Wheatstone-Panum limiting case: occlusion, camouflage, and vergence-induced disparity cues.

We examined effects of binocular occlusion, binocular camouflage, and vergence-induced disparity cues on the perceived depth between two objects when two stimuli are presented to one eye and a single stimulus to the other (Wheatstone-Panum limiting case). The perceived order and magnitude of the depth were examined in two experimental conditions: (1) The stimulus was presented on the temporal side (occlusion condition) and (2) the nasal side (camouflage condition) of the stimulus pair on one retina so as to fuse with the single stimulus on the other retina. In both conditions, the separation between the stimulus pair presented to one eye was systematically varied. Experiment 1, with 16 observers, showed that the fused object was seen in front of the nonfused object in the occlusion condition and was seen at the same distance as the nonfused object in the camouflage condition. The perceived depth between the two objects was constant and did not depend on the separation of the stimulus pair presented to one eye. Experiment 2, with 45 observers, showed that the disparity induced by vergence mainly determined the perceived depth, and the depth magnitude increased as the separation of the stimulus pair was made wider. The results suggest that (1) occlusion provides depth-order information but not depth-magnitude information, (2) camouflage provides neither depth-order nor depth-magnitude information, and (3) vergence-induced disparity provides both order and magnitude information.     

Subadditive versus hyperbolic discounting: A comparison of choice and matching

Impulsive and myopic choices are often explained as due to hyperbolic discounting, meaning that people are impatient for outcomes available immediately, and become increasingly more patient the more the outcome is delayed. Recent research, however, has suggested that much experimental evidence for increasing patience is actually due to subadditive discounting: people are less patient (per-time-unit) over shorter intervals regardless of when they occur. Because previous research into subadditive discounting has used a choice elicitation procedure, the present paper tests whether it generalises to matching. We find strong evidence that it does, but also find weak evidence of increasing patience for matching. We suggest, however, that subadditive discounting alone may be sufficient to account for all of our results. We conclude by questioning the contribution that hyperbolic discounting makes to our understanding of time preference.     

How are base‐rates used,when they are used: a comparison of additive and Bayesian models of base‐rate use

Previous research has uncovered many conditions that encourage base‐rate use. The present research investigates how base‐rates are used when conditions are manipulated to encourage their use in the lawyer/engineer paradigm. To examine the functional form of the response to base‐rate, a factorial design was employed in which both base‐rate and the individuating information were varied within‐subject. We compared the performance of several models of base‐rate use, including a model that allows base‐rate and individuating information to be combined in a strictly additive fashion, and a model which presumes that respondents use Bayes' Rule in forming their judgments. Results from 1493 respondents showed that the additive model is a stronger predictor of base‐rate use than any other model considered, suggesting that the base‐rate and individuating information are processed independently in the lawyer/engineer paradigm. A possible mechanism for this finding is discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Presence and emotions in virtual environments: the influence of stereoscopy.

This study investigates how stereoscopy (the illusion of depth and 3D imaging) affects the sense of presence and the intensity of the positive mood that users feel in virtual environments (VEs). A between-group design was used, and 40 volunteers were randomly assigned to one of two experimental conditions (stereoscopy vs. no stereoscopy) and to one of two emotional VEs (relaxation or joy). The participants' emotions were assessed before and after the VR experience. Presence was measured with two postexperiment questionnaires (ITC-SOPI and SUS). Results show that there were no differences between stereoscopic and monoscopic presentations in VEs (neither subjective sense of presence nor emotional reactions). Practical and theoretical implications of these findings are discussed herein.     

Haptic interfaces for virtual environments: perceived instability and force constancy in haptic sensing of virtual surfaces.

Haptic interfaces are becoming more commonplace in virtual environment and teleoperation systems. There is a growing need to not only continue to improve hardware platforms and rendering algorithms, but evaluate human performance with haptic interfaces. This review summarizes two recent studies inspired by perception problems in using haptic interfaces to interact with virtual environments. The first study evaluated perceived quality of virtual haptic textures and discovered several types of perceived instability and their sources. We found that the buzzing type of perceived instability was most likely due to the mechanical resonance of the haptic interface hardware, and the aliveness type of perceived instability due to our inability to sense the slight movements of our hands in free space. The second study focused on the motor strategy employed during interaction with a virtual surface via a force-feedback haptic interface. We found that users tended to maintain a constant penetration force into a virtual surface when interacting with the surface. This can result in a reversal in perceived relative surface heights if the taller surface is rendered with a lower stiffness, thereby resulting in an erroneous perception of the virtual environment being rendered. For both studies, possible solutions to improving human perception of virtual and remote objects via hardware and/or software are discussed.     

Spatial memories of virtual environments: How egocentric experience, intrinsic structure, and extrinsic structure interact

Previous research has uncovered three primary cues that influence spatial memory organization:egocentric experience, intrinsic structure (object defined), and extrinsic structure (environment defined). In the present experiments, we assessed the relative importance of these cues when all three were available during learning. Participants learned layouts from two perspectives in immersive virtual reality. In Experiment 1, axes defined by intrinsic and extrinsic structures were in conflict, and learning occurred from two perspectives, each aligned with either the intrinsic or the extrinsic structure. Spatial memories were organized around a reference direction selected from the first perspective, regardless of its alignment with intrinsic or extrinsic structures. In Experiment 2, axes defined by intrinsic and extrinsic structures were congruent, and spatial memories were organized around reference axes defined by those congruent structures, rather than by the initially experienced view. The findings are discussed in the context of spatial memory theory as it relates to real and virtual environments.     

Perfectionism, ego defense styles, and depression: a comparison of self-reports versus informant ratings

The present study examined the associations among perfectionism, defense styles, and depression in an Israeli community sample of young adults. This study involved a comparison of self-reports and informant ratings on all measures. A community sample of 210 pairs of same-sex best friends from Israel completed the Multidimensional Perfectionism Scale, the Defense Styles Questionnaire - 40, and a depression measure. Analyses confirmed that socially prescribed perfectionism is associated with depression, not only in terms of self-reports but also in terms of informant ratings. In addition, informant ratings revealed a link between other-oriented perfectionism and depression. Both self-reports and informant ratings also indicated that socially prescribed perfectionism is associated with immature defense styles and neurotic defense styles. Further simultaneous Structural Equation Modeling (SEM) analyses of self-reports and informant ratings showed that maladaptive defense styles mediate the link between socially prescribed perfectionism and depression. The practical and theoretical implications of these findings are discussed.     

The what,how much,and when of study strategies: comparing intended versus actual study behaviour

The study behaviours of students can be assessed from several perspectives, such as what study strategies are used, the total number of hours of study, and the distribution of studying over time. Here, we present the results of a survey study that considered each of these perspectives by asking students to report the what, how much, and when of their study behaviours over the course of a semester. As important, to better understand students’ use of study strategies, we also had students report at the beginning of the semester how they intended to study and their beliefs about the effectiveness of a variety of common strategies. Our results indicate that during the semester, students rely on relatively ineffective strategies and mass their studying the day or two before an exam. However, students intended to begin studying earlier and to use a mix of effective and ineffective study habits. Despite their use of some ineffective strategies, they did have a relatively accurate assessment of which strategies were less versus more effective. Taken together, our results suggest that students have some excellent intentions but may falter because massing study the evening before an exam limits their use of more effective study strategies.     

Body-image,quality of life and psychological distress: a comparison between kidney transplant patients and a matching healthy sample

The purpose of the current study was to assess the uniqueness of the condition of kidney transplant recipients in comparison to a sample of matching healthy peers in relation to body-image dissatisfaction and identification, quality of life and psychological distress. Participants were 45 kidney transplant recipients who were under follow-up care at a Transplant Unit of a major Medical Center, and a sample of 45 matching healthy peers. Measures were taken using self-report questionnaires [Body-Image Ideals Questionnaire (BIIQ), Body Identification Questionnaire (BIQ), Brief Symptoms Inventory (BSI), and the SF-12]. The major findings were the following: (i) kidney transplant recipients reported lower levels of quality of life and higher levels of PsD when compared to their healthy peers; (ii) no difference in body-image dissatisfaction was found between the two studied groups; (iii) significant correlations between body-image dissatisfaction quality of life and PsD were found only in the kidney transplant recipients. The kidney transplantation condition has a moderating effect in the association between body-image dissatisfaction PsD but not in the association between body-image dissatisfaction and quality of life; (iv) kidney transplant recipients experienced higher levels of body identification than did their healthy peers. Taken together, these findings highlight the unique condition of kidney transplant recipients, as well as the function that body-image plays within the self.     

Using a virtual reality system to study balance and walking in a virtual outdoor environment: a pilot study.

Falls and fall-related injuries are a major problem for elderly persons. Most falls occur during walking and turning, and the risk of falling increases when attention is diverted to something besides walking. It is often difficult to standardize methods for testing balance and fall tendency in a clinically relevant setting. We describe the development of a system using a virtual environment (VE) to assess how attention demanding and unexpected events influence a person's capacity to control balance and movement. The hardware in the system consists of a head-mounted display (HMD), a magnetic tracker system, and two SGI computers. The software consists of the image generation of the VE and the management and visualization of motion tracking data. In a preliminary pilot study eight subjects (age 23-80) participated. Each subject walked on a normal floor and was visually presented a familiar outdoor environment in the HMD. They were exposed to different unexpected events, such as a virtual snowfall and tilting of the VE. Disturbances of balance and walking patterns such as changes in speed, stride length and balance reactions like slipping were observed. Two subjects experienced symptoms of cyber sickness with a SSQ score above 25 points. Walking with sensors only did not affect walking time, but in VE the subjects generally walked more slowly. Virtual tilting of the environment had an impact on balance performance during walking. This effect was not observed while the test subjects were walking in a virtual snowfall. The model needs further development but may hold a potential for clinical use.     

Revisiting the effect of quality of graphics on distance judgments in virtual environments: A comparison of verbal reports and blind walking

In immersive virtual environments, judgments of perceived egocentric distance are significantly underestimated, as compared with accurate performance in the real world. Two experiments assessed the influence of graphics quality on two distinct estimates of distance, a visually directed walking task and verbal reports. Experiment 1 demonstrated a similar underestimation of distances walked to previously viewed targets in both low- and high-quality virtual classrooms. In Experiment 2, participants’ verbal judgments underestimated target distances in both graphics quality environments but were more accurate in the high-quality environment, consistent with the subjective impression that high-quality environments seem larger. Contrary to previous results, we suggest that quality of graphics does influence judgments of distance, but only for verbal reports. This behavioral dissociation has implications beyond the context of virtual environments and may reflect a differential use of cues and context for verbal reports and visually directed walking.     

Visual memory in a spelling matching task: comparison of good and poor spellers

The role of visual memory in learning to spell words was investigated through a matching task on which one nonsense word was presented, then a second word identical in spelling or differing in one letter was presented. Ten pairs of 9th and 10th-grade students, matched for intelligence and sex but of different spelling ability, were asked to indicate whether word pairs were spelled the same or differently. The two words of a pair were either the same or different in print size or letter case. Significant effects were obtained for spelling ability, print size (same or different), and letter case (same or different), and the interaction of size X case, providing evidence for the use of visual memory by both good and poor spellers in learning to spell words. Good spellers were equally able to identify matched and mismatched pairs, while poor spellers showed greater difficulty in identifying mismatches than matches, supporting Frith's (1980) "partial cues" explanation of poor spelling performance.     

Gendered virtual environments of STEM fields: a cultural-ecological analysis of predominantly white and historically black institutions

Although many studies have examined gender and racial discrepancies in STEM participation, few have considered variation in the gendered construction of STEM across racial spaces. We applied a cultural psychological perspective to investigate whether variation in conceptions of gender identity across African American and European American settings resonates with variation in gendered constructions of science, technology, engineering, and mathematics (STEM) domains across predominantly white institutions (PWIs) and historically black colleges and universities (HBCUs). We further examined implications of engagement with virtual STEM departments across these school categories. In Study 1, independent coders rated website images as less masculine, and evaluated website climates more favorably, for physics and biology departments at HBCUs relative to PWIs. In Studies 2 and 3, we used these website images as stimuli in within- and between-subjects experiments. Participants gave more positive ratings for sense of belonging and perceived climate in response to images from physics departments at HBCUs than at PWIs; women rated physics departments at PWIs as higher in masculinity than those at HBCUs. We replicated these patterns in Study 3, and also found that lower sense of belonging due to exposure to images from PWI physics departments predicted less interest in pursuing STEM fields among women only. We discuss implications of our findings for understanding and addressing gender discrepancies in STEM participation.

     

Dynamic illusion effects in a reaching task: evidence for separate visual representations in the planning and control of reaching.

The effects of an orientation illusion on perception and 2 different actions were investigated. An 8-cm x 2-cm cylindrical bar was placed in front of participants at various orientations. A background grating was used to induce an orientation illusion. In a perception task, the illusion affected participants' ability to align the bar with their sagittal planes. In one reaching task, a similar effect of the illusion was found on the choice between 2 possible grasping postures. In a second reaching task involving a single grasping posture, the orientation illusion affected the orientation of the hand at the beginning of the reach but not near its end. The authors argue that reaching trajectories are planned and initiated through a context-dependent representation but are corrected on-line through a context-independent representation. The relation of this model to a more general dichotomy between perception and action is discussed.     

Students' perceptions of constructivist Internet learning environments by a physics virtual laboratory: the gap between ideal and reality and gender differences.

The purpose of this study was to investigate the perceptions of Internet users of a physics virtual laboratory, Demolab, in Taiwan. Learners' perceptions of Internet-based learning environments were explored and the role of gender was examined by using preferred and actual forms of a revised Constructivist Internet-based Learning Environment Survey (CILES). The students expressed a clear gap between ideal and reality, and they showed higher preferences for many features of constructivist Internet-based learning environments than for features they had actually learned in Demolab. The results further suggested that male users prefer to be involved in the process of discussion and to show critical judgments. In addition, male users indicated they enjoyed the process of negotiation and discussion with others and were able to engage in reflective thoughts while learning in Demolab. In light of these findings, male users seemed to demonstrate better adaptability to the constructivist Internet-based learning approach than female users did. Although this study indicated certain differences between males and females in their responses to Internet-based learning environments, they also shared numerous similarities. A well-established constructivist Internet-based learning environment may encourage more female learners to participate in the science community.     

Visual information and the control of reaching in children: a comparison between children with and without developmental coordination disorder

Three experiments were performed on reach and grasp in 9- to 10-year-old children (8 controls and 8 with developmental coordination disorder [DCD]). In normal reaching, children in the DCD group were less responsive to the accuracy demands of the task in controlling the transport component of prehension and spent less time in the deceleration phase of hand transport. When vision was removed as movement began, children in the control group spent more time decelerating and reached peak aperture earlier. Children in the DCD group did not do that, although, like the control group, they did increase grip aperture in the dark. When depth cues were reduced and only the target or only the target and hand were visible, children in the control group used target information to maintain the same grip aperture in all conditions, but DCD children behaved as if the target was not visible. Throughout the studies, the control group of 9- to 10-year-olds did not produce adult-like adaptations to reduced vision, suggesting that they had not yet attained adult-like integration of sensory input. Compared with control children, children with DCD did not exhibit increased dependence on vision but showed less recognition of accuracy demands, less adaptation to the removal of vision, and less use of minimal visual information when it was available.     

The development of route learning in Down syndrome,Williams syndrome and typical development: investigations with virtual environments

The ability to navigate new environments has a significant impact on the daily life and independence of people with learning difficulties. The aims of this study were to investigate the development of route learning in Down syndrome (N = 50), Williams syndrome (N = 19), and typically developing children between 5 and 11 years old (N = 108); to investigate use of landmarks; and to relate cognitive functions to route‐learning ability in these groups. Overall, measures of attention and long‐term memory were strongly associated with route learning, even once non‐verbal ability was controlled for. All of the groups, including 5‐ to 6‐year‐old TD children, demonstrated the ability to make use of all landmark types to aid route learning; those near junctions, those further from junctions, and also distant landmarks (e.g. church spire, radio mast). Individuals with WS performed better than a matched subset of TD children on more difficult routes; we suggest that this is supported by relatively strong visual feature recognition in the disorder. Participants with DS who had relatively high levels of non‐verbal ability performed at a similar level to TD participants.     

Finding order and direction from chaos: a comparison of chaos career counseling and trait matching counseling

Chaos career counseling, based on the Chaos Theory of Careers (R. G. L. Pryor & J. E. H. Bright, 2003a, 2003b), was compared with trait matching career counseling and a wait list control. Sixty university students who attended the Careers Research and Assessment Service seeking career advice were randomly assigned to the chaos intervention, the trait matching intervention, or a wait list control group. Both chaos and trait matching counseling had a positive impact; however, chaos counseling had a more lasting effect. Overall, results support using the chaos counseling approach as a valid alternative to trait matching approaches. Implications for counseling practice as well as future research are discussed.