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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.


Ramani, Geetha Balaraman 20 March 2006 (has links)
The effects of setting on cooperative play and problem solving in preschool children were examined. The study investigated whether a cooperative problem-solving setting that was more like informal social play promoted more effective cooperation and problem solving than a setting that was more structured, and whether the benefits of the play-like setting generalized to another problem solving task. The study also examined the development of cooperative problem solving skills across the preschool years. Four- and five-year-old same-age, same-sex dyads were randomly assigned to complete a problem solving building task in a more play-like, flexible, and child-driven setting or in a more structured and adult-driven setting. The older children built more complete, complex structures with a greater number of blocks than younger children. Children in the play-like setting built more complex structures and utilized observational learning more than children in the structured condition, although no significant condition differences emerged for cooperative behavior and communication. Performance differences also carried over into a subsequent joint problem solving task. Across both settings, individual differences in cooperative skills were related to childrens task performance. The results suggest that problem solving skills develop through the preschool years, and that cooperative problem solving in age-appropriate play-like settings is an effective way to promote and investigate both cooperative behavior and cooperative learning in young children.

Do Individuals with Autism Process Categories Differently? The Role of Typicality

Gastgeb, Holly Zajac 20 March 2006 (has links)
A critical cognitive ability that has received relatively little attention in individuals with autism is the ability to form categories. Previous studies of categorization in individuals with autism have found mixed results, some indicating that these individuals have a deficit in categorization and others suggesting that they do not. These studies are limited, however, because they have not closely investigated the role that typicality or task complexity may have on categorization. The current study addresses these issues by examining the effect of exemplar typicality on both the reaction times and accuracy of categorizing basic level exemplars. High-functioning children, teens, and adults with autism and matched controls were tested in a category verification procedure. Results indicate that the processing and accuracy of categorization improves throughout the lifespan for typical and somewhat typical category exemplars, but that processing differences are found throughout the lifespan with respect to atypical or poor category exemplars. The results are discussed in relation to potential differences in the type of processing that may be required for categorizing typical and atypical category members. Parallels are also drawn between the results of the current studies and the results of previous studies on face processing in individuals with autism.

An investigation of the cognitive basis for the selectivity of age-related memory impairment

Overman, Amy A. 05 June 2006 (has links)
Older adults have been found to have a selective impairment in certain types of episodic memory, although other types of memory are generally preserved. The goal of this research is to determine whether the selective age-related memory deficit is best explained by an impairment in perceptual processing, an impairment in the formation of associations between items and their contexts, or an impairment in controlled processing, which is presumed to be required for recollection. Three behavioral experiments were conducted which attempted to evaluate the relative merits of each of these three accounts of age-related memory impairment. To allow for a more meaningful comparison of the data from each experiment, the same participants completed all three behavioral experiments. In addition to the behavioral experiments, an event-related potential (ERP) experiment was conducted to provide further information regarding perceptual processing differences between older and younger adults. When relying solely on perceptual information, rather than semantic and perceptual information, older adults memory performance was especially poor for perceptually impoverished stimuli (words), but less so for perceptually rich stimuli (pictures). Unlike young adults, older adults did not benefit from repeated presentations of pair information, suggesting that older adults do not form associative links between to-be-remembered stimuli. However, older adults did not show a recollection-specific impairment as the controlled processing hypothesis would have predicted. Older adults were equivalently impaired for both recollection and familiarity measures, suggesting that controlled processing is not specifically impaired in older adults. ERPs for older adults had much more individual variability than for young adults and the differences in ERP waveforms between age groups were observed more consistently in word conditions than in picture conditions, which is consistent with the behavioral results. Additionally, older adult ERPs to pictures were most similar to young adults, in accordance with the behavioral results. The behavioral data support the hypothesis that there is a deficit in perceptual processing which may help explain age-related memory impairments. The ERP data, though limited, lends some support to this explanation as it reveals perceptual and semantic processing differences between young and older adults. An associative deficit may be an additional source of memory impairment.

Face Processing Abilities in Children with Autism

Giovannelli, Joyce Lynne 01 June 2006 (has links)
The current study was comprised of three experiments that examined face processing abilities in children (aged five to seven) diagnosed with high functioning autism as compared to control participants matched on verbal mental age and chronological age. Experiment one examined recognition memory for faces using an implicit memory task in which peripheral cues for identity were removed and distinctiveness of facial stimuli was varied. Experiment two was designed to assess gender identification skills with gender stimuli that varied in the degree of typicality of gender. Experiment three examined the recognition of facial expression of emotion using dynamic stimuli that varied in the degree of expression exhibited, from subtle to exaggerated, as evidenced by increased facial muscle movement. Results indicated children with autism exhibited significantly poorer performance on all three face processing tasks, as compared to controls. Among children with high functioning autism, results of experiment one indicated that they do not capitalize on distinctive features as a way of improving memory for faces. Results of experiment two indicated that, as compared to controls, children with autism exhibited more difficulty discriminating gender, even with typical exemplars of gender. Results of experiment three suggest that children with autism found it more difficult to identify dynamic representations of facial expressions of emotion when the expressions were more subtle in presentation. Although children with autism exhibited significantly poorer performance on all three tasks, they were still able to perform at a level above chance, indicating that by the ages of five to seven, children with autism were able to process facial information, although they were developmentally delayed when compared with controls. These results are discussed in the context of several current theories of autism and the literature of both autism and typically-developing face processing abilities.


Janicki, Denise L. 02 June 2006 (has links)
Psychosocial stress might account for some of the variance in cardiovascular disease (CVD) risk that is not explained by traditional risk factors. Most studies of stress and CVD have focused on (a) stress in a single life domain, and (b) clinical CVD outcomes. Few studies have examined physiologic mechanisms that might explain the association between stress and CVD. The primary aim of the present study was to examine whether: (1) chronic stress predicts changes in carotid artery intima-media thickness (IMT) and plaque; and (2) the association between chronic stress and changes in these surrogate CVD endpoints is mediated by inflammatory processes. A secondary aim was to investigate whether individual differences in cardiovascular reactivity (CVR) moderates the association between stress and changes in IMT and plaque. The sample (n=276; M age=60.5), was a subset of the Pittsburgh Healthy Heart Project, a longitudinal investigation of the effects of psychosocial and biological risk factors on surrogate CVD endpoints among healthy older adults. Chronic stress was assessed at baseline with the Chronic Stress Scale (CSS; Norris & Uhl, 1993), a self-report survey that measures stress in 7 life domains during the preceding 6 months. Chronic stress was computed in terms of (a) scores on the 7 CSS subscales and (b) average score across all 7 subscales. Ultrasound IMT measures were taken at baseline and 3 years later. Mean IMT was derived by taking the bilateral average of far wall common, internal and bulb measures. IMT change was computed as the arithmetic difference between follow-up and baseline values. Plaque change was computed as the number of visible lesions at follow-up less the number of lesions at baseline. Blood draws for inflammatory markers and CVR testing were conducted at separate baseline visits. Results failed to support the mediation model. Only the CSS physical stress subscale was an independent predictor of IMT change (b=.02, t=2.13, p=.03). CSS scores were unrelated to plaque, or to inflammatory marker levels. Results did not differ according to CVR. Findings question the importance of chronic stress, as measured by global self-report, as a predictor of change in IMT and plaque.

Examining Theories of Ventromedial Prefrontal Cortex Function

Wheeler, Elizabeth Zabriskie 21 June 2006 (has links)
The ventromedial prefrontal cortex (VMPFC) is an intriguing brain region which sends output to and receives input from memory, emotion and reward related structures such as the amygdala, hippocampus, and caudate nucleus. Humans with lesions to the VMPFC on the surface seem to function normally and most have normal intelligence. However, in high-level tasks blending affect and decision-making, they are often highly impaired. This thesis concerns three behavioral experiments of patients with VMPFC damage which contrast and examine hypotheses of VMPFC function. In Experiment 1, the hypothesis that the VMPFC is involved in representing social knowledge was tested with more rigorous methods and a non social control task. Results did not support a specific role of the VMPFC in social knowledge. In Experiments 2 & 3, the hypothesis that VMPFC is involved in rapid reversal of stimulus-reinforcer associations was examined in detail. A gambling task and a probabilistic learning task helped discriminate punishment versus reward processing. Experiment 2 revealed normal performance of VMPFC patients in a rewards-only reversal task, in contrast to performance on previous gambling tasks with both reversal and punishment. Experiment 3 added to this evidence for a special function in punishment processing by examining learning from punishment versus learning from reward. Results revealed deficits in punishment learning, but not reward learning, after damage to the VMPFC. In conclusion, these experiments suggest a special role for the VMPFC in punishment processing, especially when a change in stimulus choice is indicated.


van Veen, Vincent 21 June 2006 (has links)
People are able to trade off speed and accuracy when performing a task; that is, they can either focus on performing accurately at the cost of being slow, or on being fast at the cost of decreased accuracy. Performance can be varied along this speed-accuracy tradeoff (SAT) continuum. The present set of studies were designed to, first, test the effects of speed versus accuracy emphasis on attentional processes and the underlying neural activity, and, second, to investigate how the brain achieves the desired level of SAT. In Experiment 1 it was found that attentional adjustments on trials following difficult trials or error trials, and their associated neural activation in the anterior cingulate and lateral prefrontal cortices were modulated by SAT. The conflict adaptation effect and associated anterior cingulate and prefrontal activation were greater under speed emphasis, whereas post-error slowing and associated anterior cingulate and prefrontal activation were greater under accuracy emphasis. Experiment 2 tested how people achieve a desired level of SAT by measuring neural activity in response to cues instructing participants whether to either emphasize speed or accuracy during a subsequent set of trials. Increased activation to speed cues was found in brain regions related to the preparation and execution of actions, which was furthermore sustained throughout speeded performance. This suggests that the level of baseline activation in these areas increased under speed emphasis. Moreover, transient, response-related activation of the dorsal premotor cortices was increased during accuracy emphasis. The results of Experiment 2 support computational theories of decision making according to which evidence for one or another decision builds from a baseline to a threshold, and different levels of SAT are achieved by varying the distance between this baseline and threshold. Together, these studies provide novel data that help us better understand how people are able to regulate their performance.

Dyadic Synchrony and The Development of Boys' Conduct Problems in Early Childhood.

Skuban, Emily Moye 29 June 2006 (has links)
Dyadic synchrony has been broadly conceptualized as the quality of the parent-child dyadic relationship from infancy to the school-age period. It has been theorized as a molar construct that captures features of parent-child interaction that are beyond individual attributes. A sample of 120 mother-son dyads from a high-risk, low-income sample were observed at age two years during a series of interactions and coded for their dyadic synchrony. It was hypothesized that characteristics of the child, maternal psychological resources and aspects of parenting would be associated with synchrony. It was also hypothesized that synchrony would be associated with concurrent externalizing symptoms and externalizing symptoms at a 1-year follow-up. Results of a series of bivariate correlations found that synchrony was associated with mother, child and parenting attributes. However, results of a series of hierarchical regression analyses found that synchrony was not associated with concurrent or later externalizing symptoms. While synchrony did not moderate the association between most child characteristics and maternal attributes, synchrony was found to moderate the relationship between maternal depression and later externalizing symptoms. These findings suggest that synchrony is associated with multiple measures of child and maternal functioning; however, in this sample of low-income, high-risk samples where rates of synchrony are generally low and rates of externalizing problems are somewhat higher, an association between externalizing symptoms and synchrony may not be present.

Protective factors and the development of resilience among boys from low-income families

Vanderbilt-Adriance, Ella 28 September 2006 (has links)
The purpose of the study was to advance our understanding of resilience by studying multiple protective factors associated with positive adjustment among an ethnically diverse sample of 226 low-income boys followed prospectively from ages 1.5 to 12, using trajectories of neighborhood quality from ages 1.5-10 to define risk status. The results indicated that child IQ, nurturant parenting, parent-child relationship quality, and marital quality measured in early childhood were all significantly associated with a composite measure tapping low levels of antisocial behavior and high levels of social skills at ages 11 and 12. However, these results were qualified by the fact that marital quality was only significantly related to positive social adjustment in the context of low levels of risk. Results suggest that with the exception of marital quality, these protective factors operate in a comparable manner with respect to positive social adjustment for this predominantly low-income urban sample of boys.


Bleil, Maria Elizabeth 20 September 2006 (has links)
The dispositional tendency to experience negative emotions may underlie correlated psychological risk factors for coronary heart disease (CHD). Here, we examined the relative contribution of variance shared by depression, anxiety, and anger (i.e. negative affect) and the variance unique to each negative affective disposition in predicting cardiac autonomic function as indexed by heart rate variability (HRV). The sample included 653 community volunteers (51.0% female; 15.8% Black) ages 30-54 (M= 43.8 + 7.1). Latent constructs of depression, anxiety, and anger were each measured by three scales from well-validated self-report questionnaires. Indices of HRV were derived from a 5-minute segment of continuous ECG recording and included high frequency (HF-HRV), low frequency (LF-HRV), and the ratio of LF to HF (LF:HF-HRV) power components. Factor analysis/multiple regression and structural equation modeling analyses were employed with covariate-adjustment for age, sex, race, education, BMI, smoking status, SBP, and DBP. At the single-trait level of analysis, examination of depression, anxiety, and anger individually showed depression to predict reduced HF-HRV and LF-HRV and increased LF:HF-HRV, anxiety to predict reduced HF-HRV and LF-HRV, and anger to be unrelated to any HRV index. However, a more complex pattern of relations emerged when the common (i.e. negative affect) and unique effects of depression, anxiety, and anger on HRV were evaluated simultaneously. First, the relation of depression to HRV indices was partially accounted for by negative affect, though variance unique to depression also predicted HF-HRV independently. Secondly, the relation of anxiety to HRV indices was fully accounted for by negative affect. Thirdly, anger emerged as an independent predictor of increased HF-HRV, suggesting the variance that anger shares with depression and anxiety predicts reduced HF-HRV and the variance that is unique to anger predicts increased HF-HRV. In sum, negative affect explains the common effects of psychosocial risk factors for CHD on cardiac autonomic function with unique aspects of depression and anger related independently to reduced and increased vagal modulation of heart rate, respectively. These findings underscore the importance of examining multiple negative affective dispositions in the same analysis to differentiate the elements of these traits that are specifically cardiotoxic.

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