of intergroup competition, aggression, discrimination, and violence. Where the theory leapt ahead of alternatives, such as realistic conflict theory and relative deprivation theory, was in spelling out the factors that could inflame or suppress competitive responses to inequality in testable hypotheses. Later scholars developed from social identity theory a rigorous understanding of social comparison processes that underpin people’s awareness of their own identities, sometimes identified separately as self-categorisation theory (Turner et al., Reference Turner, Hogg, Oakes, Reicher and Wetherell1987). Together, social identity theory and self-categorisation theory teach us that groups aware of inequality have different responses, based on perceptions of how groups are related to each other: the legitimacy and permanence (stability) of the inequality, and the possibility of the intrusion of outsiders into their groups. Self-categorisation theory and social identity theory (now often grouped as the social identity approach; Hornsey, Reference Hornsey2008) also detail the group processes that shape particular types of intergroup competition, and put forward a model that could be used to explain and predict social influence and action in contexts from protest to politics. We’ll take a first pass at introducing the social identity approach in this chapter, but you will encounter the theory again and again throughout this book.

Tajfel and Turner (Reference Tajfel, Turner, Austin and Worchel1979) picked up the idea of individual and group comparisons put forward by Runciman (Reference Runciman1966) and others, and proposed a first insight: that people have both personal identities (I) and social identities (we), and that these could be understood as ends of a continuum of increasing psychological inclusiveness (see also Turner et al., Reference Turner, Hogg, Oakes, Reicher and Wetherell1987, Reference Turner, Wetherell and Hogg1989). At any given time, individuals can be thinking of themselves in terms of their personal identities or as members of a group.

To understand whether individuals experience themselves as individuals (I) or as group members (we), Tajfel, Turner, and colleagues proposed that three aspects of the context matter. First, the subjective awareness of an identity depends upon people’s chronic identification: how regularly their identities are activated, how strongly they feel connected to others in their group, and how much the identity is a source of positive distinctiveness (Cameron, Reference Cameron2004). Two people may both be members of a religion, for example, but one who regularly engages in religious practices and interacts with other members of their faith will be much more likely to be consciously aware of their religious social identity in everyday life.

Second, the salience of a social identity depends on two situational factors (Turner et al., Reference Turner, Hogg, Oakes, Reicher and Wetherell1987). One factor is the comparative context: the presence of people in an interaction who are outgroup members (outsiders who are members of a different group) versus people who are ingroup members (insiders belonging to the same group). The second factor is the normative context: the alignment of the content of the social interaction to the social rules and standards of the group. For example, I may feel much more like an American, an Austrian, or an Australian in a multinational and diverse group, compared to when I am interacting solely with my fellow citizens, when our nationality fades into the psychological background. More broadly, if I am interacting with people who all belong to one of my groups, who are ingroup members, I am less likely to be aware of my group membership than if I am interacting with some ingroup members and some outgroup members. The arrival and departure of new people in an interaction or situation can change my identity awareness.

But this depends on the normative context: how we are following the social rules of our group. If I am in a group of fellow citizens and we start to discuss international affairs, my national identity will become more salient due to the learned association between the topic and my nationhood. I may become consciously aware of my social identity as an Australian, for example, if we start to discuss Australia’s participation in past international wars, or an international cricket match. Thus, in the course of a single conversation, I might experience periods of feeling aware of myself as an individual, as a fan of a sports team, as a woman, as an Australian, and so on, depending on the various changes of conversation topic that occur.

According to the social identity approach, these changes matter because the social identity that is salient for me at any given time shapes my emotions, my attitudes, and my actions by channelling shared emotions, attitudes, and actions. It is proposed that individuals derive their self-concept from their group membership, with flow-on consequences for social comparison, self-esteem and well-being, and action choices. However, different individuals may engage in different action choices from the same social comparison. For example, if I become aware of my gender as a woman because of a sexist remark, this awareness of discrimination and collective relative deprivation for women may make me angry and cause me to speak out. But it often doesn’t – sometimes I might laugh it off, or keep uncomfortably silent, or change the topic, or leave the room. I might even join in the laughter, experiencing the favour and validation of others if I seek to stay included as ‘one of the boys’.

Social identity theory made a third important contribution to the study of intergroup relations by focusing on those different choices and seeking to speak to why those choices might diverge. Tajfel and Turner (Reference Tajfel, Turner, Austin and Worchel1979) identified three socio-structural beliefs that make the difference between grumbling and taking a stand. Relative deprivation theory focuses on resentment and collective action as a natural outcome of deprivation perceptions (e.g. Runciman, Reference Runciman1966). However, scholars in social identity research have shown that when intergroup inequality is seen as stable (unlikely to change) and/or legitimate (socially justified), and when the boundaries between groups are permeable (people are able to leave one group and join another), people will often react at an individual level instead of taking action together, even in conditions of great inequality. Individual action is also likely if people don’t identify strongly as members of a group – for example, a person who is not active in their faith may be less likely to notice or respond to inequalities between religious groups than someone who is more active. But even if they do care a great deal about their group’s relatively low position, individuals in a poor neighbourhood, or a low-wage profession, may be unlikely to advocate for the group’s higher status. Instead, they may generally seek to move, or to change jobs: a strategy of individual social mobility (Ellemers et al., Reference Ellemers, Spears and Doosje1997). When the option exists to leave a low-status group, group members are more likely to disidentify, or psychologically distance themselves from the group, and this psychological distancing may also be a precursor to leaving the group.

Social identity scholars have also drawn attention to the multiple possible dimensions of intergroup comparison that could be considered for judgements of relative deprivation of inequality, and how this affects people’s choices in reaction to inequality between groups. For example, if I want to compare men and women, should I compare each group’s pay, or experience of violence, or intellectual acumen, or moral integrity? Social identity scholars have found that when groups are disadvantaged by one intergroup comparison (e.g. wealth) in a way that is stable, and when there is no way of changing groups (impermeability of group boundaries), group members often choose to focus on different dimensions on which they may feel more advantaged: a strategy of social creativity (Lemaine, Reference Lemaine1974; van Bezouw et al., Reference van Bezouw, van Der Toorn and Becker2021). Thus, compared to theories that came before that over-predicted protest, confrontation, and intergroup competition, from its beginnings, social identity theory more powerfully considered a full range of individual and group conciliatory responses as well. However, not all aspects of its intellectual legacy are equally well studied empirically, as we shall see in Chapters 2 and 3.

The Engine of Truth

A great deal of research and advocacy approaches system change as a struggle to discover and disseminate truthful information in order to dispel ignorance and combat falsehood. While the existence of ‘truth’ is contested, our approach is that socially constructed information varies in its integrity – its truthfulness – defined as alignment with the social and physical world as it is perceived and interpreted by the audience. We propose that there is motivational power in speaking truth. Within the field of intergroup relations, early psychologists even embedded this distinction into their definitions of prejudice and discrimination. For example, in an influential early text, Allport (Reference Allport1954) proposed that prejudice is an unjustifiable negative attitude towards an individual based on their group membership: an irrational hostility on the part of advantaged group members. From this perspective, segregation and misleading circumstances beget stereotypes, and the truth is liberating. Accordingly, the solution is simple: social integration, which will bring about contact with disadvantaged group members and reveal each fully to the other. According to contact theory (Allport, Reference Allport1954; Paolini et al., Reference Paolini, White, Tropp, Turner, Page-Gould, Barlow and Gómez2021; Pettigrew, Reference Pettigrew1998), when groups are brought into contact with each other, advantaged group members’ false stereotypes may be shattered, and pro-social intergroup relations allowed to form. Of course, Allport knew that it was more complicated than that – as we shall see in what follows – but this exciting, simple possibility is one positive hypothesis arising from contact theory.

There’s no doubt at all that in the right conditions, this happy consequence may be observed: contact between groups can dispel false stereotypes and open the door to cooperation and harmony (e.g. Paolini et al., Reference Paolini, White, Tropp, Turner, Page-Gould, Barlow and Gómez2021). There is also no doubt at all that it’s not inevitable for contact to promote harmony! There’s another engine that’s required for truth to work to improve intergroup relations – or vaccination rates, or financial behaviour, or any other area where scientific knowledge can be at odds with mass action. Scientific truth must become social truth – it must become supported by group norms.

The Engine of Norms

Group norms – social rules, or standards for behaviour (Smith & Louis, Reference Smith and Louis2009) – structure social realities and decisions. In Allport’s (Reference Allport1954) formulation of contact theory, this ground truth was acknowledged as a precondition for contact to work. Contact would only improve individuals’ intergroup attitudes and actions, Allport theorised, when that contact occurred framed by norms of cooperation, equal status, shared goals, and authority support. If social norms support inequality, discrimination, and exploitation, those forms of unequal contact can be experienced as legitimising them instead of undermining them. That is why so many slave owners could interact with slaves, through centuries of profound inequality, without feeling morally challenged to question the hierarchy they were in. In a similar vein, men, women and children can interact regularly in patriarchal societies with associated patriarchal norms, in which children and women are being coerced and violently controlled by men, without men feeling moved to challenge the system. Over decades or centuries, even millennia, people who are members of different castes, social classes, or advantaged and disadvantaged professions or ethnic groups have been able to interact on a daily basis, and find this contact, if anything, reinforces the status quo. So, what are these legitimising or challenging norms, these powerful social standards? Where do they come from, how do they operate, and how do they change?

According to research on group processes, social norms are explicitly taught and socialised by parents, teachers, and peers, and they are also inferred from others’ actions and the status quo more broadly. We have already begun to discuss these principles in relation to social identity theory, which proposes that when individuals identify themselves as group members, they enact the social norms of their group, often quite unconsciously (Turner et al., Reference Turner, Hogg, Oakes, Reicher and Wetherell1987). For example, when teaching a class, I may speak for 30 minutes without interruption; when relaxing with friends, I may take turns to speak and listen every few minutes. This change in speaking behaviour may not be the result of any formal rule or conscious choice (‘I had better let my friend talk now’), but rather a result of my obedience to the learned norms of the different identities that are salient for me as a teacher versus as a conversation partner. Similarly, as a student, I might feel quite relaxed about listening to a teacher speak for 30 minutes, whereas if I were listening to a friend who spoke for 30 minutes without interruption, I might feel my friend was very unusual and rude. Thus, different roles within the same society may have different norms, and when people identify with those roles, people’s behaviour may change accordingly. But more broadly, different societies have different norms that people obey unthinkingly and do not challenge. In the 21st century, for example, few people might consciously choose whether or not to wear clothes every day. Instead, people engage in these behaviours because they are normative, typically without ever having made a conscious decision to do so.

What is relevant to our discussion of norms as a necessary accompaniment to the engine of truth is that research has found that social norms can guide perceptions of ambiguous stimuli and even override clear-cut realities. The classic studies in this area were conducted by Sherif (Reference Sherif1936) and Asch (Reference Asch and Guetzkow1951, Reference Asch1952). In Sherif’s (Reference Sherif1936) research on ambiguous stimuli, participants in a dark room were asked to estimate the autokinetic movement of a small dot of light on a screen. The dot of light was actually stationary, but due to the lack of visual cues in the dark room, participants perceived it as moving. When participants were tested individually, their estimates of the dot’s movement varied widely. However, when participants were tested in groups, their estimates became more similar and converged towards a group norm. Interestingly, when group members were rotated periodically so that newcomers came into an existing group, they tended to converge to the norm as well – and the influence of the norm persisted even when the group members who originally created the norm were gone! Even in groups of strangers with limited interactions, shared realities become a basis for perceiving, interpreting, and reacting to stimuli.

But what happens if there is a less ambiguous stimulus – what if there is a clear right and wrong? Do norms still matter? Yes, they certainly do, as the work of Asch (Reference Asch1952) showed. Asch created an experiment in which participants were asked to select which of a set of three clearly different lines (short, medium, and long) matched a target line. In a control condition, participants answered alone, and error rates were lower than 1% on this task: they could easily see which line matched. In the conformity condition, participants were seated in a group of six people, and the group members each answered the same question out loud: always in the same order, with the participant coming last. The participant was not informed that the other five other group members were confederates of the experimenter, who were responding according to instructions, and only pretending to be participants. All participants repeated the judgement task multiple times, and in 12 critical trials, all five previous speakers (the confederates) selected an incorrect line. What would participants do? Unexpectedly, 75% gave at least one incorrect answer! Only 25% correctly perceived or reported the truth all the time, in the face of group members’ false claims.

As we shall see in later chapters, this conformity effect could be weakened by dissent, and didn’t affect all participants equally – but it is a startling base rate of influence. If norms can distort people’s ability to perceive or report simple truths, perhaps it is not surprising that norms also have been found to influence social actions, like harm-doing (Crutchfield, Reference Crutchfield1955; Milgram, Reference Milgram1963), helping (Darley & Batson, Reference Darley and Batson1973), and decision-making broadly (Bicchieri, Reference Bicchieri2006; Smith & Louis, Reference Smith and Louis2009). For the purpose of this book, and as we shall elaborate in later chapters, it is particularly relevant to note that norms have been shown to influence intergroup behaviour and social systems powerfully. Norms affect when group members are willing to discriminate and even kill people from other groups, versus when they support them with charitable giving or foreign aid.

Where do these norms come from? We have already discussed two distinct paths – norms that form ‘bottom up’ from the discussions and input of peer group members (Sherif, Reference Sherif1936), and norms that are created ‘top down’ by leaders shaping followers, or in this case an experimenter shaping confederates (Asch, Reference Asch1952). These inductive (bottom-up) and deductive (top-down) paths to norm formation (Postmes et al., Reference Postmes, Haslam and Swaab2005a, Reference Postmes, Spears, Lee and Novak2005b) both allow for norms to come in from the external world – for a person to be a ‘blank slate’ onto which a group may write norms of any kind, from politeness to promiscuity, from kindness to killing. In ‘bottom-up’ or inductive processes, however, group members’ actions also contribute to the norms, and persistent dissent or deviance may therefore help to reset a norm and create social change.

Beyond this general point, we can observe that the four theories mentioned earlier – realistic conflict, evolutionary approaches, relative deprivation, and social identity theory – differ in their approaches to norms. The first two emphasise that norms form when they give functional benefits for resource acquisition, and the latter two allow for construction of norms for multiple purposes. That is, realistic conflict theory (Bobo, Reference Bobo1983; Jackson, Reference Jackson1993; Sherif et al., Reference Sherif, Harvey, White, Hood and Sherif1961) proposes that more competitive or cooperative norms for a particular group will be adopted because they are more functional for the group – they will be afforded or evoked by environmental opportunities. When a cooperative group meets a threatening environment, they will change by adopting norms for competitive, aggressive, and defensive behaviour. Similarly, as we saw in the Robber’s Cave experiment when the truck broke down, if a competitive group enters an environment with material benefits flowing from peaceful cooperation, standards of action change to support more peaceful, cooperative actions.

This flexibility and alignment to environmental opportunities is consistent with an evolutionary perspective, which emphasises that humans have evolved both biologically and culturally in contexts where they exchanged resources or favours with others (Cosmides & Tooby, Reference Cosmides, Tooby, Barkow, Cosmides and Tooby1992; Tooby & Cosmides, Reference Tooby, Cosmides, Barkow, Cosmides and Tooby1992), and which they also shape (Eidelson, Reference Eidelson1997). Evolutionary scholars propose that there are psychological and cultural mechanisms that serve as domain-specific adaptations to support group cooperation and intergroup competition, such as norms for detecting and punishing cheaters, even when such punishment is costly to the self. Groups that adopt such norms are more able to avoid exploitation and free-riding, to cooperate with each other to access resources, and to compete with other groups. Individual group members are motivated to conform because the approval of others has material implications for themselves: belonging to a group is a precondition for safety, security, and reproductive success, and a high-functioning group, in particular, is better placed to acquire safety, security, and reproductive success for its members.

In contrast, relative deprivation theory and social identity theory both emphasise groups’ capacity to use norms to construct feelings of higher or lower safety, security, and status, in ways that may or may not be functional for the group’s material resource acquisition or security. In relative deprivation theory (Runciman, Reference Runciman1966; Stouffer et al., Reference Stouffer, Suchman, DeVinney, Star and Williams1949), as we have noted, it is the focus on a particular comparison referent that leads to more or less of a sense of grievance or deprivation, regardless of objective conditions. Teenagers in one context may be more content because they compare themselves with similar neighbours and classmates, whereas in another context they may feel ill-being and resentment, because they compare themselves to glamourous influencers on social media. Factors that affect the choice of comparison target change deprivation perceptions, emotions, and actions, whether or not that is in the best interests of the perceivers, and sometimes even when it is harmful for them. For example, many psychologists have found that social media comparisons for teenagers can be dysfunctional: they can increase anxiety and depression, and decrease productivity (Kross et al., Reference Kross, Verduyn, Sheppes, Costello, Jonides and Ybarra2021). The capacity of group norms to persist to support behaviours that are harmful to members of the groups is beyond dispute, from unhealthy eating (Louis et al., Reference Louis, Davies, Smith and Terry2007) and wasteful consumerism (Hamilton, Reference Hamilton2010) to religious or racial prejudices (Crandall et al., Reference Crandall, Eshleman and O’Brien2002). Are there factors that increase the likelihood of irrational resentment and deprivation flourishing? Or of unwarranted complacency and quietude persisting in objectively disadvantaged groups?

For social identity scholars (Tajfel & Turner, Reference Tajfel, Turner, Austin and Worchel1979; Turner et al., Reference Turner, Hogg, Oakes, Reicher and Wetherell1987, Reference Turner, Wetherell and Hogg1989), shared normative beliefs in illegitimacy, instability, and impermeability are factors that will afford or evoke norms of social competition. In contrast, normative beliefs of legitimacy, stability, and permeability will allow or guide a group that is objectively disadvantaged to use strategies of individual mobility or social creativity. Both theories suggest that the nature of the social comparison groups is a powerful input to groups’ normative change. However, social identity theory offers a richer understanding of the persistence of social hierarchy.

While it is certainly true that some harmful group norms and intergroup systems can persist for centuries unchallenged, it is also the case that they can change with unexpected rapidity. What explains that? We shall address the complexity of norm change in more detail in Chapters 4 and 5, looking at ideologies (shared belief systems). But first we turn our attention to the last engine proposed to drive system change: the role of leaders and followers.

The Engine of Leadership

If truthfulness (or lies) and norms can motivate cooperative or destructive intergroup relations, who speaks the truth? And who contests and changes the norms? One popular answer is particular leaders: Martin Luther King, Jr. may be given credit for the civil rights movement in the United States; Gandhi for the independence of India; or Hitler for the devastation of World War II. How credible are these attributions? Do individuals really change systems?

So-called individual difference explanations of intergroup relations focus on the ways that some individuals are more or less cooperative or hostile within a given context than others (Cohrs et al., Reference Cohrs, Kämpfe-Hargrave and Riemann2012; Hodson & Dhont, Reference Hodson and Dhont2015). This class of theories predicts that people who are more confrontational or cooperative behave this way because of differences in their individual values, personalities, and ideologies. For example, people who value power and dominance more strongly may be more ready to support intergroup aggression. We do touch on this literature in Chapter 4, but this book focuses primarily on how the needle moves for societies and systems as a whole. Why is the 21st century so much more supportive of equality than the 11th century was? Why do parents in many societies now avoid punishing children physically, whereas in centuries past this was common? At face value, individual difference explanations cannot answer the question of how groups change: if more socially dominant people push for hierarchies, and less socially dominant people for inclusion and equality, how does that lead to civil rights? Or to new eras of despotism? In Chapter 11, we shall dive deep into the mechanisms that allow individual innovators – leaders, artists, scientists – to instigate, contribute to, or block social change. The purpose of the present section is narrower, however: it is to make readers aware that for some scholars and many community members, it is leaders and followers that create system change. They are the third engines of progress and retrogress that we discuss.

The definition of leadership is very much contested (Ellemers et al., Reference Ellemers, De Gilder and Haslam2004), but let us presume that key aspects of leadership include their ability to discern the truth and broadcast it to group members – in so doing, they become the conductors of the engine of truth. And let us presume that leaders also have the ability to direct and magnify the efforts of others towards the achievement of a common goal – in so doing, leaders become the conductors of the engine of norms. For example, a successful leader such as Martin Luther King, Jr. or Ghandi may contest norms that are unfair, based on false information, or unproductive for the group’s goals. In so doing, they might improve the status and power of the group as well as its efficiencies, or its moral integrity, or intragroup relationships. Such leaders might receive the recognition and respect of their fellow group members.

In contrast, an unsuccessful or destructive leader might embrace unfairness, falsity, and inefficiency, promoting divisions within the group and reducing group members’ security, health, and prosperity. They might ultimately lose power and attract the derision and scorn of their group, but do a lot of damage along the way. In the present section, our aim is to consider these leaders, and to introduce the concept of leadership according to two very different perspectives: the theory of great (or not so great) individuals, and the social identity approach to leadership as a group process.

Great Men and Women. According to Carlyle (Reference Carlyle1841), the history of the world is the history of great men: leaders like George Washington, Churchill, Napoleon, Marx, or Buddha, as people who turn the page of history, and who introduce new upwards (or downwards) trajectories of social change for groups and societies through their actions. Different theories of greatness locate leaders’ successes in different qualities they possess. Some scholars stress that great leaders have certain traits or attributes that make them inherently more effective in their role, such as charisma, intelligence, and self-confidence (Stogdill, Reference Stogdill1974). Others focus on ideas that meet the challenge of the moment: transformational leaders are proposed to have critical insights or visions that inspire followers to perceive the world in a new way, and unlock a new sense of purpose and meaning that motivates action for the good of the group (Bass, Reference Bass1985). A third group of scholars stress leaders’ values, proposing that great men and women may be distinguished by their humility and servant ethic, focusing on the well-being and needs of followers and developing their followers’ abilities and potential to the utmost (Greenleaf, Reference Greenleaf1977). What these theories have in common is the view that a leader who is successful in one context (e.g. in one company or country) is also likely to have the capacity to lead in another context, if they were transplanted. In these approaches, leaders’ potential arises from their personal aptitudes, insights, or values rather than necessarily being specific to a particular context.

Leaders as creators of shared social identities. In contrast, the social identity approach to leadership (Haslam et al., Reference Haslam, Reicher and Platow2020; Haslam & Reicher, Reference Haslam and Reicher2012; Steffens & Haslam, Reference Steffens and Haslam2013; Steffens et al., Reference Steffens, Haslam, Reicher, Platow, Fransen, Yang, Ryan, Jetten, Peters and Boen2014, Reference Steffen, Richardson, Rockström, Cornell, Fetzer, Bennett and Sörlin2015, Reference Steffens, Mols, Haslam and Okimoto2016) locates leaders’ influence in the relationship of leaders to particular groups. A successful leader in one context and for one goal is not necessarily successful or a leader in another. In the social identity approach, it is the capacity to define and symbolise the group’s values and goals in a particular context that empowers leaders. In that specific context, leaders co-construct a social identity with other group members, followers, that creates a shared sense of reality, meaning and purpose, allowing leaders to channel and amplify the efforts of group members towards particular goals. It is the articulation of these situationally shared goals, values, and norms that is the foundation for effective leadership and follower action. The important corollary, then, is that when contexts and groups change, leaders must change to retain their influence. Without such change, the capacity of leaders to influence their followers, the trajectory of their groups, and the broader society is undermined (Blackwood & Louis, Reference Blackwood and Louis2017).

As one example of the truth of this model, we can consider Churchill, who successfully rallied Britain during World War II in part due to his immense courage and pugnacity (Best, Reference Best2001). Churchill is frequently put forward as a great man – the greatest leader (for some) of the West in the 20th century. From the perspective of the great man theory, it is puzzling to observe the valleys of his career. For example, Churchill was voted out immediately after World War II due in part to questions about his capacity to manage unemployment, and he also is now judged harshly by historians of colonialism (e.g. Catherwood, Reference Catherwood2015). But from a social identity perspective, it is not surprising at all to see that his leadership met some challenges superbly and others weakly. From this perspective, Churchill’s capacity to meet the needs of the moment – his greatness in uniting Great Britain to resist adversity and war – would not necessarily be expected to flow through to greatness in every other sphere of leadership. And indeed, it did not.

Closer to home within social psychology, we might also consider the legacy of Henri Tajfel, the brilliant intellectual pioneer who gave us social identity theory, and who influenced tens of thousands of students and scholars so positively, including the authors of this book. In 2019, Tajfel’s name was stripped from the lifetime achievement medal of the European Association of Social Psychology (EASP), which he had helped to found. The reason for this disgrace? In the wake of the #MeToo movement, EASP chose to distance itself from Tajfel’s record as a sexual harasser, searingly documented by Young and Hegarty (Reference Young and Hegarty2019). Ironically, it is the very social identity theory that Tajfel created that offers us a lens to understand leaders’ fitness and unfitness, seeing through the labels of great men and women to the normative context in which the actors are situated. Social identity theory tells us that there are not great men and women independent of their local context – and that great moral courage, insight, and clarity in one area are no guarantee of greatness in another. A leader who is fit for one goal and represents well one part of their group may yet fall short for other goals and harm the interests of other group members. And when the norms of a group change, the judgements of historical leaders change. Tajfel would have expected this.

With these points in mind, we can turn to considering how systems change – taking up the struggles for equality of disadvantaged groups (in Chapter 2) as well as the quest for power of advantaged groups (in Chapter 3). Before we do so, however, let us turn to a final interesting question: Do groups act? Or do only individuals have agency?