Influence of Binocular Disparity in Depth Perception Mechanisms in Virtual Environments

In this chapter, an experimental study is presented for evaluating the importance of binocular disparity in depth perception within a Virtual Environment (VE), which is assumed to be critical in many manipulation tasks. In this research work, two assumptions are made: Size cues strongly contaminate depth perception mechanisms and binocular disparity optimizes depth perception for manipulation tasks in VE. The results outline size cues as possible cause of depth perception degradation and binocular disparity as an important factor in depth perception, whose influence is altered by the position within a VE

Haptic-Enhanced Learning in Preclinical Operative Dentistry

Background: Virtual reality haptic simulators represent a new paradigm in dental education that may potentially impact the rate and efficiency of basic skill acquisition, as well as pedagogically influence the various aspects of students’ preclinical experience. However, the evidence to support their efficiency and inform their implementation is still limited. Objectives: This thesis set out to empirically examine how haptic VR simulator (Simodont®) can enhance the preclinical dental education experience particularly in the context of operative dentistry. We specify 4 distinct research themes to explore, namely: simulator validity (face, content and predictive), human factors in 3D stereoscopic display, motor skill acquisition, and curriculum integration. Methods: Chapter 3 explores the face and content validity of Simodont® haptic dental simulator among a group of postgraduate dental students. Chapter 4 examines the predictive utility of Simodont® in predicting subsequent preclinical and clinical performance. The results indicate the potential utility of the simulator in predicting future clinical dental performance among undergraduate students. Chapter 5 investigates the role of stereopsis in dentistry from two different perspectives via two studies. Chapter 6 explores the effect of qualitatively different types of pedagogical feedback on the training, transfer and retention of basic manual dexterity dental skills. The results indicate that the acquisition and retention of basic dental motor skills in novice trainees is best optimised through a combination of instructor and visualdisplay VR-driven feedback. A pedagogical model for integration of haptic dental simulator into the dental curriculum has been proposed in Chapter 7. Conclusion: The findings from this thesis provide new insights into the utility of the haptic virtual reality simulator in undergraduate preclinical dental education. Haptic simulators have promising potential as a pedagogical tool in undergraduate dentistry that complements the existing simulation methods. Integration of haptic VR simulators into the dental curriculum has to be informed by sound pedagogical principles and mapped into specific learning objectives

Age-related changes in memory for object locations across different perspectives.

One important aspect of spatial cognition is the ability to recognize and remember spatial locations across different viewpoints. Previous research has suggested that those abilities decline in older adults. The aim of the current PhD project is to develop a clearer understanding of what may be contributing to age-related declines in recognising object locations from different perspectives. Specifically, focusing on how ageing effects encoding strategies that are used to memorize spatial configurations and the precision with which object/landmark locations are remembered. In Chapter 2, gaze behaviour was recorded during a task in which young and older adults judged whether previously encoded objects have remained in the same position or were displaced following perspective shifts. Ageing was associated with declines in spatial processing abilities. Additionally, older adults displayed a more conservative decision style and relied more on encoding object positions using room-based cues compared to young adults, who focused on the spatial relations among the to-be remembered objects during encoding. In Chapter 3, age-related differences in encoding strategies were further investigated using a modified version of the task used in Chapter 2 in which the availability and utility of the room- based cues was manipulated. Performance accuracy was similar across both age groups, yet, older adults displayed a greater preference towards a more categorical encoding strategy in which they formed spatial relations between objects and room-based cues. In the remaining chapters the focus shifted to investigating the precision with which object locations are remembered across different perspectives. In Chapter 4 participants memorized the position of an object in a virtual room and then judged from a different perspective, whether the object has moved to the left or to the right. Results revealed that participants exhibited a systematic bias in their responses that was termed the reversed congruency effect. Specifically, participants performed worse when the camera and the object moved in the same direction than when they moved in opposite directions. In Experiment 2, it was shown that the presence of additional objects in the environment reduced the reversed congruency effect whilst in Experiment 3 the reversed congruency effect was greater in older adults, suggesting that the quality of spatial memory and perspective-taking abilities are critical in mediating the reversed congruency effect. In Chapter 5, a novel task was used to investigate the systematic bias reported in Chapter 4. In this task participants encoded the position of an object in a virtual room and then estimated the object’s position following a perspective shift. In addition, memory load was manipulated. Overall, participants systematically overestimated the position of the object in the direction of the perspective shift. This bias was present in both memory and perception conditions. In Chapter 6, these results were replicated in an online-based version of the study. Lastly in Chapter 7, the influence of camera translations and camera rotations on the perspective shift related bias was decoupled. Additionally, the study investigated whether adding more information into the scene would reduce the bias and if there are age-related differences in the precision of object location estimates and the tendency to display the bias related to perspective shift. Overall, camera translations led to a greater systematic bias than camera rotations. Furthermore, the use of additional spatial information improved the precision with which object locations were estimated and reduced the bias associated with camera translation. Finally, although older adults were as precise as younger participants when estimating object locations, they benefited less from additional spatial information and their responses were more biased in the direction of camera translations. Overall, by combining eye-tracking and diffusion modelling the current thesis shows that ageing is associated with changes in the type of information that is used to encode object locations across different perspectives. Additionally, ageing was found to be particularly associated with impairments in the formation of fine-grained spatial representations. Furthermore, a novel bias in spatial memory across different perspectives has been identified. It is proposed that the perspective shift related bias is driven by uncertainty about object position following a perspective shift that leads participants to rely on an egocentric anchor when estimating the location of an object