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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.
1

Implicit and Explicit Consequences of Distraction for Aging and Memory

Thomas, Ruthann C. 15 September 2011 (has links)
This investigation explored implicit and explicit memory consequences of age differences in susceptibility to distraction when previous distraction occurs as target information in a later memory task. Younger and older adults were presented with either implicit (Study 1) or explicit (Studies 2 and 3) memory tasks that included previously distracting and new words. Study 1 explored whether prior exposure to distraction would transfer to improve memory when previously distracting words were included in list to be studied for a recall task. Older adults recalled more previously distracting than new words whereas younger adults recalled the same amount of previously distracting and new words. This initial study was implicit in its use of previously distracting information in that participants were neither informed nor aware of their prior exposure to words in the recall task. Here, only older adults’ memory was influenced by prior exposure to distraction and their recall actually increased to the level of younger adults with implicit use of distraction to improve performance. Subsequent studies investigated explicit influences of prior exposure to distraction on later memory. In Study 2, both younger and older adults showed reliable memory for previously distracting words in an explicit recognition task. These results suggest that although younger adults encode distraction, they do not transfer this information when previous distraction occurs as target stimuli in an implicit memory task. Study 3 investigated whether participants would transfer previous distraction to improve recall if the task was explicit in its use of previous distraction. When cueing instructions were given before the memory task informing participants of the connection between tasks, older adults once again recalled more previously distracting than new words. In contrast to the results of Study 1, younger adults also recalled more previously distracting than new words. Taken together, the results indicate that younger adults do encode distraction, but they require explicit instructions to transfer their knowledge of distraction to later tasks. In contrast, older adults apply their knowledge of distraction in both implicit and explicit memory tasks. Implications are discussed in terms of inhibitory control theory and age differences in strategies engaged in memory tasks.
2

Happy Distraction: Positive Affect Broadens Attention to Irrelevant Information

Biss, Renee Katherine 24 February 2009 (has links)
The present study investigated the claim that positive mood broadens the scope of attention to include irrelevant information, and if so, whether this loosening of attentional control has longer term cognitive consequences. In Experiment 1, participants in an induced happy mood were more influenced by distracting information that interfered with responses in the global-local task, particularly when this information was global in nature. Experiment 2 demonstrated that, when previously irrelevant information became solutions on a subsequent task, implicit memory for this distraction was positively correlated with naturally-occurring positive mood. This study corroborates findings that individuals in a happy mood are more affected by distracting irrelevant information. Furthermore, this widened scope of attention can facilitate performance on a subsequent task, a finding with implications for the relationship between positive mood and creativity.
3

Effects of Attention on Change Deafness

Backer, Kristina Carol 14 December 2010 (has links)
Detecting acoustic changes in our environment, such as a rattlesnake’s sudden approach, can be essential for survival. Although auditory change detection has been intensively investigated using sequentially-presented sounds, very little is known about how we detect changes in a natural, complex scene comprised of multiple concurrent sounds. The present study used a location-switch change deafness paradigm; on each trial, participants listened to two consecutive auditory scenes, consisting of three natural sounds played in distinct locations, and reported if the two scenes were the same or identified the two sounds that switched locations. Directing a listener’s attention to a changing sound improved accuracy and decreased reaction time, relative to uncued trials. However, when participants’ attention was invalidly directed to a non-changing sound object, performance suffered. Further analyses showed that these effects could not be explained by energetic masking. Thus, attention is necessary for change identification in complex auditory scenes.
4

The Role of Estrogens in Cognition: Does Prophylactic Oophorectomy Affect Verbal, Spatial and Working Memory?

Schwartz, Deborah 11 January 2011 (has links)
Studies of non-human animals have shown that estrogens have a significant effect on the structure and neurochemistry of the brain and on cognitive behaviours. This study examines women with BRCA1/2 mutations who have undergone bilateral salpingo-oophorectomy (BSO), resulting in surgical menopause. In order to understand how the absence of endogenous estrogens affects cognition, women with BSO are compared to women with BRCA1/2 mutations but without BSO, as well as age-matched controls on tests of verbal, spatial and working memory. Women with BSO show decreased verbal memory and attention (logical memory) relative to controls but better performance on a measure of temporal lobe function (fluency clustering). Further, concentration of estrogen metabolites (E1G) negatively correlated with performance on a spatial memory task (object placement task) and with fluency clustering. These results indicate that endogenous estrogens are important for verbal memory and attention, but may contribute negatively to spatial memory and fluency clustering.
5

Age-related Differences in the Perceptual Organization of Speech Sounds

Hutka, Stefanie Andrea 08 December 2011 (has links)
Aging is associated with a decline in the ability to understand what a person is saying in the presence of other sounds. This study investigated the perceptual organization of speech in young (n=20) and older adults (n=20). Four vowels were arranged into six sequences, defined by either continuous or discontinuous first-formant transitions. Participants first made an objective response (choosing the sequence that best matched the one they just heard from a list), followed by a subjective response (indicating if they heard one or two streams of sound). There were significant interactions between age and sequence-type for both objective and subjective responses, respectively. These results suggest that aging affects the ability to perceptually organize speech-sounds and the ability to perceive sequential streaming of speech. These findings are discussed within the context of further enriching what is known about auditory scene analysis, cognitive aging, and sequential streaming.
6

Inhibitory Account of Semantic Interference Resolution in Memory: Suppression of Competing Information

Ngo, Ka Wai Joan 15 December 2011 (has links)
Using a novel paradigm, we provide direct evidence for the role of inhibition during semantic interference resolution in memory. In Experiment 1, target words were primed via a naming task. Then, a cue word prompted participants to generate either a meaningfully related or unrelated word. Producing an unrelated word should require suppression of the cue's closest associates, which were the primed targets. Finally, participants read a list of words including the suppressed targets. Participants were slower to name targets in the unrelated condition than in the related condition, indicating that generating an unrelated word required suppression of competitors. Experiment 2 eliminated the initial priming phase, and a robust suppression effect was observed. Both studies showed that naming targets in the unrelated condition was even slower than controls. These results reflect that resolving semantic competition entails suppression of rejected competitors to below baseline levels, supporting an inhibitory account of interference resolution.
7

Normal Aging and Interacting Attentional Processes

Hughes, Jessica Ann 08 December 2011 (has links)
To examine whether executive attention is affected by perceptual attention, we manipulated executive load in a single experiment. Moreover, we assessed the influence of normal aging on knowledge-driven and attentional sensory-driven processes. Healthy young and older adult participants viewed visual streams of superimposed face/place images at low and high perceptual loads while making sex judgments on each face component and then completing a low or high executive load working memory task. Younger adults exhibited independent behavioural patterns for the executive and perceptual load manipulations due to intact selective attention mechanisms, whereas older adults exhibited interacting processes. This is evidenced by the performance of older adults on concurrent executive and perceptual tasks, which was associated with working memory capacity; whereas younger adults did not exhibit this dependency. Selective attention processes that are independent in younger populations seem to converge in older populations due to decrements in executive and perceptual attention domains.
8

Schematic Representation Across Age and in Patients with vmPFC Lesions

Ghosh, Vanessa 20 November 2012 (has links)
This study tested the mechanism of the ventromedial prefrontal cortex (vmPFC) in representing schemata, be it excitatory or inhibitory. Participants were administered a behavioural task distinguishing their ability to activate a relevant schema from their ability to inhibit an irrelevant schema. Healthy participants were highly accurate throughout the task, indicating proficiency in both abilities. However, older adults demonstrated a need for greater cognitive resources to inhibit a previously relevant schema. Non-confabulating patients with vmPFC lesions acted similarly to control participants, while patients with vmPFC lesions with either current or prior demonstration of confabulation performed abnormally. Specifically, their inability to inhibit irrelevant schemata was more severe than their inability to activate a relevant one. The results suggest that the nature of vmPFC damage leading to confabulation may also be responsible for erroneous schema representations. A sub-region of the vmPFC is proposed to underlie the representation of schemata through semantic lateral inhibition.
9

Temporal Integration of English Words: Evidence for a Processing Hierarchy in Visual Word Recognition

Chu, Ronald 21 November 2012 (has links)
Several models of visual word recognition suggest a processing hierarchy; basic orthographic features are processed early and whole-word representations are processed late in the hierarchy. Unfortunately, given the extreme efficiency of the visual word recognition system, studies typically focus on one specific level of the processing hierarchy (e.g., orthographic, phonological and/or semantic processing). Furthermore, different paradigms are used to study different levels of the hierarchy. Fortunately, data across different studies in the literature do converge to two distinct temporal thresholds for letter perception and whole-word integration. The current experiments assessed the temporal thresholds for both letter perception and whole-word integration using a single novel paradigm. The results demonstrated distinct temporal thresholds for letter perception and whole-word integration which agree with those reported in the literature. Thus, the current experiments provide further behavioral evidence that the visual word recognition is a hierarchical process.
10

Effects of Attention on Change Deafness

Backer, Kristina Carol 14 December 2010 (has links)
Detecting acoustic changes in our environment, such as a rattlesnake’s sudden approach, can be essential for survival. Although auditory change detection has been intensively investigated using sequentially-presented sounds, very little is known about how we detect changes in a natural, complex scene comprised of multiple concurrent sounds. The present study used a location-switch change deafness paradigm; on each trial, participants listened to two consecutive auditory scenes, consisting of three natural sounds played in distinct locations, and reported if the two scenes were the same or identified the two sounds that switched locations. Directing a listener’s attention to a changing sound improved accuracy and decreased reaction time, relative to uncued trials. However, when participants’ attention was invalidly directed to a non-changing sound object, performance suffered. Further analyses showed that these effects could not be explained by energetic masking. Thus, attention is necessary for change identification in complex auditory scenes.

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