The Psychology of Strategy & Strategy, Evolution, and War

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The Psychology of Strategy: Exploring Rationality in the Vietnam War. Kenneth Payne. Oxford, UK: Oxford University Press, 2016.

Strategy, Evolution, and War: From Apes to Artificial Intelligence. Kenneth Payne. Washington, D.C.: Georgetown University Press, 2018.

A new science of human behavior has emerged over the past two decades. This new science has linked together the research of neuroscientists, cognitive and evolutionary anthropologists, decision theorists, social and cross cultural psychologists, cognitive scientists, ethnologists, linguists, endocrinologists, and behavioral economists into a cohesive body of research on why humans do what they do. Research in this field rests on two propositions about the human mind. The first, that the mind is embodied; the second, that it is evolved.

When behavioral scientists say the mind is embodied, they mean the mind is a biological thing and the study of decision making cannot be divorced from the architecture of the biological machinery that makes the decisions. Their research suggests most of the mind’s machinery works under the hood, below the level of conscious awareness. Researchers have their  favorite object of study: for some it is hormones and emotions, for others it is specialized cognitive modules evolved in the deep human past to solve problems faced by our hominid ancestors, and for yet others it is culturally created cognitive gadgets impressed into the biological structure of brains at an early age by the societies in which we grew up.[1] When behavioral scientists say these attributes of human psychology are evolved, they mean only that, as a biological thing, the human mind was created by the same evolutionary process that crafted the function and form of every other living thing. “Nothing in biology makes sense except in the light of evolution” (as one famous biologist declared several decades ago), and this is as true for the study of the human mind as it is for the study of bacteria or butterflies.[2]

What does this have to do with war or strategy? Everything, answers Kenneth Payne, professor in the War Studies department at King’s College London. In the last three years, Payne has published two books on the subject. The first, The Psychology of Strategy: Exploring Rationality in the Vietnam War, uses the Vietnam War as its central case study; the second, Strategy, Evolution, and War: From Apes to Artificial Intelligence, extends the themes of the first book deep into the wars of humanity’s evolutionary past and forward into the less human wars of its future. The reasoning behind Payne’s books is simple: strategic decision making is human decision making. Like all aspects of human behavior, powerful insights about the nature of strategy can be gained by viewing it through the lens of behavioral science.[3]

Payne’s vision stretches far into the human past––indeed, past the human past. By defining strategy as “the purposeful use of violence for political ends,” Payne creates a definition of strategic action that can apply to non-human species such as chimpanzees or our hominid ancestors.[4] Chimpanzees use purposeful violence against other chimpanzees to maintain preferential access to resources and mates, and Payne sees similarities between the tactics of chimpanzee violence and that found in hunter-gatherer and foraging societies. The “essence of strategy for early man [and other primates] was to concentrate force in time and space against weaker enemies.”[5]

Like other animals, humans prefer to fight with an asymmetric advantage. In warfare, the simplest asymmetric advantage is numbers. Surprise is one way to ensure your side gets to fight at the moment of maximum numerical advantage, but the easiest way to ensure you have that advantage is simply to have a larger population of fighters to draw from. Payne suggests this reality was a driving force behind the evolution of the human brain. In primates, brain size correlates with social group size. Larger, more complex brains are more capable of monitoring and navigating larger social networks. In the Pleistocene, both hominid brain size and group size ballooned. Many evolutionary anthropologists and psychologists have noted this relationship before, but Payne argues that simply drawing the correlation between the two is not enough. What is needed is “an endogenous account of the evolutionary rationale for these larger ultrasocial groups. Where is the big advantage to be gained from intense cooperation and larger groups? My answer is the threat of war.”[6]


In making this argument, Payne side-steps many of the most contentious anthropological debates about the origins of war. Humans are not the only animals to engage in violent group conflict. We are not even the group that engages in it on the largest scale; that honor goes to ants, who are capable of battles with more than 30 million casualties! What makes human conflict unique is the genetic distance between comrades-in-arms. Other warring primate bands are very small and thus closely related, while eusocial insects like ants are often the progeny of a single queen. Humans, in contrast, fight and die for the sake of individuals who share very little of their genes. Any account of human evolution that emphasizes war must find a way to explain this evolutionary paradox.

The worst enemies of ants are often other ants in Diamond Creek, Victoria, Australia. (Alex Wild/iO9)


The archeological record presents another challenge to war-driven accounts of human evolution. Archaeological evidence for war is plentiful in the Mesolithic Period, but much harder to find in the Pleistocene—the era when humans first evolved. Nor is war a universal in the contemporary anthropological record. Anthropologist Douglas Fry composed a list of 70 different societies that do not have violent, group-level conflict; other cross-cultural examinations of hundreds of small scale societies have estimated that, depending on the exact data set, somewhere between 10-15% of foraging societies did not have any experience with war at the point of anthropological contact.[7] Any argument that warfare was a major source of evolutionary selection pressure on the evolution of human psychology needs to address this.

Payne mostly ignores these issues. Instead, he focuses on unique elements of human psychology that make humans especially well adapted for strategic competition. Ultrasociality is one of these elements. Theory of mind—the label psychologists give our ability to attribute mental states like thoughts, feelings, or intentions to other people—is another key skill that is unique to humanity and fundamental to strategic theory. With theory of mind comes both the ability to intuit the intentions of an enemy and the capacity to deceive them. Surprise, shock, and deception are some ways to overcome the hard laws of numbers; if war was a strong source of selection pressure in early hominid history, the capacity to use these cognitive skills in conflict would give individuals with it a distinct evolutionary advantage.

Readers’ tolerance for Payne’s evolutionary theorizing will vary. Yet even those positively allergic to evolutionary psychology will have difficulty dismissing Payne’s larger framework. Be it the product of deeply ingrained evolutionary biases, or the product of more recent cultural evolution, human psychology is the tool through which all decisions of war and peace must be made. In both Evolution, Strategy, and War and The Psychology of Strategy, Payne isolates several aspects of human psychology that are especially relevant to strategic decision making. Payne divides these aspects into three broader themes: unconscious biases that affect strategic decision making, interaction between emotions and strategic action, and the critical role that social esteem plays in the psychology of strategy.


Payne’s list of biases will be familiar to anyone familiar with behavioral economics. This includes an optimism bias that leads humans to overestimate the chance of success in risky endeavors, the illusion of control effect, which leads humans to assume they have more control over systems they interact with than they actually do, and the fundamental attribution error, which leads humans to under-emphasize situational incentives and overemphasize personality when analyzing the behavior of other humans. Payne also details how various emotions might affect human decision making. For example, there is strong evidence humans become more certain in our beliefs and in our decisions when angry; the strategic calculations of an angry decision maker will be fundamentally different from a sorrowful one. One of the more intriguing ideas in Payne’s catalog of biases is his interpretation of Clausewitz’s dictum that the defense is stronger than the offense. This is true, Payne argues, because humans are loss averse. We are willing to suffer more to keep what we have now than we are to earn something new. If humans think about territory or international prestige this way, then commanders will be bolder when trying to recover lost ground, and their soldiers will be more determined in defense than on the attack.[8]

Presidents Johnson and Nixon at the latter’s inauguration. (Nixon Presidential Library)

The most interesting part of this discussion is Payne’s analysis of honor and esteem. Humans are social animals. The need for the esteem of other humans seems deeply ingrained in human psychology, and statesmen and strategists are not immune to this. In the Psychology of Strategy Payne provides scores of examples of strategic decisions made by Lyndon Johnson, Richard Nixon, and other officials that were made more to bolster the social esteem of the decision maker than to defeat the enemy. For Johnson and his officials, esteem and reputation were often explicitly described as the most important objective in the war—one administration official estimated in a memo that 70% of the reason the U.S. was escalating in Vietnam was to avoid humiliation; the other 30% was divided between the need to keep Vietnam out of Chinese hands and to help the people of South Vietnam live a freer life.[9] Memos like these are the product of another human psychological quirk: the natural tendency to conflate the honor given to the groups with which we identify with our own sense of esteem.

The impulse to treat an insult directed at the groups to which we belong as an insult to ourselves is natural, but odd. For example, when is the last time you got angry because someone disparaged the weather under which you live? Also odd is the flexibility with which our group identities change. At any one time a human will identify with many different groups, and the importance of each group to the identity of any given human will change with the situation. The groups with which humans feel most solidarity tend to be those under attack or given the most public esteem. This has important implications for strategists: “Honor becomes an essential part of our interest in war, because it is integral to the preservation of the group itself, as a locus of shared meaning. There is no interest without identity, and the defence of that identity demands honor.”[10]

The overuse of the word human in the last two paragraphs is intentional. Esteem, emotion, and cognitive biases are human phenomena. If wars were fought by non-humans they would be fought differently. This is exactly what Payne imagines for the future of war. Artificial intelligence will be a revolution in warfare, Payne claims, because for the first time in man’s evolutionary history, strategy will be freed from the limits of human psychology: “Rather than creating a danger from AI acting strategically against humans, the main effects of AI are likely to be felt from AI acting in our interests.”[11]

How might artificial intelligence affect the risk and conduct of war? (Pinterest)

While there is much to praise in these two books, I suspect both academics and practitioners will be frustrated by their approach. Payne does not offer hypotheses or models that might put his ideas on surer scientific footing. He suggests rationalist models of international relations are fundamentally flawed, but does not outline what might replace them. He argues the results found in psychology labs are inseparably linked to the decisions of war, but does not provide a framework that might help strategists use these results to refine their craft. Payne’s approach is suggestive. He synthesizes a vast psychological literature and then suggests where this literature might intersect with the study and practice of war. But Payne goes no further than this.

To his credit, Payne is fully aware of these limitations. In both books he laments the “difficulties [that] stymie our ability to robustly establish the way in which psychology shapes strategy.”[12] This humility is refreshing, though it makes it difficult to know exactly what readers are supposed to do with his work.

I submit the value of Payne’s research is less in what it proves than in the avenues for research it opens. Payne’s books are full of small asides that—if properly investigated—could become their own books. Here are three potentially fruitful research questions that occurred to me as I read through these two books.

In one of the more intriguing passages of The Psychology of Strategy, Payne suggests:

Insofar as honour is the goal for states embroiled in war, the fighting itself can tend to the ritualized and stylized, rather than the conception of ‘total’ war offered in parts of Clausewitz’ writing... Display and attention to rules become integral parts of strategy. Societies have more latitude to fight according to their cultural precepts, rather than to adjust them in pursuit of efficiency. They can acquire armed forces and develop ways of fighting that seem in tension with strategic conditions facing them.[13]


The contrast Payne sees between wars of honor and more total conceptions of war has striking parallels with patterns military historians have described independently. J.E. Lenden, Pier Mackay, and Stephen Morillo have described this exact contrast in their analysis of different wars between the polis of ancient Greece, the kings of medieval Europe, and the European empires of the 18th century.[14] But if stylized wars of honor are a real phenomena, what determines when armies and states fight them instead of wars dominated by fear or interest? Why were the first ten years of the duel between Athens and Sparta defined by Greek honor norms, when these same norms had so little power to shape behavior in the later years of the conflict? What, in short, can the study of human psychology teach us about the durability of norms of war?

An Imperial Battle Painting from the Set of Seventeen Paintings Commemorating the Campaign Victories in the Northwestern Region, Qing Dynasty, Guangxu Period. (Pinterest)

Cross-cultural psychology is a burgeoning subfield of psychology. Psychologists, and more than a few anthropologists, have discovered human beings from different cultures often have different cognitive profiles, including the psychological biases they are victim to.[15] As anthropologist-cum-psychologist Joseph Henrich noted, “Many researchers want to study those psychological processes that make us uniquely human. The problem is, at this point, there has been so little systematic comparative experimental research across diverse populations that we currently lack any reliable way to know when we are tapping innate psychological processes, or the products of centuries of cultural evolution.”[16] This critique is relevant to almost all the evidence Payne presents. Indeed, Henrich and a team of cross-cultural psychologists suggest in a forthcoming research article that optimism bias, one of the biases Payne discusses at length, is not similarly manifested in East Asian and Western populations.[17] One must ask: Is Payne’s psychology of strategy really just the psychology of Western strategy?

This may cause some to question the utility of Payne’s entire work. In contrast, I see it as an opportunity to extend Payne’s general research program. For the last three decades scholars have tried to create viable theories of strategic culture that might explain patterns in the strategic decision making across cultures. While this literature has been plagued with many problems, one of its key failings is that most of it fails to explain how strategic culture is transmitted from one generation to the next. This literature also fails to describe the mechanism by which culture actually changes decision making.

By refocusing these debates on cognitive differences of decisions makers, progress may be possible. Psychology might be the missing key to the puzzle. It is easy to imagine a robust line of research that attempts to ferret out which elements of human psychology are most relevant to strategy, tests through laboratory and field studies which of these elements are cognitive gadgets unique to certain cultures and which are genetically ingrained human universals, and then uses these results as a lens through which to test strategic history.

Another new and fascinating line of research in the behavioral sciences is the study of what researchers have dubbed folk sociology. As cognitive scientist Pascal Boyer has described, “In all human societies, people have some notion of what social groups are, how they are formed, what political power consists of.” Linguistically, this folk sociology is expressed through metaphors. For example, we talk about groups of people as if they were unitary agents (“the American administration is angry with China”), and we talk about political power as if it were a physical force (“the Republicans bowed under popular pressure” or “the Conservatives crushed Labour”) even though neither of these things is true. Despite its inaccuracy, this way of talking is natural and appears in multiple languages. Boyer and his compatriots suggest this is because the cognitive resources we use to understand these concepts originally evolved for other purposes—in this case, understanding the behavior of actual unitary agents and intuitive models of physics, respectively. They have traced many ways in which this folk sociology has a powerful effect on the way humans understand and interact with political institutions and economic markets.[18]

Is there such a thing as folk strategic theory? If Payne is correct, and warfare was a source of selection pressure throughout the evolution of humanity, then it is likely we have developed cognitive modules that channel or understanding of violence, strategy, and war into certain metaphors and mental conceptions.

These are but some of the questions raised by Payne’s work. Neither of these books are without their flaws, but through writing them Payne has laid a worthy foundation for years of research to come.

T. Greer is a writer and analyst currently based out of Taipei. His research focuses on the evolution of East Asian strategic thought from the time of Sunzi to today. He blogs at The Scholar’s Stage.

This article appeared originally at The Strategy Bridge.


[1] For recent reviews of this research, see Robert Sapolsky, Behave: The Biology of Humans at Our Best and Worst (New York: Penguin, 2017); Cecilia Heyes, Cognitive Gadgets: The Cultural Evolution of Thinking (Cambridge: Harvard University Press, 2018); Pascal Boyer, Minds Make Societies: How Cognition Explains the World Humans Create (New Haven, Yale University Press, 2018).

[2] Dobzhansky, Theodosius (March 1973), "Nothing in Biology Makes Sense Except in the Light of Evolution", American Biology Teacher, 35 (3): 125–129.

[3] Incidentally, this vision of strategic theory would please the founder of the discipline. Clausewitz was obsessed with the psychological aspects of his art. A quick search through my kindle edition of the Peter Paret translation On War reveals 159 references to ‘moral’ (a word Clausewitz used similarly to our use of ‘psychological’ today), 78 to the word ‘psychological,’ and 59 to “emotions.” Included in these discussions are long discussions of daring, instinct, memory, courage, cowardice, anger, determination, uncertainty and the difficulties human minds have grasping the complexities of war—staple topics of the new wave of behavioral science.

[4] Payne, Evolution, 1.

[5] Ibid., 3

[6] Ibid, 5

[7] For a concise review of this literature and its attendant controversies, see Sarah Matthew and M. Zefferman "An Evolutionary Theory of Large-scale Human Warfare: Group-structured Cultural Selection," Evolutionary Anthropology: Issues, News and Reviews, vol 24, iss. 2 (2015): 50-61. One potential answer Payne might have to this question concerns the survival benefits that come from being in a larger group: "not only does lethality rise disproportionately with scale; casualties fall in similarly nonlinear fashion. It's safer to be in a swarm of fighters finishing off an isolated combatant" (Evolution, 69). This does not answer, however, the problem of free-riding. An evolutionary explanation for group violence must account for why there are a comparatively low number of attempts to 'defect' from danger in battle when such behavior seems like the optimal thing to do, from a genetic perspective.

[8] Payne’s notion of loss aversion is not unique. For example, see Daniel Kahneman and Amos Tversky, “Choices, values, and frames,” American Psychologist, 39 (4), 341-350.

[9] Payne, Psychology, 104.

[10] Ibid., 100.

[11] Payne, Evolution, 2

[12] Ibid, 159.

[13] Payne, Psychology, 23.

[14] J.E. Linden, Song of Wrath: The Peloponnesian War Begins (New York: Basic Books, 2010); Piers Mackay, The War for America, 1775-1783 (Bison Books, 1993); Stephen Morillo, “A General Typology of Transcultural Wars: The Early Middle Ages and Beyond,” in Hans-Henning Kortüm, ed., Transcultural Wars from the Middle Ages to the 21st Century (Berlin: Akademie Verlag, 2006), 29-43.

[15] For a (now slightly outdated!) review, see Richard Nisbett, The Geography of Thought: How Asians and Westerners Think Differently…and Why (New York: Free Press; 2003).

[16] Joseph Henrich, “Culture and the Science of Behavior,” Current Opinion in Behavioral Sciences, vol 3 (2015), 89.

[17] Muthukrishna, et. al., “Overconfidence is Universal? Elicitation of Genuine Overconfidence (Ego) Method Reveals Systematic Differences Across Domain, Task Knowledge, and Incentives in Four Populations.” PLoS One (forthcoming).

[18] Boyer, Minds Make Societies, kindle locations 3556-3557.

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