A dual-task paradigm was used to infer the processes critical for episodic memory retrieval by measuring susceptibility to memory interference from different distracting tasks. Research suggests that retrieval interference occurs due to material-specific overlap between concurrent tasks. I tested whether interference could instead arise from processing-specific overlap. In Experiment 1, I took advantage of individual differences in how verbal materials could be represented in those with different language backgrounds. I compared recognition of studied information in English and Chinese speakers under full attention (FA) or under one of two different divided attention (DA) conditions. Participants viewed simplified Chinese characters or English words, and later completed recognition while simultaneously performing distracting tasks requiring phonological (DAP) or visuospatial (DAV) processing of auditorily presented letters. I found an interaction such that Chinese speakers were more susceptible to interference from the visuospatial than phonological distracting task, whereas the reverse pattern was shown in English speakers. These results suggest that interference with memory retrieval is processing-, not material-, specific, as both distracting tasks used the same materials. Next I sought to determine whether processing-specific interference could be observed within the visuo-spatial domain. Accordingly, in Experiments 2 and 3, I examined whether face recognition would be disrupted more by a distracting task requiring configural than featural processing. In Experiment 2, participants studied faces under FA and subsequently performed a recognition task under either FA or each of two different DA conditions in which a distracting face was presented alongside, requiring either a featural (DAF) or configural (DAC) decision. In line with a material-specific account of interference, face memory accuracy was disrupted in both DA conditions relative to the FA condition, although no processing-specific differences in interference were found between the DA conditions, likely because both distracting tasks engaged configural processing. To better isolate the different processing streams in Experiment 3, some faces were inverted to offset configural processing and to engage featural processing. I compared patterns of memory interference when target faces were presented upright (configural) or inverted (featural). I found a crossover interaction: memory for upright faces was worse in the DAC than in the DAF condition, whereas the reverse was true for inverted target faces, supporting a processing-specific account of memory interference. In Experiment 4, I sought to rule out task difficulty as an alternative explanation for the pattern of interference effects. I measured whether each distracting task produced similar slowing, which provides an indirect assessment of resource requirements of a task, on a simultaneously performed auditory tone discrimination task. Results showed that my distracting tasks were not differentially attention demanding, as indexed by similar accuracy rates for tone classification and response times on the tone discrimination task when performed concurrently with each distracting task. Findings suggest that the magnitude of memory interference under DA conditions at retrieval is influenced by material-specificity but that, critically, it also depends on the extent to which the processing demands of the distracting and retrieval tasks overlap. I have shown here that retrieval is not automatic or obligatory as others have suggested, but instead is subject to disruption. This thesis specifies that retrieval interference can occur due to competition for a limited pool of common processing resources across target and distracting tasks. Thus, when trying to recall studied information, one should avoid distracting conditions, especially those that overlap significantly not only with the type of materials tested but also with the mental processes required to retrieve that target information.

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Polarization, defined as the ideological distance between the Democrat and Republican parties in Congress, has increased dramatically in Congress since the 1970s. Research on polarization in the U.S. Congress primarily focuses on the sources of this increase. Relatively little work has been done on the consequences of polarization for Congress? relationship with the president and the passage of legislation. This dissertation corrects this omission by examining the influence of polarization on several key aspects of the legislative process. It examines the impact of polarization on the interaction between Congress and the president, including the president?s strategy in supporting or opposing legislation and the success the president has on bills when he takes a position. It also examines the effect polarization has on the overall passage of legislation. An empirical examination was undertaken using significant bills in Congress over a sixty year time period (1947-2006). The results indicate that the effects of polarization on the legislative process are contingent upon the presence of divided government, defined as times when the president and a majority of members of Congress are from different parties, and the chamber of Congress under examination. As polarization increases, the president is more likely to support legislation and be successful when his party controls Congress, but he opposes more legislation and is less successful as polarization increases under divided government. Legislative gridlock, the inability of Congress to pass important or innovative legislation, tends to decrease in both the House and Senate as polarization increases under unified government. However, as polarization increases under divided government the overall passage of bills into law decreases. The dissertation also offers an improved method for modeling the impact of divided government on gridlock. Prior studies model divided government without regard for whether the president takes a position on a given bill. This study shows that when the president takes a position on a bill under divided government the probability it passes decreases, but the probability of passage increases when the president does not take a position. This finding implies that previous research may underestimate the true effects of divided government on gridlock.

Thesis (Ph. D.)--University of California, San Diego, 2001. / Vita. Includes bibliographical references (leaves 189-206).

Ethnic conflict is a persistent and vexing problem for the world today. The intercommunal violence during these conflicts not only significantly alters the social and spatial geography in these regions for decades, but also frequently involves external actors who magnify the social conflict. It is within the urban areas that the impacts of violence are often most acute and deleterious to the once functioning system. Ethnic conflict transforms many urban areas into “divided cities” in which barricades and armed posts dominate the landscape. With this paradigm of conflict in mind, the overarching purpose of this dissertation is two-fold: 1) to examine how and why certain peaceful societies devolve into intercommunal conflict, and 2) to outline how ethnic conflict ultimately, and often irreparably, transforms an urban area into a “divided city.” In this dissertation, Nicosia, the ethnically divided capital of Cyprus, serves as the primary case study used to illustrate the process of social devolution from ethnic conflict to a militarily fortified urban division. The three main research questions are asked concerning Nicosia’s division. 1) What historic factors contributed to the progression and intensification of the social and spatial cleavages that appear in the urban landscape today? 2) To what extent is the urban divide diagnostic of the overarching ethnic conflict on Cyprus? 3) How is Nicosia’s urban division similar to or different from other “ethnically” divided cities and how might this comparison help further the general understanding of the causes and consequences of these entities? These three questions help frame Nicosia within the context of the larger social conflict on Cyprus as well as assist in developing linkages with other divided cities. As articulated throughout this study, Nicosia is a “model” divided city that typifies how the historically-laden process of ethno-territorial polarization can manifest itself in the physical and social geography of a contested region. In the end, divided cities epitomize the “worst-case-scenario” outcome of ethnic conflict and once the urban divisions take root, they prove exceptionally challenging to remove from the social and physical landscape. / text

This study examined how different background noise conditions affected the spoken language production of people with aphasia (PWA) when performing a story retell task. Participants included 11 adults with mild to moderate aphasia and 11 age- and gender-matched controls. Participants retold stories in a silent baseline and five background noise conditions (conversation, monologue, phone call, cocktail, pink noise). Dependent measures of speech fluency and language production measures (correct information units, lexical errors, lexical diversity, and cohesive utterances) were compared between groups and across conditions. Results reveal that background noise results in significantly lower communication efficiency (i.e., correct information units) for the aphasic group than the control group. PWA also experience background noise costs in relation to speech fluency and lexical production during both conversation and phone call conditions. The control group experience no significant background noise costs. These findings suggest that background noise interferes with discourse more for PWA than neurologically healthy adults.

While previous research has extensively examined the effect of acute stress on cognitive performance, relatively little research has explored the relationship between chronic stress and cognitive performance. The current study aimed to control for current state anxiety to better isolate more chronic stress, when examining the relationship with performance on divided attention tasks. Fifty-four university undergraduates, who self-reported a wide range of perceived chronic stress (10-item Perceived Stress Scale), completed the Trail-Making Test and a dual (auditory and visual) Continuous Performance Test (CPT). Hierarchical regressions were performed to explore cognitive predictors of chronic perceived stress. After covarying for state anxiety (state portion of State-Trait Anxiety Inventory), the most statistically significant predictor (via stepwise entry) was the auditory omission error change score (dual minus single condition), which showed a medium effect size (r = .36). Results have practical safety implications, as the implementation of an efficient and inexpensive measure of self-reported stress may predict future job-related errors in high-stress professions that require divided attention.

This study examined the impact of divided attention tasks on stress using physiologic measures. The divided attention conditions included speech tasks (conversation or procedural discourse) and non-speech computer-based tasks (visuospatial, mathematical, language, data entry, or text editing). Participants included 60 adults divided into two groups of 30 by age. The young adult group ranged in age from 18-30 years and the older adults ranged from 55-82 years. Participants were required to perform the speech task and the non-speech task in isolation as well as a speech task performed concurrently with each of the non-speech tasks. The order of the tasks was randomized between participants to reduce sequencing effects. Physiologic measures include heart rate (HR), heart rate variability (HRV), and galvanic skin response (GSR) using a physiologic measurement system. Statistical analysis revealed age-related physiologic differences during the performance of all tasks. All GSR measures were significantly lower in older adults. Findings also provide insight into the physiologic response to dual-task conditions. The GSR levels were lower in concurrent conditions when compared to the conversation only tasks. Additionally, GSR levels increased during math tasks when compared to visuospatial or language tasks. The results provided insight into the physiologic response to divided attention tasks. The lack of a resting baseline condition and the effects of age on the dependent measures complicated the interpretation of the findings. Further research is needed to better understand the impact of divided attention tasks on a speaker’s physiologic stress response.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The content of this paper is putting forward an idea that applies the software radio technique to the subcarrier demodulation of frequency divided multiplexing telemetry system. Firstly, the article explains the basic thought and application of the software radio. It introduces the main function and the use of the programmable downconverter in HSP50214/ HSP50216. Secondly, it discusses the merit and shortcoming about the method of the subcarrier demodulation of frequency divided multiplexing telemetry system in common use. Finally, the article aims at ± 7.5% proportion bandwidth FM subcarrier channels that in common use in the military standard, introducing HSP50214/HSP50216 programmable downconverter in achievement of design and simulation result. The main problems in the design are discussed and a conclusion obtained.