Bargaining over power: when do shifts in power lead to war?

Students of international relations have long argued that large and rapid shifts in relative power can lead to war. But then why does the rising state not alleviate the concerns of the declining one by reducing its expected future power, so that a commitment problem never emerges? For example, states often limit their ability to launch preemptive attacks by creating demilitarized zones, or they abandon armament programs to avoid preventive wars. In a model of complete information, I show that shifts in power never lead to war when countries can negotiate over the determinants of their power. If war occurs, then, it must be that negotiations over power are impossible or too costly. I then show how third parties, domestic politics, and problems of fungibility can increase the costs of such negotiations, and hence lead to war, even under complete informatio

How Wealth Accumulation Can Promote Cooperation

Explaining the emergence and stability of cooperation has been a central challenge in biology, economics and sociology. Unfortunately, the mechanisms known to promote it either require elaborate strategies or hold only under restrictive conditions. Here, we report the emergence, survival, and frequent domination of cooperation in a world characterized by selfishness and a strong temptation to defect, when individuals can accumulate wealth. In particular, we study games with local adaptation such as the prisoner's dilemma, to which we add heterogeneity in payoffs. In our model, agents accumulate wealth and invest some of it in their interactions. The larger the investment, the more can potentially be gained or lost, so that present gains affect future payoffs. We find that cooperation survives for a far wider range of parameters than without wealth accumulation and, even more strikingly, that it often dominates defection. This is in stark contrast to the traditional evolutionary prisoner's dilemma in particular, in which cooperation rarely survives and almost never thrives. With the inequality we introduce, on the contrary, cooperators do better than defectors, even without any strategic behavior or exogenously imposed strategies. These results have important consequences for our understanding of the type of social and economic arrangements that are optimal and efficient

Saving Human Lives: What Complexity Science and Information Systems can Contribute

We discuss models and data of crowd disasters, crime, terrorism, war and disease spreading to show that conventional recipes, such as deterrence strategies, are often not effective and sufficient to contain them. Many common approaches do not provide a good picture of the actual system behavior, because they neglect feedback loops, instabilities and cascade effects. The complex and often counter-intuitive behavior of social systems and their macro-level collective dynamics can be better understood by means of complexity science. We highlight that a suitable system design and management can help to stop undesirable cascade effects and to enable favorable kinds of self-organization in the system. In such a way, complexity science can help to save human lives.Comment: 67 pages, 25 figures; accepted for publication in Journal of Statistical Physics [for related work see http://www.futurict.eu/

Asymptotic <i>proportion</i> of cooperators without and with wealth accumulation.

<p>The contour plot shows the average final proportion of cooperators in the world, as a function of the payoff parameters (horizontal axis) and (vertical axis). (A) In a world in which payoffs are homogenous across agents, the proportion of cooperators is low for any . (B) In an unequal environment, in which the rich can become richer, cooperation is stable for a much larger range of payoff parameters. The top-left quadrant corresponds to the harmony game (HG); the bottom-left ( and ) to the stag-hunt (or ‘assurance’) game (SH); the upper-right quadrant (, ) to the snowdrift (or ‘chicken’) game (SD); and the lower-right quadrant ( and ) corresponds to the prisoner's dilemma (PD) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone.0013471-Roca1" target="_blank">[33]</a>.</p

Asymptotic proportion, domination, and survival of cooperators, when individuals imitate others based on cumulative wealth.

<p>We tested the robustness of our results by using cumulative payoffs instead of the current step's payoff as the basis of adaptation. That is, agents here adapt to the strategy of their most successful neighbor, as measured by the total wealth they have accumulated over time, instead of the payoff they obtained in the previous step. Panel A shows the final proportion of cooperators in the world (compare with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g004" target="_blank">Figure 4</a>). Panel B shows the percentage of runs that end with more than 99% cooperators (compare with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g006" target="_blank">Figure 6</a>). Panel C shows the percentage of runs in which at least 1% of cooperators survive after 1000 steps (compare with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g005" target="_blank">Figure 5</a>). Note that the results basically agree with the ones, when individuals imitate others based on their payoff in the previous time step, rather than their overall wealth, as is the case here (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g004" target="_blank">Figures 4B</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g005" target="_blank">5B</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013471#pone-0013471-g006" target="_blank">6B</a>).</p

Strategies with the highest average score, as a function of the proportion of prejudiced players.

<p>Each individual is given five traits; the proportion of prejudiced (P(5)) players added to the simulation is “% P(5)”, with the remaining population equally split between ALLD and TFT players. For short shadows of the future, ALLD defeats all other strategies. For longer shadows of the future, prejudiced players can beat TFT, but only if the total proportion of prejudiced players in the population remains sufficiently low. In other words, prejudiced strategies perform well against TFT and ALLD, but not against themselves.</p