Eyes are an ideal tool for investigating social attention, as their physiological composition with the iris and pupil highly-distinguishable against the white sclera, combined with our foveated vision, mean that gaze cues are both a means of understanding where attention is being allocated and a method for non-verbal communication. Previous attention research using gaze cues has focused on Posner-type paradigms that have supported a model of reflexive orienting of attention in response to gaze cues. However, the ecological validity of this type of paradigm has been called into question given more recent real world research, which has produced findings that cannot be explained by laboratory-based Posner-type paradigms. Therefore, the aim of this thesis was to develop and test a novel, more ecologically-valid paradigm that could investigate observers’ responses to gaze cues in a realistic, but controlled, manner. Based on past research, an initial goal of this research was to develop an early iteration of a realistic visual search paradigm in which a single non-predictive gaze cue is presented. This was built on in later chapters by adding manipulations of task instruction. These chapters presented some evidence that supported a reflexive orienting model of gaze, with clear facilitation to performance as a result of person presence. The second goal of this research was to explore observers’ responses when presented with the same task and search arrays, but with the inclusion of a second gaze cue. This is some of the first research to address multiple gaze cues within a realistic visual search paradigm. These chapters showed multiple gaze cues result in quite considerably different observer eye movement behaviour. Benefits of people presence were stronger and far more congruency effects were apparent. There were also clear effects of instruction, with the suggestion that gaze cues provided may be helpful to the task resulting in significantly greater proportions of overt gaze-seeking than in other instruction conditions. The introduction of multiple gaze cues created a new gaze cue condition – the conflicting condition in which each person cued separate spatial areas within the scene. In order to explore the effects of gaze cue sender reliability on observers’ eye movements, a third version of the study was tested where the gaze cues presented were spatially informative, cuing the target in 70% of trials. Results showed similar benefits of people presence to the previous multiple-cue chapters, but there were minimal reliability effects. Methodological adaptations were suggested based on previous research that has explored reliability effects that may more successfully elicit reliability effects in future research. The final chapter presents a summary of the findings of the research contained within this thesis. The results showed that in a more complex and realistic visual search task employing a single gaze cue, results are somewhat consistent with the reflexive orienting model of gaze due to the clear facilitation as a result of person presence and the lack of instruction effects. The findings presented also demonstrate that once multiple gaze cues are introduced, the reflexive orienting model cannot account for observers’ gaze behaviour. Instead, findings are more consistent with recent real world research. This would suggest that a new model of gaze processing is required when more than one gaze cue is presented, and the final chapter offers some suggestions of what this new model would need to take into account. It is suggested that subsequent research using this novel paradigm should explore the use of dynamic cues and the effects on eye movement behaviour in special populations, and that the research presented in this thesis provides a solid foundation upon which these new directions for research can be built.

abstract: Previous research from Rajsic et al. (2015, 2017) suggests that a visual form of confirmation bias arises during visual search for simple stimuli, under certain conditions, wherein people are biased to seek stimuli matching an initial cue color even when this strategy is not optimal. Furthermore, recent research from our lab suggests that varying the prevalence of cue-colored targets does not attenuate the visual confirmation bias, although people still fail to detect rare targets regardless of whether they match the initial cue (Walenchok et al. under review). The present investigation examines the boundary conditions of the visual confirmation bias under conditions of equal, low, and high cued-target frequency. Across experiments, I found that: (1) People are strongly susceptible to the low-prevalence effect, often failing to detect rare targets regardless of whether they match the cue (Wolfe et al., 2005). (2) However, they are still biased to seek cue-colored stimuli, even when such targets are rare. (3) Regardless of target prevalence, people employ strategies when search is made sufficiently burdensome with distributed items and large search sets. These results further support previous findings that the low-prevalence effect arises from a failure to perceive rare items (Hout et al., 2015), while visual confirmation bias is a bias of attentional guidance (Rajsic et al., 2015, 2017). / Dissertation/Thesis / Doctoral Dissertation Psychology 2018

Individuals with Autistic Spectrum Disorders (ASD) often perform better than typically developing (TD) individuals in simple, albeit difficult, visual search tasks. This ability is often attributed to a lack of drive for coherence or superior local processing. We compare thirty adults with ASD with forty-nine TD individuals and twenty-seven adults with anxiety (ANX) across two real-world visual search tasks. Individuals had to find either a number superimposed over a real-world scene ("œno context" condition) or an object located in a contextually relevant location ("œcontext" condition). Each participant completed forty-one trials in each condition, each with a unique scene. Eye movements were recorded using an SR Research EyeLink 1000 eyetracker. All groups performed better in the context condition. However, the ASD group was less accurate than both groups, across conditions. All groups were quicker to find the target in the context condition but the ASD group was slower than the TD group. Furthermore, the ASD group took longer to initiate their search, fixate on the target, and decide that they had found the target than the TD group. These results suggest that individuals with ASD are able to integrate contextual information to aid the search but that their previously seen visual search advantage may not transfer to visual searches of real-world scenes.

An attentional template based on a feature in visual working memory (VWM) can be used to bias attention toward feature-matching objects in the visual field. Attentional guidance based on a single feature is highly efficient and has been well characterized. It is debated, however, whether multiple features can be used to guide attention simultaneously. Some argue that only a single feature in VWM can be elevated to an “active” state and influence perceptual selection. To evaluate whether multiple features can guide attention simultaneously, eye movements were recorded while participants completed both traditional and gaze-contingent visual search tasks. Participants demonstrated guidance by multiple features by switching between relevant colors frequently and without delay. Furthermore, relevant objects of different colors actively competed for saccadic selection. These results provide compelling evidence that multiple attentional templates are able to guide selection simultaneously. Although it was originally proposed that a feature in VWM could also be used to bias attention away from irrelevant items (“template for rejection”), the evidence thus far has been mixed. Some studies report that participants were faster to find a target item after being cued with a distractor feature, suggesting participants were using this feature to avoid matching items, while other studies report a cost and find that participants actually attended to cue-matching items even though they are irrelevant. The current work demonstrates that some evidence in support of feature-guided avoidance can be explained by spatially recoding the cued feature information. Furthermore, when shown a distractor color at the beginning of a trial, participants frequently fixated a matching object early in the trial, but avoided matching objects later in the trial. Other work has suggested that this initial attentional capture by a cue-matching object facilitates later avoidance, but the current data do not support a functional relationship of this nature. In sum, it may not be possible to implement an exclusionary template directly as feature-guided avoidance, but it may be possible to implement indirectly by converting the irrelevant feature information into relevant feature or spatial information.

In Canada, as baby boomers age, there will be an increase in the percentage of seniors within the general population (Statistics Canada, 2006). Seniors often have difficulty in performing certain everyday tasks and have greater risk of having health issues. As such, it becomes increasingly important to understand factors that pose difficulty for this group of people. As people get older, many visual functions such as visual acuity, contrast sensitivity, and glare are known to deteriorate (Haegerstrom-Portnoy, 2005). However, when considering activities that aid mobility such as driving and walking, vision related variables are not the only ones that create difficulty for older individuals. A sensory variable such as attention, in conjunction with vision, has been shown in previous studies to be a good predictor of difficulties encountered by the elderly (McGwin, Owsley, & Ball, 1998; Owsley, McGwin, Sloane, Stalvey, & Wells, 2001). Moreover, inattention and distraction seem to be common causes of automobile accidents as well as falls. The work load imposed on the working memory can impact distractibility and inattention. In mobility related activities such as driving and walking, individuals perceive objects that are increasing in size. Experiments were designed to investigate the factors that affect the perception of targets that are enlarging in size. Size matching of expanding targets to a previously presented static target, was investigated in a group of younger participants with normal vision using central or peripheral vision. The results show that size estimates differ depending on whether the target appears in the central visual field or in the periphery. The participants respond faster to targets that appear in the periphery compared to those in the centre/midline. In the subsequent set of experiments we compared the performance of younger and older participants using a dual task paradigm where individuals had to perform two tasks concurrently, one of which was to match the size of an enlarging target. Attention was modulated in the dual tasks by varying the difficulty of the secondary task. It has been found that older individuals have difficulty processing multiple visual tasks or performing multiple tasks in general (Pashler, 1994a, 1994b, 1998; Verhaeghen et al., 2003). Compared to younger individuals, older individuals were found to have greater performance difficulty in the highly demanding dual tasks. These results are compared to those observed in studies of psychological refractory period effects. The differences between the young and older individuals are discussed with respect to limited capacity and bottle neck models of attention. Furthermore, eye movement measures in the dual tasks seem to provide evidence of difficulty in task switching for the older observers. The thesis also investigated the functional field of view of younger and older individuals. By assessing the functional field of view (FFOV) using a method employed earlier by Coeckelbergh et al., (2004a), significant overall age related differences were found. Multiple characteristics of what might affect the FFOV as measured by the attended field of view (AFOV) were also investigated (e.g., impact of a pop out distracter and divided attention). It was found that differences between the two age groups occurred in all conditions. The presence of irrelevant distracters had a greater impact on the older individuals compared to the younger group, whereas divided attention or the presence of the pop out distracter did not affect either age group. Attention processing seemed to be similar for both the younger and older individuals and, therefore, the differences between the age groups appear to be at a quantitative level rather than a qualitative level.

In Canada, as baby boomers age, there will be an increase in the percentage of seniors within the general population (Statistics Canada, 2006). Seniors often have difficulty in performing certain everyday tasks and have greater risk of having health issues. As such, it becomes increasingly important to understand factors that pose difficulty for this group of people. As people get older, many visual functions such as visual acuity, contrast sensitivity, and glare are known to deteriorate (Haegerstrom-Portnoy, 2005). However, when considering activities that aid mobility such as driving and walking, vision related variables are not the only ones that create difficulty for older individuals. A sensory variable such as attention, in conjunction with vision, has been shown in previous studies to be a good predictor of difficulties encountered by the elderly (McGwin, Owsley, & Ball, 1998; Owsley, McGwin, Sloane, Stalvey, & Wells, 2001). Moreover, inattention and distraction seem to be common causes of automobile accidents as well as falls. The work load imposed on the working memory can impact distractibility and inattention. In mobility related activities such as driving and walking, individuals perceive objects that are increasing in size. Experiments were designed to investigate the factors that affect the perception of targets that are enlarging in size. Size matching of expanding targets to a previously presented static target, was investigated in a group of younger participants with normal vision using central or peripheral vision. The results show that size estimates differ depending on whether the target appears in the central visual field or in the periphery. The participants respond faster to targets that appear in the periphery compared to those in the centre/midline. In the subsequent set of experiments we compared the performance of younger and older participants using a dual task paradigm where individuals had to perform two tasks concurrently, one of which was to match the size of an enlarging target. Attention was modulated in the dual tasks by varying the difficulty of the secondary task. It has been found that older individuals have difficulty processing multiple visual tasks or performing multiple tasks in general (Pashler, 1994a, 1994b, 1998; Verhaeghen et al., 2003). Compared to younger individuals, older individuals were found to have greater performance difficulty in the highly demanding dual tasks. These results are compared to those observed in studies of psychological refractory period effects. The differences between the young and older individuals are discussed with respect to limited capacity and bottle neck models of attention. Furthermore, eye movement measures in the dual tasks seem to provide evidence of difficulty in task switching for the older observers. The thesis also investigated the functional field of view of younger and older individuals. By assessing the functional field of view (FFOV) using a method employed earlier by Coeckelbergh et al., (2004a), significant overall age related differences were found. Multiple characteristics of what might affect the FFOV as measured by the attended field of view (AFOV) were also investigated (e.g., impact of a pop out distracter and divided attention). It was found that differences between the two age groups occurred in all conditions. The presence of irrelevant distracters had a greater impact on the older individuals compared to the younger group, whereas divided attention or the presence of the pop out distracter did not affect either age group. Attention processing seemed to be similar for both the younger and older individuals and, therefore, the differences between the age groups appear to be at a quantitative level rather than a qualitative level.

<p>A pervasive aspect of daily life is searching for a specific target amongst an array of distracting items. Studying such visual searches offers a useful and powerful tool for revealing the underlying aspects of visual attention. Understanding how factors influence accurate target detection serves to both enhance real-world search tasks and inform basic cognitive psychology. The goal of the research presented herein is to examine the effects of expectation, experience, and environment on search behavior. The experiments are conducted in controlled laboratory environments, but are designed to simulate real-world searches, with the express goal of informing the implementation of search tasks in everyday life. First, <italic>expectation </italic>is explored by manipulating target prevalence and measuring the resultant change in behavior as participants' biases shift. Second, <italic>experience </italic>is tested by comparing individuals with and without extensive video game exposure, specifically on their susceptibility to the pressures of rare target search. Lastly,<italic> environment</italic> is examined by utilizing multiple simultaneous targets. This manipulation has been shown to induce errors in radiology, and here the generality of this effect is explored to establish the various pressures to which it is sensitive. Collectively, these data serve to inform how different influences modulate visual search performance, and the results can directly inform the training, recruitment, and execution of real-world search tasks such as those in radiology, cytology, and airport security.</p> / Dissertation

The current study examined two means of reducing uncertainty in visual search: 1) visual relatedness of a prime to the target (a data-driven, bottom-up processing) and 2) expectancy (a top-down process based on the proportion of validly primed trials). The two processes were decoupled using a short and a long inter-stimulus interval (ISI) to examine their time course in visual search. Competing hypotheses were contrasted in order to determine whether relatedness is associated with iconic memory (Neely, 1977) or a longer lasting visual-structural implicit memory (Schacter and Cooper, 1995) and what role participant expectancy plays in visual search performance. Twelve participants engaged in a discrimination task and a visual search task. The obtained results suggest that visual relatedness is a bottom-up process, probably mediated by a short-term iconic store that affects search performance early, but whose effects rapidly decay. They also suggest that expectancy is a top-down process that requires time to build up before it can affect visual search performance, but whose effects are more long lasting than visual relatedness.

This research study examined the design of a virtual keyboard that can be used for text entry with a rotary controller, particularly when users may differ in age and experience with a particular system. I specifically examined the shape and letter arrangement on the virtual keyboard to help determine the best features to use in a design. Two keyboard shapes, an Oval and a Plus, were selected to represent different aspects of the shape. Two keyboard arrangements, Alphabetic and a Standard QWERTY-based ordering, were selected to represent a well-known and less familiar arrangement. In the experiment, older and younger adults entered words over two consecutive days. Most of the time, they used either the Oval or the Plus, but they also used the alternate shape at specific points during their practice session to allow assessment of their ability to transfer what they had learned. At the end of the second day, they also used a variation of the practiced arrangement to examine how well they had learned the letter arrangement. Text entry performance on both shapes improved as a function of practice, demonstrating that participants could learn even unfamiliar devices and virtual keyboards to complete a word entry task. No overall shape effects were found for any level of performance, but shape did affect how participants learned and performed the word entry task. In particular, unique visual features on a shape may facilitate memorization of letter/visual cue mappings. These shape features are particularly important for older adults, as younger adults seem to develop a mental model that helps them memorize letter locations on either shape. With practice, older adults could achieve optimal performance levels with an Alphabetic keyboard on the Plus shape that has the more visually unique corners. In general, alphabetic ordering is best not only because it helped visual search, but also because it facilitated better movement planning. Overall, designers should consider creating unique visual features on a virtual keyboard that will blend with the compatibility and allowed movements for the selected device to create an effective virtual keyboard.

When multiple objects are present in a visual scene, salient and behaviorally relevant objects are selectively processed at the expense of less salient or irrelevant objects. Here I used three lateralized components of the event-related potential â " the N2pc, Ptc, and SPCN â " to examine how objects compete for representation in our limited capacity visual system, and how task-relevant objects are selectively processed. Participants responded to the orientation of a color singleton target while ignoring a color singleton distractor. Competition between the objects was manipulated by presenting visual search arrays that contained only a target, only a distractor, or both objects together. In Experiment 1, observers did not know the color of the target in advance, whereas in Experiment 2 this information was provided. Experiment 3 was a control experiment to rule out low-level sensory explanations of the effects. The results suggest that the N2pc component indexes capture of attention by salient objects which is modulated both by competition between the objects and top-down knowledge. The Ptc component may index inhibition of return so that once an object is processed it is not selected again. The SPCN component may index enhancement of goal-relevant objects once task-irrelevant objects have been suppressed. Together these lateralized event-related potentials reveal the temporal dynamics of competition and selectivity in the human visual system.