Much about visual spatial attention has been learned from studying how observers respond to two-dimensional stimuli. Less is known about how attention varies along the depth axis. Most of the work on the effect of depth on spatial attention manipulated binocular disparity defined depth, and it is less clear how monocular depth cues affect spatial attention. This thesis investigates the effect of target distance on peripheral detection in a virtual three-dimensional environment that simulated distance using pictorial and motion cues. Participants followed a lead car at a constant distance actively or passively, while travelling along a straight trajectory. The horizontal distribution of attention was measured using a peripheral target detection task. Both car-following and peripheral detection were tested alone under focussed attention, and simultaneously under divided attention. Chapter 2 evaluated the effect of target distance and eccentricity on peripheral detection. Experiment 1 found an overall near advantage that increased at larger eccentricities. Experiment 2 examined the effect of anticipation on target detection and found that equating anticipation across distances drastically reduced the effect of distance in reaction time, but did not affect accuracy. Experiments 3 and 4 examined the relative contributions of pictorial cues on the effect of target distance and found that the background texture that surrounded the targets could explain the main effect of distance but could not fully account for the interaction between distance and eccentricity. Chapter 3 extended the findings of Chapter 2 and found that the effect of distance on peripheral detection in our conditions was non-monotonic and did not depend on fixation distance. Across chapters, dividing attention between the central car-following and peripheral target detection tasks consistently resulted in costs for car-following, but not for peripheral detection. This work has implications for understanding spatial attention and design of advanced driver assistance systems. / Dissertation / Doctor of Science (PhD) / Our visual world is complex and dynamic, and spatial attention enables us to focus on certain relevant locations of our world. However, much of what we know about spatial attention has been studied in the context of a two-dimensional plane, and less is known about how it varies in the third dimension: depth. This thesis aims to better understand how spatial attention is affected by depth in a virtual three-dimensional environment, particularly in a driving context. Generally, driving was simulated using a car-following task, spatial attention was measured in a task that required detecting targets appearing at different depths indicated by cues perceivable with one eye. The results of this work add to the literature that suggests that spatial attention is affected by depth and contributes to our understanding of how attention may be allocated in space. Additionally, this thesis may have implications for the design of in-car warning systems.

Previous research suggests that cellular phone conversations or similar auditory/conversational tasks lead to degradations in visual processing. Three contemporary theories make different claims about the nature of the degradation that occurs when we talk on a cellular phone. We are either: (a) disproportionately more likely to miss objects located in the most peripheral areas of the visual environment due to a reduction in the size of the attentional window or functional field of view (Atchley & Dressel, 2004); (b) more likely to miss objects from all areas of the visual environment (even at the center of fixation) because attention is withdrawn from the roadway, leading to inattention blindness or general interference (Strayer & Drews, 2006; Crundall, Underwood, & Chapman, 1999; 2002), or (c) more likely to miss objects that are located on the side of the visual environment contralateral to the cellular phone message due to crossmodal links in spatial attention (Driver & Spence, 2004). These three theories were compared by asking participants to complete central and peripheral visual tasks (i.e., a measure of the functional field of view) in isolation and in combination with an auditory task. During the combined visual/auditory task, peripheral visual targets could appear on the same side as auditory targets or on the opposite side. When the congruency between auditory and visual target locations was not considered (as is typical in previous research), the results were consistent with the general interference/inattention blindness theory, but not the reduced functional field of view theory. Yet, when congruency effects were considered, the results support the theory that crossmodal links affect the spatial allocation of attention: Participants were better at detecting and localizing visual peripheral targets and at generating words for the auditory task if attention was directed to the same location in both modalities.

Doctor of Philosophy / Department of Psychological Sciences / Lester Loschky / Everyday event perception requires us to perceive a nearly constant stream of dynamic information. Although we perceive these events as being continuous, there is ample evidence that we “chunk” our experiences into manageable bits (Zacks & Swallow, 2007). These chunks can occur at fine and coarse grains, with fine event segments being nested within coarse-grained segments. Individual differences in boundary detection are important predictors for subsequent memory encoding and retrieval and are relevant to both normative and pathological spectra of cognition. However, the nature of attention in relation to event structure is not yet well understood. Attention is the process which suppresses irrelevant information while facilitating the extraction of relevant information. Though attentional changes are known to occur around event boundaries, it is still not well understood when and where these changes occur. A newly developed method for measuring attention, the Gaze-Contingent Useful Field of View Task (GC-UFOV; Gaspar et al., 2016; Ringer, Throneburg, Johnson, Kramer, & Loschky, 2016; Ward et al., 2018) provides a means of measuring attention across the visual field (a) in simulated real-world environments and (b) independent of eccentricity-dependent visual constraints. To measure attention, participants performed the GC-UFOV task while watching pre-segmented videos of everyday activities (Eisenberg & Zacks, 2016; Sargent et al., 2013). Attention was probed from 4 seconds prior to 6 seconds after coarse, fine, and non-event boundaries. Afterward, participants’ memories for objects and event order were tested, followed by event segmentation. Attention was predicted to either become impaired (attentional impairment hypothesis), or it was predicted to be broadly distributed at event boundaries and narrowed at event middles (the ambient-to-focal shift hypothesis). The results showed marginal evidence for both attentional impairment and ambient-to-focal shift hypotheses, however model fitness was equal for both models. The results of this study were then used to develop a proposed program of research to further explore the nature of attention during event perception, as well as the ability of these two hypotheses to explain the relationship between attention and memory during real-world event perception.

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A growing body of literature suggests that aging causes restrictions in mobility, gaze, and cognitive functions, increasing the risk of falls and adverse health events. A novel Dual-Task Treadmill walking (DT-TW) program was designed to train balance, gaze, cognition, and gait simultaneously. Eleven healthy community-dwelling older adults (age 70-80 yrs) were recruited to play a variety of computer games while standing on a sponge surface and walking on a treadmill. Data on centre of pressure (COP) excursion for core balance, spatio-temporal gait variability parameters, head tracking performances, and neuropsychological tests were collected pre and post intervention. A significant improvement in balance, gaze, cognition, and gait performance was observed under dual-task conditions. The study thus concludes that DT-TW is a novel intervention program which combines interactive games with exercises to train dual-task abilities in community dwelling older adults. / October 2015