The present dissertation investigates perceptual grouping and shape completion in motion in younger and older observers. The first set of experimental results, Chapter 2, provides a set of exploratory experiments which characterize the nature of a motion grouping task, uncovering accurate direction discrimination when the stimulus contains a cue for global grouping, but compelling illusory motion when the stimulus does not contain that cue. Chapter 3 builds on the findings of Chapter 2 by measuring biases in motion integration that lead to the illusory motion. Chapter 3 extends this paradigm into older adult observers, and explores various stimulus variants and tasks to add to the characterization of this effect. In Chapter 4 the concepts of grouping and motion perception are examined in the context of shape completion by measuring the accuracy of aspect ratio, size, and area discrimination in younger and older adults. Chapter 4 concludes that older adults are worse at discriminating characteristics of shapes, but are similarly affected by incomplete or occluded stimuli as younger adults. On the whole, the dissertation demonstrates several novel findings in the perceptual organization literature, and investigates many of these phenomena into older adults populations. Throughout the dissertation, a central theme concerns the concept of behavioural measurement of perceptual processes, and consequently many of the phenomena are studied using several types of measurements and tasks to ensure a complete picture of the perceptual experience. The current dissertation presents a novel and important addition to the current literature in perceptual grouping and shape completion. / Dissertation / Bachelor of Arts (BA) / The visual experience of a human observer is the result of perceptual processing of the brain. The current dissertation focuses on a subset of these processes that concern the grouping of segmented parts into a single shape, while those segmented parts are in motion. This type of visual experience occurs regularly, in situations where part of a visual scene is occluded such as when viewing a moving object through a window occluded by window blinds. In general, we measure an observer's ability to identify the sources of motion, and the ability to infer the shape of the grouped object. In each experiment, the physical stimulus is varied while observers complete tasks using this stimulus. The dissertation characterizes perceptual organization processes using a number of different tasks, stimuli and paradigms in both younger and older adults. Each experimental result characterizes the perceptual abilities of younger and older observers, contributing to the literature of visual perceptual organization in aging.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25146 |
| Date | January 2019 |
| Creators | Cali, Jessica N. |
| Contributors | Sekuler, Allison B., Bennett, Patrick J., Psychology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Article |
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