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The development of reflexive and voluntary shifts of visual attention, as well as relations between the two forms of shifting was examined in three groups of children (5-, 7-, and 9-years-old), one group of young adults (24-years-old), and two groups of senior adults (young seniors: 69-years-old, old seniors: 81-years-old). The task entailed the detection and response to the presentation of a target (black dot) in one of four possible locations in the visual field. The dependent measure was reaction time (RT). The extent to which flash cues facilitated or inhibited reflexive orienting was determined through presentation of nonpredictive abrupt onset peripheral flash cues prior to the target. Arrow facilitation and inhibition was measured by shifts of attention initiated in response to predictive central arrow cues. Relations between reflexive and voluntary shifts of attention were gauged by the degree to which flash and arrow facilitation and inhibition were observed in response to the presentation of both arrow and flash cues together in one trial. Conditions varied with regard to the validity of the location cues (accurate or inaccurate information regarding the location of the subsequent target) and the length of the interval between the cue and the target (SOA: 185 or 875 ms). All age groups demonstrated flash facilitation with the flash cue alone, demonstrating similar patterns of reflexive orienting across the lifespan. However, the three groups of children demonstrated the largest flash cue effects suggesting that they had the most difficulty ignoring the nonpredictive flash cues. With the arrow cue alone, young adults, and young and old senior adults were more efficient (faster RTs) in their execution of voluntary shifts, however, all age groups utilized the arrow cues to orient attention strategically and in doing so experienced similar patterns of arrow facilitation. When both flash and arrow cues were presented together, the 9-year-old children, young

Twelve spatial-cueing experiments examined stimulus-driven and goal-driven control of visual attention orienting under multiple-cue conditions. Spatial cueing involves presenting a cue at a potential target location before a target appears in a display, and measuring the cue's effect on responses to the target stimulus. Under certain conditions, a cue that appears abruptly in a display (direct cue) can speed responses to a target appearing at the previously cued location relative to other uncued locations (called the cue effect). The experiments in this dissertation used a new multiple-cue procedure to decouple the effects of stimulus-driven and goal-driven processes on the control of attention. This technique involved simultaneously presenting a red direct cue (Unique Cue) that was highly predictive of the target location along with multiple grey direct cues (Standard Cues) that were not predictive of the target location. The basic finding was that while cue effects occurred at all cued locations, they were significantly larger at the Unique-Cue location. This finding was interpreted as evidence for stimulus-driven cue effects at all cued locations with additional goal-driven cue effects at the Unique-Cue location. Further experiments showed that Standard-Cue effects could occur independently at multiple locations, that they seemed to involve a sensory-based interaction between the cues and the target, and that they were mediated by a limitedcapacity tracking mechanism. In addition, Unique-Cue effects were found to be the product of goal-driven operations, to interact with Standard-Cue effects, and to involve inhibited processing at unattended locations. These results were explained in terms of a filter-based model of attention control that assigns priority to potential attention-shift destinations. According to this model, stimulus-driven and goal-driven factors generate signals (activity distributions) that drive a filter to open an attention channel at the highest priority location by suppressing the signals at other locations. The final experiments confirmed the central assumptions of this model by providing evidence that the prioritydestination process was sufficient to produce cue effects independent of attention, and that attending to a location involved a suppression of processing at unattended locations. The implications of this model for the larger visual attention literature were also discussed.

To date, research on cognitive aging has treated attention as a unitary resource that operates according to a single mechanism of top-down selection. However, contemporary theoretical models of attention propose that it is a distributed resource, embedded in distinct cortical subsystems, and operates in a manner that reflects the properties of those subsystems. For instance, perceptual attention is thought to originate in posterior sensory subsystems and filter competing unattended input prior to encoding, resulting in early selection of attended information. Executive attention, by contrast, is thought to originate in frontal control subsystems and filter unattended input after encoding, resulting in late selection of attended information. Guided by a distributed resource model, the work described here focuses on how healthy advanced aging influences early selection mechanisms embedded in posterior subsystems, perceptual encoding, and the relationship with frontal subsystems mediating late selection. To examine perceptual attention in isolation, object discrimination tasks were devised in which perceptual competition between repeated objects was manipulated while holding demand on executive control constant. Cortical mechanisms of early selection were probed using functional magnetic resonance imaging (fMRI) indices of neural response and adaptation. Evidence of an age-related impairment in early selection was detected across two fMRI experiments. Unlike young adults, unattended objects not only interfered with perceptual encoding in older adults, but were co-encoded along with the contents of attended input. Age impairments in early selection were also associated with greater reliance on frontally-mediated late selection resources, and, reduced functional connectivity with basal forebrain nuclei. In sum, the results indicate that with increasing age, frontal control subsystems become increasingly encumbered with compensatory redistribution of function from the perceptual cortices, possibly due to loss of central cholinergic integrity. Many well-described age-related deficits of executive attention may therefore represent a consequence of impaired early selection, rather than its cause.

The purpose of this study was to compare two conflicting theoretical perspectives on the relationship between intelligence and sustained attention. The cognitive resources theory assumes that lower IQ subjects are required to allocate greater amounts of their limited attentional resources during information-processing tasks than higher IQ subjects. The arousal theory assumes that there is an optimal level of arousal associated with task performance, and that an increase or decrease in arousal produces impairment in performance. Additionally the arousal theory predicts that increased time on task leads to a decrement in arousal as a function of IQ levels. Signal detection theory applications were used to operationalize and compare the two theories. Specifically, the signal detection parameters of sensory acuity ( d’), the decision criterion (a), correct detections, and false alarms were used to determine subject performance across three time periods ( 2, 4, and 6 mm.) on a visual continuous performance task. Twenty-nine teacher-nominated at-risk for learning difficulties and twenty-nine normally achieving kindergarten students were adminstered the Stanford-Binet:Fourth Edition (SB:FE) and the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI.R), as well as the Gordon Diagnostic System (GDS) Vigilance Task. The GDS is a standardized behaviour-based measure of sustained attention. The results of this study were interpreted as suggesting that ability group differences reflect attentional capacity. Two findings were important in this interpretation. First, regardless of IQ, the groups varied on the signal detection discrimination index. Second, these measures did not vary over time in either group. Thus, the arousal theory was not supported. IQ and attention intercorrelation patterns were higher for the at-risk group compared to the normally achieving group. Exploratory maximum-likelihood factor analyses indicated that intelligence plays a greater role in relation to vigilance for the at-risk for learning difficulties group than the normal achieving group.

This thesis claims that metacontrast unmasking is influenced by attentional orienting towards the target location. This view is contrary to Breitmeyer, Rudd and Dunn (1981), who proposed that metacontrast unmasking is the product of inhibition of the primary mask's transient signal by the sustained signal of a secondary mask. A series of experiments demonstrate the thesis using a task in which observers discriminated the missing corner of a target diamond. Experiments 1 and 2 replicated metacontrast masking and unmasking, respectively, experiment 3 illustrated that contour proximity had no influences on unmasking, contrary to dual-channel inhibition theory. Experiments 4 and 5 indicated that metacontrast unmasking was influenced by spatial orienting. We propose an addition of attention to dual-channel theory as it is incomplete with regards to metacontrast unmasking.

Through employing a two-faceted approach to the sociological study of Attention Deficit- Hyperactivity Disorder (ADHD), this thesis seeks to further the study of this mental illness and also to elucidate new methodological directions for the sociology of similar phenomena. Past approaches in the sociology of mental disorder have considerable merit, but may also be limited in the type of analyses they offer. One particular limitation concerns sociological accounts of mental illness that portray the meaning of such illnesses as unified and that this unification results from the collusion of special interests. Sociologists who address mental illnesses as social problems, for example, appear wont to portray such illnesses as social constructions which arise from specific agents of labeling. With regard to ADHD, previous sociological accounts often make a case for the rhetorical and political power of government agencies, medical practitioners, and pharmaceutical companies. Though such agents are certainly influential in shaping public conceptions of ADHD, this thesis demonstrates that ADHD is interpreted in various ways. These assertions are supported through the analysis of two different data sources: 1) textual data; and 2) interview data. The textual data for the first part of the thesis comprises the subject matter for a genealogy of ADHD. Through examining past and contemporary texts that frame this disorder, including medical journal articles, medical manuals, popular writings, and parental guidebooks, the author argues that the historical and current discussions of ADHD are replete with differing interpretations of the causes and treatments for ADHD. These ADHD discourses, as they are seen through written accounts, offer a variety of perspectives towards the disorder, drawing from many opposing schools of thought. Most notable in this regard are psychodynamic and neurological approaches to ADHD. I argue that even though the neurological perspective towards ADHD appears to be the most dominant in diagnosing and treating the disorder, it is far from monolithic. ' The second part of the thesis draws upon interview data from sixty-two respondents associated with cases of ADHD: twenty clinicians, twenty parents, and twenty-two teachers. Each of these groups of respondents were asked questions designed to solicit their subjective experiences with the disorder, including how they perceived ADHD children and their sources of ADHD knowledge. The analysis of such data is placed against the backdrop of the genealogical part of the thesis. Responses from participants are examined as reflecting ADHD discourses. Some respondents, for example, demonstrate a commitment to neurological perspectives towards ADHD, while others gravitate towards psychodynamic or combined understandings of the disorder. Through combining these two data sources, this thesis analyzes ADHD discourses that give rise to conceptions of the disorder and shows how these discourses influence attitudes and actions towards ADHD. By giving less salience to the collusive relationships between government agencies, medical practitioners, and pharmaceutical companies, and by putting more focus on the relationship between the three major groupings directly involved in the ADHD experience—clinicians, teachers, and parents—this thesis furthers the sociological study of ADHD.

This study investigated the influence of training on interference in younger and older adults using the Eriksen flanker task. Does flanker interference differ with age and, as practice progresses, does the pattern of interference change? Younger and older adults were given five sessions of training on the flanker task over five successive days. On each trial, participants saw a central target letter flanked vertically by two flanker letters; the flankers could be either compatible or incompatible with the target. Participants were to respond to the identity of the central letter, ignoring the flanker letters. Although older adults were slower overall than younger adults in responding, the two groups showed virtually identical overall benefits from practice. Critically, the two age groups showed equivalent and constant interference due to incompatible flankers at all stages of practice. In the flanker paradigm, aging slows response execution without affecting attention within a trial or learning across trials.