Conventional wisdom sees nuclear brinkmanship and Thomas Schelling's pathbreaking “threat that leaves something to chance” as a solution to the problem of agency in coercion. If leaders cannot credibly threaten to start a nuclear war, perhaps they can at least introduce uncertainty by signaling that the decision is out of their hands. It is not so easy to remove humans from crisis decision-making, however. Often in cases of nuclear brinkmanship, a human being retains a choice about whether to escalate. When two sides engage in rational decision-making, the chance of strategic nuclear exchange should be zero. Scholars have explained how risks associated with accidents, false warnings, and pre-delegation creep into nuclear crises. An investigation of how chance can still produce leverage while leaders retain a choice over whether and when to escalate adds to this scholarship. There remains an element of choice in chance. For a complete understanding of nuclear brinkmanship, psychology and emotion must be added to the analysis to explain how leaders make decisions under pressure. Human emotions can introduce chance into bargaining in ways that contradict the expectations of the rational cost-benefit assumptions that undergird deterrence theory. Three mechanisms of nuclear brinkmanship—accidents, self-control, and control of others—illustrate how a loss of control over the use of nuclear weapons is not a necessary element of the threat that leaves something to chance. Choice does not have to be eliminated for a risk of catastrophic destruction to remain.

The use of evolutionary models to examine political behavior in international relations has been the subject of much debate, but serious scholarly work has generally been lacking, in part because the causal mechanisms have not always been clearly explicated. An evolutionary psychological framework can correct this deficit and benefit research in at least three major areas of international relations: (1) how political groups such as states are perceived and represented by individuals and groups; (2) how coalitional action is facilitated among states; and (3) sex differences in coalitional behavior. Hypotheses are offered in each of these areas to more clearly demonstrate the psychological mechanisms that are the bridge between evolutionary theory and political behavior in the international system. The social and political landscape of the ancestral environments in which humans evolved strongly suggests that the psychological architecture of humans possesses specialized design for coalitional living that continues to guide behavior in the modern political world. These evolved mechanisms structure human motivation and engagement in areas including leadership and war.

Does the security of women influence the security and behavior of states? Existing evidence linking the situation of women to state-level variables such as economic prosperity and growth, health, and corruption is fairly conclusive. Questions remain, however, concerning the degree to which state security and state security-related behavior is linked to the security of women. The “women and peace” thesis draws upon evolutionary biology/psychology for ultimate causes of this linkage, and sociological theories of social diffusion and psychological theories of social learning for more proximate causal mechanisms. Together, a new data resource—the WomanStats Database—and conventional methodology find a robust, positive relationship between the physical security of women and three measures of state security and peacefulness. In addition, a comparison of this proposition to alternative explanations involving level of democracy, level of economic development, and civilizational identity shows that the physical security of women is a better predictor of state security and peacefulness. Although these results are preliminary, it is still possible to conclude that the security of women must not be overlooked in the study of state security, especially given that the research questions to be raised and the policy initiatives to be considered in the promotion of security will differ markedly if the security of women is seriously considered as a significant influence on state security.