In this roundtable, four of international relations’ finest scholars evaluate Marcus Holmes’s Face-to-Face Diplomacy: Social Neuroscience and International Relations, a bold effort to bring research on brains to bear on questions of high-stakes summitry. While international relations scholars identify uncertainty, particularly the problem of judging the intentions of other states, as a central and essentially unsolvable problematique, Holmes disagrees. Research shows that our neural architecture is set up to simulate the mental states of others when we meet face-to-face, something that we do unconsciously and intuitively. Holmes draws the conclusions of this central claim for the study of diplomacy, a process that is finally receiving the theoretical and empirical attention it deserves. All of the reviewers agree that this interdisciplinary-inspired book offers a new look at an old question of international relations. Andrew Ross writes, “Holmes leverages this account of intersubjectivity to dismantle an entire edifice of theorizing built on the problem of other minds, inaccessible intentions, and the distrust that ensues therein. The result is a potential game-changer not only for the study of diplomacy but also for efforts to understand other forms of social interaction in international affairs.” They also praise him for his adroit use of history. The book explores the power of face-to-face diplomacy in case studies that include the interactions of presidents Ronald Reagan and George H.W. Bush with Soviet premier Mikhail Gorbachev, the Munich summit between British prime minister Neville Chamberlain and Nazi Germany’s Adolf Hitler, and the Camp David summit in which President Jimmy Carter brokered peace between Egypt and Israel.

Editors: Thomas Maddux and Diane Labrosse

Web/Production Editor: George Fujii

Marcus Holmes. Face-to-Face Diplomacy: Social Neuroscience and International Relations. New York: Cambridge University Press, 2018. ISBN: 9781108417075 (hardback, $99.99).

Published on 1 July 2019

Contents

© Copyright 2019 The Authors



Introduction by Brian Rathbun, University of Southern California

In this roundtable, four of international relations’ finest scholars evaluate Marcus Holmes’s Face-to-Face Diplomacy: Social Neuroscience and International Relations, a bold effort to bring research on brains to bear on questions of high-stakes summitry. While international relations scholars identify uncertainty, particularly the problem of judging the intentions of other states, as a central and essentially unsolvable problematique, Holmes disagrees. Research shows that our neural architecture is set up to simulate the mental states of others when we meet face-to-face, something that we do unconsciously and intuitively. Holmes draws the conclusions of this central claim for the study of diplomacy, a process that is finally receiving the theoretical and empirical attention it deserves. All of the reviewers agree that this interdisciplinary-inspired book offers a new look at an old question of international relations. Andrew Ross writes, “Holmes leverages this account of intersubjectivity to dismantle an entire edifice of theorizing built on the problem of other minds, inaccessible intentions, and the distrust that ensues therein. The result is a potential game-changer not only for the study of diplomacy but also for efforts to understand other forms of social interaction in international affairs.” They also praise him for his adroit use of history. The book explores the power of face-to-face diplomacy in case studies that include the interactions of presidents Ronald Reagan and George H.W. Bush with Soviet premier Mikhail Gorbachev, the Munich summit between British prime minister Neville Chamberlain and Nazi Germany’s Adolf Hitler, and the Camp David summit in which President Jimmy Carter brokered peace between Egypt and Israel.

There is also overlap in a number of critiques. The first centers on the degree to which the author can rely on an unobservable mechanism to make an argument about international politics. Holmes draws heavily on research into mirror neurons that facilitate the simulation of others’ actions. Yet the very existence of mirror neurons and their role is contested, as Rose McDermott and Ross note, and research has centered on our ability to simulate the motor actions of others and infer their intentions, a fundamentally different application than that which is used in this book. The concept of mirror neurons emerged from studies of primates. As Joshua Kertzer wryly notes, “the book has noticeably more macaques in it than does the modal book on diplomatic summitry.” Macaques, however, do not engage in high stakes diplomacy about the number of intercontinental ballistic missiles. Although the role of intuitive simulation is undoubtedly important, the way it takes place among a much more social species is likely fundamentally different. Recognizing all of the problems that mirror neurons raise, and the fact that we cannot even see them, Yarhi-Milo asks whether we need them at all in order to make the case for face-to-face diplomacy. This is a somewhat unsurprising question considering that her own book, Knowing Thy Adversary, attributes its power to a much simpler fact: what we directly experience is much more vivid and therefore salient in our minds.[1]

Second, the reviewers also raise questions about the accuracy of this simulation process. Is it the case that mirror neurons really ‘solve’ the problem of other minds, or make us feel like we have solved it? In other words, is our intuition better than our deliberation? Kertzer points out that our automatic processing, sometimes called ‘System I,’ is known for its susceptibility to bias. Assuming that this is where mirror neurons do their work (and again, who knows?), it suggests that our intuition is not a better detector of deception. Yet Holmes seems to infer the opposite. It is only, for instance, Chamberlain’s narcissism that got in the way of the signals that his mirroring system was sending him, the implication being that mirror neurons are generally successful. If they are, this would help answer the question raised above: how much further does neuroscience get us in understanding face-to-face diplomacy than other equally plausible mechanisms. If it generally help us get to the bottom of things, this would be fundamentally different than Keren Yarhi-Milo’s ‘vividness’ argument.

Third, even if mirror neurons steer us right, how can we judge their impact vis-à-vis all of the other cognitive, social, and political factors that leaders literally bring to the table in their interactions with one another? All human beings, even heads of state, are affected by their personal experiences, giving them a unique set of analogies, worldviews, and emotional vulnerabilities. A focus on mirror neurons directs us naturally to a set of individual case studies. Yet, paradoxically, in single case studies the number of potential other causal factors explodes in a way that is less true of larger-N studies because idiosyncratic factors really might matter. In a larger set of cases, we could dismiss President Harry Truman’s strong association of Soviet leader Joseph Stalin with his old Democrat party boss from Missouri, Tom Pendergast, a point that McDermott raises, because any such effect would average out across the cases. This is not true for the interpersonal interactions in which Holmes is interested.

In any case, Holmes has written a book that we will want to talk about, which is perhaps the highest compliment one can pay an international relations scholar. Interdisciplinary scholars looking for new lenses, diplomacy scholars trying to figure out just what it is that diplomacy does, or signaling theorists trying to determine how we make judgments about what we believe about others will all find something that interests them.

Participants:

Marcus Holmes is Associate Professor of Government at William & Mary. His work focuses on diplomacy and political psychology. He is co-director of William & Mary’s Social Science Research Methods Center and directs an undergraduate research lab, Political Psychology and International Relations. He received his Ph.D. from The Ohio State University and is currently working on a joint-project with Nicholas J. Wheeler on the concept of social bonding in diplomacy.

Brian Rathbun is Professor of International Relations at the University of Southern California. He is the author of Reasoning of State (Cambridge University Press, 2019), Diplomacy’s Value (Cornell University Press, 2014), Trust in International Cooperation (Cambridge University Press, 2012) and Partisan Interventions (Cornell University Press, 2004) as well as articles in International Organization, International Security, World Politics, and International Studies Quarterly, among others. He is currently writing a book on the role of morality in international affairs from a non-normative point of view.

Joshua D. Kertzer is the Paul Sack Associate Professor of Political Economy at Harvard University. His research specializes in the intersection of international security, political psychology, foreign policy, and public opinion. He is the author of Resolve in International Politics (Princeton University Press, 2016), along with articles appearing in a variety of academic journals, including the American Journal of Political Science, Annual Review of Political Science, British Journal of Political Science, Conflict Management and Peace Science, International Organization, International Studies Quarterly, Journal of Conflict Resolution, Journal of Politics, and World Politics.

Rose McDermott is the David and Mariana Fisher University Professor of International Relations at Brown University and a Fellow in the American Academy of Arts and Sciences. She received her Ph.D. (Political Science) and M.A. (Experimental Social Psychology) from Stanford University and has taught at Cornell and UCSB. She has held fellowships at the Radcliffe Institute for Advanced Study, the Olin Institute for Strategic Studies and the Women and Public Policy Program, all at Harvard University. She has been a fellow at the Stanford Center for Advanced Studies in the Behavioral Sciences twice. She is the author of five books, a co-editor of two additional volumes, and author of over two hundred academic articles across a wide variety of disciplines encompassing topics such as experimentation, emotion and decision making, and the biological and genetic bases of political behavior.

Andrew A. G. Ross holds a Ph.D. from The Johns Hopkins University and is Associate Professor of Political Science at Ohio University. He is the author of: Mixed Emotions: Beyond Fear and Hatred in International Conflict (University of Chicago Press, 2014), as well as articles in the European Journal of International Relations, International Organization, International Theory, and Millennium. Ross is currently working on a project about digital technologies and practices in global politics.

Keren Yarhi-Milo is an Associate Professor of Politics and International Affairs at Princeton University. She is the author of Knowing The Adversary: Leaders, Intelligence and Assessment of Intentions in International Relations (Princeton University Press, 2014) and the newly released book “Who Fights for Reputation? The Psychology of Leaders in International Conflict” is forthcoming (Princeton University Press, 2018).

Review by Joshua D. Kertzer, Harvard University

God may have given physics the easy problems, but there is at least one advantage International Relations (IR) scholars have over our brethren in the natural sciences: we can ask our subjects of inquiry whether they think we’re on the right track.[2] Many of the most fruitful areas of research in IR in the past several decades have thus centered on questions characterized by disagreement between conventional scholarly wisdom, and the confidently held beliefs of policy-makers. For example, if leaders and diplomacy don’t matter, why do decision-makers generally presume that they do?[3]

It is in this tradition that Marcus Holmes’s thoughtful and provocative new book is situated. From President Ronald Reagan and General Secretary Mikhail Gorbachev building rapport through a series of meetings in the twilight of the Cold War, to President George W. Bush looking Russian President Vladimir Putin in the eye and claiming to “get a sense of his soul,” policymakers routinely speak of the importance of meeting face-to-face. Despite rapid advances in technology, the last three American secretaries of state prior to Rex Tillerson each flew close to a million miles over the course of their tenure, presumably out of the belief that sitting down in person is more effective than picking up the phone.[4] Yet IR scholars have traditionally either been skeptical of personal diplomacy, or unable to convincingly theoretically explain why it should be more effective than other forms of negotiation.[5]

Holmes argues that face-to-face diplomacy is effective because it solves what IR scholars call the ‘problem of intentions,’ and what philosophers call the ‘problem of other minds.’ Whereas many IR scholars often treat uncertainty about others’ intentions as the default—if not defining—condition of international politics,[6] Holmes builds on research on mirror neurons in social neuroscience and the philosophy of mind to argue that our cognitive architecture equips us with the ability to simulate others’ mental states, and that this ability is heightened when individuals engage in face-to-face interaction. Unlike theories in which the presence of private information leads actors to attempt to draw inferences about others’ intentions by looking for costly signals, Holmes posits that actors subconsciously and automatically engage in mental mimicry in face-to-face situations, detecting deception through nonverbal cues.

The book is therefore not merely a defense of decision-makers’ intuitions, but a defense of intuition itself, part of a growing body of research in both psychology and IR that is interested in moving beyond reflexive logics of action by incorporating practice and dual-process models of cognition.[7] Through rich case studies and careful process-tracing—including interviews with principals—Holmes adeptly highlights the importance of interpersonal relationships between leaders, showing that it is not simply leader-level characteristics that shape foreign policy outcomes, but also the bonds that develop between them. Some political scientists may have physics envy, but Holmes is interested in chemistry.

The book is especially propitiously timed because it comes at a moment when political scientists are increasingly interested in diplomacy more generally; the Diplomatic Studies Section of the International Studies Association (ISA), for example, has nearly three times as many members today as it did a decade before this book was published.[8] Yet because of the interdisciplinary implications of Holmes’s arguments, it also goes deep into philosophy of mind and social neuroscience; the book has noticeably more macaques in it than does the modal book on diplomatic summitry. And, it is as admirably reflexive (as only work on non-reflexive logics of action can be), raising thoughtful questions along the way about the risks and rewards associated with interdisciplinarity in an era of unsettled science, how we choose the right level of analysis for our theories, and so on, questions that make the book as valuable metatheoretically as it is substantively. The book is therefore a major contribution and crucial read not just for scholars of diplomacy and political psychologists, but also for students of international politics more broadly.

The chief contribution of the book, however, and what it will likely be the most cited for, is its emphasis on the power of face-to-face diplomacy – even though Holmes’s care as a researcher and interest in negative cases means that the book assiduously avoids overclaiming what face-to-face diplomacy can and cannot accomplish. In my comments below, then, I focus on three potential limits or scope conditions of face-to-face diplomacy worth keeping in mind. The first concerns the boundaries of theories of private information, the second concerns our own limitations in detection deception, and the third concerns open questions about how actors weigh countervailing indicators of intentions.

First, because the force of face-to-face diplomacy is posited to come through deception detection, it is perhaps worth noting what problems face-to-face diplomacy cannot solve. Face-to-face diplomacy mitigates problems of private information, but not time inconsistency; it solves the synchronic security dilemma, not the diachronic one (244). It should be the most effective in a world of unitary actors, rather than one of principal-agent problems; it provides no succor for managerial approaches to noncompliance, nor Gorbachev’s concerns about “free-ranging bureaucrats” (109).[9]

Interestingly, it also requires actors to have intentions to (mis)represent in the first place, “specific” rather than “broad” intentions (71). Thus, while Face-to-Face Diplomacy’s turn to simulation theory upends the traditional model in IR in which actors have private information that they can access and others do not,[10] it subverts the latter clause rather than the former. An alternative perspective, which subverts the former clause but not the latter, might suggest that the traits we think of as private information are emergent properties that we cannot directly access ourselves. [11] For example, in social psychology, self-perception theory argues that we only come to know our internal states by observing our own behavior, such that we are forced to draw inferences about our own dispositions much in the same way we do about others.[12] Another dissenting tradition, manifested in the work of Jon Elster, George Ainslie, and others, is similarly skeptical towards claims of actors armed with well-developed singular intentions; while IR scholars debate whether the unitary actor assumption applies to collective actors like states, scholars in other fields are less certain as to whether the unitary actor assumption even applies to individuals.[13]

Second, how sanguine should we be about our ability to read the minds of others? On the one hand, the book frequently emphasizes that our mirroring system has polish: these neutral substrates of empathy operate effortlessly and automatically at the level below conscious awareness (50), make “social life possible” (21) by enabling us to make hundreds of subtle emotional distinctions each day (32), and permit us to “have sophisticated, precise, and reliable access to the minds of others” (241). On the other hand, we also know that many of us are quite bad at putting ourselves in others’ shoes. Merely having the capacity for empathy doesn’t mean we are motivated to engage in it, and doesn’t mean that when we do engage in it that we do so accurately.[14]

Perhaps the clearest sign of our limitations in mind reading is our obsession with transcending them. Our television news networks and tabloid papers alike are filled with interviews with ‘body language experts’ who weigh in on everything from the testimony at the Brett Kavanaugh Supreme Court nomination hearings to the micro-expressions of Meghan Markle at Buckingham Palace social gatherings. Although increasingly distrusted by the legal system, the polygraph test remains the idée fixe of popular culture. Three of the most popular TED talks to date concern body language, detection deception, and the power of empathy.[15] If detection deception is so intuitive, why does it need to be taught, and what do we need the experts and contraptions for?

More generally, this tension reflects an interesting ambivalence within the psychological literature about the nature of automatic “System I” processing, which is understood to be intuitive, effortless, and necessary for survival, but also potentially prone to systematic bias.[16] Beyond the matter of the mean, there is also the question of the variance. The book acknowledges that individuals vary in their ability to detect deception, and posits that leaders are likely to be better at it given their higher levels of emotional intelligence (54). Yet some other psychological research argues that individuals in positions of power tend to fare worse at perspective taking, and are less sensitive to others in general.[17] Leaders may be better, but they also may be worse.

Third, how much weight do individuals ascribe to cues obtained through face-to-face interaction? Such interaction is valuable in IR because it reduces uncertainty, and it reduces uncertainty because it provides additional information. Some of this additional information may be conveyed through visual or audio cues, like emotional outbursts (221). Others may be conveyed through afferent feedback produced by nonconscious facial mimicry. Research suggests that Botox injections, for example, impair the ability of individuals to read others’ emotions, because the reduced mobility of their own facial musculature limits their ability to simulate others’ facial expressions, and thus, to feel what others are feeling.[18] Yet these nonverbal and afferent cues are not the only pieces of information to which decision-makers have access, and often times the information obtained in personal interactions may contradict information obtained through other channels.

How do decision-makers weigh these different inputs, particularly when faced with competing or countervailing considerations, such as when leaders’ faces say one thing, but their past actions say another?[19] How do different types of cues interact with one another in assessments of trustworthiness or credibility, when neither is more vivid than the other?[20] The case studies suggest it is not as simple as affect trumping cognition, or automatic judgments overpowering deliberative ones: Gorbachev relied more on his personal intuitions when faced with complex information environments (143), while Prime Minister Neville Chamberlain ignored Chancellor Adolf Hitler’s visual deception cues due to motivated reasoning and the likeability heuristic (227-230). A promising avenue for future research, then, is to attempt to better understand the conditions in which different types of nonverbal cues dominate. In pushing us to wrestle with these questions, and in bringing the interpersonal into the international, Face-to-Face Diplomacy does us an important service.

Review by Rose McDermott, Brown University

In arguing for the value of face-to-face diplomacy, Marcus Holmes correctly notes that “[i]ntentions represent a hard problem for IR” (20). He then goes on to postulate that “the problem may be overstated” (21). Noting that the problem of understanding another’s intentions constitutes both a philosophical as well as a psychological issue, Holmes put forth a case for the power of simulation theory to overcome the challenge of reading other minds. In this view, rather than theorizing about how others are thinking and feeling, individuals can engage in a form of introspection and intuit what another might be experiencing based on an automatic, effortless simulation of the experience in themselves. This intuition depends in part on the functioning of so-called mirror neurons that help facilitate this process. Because this ability depends on reflecting and mimicking another’s behavior, movements, and facial expressions, face-to-face contact not only enhances the accuracy of such intuitions, but in many cases is what facilitates this ability in the first place, according to this model. The power behind such face-to-face signaling in this model lies in its ability to signal emotions. Thus, rather than talk being ‘cheap,’ it provides more authentic signaling precisely because it can be so cognitively taxing to dissemble in person, creating opportunities for behavioral leakage which others can then understand as indicators of deception or malicious intent.[21]

Holmes tracks recent work in cognitive neuroscience to make the case for the role of simulation theory in general, and mirror neurons in particular, in order to examine important diplomatic exchanges between leaders in international relations. Cases include President Ronald Reagan and Soviet leader Mikhail Gorbachev, President Jimmy Carter at Camp David, and Prime Minister Neville Chamberlain and Nazi leader Adolf Hitler at the Munich Conference in 1938. He also provides telling anecdotes related to President Franklin D. Roosevelt at the Yalta Conference in 1945, and the summit between President John F. Kennedy and Soviet leader Nikita Khrushchev at the Vienna summit in 1961, just prior to the Cuban Missile Crisis, in the introduction and conclusion, respectively. In so doing, Holmes seeks to demonstrate the unique power of face-to-face interactions in striving to overcome the perennial challenge of understanding another leader’s intentions in high stakes situations in international relations.

Holmes takes on an ambitious project in attempting to apply cutting-edge social neuroscience literature to the archival record in international relations. This type of application can open up important new areas of research, and allow for the formulation of questions in new ways, the inclusion of different kinds of evidence, and the possibility of generating new hypotheses to explain complex and idiosyncratic behavior. Certainly increasing interaction between political scientists and those working in psychology and cognitive neuroscience constitutes a very valuable enterprise.

There is a lot to be said for thinking about social interaction in terms of a theory of mind approach as opposed to the more traditional folk psychology models which tend to rely on a more general social-science model of human behavior that assumes all learning is socialized and offers little role for instinct or innate behavior in understanding motives for human behavior. In the social neuroscience literature, this contrast has been most valuably explored in the investigation of autism in particular by the noted neuroscientist Simon Baron-Cohen.[22]

One of the most interesting and important aspects of this system of reading other’s intention lies in the enormous individual variance in the capacity to do so accurately, even in the domain of detecting deception. As Holmes notes, some systematic factors, most notably narcissism, can interfere with the optimal operation of intention understanding. Narcissism can limit not only a leader’s capacity to read the intentions of others, but also their very interest in doing so. This is particularly important because many of the leaders we seek to understand rose to power precisely because they have the kinds of characteristics that drive them to seek attention from the outset. Thus, the presence of narcissism constitutes an important caveat and limitation on the ability to apply this model in many cases involving international leaders.

The anecdotes related to Roosevelt and Kennedy are particularly evocative for me because these are cases I worked on in depth in my book on presidential illness.[23] In both cases, the president was severely ill, and, in the case of Kennedy, under the influence of massive amounts of psychoactive drugs during the relevant encounter. These examples illustrate the challenges of separating mimicry from other forces. Specifically, in the case of Kennedy and Khrushchev, as well as Roosevelt, British Prime Minister Winston Churchill and Soviet leader Joseph Stalin, history and past associations mattered a great deal, and not always in the most obvious way. Kennedy felt that Khrushchev had beaten him up, and he told his brother, Attorney General Robert Kennedy that the exchange reminded him of experiences in his past with their father. Such references to powerful psychological transference abound in the historical record, one of the most prominent being President Harry Truman’s strong association of Stalin with his old Democrat party boss from Missouri, Tom Pendergast. Such example raise interesting questions that can work in both directions: were these individuals reminded of others by visual factors or physical patterns manifested by certain leaders? Or did they, in turn, react to such leaders more as they wished they had reacted to whoever they were reminded of, and not to the leader they actually confronted?

As Holmes notes, repeated interactions help individuals learn about one another’s patterns, and how intention might be associated with things like facial expressions and vocal pitch. This raises another aspect of this model that is less emphasized but could potentially be even more important when leaders are trying to read other individuals, and that relates to body language. Although the emphasis here is on facial expression, this is really only one aspect of in person communication, and perhaps not even the most important. While a greater emphasis on somatic elements, such as those emphasized by Antonio Damasio as critical sources of information, would not necessarily undercut the simulation model, it does seem important, if this model is correct, to further explore not only facial expression and vocal patterns, but also body language which can quickly, effectively, and powerfully communicate signs of dominance or affiliation.[24]

These cases highlight one of the challenges raised by a simulation-theory approach, and one that Holmes acknowledges. It can be very difficult to disentangle the role of mirror neurons specifically, and the role of simulation more generally, from other factors that can influence behavior in profound ways in any given situation. It can be very difficult to analytically separate the role of simulation from other factors, including other cognitive and emotional factors, especially given the inaccessibility of such information not only to other people, but to oneself as well.[25] And, as Holmes notes, “[d]isaggregating mirroring of specific intentions, for example, from other types of mirroring, such as facial expressions, emotion and so forth, is a particularly challenging proposition” (66).

This raises the broader point that simulation theories remain quite controversial within the field of cognitive neuroscience. Rebecca Saxe, for example, argues against simulation theory, claiming that the reasoning errors that individuals make are not consistent with simulation models.[26] Instead, she suggests, while there is substantial evidence for co-opted mechanisms that allow for matching mental states between individuals, there is much less evidence that this serves as a basis for attributing mental states to others.[27] The central challenge is one that Holmes himself acknowledges: “When it comes to theory building, a critical question revolves around the extent to which a focus on mirror neurons, either their latent link to motor actions, may be over-emphasized with respect to social cognition. That is, most of the mirror neuron studies to date have focused on relatively simple motor tasks and not the more abstract beliefs that are an integral part of social relations” (65). He goes on to cite the prominent neuroscientist Marco Iacoboni in noting the challenges associated with the “‘long reach’ between simple laboratory experiments with monkeys and bananas to humans and politics and social life” (65). And this represents the primary challenge of applying this model to complex social and political behavior. The original demonstration and documentation occurred in the realm of motor behavior and it is much more difficult to demonstrate its application to the much more complex realm of understanding social intention. Simply mimicking someone’s facial expression does not mean that you will feel what they do; different histories and dispositions can generate drastically different reactions to the exact same stimuli. And in such cases, the danger may lie not in the failure to mimic, but rather in the overconfidence that face-to-face interaction can generate if individuals incorrectly believe they have accurately read someone else’s intentions. Moreover, Holmes rightly notes that understanding does not equal agreement. We can accurately understand, after all, that someone else hates us and wants to kill us. The perception can be accurate even when the intention is malign. As Holmes writes: “The argument in this book is that face-to-face interaction provides a mechanism for intention understanding. This does not imply or guarantee, however, that intention understanding results in normatively desirable outcomes, preference change, or intention dynamism” (252). Of course, none of these positions constitutes the final word, and research in this area is active and on-going. But it does suggest that, while the notion of intention understanding through mirror neurons can be quite appealing in some ways, it may not be entirely correct.

Holmes is aware of these concerns and limitations, as well as the fact that his application rests on early days in some of these neuroscientific studies whose results could easily be over-turned and will certainly be refined over time. But that does not mean the enterprise is without merit. All of science progresses with small steps, and if we wait until everything has already been determined, we would never get anywhere. And, equally important, the enterprise of inquiry alone can raise unexpected and important new insights in entirely unexpected domains. As Holmes concludes:

“These questions point to a different understanding of change in the international system than is normally considered in systemic IR. If the nature of individuals themselves, and therefore the nature of the practitioners of international politics, the substance of the first image ‘human nature,’ changes based on experience, and can be trained to change in specific ways, then an unaccounted and unauthorized source of change in the international system may be in the first image. This type of change problematizes the notion of a static human nature and resonates with arguments that place the individual front and center in constituting, and replicating, the international system” (269).

This perspective follows in the important tradition put forward by Robert Jervis, among others, that individuals matter, and we neglect their influence, however manifested and measured, at our peril.[28]

Review by Andrew A. G. Ross, Ohio University

In Face-to-Face Diplomacy, Marcus Holmes makes an invaluable contribution to both the study of diplomacy and the ontology of interpersonal interaction. While the intricacies of diplomatic interaction have excited historians, the topic has attracted less attention among International Relations (IR) scholars looking to build theories of international politics. Holmes reverses the trend by injecting a novel conceptualization of what exactly is happening when leaders and diplomats are engaged in face-to-face meetings. Drawing from recent research in social neuroscience, he demonstrates that leaders are more than just calculating machines exchanging information: they are embodied actors whose brains actively simulate the mental states of others and, as such, routinely gain direct access to otherwise hidden intentions. Holmes leverages this account of intersubjectivity to dismantle an entire edifice of theorizing built on the problem of other minds, inaccessible intentions, and the distrust that ensues therein. The result is a potential game-changer not only for the study of diplomacy but also for efforts to understand other forms of social interaction in international affairs.

Even as Holmes sets out to transform the study of strategic diplomacy, he concedes that the linkages between sharing intentions and building trust are far from straightforward. Leaders may experience some form of neural simulation processes, these may even engender “empathy,” and yet the politically coveted outcome of “trust” may fail to materialize. Empathy, as Holmes explains, is a necessary but not sufficient condition for the production of trust (247). The concession signals an underlying tension between the normatively inflected outcomes that are of interest to the social scientist and the experimental objectives of the mirror neuron researcher: while the former seeks to understand the conditions under which specific kinds of normatively coded behaviors are generated, the latter maps the ‘social brain’ without the same normative investments. It is as yet unclear whether social scientists—whose objects of study are so inherently intertwined with concerns about justice, peace, and their antinomies—could (or should) internalize the neuroscience of mirroring, simulation, and empathy without overcoding it with normative value.

In his meticulous consideration of disconfirming cases and possible objections, Holmes ultimately assembles a rich catalogue of cases for which mirroring does not in fact produce trust—and in so doing lays out a promising area for future research. Holmes accepts that narcissistic personality characteristics and efforts at deception represent possible impediments to “intention understanding” (53-54, 228, 230). But we should take care to ensure that the acknowledgment of deviations does not naturalize a link between sharing intention and building trust. Describing such cases as ‘lacking trust’ may do us an analytical disservice as we set out to understand why mirroring may either not engender empathy or engender empathy but fail to produce trust. What social factors account for the gap between successful intention understanding and the achievement of trust?

Addressing that question requires moving from the rarefied conditions in which neural simulation has been heretofore detected by neuroscientists to the more multi-dimensional terrain of political interaction. Scholars in IR need to assess the findings of neuroscience for what they reveal about, as Holmes puts it, “the messy social and political world” (259). One obstacle relates to the fact that the intentions studied in early research on mirror neurons are the simple intentions associated with basic motor movements of the arm (44-46). Is the intention to reach for food comparable to—and is it subject to the same processes of neural simulation and inference as—the intention to mobilize for war, the intention to enact some compromise toward peace, or other intentions germane to diplomacy? Moreover, does the mere occurrence of mirroring, or even the successful inference of others’ intentions, tell us about what beliefs or behaviors follow from interpersonal interaction? Trust is a possible outcome, but under what conditions does it become the most likely one?

In the messy world of politics, neural simulation takes place in social contexts that are cluttered with values, prejudices, and conditions of intelligibility. Such influences are commonplace—indeed, often insidious—in everyday interactions, and it would be surprising if they did not condition mirroring processes in some way. One pair of researchers in social neuroscience argue that different people possess different “vocabularies” that shape the responses a person mirrors most actively.[29] Early studies involving reaching for food involve an act that is universally recognizable, at least for species that use opposable thumbs to handle food. But what differences of ‘vocabulary’ exist that might modulate mirroring responses in the social world? Giacomo Rizzolatti and Corrado Sinigaglia explain that a person who has never taken a dance lesson will be affected differently by the sight of dance steps than an experienced dancer. For the IR scholar, the existence of differential vocabularies means that simulation may be either enhanced or diminished by the social and cultural influences that populate the practice of diplomacy.

More broadly, these considerations point to important questions about the power relations that accompany face-to-face interactions. Holmes recommends further study on the interpersonal as a site of power relations, noting that “individuals possess different levels of perceived interpersonal power” (261). But if each of us brings different socially produced repertoires of recognition and intelligibility to the process of neuronal simulation, the power relations at play in interpersonal interactions are always both individual and social. One recent study finds that neural responses associated with empathy are more acute in cases where bodily pain is observed in subjects perceived to be members of an ethnic ingroup, and dampened where they are seen in members of an outgroup.[30] Even if intentions are shared in the manner Holmes expects, what assortment of implicit biases and discriminations—relating to ethnicity, race, gender, and so on, and activated by skin color, gesture, fashion, and other embodied signs—might affect whether that initial achievement translates into empathy?

Beyond the linkages between simulation, empathy, and trust, Holmes’s analysis raises important questions about the social context in which face-to-face interactions are staged. He does a masterful job of revisiting classic cases with a fresh analytical agenda, telling a new story about the neurosocial signature of negotiations that are conducted in-person. Indeed, although lacking a strong interest in elite diplomacy, I found myself quite captivated by the tale. But, even as the arguments compel, they reveal additional puzzles concerning the relationship between face-to-face accomplishments and the wider context of preparatory work, preceding meetings, and events on the ground that establish their conditions of possibility. Holmes is extremely thorough in documenting the ministerial and diplomatic legwork that preceded landmark meetings, but the question remains as to how such ancillary developments carry over into a given face-to-face encounter. When U.S. Secretary of State George Schultz described a “Gorbachev euphoria in the air” (91) or U.S. National Security Advisor Brent Scowcroft an “atmosphere of comradeship” after a meeting between U.S. President George H.W. Bush and German Chancellor Helmut Kohl (137), can subsequent face-to-face interactions be isolated from those ambient conditions?

Moreover, as media technologies proliferate, the boundaries demarcating face-to-face interactions become even more porous. While U.S. President Jimmy Carter deliberately sought to minimize media access to the Camp David Summit (174), the advent of mobile computing, citizen journalism, and digital diplomacy now frustrate attempts to insulate meetings from the public gaze. Holmes argues that the proliferation of information in the form of letters, cables, and phone calls may create an information overload for which in-person meetings was the remedy (145-146). Such a connection seems plausible, but it also underscores the feedbacks connecting mediated and direct communications. Even as leaders focus on maintaining the element of personal contact, an abundance of information continues to circulate before, during, and after the diplomatic exchange.

The separability of direct and mediated diplomatic communication has both social and neural dimensions. Holmes cites a post-war statement by British Prime Minister Winston Churchill in which he disparages written communication that is rapidly transmitted but impotent relative to “personal contact” (238). But the possibility of conveying intentions through mediated communication is now a question for both diplomatic history and neuroscience. Indeed, there is evidence that the simulation processes involved in mirroring involve sensory inputs of a visual, auditory, and tactile nature. One neuroscientist suggests that the difference between mediated and face-to-face interactions is that the latter affords the possibility of a multimodal experience that combines sensory inputs of different kinds.[31] As work in media theory indicates,[32] however, digital media are augmenting the possibilities for multimodal communication, as written texts are accompanied by audio and video content, and all are curated and distributed across social media platforms. In this technological context, how much of the multimodal density formerly confined to face-to-face interactions is now also present within mediated communication?

Many contemporary scholars and commentators maintain a healthy skepticism about the advent of digital diplomacy, especially in light of the unfiltered use of Twitter by heads of state. And Holmes is surely correct that new practices of data gathering “lack … the information richness, visuality, and optics of face-to-face interactions that allow for intention understanding” (267). But the question remains as to how densely mediated environments of communication pre-figure the face-to-face meetings embedded within them. As leaders meet in person, they may seek to bypass the noise of media chatter, but is it not increasingly difficult for them to scrub any knowledge of it? And the accelerations associated with live-Tweeting and livestreaming may diminish the temporal space for painstaking discussions of the sort staged by Carter. Holmes rightly notes that further research will be needed to explore the impact of media technologies on face-to-face diplomacy. My own hunch is that an especially productive avenue will involve investigating how seemingly direct interactions are increasingly affected by and embedded within processes of mediation.

Review by Keren Yarhi-Milo, Princeton University

Face-to-Face Diplomacy offers an important contribution to the study of diplomacy in international relations. This book adds to a resurgent literature on how leaders matter in international politics; the credibility of costless communication; and the importance of diplomacy more generally. Marcus Holmes offers a new theory, which draws heavily on insights from social neuroscience, to explain what makes face-to-face diplomacy a powerful tool of statecraft and for understanding other leaders’ intentions.

There is a lot to like about Face-to-Face Diplomacy. The theory is novel and compelling; the case studies are substantively important; and the book’s theoretical and policy implications are evident. Face-to-Face Diplomacy is the kind of book that one will remember when a photo of a meeting of two leaders appears. It is not only the kind of book that answers important questions, but also one that raises new ones.

In this spirit, I will highlight three main questions that I feel deserve more attention. I should mention that these questions are not solely aimed at Holmes’s book, but also my own scholarly work on the subject. Indeed, Holmes and I published an article together on the psychological logic of face-to-face interaction between leaders during peace summits, emphasizing the importance of empathy between leaders in determining their success or failure.[33] Todd Hall and I also published our own take on why face-to-face diplomacy matters, dealing with some of the same case studies that Face-to-Face Diplomacy explores, specifically during the interwar period and end of the Cold War.[34] My first book, Knowing the Adversary, dealt with the question of how leaders assess each other’s intentions, and showed how the vividness of face-to-face interactions makes them a salient indicators leaders use to gauge each other’s types.[35] Thus, given my own deep interest and contribution to this literature, I view my comments not as criticism of Face-to-Face Diplomacy, but as an opportunity to reflect on the questions this book, and other scholarship on the subject, should delve into more forcefully.

First, Face-to-Face Diplomacy, and much of my work on this topic, deals with the question of what happens when leaders meet in person. The process by which face-to-face diplomacy works, and why it is an effective tool of understanding intentions, is perhaps the central question with which we should concern ourselves. But there is a second, and highly related, set of questions that bear directly on the question of leaders’ intentions. For example, under what circumstances is face-to-face diplomacy more likely to take place?[36] Why are some leaders more prone to engage in face-to-face diplomacy than others? Understanding the dynamics that give rise to face-to-face diplomacy could offer important context for the outcomes this book seeks to explain. Specifically, some leaders appear to value face-to-face diplomacy more than others and are willing to take greater political risks to engage in such diplomacy. But what explains this variation among leaders? Alternatively, some leaders view this type of diplomacy, especially with adversaries, as a sign of weakness; still others perceive it as an indicator of confidence and strength. Face-to-Face Diplomacy, because of its focus on mechanisms and outcomes, is silent on this question. Yet, one could wonder whether there is an underlying systematic factor that shapes, on one hand, leaders’ willingness to engage in such diplomacy in the first place, and on the other hand, their assessments of others’ intentions.

Second, Face-to-Face Diplomacy focuses on the processes by which interpersonal meetings between policymakers, especially heads of state, affect the assessment of leaders’ intentions. Holmes’s work is unique in drawing on social neuroscience, especially the role of mirror neurons, to explicate the mechanism by which face-to-face diplomacy operates. Nevertheless, as Holmes himself admits, it is not feasible to “prove” or “show” that mirroring is the key mechanism at play in the historical cases he investigates. Indeed, readers are asked to make a “theoretical bet,” as Holmes puts it, on whether the causal mechanism he posits is in fact the one that drives actors’ assessments during face-to-face interactions (15, 67, 76). Thinking about this further, I wonder to what extent we need to believe in Holmes’s proposed mechanism in order to believe the larger argument of this book? If so, is this a problem? And if so, how big of a problem? The book could go further in unpacking for the reader the extent to which the difficulty in identifying the underlying mechanism with confidence (given its lack direct observable implications) should cast doubt on the validity of the case studies.

Finally, Face-to-Face Diplomacy offers a sophisticated account of how this type of diplomacy is not only useful for assessing others’ intentions, but also for detecting deception. The issue of deception, however, could have been given further treatment. The book is mainly concerned with deception only during face-to-face interactions, that is, with the ability of the actor to detect a lie through micro-expressions. But the issue of deception detection is a larger phenomenon that deserves further attention. For one, it is unclear what type of deception Face-to-Face Diplomacy is really capturing. It seems to me that face-to-face diplomacy might allow leaders to detect a particular type of deception—one that involves flat-out lying. But deception between countries goes well beyond lying to one’s face, including the omission of important information, the deliberate use of ambiguous language, or true uncertainty that is interpreted as deception. One could therefore ask how important the deception that leaders may detect within face-to-face diplomacy is, compared to other types of deception, which are also fundamental to leaders’ understanding of intentions, but cannot be detected in interpersonal interactions. The analysis in Face-to-Face Diplomacy could further develop this point both theoretically and empirically, especially in the case study of British decision-makers’ inferences made from interacting with German dictator Adolf Hitler in the lead up to World War II.

One interesting set of questions that arises from this book’s analysis concerns the extent to which judgments and beliefs formed during face-to-face diplomacy uniquely affect leaders’ subsequent behavior. For example, do leaders who detect their counterpart to be lying during a face-to-face meeting, or who later learn that a leader had been lying to them during a face-to-face meeting, react more aggressively than leaders who are the recipients of lies outside of face-to-face interaction? Will leaders who form beliefs about another leader’s intentions during face-to-face interactions be less likely to change their beliefs in the presence of contradictory evidence, compared to leaders who formed beliefs about another leader’s intentions through other means such as intelligence reports, diplomatic actions, behavioral signals (i.e., not face-to-face factors)? Are leaders who were deceived in past interactions less likely to rely on their impressions during subsequent face-to-face interactions? Those are, in one respect, important empirical questions, but they also have theoretical significance. A systematic answer to those questions—which is obviously beyond the scope of this book —could further underpin the causal role of face-to-face diplomacy in shaping leaders’ behavior.

In sum, Face-to-Face Diplomacy did not need to convince me that this type of diplomacy is an important tool of statecraft and a method that leaders use to infer intentions of others. I was already convinced. But Holmes’s monograph offers a very strong and effective account of why and how face-to-face diplomacy matters, and in so doing significantly raises the bar for future scholarship on this topic.

Author’s Response by Marcus Holmes, College of William & Mary

I am immensely grateful to Brian Rathbun for writing the introduction to this roundtable, and to Joshua Kertzer, Rose McDermott, Andrew A. G. Ross, and Keren Yarhi-Milo for their insightful and thoughtful assessments of my book, Face-to-Face Diplomacy: Social Neuroscience and International Relations. It is an amazing privilege to have such fine scholars, all of whom have been a tremendous influence on me, read deeply and respond to one’s work. Each of them raises important issues, many of which I have grappled with myself in the process of writing the book as well as afterward, and also help to identify areas for fruitful future research. While I do not have space to address all of the points raised, I do wish to pick up on a few broad themes and specific issues that were raised in the reviews: (i) the antecedents to face-to-face diplomacy; (ii) its relationship to trust; (iii) the mirroring system causal mechanism; (iv) the effect of digital technology on face-to-face interactions; (v) and areas for future research.

Antecedents to Face-to-Face Diplomacy

While Face-to-Face Diplomacy is focused on face-to-face interactions, and the understanding of others’ intentions that can result from such encounters, Keren Yarhi-Milo is exactly right to note that there are important questions to be asked regarding the conditions under which face-to-face interactions take place. As she notes, some leaders seem to jump at the opportunity to meet personally with friends and adversaries, while others are happier staying home. What explains this variation? And, is it possible that whatever determines whether one seeks face-to-face meetings might also shape intention assessments in those meetings? While Face-to-Face Diplomacy does not focus on these questions, these are questions that represent one of my current areas of research. I would like to suggest two preliminary answers.

In a recent paper, Nicholas J. Wheeler—whose recently published book, Trusting Enemies, also engages deeply with face-to-face interaction as it relates to bonding and trust-building—and I argue that one way to address the puzzle of why face-to-face diplomacy sometimes occurs, and other times does not, involves the extent to which leaders possess security dilemma sensibility (SDS).[37] SDS refers to “an actor’s intention and capacity to perceive the motives behind, and to show responsiveness towards, the potential complexity of the military intentions of others. In particular, it refers to the ability to understand the role that fear might play in their attitudes and behaviour, including, crucially, the role that one’s actions may play in provoking at fear.”[38] The logic behind SDS is that individual leaders may appreciate that others are possibly operating from a position of fear and insecurity, rather than from aggression and predation. If so, they may be amenable to diplomacy as a way to both convey that understanding to their adversary as well as to potentially de-escalate the conflict. Wheeler and I conceptualize SDS as varying both in terms of intensity of the strength of an actor’s intention and capacity, as well as in the extent to which actors believe the other actor in the dyad may possess, or is open to possessing, SDS. Put simply, SDS is a variable and leaders will vary in the extent to which they possess it (what we call ‘inward SDS’) and believe that the other side possesses it (‘outward SDS’). The extent to which leaders possess inward/outward SDS, we think, helps us explain generally why some leaders are more willing to meet than others, as well more specifically why some dyads of leaders are more likely to meet than other dyads.

The second way I think about this question of who pursues face-to-face diplomacy is to consider who might be more likely to possess outward or inward SDS in the first place. First, with respect to outward SDS, generalized vs. particularized trust – how likely leaders are to trust folks outside of their moral community – is likely highly relevant.[39] All else being equal, it is likely the case that particularlized trustors have a more narrow moral community that limits their desire to engage in diplomacy, whereas generalized trustors will exhibit more of a willingness to engage with others, even distant others outside of their moral community. Second, variation in leaders’ reliance on intuition likely matters as well. One of the salient moments I reference in the book relates to President Ronald Reagan’s strong intuition that he needed to get a Soviet leader in a room together so that he would be able to explain U.S. intentions and policy. Others, such as Secretary of Defense Caspar Weinberger, were much more circumspect, preferring to privilege intelligence and hard data over intuition.[40] High-reliance intuitional thinkers, we argue, may be more likely to take action to meet face-to-face since when it comes to outward SDS, intuition is often all there is to work with, as leaders try to interpret signals, costly and otherwise.

Finally, a third variable which we think helps explain the who and why of face-to-face interactions relates directly to Yarhi-Milo’s own work on self-monitoring: the extent to which people are aware of, and attempt to control, their expressive behaviors and can effectively navigate social interactions.[41] High self-monitors are likely to care very much about how they are perceived by others, and as such, will try to understand how others perceive them. Low self-monitors, on the other hand, are typically less observant of the wider social context and less concerned with how they are viewed and understood by others. They may tend toward acting upon their own beliefs regardless of what the social situation might otherwise dictate. With respect to face-to-face diplomacy, high self-monitors, being keenly aware of the social interaction in which they find themselves with an adversary, will be more attuned to how they themselves are perceived generally by the other and, crucially, how one’s own specific actions will be perceived by the other. This ability to think through the ramifications of one’s actions on the perceptions held by the other is akin to a form of empathy that may lend itself to successfully exercising inward SDS. Low self-monitors, on the other hand, relying not on how they are perceived by the other, and concerned less with the social interaction itself, are less likely to develop inward SDS for their concern is not explicitly on how one’s own actions will be perceived.

These are but three variables that may be relevant for understanding the determinants of when leaders meet face-to-face. This is an exciting area of research and has, just in the last few years, produced an impressive amount of scholarship.[42]

Relationship to Trust

One of the intriguing aspects of increased intention understanding is that it does not always lead to salutary outcomes. The reason is that taking advantage of someone, deceiving, or even dominating another often requires strategic empathy in the sense of understanding their intentions, motivations, interests, and desires. More generally, simply knowing the intentions of the other side is not a guarantee that interests will be aligned. As the famous line of Emperor Charles V goes, “My cousin Francis and I are in perfect accord – he wants Milan, and so do I.”[43] Andrew Ross therefore points to a crucial question, which is when and why is it that we sometimes witness trust developing from intention understanding and other times do not? More generally, why do some dyadic interactions between leaders result in trusting relationships, while others are mired in negativity? The cases in Face-to-Face Diplomacy highlight the disparity. Whereas Reagan and Soviet leader Mikhail Gorbachev were able to engender intention understanding and, subsequently, build trust and even bond with one another, President John F. Kennedy and Soviet leader Nikita Khrushchev were able at their summit meeting in Vienna in June 1961 to develop increased intention understanding, but not trust and certainly not a positive bond.

In a second paper, Wheeler and I attempt to theorize why and when face-to-face interactions engender not only intention understanding, but social bonds that result in trust.[44] We turn to micro-sociology – the study of human interactions at the smallest scales – an approach that has theorized the determinants of social bonding in everyday life. Drawing from U.S. sociologist Randall Collins, and related empirical studies on the determinants of social bonding, we develop a model of diplomatic social bonding that privileges interaction elements rather than the dispositional characteristics of the actors involved or the material environment in which the interaction takes place.[45] In particular, four conditions are necessary for a successful social bond: bodily co-presence, barriers to outsiders, mutual focus of attention, and shared mood. In the absence of any of these conditions a social bond will not form at all, or a negative emotional connection will engender. When the conditions are present, however, leaders in an interaction will experience positive emotional energy and the experience of “hitting it off” or having personal chemistry, with one another. Building on Wheeler’s arguments in Trusting Enemies we argue that it is precisely this bonding process that results in trust.

In the Collins model, bodily co-presence is crucial, partially because it allows individuals to “monitor each other’s signals and bodily expressions” such “that human nervous systems become mutually attuned.”[46] While Collins does not invoke the mirroring system directly (the book came out just as the first mirror neuron studies were being published), he notes the evolutionary importance of human nervous systems in being able to “pay attention to each other” and “more attuned to individualized social interaction.”[47] Explaining how we go from intention understanding to trust, however, requires consideration of two of the other crucial ingredients: mutual focus of attention and shared mood.

With respect to mutual focus of attention, Wheeler and I highlight the importance of shared SDS, which as noted earlier is an intuition that an adversary may be acting out of fear and not malign intent. If one side exercises SDS and the other does not, there is not a mutual focus of attention that both sides are responsible for the conflict and that each side realizes they are jointly trapped in this conflict together. However, through face-to-face interaction, each side may be able to jointly and simultaneously arrive at SDS and thereby satisfy the condition that it be the mutual focus of both parties. Prior to that moment we would not expect this condition to be satisfied. This further highlights the importance of bodily co-presence and the ability to see, and respond to, bodily signals in those interactions.

Shared mood is comprised of two constituent ingredients: positive identification of interests and humanization. Positive identification of interests is drawn from Wheeler’s analysis of trust-building in face-to-face interactions. It refers to a process by which “state leaders no longer [think] of their interests being autonomous, even if congruent… they need to see the other’s interests as their interests, and the other’s security and well-being as their security and well-being.”[48] This occurs when the individuals involved in an interaction share the other’s security concerns, but it does not necessarily imply that the positions held by both leaders will be the same. It may well be the case that two leaders ultimately have the same end-point in mind with very different strategies and positions on how that end-point should be reached. The second component of shared mood is humanization of the other. Wheeler notes the importance of “see[ing] the ‘human’ in their counterpart’s attitudes and behaviour rather than just a representative of cold state interests.”[49] Humanization may involve several processes that are facilitated by face-to-face interaction. As I discuss in Face-to-Face Diplomacy, psychologists have highlighted the peculiar ‘chameleon effects’ which occur when individuals interact face-to-face and automatically, and sub-consciously, adjust their own expressive behaviors to that of the other, mimicking facial expressions, bodily positions, and so forth, signaling to each that the other is not all that unlike the self.[50] More cognitively, empathy is also implicated here, as it is the process by which individual leaders conceive of the other as someone like themselves, with emotion and agency. Humanization is shared because it orients both sides to seeing the humanity in the other.

The upshot is that using the Collins model, we can begin to piece together the crucial question of ingredients to not just a face-to-face encounter that results in intention understanding, but one that results in trust-building as well. As with the determinants of face-to-face interaction, this represents a thriving, and exciting, area of current research.

Causal Mechanism

Moving to the causal mechanism, I wish to address some broader issues raised about the type of research strategy I employ in the book and then move on to specific issues about how the mechanism may be operating in the context of leader interactions.

The first issue relates to observability. As Yarhi-Milo rightly points out, “it is not feasible to ‘prove’ or ‘show’ that mirroring is the key mechanism at play in the historical cases he investigates” and she “wonder[s] to what extent we need to believe in Holmes’s proposed mechanism in order to believe the larger argument of this book? If so, is this a problem? And if so, how big of a problem?” Indeed, one could imagine a version of this book that did not engage with neuroscience at all. After unpacking the problem of intentions and the broader philosophical problem of other minds I would then outline, as I do in Face-to-Face Diplomacy, the various behavioral and observational studies in psychology, economics, and so on over the last 60 years that suggest that face-to-face interaction is intimately connected to intention understanding. I would then be able to build a theory based on previous studies and test the theory in the same way I do in the book, through historical case studies.

There are several reasons why I believe there is value in digging deeper for causal mechanisms, at least in this case. First, not all unobservable causal mechanisms should be treated equally; some are more unobservable than others. While the mechanism I have identified may not be visible in case studies, it should be visible in the laboratory. With neuroscience technologies advancing at an extremely rapid rate, we should soon be able to test the theory laid out in Face-to-Face Diplomacy in the lab. Dual functional magnetic resonance imaging (fMRI) technology, for example, will likely soon make it possible to measure brain activity in two individuals simultaneously, as they interact face-to-face.[51] This makes the theory falsifiable not only at the observational/behavioral level in case studies, but falsifiable at the mechanism level as well. Comprehensive falsifiability, as it were, is one benefit of articulating a testable material mechanism.

Second, the causal mechanism in this case allows for better theory-building. One of the unresolved issues that emerges from the impressive amount of scholarship on face-to-face interaction is when it fails. That is, why do face-to-face interactions sometimes result in intention understanding and other times do not? The mirroring system provides an answer at the material level: intention specificity. Without insights from the mirror neuron studies, it would be difficult to theorize intention specificity as a condition for face-to-face interaction. As I argue in the book, this is one of the main benefits of turning to social neuroscience: it provides inspiration in theory-building and allows for new ways, potentially path-breaking ways, of thinking about old problems. Ultimately, the discovery of the mirroring system provides a material basis that pulls together, and helps to make sense of, the decades of disparate findings about face-to-face interaction I mentioned above.

Finally, and more broadly, while identifying material causal mechanisms in the body that may be unobservable in certain instances introduces certain problems, it does have the virtue of avoiding the pitfalls of poorly articulated, under-theorized, or even missing mechanisms. For example, in much of the existing literature that has looked at face-to-face interactions, mostly in diplomacy, there is little by way of examination of how specifically face-to-face diplomacy actually works. This is a point I made in the book. Assumptions are often made, usually unstated, and left unconnected to the chosen empirical approach. As a result, one is often left not only with an unsatisfying account of face-to-face diplomacy but oftentimes with more questions than answers. This issue is not just germane to diplomacy, of course, and has been raised by many others in the social sciences. As Jon Elster puts it, “To explain is to provide a mechanism, to open up the black box and show the nuts and bolts, the cogs and wheels of the internal machinery.”[52] In IR, recent work by Rudra Sil and Peter Katzenstein have highlighted the need to focus on mechanisms, both in terms of theory creation and theory testing.[53] I share this sentiment and my position is that good theory includes the articulation of specific causal mechanisms, even if they are not directly testable, as it aids in theory precision, reduces ambiguity, and ultimately results in more comprehensive and satisfying theory. We need to take causal mechanisms seriously (when we can), even if it may mean being vulnerable to new lines of critique.

One such critique relates to the extent to which simulation, through the mechanism of the mirror neuron and broader mirroring system, is actually doing the work in intention understanding. As McDermott rightly notes, “simulation theories remain quite controversial within the field of cognitive neuroscience.” She argues that some, such as Rebecca Saxe, have argued against simulation theory and that the leap from motor behaviors to social intention is indeed a broad one, presenting “the primary challenge of applying this model to complex social and political behavior.” Ross similarly wonders whether the findings from motor-based experiments can be applied to the more complex intentions and mental states we see conveyed in diplomacy contexts, replete with “values, prejudices, and conditions of intelligibility.”

To briefly recap relevant parts of the argument, there are two broad theories, or categories of theories, with respect to theory of mind, or the question of how we ascertain the mental states, including intentions, of others. “Theory theory” has been the dominant paradigm for several decades and simply posits that our understanding of the mind, and the minds of others, is based on a folk psychological theory consisting of frameworks and concepts that all together are “roughly adequate to the demands of everyday life.”[54] Put simply, in order to understand others we deploy a theory regarding their intentions. I make the case in Face-to-Face Diplomacy that much of social science, including IR theory, is based on a ‘theory theory’ understanding of how actors assess others. For example, costly signaling as a way to deduce trustworthiness of actors is based on the notion that actors will theorize that as the costs of an action escalates, so too should the sincerity, since “one would hesitate to send them if one were untrustworthy.”[55] This folk psychology theory, which includes a broadly rationalist framework, helps individuals to understand the intentions of others. ‘Theory theory’ approaches tend to privilege reflection and conscious deliberation over automaticity and intuition, and thus resonate with “System 2” ways of thinking, to use language associated with Daniel Kahneman, which was used originally by psychologists Keith Stanovich and Richard West.[56]

Recently, increasing attention has been given to simulation theory, which denies that we deploy theories to understand others, but rather use “the resources of [our] own minds to simulate… others.”[57] The roots of simulation theory are in empathy and the basic idea is that by placing oneself in the shoes of another being, one can simulate their mental states for oneself. An example from the work of Kahneman and Amos Tversky illustrates the logic: “Mr. Crane and Mr. Tees were scheduled to leave the airport on different flights, at the same time. They traveled from town in the same limousine, were caught in a traffic jam, and arrived at the airport 30 minutes after the scheduled departure of their flights. Mr. Crane is told that his flight left on time. Mr. Tees is told that his flight was delayed, and just left five minutes ago. Who is more upset?”[58] 96% of the sample thought that Mr. Tees would be more upset. Simulation theorists suggest that it is unlikely that individuals are applying a theory of plane delays, traffic jams, or the psychology of ‘just missed’ incidents to this situation, but rather simply simulating for themselves what it would be like to be in both positions. Since such an approach does not rely on reflecting upon what a theory says about a given situation, simulation theories tend to privilege automaticity and intuition over reflection and conscious deliberation, and thus resonate with a ‘System 1’ type of thinking. Some have articulated the distinction between simulation and theorizing as one of “bottom up” pre-reflective processes (such as mirroring) juxtaposed against “top down” effortful higher-level theorization.[59]

There are several reasons why simulation theories have gained considerable traction in recent years, not least of which because of the influential work on “fast” thinking by Daniel Kahneman, Amos Tversky, and others, who have provided an intuitive observation-based argument that much of our decision-making is pre-reflective, automatic, and more or less effortless.[60] Another important reason has to do with the discovery of the mirror neuron system in the brain. As mirror neurons literally simulate the intentional motor actions of others, they provide evidence that would support a more general simulation theory approach to understanding the mental states of others. Or, as Vittorio Gallese and Alvin Goldman put it, mirror neuron activity “seems to be nature’s way of getting the observer into the same ‘mental shoes’ as the target – exactly what the conjectured simulation heuristic aims to do.”[61] As I argue in Face-to-Face Diplomacy, these findings suggest a type of motor theory of social cognition, where mirroring aids individuals in understanding the intentions of others in face-to-face interactions.

Ross raises a great question, however, in questioning whether the simulation of intentional motor actions, such as banana grabbing (one of the early mirror neuron experiments), is really the same as simulation of other more complex mental states that may not seem to be motor-related at all. However, proponents of simulation theory often argue that even abstract intentions and higher-level mental states are indeed motor related. While these are difficult questions to study directly in social interaction with currently available technology, a few recent studies provide evidence to support this position.

First, Leonardo Christov-Moore and Marco Iacoboni have demonstrated that the level of mirror neuron activity predicts the level of generosity in the Dictator Game, an economic decision-making task that requires high-level and deliberate abstract thought, weighing of costs and benefits, and so forth. In this particular setup subjects first observed a human hand pierced by a needle, and then observed and imitated emotional facial expressions. They then made economic decisions while viewing the faces of those individuals that they were making decisions regarding. If motor mirroring was not involved in high level decisions, then we would not expect correlation between mirror neuron activity and outcome. Instead, mirroring brain activity predicted giving decisions: subjects with greater activity in areas of the brain associated with mirroring tended to give more generously than those with lower levels of activity in mirroring regions. Mirroring may allow individuals to put themselves in the place of those they are making decisions regarding, feeling their predicaments and making economic decisions accordingly. The evidence therefore suggests that “thinking about people is grounded on the perceptual and motor experiences we have when interacting with people.”[62] Put another way, mirroring activity in the brain is not just relegated to viewing simple motor tasks, but plays a role in higher level thought processes as well.

A second study similarly looked at neural resonance with the pain of others and whether this predicted judgments in moral dilemmas. Christov-Moore, Paul Conway, and Iacoboni measured individuals’ reactions to seeing another in pain, including classic mirror neuron centers in the brain, in order to determine if mirroring activity predicted moral judgments. The study found that brain response to viewing pain indeed predicted moral dilemma choices. Those with greater activity in brain regions associated with mirroring when viewing someone in pain were more likely to avoid causing harm to others (a deontological position rather than a utilitarian one). Put another way, a simple action of watching someone in pain, and the mirroring of that pain in the brain, was connected to much more complex decisions, presumably requiring conscious thought, including difficult moral dilemmas.[63] This lends support to motor theory of social cognition for high-level deliberative tasks.

A legitimate question to ask regarding these types of studies is whether the findings are merely correlations rather than causal. Put another way, is the mirroring activity of subjects when they see an individual in pain causal of prosocial giving behaviors in the Dictator Game? To study this, Christov-Moore and colleagues conducted a third study using transcranial magnetic stimulation which can temporarily “knock out” brain functioning in specific regions (and crucially participants go back to normal brain functioning after the experiment is over!). This is valuable because it allows researchers to hone in on very specific areas of the brain and test causal, not just correlational, hypotheses. In the study the researchers found that they could make individuals more generous by knocking out two areas of the prefrontal cortex that are associated with top-down executive control. This means that mirroring is not just correlated with prosocial behaviors, but it is causal of them. Put another way, simulation of pain drives prosocial behavior, executive control and theorizing, at least with respect to these particular brain regions, inhibits that response.[64]

These studies are not, of course, the final word on the matter. They are still far removed from analyzing actual social interactions, particularly as it relates to high-level diplomacy and intention understanding therein. On the other hand, they do, I think, illustrate three important points. First, as I argue above, the hypothesized causal mechanism of the mirror neuron system is increasingly observable in the lab. These studies combine both imaging and stimulation in order to assess causality rather than simply correlations. Second, they support a core proposition of Face-to-Face Diplomacy, which is that we need to start taking simulation theory seriously and ask questions about what it might mean if simulation is indeed at least part of the way that individuals come to understand the intentions of others. It should also be noted that the position taken by Face-to-Face Diplomacy with regards to simulation theory would actually be unsatisfactory to many simulation theorists as it does not go far enough. Indeed, some simulation theories suggest that simulation should not only replace ‘theory theory’ as the dominant paradigm, but also find little value in adopting a hybrid approach. In Face-to-Face Diplomacy I was careful to note that simulation theory and ‘theory theory’ likely both accurately describe how we assess mental states depending on the context (specifically in this case intuitions drawn from face-to-face interactions and the beliefs that follow from reflection), including intentions (33), which suggests more of a hybrid model.

Finally, it is therefore not surprising that Rebecca Saxe and others, as McDermott points out, have questioned the extent to which simulation theory can completely explain intention understanding. Kertzer, like Saxe, similarly points out the problem of error. If simulation theory explains how we come to understand the mental states of others, how is it that we make errors? The latest empirical simulation studies, and the empirical arguments made by Saxe and others, imply to me that a metaphor of two categories of theories, such as simulation vs. theorizing, is probably inadequate. In the recent studies mentioned above, mirroring neural responses (simulation) predict the more deliberate reflective decisions (theorizing) that individuals make when it comes to prosocial behavior. But we know theorizing is playing some role because when top-down control regions are knocked out prosocial behaviors increase. Thus, a strict separation between simulation and theorizing may be more of an illusion than accurate portrayal of how the brain and mind work. This is a point Face-to-Face Diplomacy makes in passing (33) as it attempts to bring simulation theory into the limelight, but one that could, and should, be given more attention in subsequent work in this area. The brain exhibits remarkable interconnectivity. Or, as Iacoboni puts it, “Everything in the brain is interconnected, so that the activity of each cell reflects the dynamic interactions with other brain cells and other neural systems.”[65] Rather than simulation and theorizing acting as two different “systems,” recent findings suggest more of a relationship of multi-level layers where each plays a role, perhaps at differing degrees. The ultimate challenge for future research is to better understand the interaction between automatic simulation processes and deliberate theorizing processes, particularly as it relates to outcomes we care about in world politics, such as diplomatic encounters.

Digital Replacement

The question I have received more than any other since the book’s release is how technology affects face-to-face interaction. Ross raises the prospect that digital communication technologies may be able to replicate face-to-face encounters. As technology advances, and the quality of digital transmissions increases, the prospect for multimodal density arises and may suggest that mediated communication could, one day, supplant physical co-present face-to-face interaction. A legitimate question that arises is whether, one day, we might witness leaders interacting through video conferencing technology, perhaps even replacing the physical visit, which can be costly, time-consuming, and pressure inducing in terms of domestic politics.

In other work I have investigated the extent to which ‘digital diplomacy,’ specifically the use of social media, allows leaders, diplomats, and other policymakers to develop relationships with foreign publics or other constituents in order to assess, and respond to, change in the international system.[66] While I have not looked specifically at the use of digital video technologies, there is some initial evidence to suggest that Ross’s intuition is indeed correct that space might take on different meaning in the digital realm; policymakers increasingly seem to be making use of video conferencing technologies.[67]

On the other hand, users often report that these types of video conferencing technologies are cold and impersonal, even awkward. Instead, individuals prefer the “interaction quality” of physical face-to-face interaction relative to its digital equivalent.[68] There are likely several reasons for this. First, related to a point made by McDermott, video conferencing technologies, while clearly more information rich than many other modalities such as telephone, text message, or Tweet, lack much of the sensory experience provided in face-to-face interactions. Not only is video-conferencing typically “head-to-head” rather than “body-to-body,” reducing the sensory input of expressive bodily behaviors that represent a significant amount of non-verbal communication,[69] but the medium, even at high resolutions, is not data-rich enough to allow individuals to pick up on subtle facial expressions, micro-expressions, and other expressive clues that may reveal mental states. Returning to Randall Collins’s take on bonding, it is also often the case that video conferencing makes it difficult to ensure outsiders are barred from a video interaction (individuals may be “off screen” but still capable of hearing or seeing the interaction), which likely limits the usefulness of the technology for bonding purposes.

Future Research

There are several areas of future research that the reviewers pick up on and I believe would be worth pursuing; I will only mention two here. The first relates to the question of the effect of individual traits, dispositions, experiences, and socially salient characteristics on face-to-face diplomacy. Yarhi-Milo asks whether what is learned in face-to-face diplomacy might affect subsequent behaviors, Ross questions what role gender, ethnicity, or race might play, while Kertzer and McDermott hone in on empathic accuracy/perspective-taking proficiency and individual illness and the effect of pharmaceuticals respectively. Yarhi-Milo’s aforementioned work on self-monitoring is an important multi-method prototype that can be used as the basis for the study of traits/dispositions/characteristics or experiences on face-to-face diplomacy, both in terms of decisions to engage in it and substantive outcomes from it. McDermott and Kertzer have also been leaders in utilizing experimental designs to isolate the causal impact of specific individual-level factors, or microfoundations, and similar designs could be utilized with current or former policymakers.[70]

A slightly different approach would involve the construction of comprehensive datasets on face-to-face diplomacy. Surprisingly, this is an area that only very recently has begun to see some traction. At the moment, available data focuses largely on who visits whom and what they discuss. Utilizing the approach by Yarhi-Milo, for example, it is conceivable that data could be collected not only on the interactions themselves, but on the relevant characteristics of the individuals involved as well. Such a dataset would allow researchers to not only test specific theories of diplomacy, such as the ones offered in diplomatic studies scholarship, but also the impact of face-to-face diplomacy on specific issue areas, such as deterrence or international trade.

A second area for future research relates to the problem of future uncertainty raised by Kertzer. As he rightly notes, Face-to-Face Diplomacy is ultimately focused on the synchronic problem of intentions rather than the diachronic problem. Put simply, face-to-face interactions help leaders to understand intentions in the present, but the core problem that intentions can change, ultimately remains. One way to think about the latter problem is that it is matter of converting the diachronic problem into a synchronic one. As Eric Parajon argues, for example, with enough face-to-face interaction it might be possible for leaders to be aware of when the intentions of their counterparts are indeed changing.[71] Close relationships, in other words, allow for reduced uncertainty.

A different approach, however, would be to think about future uncertainty in terms of aggregation processes. Whereas Face-to-Face Diplomacy focused on interactions at the highest levels – those between leaders – face-to-face diplomacy also takes place at other levels of interaction, including through institutions, governmental organizations, and between diplomats and civil servants.[72] A fruitful area for future research would be investigating the processes and precise mechanisms by which these interactions at non-leadership levels aggregate into macro-structures, such as security communities. Wheeler’s account of interaction between interpersonal interaction, bureaucracies at home, and the veto players that can sink a trust relationship provides a useful start.[73] The creation of a security community does not necessarily completely solve the diachronic problem of intentions, as it is an ever-present problem under anarchy, but it does move us to an environment where states, and the individual making decisions on behalf of the state, are less likely to worry about future intentions, or take them for granted, perhaps at their own peril.

Notes

[1] Keren Yarhi-Milo, Knowing the Adversary: Leaders, Intelligence, and Assessment of Intentions in International Relations (Princeton: Princeton University Press, 2014).

[2] Steven Bernstein, Richard Ned Lebow, Janice Gross Stein, and Steven Weber, “God Gave Physics the Easy Problems: Adapting Social Science to an Unpredictable World,” European Journal of International Relations 6:1 (2000): 43-76.

[3] See, for example, Brian Rathbun, Diplomacy’s Value: Creating Security in 1920s Europe and the Contemporary Middle East (Ithaca: Cornell University Press, 2014); Anne E. Sartori, Deterrence by Diplomacy (Princeton: Princeton University Press, 2005); Robert F. Trager, Diplomacy: Communication and the Origins of International Order (New York: Cambridge University Press, 2017); Seanon S. Wong, “Mapping the Repertoire of Emotions and Their Communicative Functions in Face-to-face Diplomacy,” International Studies Review viy079, DOI: https://doi.org/10.1093/isr/viy079.

[4] See https://www.state.gov/secretary/travel/.

[5] Scholars outside the United States have been less skeptical, although they too argue that diplomacy remains underappreciated in IR. See, for example, Paul Sharp, “For Diplomacy: Representation and the Study of International Relations,” International Studies Review 1:1 (1999): 33-57.

[6] Dale C. Copeland, “The Constructivist Challenge to Structural Realism: A Review Essay,” International Security 25:2 (2000): 187-212.

[7] Ted Hopf, “The Logic of habit in International Relations,” European Journal of International Relations 16:4 (2010): 539-561; Emanuel Adler and Vincent Pouliot, “International Practices,” International Theory 3:1 (2011): 1-36; Emilie M. Hafner-Burton, Stephan Haggard, David A. Lake and David G. Victor, “The Behavioral Revolution and the Study of International Relations,” International Organization 71:S1 (2017): S1-S31; Brian C. Rathbun, Joshua D. Kertzer and Mark Paradis, “Homo Diplomaticus: Mixed-Method Evidence of Variation in Strategic Rationality,” International Organization 71:S1 (2017): S33-S60.

[8] See “DPLST Reports,” https://www.isanet.org/ISA/Sections/DPLST/Reports.

[9] Abram Chayes and Antonia Handler Chayes, “On Compliance,” International Organization 47:2 (1993): 175-204.

[10] James Fearon, “Rationalist Explanations for War,” International Organization 49:3 (1995): 379-414.

[11] Joshua D. Kertzer, Resolve in International Politics (Princeton: Princeton University Press, 2016): 148-150.

[12] Daryl J. Bem, “Self-Perception Theory,” Advances in Experimental Social Psychology 6 (1972): 1-62.

[13] See, for example, George Ainslie, Picoeconomics: The Strategic Interaction of Successive Motivational States within the Person (Cambridge: Cambridge University Press, 1992); Jon Elster, The Multiple Self (Cambridge: Cambridge University Press, 1986).

[14] Nicholas Epley, Boaz Keysar, Leaf Van Boven, and Thomas Gilovich, “Perspective Taking as Egocentric Anchoring and Adjustment,” Journal of Personality and Social Psychology 87:3 (2004): 327-339; Nicholas Epley and Eugene M. Caruso, “Perspective Taking: Misstepping into Others’ Shoes,” in Keith D. Markman, William M.P. Klein, and Julie A. Suhr, eds., The Handbook of Imagination and Mental Simulation, (New York: Psychology Press, 2008).

[15] See https://www.ted.com/playlists/171/the_most_popular_talks_of_all.

[16] Daniel Kahneman, Thinking Fast and Slow (New York: Farrar, Straus & Giroux, 2011); Gerd Gigerenzer, “Why Heuristics Work,” Perspectives on Psychological Science 3:1 (2008): 20-29.

[17] Adam D. Galinsky, Joe C. Magee, M. Ena Inesi and Deborah H. Gruenfeld, “Power and Perspectives Not Taken,” Psychological Science 17:12 (2006): 1068-1074; Dacher Keltner, Deborah H. Gruenfeld and Cameron Anderson, “Power, Approach, and Inhibition,” Psychological Review 110:2 (2003): 265-284.

[18] David T. Neal and Tanya L. Chartrand, “Embodied Emotion Perception: Amplifying and Dampening Facial Feedback Modulates Emotion Perception Accuracy,” Social Psychological and Personality Science 2:6 (2011): 673-678.

[19] Joshua D. Kertzer, Jonathan Renshon and Keren Yarhi-Milo, “How Do Observers Assess Resolve?” British Journal of Political Science (forthcoming).

[20] Keren Yarhi-Milo, Knowing the Adversary: Leaders, Intelligence, and Assessment of Intentions in International Relations (Princeton: Princeton University Press, 2014).

[21] Robert Trivers, The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life (New York: Basic Books, 2011).

[22] Simon Baron-Cohen, Mindblindness: An Essay on Autism and Theory of Mind (Cambridge: MIT Press, 1997).

[23] Rose McDermott, Presidential Leadership, Illness, and Decision Making (New York: Cambridge University Press, 2007).

[24] Antonio Damasio, Descartes’ Error: Emotion, Reason, and the Human Brain (New York: GP Putnam’s Sons, 1994).

[25] Richard. Nisbett and Timothy Wilson, “Telling More than We Can Know: Verbal Reports on Mental Processes”, Psychological Review 84:3 (1997): 231.

[26] Rebecca Saxe, “Against Simulation: The Argument from Error”, Trends in Cognitive Sciences 9:4 (2005): 174-179.

[27] Rebecca Saxe, “The Neural Evidence for Simulation Is Weaker than I Think You Think It Is. Philosophical Studies 144:3 (2009): 447-456.

[28] Robert Jervis, Perception and Misperception in International Politics: New Edition (Princeton: Princeton University Press, 2017).

[29] Giacomo Rizzolatti and Corrado Sinigaglia, Mirrors in the Brain: How Our Minds Share Actions and Emotions (New York: Oxford University Press, 2008), 131-138.

[30] Igor Riečanský et al., “Beta Oscillations Reveal Ethnicity Ingroup Bias in Sensorimotor Resonance to Pain of Others,” Social Cognitive & Affective Neuroscience 10:7 (2015): 893-901.

[31] Christian Keysers, The Empathic Brain: How the Discovery of Mirror Neurons Changes Our Understanding of Human Nature (Lexington: Christian Keysers, 2011), 100-101.

[32] See, for example, J. David Bolter and Richard Grusin, Remediation: Understanding New Media (Cambridge: MIT Press, 1999).

[33] Marcus Holmes and Keren Yarhi-Milo, “The Psychological Logic of Peace Summits: How Empathy Shapes Outcomes of Diplomatic Negotiations,” International Studies Quarterly 61:1 (2016): 107-122.

[34] Todd Hall and Keren Yarhi-Milo, “The Personal Touch: Leaders’ Impressions, Costly Signaling, and Assessments of Sincerity in International Affairs,” International Studies Quarterly 56:3 (2012): 560-573.

[35] Keren Yarhi-Milo, Knowing the Adversary: Leaders, Intelligence, and Assessment of Intentions in International Relations (Princeton: Princeton University Press, 2014).

[36] For one recent study probing when and why high-level diplomatic events occur, see James H. Lebovic and Elizabeth N. Saunders, “The Diplomatic Core: The Determinants of High-Level US Diplomatic Visits, 1946-2010,” International Studies Quarterly 60:1 (2016): 107-123.

[37] Marcus Holmes and Nicholas J. Wheeler, “Overcoming the Four Horsemen of Diplomacy: Explaining Variation in Face-to-Face Engagement.” Workshop Paper (2019); Nicholas J. Wheeler, Trusting Enemies: Interpersonal Relationships in International Conflict (Oxford: Oxford University Press, 2018).

[38] Ken Booth and Nicholas J. Wheeler, The Security Dilemma: Fear, Cooperation, and Trust in World Politics (Basingstoke: Palgrave Macmillan, 2007), 7.

[39] Eric M. Uslaner, The Moral Foundations of Trust. (Cambridge: Cambridge University Press, 2002); Brian Rathbun, Trust in International Cooperation: International Security Institutions, Domestic Politics and American Multilateralism (Cambridge: Cambridge University Press, 2011).

[40] On this point, also see Keren Yarhi-Milo, Knowing the Adversary: Leaders, Intelligence, and Assessment of Intentions in International Relations (Princeton: Princeton University Press, 2014).

[41] Keren Yarhi-Milo, Who Fights for Reputation: The Psychology of Leaders in International Conflict (Princeton: Princeton University Press, 2018).

[42] See, for example, James H. Lebovic and Elizabeth N. Saunders, “The Diplomatic Core: The Determinants of High-Level US Diplomatic Visits, 1946-2010.” International Studies Quarterly 60:1, (2016): 107-123; Roseanne McManus, “Making It Personal: The Role of Leader-Specific Signals in Extended Deterrence,” Journal of Politics 80:, (2018): 982-995; Julia Gray and Philip B.K. Potter, “Diplomacy and the Settlement of International Disputes” (August 2017), https://ssrn.com/abstract=3012639; Seanon S. Wong, “Stoics and Hotheads: Leaders’ Temperament, Anger, and the Expression of Resolve in Face-to-Face Diplomacy,” Journal of Global Security Studies 4:2 (2019), 190-208; Deepak Nair, 