Masciocchi and Still [1] suggested that biologically inspired computational saliency models could predict attentional deployment within webpages. Their stimuli were presented on a large desktop monitor. We explored whether a saliency model’s predictive performance can be applied to small mobile interface displays. We asked participants to free-view screenshots of NASA’s mobile application Playbook. The Itti et al. [2] saliency model was employed to produce the predictive stimulus-driven maps. The first six fixations were used to select values to form the saliency maps’ bins, which formed the observed distribution. This was compared to the shuffled distribution, which offers a very conservative chance comparison as it includes predictable spatial biases by using a within-subjects bootstrapping technique. The observed distribution values were higher than the shuffled distribution. This suggests that a saliency model was able to predict the deployment of attention within small mobile application interfaces.

SSUSI-Lite is a far-ultraviolet (115-180nm) hyperspectral imager for monitoring space weather. The SSUSI and GUVI sensors, its predecessors, have demonstrated their value as space weather monitors. SSUSI-Lite is a refresh of the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) design that has flown on the Defense Meteorological Satellite Program (DMSP) spacecraft F16 through F19. The refresh updates the 25-year-old design and insures that the next generation of SSUSI/GUVI sensors can be accommodated on any number of potential platforms. SSUSI-Lite maintains the same optical layout as SSUSI, includes updates to key functional elements, and reduces the sensor volume, mass, and power requirements. SSUSI-Lite contains an improved scanner design that results in precise mirror pointing and allows for variable scan profiles. The detector electronics have been redesigned to employ all digital pulse processing. The largest decrease in volume, mass, and power has been obtained by consolidating all control and power electronics into one data processing unit.

PURPOSE:To determine whether peripheral field loss (PFL) systematically distorts spatial representations and to determine whether persons with actual PFL show adaptation effects.METHODS:Nine participants with PFL from retinitis pigmentosa (RP) learned the locations of statues in a virtual environment by walking a predetermined route. After this, the statues were removed and the participants were to walk to where they thought each statue had been located. Placement errors, defined as the differences between the actual and estimated locations, were calculated and decomposed into distance errors and angular offsets.RESULTS:Participants showed distortions in remembered statue locations, with mean placement errors increasing with decreasing field of view (FOV) size. A correlation was found between FOV size and mean distance error but not mean angular offsets. Compared with eye movements of normal-vision participants with simulated PFL from a previous study, the eye movements of the RP participants were shorter in duration, and smaller saccadic amplitudes were observed only for the RP participants with the smallest FOV sizes. The RP participants also made more fixations to the statues than the simulated PFL participants. Results from a real-world replication of the task showed no behavioral differences between simulated and naturally occurring PFL.CONCLUSIONS:PFL is associated with distortions in spatial representations that increase with decreasing FOV. The differences in eye movement and gaze patterns suggest possible adaptive changes on the part of the RP participants. However, the use of different sampling strategies did not aid the performance of the RP participants as FOV size decreased.

Three experiments examine how the peripheral visual field (PVF) mediates the development of spatial representations. In Experiment 1 participants learned and were tested on statue locations in a virtual environment while their field-of-view (FOV) was restricted to 40 degrees , 20 degrees , 10 degrees , or 0 degrees (diam). As FOV decreased, overall placement errors, estimated distances, and angular offsets increased. Experiment 2 showed large compressions but no effect of FOV for perceptual estimates of statue locations. Experiment 3 showed an association between FOV size and proprioception influence. These results suggest the PVF provides important global spatial information used in the development of spatial representations.

The following paper describes a new technique for simulating peripheral field losses in virtual environments to study the roles of the central and peripheral visual fields during navigation. Based on Geisler and Perry's (2002) gaze-contingent multiresolution display concept, the technique extends their methodology to work with three-dimensional images that are both transformed and rendered in real time by a computer graphics system. In order to assess the usefulness of this method for studying visual field losses, an experiment was run in which seven participants were required to walk to a target tree in a virtual forest as quickly and efficiently as possible while artificial head and eye-based delays were systematically introduced. Bilinear fits were applied to the mean trial times in order to assess at what delay lengths breaks in performance could be observed. Results suggest that breaks occur beyond the current delays inherent in the system. Increases in trial times across all delays tested were also observed when simulated peripheral field losses were applied compared to full FOV conditions. Possible applications and limitations of the system are discussed. The source code needed to program visual field losses can be found at lions.med.jhu.edu/archive/turanolab/Simulated_Visual_Field_Loss_Code.html.

Critical points were computed to determine the minimum field of view (FOV) size required for efficient navigation. Navigation performance in 20 normally sighted subjects was assessed using an immersive virtual environment. Subjects were instructed to walk through a virtual forest to a target tree as quickly as possible without hitting any obstacles (trees, boulders, and holes). The navigation task was performed in three FOV and image contrast conditions under binocular, monocular, chromatic and achromatic viewing conditions. FOV was constricted to 10 degrees , 20 degrees and 40 degrees diameter and average image contrast was nominally high (11%), medium (6%) and low (3%). Navigation performance was scored as latency in walk initiation, walk time to reach goal and the number of obstacle contacts. The results revealed a linear relationship between log FOV and the two time measures, log latency and log walk time. The slopes of the linear regressions for log latency and log walk time ranged between -0.11 and -0.41. Critical points were computed from the non-linear relationships found between the number of obstacle contacts and FOV. The critical points for efficient navigation were FOVs of 32.1 degrees , 18.4 degrees and 10.9 degrees (diam.) for low, medium and high image contrast levels, respectively, highlighting the importance of contrast on the size of the FOV required for efficient navigation. Neither binocularity nor image chromaticity significantly affected navigation performance. The findings of this study have important implications in the design and prescription of head mounted displays intended to augment navigation performance.

Three studies were conducted to examine whether men and women differ in how they recalibrate their path-integration systems when walking without vision in virtual environments. Distance cues provided by a scene and a tone, which ended each trial, were placed in conflict. Participants briefly viewed a room with a target, which was offset from their midlines and hung inside a doorframe on the far wall. After viewing, participants walked to the target's position until a tone sounded, ending the trial. In two experiments the doorframe was placed at 6 m and the tone sounded at 4 or 8 m. The rooms had minimal or photorealistic texturing applied. The third experiment used photorealistic texturing, but here the tone sounded at 6 m and the doorframe was presented at 4 or 8 m. Path angles were recorded to estimate perceived distance to the target. In all conditions tested, the women failed to scale their path angles. The men, however, scaled their path-angles with the auditory cue in the minimal-texture condition, but with the visual cue in the photorealistic-texture conditions. These results suggest that gender differences exist in the way that humans recalibrate their path-integration systems when walking without vision in virtual environments.

This study employed a novel method to dissociate the use of external visual information and internal spatial representations in human navigation. Using a goal-directed walking task and gaze-contingent displays, 14 participants with normal vision navigated within an immersive virtual forest during which each participant's field of view (FOV) was restricted to 10, 20, or 40 deg in diameter. Participants were classified into two groups, good and poor navigators, based on a cluster analysis of their individual mean latencies, walk times, and path efficiencies in the 10 deg condition. Changes in performance measures across the three FOVs were calculated for the two groups. Significant interactions were found, with the overall performance of the poor navigators decreasing at a faster rate than the performance of the good navigators. Perceptual spans were also calculated for the two groups, and it was determined that the good navigators were able to complete the same task as effectively as the poor navigators with a smaller FOV. Collectively, these results support recent theories stating that good navigators rely on internal spatial representations to a greater extent than poor navigators do.

With simulated optic flow (OF), heading thresholds are little affected by the retinal position of stimulation (Warren & Kurtz, 1992; Crowell & Kurtz, 1993). The only retinal advantage is with radial flow in the central retina. This study examines whether these passive-judgment findings generalize to the use of OF in walking. With an immersive virtual environment, 5 subjects performed a walking task with full fields (48 diam) and with simulated visual field loss linked to eye position. Retinal stimulation was restricted to either the central 10, a 10 window located 10 left of fixation (parafoveal), or the full field with a central 10 mask (peripheral). The target was presented in an empty space that lacked OF cues, a richly textured forest with trees, and a “cloud of dots” that lacked reliable landmark cues. Subjects were instructed to walk to a pole 8m away. Head position, measured with an optical tracker, determined the point of view and was used to record the walking path for analysis. To identify the influence of OF, the OF pattern was offset 10 to the right or left of the direction of walking. A 10 heading error indicates no OF influence, whereas a 0 error indicates maximum influence. The results showed that with full fields, OF was used only modestly to guide walking and the amount was reduced when stimulation was in the central retina. The peripheral stimulation had the lowest heading error in the forest scene (6.9 ), comparable to that with the full field (7.0 ), and significantly lower than that with central or parafoveal stimulation (9.0, 10.4 ). Similar findings were obtained in the cloud scene. No difference in heading error was observed in the empty-space scene (8.9 –9.8 ). These findings show that retinal position matters in the use of OF for goal-directed walking, but not as predicted by the threshold results. The use of simulated field loss in mobile observers takes us one step closer in bridging the gap between lab and the real world.

In this study we investigated whether a visual illusion located in far space alters a person's open-loop, target-directed walking path in the same manner as it alters the perception of the target's position. Through the use of immersive VR the subject was able to walk physically to the location of a target embedded in a scene that was manipulated to create a visual illusion, known as the induced Roelofs effect. This illusion has been shown to alter the perception of a target's position. The experiment consisted of two tasks: a perception task and an action task. In the perception task, subjects viewed the scene for 1 s, it disappeared, and they were to report the target's location verbally. The results showed that the visual illusion altered the reported positions in all but one subject. In the action task, subjects viewed the scene for 1 s, it disappeared, and the subjects were asked to walk to the target's location. The results showed that the illusion significantly altered the walking paths of most of the women and less than half of the men. A significant gender effect was observed; women's walking paths deviated, on average, by 7.1 degrees and men's, by only 2.0 degrees . These results indicate that action tasks in far space are susceptible to the effects of visual illusions, unlike the action tasks in near space that reportedly have been resistant to them. Furthermore, the significant gender effect suggests that men and women either have different strategies and/or employ different mechanisms when executing a visually guided task in far space.

Spatial context has been shown to affect the perceived location of an object. An object surrounded by a frame that is offset relative to one's midline is perceived to be more centrally located than it actually is (induced Roelof's effect). Remarkably, that same object will be accurately localized when subjects must point to it (Bridgeman et al., 1979). Differences in perception and action responses have been used to support the view that visual information is processed differently depending on whether the information is used for perception or action. Here we show a sex difference in the effects of context on spatial localization, predominantly revealed by an action response. Ten subjects wearing a head-mounted display, and viewing a virtual environment, were briefly presented (1 s) a scene of an object (2°-diameter ball) in a doorway (20.5° wide). Subjects were instructed to either verbally report the object's position relative to themselves or to walk to it. The object was positioned at −3°, 0°, or 3° relative to the subject's midline, and the doorway was either centered or offset by 5° to the left or right of the subject's midline. All subjects exhibited the typical Roelof's effect in their verbal report, with average object mislocalizations of 2.2° (men) and 4.2° (women) for the offset doorway conditions. However, when the subjects had to walk to the object, spatial context had little effect on the men's endpoints (average deviation <1°) but had significant effects on the endpoints of the women (average deviation >4°). These findings suggest a basic difference in men and women with respect to the effects of context on spatial processing as it relates to navigation and may help explain reported sex differences in navigation ability. Bridgeman, B. et al. (1979). Relation between cognitive and motor-oriented systems of visual position perception. Journal of Experimental Psychology: Human Perception and Performance, 5, 692–700.