A modeling framework for adaptive collective defense: crisis response in social-insect colonies.

Living systems, from cells to superorganismic insect colonies, have an organizational boundary between inside and outside and allocate resources to defend it. Whereas the micro-scale dynamics of cell walls can be difficult to study, the adaptive allocation of workers to defense in social-insect colonies is more conspicuous. This is particularly the case for Tetragonisca angustula stingless bees, which combine different defensive mechanisms found across other colonial animals: (1) morphological specialization (distinct soldiers (majors) are produced over weeks); (2) age-based polyethism (young majors transition to guarding tasks over days); and (3) task switching (small workers (minors) replace soldiers within minutes under crisis). To better understand how these timescales of reproduction, development, and behavior integrate to balance defensive demands with other colony needs, we developed a demographic Filippov ODE system to study the effect of these processes on task allocation and colony size. Our results show that colony size peaks at low proportions of majors, but colonies die if minors are too plastic or defensive demands are too high or if there is a high proportion of quickly developing majors. For fast maturation, increasing major production may decrease defenses. This model elucidates the demographic factors constraining collective defense regulation in social insects while also suggesting new explanations for variation in defensive allocation at smaller scales where the mechanisms underlying defensive processes are not easily observable. Moreover, our work helps to establish social insects as model organisms for understanding other systems where the transaction costs for component turnover are nontrivial, as in manufacturing systems and just-in-time supply chains.

Local alliances and rivalries shape near-repeat terror activity of al-Qaeda, ISIS, and insurgents.

We study the spatiotemporal correlation of terrorist attacks by al-Qaeda, the Islamic State of Iraq and Syria (ISIS), and local insurgents, in six geographical areas identified via k-means clustering applied to the Global Terrorism Database. All surveyed organizations exhibit near-repeat activity whereby a prior attack increases the likelihood of a subsequent one by the same group within 20 km and on average 4 (al-Qaeda) to 10 (ISIS) weeks. Near-response activity, whereby an attack by a given organization elicits further attacks from a different one, is found to depend on the adversarial, neutral, or collaborative relationship between the two. When in conflict, local insurgents respond quickly to attacks by global terror groups while global terror groups delay their responses to local insurgents, leading to an asymmetric dynamic. When neutral or allied, attacks by one group enhance the response likelihood of the other, regardless of hierarchy. These trends arise consistently in all clusters for which data are available. Government intervention and spillover effects are also discussed; we find no evidence of outbidding. Understanding the regional dynamics of terrorism may be greatly beneficial in policy making and intervention design.

The Triad of Risk-Related Behaviors (TriRB): A Three-Dimensional Model of Cyber Risk Taking.

OBJECTIVE: We identify three risk-related behaviors in coping with cyber threats-the exposure to risk a person chooses, use of security features, and responses to security indications. The combinations of behaviors that users choose determine how well they cope with threats and the severity of adverse events they experience. BACKGROUND: End users' coping with risks is a major factor in cybersecurity. This behavior results from a combination of risk-related behaviors rather than from a single risk-taking tendency. METHOD: In two experiments, participants played a Tetris-like game, attempting to maximize their gains, while exogenous occasional attacks could diminish earnings. An alerting system provided indications about possible attacks, and participants could take protective actions to limit the losses from attacks. RESULTS: Variables such as the costs of protective actions, reliability of the alerting system, and attack severity affected the three behaviors differently. Also, users dynamically adjusted each of the three risk-related behaviors after gaining experience with the system. CONCLUSION: The results demonstrate that users' risk taking is the complex combination of three behaviors rather than the expression of a general risk-taking tendency. The use of security features, exposure to risk, and responses to security indications reflect long-term strategy, short-term tactical decisions, and immediate maneuvering in coping with risks in dynamic environments. APPLICATION: The results have implications for the analysis of cybersecurity-related decisions and actions as well as for the evaluation and design of systems and targeted interventions in other domains.

A cognitive model of dynamic cooperation with varied interdependency information.

We analyze the dynamics of repeated interaction of two players in the Prisoner's Dilemma (PD) under various levels of interdependency information and propose an instance-based learning cognitive model (IBL-PD) to explain how cooperation emerges over time. Six hypotheses are tested regarding how a player accounts for an opponent's outcomes: the selfish hypothesis suggests ignoring information about the opponent and utilizing only the player's own outcomes; the extreme fairness hypothesis weighs the player's own and the opponent's outcomes equally; the moderate fairness hypothesis weighs the opponent's outcomes less than the player's own outcomes to various extents; the linear increasing hypothesis increasingly weighs the opponent's outcomes at a constant rate with repeated interactions; the hyperbolic discounting hypothesis increasingly and nonlinearly weighs the opponent's outcomes over time; and the dynamic expectations hypothesis dynamically adjusts the weight a player gives to the opponent's outcomes, according to the gap between the expected and the actual outcomes in each interaction. When players lack explicit feedback about their opponent's choices and outcomes, results are consistent with the selfish hypothesis; however, when this information is made explicit, the best predictions result from the dynamic expectations hypothesis.

Attention and search conspicuity of motorcycles as a function of their visual context.

BACKGROUND: Over the years, PTWs' number of accidents have increased dramatically and have accounted for a high percentage of the total traffic fatalities. The majority of those accidents occur in daylight, clear weather, and at light to moderate traffic conditions. The current study included two experiments. The first experiment evaluated the influence of PTW attention conspicuity on the ability of un-alerted viewers to detect it, whereas the second experiment evaluated the PTWs search conspicuity to alerted viewers. The independent variables in both experiments included driving scenarios (urban and inter-urban), PTW rider's outfit (black, white, and reflective) and PTW distance from the viewer. METHOD: 66 students participated in experiment 1. Every participant was presented with a series of pictures and was asked to report all the vehicle types present in each picture. Experiment 2 included 64 participants and incorporated the same pictures as experiment 1. However, in this experiment the participants were instructed to search the pictures for a PTW and to report its presence or absence as soon as they reach a decision. RESULTS: In experiment 1 the detection of a PTW depended on the interaction between its distance from the viewer, the driving scenario and PTW rider's outfit. For an un-alerted viewer when the PTW was distant the different outfit conditions affected its' attention conspicuity. In urban roads, where the background surrounding the PTW was more complex and multi-colored, the reflective and white outfits increased its attention conspicuity compared to the black outfit condition. In contrast, in inter-urban roads, where the background was solely a bright sky, the black outfit provided an advantage for the PTW detectability. In experiment 2, the average PTW detection rate of the alerted viewers was very high and the average reaction time to identify the presence of a PTW was the shortest in the inter-urban environment. Similar to the results of experiment 1, in urban environments the reflective and white clothing provided an advantage to the detection of the PTW, while in the inter-urban environment the black outfit presented an advantage. Comparing the results of the two experiments revealed that at the farthest distance, the increased awareness in the search conspicuity detection rates were three times higher than in the attention conspicuity. CONCLUSIONS: The conspicuity of a PTW can be increased by using an appropriate rider's outfit that distinguishes him/her from the background scenery. Thus, PTW riders can actively increase their conspicuity by taking into account the driving route (crowded urban/inter urban), eventually increasing the probability of being detected by the other road users. In addition, increasing the alertness and expectancy of drivers to the presence of PTWs can increase their search conspicuity.