Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item The Malleability of Cognitive Control and its Effects on Language Skills(2013) Hussey, Erika; Dougherty, Michael R; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cognitive control, or executive function (EF), refers to the mental ability to regulate and adjust behavior across domains in the face of interference, conflict, or new rules. Evidence from psycholinguistics suggests a role for cognitive control in a range of language processing tasks including syntactic ambiguity resolution and verbal fluency. Separate work demonstrates that EF abilities are malleable with extensive practice, such that training improvements transfer across domains to novel tasks that rely on the same underlying EF mechanisms (an effect dubbed 'process-specificity'). In uniting these two growing literatures, this dissertation investigated the (causal) role of cognitive control for language processing through two longitudinal training interventions. In one study, I demonstrated that practicing a battery of cognitive tasks conferred selective benefits on untrained reading tasks requiring syntactic ambiguity resolution. Compared to controls, individuals who responded most to an EF training task exhibited (1) higher accuracy to comprehension questions indexing offline reinterpretation, and (2) faster real-time recovery efforts to resolve among conflicting interpretations. A second experiment extended these findings by addressing the degree to which training on a single EF task was necessary and sufficient to confer transfer to untrained, related language measures. Participants were assigned to practice a single training task that was minimally different from other training groups' tasks in terms of EF demands. By and large, participants who practiced a high-EF training task were exclusive in demonstrating a cross-assessment improvement profile consistent with a process-specific account: Pre/post benefits across a range of ostensibly different linguistic (verbal fluency, syntactic ambiguity resolution) and non-linguistic (Stroop, recognition memory) tasks were observed selectively for conditions with high-EF demands; no benefits were seen for cases when the need for cognitive control was minimized. Together, these findings provide support for the malleability of EF skills and suggest a critical (and perhaps causal) role for domain-general cognitive control in language processing. Further, the present studies indicate that within the right framework, and having appropriate linking hypotheses, cognitive training may be a viable way to improve language use.Item Adaptive Agent Modeling in a Policy Context(2004-12-15) Gulden, Timothy R; Daly, Herman E; Public Affairs; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines the utility of adaptive agent modeling (also referred to as agent-based modeling or individual based modeling) as a tool in public policy research. It uses the adaptive agent technique to produce useful results in three diverse areas. It demonstrates that the adaptive agent framework can be used to extend traditional models of comparative advantage in international trade, showing that the presence of increasing returns to scale in some industries shifts the basis of comparative advantage arguments, making room for industrial policy and the regulation of trade. Next, the dissertation demonstrates that the size distribution of cities within nations, generally thought to approximate the "Zipf" distribution, can be reproduced using a simple agent-based model. This model produces insights into the evolution of the distribution as well as departures from it especially in France and Russia. This understanding of urban dynamics has implications for easing the structural transition of the Russian economy and for designing policies to reduce the size of megacities in the developing world. The dissertation goes on to examine individual level data from the Guatemalan civil war from an adaptive agent modeling perspective. It finds several novel patterns in the data which may serve as benchmarks for adaptive agent modeling efforts and suggests avenues by which existing conflict models might be brought into closer accord with the data. The dissertation concludes that adaptive agent modeling is useful in a policy context because it allows quantitative work to be done while relaxing some of the unrealistic assumptions which are often required to gain analytical traction using traditional methods. The method is found to be particularly useful in situations where path dependence, heterogeneity of actors, bounded rationality, and imperfect information are significant features of the system under examination. The individual based nature of the method is also found to be well suited to assessing distributional impacts of changes in process or policy.