Task variety during training was manipulated to assess residual effects on skill acquisition during subsequent transfer to a novel perceptual motor task. The task involved tracing a four-point star pattern displayed on a personal computer with a "mouse," while receiving variation in visual feedback from the CRT display. Variety during training involved two cases of abnormal visual feedback (left-right reversal and 90 degree tilt) Task variety (i.e., visual feedback) was manipulated and counterbalanced in four levels: alternated variety (trial by trial), blocked variety (in five trial sets), no variety (i.e., one type of feedback), and a control condition that trained with no displacement (normal feedback). All groups were tested with inverted feedback (up-down reversal) as the novel transfer task. The number of trials was fixed as 10 trials each for the training and transfer phases. Dependent measures were RMS error and time to completion. During training, significant differences revealed that the alternated variety condition was the most difficult to learn, followed by blocked variety, no variety, and the control condition. The two variety groups did not differ in performance on the first transfer trial. The alternated group traced faster on transfer trials two through five, however, the blocked group was more accurate. The no variety group performed superior to the two variety conditions combined, on all of the first five transfer trials. Although the control group performed with significantly fewer errors than the treatment conditions on the first transfer trial, the treatment groups performed significantly faster than the control group on transfer trials two through five. These results indicate that task variety under these circumstances was generally no advantage to transfer performance. It is speculated that variation may indeed improve transfer with longer training periods.

Five experiments, involving 456 subjects, were conducted to determine the influence of certain stimulus characteristics of the Müller-Lyer figure on the magnitude of this illusion and on the decrement of the illusion which occurs with practice. The results showed that the magnitude of the illusion is directly related to the length of the oblique lines and inversely related to the angle between the obliques and the prominence of the horizontal line. Reducing the angle between the obliques and reducing the prominence of the horizontal line caused the illusion to decrease more rapidly over a series of 100 trials. The final experiment provided evidence consistent with the interpretation that changes in attention may be responsible for the practice decrement. These results are discussed in terms of perceptual learning. / Thesis / Doctor of Philosophy (PhD)

The purpose of the study was to explore perceptual-motor differences between blind and sighted adults from a neuropsychological perspective, and to analyze differences within the blind group. Perceptual-motor abilities were examined using the Comprehensive Vocational Evaluation System (CVES), a vocational rehabilitation and neuropsychological battery designed for use with blind populations. The data were processed using Analysis of Covariance. Results showed that sighted persons had better motor abilities, while persons with blindness were more skilled at haptic identification of shape and texture. Analysis within the blind group showed that texture identification skills are better when blindness occurs earlier in life and to the extent that the blindness is total. Later onset blindness and the retention of some functional vision may not lead to a refocusing of attentional states necessary to develop haptic images. New neural connections may develop in persons with congenital/total blindness, a hypothesis in line with recent neuroradiological findings that occipital lobe activation occurs when congenitally blind individuals engage in tactile processing tasks. One implication of the findings is that teaching individuals who retain some functional vision to read Braille is probably counterproductive. These individuals would be better served by learning to use a CCTV and large print books. Future researchers should examine blindness from a multivariate perspective, examining subsets of blind groups based on age at onset, visual status, and other pertinent variables. Other implications are discussed and recommendations for future research are provided.

Previous research shows that social biases, such as pro-White racial bias, can influence a person's decisions and behaviors (Correll et al. 2007; Mekawi & Bresin, 2015). Studies also suggest that social biases may influence basic functions like visual perception (Cesario & Navarrete, 2014); however, few studies have examined the relationship between visual perceptions and threat (Cesario, Placks, Hagiwara, Navarrete, & Higgins, 2010; Todd, Thiem, & Neel, 2016). The current research aims to investigate whether implicit pro-White preference can influence basic functions like visual perception. A secondary aim of this study is to examine the role of threat in this relationship. To test, White male and female participants (N= 29) were asked to complete distance estimates to either a Black or White male experimenter. It was hypothesized that participants would judge the distance to the Black confederate as closer compared to those who estimate the distance to a White confederate. The results marginally supported the idea that participants’ distance judgements were influenced by the experimenter’s race, such that the Black experimenter was viewed as closer when compared to the White experimenter. However, results showed that implicit racial attitudes did not influence distance estimations, but explicit bias did. Fully powered follow-up studies will be conducted to further examine these hypotheses and investigate whether a type one error was present.

Little is known about how healthy aging impacts figure-ground (FG) perception, which is critical in organizing complex visual input into coherent figures. Inhibitory-suppression is thought to be critical in resolution between competing FG interpretations. Given the age-related changes to inhibitory cortical mechanisms, my thesis investigated the hypothesis that processes underlying FG organization are impaired in aging. We explored the effects of age on the convexity context effect (CCE): the tendency to perceive convex regions as figural [i.e., P(Convex=Figure)] increases with surrounding convex and concave regions. In Chapter 2, we observed that adding context by increasing region number, increased P(Convex=Figure) in younger and older observers, but this CCE was significantly reduced in older adults. Reducing competition between perceptual interpretations by heterogeneously colouring convex regions, thereby invalidating the alternative {Concave=Figure} stimulus interpretation, greatly increased P(Convex=Figure) in older observers. These results supported the notion that aging impairs FG organization, particularly in relatively high competition contexts. In Chapter 3, we explored the possibility that reduced presumption of depth in our stimuli might explain the reduced the CCE in older observers by adding texture motion to region fills consistent with depth in the stimulus. The results were inconsistent with the hypothesis, but supported the reduced inhibitory-suppression hypothesis of the age effect. In Chapter 4, we explored the neural activation associated with the processing mechanisms underlying the resolution of FG competition. The results indicated that the N250 in younger observers but not older observers is sensitive to high vs. low competition contexts. Furthermore, individual differences in this N250-competition effect were correlated with the behavioural effect of competition. Our findings are consistent with the hypothesis that the processing underlying FG organization is impaired in senescence, which may stem from reduced efficacy of the neural architecture supporting this ability. Various implications of this work are discussed. / Dissertation / Doctor of Philosophy (PhD)

This study investigated whether perceptual fluency could affect duration judgments. Fluency refers to levels of subjective ease, in which stimuli can be processed (Lanska, Olds, & Westerman, 2014). The study was conducted with experimental within group factorial design. Visual stimuli were selected from Snodgrass and Vanderwarts (1980) standardized set of 260 pictures. Pairs were made with low and high levels of complexity. Duration was about 1000 milliseconds with .10 variations. 1/3 of pairs were without variation. Participants were asked to judge which image was presented for longest time. Total amount of participants was 37. Main hypothesis was that low levels of complexity would be judged, to a greater frequency, as having been presented for longer duration. Observed mean (M= 20.27, SD = 2.90) was slightly lower than level of chance (M = 21) and the difference was non significant, t(36) = -1.53, p > .13. The null hypothesis was not rejected.

Perceptual centres, or P-centres, represent the perceptual moments of occurrence of acoustic signals - the 'beat' of a sound. P-centres underlie the perception and production of rhythm in perceptually regular speech sequences. P-centres have been model ed both in speech and non speech (music) domains. The three aims of this thesis were tost out current P-centre models to determine which best accounted for the experimental data b)to identify a candidate parameter to map P-centres onto (a local approach) as opposed to the previous global models which rely upon the whole signal to determine the P-centrethe final aim was to develop a model of P-centre location which could be applied to speech and non speech signals. The first aim was investigated by a series of experiments in whicha)speech from different speakers was nvestigated to determine whether different models could account for variation between speakersb)whether rendenng the amplitude time plot of a speech signal affects the P-centre of the signa whether increasing the amplitude at the offset of a speech signal alters P-centres in the production and perception of speech. The second aim was carried out by manipulating the rise time of different speech signals to determine whether the P-centre was affected, and whether the type of speech sound ramped affected the P-centre shift1 manipulating the rise time and decay time of a synthetic vowel to determine whether the onset alteration was had more affect on P-centre than the offset manipulationnd whether the duration of a vowel affected the P-centre, if other attributes (amplitude, spectral contents) were held constant. The third aim - modelling P-centres - was based on these results. The Frequency dependent Amplitude Increase Model of P-centre location (FAIM) was developed using a modelling protocol, the APU GammaTone Flterbank and the speech from different speakers. The P-centres of the stimuli corpus were highly predicted by attributes of the increase in amplitude within one output channel of the filterbank. When this was used to make predictions of the P-centres for all the stimuli used in the thesis, 85°c of the observed variance was accounted for. The FAIM approach combines aspects of previous speech and non speech models (Gordon 1987, Marcus 1981, Vos and Rasch 1981). P-centre were thus modelled n a non speech specific, local manner.

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We examined age-related differences in figure-ground perception by exploring the effect of age on Convexity Context Effects (CCE; Peterson & Salvagio, 2008). Experiment 1, using Peterson and Salvagio's procedure and black and white stimuli consisting of 2 to 8 alternating concave and convex regions, established that older adults exhibited reduced CCEs compared to younger adults. Experiments 2 and 3 demonstrated that this age difference was found at various stimulus durations and sizes. Experiment 4 compared CCEs obtained with achromatic stimuli, in which the alternating convex and concave regions were each all black or all white, and chromatic stimuli in which the concave regions were homogeneous in color but the convex regions varied in color. We found that the difference between CCEs measured with achromatic and colored stimuli was larger in older than in younger adults. Our results are consistent with the hypothesis that the senescent visual system is less able to resolve the competition among various perceptual interpretations of the figure-ground relations among stimulus regions.

The main aim of this research is to develop a list of principles relevant to the design of neighbourhoods and in particular neighbourhood centres in Tehran. The study embodies two main phases, a literature review and a survey. During the literature review various dimensions of a neighbourhood centre are explored among both 'prescriptive' and 'explanatory' theories in architecture and urban design. Attempts are made to extract the essence and concepts of individual projects among the prescriptive resources, while the investigations of explanatory resources are focused on finding concepts and ideas which are applicable to design. The characteristics of neighbourhood centres are then classified into three categories called functional, perceptual and operational. These categories embody different sections which are separately studied among the literature and design principles are derived out of the writings and presented at the end of each section. Finally, a provisional list of principles is developed as the result of the literature review. The survey is designed to examine the above principles in the real world in two contrasting neighbourhood centres in Tehran. Face-to-face interviews with the residents of the neighbourhoods, together with the observation of cases, comprise the research instruments. The interviews are based on qualitative open-ended questions in order to find out the characteristics of the centres which the residents mostly appreciated or disliked. A checklist is formulated to explore design factors out of the survey responses. The design principles resulting from the survey are then compared with the initial list. The outcome of the research is the final list of generic principles which draws together the results of the literature investigation and the survey. These principles are primarily aimed at those directly engaged in the design of neighbourhood centres such as architects and urban designers. It also includes information for the management body of the centres. For the ease of users the principles are classified into ten sections under the three main categories mentioned above. Along with the above results, there are some secondary findings about the respondents' differences in perception and evaluation of their neighbourhood centre which are presented in the concluding chapter of the thesis. The study intends to decrease the gap between theoretical research and practical work by presenting design principles, extracted from the conceptual theories, that can be easily used by designers. Based on both theoretical and empirical approaches, it also helps to draw attention to the importance of neighbourhood centres in enhancing the quality of day-to-day lives of the city inhabitants.