Iterated Insights

William Wesley Reser, Brittany Axworthy Reser, and Jared Edward Reser

Abstract

Psychopathy and antisocial personality traits are usually understood as harmful deviations from normal social functioning, or as selfish strategies by which individuals exploit cooperative groups. Existing evolutionary accounts have interpreted psychopathy as a frequency-dependent cheating strategy, a hawkish aggression strategy, or a fast life-history strategy shaped by harsh and unpredictable environments. This article proposes a complementary hypothesis: some psychopathic and antisocial traits may also have been tolerated because they increased a group’s apparent formidability during intergroup conflict. Individuals with reduced fear, reduced empathy, emotional detachment, and a willingness to use extreme aggression may have functioned as deterrents, enforcers, raiders, retaliators, intimidating subordinates, or dangerous allies. Such individuals would often impose costs on their own groups, but when their aggression was directed outward, they may have made rival groups more cautious. We call this the tolerated-danger hypothesis. We also connect this hypothesis to predictive adaptive response theory, suggesting that early cues of deprivation, violence, famine, or social instability may bias some individuals toward a more fearless, callous, and opportunistic phenotype. This article does not argue that psychopathy is generally beneficial, or that it evolved for the good of the group. It proposes only that intergroup conflict may have created one narrow selection pressure by which some antisocial traits were sometimes rewarded, channeled, or tolerated.

1. Introduction: The Dangerous Member of the Group

Psychopathy presents an evolutionary puzzle. Psychopathic and antisocial traits are associated with deception, exploitation, aggression, lack of remorse, shallow affect, impulsivity, and disregard for the rights of others. These traits are costly to families, partners, communities, and societies. They are also costly to the individual when they lead to retaliation, imprisonment, exclusion, or social failure. For that reason, psychopathy is usually treated as a pathology, a developmental disturbance, or a destructive personality configuration.

Yet psychopathic traits persist. They are distributed dimensionally in the population, they are partly heritable, and they appear in multiple social settings. This has led evolutionary theorists to ask whether some psychopathic traits may have been maintained because they occasionally produced fitness benefits. Linda Mealey’s influential sociobiological model proposed that sociopathy can be understood partly as a frequency-dependent life strategy, integrating proximate developmental factors with ultimate evolutionary explanations.  Later work has examined psychopathy as a possible adaptive strategy, while also warning that the evidence is not strong enough to choose decisively among adaptation, developmental pathology, and mutation-load explanations.

Most evolutionary explanations focus on what the psychopathic individual gains. A person with low empathy, low guilt, and manipulative skill may exploit trust, deceive cooperators, pursue short-term mating opportunities, intimidate rivals, or take resources without reciprocating. These theories are important, but they leave open another possibility.

A dangerous person may be costly inside the group but useful at the boundary of the group.

This article develops a hypothesis proposed by William Wesley Reser: psychopathic and antisocial traits may have been maintained partly because, under conditions of intergroup conflict, some groups tolerated dangerous individuals who made the group more frightening to outsiders. The idea is not that psychopathy is generally good for groups. It is not. The idea is narrower: in ancestral environments where raids, revenge, territorial conflict, male coalitions, and group reputation mattered, a small number of fearless, callous, aggressive individuals may have increased a coalition’s apparent danger.

A group might not love such a person. It might fear him, manage him, punish him, reward him, and keep him close. But if his aggression was directed outward often enough, he could become a dangerous asset.

2. Existing Evolutionary Accounts: Cheaters, Hawks, and Fast Life-History Strategies

Several ideas in the literature already point toward an evolutionary interpretation of psychopathy. The first is the cheater hypothesis. Cooperative groups depend on trust, reciprocity, reputation, guilt, and empathy. A small number of individuals who do not feel these constraints as strongly may exploit the cooperative instincts of others. In this view, psychopathy functions as a selfish strategy that works best when rare. If everyone were psychopathic, trust would collapse and the strategy would lose its advantage. But when most people are cooperative, a minority of exploiters can sometimes benefit.

The second is the hawk hypothesis. In evolutionary game theory, a “hawk” is an organism that escalates conflict, uses aggression, and refuses to back down. Kent Bailey’s “warrior hawk” commentary argued that violent competition among ancestral bands may have been a major evolutionary precursor of sociopathy. He suggested that the violent sociopath may be better understood as a warrior hawk than merely as a failed cooperator.  Book and Quinsey later proposed that psychopaths may combine both cheating and hawkish aggression. Their “cheater-hawk” framing treats psychopathy as involving both social exploitation and aggression.  A later study testing the cheater-hawk hypothesis found that primary psychopathy was related to cheating behavior as well as direct and indirect aggression in a noninstitutionalized sample.

The third major account is the fast life-history strategy. Harsh, unpredictable environments may favor present-oriented behavior, short-term mating, risk-taking, aggression, low trust, and opportunism. From this perspective, antisocial traits may sometimes reflect developmental calibration to a world in which long-term cooperation is unreliable and vulnerability is dangerous. Evolutionary reviews of psychopathy have discussed both adaptive-strategy models and contingent-shift models, in which individuals respond developmentally to environmental conditions.

These theories are important background, but they mostly ask how psychopathic individuals might benefit themselves. The present hypothesis asks a different question: why might a group tolerate them?

The difference matters. A cheater exploits the group. A hawk intimidates opponents. A fast life-history strategist adapts to danger and uncertainty. But a tolerated-danger individual may occupy an additional niche: he may be dangerous enough to harm insiders, but useful enough against outsiders that the group does not immediately expel him.

3. The Tolerated-Danger Hypothesis

The tolerated-danger hypothesis proposes that psychopathic and antisocial traits may have been maintained partly because groups sometimes tolerated dangerous individuals when those individuals increased coalitional deterrence against outsiders.

In ancestral environments, groups were not only collections of cooperators. They were coalitions embedded in dangerous social landscapes. Neighboring groups could compete over territory, food, mates, status, revenge, and survival. Under such conditions, the perceived formidability of a group could matter enormously. A group that appeared easy to threaten, exploit, or attack might invite predation. A group that appeared dangerous, vengeful, and hard to intimidate might deter conflict before it began.

A psychopathic or antisocial individual could contribute to this deterrent effect in several ways. He might serve as a raider, enforcer, retaliator, bodyguard, executioner, intimidator, or dangerous subordinate to a leader. He might be willing to harm outsiders when others hesitate. He might show less fear in confrontations. He might be less inhibited by empathy, guilt, or pity. He might be more willing to escalate. He might cultivate a reputation for being unpredictable or cruel.

The key point is not that such a person is morally good, internally cooperative, or generally beneficial. He may be a liability. He may manipulate allies, intimidate weaker group members, disrupt families, or challenge leaders. But if his dangerousness is directed outward often enough, and if the group can control or channel him enough, he may create a net advantage under some conditions.

This is not a claim about group selection in the strong sense. The individual must benefit too. A tolerated-danger individual may gain protection, status, food, mating opportunities, access to leaders, spoils from conflict, or freedom from punishment. He may be useful to the coalition, but he remains motivated by self-interest. The group tolerates him because he is useful. He remains with the group because the group is useful to him.

This may be one reason why human cultures so often contain the archetype of the dangerous lieutenant, the feared enforcer, the ruthless warrior, or the violent subordinate. The leader may not trust him completely. The group may not admire him fully. But his willingness to cross lines can make him valuable.

The tolerated-danger hypothesis therefore adds a group-facing layer to earlier evolutionary theories. Psychopathy may not only be a strategy for exploiting cooperators. It may also be a strategy that some cooperators tolerate when external enemies are present.

4. Selective Restraint, Conditional Loyalty, and the Psychopathic Henchman

A common mistake is to imagine psychopathy as total disinhibition. In reality, many individuals with psychopathic traits are not simply out of control. Some are capable of strategic restraint. They may break moral rules, manipulate others, intimidate people, and violate trust, while still avoiding the most obvious forms of punishment.

This distinction is crucial. The group-tolerated psychopath cannot be entirely uncontrolled. If he indiscriminately harms insiders, he becomes too costly. He may be expelled, punished, abandoned, or killed. For the tolerated-danger niche to exist, he must restrain himself just enough to remain inside the coalition.

Modern research on “successful psychopathy” supports the idea that some people with psychopathic traits inhibit antisocial impulses better than others. Lasko and Chester’s longitudinal study tested a compensatory model in which relatively successful psychopathic individuals develop greater self-regulatory control over antisocial impulses. They found that higher initial psychopathy was associated with steeper increases in inhibitory control and suppression of aggression over time, especially among offenders who reoffended less.  A systematic review similarly notes that “successful psychopathy” is often conceptualized through moderated expression, where moderate levels of psychopathic traits or particular trait configurations may permit functioning better than extreme, uncontrolled forms.

There is also evidence that participation in coalitionary aggression can benefit individual males. Gilby and colleagues analyzed 14 years of genetic and behavioral data from Gombe National Park and found that male chimpanzees who participated in coalitionary aggression increased their chances of siring offspring compared with other males of similar dominance rank. Participation in coalitionary aggression also increased a male’s chance of rising in rank, which can itself improve future reproductive prospects.

This supports an important refinement: psychopathy may involve selective inhibition, not merely poor inhibition. A psychopathic individual may learn where the line is. He may avoid prison, avoid exile, avoid direct betrayal of the leader, avoid harming high-value allies, or avoid actions that would provoke collective punishment. His restraint may not come from empathy, guilt, or conscience. It may come from self-interest.

In an ancestral group, being expelled could mean death. A person could lose access to food sharing, mating opportunities, protection, kin support, and shelter. Even a low-empathy individual would have strong reasons to avoid total exclusion. Like a person suppressing a powerful impulse when the stakes are high, the tolerated-danger individual may be able to restrain antisocial behavior inside the group while expressing it more freely outside the group.

This is also why the “psychopathic henchman” archetype is useful. In movies, the villain often has a ruthless subordinate who is not loyal in the warm, empathic sense. He is loyal because the leader gives him status, purpose, protection, money, permission, identity, or sanctioned opportunities for aggression. His loyalty is conditional, instrumental, and self-interested. But it can still be real enough to make him useful.

The same may have been true in ancestral contexts. A psychopathic subordinate may have stayed close to a leader because the leader protected him. A leader may have tolerated him because he was willing to do frightening things. The group may have disliked him but still valued his usefulness when facing outsiders.

The group-tolerated psychopath, then, is not necessarily someone who cannot control himself. He is someone who controls himself just enough to remain inside the coalition, while becoming more dangerous when turned toward outsiders.

5. Comparative Clues from Chimpanzee Coalitional Aggression

Comparative evidence from chimpanzees provides a useful, though limited, analogy for the tolerated-danger hypothesis. Chimpanzees cannot be diagnosed with human psychopathy. However, chimpanzees do show individual differences in traits that resemble components of psychopathy, including boldness, aggression, dominance, disinhibition, and meanness. Researchers have even applied the triarchic model of psychopathy to chimpanzees, measuring chimpanzee analogs of boldness, meanness, and disinhibition. In one study of 178 socially housed chimpanzees, boldness showed significant heritability in the full sample, and all three triarchic dimensions showed significant heritability among mother-reared chimpanzees, with both genes and environment contributing to the relationships among these traits.

This matters because chimpanzees also engage in severe coalitionary aggression. Long-term field studies have documented territorial patrols, coordinated attacks, intercommunity killings, and violence directed at isolated or vulnerable individuals. A major 2014 study in Nature compiled data from 18 chimpanzee communities and 4 bonobo communities over five decades. The authors reported 152 chimpanzee killings, with males representing 92% of attackers and 73% of victims. Most killings, 66%, involved intercommunity attacks, and attackers typically outnumbered victims by a large margin, with a median ratio of 8 attackers to 1 victim. The authors concluded that lethal aggression in chimpanzees is better explained by adaptive strategies than by human disturbance alone.

This evidence is important for the present hypothesis because chimpanzee violence is not merely random rage. It is often coalitionary, opportunistic, and sensitive to power imbalance. Chimpanzee males are more likely to attack when they possess numerical superiority, when the target is isolated, and when the costs of retaliation are low. That pattern resembles controlled predatory aggression more than indiscriminate violence. It suggests that severe outgroup aggression can coexist with social calculation and selective restraint. In this sense, chimpanzees provide a comparative model for how extreme violence can be both brutal and strategically patterned.

The chimpanzee evidence also supports the possibility of group-level benefits from intergroup violence. A recent study of the Ngogo chimpanzees found that after males killed members of neighboring groups and expanded their territory, female fertility and infant survivorship increased. The study reported that lethal intergroup aggression and territorial expansion were followed by increased female fertility and improved infant survival, suggesting that successful violence against outsiders can increase access to resources and improve reproductive outcomes for the community.

This does not mean that human psychopathy evolved directly from chimpanzee-like violence. Nor does it mean that chimpanzee aggression is equivalent to human antisocial personality disorder. The comparison is narrower. In one of our closest living relatives, coalitionary outgroup violence can be severe, male-biased, strategic, fitness-enhancing, and linked to territory, rank, mating, and infant survival. That provides a comparative foundation for asking whether some ancestral human individuals with unusually low fear, low empathy, and high aggression may have gained value inside their groups by contributing to outgroup deterrence or violence.

The tolerated-danger hypothesis builds on this comparative logic. In chimpanzees, aggressive males can gain reproductive and status benefits through coalitionary aggression. In humans, a similar ecological logic may have created a niche for dangerous individuals who could be useful during intergroup conflict. Such individuals may have imposed costs within the group, but if they could restrain themselves enough to remain tolerated, their willingness to threaten, retaliate, intimidate, or harm outsiders may have increased the apparent formidability of the coalition.

The strongest version of the argument is therefore not that chimpanzees are psychopathic, or that psychopathy is simply an ape-like warrior trait. The stronger and more cautious claim is that chimpanzees show how extreme coalitionary aggression can be adaptive under some conditions. If human ancestors faced similar pressures, then psychopathic traits such as fearlessness, emotional coldness, dominance, and reduced inhibition toward violence may sometimes have been tolerated when they were directed outward. In this sense, chimpanzee evidence does not prove the tolerated-danger hypothesis, but it strengthens its evolutionary plausibility.

6. Predictive Adaptive Responses and Developmental Calibration

The tolerated-danger hypothesis also connects naturally to developmental plasticity. Psychopathic and antisocial traits are not shaped by genes alone. They may also be influenced by prenatal stress, deprivation, childhood adversity, violence, neglect, and social instability. A 2022 meta-analysis found a moderate association between childhood maltreatment and psychopathic traits across 47 studies and 12,737 participants.  A 2023 meta-analysis found that childhood maltreatment was positively associated with callous-unemotional traits in youth, including physical abuse, emotional abuse, physical neglect, and emotional neglect.

Prenatal adversity may also matter. In the Dutch Hunger Winter study, Neugebauer, Hoek, and Susser examined more than 100,000 Dutch men and found that severe maternal nutritional deficiency during the first and/or second trimester was associated with increased risk of antisocial personality disorder in early adulthood.  This finding does not prove that famine produces psychopathy. It concerns ASPD, not psychopathy narrowly. But it does support the broader idea that early developmental conditions can affect later antisocial outcomes.

Predictive adaptive response theory offers one possible evolutionary interpretation. Gluckman, Hanson, and Spencer described predictive adaptive responses as developmental responses to early cues that may improve fitness later in life if those cues accurately predict future conditions.  Nettle, Frankenhuis, and Rickard later discussed predictive adaptive responses in human life history, especially in relation to early adversity and accelerated reproductive timing. They distinguish external PAR hypotheses, in which early adversity functions as a “weather forecast” of later environmental conditions, from other adaptive explanations.

Jared E. Reser made a related argument in a 2011 blog post titled “Psychopathy is a Selfish Behavioral Strategy that may be Programmed by Ecological Adversity.” That post proposed that environmental cues may help shape selfish, manipulative, guiltless, and antisocial traits when early life predicts scarcity, hostility, and competition.

Jared E. Reser, “Psychopathy is a Selfish Behavioral Strategy that may be Programmed by Ecological Adversity,” Observed Impulse, March 18, 2011.

https://www.observedimpulse.com/2011/03/psychopathy-is-selfish-behavioral.html?m=1

The tolerated-danger hypothesis adds William Wesley Reser’s group-level dimension to this developmental idea. If early life predicts a harsh, violent, low-trust social world, then fearlessness, callousness, dominance, opportunism, and aggression may become more likely. In peaceful environments, these traits are often destructive. But in violent intergroup environments, some of the same traits might make a person useful to his coalition.

When conditions are especially bad, it may be advantageous for a group to contain someone who is difficult to frighten. A person who is low in empathy and high in aggression may be dangerous in ordinary social life, but in a world of raids, revenge, and lethal outgroup competition, he may also be the person willing to retaliate, intimidate, or cross lines that others will not cross.

This does not mean that psychopathy is simply adaptive. It means that some psychopathic traits may reflect a developmental system that becomes more likely under adversity and may have had conditional advantages in dangerous ecologies.

7. Limits, Predictions, and Conclusion

The tolerated-danger hypothesis is deliberately limited. It does not claim to explain all psychopathy or all antisocial personality disorder. It does not imply that psychopathy is generally beneficial. It does not imply that warriors are psychopaths. Most warriors, soldiers, protectors, and brave group defenders are not psychopathic. Courage, loyalty, discipline, and sacrifice are different from callousness, manipulation, and lack of remorse.

The hypothesis also does not deny pathology. Psychopathic traits can be destructive, traumatic, disabling, and socially harmful. They can arise from genetic liability, neurodevelopmental disruption, childhood adversity, social learning, and other risk factors. The present argument is only that one selection pressure may have acted on some component traits under some conditions.

The theory should apply most strongly when intergroup conflict is common, retaliation matters, reputation matters, leaders can channel dangerous subordinates, warriors or enforcers are rewarded, and the individual’s aggression is directed mostly outward. It should apply least strongly when the individual is indiscriminately violent, primarily harms insiders, lacks strategic restraint, cannot be controlled, or lives in a peaceful environment with strong legal institutions.

The tolerated-danger hypothesis makes several predictions. Groups under high external threat should show greater tolerance for callous-aggressive individuals than groups in safer conditions. Antisocial individuals should gain more status when their aggression is framed as protective, retaliatory, or outgroup-directed. Leaders should be more willing to protect dangerous subordinates when those subordinates enhance intimidation. Psychopathic traits should be more useful when paired with strategic self-control than when paired with chaotic impulsivity. Rival groups should perceive coalitions with known violent enforcers as more formidable.

There is already related evidence that warrior-like traits can be socially rewarded in high-conflict cultural contexts. Nawata’s cross-cultural study of honor culture found that honor cultures, which value male toughness and aggression, are positively associated with intergroup conflict, and that social rewards for warriors mediate this relationship.  This does not show that warriors are psychopathic, but it does show that some societies reward aggressive male formidability when conflict is frequent.

Attributions

The central hypothesis developed in this article originated with William Wesley Reser. His insight was that psychopathic and antisocial traits may have been tolerated in ancestral groups when they made the group more frightening to outsiders. Jared E. Reser contributed the predictive-adaptive-response framing. We offer this as a partial explanation, not a complete theory of psychopathy or antisocial personality disorder.