War and Human Nature

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Why did President John F. Kennedy choose a strategy of confrontation during the Cuban missile crisis even though his secretary of defense stated that the presence of missiles in Cuba made no difference? Why did large numbers of Iraqi troops surrender during the Gulf War even though they had been ordered to fight and were capable of doing so? Why did Hitler declare war on the United States knowing full well the power of that country?

War and Human Nature argues that new findings about the way humans are shaped by their inherited biology may help provide answers to such questions. This seminal work by former Defense Department official Stephen Peter Rosen contends that human evolutionary history has affected the way we process the information we use to make decisions. The result is that human choices and calculations may be very different from those predicted by standard models of rational behavior.

This notion is particularly true in the area of war and peace, Rosen contends. Human emotional arousal affects how people learn the lessons of history. For example, stress and distress influence people's views of the future, and testosterone levels play a role in human social conflict. This thought-provoking and timely work explores the mind that has emerged from the biological sciences over the last generation. In doing so, it helps shed new light on many persistent puzzles in the study of war.

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What People Are Saying

Thomas Schelling
This is a lucid, beautifully-written, informative and provocative book. It presents the modern science of choice and decision persuasively.
Thomas Schelling, University of Maryland
War and Human Nature holds the potential to open an entirely new area of insight into war. It will provide a new way of thinking about the collapse of armies, the choices and behaviors of tyrants, and the way in which differing elite selection mechanisms may wittingly or otherwise lead to individuals with differing cognitive profiles ending up in office. The use of the cognitive science literature is novel and provides insight into an area of research social scientists typically ignore.
Allan C. Stam, Dartmouth College
A thought-provoking, timely synthesis of political decision-making in light of recent progress in neurobiology, psychology and behavioral biology. Rosen explores an intriguing new formulation of biologically-motivated political science.
Michael L. Platt, Duke University
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Product Details

  • ISBN-13: 9780691130569
  • Publisher: Princeton University Press
  • Publication date: 2/5/2007
  • Edition description: ANN
  • Pages: 224
  • Product dimensions: 6.10 (w) x 9.20 (h) x 0.60 (d)

Meet the Author

Stephen Peter Rosen is a political scientist and Beton Michael Kaneb Professor of National Security and Military Affairs at Harvard University

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Read an Excerpt

War and Human Nature

By Stephen Peter Rosen

Princeton University Press

Copyright © 2004 Princeton University Press
All right reserved.

Chapter One


THE GREEK HISTORIAN Thucydides analyzed decisions about war and peace over two thousand years ago. People, he argued, were motivated by calculations of self-interest, but other factors mattered as well, factors like fear and honor, that were not quite the same as self-interest. If you asked a social scientist today what drives decisions about war, you would get the answer that people make decisions about the use of organized violence more or less in the same way that economists say people make economic decisions, that is, in a coherent, stable, and efficient manner. This book is an exploration of a more complicated understanding of human decision making. It does not reject the explanation of decision making offered by the economists, which is often a useful analytical tool. It does, however, argue that processes other than conscious calculation play a role in human decision making along with conscious calculation. Emotion, stress, and hormones such as testosterone are important players in human decision making. By understanding the role of these other cognitive mechanisms, we can often better specify the limits within which conscious, rational calculations are performed. We can also specify the ways in which human decision making may change as our bodily states change. This helps us understand why the behavior of decision makers may not bestable over time, though their behavior could be understood as rational at any one moment. These other nonconscious factors can enable rational decision making, but they do lead to decisions that we would not understand or predict if we did not take those factors into account.

The evidence for this argument comes from many sources. It includes data from college students who participate in psychological experiments. It includes data from people receiving medical treatment for mental disorders. In such cases, we must be very careful not to extrapolate directly from these findings to the behavior of leaders in the real world, who, after all, tend not to be college sophomores or brain-damaged. Yet those experiments and the data from the treatment of patients can help us understand the operations of the human mind. What happens when certain portions of the brain responsible for understanding human emotion, for example, are disabled? By answering this question, we can begin to see how the behavior of people who have not experienced brain damage may be affected by the operation of those portions of the brain. By understanding why nineteen-year-old men are different from average politicians, most noticeably with regard to their testosterone levels, we can begin to see how variations in testosterone levels can affect human decision making.

There will be a natural tendency to see the operation of these nonconscious cognitive mechanisms as producing "bad" decisions, while conscious calculations produce "good" decisions. While natural, this would be a mistake. To repeat, the nonconscious mechanisms often function in ways that make rational choice possible in complex settings. These non-conscious mechanisms exist because they played a positive role in human evolutionary history. For example, they make possible rapid decisions when there are severe limits on the amount of time available for deliberation. But they may lead to decisions that differ from what standard economic models would predict. As Daniel Kahneman and Amos Tversky demonstrated, people may overgeneralize from limited observations, impute characteristics to people on the assumption that they are representative of a group, and take more risks to avoid losses than to achieve gains. This book will explore the ways in which emotional memories may affect rational decisions, how stress and distress may lead to depression and defeat, and how testosterone may affect the impulse to punish perceived challengers. All of these phenomenan could be judged, after the fact, to be "good" or "bad." The concern of this book, however, will simply be to understand how and why the decisions were made, without judging the outcomes. This issue will be explored, in particular, in chapter 2. The argument of the book is, in its essence, reasonably simple. It includes biological issues, but it is not a biological determinist argument. Human beings have several mechanisms inside them that play a role in decision making. These multiple mechanisms exist as a result of our biological inheritance. Human beings are not exactly alike, and in a population of people there will be variations in their biological inheritance. These variations affect the mechanisms involved in making decisions about social problems, including war. These biological factors and the way in which they vary from person to person can affect the political behavior of states. But there is a social or organizational component to the argument as well. The behavior of states will depend on the nature of the social institutions that empower or weaken the influence of individuals with certain inherited ways of making decisions. The impact of the biological mechanisms analyzed in this book depends on the social settings within which people make decisions, social settings that are, in part, the result of human choice. In short, this book tries to make the case that there is a biological argument that Thucydides was right, that fear and honor play a role in human politics along with calculations of interest, but also that the other issues he analyzed, such as the nature of the political systems present in the ancient Greek world, matter as well.

Making that case takes some effort. This book uses the current scientific understanding of human nature, along with an understanding of social institutions, to explain human cognition as it is relevant to the issues of war and peace. Since the terms "human nature" and "cognition" are used in a variety of ways, they should be defined. In this book, cognition will mean the way in which information is selected, stored, recalled, and used, consciously or unconsciously, for decision making. Human nature will refer to the aspects of human cognition that are affected by biological inheritance, as those inherited factors are shaped by human interaction with the environment. This book argues that the two are linked. There are inherited parts of the brain and the endocrine system that function along with the parts of the brain that do perform conscious calculations. They affect rational calculation, and can facilitate rational calculation, but they can also push us toward decisions that are different from the ones we would make on the basis of conscious calculation alone. Indeed, it will be shown that conscious calculations by themselves may be insufficient to lead people to a decision, and other factors are important because they make possible rational choices in complex environments. Yet those other factors do complicate our internal decision-making processes. It is because of the coexistence of these other mechanisms, along with conscious calculation, that Thomas Schelling was correct when he stated that human behavior must be understood as the interaction between at least two conflicting selves within each person.

The rest of this book is an elaboration of these ideas.

It helps to begin by looking at human nature and cognition in general, or the biologically affected ways of processing information that most people have in common. The biological sciences now give us a more detailed picture of how the human brain operates. While we do not have anything close to a complete understanding of human cognition, important elements of it are now better understood. For example, we know that the neocortex, the part of the human brain that is proportionally much larger than that found in any other animal, and which is responsible for conscious thought, does not treat all data equally. It is more sensitive to some kinds of data derived from sensory perceptions. In ways that can be reliably and empirically demonstrated, and for which evolutionary psychology provides plausible explanations, the neocortex is provided with, or preferentially selects, certain kinds of data. Certain memories, notably those formed at times of emotional arousal, and certain kinds of current data, notably the data associated with the expression of emotion in faces and voices, are more salient when we consciously and unconsciously consider what we should do. This selection of data is not done consciously, but it does shape conscious thought. The data selected for use by the human brain is not necessarily the selection of data that would lead to the choices that an economist would regard as optimal. For example, new information may not be given as much weight as an economist would think it should, if the new information conflicts with memories that have emotional associations.

The neocortex then processes that data within certain parameters, or constraints. Those constraints are not consciously chosen and may or may not be optimal in ways that economists would recognize. For example, rational decision making involves thinking about the future consequences of current actions. The act of considering the consequences of our actions before making a decision is a function performed by the neo-cortex. But how far into the future should we think? Should I care a great deal about the consequences of my actions ten years from now, or should I let the future take care of itself? In more technical language, what is the nature of our time horizons? How much do we discount costs and benefits that arrive sometime after our actions? These time horizons are not something that we always choose consciously. Our time horizons can be affected by human nature, as well as conscious decisions. Both human nature acting unconsciously and conscious calculation can affect what we consciously decide to do. By better understanding the biology of human cognition, we can better specify how people make decisions rationally, by specifying the biological mechanisms that supply the data needed for decision making and specifying the parameters, such as time horizons, within which decisions are rationally made.

To be more specific, there are parts of the human brain involved in decision making that are distinct from the neocortex. These are sometimes referred to as the evolutionary older parts of the brain, because they are also found in nonhuman animals. For example, the amygdala and the hippocampus, working together with portions of the endocrine system, react to information in ways that shape the decision making done by the neocortex. But there are also parts of the brain that perform an independent decision-making role, separately from the neocortex. When I am hungry and I see a doughnut, I may eat it, not because I consciously calculate that I should, but because something other than conscious calculations has decided that I will eat it. This form of decision making is not the same as conscious decision making and can affect social interactions. If I am challenged by my subordinate, I may lash out and punish that subordinate "without thinking," and in ways that may not be what I would, in calmer moments, refer to as being in my best interests. If I am subjected to prolonged stimulation from the environment that I cannot control, my stress response and endocrine system will respond in a way that will eventually create a state of mind equivalent to depression. While depressed, I will make decisions that will be different from the decisions I will make when not depressed. At any particular moment in time, my biological state will affect my decision making. If you are aware of my immediate biological state, my decisions will be comprehensible, but my behavior will not be stable over time. My decisions may not be rational in the sense that they are not stable: the same information will lead to different decisions at different times.

In short, the human brain is not easily reducible to a unified, rational calculating machine. It has parts that support conscious calculation, parts that shape conscious calculation, but also parts that can run counter to conscious calculation. Because these characteristics of the human brain are to some extent determined by our heredity, they are resistant to changes that are motivated by conscious choice. I cannot decide, for example, not to be depressed. I can try not to be affected by traumatic memories, but I may not succeed. We are not unitary rational actors, though we can try, sometimes successfully, to make ourselves behave as if we were. Because certain decision-making mechanisms can be dominant at some times but not at others, we do not always make decisions the same way. This means that we may not display what is at the core of the economic model of human decision making, that is, consistent and ordered preferences that are stable over time. The nonconscious elements of decision making can and do change over time in ways that we cannot consciously control, and this can lead to inconsistencies in our behavior. For a variety of reasons, at some times we will behave as if we want A, and at others, we will behave as if we want not-A. Human beings have been known to want to have their cake and eat it too, or, in the case of international politics, to want peace, for example, but also want to lash out at challengers who hurt us.

Though there is much about human cognition that is shared by all people, human beings are not identical. Natural selection can operate only on a population that has variations, and human beings display variations in their inherited decision-making mechanisms. As a result, it is important to understand the way different people process information differently, because of their differing hereditary factors. With regard to many cognitive factors, people are not all the same. All people have some measure of intelligence, for example, but intelligence varies across individuals in ways that are affected by genetic inheritance, though we can argue about how big a factor genetic inheritance is compared with other factors. Biological variations in cognition go beyond intelligence. A teenage boy reacts to a challenge from a peer in a way that is different from the reaction of a middle-aged woman. More subtle but important differences exist among mature adults, with regard to their sensitivity to status challenges, time horizons, or susceptibility to depression. The ability to specify the ways in which different people make decisions differently enables us to deal with one of the longstanding objections to the use of the results of experimental psychology to explain real-world political behavior. The objection is obvious: people who participate in lab experiments may not be like the people who are the heads of governments. In fact, they are very likely to be different. But we can now begin to understand this heterogeneity, and so distinguish and identify people with different cognitive profiles.

Up to this point, the emphasis has been on individuals and individual decision making, but individual human nature and the variations among individuals in their natures cannot, by themselves, explain the behavior of groups of humans. There may well be differences in individual cognitive profiles, but political decisions are seldom made and executed by single individuals. It may be the case that human nature affects human cognition, and that individuals are different from each other, but how do we go from that to an explanation of the behavior of governments? The argument of this book is that different social settings or institutions do not always randomly select people and give them political power. Instead, they may preferentially select people with particular cognitive profiles for positions of responsibility and then situate them in social environments that reinforce the decision-making tendencies that they have as individuals. To give one example discussed at length in chapter 5, turbulent political environments full of near-term dangers make it easier for people with near-term time horizons to rise to political power, and for them to gain tyrannical power. Once in a position of absolute power, such individuals will exist in a social environment in which their individuals. To give one example discussed at length in chapter 5, turbulent political environments full of near-term dangers make it easier for people with near-term time horizons to rise to political power, and for them to gain tyrannical power. Once in a position of absolute power, such individuals will exist in a social environment in which their individual cognitive profiles will be of considerable political importance, and their individual predisposition to act in ways affected by near-term calculations will be reinforced by the social setting in which they exist. A different political system will select and empower a different kind of person. The institutions associated with oligarchic politics may select for people sensitive to social status and put those people together in an environment that tends to focus and magnify their status challenges to each other, reinforcing their predisposition to engage in challenge-response types of status politics. In other group settings, the stress-induced depression experienced by one individual will create behavior that others can observe, and which can trigger fear and depression in them. On the other hand, one can also specify social institutions that will tend to dampen or neutralize the effects of individual cognitive predispositions before they are translated into group behavior. Checks and balances are meant, among other things, to prevent individual tendencies to "act in the heat of the moment" from becoming actual. So the variations in human nature relevant to cognition will be important only when social conditions reinforce them.


Excerpted from War and Human Nature by Stephen Peter Rosen Copyright © 2004 by Princeton University Press. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
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Table of Contents

Acknowledgments vii
Chapter One: Introduction 1
Chapter Two: Emotions, Memory, and Decision Making 27
Chapter Three: Status, Testosterone, and Dominance 71
Chapter Four: Stress, Distress, and War Termination 99
Chapter Five: Of Time, Testosterone, and Tyrants 135
Chapter Six: Where Do We Go from Here? 179
Notes 185
Index 205

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"This is a lucid, beautifully-written, informative and provocative book. It presents the modern science of choice and decision persuasively."—Thomas Schelling, University of Maryland

"War and Human Nature holds the potential to open an entirely new area of insight into war. It will provide a new way of thinking about the collapse of armies, the choices and behaviors of tyrants, and the way in which differing elite selection mechanisms may wittingly or otherwise lead to individuals with differing cognitive profiles ending up in office. The use of the cognitive science literature is novel and provides insight into an area of research social scientists typically ignore."—Allan C. Stam, Dartmouth College

"A thought-provoking, timely synthesis of political decision-making in light of recent progress in neurobiology, psychology and behavioral biology. Rosen explores an intriguing new formulation of biologically-motivated political science."—Michael L. Platt, Duke University

Read More Show Less

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