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The development of perceptual-cognitive processes during infancy has been traditionally studied using visual habituation and paired-comparison techniques. There has been extensive work within the field of infant attention that has focused on the development of visual attention. Within this field, it has been well established that there are two distinct classifications of infants' visual behavior; infants with short visual fixations who perform well in a recognition task following familiarization and infants with long visual fixation with impaired performance. There are two hypotheses for the differences underlying these groups. First, that visual fixation duration is reflective of the speed of information processing such that long-looking infants process information more slowly than short-looking infants. The second hypothesis is that infants who are long-looking have difficulty disengaging and shifting their attention to another location. There has not been any work exploring how these differences manifest themselves in other modalities. Thus, this project has three purposes: (1) to explore whether group differences emerge in an auditory recognition task similar to those found in the visual recognition phase of the paired-comparison task, (2) to better understand how performance differences in the visual task correspond to any observed differences in an auditory task, and (3) to identify any potential mechanisms which may account for the observed differences in group performance on an auditory task. / Ph. D.

The present thesis set out to investigate how sensory modality and spatial presentation influence visual and auditory duration judgments in the millisecond range. The effects of modality and spatial location were explored by considering right and left side presentations of mixed or blocked visual and auditory stimuli. Several studies have shown that perceived duration of a stimulus can be affected by various extra-temporal factors such as modality and spatial position. Auditory stimuli lead to more precise duration judgments than visual stimuli and often last subjectively longer than visual stimuli of equal duration. The circumstances under which these modality differences occur are not clear yet. Recent studies indicated an interaction between temporal and spatial processing. Overestimation of durations was associated with right side presentation of visual stimuli, underestimation with left side presentation. However, the effect of spatial presentation has not been explored in the auditory temporal judgments. Furthermore, there is a debate concerning the mechanisms underlying processing of visual and auditory intervals with some researchers supporting the view that there is a central, amodal temporal mechanism and others arguing in favour of distinct, modality specific temporal mechanisms. The above issues were examined in a series of experiments using the duration discrimination paradigm. Processing demands where varied between experiments by varying the number of stimuli positions and the way that different modality trials were presented (mixed or blocked). Across all experiments we found no effect of location either in visual or auditory domain. However, in experiments in which different modality trials were intermixed, participants in the visual versions of the task tended to overestimate durations of comparison stimuli that were presented at different locations to the standard stimuli. In such conditions, visual stimuli were also judged to be longer than the auditory. However, when the location of the comparison stimulus was at the same side as the standard a reverse effect was observed. These findings call into question an influence of the position per se on temporal judgments as the visual duration judgments were affected rather by the change of the location. Auditory judgments were not affected by location manipulations, suggesting that different mechanisms might underlie visual and auditory temporal processing. Based on these results, we propose the existence of an error-correction mechanism, according to which a specific duration is added in order to compensate for the loss of time caused by spatial attention shifts. This mechanism is revealed under some circumstances (such as mixed modality) where it is over-activated, resulting into a systematic bias. This work has important implications for the contemporary research in time perception as it is shedding new light on the possible ways that a unified experience of timing arises from modally and spatially specific temporal mechanisms.

Thesis (B.Sc)--University of Hong Kong, 2000. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, May 10, 2000." Also available in print.

Thesis--Göteberg. / Extra t.p. with thesis statement inserted. Includes bibliographical references (p. 186-195).

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. "These investigations were supported in part by the National Institute on Deafness and Communication Disorders ... and the National Institute of General Medical Sciences"--P. viii. Includes bibliographical references (leaves 142-152). Also available for download via the World Wide Web; free to University of Oregon users.

Perceptual bi/multi-stability—the phenomenon in which perceptual awareness switches between alternative interpretations of a stimulus—can be elicited by a large range of stimuli. The phenomenon is explored in vision, audition, touch, and even olfaction. The degree to which perceptual switching across visual and auditory bi/multi-stable paradigms depends on common or separate mechanisms remains unanswered. This main question was addressed in the current work by using four ambiguous tasks that give rise to bi/multi-stability and which are thought to involve rivalry at different levels of cognitive processing: auditory streaming and ambiguous-structure-from-motion (low- level tasks), and verbal transformations and ambiguous figures (high-level tasks). It was also investigated if individual differences in executive function (inhibitory control and set-shifting), creativity and personality traits have common relationships with perceptual switching in adults and children. A series of five experiments (four studies) were conducted. In Study 1 (two experiments), perceptual switching behaviour of adult participants was examined in the four perceptual tasks mentioned above. In Experiment 1, participants reported higher switching rates for the ambiguous figure and verbal transformations than for ambiguous motion and auditory streaming. However, in Experiment 2 participants had a higher switching rate in verbal transformations than in auditory streaming, while the switching rates in the two visual tasks did not differ significantly. The correlations between visual and auditory switching rates were similarly inconclusive: in Experiment 1, no cross-modal correlations emerged, while in Experiment 2 there were correlations between ambiguous figure and verbal transformations and between ambiguous motion and verbal transformation. Furthermore, inhibitory control, set-shifting, and creativity correlated with perceptual ii switching rates in some of the perceptual tasks, although not in a consistent manner. In Study 2, the development of perceptual switching was investigated in children in the same four tasks used in Study 1. Findings showed that the number of switches increased with age in all four perceptual tasks, indicating general maturational developments. Executive functions and creativity were not associated with the ongoing perceptual switching, which was similar to what was found in adults. In Study 3, a neuroscientific perturbation approach was used to investigate whether the superior parietal cortex is causally involved in both visual and auditory multistability as a top-down mechanism. Transcranial magnetic stimulation on the anterior and posterior superior parietal cortex did not increase or decrease the median phase durations in response to the ambiguous motion and auditory streaming. These regions were not causally involved in either visual or auditory multistability. Perceptual switching across modalities correlated nevertheless, indicating common perceptual mechanisms. In Study 4, the effects of attentional control and instructions were further investigated in ambiguous motion and auditory streaming. There were strong correlations between perceptual switching in the two tasks, confirming that there are common mechanisms. However, the effects of voluntary attention did not explain the commonalities found. Possibly the commonalities found reflect similar functionalities at more low-level sensorial mechanisms. In conclusion, perceptual switching in vision and audition share common mechanisms. These commonalities do not seem to be due to the same neural underpinning in parietal cortex. Moreover, attentional control does not explain the commonalities found, indicating a more low-level common mechanism or functionality. Perceptual switching across all ages is task-specific, more than modality specific. No central influence of inhibitory control and creativity was constantly associated with perceptual switching regardless of task/modality, supporting the distributed mechanisms hypothesis.

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Sensory substitution devices are a non-invasive visual prostheses that use sound or touch to aid functioning in the blind. Algorithms informed by natural crossmodal correspondences convert and transmit sensory information attributed to an impaired modality back to the user via an unimpaired modality and utilise multisensory networks to activate visual areas of cortex. While behavioural success has been demonstrated in non-visual tasks suing SSDs how they utilise a metamodal brain, organised for function is still a question in research. While imaging studies have shown activation of visual cortex in trained users it is likely that naïve users rely on auditory characteristics of the output signal for functionality and that it is perceptual learning that facilitates crossmodal plasticity. In this thesis I investigated visual-to-auditory sensory substitution in naïve sighted users to assess whether signal complexity and processing in the auditory system facilitates and limits simple recognition tasks. In four experiments evaluating; signal complexity, object resolution, harmonic interference and information load I demonstrate above chance performance in naïve users in all tasks, an increase in generalized learning, limitations in recognition due to principles of auditory scene analysis and capacity limits that hinder performance. Results are looked at from both theoretical and applied perspectives with solutions designed to further inform theory on a multisensory perceptual brain and provide effective training to aid visual rehabilitation.

While consumers are shifting towards online clothing purchases globally, South Africa, a developing economy with well-developed infrastructure, is lagging in this regard. This research highlights significant drawbacks that may jeopardise the growth of online shopping despite the multiple advantages that consumers and retailers could benefit from. The key to the issue is that a consumer is not physically present in the store, and that online consumers’ experiences are limited to the technological capabilities of existing digital platforms. Inevitably, consumers’ online experiences would be framed in terms of what they are accustomed to in physical stores, therefore, sensory-rich, captivating environments. Creating well-designed mobile phone applications, which incorporate multiple sensory cues, is consequently crucial to capture online shoppers’ attention, and to ensure online retailers’ success. Millennials, the largest generational consumer group presently worldwide, is particularly important to online clothing retailers due to their potential buying power, interest in clothing as a product category, as well as their extensive use of mobile technologies. This study was conducted in the context of an emerging economy and aimed to examine the real-time influence of visual and auditory cues - that could viably be incorporated with available technology into a custom-designed mobile phone application for a fictitious clothing retailer - on millennials’ sensory experience and purchase intentions when purchasing clothing online. Clothing is a rather complex product category where sensory cues in combination with a range of extrinsic and intrinsic product characteristics are highly relevant during product evaluation. To accommodate the realities of physical store experience, three moderating influences were examined within the chosen stimulus-organism-response (S-O-R) theoretical framework, namely, the effects of telepresence, customisation, and available clothing product information. A positivistic, quantitative, descripto-explanatory, cross-sectional study was designed, presenting a two-phase electronic survey. It presented a vignette design that exposed respondents to the capabilities of the custom-designed mobile phone application before completing a questionnaire. Convenient, online snowball sampling through social media produced a sample size of 842 millennial respondents, from the Gauteng province in South Africa. Statistical analyses included descriptive statistics, covariance-based structural equation modelling, moderation analyses, and multivariate analyses of variance. The findings confirmed the significant influence of visual and auditory cues on millennials’ online sensory experience, as well as the significant positive moderating role of telepresence and customisation respectively, in facilitating millennials’ purchase intentions when shopping online. Failure to affirm the moderating influence of product information on consumers' purchase intentions, may be ascribed to the absence of intrinsic product characteristics such as fit, feel, and comfort, which are highly relevant but can not yet be incorporated into an online platform. This elevates the importance of how existing sensory cues are presented, and how they could counteract shortcomings of online shopping encounters. Considering what has been achieved by the gaming industry, in terms of visuals and sound when playing online, retail store mobile phone applications have not yet optimised their potential. Gender differences in online shoppers’ sensory experience, purchase intention and use of product information suggest that millennial men's purchase decisions may be more rational inclined compared to their female counterparts. The study indicates how millennials’ online clothing purchase endeavours could be enhanced in developing countries like South Africa, where online shopping has not yet reached first-world levels. Empirical evidence is also provided on how online sensory experiences and effective mobile phone app designs could enhance clothing retailers’ online apps to boost online sales. / Thesis (PhD)--University of Pretoria, 2021. / Gordon Institute of Business Science (GIBS) / PhD / Unrestricted