A constructionist cognitive model of virtual presence

This paper proposes a cognitive model of presence which emphasizes the interaction of top-down and bottom-up processes, and the subsequent creation of temporary representations of an environment in working memory. These temporary representations (which we term constructions) are formations of meaning about the environment, which allow a subject to make inferences and interact in that environment. We argue that this constructionist position follows from the existence of hypothesis selection models of presence such as proposed by Slater & Steed. Finally, we contrast our model to that of Wirth et al and discuss some of the implications of this model for presence in unfamiliar or unrealistic environment

A connectionist explanation of presence in virtual environments

Presence has various definitions, but can be understood as the sensation that a virtual environment is a real place, that the user is actually in the virtual environment rather than at the display terminal, or that the medium used to display the environment has disappeared leaving only the environment itself. We present an attempt to unite various presence approaches by reducing each to what we believe is a common basis – the psychology of behaviour selection and control – and re-conceptualizing presence in these terms by defining cognitive presence – the mental state where the VE rather than the real environment is acting as the basis for behaviour selection. The bulk of this work represents the construction of a three-layer connectionist model to explain and predict this concept of cognitive presence. This model takes input from two major sources: the perceptual modalities of the user (bottom-up processes), and the mental state of the user (top-down processes). These two basic sources of input competitively spread activation to a central layer which competitively determines which behaviour script will be applied to regulate behaviour. We demonstrate the ability of the model to cope with current notions of presence by using it to successfully predict two published findings: one (Hendrix & Barfield, 1995) showing that presence increases with an increase in the geometric field of view of the graphical display, and another (Sallnas, 1999), which demonstrates the positive relationship between presence and the stimulation of more than one sensory modality. Apart from this theoretical analysis, we also perform two experiments to test the central tenets of our model. The first experiment aimed to show that presence is affected by both perceptual inputs (bottom-up processes), conceptual inputs (top-down processes), and the interaction of these. We collected 103 observations from a 2x2 factorial design with stimulus quality (2 levels) and conceptual priming (2 levels) as independent variables, and as dependent variable we used three measures of presence (Slater, Usoh & Steed’s scale (1995), Witmer & Singer’s (1998) Presence Questionnaire and our own cognitive presence measure) for the dependent variable. We found a significant main effect for stimulus quality and a significant interaction, which created a striking effect: priming the subject with material related in theme to the content of the VE increased the mean presence score for those viewing the high quality display, but decreased the mean of those viewing the low quality display. For those not primed with material related to the VE, no mean presence difference was discernible between those using high and low quality displays. The results from this study suggest that both top-down and bottom-up activation should be taken into account when explaining the causality of presence. Our second study aimed to show that presence comes about as a result not of raw sensory information, but rather due to partly-processed perceptual information. To do this we created a simple three group comparative design, with 78 observations. Each one of the three groups viewed the same VE under three display conditions: high-quality graphical, low-quality graphical, and text-only. Using the model, we predicted that the text and low-quality graphics displays would produce the same presence levels, while the high-quality display would outperform them both. The results were mixed, with the Slater, Usoh & Steed scale showing the predicted pattern, but the Presence Questionnaire showing each condition producing a significantly different presence score (in the increasing order: text, low-quality graphics, high-quality graphics). We conclude from our studies that the model shows the correct basic structure, but that it requires some refinement with regards to its dealings with non-immersive displays. We examined the performance our presence measure, which was found to not perform satisfactorily. We conclude by proposing some points relevant to the methodology of presence research, and by suggesting some avenues for future expansion of our model

Loading ... A Short Study into Security Delay Frustration

This report discusses a small experiment to investigate the amount of time users are willing to wait for applications to load, before they become frustrated. In particular, the experiment investigates whether, users are willing to wait longer, if they are aware that a security operation needs to be performed before loading the application. Our results show that users are willing to wait, on average 5.5 seconds longer for applications to load, if they are aware of a security operation

Novel Information on the Epitope of an Inverse Agonist Monoclonal Antibody Provides Insight into the Structure of the TSH Receptor

The TSH receptor (TSHR) comprises an extracellular leucine-rich domain (LRD) linked by a hinge region to the transmembrane domain (TMD). Insight into the orientation of these components to each other is required for understanding how ligands activate the receptor. We previously identified residue E251 at the LRD-hinge junction as contributing to coupling TSH binding with receptor activation. However, a single residue cannot stabilize the LRD-hinge unit. Therefore, based on the LRD crystal structure we selected for study four other potential LRD-hinge interface charged residues. Alanine substitutions of individual residues K244, E247, K250 and R255 (as well as previously known E251A) did not affect TSH binding or function. However, the cumulative mutation of these residues in varying permutations, primarily K250A and R255A when associated with E251A, partially uncoupled TSH binding and function. These data suggest that these three residues, spatially very close to each other at the LRD base, interact with the hinge region. Unexpectedly and most important, monoclonal antibody CS-17, a TSHR inverse agonist whose epitope straddles the LRD-hinge, was found to interact with residues K244 and E247 at the base of the convex LRD surface. These observations, together with the functional data, exclude residues K244 and E247 from the TSHR LRD-hinge interface. Further, for CS-17 accessibility to K244 and E247, the concave surface of the TSHR LRD must be tilted forwards towards the hinge region and plasma membrane. Overall, these data provide insight into the mechanism by which ligands either activate the TSHR or suppress its constitutive activity

The basic approval voting game

We survey results about Approval Voting obtained within the standard framework of game theory. Restricting the set of strategies to undominated and sincere ballots does not help to predict Approval Voting outcomes, which is also the case under strategic equilibrium concepts such as Nash equilibrium and its usual refinements. Strong Nash equilibrium in general does not exist but predicts the election of a Condorcet winner when one exists

Disease knowledge after an educational program in patients with GERD – a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Patient education has proved beneficial in several but not all chronic disease. Inconsistent findings may rely on varying educational effects of various programs and differential effects on subgroups of patients. Patients' increase in disease knowledge may serve as a feedback to the educator on how well the education program works – but may not be associated to relevant clinical outcomes like quality of life (QoL). This study aimed to investigate the effects of a group based education program for patients with gastroesophageal reflux disease (GERD) on disease knowledge and the association between knowledge and QoL.</p> <p>Methods</p> <p>Patients with GERD were randomly allocated to education (102 patients) or control (109 patients). The education program was designed as a structured dialogue conveying information about pathophysiology, pharmacological and non-pharmacological treatment of GERD, patients' rights and use of healthcare. Outcomes were a 24 item knowledge test on GERD (score 0 – 24) 2 and 12 months after the educational program and disease specific and general QoL (Digestive symptoms and disease impact, DSIQ, and General Health Questionnaire, GHQ).</p> <p>Results</p> <p>Patients allocated to education achieved higher knowledge test scores than controls at 2 months (17.0 vs. 13.1, p < 0.001) and at 12 months (17.1 vs. 14.0, p < 0.001) follow-up. Knowledge test score was positively associated with having completed advanced school and inversely related to psychiatric illness and poor QoL as perceived by the patients at the time of inclusion. Overall, changes in knowledge test score were not associated with change in QoL.</p> <p>Conclusion</p> <p>A group based education program for patients with GERD designed as a structured dialogue increased patients' disease knowledge, which was retained after 1 year. Changes in GERD-knowledge were not associated with change in QoL.</p> <p>Trial registration</p> <p>ClinicalTrials.gov: NCT0061850</p

Modulation of N-methyl-N-nitrosourea induced mammary tumors in Sprague–Dawley rats by combination of lysine, proline, arginine, ascorbic acid and green tea extract

INTRODUCTION: The limited ability of current treatments to control metastasis and the proposed antitumor properties of specific nutrients prompted us to examine the effect of a specific formulation (nutrient supplement [NS]) of lysine, proline, arginine, ascorbic acid, and green tea extract in vivo on the development of N-methyl-N-nitrosourea (MNU)-induced mammary tumors in rats. METHODS: A single intraperitoneal dose of MNU was injected into each of 20 female Sprague–Dawley rats (aged 50 days) to induce tumors. Two weeks after MNU treatment, a time by which the animals had recovered from MNU-induced toxicity, the rats were divided into two groups. Rats in group 1 (n = 10) were fed Purina chow diet, whereas those in group 2 (n = 10) were fed the same diet supplemented with 0.5% NS. After a further 24 weeks, the rats were killed and tumors were excised and processed. RESULTS: NS reduced the incidence of MNU-induced mammary tumors and the number of tumors by 68.4%, and the tumor burden by 60.5%. The inhibitory effect of NS was also reflected by decreased tumor weight; the tumor weights per rat and per group were decreased by 41% and 78%, respectively. In addition, 30% of the control rats developed ulcerated tumors, in contrast to 10% in the nutrient supplemented rats. CONCLUSION: These findings suggest that the specific formulation of lysine, proline, arginine, ascorbic acid, and green tea extract tested significantly reduces the incidence and growth of MNU-induced mammary tumors, and therefore has strong potential as a useful therapeutic regimen for inhibiting breast cancer development

Study of the reaction e^{+}e^{-} -->J/psi\pi^{+}\pi^{-} via initial-state radiation at BaBar

We study the process $e^+e^-\to J/\psi\pi^{+}\pi^{-}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BaBar detector at center-of-mass energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 $\mathrm{fb^{-1}}$. We investigate the $J/\psi \pi^{+}\pi^{-}$ mass distribution in the region from 3.5 to 5.5 $\mathrm{GeV/c^{2}}$. Below 3.7 $\mathrm{GeV/c^{2}}$ the $\psi(2S)$ signal dominates, and above 4 $\mathrm{GeV/c^{2}}$ there is a significant peak due to the Y(4260). A fit to the data in the range 3.74 -- 5.50 $\mathrm{GeV/c^{2}}$ yields a mass value $4244 \pm 5$ (stat) $\pm 4$ (syst)$\mathrm{MeV/c^{2}}$ and a width value $114 ^{+16}_{-15}$ (stat)$\pm 7$(syst)$\mathrm{MeV}$ for this state. We do not confirm the report from the Belle collaboration of a broad structure at 4.01 $\mathrm{GeV/c^{2}}$. In addition, we investigate the $\pi^{+}\pi^{-}$ system which results from Y(4260) decay

The dynamics of neural fields on bounded domains: an interface approach for Dirichlet boundary conditions

Continuum neural field equations model the large scale spatio-temporal dynamics of interacting neurons on a cortical surface. They have been extensively studied, both analytically and numerically, on bounded as well as unbounded domains. Neural field models do not require the specification of boundary conditions. Relatively little attention has been paid to the imposition of neural activity on the boundary, or to its role in inducing patterned states. Here we redress this imbalance by studying neural field models of Amari type (posed on one- and two-dimensional bounded domains) with Dirichlet boundary conditions. The Amari model has a Heaviside nonlinearity that allows for a description of localised solutions of the neural field with an interface dynamics. We show how to generalise this reduced but exact description by deriving a normal velocity rule for an interface that encapsulates boundary effects. The linear stability analysis of localised states in the interface dynamics is used to understand how spatially extended patterns may develop in the absence and presence of boundary conditions. Theoretical results for pattern formation are shown to be in excellent agreement with simulations of the full neural field model. Furthermore, a numerical scheme for the interface dynamics is introduced and used to probe the way in which a Dirichlet boundary condition can limit the growth of labyrinthine structures