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This study investigated the effect of hearing six background noise conditions (silent baseline, pink noise, monologue, lively conversation, one-sided phone call, and cocktail noise) on acoustic measures of speech production during story retells in people with aphasia. Eleven individuals with aphasia and 11 age- and gender-matched control participants took part in the study. Participants heard the background noise conditions through open-back headphones while they retold six short stories. The examiner calculated mean and standard deviation of intensity, mean and standard deviation of fundamental frequency (F0), and speech rate in words per minute. A Matlab application that identified pauses (i.e., periods of silence greater than 200 ms) computed a speaking time ratio measure (i.e., time speaking versus time pausing). With the exception of the monologue and one-sided phone call condition, both people with aphasia and control participants significantly increase their intensity and F0 in the presence of background noise. Additionally, participants with aphasia have significantly lower speaking time ratios and speaking rates when compared to control participants. Participants make acoustic changes while hearing background noise; speech intensity rises in an effort to increase the signal-to-noise ratio, while mean F0 increases due to a presumed rise in subglottal pressure. Further research is suggested to investigate other acoustic differences, possibly at the segmental level, between speech produced in informational and energetic background noise.

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Our lives are dominated by a complex visual world, and spatially selective attention allows us to process only the most relevant information. Previous evidence suggests that if possible locations of stimulus presentation are delineated, attention affects processing in a spatially graded manner. This gradient is seen in both behavioral measures and in visual evoked potentials (VEPs). Stimuli presented close to cued regions elicit faster responses and larger VEPs than those presented farther away. However, both position in the visual field and allocation of attention may contribute to the observed gradients. These relative contributions can be distinguished by comparing responses on physically identical trials when attention is directed to locations at various distances from the stimuli. In the current study, participants attended to one of 12 squares arranged in a circle around fixation. Letters appeared individually, each in one of the squares; 80% were O’s (standards) and 20% were X’s (deviants). Participants were instructed to press a button when an X appeared at the attended location. The largest amplitude N1s (150-200 ms) were observed when participants attended to the location where a standard was presented. VEPs elicited by standards showed evidence of asymmetric attentional gradients. Specifically, the gradient of facilitation spread down more than up. Results also showed that attention had differential effects on the stages of processing indexed at specific time windows. These results confirm that attention can be applied to visual processing in a spatial gradient, reveal its asymmetric distribution, and elaborate on the timing of its selectivity.

Studies have shown that facial sexual dimorphism, ranging on a continuum from very feminine to very masculine, affects observers’ ratings of dominance and threat. These studies, however, have used forced-choice paradigms, in which a pair of faces that have been manipulated to appear more masculine (masculinized) and feminine (feminized) are presented side by side. They are susceptible to demand characteristics, situational aspects of the experiment which produce the desired outcome, because participants may be able to draw the conclusion that faces which appear more masculine should be rated as more dominant. In this dissertation, I evaluated whether facial sexual dimorphism affects observers' threat perceptions in a way that minimizes the confounds caused by demand characteristics. In Experiment 1 and Experiment 2, I presented observers with masculinized and feminized faces individually, rather than in pairs, and for an extremely brief duration (Experiment 1). I predicted that observers would assign higher dominance (Experiment 1) and threat ratings (Experiment 2) to masculinized faces. Observers assigned higher dominance (Experiment 1) and threat (Experiment 2) ratings to masculinized faces, even when they were presented individually, and for as little as 100 milliseconds (ms) (Experiment 1). This would suggest that they can appraise differences in facial sexual dimorphism following very brief exposure. I proceeded to evaluate the effects of facial sexual dimorphism on men’s selective attention, while reducing the effects of demand characteristics, by testing for an attentional bias towards task-irrelevant masculinized men’s faces. In Experiment 3, forty-five men completed a Posner Cueing Paradigm in which they classified shapes, presented either right or left of center screen after a masculinized or feminized man’s face was presented in either the same or opposite location. Participants were faster to classify the shape following the presentation of a masculine face; however, they were not faster when a masculine face cued target position. In Experiment 4, forty-four men completed a Flanker Task in which they judged letter orientation (i.e., upright or upside-down), while ignoring flanking faces. Participants’ RT was not affected by Morph Type (i.e., whether the face was masculinized, feminized or unmodified). In Experiment 5, forty-one men completed a Dot Probe Task. They were presented with two facial photographs of different Morph Types to the left and right of center screen. This was followed by the presentation of a target shape, in the location of one of the faces. Participants’ objective was to classify shape orientation. Facial sexual dimorphism did not affect participants' classification speed. In Experiment 6, I primed participants with images meant to induce fear or arousal before each trial of a Dot Probe Task. Following the presentation of a fear inducing picture, participants RT to classify shapes when a masculinized face cued target position did not differ from when a feminized face cued target position. The two different presentation times did not create different patterns of results, indicating that masculinized faces did not induce either a cueing or inhibitory affect. Overall, my results do not support my hypothesis that men selectively attend to masculinized faces when they are presented as irrelevant information. I conclude by discussing future directions for evaluating the effects that facial sexual dimorphism has on observers’ interpersonal perceptions of threat and dominance, while controlling for the effects of demand characteristics.

A number of studies have explored the impact of multitasking on specific cognitive skills, primarily with regard to non-media multitasking activities. While briefly addressing technology, its use in the modern era regarding media multitasking and its associated cognitive declines has not been extensively examined. Forty-nine participants were required to complete a series of cognitive tasks including the Stroop Color and Word Test and the Trail Making Test. Data were also collected for how often participants media multitask, the amount of technology they use, as well as other demographic variables. The goal of this study was to empirically examine the role of technology use and media multitasking on cognitive processes such as selective attention and task switching. It was hypothesized that those grouped as high media-multitaskers would predict a faster reaction time on the Stroop task, in line with previous literature by Cain & Mitroff (2011). Results showed a significant relationship exhibiting a negative correlation between the two factors, thereby accepting the hypothesis. Findings conclude with considerations for both the use and design of technological interfaces and devices as they apply to a variety of operational settings and high-tech environments.

Bilingualism has been studied extensively in multiple disciplines, yet we are still trying to figure out how exactly bilinguals think. A bilingual advantage has been observed in various experimental studies, but also has not been observed in many other studies. A bilingual advantage has been shown in tasks using selective attention. These tasks study the effects of language interference, where two types of interference are observed: interlingual (between-languages) and intralingual (within one language). This study examined language interference in Spanish-English bilinguals, using an auditory-visual simultaneous translation experimental setup. 16 college English monolinguals and 17 college Spanish-English bilinguals were tested. The task was to ignore the word in the headphones and to translate/repeat the word on the screen into English. Distractor words went to either the right, left, or both headphone ears. Subjects were given 72 words to translate, words were randomized, and ear of the distractor word was randomized. The monolingual group was not affected by any independent variables tested except screen word length. Bilinguals did worse when the word and audio were in Spanish, and when the word and audio were different words. No ear advantage was observed. Proficiency levels and first language had no effects on bilingual performance. More intralingual interference was observed for bilinguals only, no significant interference occurred for monolinguals. A slight bilingual advantage was found but not fully, because of the high load of the task and introduction of another language. In conclusion, bilinguals did not have a cognitive advantage in this experiment setup.

One means by which inhibitory control in selective attention may be studied is with the negative priming (NP) procedure. It is widely assumed that children are characterised by reduced capacity for inhibition (Diamond, 2002) and that inhibitory dysfunction is a key characteristic of children and adolescents with ADHD (Barkley, 1997). This should translate into reduced NP effects for these populations. In this dissertation, four studies using the NP procedure find no evidence for reduced inhibitory function in typical children or in adolescents with ADHD. Study 1 examined the magnitude of NP in children compared with adults. An important line of support for the idea that children suffer an inhibitory decrement has been based an empirical report suggesting that conceptual (identity or semantic) NP effects, assumed to reflect the by-product of distractor inhibition, while consistently found in adults are lacking in children (Tipper, Bourque, Anderson, & Brehaut, 1989). In Study 1, the opposite result was found. Study 2 compared NP effects between 7-year-old children and adults while replicating the respective methodologies of the only two studies to explore conceptual NP effects in developmental populations to date (Pritchard & Neumann, 2004, vs. Tipper et al., 1989) to determine the nature of the divergent results between these studies. In Study 2, it was found that distractor inhibition effects are comparable between children and adults when a NP task contains trials in which the distractor stimulus is consistently incongruent with the target stimulus, but that children may be more susceptible than adults to divide attention between target and distractor when a NP task contains a number of trials in which target selection difficulty is reduced. These are critical new findings, highlighting that reduced NP may often relate to methodological artifacts, and when considered in the light of current theories of NP, are also problematic for anti-inhibitory accounts of NP. Having distinguished more definitively the role of inhibition in developmental NP effects, Studies 3 and 4 explored whether the inhibitory process underpinning NP was implicated in young persons with ADHD. To date, evidence for NP in ADHD populations is equivocal. Study 3 found no evidence for a reduced NP effect in ADHD devoid of a corresponding diagnosis. Study 4 found that conduct and oppositional defiant disorders had the potential to confound the evaluation of NP in ADHD. Taken together, results in Studies 1 - 4 parallel very recent results in the literature on NP in older adults and adult psychopathology where presumed reductions of NP in these populations may also be accounted for by methodological artifacts (Buchner & Mayr, in press). It is concluded that NP may reflect a primitive and robust form of inhibitory processing, one that develops early and one that is often the last to deteriorate.

Human vision is remarkable. By limiting the main concentration of high-acuity photoreceptors to the eye's central fovea region, we efficiently view the world by redirecting the fovea between points of interest using eye movements called <em>saccades</em>. <br /><br /> Part I describes a saccadic vision system prototype design. The dual-resolution saccadic camera detects objects of interest in a scene by processing low-resolution image information; it then revisits salient regions in high-resolution. The end product is a dual-resolution image in which background information is displayed in low-resolution, and salient areas are captured in high-acuity. This lends to a resource-efficient active vision system. <br /><br />Part II describes CMOS image sensor designs for active vision. Specifically, this discussion focuses on methods to determine regions of interest and achieve high dynamic range on the sensor.

This thesis concerns selective attention in the context of the Stroop task (identify the colour) and Reverse Stroop task (identify the word). When a person is asked to select and identify one dimension of a bidimensional stimulus (e. g. , the word RED printed in green) the typical finding is that the word influences colour identification (i. e. , the Stroop effect) but the colour does not influence word identification (i. e. , no Reverse Stroop effect). A major account of performance in these tasks posits that one dimension interferes with the other only when a translation occurs (e. g. , Roelofs, <i>Psychological Review, 2003</i>; Sugg & McDonald, <i>Journal of Experimental Psychology: Human Perception & Performance, 1994</i>; Virzi & Egeth, <i>Memory & Cognition, 1985</i>). This translation assumption is implicit in virtually all work in the field. The first part of this thesis completely undermines the translation assumption. In a series of four experiments (two unique paradigms), I demonstrate that interference from the colour in a Reverse Stroop task occurs in the absence of a translation. The second part of this thesis contains two additional experiments designed to discriminate between translation effects and response conflict effects. The results of these experiments confirm that a translation was not required because no stimulus conflict effect, the most likely locus of a translation effect, was observed. However, response conflict effects were observed. The third part of this thesis implements a computational model based on the principle that the strength of association (Cohen, Dunbar, & McClelland, <i>Psychological Review, 1990</i>) between a specific stimulus and its response (Logan, </i>Psychological Review, 1988</i>) is important in determining the influence of the irrelevant dimension. This model has no translation mechanism. A final experiment was conducted to test this model; the model accounted for over 98% of the variance in RTs and 92% of the variance in interference and facilitation scores in both the Stroop and Reverse Stroop tasks independent of whether a translation was required.