SOCIAL AND ECOLOGICAL FACTORS INFLUENCING COLLECTIVE BEHAVIOR IN GIANT DANIO

A fundamental problem in biology is understanding how and why things group together. Collective behavior is observed on all organismic levels - from cells and slime molds, to swarms of insects, flocks of birds, and schooling fish, and in mammals, including humans. The long-term goal of this research is to understand the functions and mechanisms underlying collective behavior in groups. This dissertation focuses on shoaling (aggregating) fish. Shoaling behaviors in fish confer foraging and anti-predator benefits through social cues from other individuals in the group. However, it is not fully understood what information individuals receive from one another or how this information is propagated throughout a group. It is also not fully understood how the environmental conditions and perturbations affect group behaviors. The specific research objective of this dissertation is to gain a better understanding of how certain social and environmental factors affect group behaviors in fish. I focus on two ecologically relevant decision-making behaviors: (i) rheotaxis, or orientation with respect to a flow, and (ii) startle response, a rapid response to a perceived threat. By integrating behavioral and engineering paradigms, I detail specifics of behavior in giant danio Devario aequipinnatus (McClelland 1893), and numerically analyze mathematical models that may be extended to group behavior for fish in general, and potentially other groups of animals as well. These models that predict behavior data, as well as generate additional, testable hypotheses. One of the primary goals of neuroethology is to study an organism's behavior in the context of evolution and ecology. Here, I focus on studying ecologically relevant behaviors in giant danio in order to better understand collective behavior in fish. The experiments in this dissertation provide contributions to fish ecology, collective behavior, and biologically-inspired robotics.

States' Responding Behavior in Conflict: Asymmetric Response and Strategic Conflict Avoidance

State responses to external threats and aggression are studied with focus on two different rationales: (1) to make credible deterrent threats to avoid being exploited, and (2) to minimize the risk of escalation to unwanted war. Given external aggression, the target state's responding behavior has three possibilities: concession (under-response), reciprocation, and escalation. This study focuses on the first two possibilities and investigates how the strategic nature of crisis interaction can explain the intentional choice of concession or avoidance of retaliation. I build a two-level bargaining model that accounts for the domestic bargaining situation between the leader and the challenger for each state. The model's equilibrium shows that the responding behavior is determined not only by inter-state level variables (e.g. balance of power between two states, or cost of war that each state is supposed to pay), but also the domestic variables of both states. Next, the strategic interaction is rationally explained by the model: as the responding state believes that the initiating state has strong domestic challenges and, hence, the aggression is believed to be initiated for domestic political purposes (a rally-around-the-flag effect), the response tends to decrease. The concession is also predicted if the target state leader has strong bargaining power against her domestic challengers \emph{and} she believes that the initiating leader suffers from weak domestic standing. To test the model's prediction, I conduct a lab experiment and case studies. The experimental result shows that under an incentivized bargaining situation, individual actors are observed to react to hostile action as the model predicts: if the opponent is believed to suffer from internally driven difficulties, the subject will not punish hostile behavior of the other player as severely as she would without such a belief. The experiment also provides supporting evidence for the choice of concession: when the player finds herself in a favorable situation while the other has disadvantages, the player is more likely to make concessions in the controlled dictator game. Two cases are examined to discuss how the model can explain the choice of either reciprocation or concession. From personal interviews and fieldwork in South Korea, I find that South Korea's reciprocating behavior during the 2010 Yeonpyeong Island incident is explained by a combination of `low domestic power of initiating leader (Kim Jong-il)' and `low domestic power of responding leader (Lee Myung-bak).' On the other hand, the case of EC-121 is understood as a non-response or concession outcome. Declassified documents show that Nixon and his key advisors interpreted the attack as a result of North Korea's domestic political instabilities (low domestic power of initiating leader) and that Nixon did not have difficulties at domestic politics during the first few months of his presidency (high domestic power of responding leader).

Criminal Case Processing of Sexual Assaults in Alaska

Discretion plays a role in nearly every facet of the American criminal justice system. It is widely regarded as necessary to do justice but is not without criticisms – especially when it leads to unfavorable or disparate treatment. The role of discretion in sexual assault cases has been particularly scrutinized. Since the majority of sexual assaults do not fit stereotypic beliefs about what constitutes a “real rape” and “genuine victim,” criminal justice officials use their discretion to filter these cases out of the justice system. This study explored this issue by examining two stages of the criminal justice process: the police decision to refer cases for prosecution and the prosecutorial decision to accept referred cases. In doing so, it contributes to this body of literature in three ways. First, it included sexual assault cases that involve Alaska Native victims and suspects. Second, it addressed a gap in the theoretical scholarship by examining the downstream nature of police decision-making. And finally, it examined the formal reasons prosecutors give for charge dispositions. This study found a significant amount of attrition of sexual assault cases as they progressed through the criminal justice system. Moreover, a combination of legally relevant and extralegal factors was found to be important, but not consistently across all types of sexual assaults. Among legal factors, the number of victim injuries was the most consistent predictor. Among extralegal factors, cases that involved Alaska Native suspects had significantly higher odds of case referral and case acceptance compared to white suspects. The effect of suspect race was particularly pronounced in cases with a white victim. Additionally, the findings suggest that not only are Native American defendants more likely to have their cases referred by police, but once referred, they are also more likely to have them accepted for prosecution. Contrary to expectations, victim-suspect relationship, specifically non-stranger assaults, increased the odds of police referral compared to stranger cases. However, the opposite appears to be true for the decision to prosecute cases. Once referred, prosecutors were five times more likely to accept sexual assaults perpetrated by strangers. The implications of these findings are also discussed.