Correlated Cascades: Compete or Cooperate

In real world social networks, there are multiple cascades which are rarely independent. They usually compete or cooperate with each other. Motivated by the reinforcement theory in sociology we leverage the fact that adoption of a user to any behavior is modeled by the aggregation of behaviors of its neighbors. We use a multidimensional marked Hawkes process to model users product adoption and consequently spread of cascades in social networks. The resulting inference problem is proved to be convex and is solved in parallel by using the barrier method. The advantage of the proposed model is twofold; it models correlated cascades and also learns the latent diffusion network. Experimental results on synthetic and two real datasets gathered from Twitter, URL shortening and music streaming services, illustrate the superior performance of the proposed model over the alternatives

Which way to cooperate

Cooperation in real-world dilemmas takes many forms. We introduce a class of two-player games that permits two distinct ways to cooperate in the repeated game. One way to cooperate is to play cutoff strategies, which rely solely on a player's private value to defection. The second cooperative strategy is to take turns, which relies on publicly available information. Our initial experiments reveal that almost all cooperators adopt cutoff strategies. However, follow-up experiments in which the distribution of values to defection are made more similar show that all cooperators now take turns. Our results offer insight into what form a cooperative norm will take: for mundane tasks or where individuals otherwise have similar payoffs, taking turns is likely; for difficult tasks that differentiate individuals by skill or by preferences, cutoff cooperation will emerge.experimental economics; cooperation; incomplete information; alternating; cutoff strategies; random payoffs

Making Wireless Sensor Network Simulators Cooperate

CONE

The evolution of cooperative norms: evidence from a natural field experiment

We document the establishment and evolution of a cooperative norm among workers using evidence from a natural field experiment on a leading UK farm. Workers are paid according to a relative incentive scheme under which increasing individual effort raises a worker's own pay but imposes a negative externality on the pay of all co-workers, thus creating a rationale for cooperation. As a counterfactual, we analyze worker behavior when workers are paid piece rates and thus have no incentive to cooperate. We find that workers cooperate more as their exposure to the relative incentive scheme increases. We also find that individual and group exposure are substitutes, namely workers who work alongside colleagues with higher exposure cooperate more. Shocks to the workforce in the form of new worker arrivals disrupt cooperation in the short term but are then quickly integrated into the norm. Individual exposure, group exposure, and the arrival of new workers have no effect on productivity when workers and paid piece rates and there is no incentive to cooperate

A Public Dilemma: Cooperation with Large Stakes and a Large Audience

We analyze a large-stakes prisoner's dilemma game played on a TV show. Players cooperate 40% of the time, demonstrating that social preferences are important; however, cooperation is significantly below the 50% threshold that is required for inequity aversion to sustain cooperation. Women cooperate significantly more than men, while players who have "earned" more of the stake cooperate less. A player's promise to cooperate is also a good predictor of his decision. Surprisingly, a player's probability of cooperation is unrelated to the opponent's characteristics or promise. We argue that inequity aversion alone cannot adequately explain these results; reputational concerns in a public setting might be more important.

Unrelated toxin-antitoxin systems cooperate to induce persistence.

Persisters are drug-tolerant bacteria that account for the majority of bacterial infections. They are not mutants, rather, they are slow-growing cells in an otherwise normally growing population. It is known that the frequency of persisters in a population is correlated with the number of toxin-antitoxin systems in the organism. Our previous work provided a mechanistic link between the two by showing how multiple toxin-antitoxin systems, which are present in nearly all bacteria, can cooperate to induce bistable toxin concentrations that result in a heterogeneous population of slow- and fast-growing cells. As such, the slow-growing persisters are a bet-hedging subpopulation maintained under normal conditions. For technical reasons, the model assumed that the kinetic parameters of the various toxin-antitoxin systems in the cell are identical, but experimental data indicate that they differ, sometimes dramatically. Thus, a critical question remains: whether toxin-antitoxin systems from the diverse families, often found together in a cell, with significantly different kinetics, can cooperate in a similar manner. Here, we characterize the interaction of toxin-antitoxin systems from many families that are unrelated and kinetically diverse, and identify the essential determinant for their cooperation. The generic architecture of toxin-antitoxin systems provides the potential for bistability, and our results show that even when they do not exhibit bistability alone, unrelated systems can be coupled by the growth rate to create a strongly bistable, hysteretic switch between normal (fast-growing) and persistent (slow-growing) states. Different combinations of kinetic parameters can produce similar toxic switching thresholds, and the proximity of the thresholds is the primary determinant of bistability. Stochastic fluctuations can spontaneously switch all of the toxin-antitoxin systems in a cell at once. The spontaneous switch creates a heterogeneous population of growing and non-growing cells, typical of persisters, that exist under normal conditions, rather than only as an induced response. The frequency of persisters in the population can be tuned for a particular environmental niche by mixing and matching unrelated systems via mutation, horizontal gene transfer and selection