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Previous neurophysiological and behavioural studies have shown that attention can be guided by the contents of working memory (WM), and that such guidance can be involuntary even when it is detrimental to the task at hand. In three experiments, this thesis investigated whether the guidance of visual attention from WM could be generalized from a specific stimulus or a task to a category. Experiment 1 tested whether maintaining a set of stimuli of a specific category in WM would influence participants' deployment of visual attention to favour other stimuli that belonged to the same category. Experiment 2 further manipulated the interval between the onset of a critical prime (i.e., a stimulus in the same category as the stimuli held in WM) and the target to determine whether the results of Experiment 1 were associated with the lack of time for attention to be focused onto the critical prime. In both experiments, the stimuli held in WM never appeared in the prime display. In Experiment 3, the identity of the prime was manipulated so that it matched the stimuli held in WM on half of the trials. The results showed that when the stimuli held in WM never reappeared in the prime display (Experiments 1 and 2) there was no evidence that maintaining specific stimuli in WM biased the distribution of attention to other stimuli within the same category. However, when the stimuli held in WM could reappear in the prime display on some trials (Experiment 3), the participants whose reaction times were relatively fast showed evidence for category-based WM guidance of attention when the critical prime item was a new stimulus in the same category as the stimuli held in WM. In contrast, the participants whose reaction times were relatively slow showed a non-spatially specific cost when the critical prime was one of the WM items than when it was a new item in the same category. These results showed that category-based WM could guide the deployment of visual attention under certain conditions. It further suggests that the relationship between WM and attention is more complex than what is outlined by the biased competition theory and related theories of attention.

A dual-task paradigm was used to infer the processes critical for episodic memory retrieval by measuring susceptibility to memory interference from different distracting tasks. Research suggests that retrieval interference occurs due to material-specific overlap between concurrent tasks. I tested whether interference could instead arise from processing-specific overlap. In Experiment 1, I took advantage of individual differences in how verbal materials could be represented in those with different language backgrounds. I compared recognition of studied information in English and Chinese speakers under full attention (FA) or under one of two different divided attention (DA) conditions. Participants viewed simplified Chinese characters or English words, and later completed recognition while simultaneously performing distracting tasks requiring phonological (DAP) or visuospatial (DAV) processing of auditorily presented letters. I found an interaction such that Chinese speakers were more susceptible to interference from the visuospatial than phonological distracting task, whereas the reverse pattern was shown in English speakers. These results suggest that interference with memory retrieval is processing-, not material-, specific, as both distracting tasks used the same materials. Next I sought to determine whether processing-specific interference could be observed within the visuo-spatial domain. Accordingly, in Experiments 2 and 3, I examined whether face recognition would be disrupted more by a distracting task requiring configural than featural processing. In Experiment 2, participants studied faces under FA and subsequently performed a recognition task under either FA or each of two different DA conditions in which a distracting face was presented alongside, requiring either a featural (DAF) or configural (DAC) decision. In line with a material-specific account of interference, face memory accuracy was disrupted in both DA conditions relative to the FA condition, although no processing-specific differences in interference were found between the DA conditions, likely because both distracting tasks engaged configural processing. To better isolate the different processing streams in Experiment 3, some faces were inverted to offset configural processing and to engage featural processing. I compared patterns of memory interference when target faces were presented upright (configural) or inverted (featural). I found a crossover interaction: memory for upright faces was worse in the DAC than in the DAF condition, whereas the reverse was true for inverted target faces, supporting a processing-specific account of memory interference. In Experiment 4, I sought to rule out task difficulty as an alternative explanation for the pattern of interference effects. I measured whether each distracting task produced similar slowing, which provides an indirect assessment of resource requirements of a task, on a simultaneously performed auditory tone discrimination task. Results showed that my distracting tasks were not differentially attention demanding, as indexed by similar accuracy rates for tone classification and response times on the tone discrimination task when performed concurrently with each distracting task. Findings suggest that the magnitude of memory interference under DA conditions at retrieval is influenced by material-specificity but that, critically, it also depends on the extent to which the processing demands of the distracting and retrieval tasks overlap. I have shown here that retrieval is not automatic or obligatory as others have suggested, but instead is subject to disruption. This thesis specifies that retrieval interference can occur due to competition for a limited pool of common processing resources across target and distracting tasks. Thus, when trying to recall studied information, one should avoid distracting conditions, especially those that overlap significantly not only with the type of materials tested but also with the mental processes required to retrieve that target information.

Are we conscious of more than what's in the “spotlight” of attention, or is consciousness limited to the content of attention? Recently several authors (DeBrigard & Prinz 2011; Prinz 2010; Dennett & Cohen 2012) have defended the view that attention to some object is necessary for conscious perception of that object. For each of these authors, attention acts like more than just a “spotlight on a stage.” But none of them provides a robust account of this new way of attending. My project offers a new theory of diffuse attention that explains the apparent richness of experience. Accepting that there is a diffuse way of attending requires us to abandon the notion of attention as a spotlight. On the view that I offer, attention has degrees. For example, when looking at a landscape, your attention is spread over a broad spatial area and details are more difficult to remember or describe than when you focus attention in greater depth on some object within that landscape. A broad and shallow diffusion of attention nonetheless makes its object available for guiding thought and action, and so should be considered a way of attending rather than merely being conscious. After defending a theory of diffuse attention, I offer a new argument for the view that attention is necessary for conscious perception. My argument is motivated by the phenomenological observation that ordinary perceptual experience has a structure: some objects are in the foreground of experience, while others are in the background. I motivate the claim that this foreground/background structure is necessary for perceptual experience, and argue that focal and diffuse attention provide the foreground/background structure. I conclude that attention is necessary for perceptual experience, since it provides a necessary structure of experience. In making this argument, I draw on phenomenological insight into the structure of consciousness from James (1890), Gurwitsch (1964; 1966) and C.O. Evans (1970). For each of these authors, attention structures the foreground – but not the background – of consciousness. My novel contribution is to provide an account of how attention structures the conscious background. By enriching the concept of attention to include diffuse attention, my account is poised to explain the structure of conscious experience from foreground to background.

Are we conscious of more than what's in the “spotlight” of attention, or is consciousness limited to the content of attention? Recently several authors (DeBrigard & Prinz 2011; Prinz 2010; Dennett & Cohen 2012) have defended the view that attention to some object is necessary for conscious perception of that object. For each of these authors, attention acts like more than just a “spotlight on a stage.” But none of them provides a robust account of this new way of attending. My project offers a new theory of diffuse attention that explains the apparent richness of experience. Accepting that there is a diffuse way of attending requires us to abandon the notion of attention as a spotlight. On the view that I offer, attention has degrees. For example, when looking at a landscape, your attention is spread over a broad spatial area and details are more difficult to remember or describe than when you focus attention in greater depth on some object within that landscape. A broad and shallow diffusion of attention nonetheless makes its object available for guiding thought and action, and so should be considered a way of attending rather than merely being conscious. After defending a theory of diffuse attention, I offer a new argument for the view that attention is necessary for conscious perception. My argument is motivated by the phenomenological observation that ordinary perceptual experience has a structure: some objects are in the foreground of experience, while others are in the background. I motivate the claim that this foreground/background structure is necessary for perceptual experience, and argue that focal and diffuse attention provide the foreground/background structure. I conclude that attention is necessary for perceptual experience, since it provides a necessary structure of experience. In making this argument, I draw on phenomenological insight into the structure of consciousness from James (1890), Gurwitsch (1964; 1966) and C.O. Evans (1970). For each of these authors, attention structures the foreground – but not the background – of consciousness. My novel contribution is to provide an account of how attention structures the conscious background. By enriching the concept of attention to include diffuse attention, my account is poised to explain the structure of conscious experience from foreground to background.

Experiments were conducted to investigate the role of attention in peripheral detection and discrimination. Advance spatial cues informed subjects about likely target positions; the task required to detect/discriminate plus localise a target briefly presented at cued or uncued locations, with accuracy as the dependent variable ("cost-benefit" analysis).Spatial cueing produced reliable advantages for cued over uncued locations, in single and in multiple element displays. However, costs plus benefits were less marked for single displays. Thus, advance knowledge of the likely target location enhances performance also when there are no competing stimuli present in the visual field. But costs plus benefits are smaller because single target onsets at uncued locations summon attention in the same "automatic" fashion as peripheral cues. Peripheral cues trigger a rapid facilitatory component (automatic), fading out within 300 msec after cue onset. Facilitation is then maintained by a less effective mechanism (controlled). Central cues initiate only this second component. Sustained, controlled, orienting in response to central cues is interruptable by automatic orienting in response to uninformative peripheral flashes. Interruption also occurs when irrelevant flashes compete with peripheral cues. However, interference is less marked for the early automatic than for the following controlled orienting component. Indication of a second position (four-location display) to be most likely resulted in a marked sensitivity gain for this position, relative to uncued locations in a single cue condition. That is, attention could be simultaneously shared between two cued positions. For a luminance detection task (single target), cued locations showed no advantage in sensitivity; but for letter detection tasks (target plus distractors), there was a marked priming effect. That is, letter detection is capacity limited, whereas luminance detection is not. In all tasks, decision criteria are largely preset according to a-priori target probabilities assigned to particular locations, i.e. more liberal for cued and more conservative for uncued locations.

No description available.

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.

A rapid serial visual presentation task (RSVP) was combined with the 'inattention' paradigm (Mack & Rock, 1998) to investigate the effect of cognitive load on the detection of an unexpected stimulus. In addition, the detection of an unexpected stimulus presented in conjunction with a distractor item, rather than target, was also investigated. Seventy four students of the University of Canterbury participated in one of five experiments. Participants either performed a high cognitive load version of the RSVP task, selecting items on the basis of colour and semantic category, or a low cognitive load version selecting items on the basis of colour only. On the final frame of the fourth and critical trial, an unexpected stimulus appeared in conjunction with either a target or distractor item. The level of inattentional blindness to the unexpected stimulus was the result of interest. No effect of cognitive load or presentation partner was found. The implications of the results for the load theory of attention and cognitive control are discussed, along with the potential future uses of the developed method.

Thesis (M.A.)--York University, 2006. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 64-73). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19637