Current theories of environmental cognition typically differentiate between an online, transient, and dynamic system of spatial representation and an offline and enduring system of memory representation. Here we present additional evidence for such two-system theories in the context of the disorientation paradigm introduced by Wang and Spelke (2000). Several experiments replicate the finding that disorientation results in a decrease in the precision of people's estimates of relative directions. In contrast to the typical interpretation of this effect as indicating the primacy of a transient spatial system, our results are generally more consistent with an interpretation of it as indicating a switch from a relatively precise online representation to a relatively coarse enduring one. Further experiments examine the relative precision of transient and enduring representations, and show that switching between them does not require disorientation, but can also be produced by self-rotations as small as 135°. KeywordsSpatial representation; spatial memory; egocentric updating; spatial updating; cognitive maps Transient and enduring spatial representations under disorientation and selfrotationKnowing the locations of objects in one's environment is a fundamental competence that is critical for survival. Because of this, understanding how humans (and other animals) interpret, monitor, and internally represent spatial information about their environment has been one of the major driving issues in the contemporary study of spatial cognition. In the past 15 years, several investigators have proposed theories of environmental behavior that posit a two-system or two-process account of spatial cognition (Amorim, Glasauer, Corpinot, & Berthoz, 1997;Arbib, 1999;Creem & Proffitt, 1998;Easton & Sholl, 1995;Gallistel, 1990;Hartley & Burgess, 2005;Huttenlocher, Hedges, & Duncan, 1991;McNamara, 2003;Mou, McNamara, Valiquette, & Rump, 2004;Wang, 2000;Wang & Spelke, 2000). Although these accounts differ in many of their details, in general, they all contrast an online transient system that is chiefly supported by perceptual processes and that codes spatial information with relatively high precision, with an offline enduring system that is supported primarily by long-term memory and whose codes are relatively coarse and/or biased

AIM The aim of the study was to assess two levels of immersive virtual reality simulation (VRS) to teach the skill of decontamination. BACKGROUND Little is known about the use of VRS in providing disaster education, including retention. METHOD Quasiexperimental design with repeated measures, supplemented by qualitative data, using a convenience sample of senior baccalaureate nursing students (n = 197) from four Midwest campuses was used. Students were randomly assigned to a group (two levels of immersive VRS and a control group) to learn the skill of decontamination. Cognitive learning, performance, and performance time were measured pre/post and at six months. RESULTS Outcome measures were significant with immediate postintervention improvements and lower retention scores at six months. No significant differences were noted between groups. Students were satisfied with the VRS but found immersive VRS more interactive. CONCLUSION VRS provides another alternative for simulated learning experiences; best practice approaches for its use still need to be explored.

Adoption of virtual reality technology may be delayed due to high up-front costs with unknown returns on that investment. In this article, we present a cost analysis of using virtual reality as a training tool. Virtual reality was used to train neonatal intensive care workers in hospital evacuation. A live disaster exercise with mannequins was also conducted that approximated the virtual experience. Comparative costs are presented for the planning, development, and implementation of both interventions. Initially, virtual reality is more expensive, with a cost of $229.79 per participant (total cost $18 617.54 per exercise) for the live drill versus $327.78 (total cost $106 951.14) for virtual reality. When development costs are extrapolated to repeated training over 3 years, however, the virtual exercise becomes less expensive with a cost of $115.43 per participant, while the cost of live exercises remains fixed. The larger initial investment invirtual reality can be spread across a large number of trainees and a longer time period with little additional cost, while each live drill requires additional costs that scale with the number of participants.

Redirected walking algorithms imperceptibly rotate a virtual scene and scale movements to guide users of immersive virtual environment systems away from tracking area boundaries. These distortions ideally permit users to explore large and potentially unbounded virtual worlds while walking naturally through a physically limited space. Estimates of the physical space required to perform effective redirected walking have been based largely on the ability of humans to perceive the distortions introduced by redirected walking and have not examined the impact the overall steering strategy used. This work compares four generalized redirected walking algorithms, including Steer-to-Center, Steer-to-Orbit, Steer-to-Multiple-Targets and Steer-to-Multiple+Center. Two experiments are presented based on simulated navigation as well as live-user navigation carried out in a large immersive virtual environment facility. Simulations were conducted with both synthetic paths and previously-logged user data. Primary comparison metrics include mean and maximum distances from the tracking area center for each algorithm, number of wall contacts, and mean rates of redirection. Results indicated that Steer-to-Center out-performed all other algorithms relative to these metrics. Steer-to-Orbit also performed well in some circumstances.

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A goal of redirected walking (RDW) is to allow large virtual worlds to be explored within small tracking areas. Generalized steering algorithms, such as steer-to-center, simply move the user toward locations that are considered to be collision free in most cases. The algorithm developed here, FORCE, identifies collision-free paths by using a map of the tracking area's shape and obstacles, in addition to a multistep, probabilistic prediction of the user's virtual path through a known virtual environment. In the present implementation, the path predictions describe a user's possible movements through a virtual store with aisles. Based on both the user's physical and virtual location / orientation, a search-based optimization technique identifies the optimal steering instruction given the possible user paths. Path prediction uses the map of the virtual world; consequently, the search may propose steering instructions that put the user close to walls if the user's future actions eventually lead away from the wall. Results from both simulated and real users are presented. FORCE identifies collision-free paths in 55.0 percent of the starting conditions compared to 46.1 percent for generalized methods. When considering only the conditions that result in different outcomes, redirection based on FORCE produces collision-free path 94.5 percent of the time.

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