Theses and Dissertations from UMD
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Item The emergence of symbolic norms(2023) Pan, Xinyue; Gelfand, Michele J.; Nau, Dana S.; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Human groups are experts in developing and maintaining social norms. Many social norms have clear practical functions, such as regulating competition or facilitating coordination. Some other norms, however, have arbitrary functions and limited direct material consequences for the self or the group, but are nevertheless enforced. I define such norms as symbolic norms. Symbolic norms are prevalent across human societies. Given the discrepancy between the social importance and the functional opacity of these norms, it is important to understand how a seemingly neutral behavior can emerge as a symbolic norm and be adopted by the population. In this dissertation, I argue that a neutral behavior is more likely to evolve as a symbolic norm when it shows statistical correlation with a practical behavior on the population level. I call this the norm spillover effect. The norm spillover effect predicts that if, on the population level, followers of a practically beneficial norm happen to conduct a certain neutral behavior more often than practical norm violators, the social norm will spill over from the practical domain to the neutral domain. Thus, people will adopt and enforce that neutral behavior, and a symbolic norm will emerge. This dissertation uses agent-based models and an empirical experiment to test the norm spillover effect across two levels of analyses. First, agent-based models are used to test the evolutionary force behind the norm spillover effect on the population level. I argue that the statistical correlation between a practical and a neutral behavior creates an ecology that fosters symbolic norm following and enforcement. Second, an empirical experiment is conducted to examine the psychology of the norm spillover effect on the individual level. I argue that the perceived correlation between a practical and a neutral behavior increases the perceived direct function of and the pressure to conform to the symbolic norm.Item U.S. NUCLEAR ENERGY COOPERATION AND PARTNER COUNTRY NONPROLIFERATION: CASE STUDIES FROM EAST ASIA(2022) Siegel, Jonas Elliott; Gallagher, Nancy; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)U.S. policy makers are promoting U.S. civilian nuclear exports as a means of influencing the nonproliferation policies of foreign governments and of achieving U.S. nuclear nonproliferation objectives. This approach to nonproliferation policy making assumes that engaging in international civilian nuclear cooperation is effective at influencing partner country nonproliferation commitments and behavior, and that it is more efficient and effective than other means of achieving similar nonproliferation goals. This dissertation tests these assumptions by examining the historical nonproliferation impact of U.S. civilian nuclear cooperation on three countries who sought to build civilian nuclear power programs with U.S. assistance: Japan, South Korea, and China. These case studies place U.S. civilian nuclear energy cooperation in the context of broader U.S. security and economic relations with these countries, and provide a nuanced understanding of each countries’ rationales for engaging in nuclear cooperation and nonproliferation in the first place. This dissertation also develops a novel approach to measuring nonproliferation that focuses on a country’s nonproliferation behavior in addition to its policy commitments. It also assesses whether particular types and stages of U.S. civilian nuclear cooperation and/or the characteristics of U.S. partners affect the strength and direction of the relationship between nuclear cooperation and nonproliferation. In examining multiple periods of U.S. civilian nuclear cooperation with each country, this dissertation finds that U.S. civilian nuclear energy cooperation—and more specifically, the process of negotiating and renegotiating the terms of nuclear cooperation—can be effective ways to induce U.S. partner countries to adopt nonproliferation commitments. This is particularly the case when U.S. partners are energy insecure and rely predominantly (or exclusively) on foreign assistance in developing their civilian nuclear programs. U.S. civilian nuclear cooperation coupled with U.S. security cooperation (including nuclear security guarantees) can often win U.S. policy makers additional, detailed nonproliferation commitments from partner countries that are not possible with security cooperation alone. The dissertation also finds that U.S. civilian nuclear cooperation has limited impact on the nonproliferation behaviors of U.S. partners in the short run once they formally make nonproliferation commitments. In all three cases, U.S. partners’ nonproliferation behaviors improve over time, but these improvements are due to the partners’ internalization of global nonproliferation norms and partners’ development of their own nonproliferation logic, rather than the influence of U.S. civilian nuclear cooperation. Frequent changes in U.S. nonproliferation preferences and, in particular, the divergence of U.S. nonproliferation preferences from the baseline tenets of the multilateral nonproliferation regime make it costly and difficult for the United States to maintain influence on partner countries’ nonproliferation commitments and behaviors over time with civilian nuclear cooperation. On account of these findings, this dissertation argues that in many situations, U.S. civilian nuclear cooperation is not an effective means of achieving U.S. nonproliferation objectives. Compared to other possible courses of action, such as reinforcing multilateral nonproliferation agreements and norms, or engaging in nonproliferation capacity building, U.S. civilian nuclear cooperation is also not efficient in achieving U.S. aims. Should U.S. policy makers continue to pursue civilian nuclear cooperation as a means of achieving U.S. nonproliferation objectives, they should be aware of the conditions that are most conducive to U.S. nonproliferation influence, and they should be realistic about the challenges and costs associated with maintaining that influence over time.Item The role of gossip in the evolution of cooperation(2021) Pan, Xinyue; Gelfand, Michele J.; Nau, Dana S.; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The prevalence of cooperation in human societies is astonishing. Scholars from many disciplines have been sought to understand why it evolves. Some studies have indicated that gossip may play an important role in the evolution of cooperation. However, there has yet to be a systematic attempt to test this hypothesis directly. In this thesis, I developed an evolutionary game theoretic model and examined the role of gossip in the evolution of cooperation as well as the mechanism of the evolution of gossipers. I found that gossip increases reputation accessibility and makes the utilization of reputation information effective and necessary. The utilization of reputation information not only leads to more cooperation but also motivates individuals to manage their reputation by cooperating more with gossipers. As a result, gossipers gain an advantage over non-gossipers, and this leads to the evolution of gossipers. I also examined the factors that moderate these results.Item Mindreading for Cooperation: a moderately minimalist approach(2019) Schoenher, Julius; Carruthers, Peter; Philosophy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation puts forth a series of arguments about the extent to which human cooperative interaction is fundamentally shaped by mindreading; i.e. the capability to reason about the psychological causes (e.g. intentions, beliefs, goals) of behavior. The introduction to this dissertation discusses the broad philosophical underpinnings that lay the foundations for more specific philosophical issues under discussion in subsequent chapters. In chapter two, I argue that a thorough interpretation of the relevant empirical evidence suggests that mindreading is fast, effortlessly deployed, and operative sub-personally. For this reason, mindreading is principally well-suited to enable most everyday cooperative interactions. In the appendix, I (in collaboration with Evan Westra ) elaborate on this picture, arguing that the cognitive mechanisms operative in social interactions are, in all relevant respects, similar to those operative in non-interactive situations. While chapter two and the appendix defend the idea that the cognitive faculties responsible for mindreading are fit to enable cooperative interactions, chapters three and four take this perspective for granted and discusses whether human cooperation is crucially dependent on a form of reciprocal attribution of mental states that is often labeled common knowledge. In chapter three of this dissertation I address, and reject, the oft defended idea that truly performing an action together with others requires that all parties commonly know their intended goals. I argue that this view is fundamentally mistaken. Successfully acting together with others often requires not knowing these goals. Chapter four explores reciprocal belief attribution in the context of coordination problems. Humans often coordinate their actions by replicating successful past choices; they reason based on precedent. Philosophers have often claimed that solving coordination problems by relying on precedent presupposes common knowledge that all parties rely on precedent in trying to coordinate their actions. Chapter four points out that this assumption is erroneous: Coordinating behavior on the basis of precedent is broadly incompatible with any higher-order knowledge (or beliefs) about the other agents’ choices.Item COOPERATION AND SOCIAL BONDS IN COMMON VAMPIRE BATS(2015) Carter, Gerald; Wilkinson, Gerald S; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Regurgitated food sharing among vampire bats is a classic textbook example of reciprocity ("reciprocal altruism"). But many authors have contested both the notion that reciprocity explains vampire bat food-sharing and the importance of reciprocity more generally. In Chapter 1, I review the literature on evolutionary explanations of cooperation. I show why reciprocity was once considered important but is now considered rare: overly literal translations of game theory strategies have resulted in problems for both defining and testing reciprocity. In Chapter 2, I examine the relative roles of social predictors of food-sharing decisions by common vampire bats (Desmodus rotundus) under controlled conditions of mixed relatedness and equal familiarity by fasting 20 individuals in 48 trials over two years. The food-sharing network was consistent, symmetrical, and correlated with mutual allogrooming. Non- kin food-sharing patterns were not consistent with harassment or byproduct explanations. I next attempted to manipulate food-sharing decisions in two ways. In Chapter 3, I administered intranasal oxytocin to test for effects on allogrooming and food sharing. I observed that inhaled oxytocin slightly increased the magnitude of food donations within dyads, and the amount of female allogrooming within and across all partners, without increasing number of partners. In Chapter 4, I assessed contingency of food-sharing in 7 female dyads (including four pairs of mother and adult daughters) with prior histories of sharing. To test for evidence of partner switching, I measured dyadic levels of food sharing before and after a treatment period where I prevented dyadic sharing (each bat could only be fed by others). A bat's sharing network size predicted how much food it received in the experiment. When primary donors were excluded, subjects did not compensate with donations from other partners. Yet, food-sharing bonds appeared unaffected by the non-sharing treatment. In particular, close maternal kin were clearly not enforcing cooperation using strict contingency. I argue that any contingencies within such bonds are likely to involve multiple services and long timescales, making them difficult to detect. Simple and dyadic `tit-for-tat' models are unlikely to predict cooperative decisions by vampire bats or other species with stable, mixed kinship, social bonds.Item Capacity Bounds For Multi-User Channels With Feedback, Relaying and Cooperation(2010) Tandon, Ravi; Ulukus, Sennur; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent developments in communications are driven by the goal of achieving high data rates for wireless communication devices. To achieve this goal, several new phenomena need to be investigated from an information theoretic perspective. In this dissertation, we focus on three of these phenomena: feedback, relaying and cooperation. We study these phenomena for various multi-user channels from an information theoretic point of view. One of the aims of this dissertation is to study the performance limits of simple wireless networks, for various forms of feedback and cooperation. Consider an uplink communication system, where several users wish to transmit independent data to a base-station. If the base-station can send feedback to the users, one can expect to achieve higher data-rates since feedback can enable cooperation among the users. Another way to improve data-rates is to make use of the broadcast nature of the wireless medium, where the users can overhear each other's transmitted signals. This particular phenomenon has garnered much attention lately, where users can help in increasing each other's data-rates by utilizing the overheard information. This overheard information can be interpreted as a generalized form of feedback. To take these several models of feedback and cooperation into account, we study the two-user multiple access channel and the two-user interference channel with generalized feedback. For all these models, we derive new outer bounds on their capacity regions. We specialize these results for noiseless feedback, additive noisy feedback and user-cooperation models and show strict improvements over the previously known bounds. Next, we study state-dependent channels with rate-limited state information to the receiver or to the transmitter. This state-dependent channel models a practical situation of fading, where the fade information is partially available to the receiver or to the transmitter. We derive new bounds on the capacity of such channels and obtain capacity results for a special sub-class of such channels. We study the effect of relaying by considering the parallel relay network, also known as the diamond channel. The parallel relay network considered in this dissertation comprises of a cascade of a general broadcast channel to the relays and an orthogonal multiple access channel from the relays to the receiver. We characterize the capacity of the diamond channel, when the broadcast channel is deterministic. We also study the diamond channel with partially separated relays, and obtain capacity results when the broadcast channel is either semi-deterministic or physically degraded. Our results also demonstrate that feedback to the relays can strictly increase the capacity of the diamond channel. In several sensor network applications, distributed lossless compression of sources is of considerable interest. The presence of adversarial nodes makes it important to design compression schemes which serve the dual purpose of reliable source transmission to legitimate nodes while minimizing the information leakage to the adversarial nodes. Taking this constraint into account, we consider information theoretic secrecy, where our aim is to limit the information leakage to the eavesdropper. For this purpose, we study a secure source coding problem with coded side information from a helper to the legitimate user. We derive the rate-equivocation region for this problem. We show that the helper node serves the dual purpose of reducing the source transmission rate and increasing the uncertainty at the adversarial node. Next, we considered two different secure source coding models and provide the corresponding rate-equivocation regions.Item Synthesis of Strategies for Non-Zero-Sum Repeated Games(2008-08-21) Au, Tsz-Chiu; Nau, Dana; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There are numerous applications that involve two or more self-interested autonomous agents that repeatedly interact with each other in order to achieve a goal or maximize their utilities. This dissertation focuses on the problem of how to identify and exploit useful structures in agents' behavior for the construction of good strategies for agents in multi-agent environments, particularly non-zero-sum repeated games. This dissertation makes four contributions to the study of this problem. First, this thesis describes a way to take a set of interaction traces produced by different pairs of players in a two-player repeated game, and then find the best way to combine them into a strategy. The strategy can then be incorporated into an existing agent, as an enhancement of the agent's original strategy. In cross-validated experiments involving 126 agents for the Iterated Prisoner's Dilemma, Iterated Chicken Game, and Iterated Battle of the Sexes, my technique was able to make improvement to the performance of nearly all of the agents. Second, this thesis investigates the issue of uncertainty about goals when a goal-based agent situated in a nondeterministic environment. The results of this investigation include the necessary and sufficiency conditions for such guarantee, and an algorithm for synthesizing a strategy from interaction traces that maximizes the probability of success of an agent even when no strategy can assure the success of the agent. Third, this thesis introduces a technique, Symbolic Noise Detection (SND), for detecting noise (i.e., mistakes or miscommunications) among agents in repeated games. The idea is that if we can build a model of the other agent's behavior, we can use this model to detect and correct actions that have been affected by noise. In the 20th Anniversary Iterated Prisoner's Dilemma competition, the SND agent placed third in the "noise" category, and was the best performer among programs that had no "slave" programs feeding points to them. Fourth, the thesis presents a generalization of SND that can be wrapped around any existing strategy. Finally, the thesis includes a general framework for synthesizing strategies from experience for repeated games in both noisy and noisy-free environments.Item Robust Network Trust Establishment for Collaborative Applications and Protocols(2007-05-07) Theodorakopoulos, Georgios Efthymios; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In networks without centralized control (e.g. ad-hoc or peer-to-peer networks) the users cannot always be assumed to follow the protocol that they are supposed to. They will cooperate in the operation of the network to the extent that they achieve their own personal objectives. The decision to cooperate depends on the trust relations that users develop for each other through repeated interactions. Users who have not interacted directly with each other can use direct trust relations, generated by others, in a transitive way as a type of recommendation. Network operation and trust generation can be affected by malicious users, who have different objectives, and against whom any proposed solution needs to be robust. We model the generation of trust relations using repeated games of incomplete information to capture the repetitive operation of the network, as well as the lack of information of each user about the others' objectives. We find equilibria that provide solutions for the legitimate users against which the malicious users cannot improve their gains. The transitive computation of trust is modeled using semiring operators. This algebraic model allows us to generalize various trust computation algorithms. More importantly, we find the maximum distortion that a malicious user can cause to the trust computation by changing the reported trust value of a trust relation.Item Parent-Offspring Recognition and Alloparental Care in Greater Spear-Nosed Bats(2005-12-02) Bohn, Kirsten M; Wilkinson, Gerald S; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Selection should insure that parents selectively care for their own offspring. Thus, alloparental care, or care of other's young, seems counterintuitive to evolutionary theory. Alloparental care is often attributed to: 1) mistaken identity, when individuals confuse their young with others or 2) cooperation, when the alloparent and young mutually benefit. Cooperative care, in turn, is often explained by kin selection, where animals selectively care for genetic relatives. In this dissertation, I examine these alternative explanations for alloparental care in greater spear-nosed bats (Phyllostomus hastatus). In this species, females form stable social groups of relatively unrelated individuals. Females give birth once a year to nonvolant pups that frequently fall from roost sites in cave ceilings and likely perish unless retrieved by an adult. In this context, pups emit vocalizations, termed isolation calls, that are used in parent-offspring recognition. I examine parent-offspring recognition in P. hastatus by examining isolation call variability and both detection and perception of isolation calls by adults. I found that pups emit individually distinctive calls but that pups from the same social group have more similar calls than pups from different social groups. Psychoacoustic experiments in the laboratory showed that greatest hearing sensitivity and frequency selectivity in adult P. hastatus is at the fundamental frequency of isolation calls. I found that this is a common phenomenon in bats using comparative phylogenetic methods. Finally, using psychoacoustic experiments I demonstrated that P. hastatus females could discriminate between pups' isolation calls regardless of the pups' social groups. Next, I examine parental care in the natural habitat of P. hastatus. I found that females respond more frequently and spend more time visiting group mates' pups than non-group mates pups, even though many of these females are not missing pups of their own. These results, combined with the results from psychoacoustic studies, indicate that mistaken identity cannot explain this visiting behavior. By visiting group mates' pups, females protect them from non-group mates who attack and sometimes kill them. However, kin selection cannot explain this behavior because females are unrelated to group mates' pups that they visit.