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 Perceptual Decision Impairments in Obsessive-Compulsive Disorder: State and Trait Symptom Effects and The Role of Working Memory(2020) Kaplan, Claire; Solway, Alec; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Computational models of decision making have identified a relationship between obsessive-compulsive symptomatology and impairments in perceptual evidence accumulation. Past studies have suggested that these impairments in perceptual processing give rise to clusters of OCD symptoms (for example, not effectively “perceiving” that a door is locked or that one’s hands are clean gives rise to compulsive checking or washing). That interpretation has implications for our understanding of the disorder and warrants further testing; one way to investigate that is to determine whether such impairments correlate better with state-level symptoms (i.e., obsessions and compulsions during task performance) or trait-level symptoms (i.e., in general/past week). Using hierarchical drift-diffusion modeling, the current study examines this question in consideration of the alternate possibility that these decision impairments are simply a reflection of off-task processing of active obsessions and compulsions. We also examine whether working memory may mitigate such impairments, in light of prior studies that have associated larger working memory spans with better suppression of distractors and with faster perceptual evidence accumulation. 161 adults completed the random dot-motion task, OSPAN working memory task, and OCD symptom questionnaires online. Participants who reported greater obsessive-compulsive symptoms demonstrated slower evidence accumulation (“drift rate”) in the dot-motion task. These drift rate reductions were better explained by state-level symptom severity than trait-level severity. Working memory span showed a significant negative interaction with state-level symptom score on drift rate, however only for the easiest trials. While the current study does not negate a role of perceptual evidence accumulation deficits in the pathogenesis of OCD, these findings support the possibility that such deficits may also be brought about by active symptoms during task execution. We discuss using impairments in drift rate to approximate attentional bias for off-task symptoms, as this provides a novel computational framework in closer alignment with existing clinical models of OCD.Item Model-Based Support for Information Technology Security Decision Making(2011) Chrun, Danielle; Cukier, Michel; Mosleh, Ali; Reliability Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With the increase in the number and diversity of attacks, a main concern for organizations is to keep their network and systems secure. Existing frameworks to manage Information Technology (IT) security include empirical evaluations, security risk assessments, cost-benefit analyses, and adversary-based evaluations. These techniques are often not easy to apply and their results are usually difficult to convey. This dissertation presents a model to help reasoning about security and to support communication between IT security experts and managers. The model identifies major components of security: threat, user, organization, asset, and emphasizes the human element. Characteristics for each component are determined and cover the attacker's motivations, the user's risk perception, the IT security team expertise, and the depth of protection of the asset. These characteristics are linked through causal influences that can represent positive or negative relationships and be leveraged to rank alternatives through a set of weights. The described formalism allows IT security officers to brainstorm about IT security issues, to evaluate the impacts of alternative solutions on characteristics of security, and ultimately on the level of security, and to communicate their findings to managers. The contributions of this dissertation are three-fold. First, we introduce an approach to develop and validate a model for IT security decision making, given known issues related to this task: difficulties in sharing security data, lack of accepted security metrics, limitation in available information and use of experts. We propose a development and validation process that relies on two sources of information: experts and data. Second, we provide the results of the model development for academic environments. The resulting model is based on extended discussions with the Director of Security at the University of Maryland (UMD), two interviewed experts, fifteen surveyed experts, and empirical data collected at UMD. Finally, we demonstrate the use of the model to justify IT security decisions and present methodological steps towards measuring various characteristics of the model.Item The cognitive dynamics of beliefs: The role of discrepancy, credibility, and involvement on microprocesses of judgment(2004-11-30) Chung, Sungeun; Fink, Edward L; Communication; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation investigates the process of belief change by examining the time course of beliefs. The time course of belief change during judgment provides information about dynamic aspects of the cognitive system, cognitive responses during judgment, and the effect of distal variables on belief change. Several previous studies obtained individual belief trajectories using a computer mouse technique to observe the time course of belief change. Based on characteristics of belief trajectories, this study developed a new framework for their analysis. This framework allows analyses not only of overall but also of micro aspects of belief change during judgment. Hypotheses about the time course of belief changes were developed and tested with four data sets from three previous studies. Total N = 267. This study found the following: (1) Belief change during message receipt reflects the structure and properties of the message; (2) belief change during the post-message phase shows some oscillatory and some damping dynamics; (3) message discrepancy and source credibility have dynamic effects on belief change during judgment. This study generally supports dynamic models of belief change. Methodologically, this study suggests that belief trajectories can provide on-line information about cognitive responses and micro belief changes during judgment.