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Thesis (M.A.)--University of Wisconsin--Madison, 1946. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 41-42).

Thesis (M.A.)--University of Wisconsin--Madison, 1944. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 26-27).

Even during fixation, the eye is rarely still, as miniature eye movements continue to occur within fixational periods of the eye. These miniature movements are referred to as fixational eye movements. Microsaccades are one of the three types of fixational eye movements that have been identified. Microsaccades have been attributed to different visual processes/phenomena such as fixation stability, perceptual fading, and multistable perception. Still, debates surrounding the functional role of microsaccades in vision ensued, as many of the findings from earlier microsaccade reports contradict one another and the polarity in the field caused by these debates led many to believe that microsaccades do not hold a necessary/specialized role in vision. To gain a deeper understanding of microsaccades and its relevance in vision, we sought out to assess the role of microsaccades in bistable motion perception in our behavioral/eye-tracking study. Observers participated in an eye-tracking experiment where they were asked to complete a motion discrimination task while viewing a bistable apparent motion stimuli. The collected eye-tracking data was then used to train a classification model to predict directions of illusory motion perceived by observers. We found that small changes in gaze position during fixation, occurring within or outside microsaccadic events, predicted the direction of motion pattern imposed by the motion stimuli. Our findings suggest that microsaccades and fixational eye movements are correlated with motion perception and that miniature eye movements occurring during fixation may have relevance in vision. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

Trial-level evidence for feedback sensitivity in fixations during category learning has been previously described as weak. In this dissertation, steps were taken to overcome some methodological issues potentially obscuring the evidence for such sensitivity. Jointly, the three experiments reported here suggest that sensitivity to error in visual attention reflects cue competition, as opposed to error-driven learning of a selective visual profile. These outcomes are in agreement with previous research in human vision, which holds that fixations reflect the agent’s task representation. A case is made for the top-down control of visual attention during category learning, manifested as effects of prior knowledge, long-standing expectations, decisional uncertainty, and vacillations between alternative sources of conflicting evidence. A suggestion is made that the time-based measures of visual attention may align with the continuous ratings of the perceived category membership (reflecting learner confidence).

Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise) may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency. / text

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