No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

A forced-choice reaction time (RT) task was used to examine the efficiency of visual filtering (the inhibition of processing of irrelevant stimuli) and the concomitant ability to narrow the focus of the attentional lens in persons with Down syndrome (n = 10) and children of average intelligence (n = 13) matched for mental age (MA) (average MA = approximately 5.7 years). Conditions varied with regard to the presence or absence of distractors and their proximity to a target stimulus, and the presence or absence of a visual window within which the target stimulus was presented. Although the study yielded no significant results due to a lack of power, the mean correct reaction times (RTs) indicate that both the adults with Down syndrome and the typically developing children were less efficient at filtering close distractors as compared to far distractors or no distractors. As well, the results suggest that the presence of the visual window failed to facilitate performance in both groups. Further investigation is warranted to determine the status of visual filtering in persons with Down syndrome relative to their level of functioning at an MA level of approximately 5 years, a period that is critical in the development of attentional processes.

Because children are bombarded by an abundance of information from the environment, the development of the ability to filter extraneous information in order to attend to the most relevant information is crucial for optimal information processing. The ability to effectively filter affects every aspect of children's functioning, including educational activities and social interactions. In order to assess the development of filtering with ecologically relevant factors, a forced-choice filtering paradigm in which the target and distracting stimuli were presented at different times was used to measure the speed of target identification among a group of 6-year-olds (n=10), 7-year-olds (n=12), 9-year-olds (n=13) and adults (n=13). The targets were presented at the centre of a computer screen with flankers presented to their left and right along the same horizontal plane. The flankers varied with regard to proximity to the target and were presented 200 ms or 400 ms before, at the same time as, or 200 or 400 ms after the presentation of the target. The distance between the distractors and target was also varied to assess the ability of participants to optimally narrow their focus of attention. Temporal differences in the onset of the target and distractors were used to assess issues of attentional control in a real-world context, where attention must be maintained within a changing environment. Though no difference in response time was observed for the presentation of close and far flankers, the display of flankers before the targets led to faster response times in all four groups while the display of flankers after the target led to slower response times in the two youngest groups. The results are consistent with the notion that children are less efficient in their ability to filter attention compared to adults. Findings are discussed in relation to developmental changes from age 6 years to adulthood.

No description available.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 213-225) / Microfiche. / xvii, 225 leaves, bound ill. 29 cm