Theses and Dissertations from UMD
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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
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Item Infant Preferences for Two Properties of Infant-Directed Speech(2010) Segal, Judith Lee; Newman, Rochelle S; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study examined preferences for prosodic and structural properties of infant-directed speech (IDS) in 20 infants, 11 girls and 9 boys, ages 0;11;3 to 0;13;0 (mean age 0;11;28). It was hypothesized that year-old infants would demonstrate a preference for infant-directed structure (IS) over adult-directed structure (AS) regardless of prosody, and that infants would demonstrate no preference for either infant-directed prosody (IP) or adult-directed prosody (AP) regardless of structure. Listening times to passages were compared across infants for four conditions: IS/IP; IS/AP; AS/IP; AS/AP. Results indicate a non-significant but noticeable trend toward a preference for infant-directed structure. In addition, weak correlations were found between vocabulary size and strength of preference for adult-directed prosody, and between age and strength of preference for adult-directed prosody. A non-significant but noticeable interaction was found between prosody and structure and vocabulary. Overall, infants appear to prefer listening to infant-directed structure to adult-directed structure; more advanced language learners show a stronger preference for adult-directed prosody than do their less advanced age-mates; older infants show a stronger preference for adult-directed prosody than do younger infants; and preference for infant-directed structure (but not infant-directed prosody) depends on vocabulary level.Item The Influence of Inhibited Expression of Anger, Perceived Control by Partner, and Withdrawal Cognitions on the Association between Conflict and Relationship Dissolution(2010) Jimerson, Kirsten Elizabeth; Epstein, Dr. Norman; Family Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although there has been a large amount of attention on partners' behavior during conflict and its connection with relationship dissolution, little is known about the individuals' internal experiences during conflict that are associated with relationship instability. The current study investigated whether three internal experiences, the suppression of anger, perceived control by partner, and thoughts about withdrawal, play roles in the relation between conflict and dissolution of couple relationships. The study used assessment data from 69 couples who sought therapy at an outpatient therapy clinic, serving an ethnically and socio-economically diverse population. Analyses tested the main effects of the internal experience variables and their interactions with level of relationship conflict as predictors of steps taken toward relationship dissolution. Findings indicated that the internal experience variables did not play the anticipated moderating role, but they were found to be partial mediators in the relation between conflict and relationship dissolution.Item Parenting Style as a Moderator between Maternal Trauma Symptoms and Child Psychological Distress(2010) Cook, Emily; Leslie, Leigh A; Family Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Current research suggests parents who experience symptoms of trauma transfer distress to their children. The purpose of this study was to understand the possible moderating effect of mothers' parenting style on this relationship. The level of maternal trauma, use of parenting styles, and child psychological distress was examined for a clinical sample (n=113) of mother and child dyads. Results indicated that mothers who experience high levels of trauma symptoms are more likely to parent using authoritarian or permissive behaviors. Mothers experiencing high levels of trauma symptoms who parent with a high use of authoritarian behaviors have children who experience more depression than those whose mothers use fewer authoritarian behaviors. However, mothers experiencing high levels of trauma symptoms who parent with a high use of permissive behaviors have children who experience less depression than those whose mothers use fewer permissive behaviors. The empirical and clinical implications of these findings are discussed.Item Effects of Group Status and Cognitive Appraisal Prime on Integrative Complexity in a Decision Making Context(2009) Van Allen, Katherine Lynn; Stangor, Charles; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Integrative complexity has been shown to influence information-processing and decision-making in different social situations. The present research assessed the effects of group status and cognitive appraisal prime on complexity in a group decision-making context. Experiment 1 assessed group status effects, and Experiment 2 tested whether priming threat or challenge would moderate those effects. Both experiments found that minority members showed greater complexity than majority members. Experiment 2 found that appraisal prime moderated the relationship between status and complexity. Minority members receiving the threat prime were the most complex, while majority members in the threat and control conditions were the least complex. The mediating roles of cognitive appraisal, anxiety, and coping expectancy were assessed, but none were found to be significant mediators of complexity.Item Grammatical Gender Representation and Processing in Advanced Second Language Learners of French(2009) Vatz, Karen L.; DeKeyser, Robert; Michael, Erica B; Second Language Acquisition and Application; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)One of the most difficult challenges of learning French as a foreign language is mastering the gender system. Although there are theories that account for how French native speakers (NSs) master their gender system, it is not fully understood why second language (L2) learners are unable to do the same. The goal of the present study was to investigate this difference in ability between French NSs and non-native speakers (NNSs), specifically, how L2 learners of French store grammatical gender knowledge, and how their storage system relates to processing of grammatical gender in terms of the ability to realize accurate gender agreement throughout a sentence. First, a gender priming task investigated whether advanced L2 learners have developed a gender-nodal system in which gender information is stored as an inherent property of a noun. Second, an online grammaticality judgment task addressed L2 learners' gender agreement ability during processing, while taking into account (a) the role of gender cues available to the participant, and (b) non-linguistic processing constraints such as working memory (WM) through manipulating the distance of an adjective from the noun with which it must agree. In order to investigate the role of a learner's native language (L1) in gender representation and processing, participants included learners of French from three L1 groups: Spanish, whose gender system is congruent to that of French; Dutch, whose gender system is incongruent to that of French; and English, whose gender system is minimal, relative to French. A group of NS controls also participated. Results from the gender priming task indicate that the NNSs in the current study have not developed a native-like gender-nodal system, regardless of L1-L2 gender-system similarity. At-chance accuracy on the grammaticality judgment task indicates L2 gender agreement is far from native-like, even for advanced learners. Whereas the presence of gender cues was beneficial, neither WM nor L1-L2 similarity facilitated performance. The results from this study confirm previous findings on the difficulty of L2 gender agreement, and shed light on the nature of L2 gender representation as a possible explanation for this processing difficulty.Item SUBJECTIVE INTEGRATION OF PROBABILISTIC INFORMATION FROM DESCRIPTION AND FROM EXPERIENCE(2009) Shlomi, Yaron; Wallsten, Thomas S.; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Subjective integration of probabilistic information obtained via description and experience underlies potentially consequential judgments and choices. However, little is known about the quality of the integration and the underlying processes. I contribute to filling this gap by investigating judgments informed by integrating probabilistic information from the two sources. Building on existing information integration frameworks (e.g., N. Anderson, 1971), I develop and subsequently test computational models that represent the integration process. Participants in three experiments estimated the percentage of red balls in a bag containing red and blue balls based on two samples drawn from the bag. They experienced one sample by observing a sequence of draws and received a description of the other sample in terms of summary statistics. Subjective integration was more sensitive to information obtained via experience than via description in a manner that depended on the extremity of the experienced sample relative to the described one. Experiment 1 showed that experience preceding description leads to integration that is less biased towards experience than the reverse presentation sequence. Following this result, Experiment 2 examined the effect of memory-retrieval demands on the quality of the integration. Specifically, we manipulated the presence or absence of description- and experience- based decision aids that eliminate the need to retrieve source-specific information. The results show that the experience aid increased the bias, while the description aid had no interpretable effect. Experiment 3 investigated the effect of the numerical format of the description (percentage vs. frequency). When description was provided in the frequency format, the judgments were unbiased and the leading model suggested that the two sources are psychologically equivalent. However, when the description was provided in the percentage format, the leading model implied a tradeoff between the two sources. Finally, participants in Experiment 3 also rated how much they trusted the source of the description. The participants' ratings were correlated with how they used the description and with the quality of their judgments. The findings have implications for interpreting the description-experience gap in risky choice, for information integration models, and for understanding the role of format on the use of information from external sources. In addition, the methods developed here can be applied broadly to study how people integrate information from different sources or in different formats.Item A Predictive Model of Nuclear Power Plant Crew Decision-Making and Performance in a Dynamic Simulation Environment(2009) Coyne, Kevin; Mosleh, Ali; Reliability Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The safe operation of complex systems such as nuclear power plants requires close coordination between the human operators and plant systems. In order to maintain an adequate level of safety following an accident or other off-normal event, the operators often are called upon to perform complex tasks during dynamic situations with incomplete information. The safety of such complex systems can be greatly improved if the conditions that could lead operators to make poor decisions and commit erroneous actions during these situations can be predicted and mitigated. The primary goal of this research project was the development and validation of a cognitive model capable of simulating nuclear plant operator decision-making during accident conditions. Dynamic probabilistic risk assessment methods can improve the prediction of human error events by providing rich contextual information and an explicit consideration of feedback arising from man-machine interactions. The Accident Dynamics Simulator paired with the Information, Decision, and Action in a Crew context cognitive model (ADS-IDAC) shows promise for predicting situational contexts that might lead to human error events, particularly knowledge driven errors of commission. ADS-IDAC generates a discrete dynamic event tree (DDET) by applying simple branching rules that reflect variations in crew responses to plant events and system status changes. Branches can be generated to simulate slow or fast procedure execution speed, skipping of procedure steps, reliance on memorized information, activation of mental beliefs, variations in control inputs, and equipment failures. Complex operator mental models of plant behavior that guide crew actions can be represented within the ADS-IDAC mental belief framework and used to identify situational contexts that may lead to human error events. This research increased the capabilities of ADS-IDAC in several key areas. The ADS-IDAC computer code was improved to support additional branching events and provide a better representation of the IDAC cognitive model. An operator decision-making engine capable of responding to dynamic changes in situational context was implemented. The IDAC human performance model was fully integrated with a detailed nuclear plant model in order to realistically simulate plant accident scenarios. Finally, the improved ADS-IDAC model was calibrated, validated, and updated using actual nuclear plant crew performance data. This research led to the following general conclusions: (1) A relatively small number of branching rules are capable of efficiently capturing a wide spectrum of crew-to-crew variabilities. (2) Compared to traditional static risk assessment methods, ADS-IDAC can provide a more realistic and integrated assessment of human error events by directly determining the effect of operator behaviors on plant thermal hydraulic parameters. (3) The ADS-IDAC approach provides an efficient framework for capturing actual operator performance data such as timing of operator actions, mental models, and decision-making activities.Item On The Way To Linguistic Representation: Neuromagnetic Evidence of Early Auditory Abstraction in the Perception of Speech and Pitch(2009) Monahan, Philip Joseph; Idsardi, William J; Poeppel, David E; Linguistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The goal of this dissertation is to show that even at the earliest (non-invasive) recordable stages of auditory cortical processing, we find evidence that cortex is calculating abstract representations from the acoustic signal. Looking across two distinct domains (inferential pitch perception and vowel normalization), I present evidence demonstrating that the M100, an automatic evoked neuromagnetic component that localizes to primary auditory cortex is sensitive to abstract computations. The M100 typically responds to physical properties of the stimulus in auditory and speech perception and integrates only over the first 25 to 40 ms of stimulus onset, providing a reliable dependent measure that allows us to tap into early stages of auditory cortical processing. In Chapter 2, I briefly present the episodicist position on speech perception and discuss research indicating that the strongest episodicist position is untenable. I then review findings from the mismatch negativity literature, where proposals have been made that the MMN allows access into linguistic representations supported by auditory cortex. Finally, I conclude the Chapter with a discussion of the previous findings on the M100/N1. In Chapter 3, I present neuromagnetic data showing that the re-sponse properties of the M100 are sensitive to the missing fundamental component using well-controlled stimuli. These findings suggest that listeners are reconstructing the inferred pitch by 100 ms after stimulus onset. In Chapter 4, I propose a novel formant ratio algorithm in which the third formant (F3) is the normalizing factor. The goal of formant ratio proposals is to provide an explicit algorithm that successfully "eliminates" speaker-dependent acoustic variation of auditory vowel tokens. Results from two MEG experiments suggest that auditory cortex is sensitive to formant ratios and that the perceptual system shows heightened sensitivity to tokens located in more densely populated regions of the vowel space. In Chapter 5, I report MEG results that suggest early auditory cortical processing is sensitive to violations of a phonological constraint on sound sequencing, suggesting that listeners make highly specific, knowledge-based predictions about rather abstract anticipated properties of the upcoming speech signal and violations of these predictions are evident in early cortical processing.Item The Dynamics of Variability in Introductory Physics Students' Thinking: Examples from Kinematics(2009) Frank, Brian Wallace; Scherr, Rachel E; Hammer, David; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Physics education research has long emphasized the need for physics instruction to address students' existing intuitions about the physical world as an integral part of learning physics. Researchers, however, have not reached a consensus-view concerning the nature of this intuitive knowledge or the specific role that it does (or might) play in physics learning. While many early characterizations of student misconceptions cast students' intuitive thinking as largely static, unitary in structure, and counter-productive for the purpose of learning correct physics, much of contemporary research supports a conceptualization of intuitive thought as dynamic, manifold in structure, and generative in the development of expertise. This dissertation contributes to ongoing inquiry into the nature of students' intuitive thought and its role in learning physics through the pursuit of dynamic systems characterizations of student reasoning, with a particular focus on how students settle into and shift among multiple patterns of reasoning about motion. In one thread of this research, simple experimental designs are used to demonstrate how individual students can be predictably biased toward and away from different ways of thinking about the same physical situation when specific parameters of questions posed to students are varied. I qualitatively model students' thinking in terms of the activations and interactions among fine-grained intuitive knowledge and static features of the context. In a second thread of this research, case studies of more dynamic shifts in students' conceptual reasoning are developed from videos of student discussions during collaborative classroom activities. These show multiple local stabilities of students' thinking as well, with evidence of group-level dynamics shifting on the time scale of minutes. This work contributes to existing research paradigms that aim to characterize student thinking in physics education in two important ways: (1) through the use of methods that allow for forms of empirical accountability that connect descriptive models of student thinking to experimental data, and (2) through the theoretical development of explanatory mechanisms that account for patterns in students' reasoning at multiple levels of analysis.Item Caffeine Abstinence during the Menstrual Cycle: An Evaluation of Mood, Somatic, Cognitive, and Psychomotor Effects of Withdrawal(2008) Vo, Hoa Thi; Smith, Barry D; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of the present study was to extend our understanding of caffeine withdrawal symptoms and of potentially differing symptom patterns across phases of the menstrual cycle. Forty-eight moderate habitual caffeine consumers, age 18 to 25 years, were recruited from the University of Maryland. Exclusion criteria included current or past psychiatric conditions (within six months) and premenstrual syndrome (PMS). In addition to daily diaries (including the caffeine intake survey, premenstrual syndrome questionnaires, LH surge test, and the caffeine withdrawal checklist), the effect of caffeine abstinence on psychomotor tasks was assessed during the follicular (around day 5 of the cycle) and luteal phases (approximately 4 days after the LH surge) of the menstrual cycle. Data analyses focused on withdrawal symptom ratings and psychomotor performance one day during the follicular phase and one day during the luteal phase of the cycle after 24 hours of caffeine abstinence. A series of repeated measures ANOVAs were used to assess caffeine withdrawal effects and differences in these effects between the follicular and luteal phases. Results confirmed the presence of certain withdrawal symptoms, but did not provide support for phase-differentiated effects of self-reported withdrawal symptoms or of psychomotor and cognitive performance differentials across the menstrual cycle. However, withdrawal, as a result of caffeine abstinence, did impact self-report symptom ratings during select days of abstinence, as compared with days of non-abstinence, during the both the follicular and the luteal phase. The present study is the first multi-method study to examine the effects of caffeine abstinence on habitual consumers across the menstrual cycle.