For the past few years, virtual environments (VEs) have gained broad attention from both scholarly and practitioner communities. However, in spite of intense and widespread efforts, most VE-related research has focused on the technical aspects of applications, and the necessary theoretical framework to assess the quality of interfaces and designs has not yet been fully developed. This research, as a response to such challenges, concerns the usability of three-dimensional VEs. More specifically, this study aims to investigate the effects of wayfinding affordance design on users’ task performance and perceptual experience in 3D desktop VEs. For this purpose, four different wayfinding affordance conditions were set up: Fixed Detached Affordance Cues (FDAC) condition, Switchable Detached Affordance Cues (SDAC) condition, Portable Embedded Affordance Cues (PEAC) condition and Fixed Embedded Affordance Cues (FEAC) condition. Maps and directional cues were employed to implement wayfinding affordance. The results show that the design of wayfinding affordance has significant effects on users’ perceptual experience as well as their task performance. Task performance was significantly better where the maps and directional cues were provided independently from the VE interfaces (FDAC, SDAC). With regard to perceptual experience, the effect was significant only in simple environments. In these environments, the fixed and, therefore, stable interfaces (FEAC, FDAC) were found to provide a better sense of presence for users whereas the manipulative interfaces (PEAC, SDAC) offered a greater state of playfulness. The research findings also indicated that the design of 3D interfaces had a greater impact on non-expert users than on expert users. / text

Bandwidth-intensive video streaming applications occupy an overwhelming fraction of bandwidth-limited wireless network traffic. Compressed video data are highly structured and the psycho-visual perception of distortions and losses closely depends on that structure. This dissertation exploits the inherent video data structure to develop perceptually-optimized transmission paradigms at different protocol layers that improve video quality of experience, introduce error resilience, and enable supporting more video users. First, we consider the problem of network-wide perceptual quality optimization whereby different video users with (possibly different) real-time delay constraints are sharing wireless channel resources. Due to the inherently stochastic nature of wireless fading channels, we provide statistical delay guarantees using the theory of effective capacity. We derive the resource allocation policy that maximizes the sum video quality and show that the optimal operating point per user is such that the rate-distortion slope is the inverse of the supported video source rate per unit bandwidth, termed source spectral efficiency. We further propose a scheduling policy that maximizes the number of scheduled users that meet their QoS requirement. Next, we develop user-level perceptual quality optimization techniques for non-scalable video streams. For non-scalable videos, we estimate packet loss visibility through a generalized linear model and use for prioritized packet delivery. We solve the problem of mapping video packets to MIMO subchannels and adapting per-stream rates to maximize the total perceptual value of successfully delivered packets per unit time. We show that the solution enables jointly reaping gains in terms of improved video quality and lower latency. Optimized packet-stream mapping enables transmission of more relevant packets over more reliable streams while unequal modulation opportunistically increases the transmission rate on the stronger streams to enable low latency delivery of high priority packets. Finally, we develop user-level perceptual quality optimization techniques for scalable video streams. We propose online learning of the mapping between packet losses and quality degradation using nonparametric regression. This quality-loss mapping is subsequently used to provide unequal error protection for different video layers with perceptual quality guarantees. Channel-aware scalable codec adaptation and buffer management policies simultaneously ensure continuous high-quality playback. Across the various contributions, analytic results as well as video transmission simulations demonstrate the value of perceptual optimization in improving video quality and capacity. / text

published_or_final_version / Psychology / Master / Master of Social Sciences

published_or_final_version / Psychology / Master / Master of Philosophy

No description available.

The aim of this project was to study the phenomenology of auditory hallucinations in Indians. The sample investigated consisted of thirty adult Indian males domiciled in the Durban area, attending neuroclinics, who had been diagnosed as having suffered from a psychosis and who had experienced auditory hallucinations. The patients were examined by the author and in addition relevant data was extracted from their case files. This included religion, previous diagnosis, age at onset of illness and present age, mother tongue, language of daily usage, language of hallucinations, source of hallucinations, comprehensibi1ity of hallucinations, content of hallucinations, patient's initial reaction to hallucinations, time when hallucinations were experienced, media of transmission, direction of voices and whether the patient had consulted a traditional healer. The findings were that a significant majority of patients: 1) described their hallucinations as being voices coming from supernatural beings (84%). 2) did not attribute their hallucinations to being voices belonging to their deceased ancestors (88%). 3) did not attribute their hallucinations to voices which were being relayed by technical transmitting apparatuses (88%) . 4) diagnosed as suffering from schizophrenia initially, found their hallucinations to be distressful (89%) whereas 80% of the patients diagnosed as suffering from manic depressive psychosis found their hallucinations to be pleasant. 5) did not ascribe their hallucinations to animals (100%). 6) had visited a traditional healer (100%). Hallucinations were generally thought by the majority of patients to have occurred as a result of being possessed by spirits and that the possession had occurred following some "evil" done to them by enemies, rivals, or other persons who wanted the patient to come to harm. Their belief in spirits was derived both from religion and from folk-lore. Its connection with auditory hallucinations arose from the notion that evil spirits can invade human beings causing abnormal behaviour and also symptoms of mental illness including auditory hallucinations. All the patients had visited traditional healers presumably to exorcise the spirits that had possessed them. The Durban Indian community has been reported to be a deculturing community with many of its members adopting Western cultural attitudes and values. The following factors (religion, language grouping, and beliefs derived from folk-lore), specific to Indian culture, appear to have an important influence in shaping some aspects of the phenomenology of auditory hallucinations of psychotic Indian males. / Thesis (M.Med.)-University of Natal, Durban, 1985.

No description available.

No description available.

Everyday speech perception frequently occurs in degraded listening conditions, against a background of noise, interruptions and intermingling voices. Despite these challenges, speech perception is remarkably successful, due in part to perceptual learning. Previous research has demonstrated more rapid perceptual learning of acoustically-degraded speech when listeners are given the opportunity to map the linguistic content of utterances, presented in clear auditory form, onto the degraded auditory utterance. Here, I investigate whether learning is further enhanced by the provision of naturalistic facial gestural information, presented concurrently with either the clear auditory sentence (Experiment I), or with the degraded utterance (Experiment II). Recorded materials were noise-vocoded (4 frequency channels; 50- 8000 Hz). Noise-vocoding (NV) is a popular simulation of speech transduced through a cochlear implant, and 4-channel NV speech is difficult for naïve listeners to understand, but can be learned over several sentences of practice. In Experiment I, each trial began with an auditory-alone presentation of a degraded stimulus for report (D). In two conditions, this was followed by passive listening to either the clear spoken form and then the degraded form again (condition DCD), or the reverse (DDC); the former format of presentation (DCD) results in more efficient learning (Davis et al, 2005). Condition DCvD was similar to DCD, except that the clear spoken form was accompanied by facial gestural information (a talking face). The results indicate that presenting clear audiovisual feedback (DCvD) does not confer any advantage over clear auditory feedback (DCD). In Experiment II, two groups received a degraded sentence presentation with corresponding facial movements (Dv); the second group also received a second degraded (auditory-alone) presentation (DvD). Two control conditions and a baseline DCvD condition were also tested. Although they never received clear speech feedback, performance in the DvD group was significantly greater than in all others, indicating that perceptual learning mechanisms can capitalize on visual concomitants of speech. The DvD group outperformed the Dv group, suggesting that the second degraded presentation in the DvD condition further facilitates generalization of learning. These findings have important implications for improving comprehension of speech in an unfamiliar accent or following cochlear implantation. / Thesis (Master, Psychology) -- Queen's University, 2011-09-01 16:50:58.923

No description available.