Getting completely turned around: how disorientation impacts subjective straight ahead.

In manipulating a pointer to indicate subjective straight ahead (SSA), participants were more variable after a series of whole-body rotations in conjunction with external sensory blockade than after external sensory blockade alone. The variability of reported SSA did not increase consequent to a temporal delay matched to the time taken by the rotation procedure. These results suggest that an observer's egocentric reference frame is more complex and less stable than has previously been thought.

Tachistoscopic illumination and masking of real scenes.

Tachistoscopic presentation of scenes has been valuable for studying the emerging properties of visual scene representations. The spatial aspects of this work have generally been focused on the conceptual locations (e.g., next to the refrigerator) and directional locations of objects in 2-D arrays and/or images. Less is known about how the perceived egocentric distance of objects develops. Here we describe a novel system for presenting brief glimpses of a real-world environment, followed by a mask. The system includes projectors with mechanical shutters for projecting the fixation and masking images, a set of LED floodlights for illuminating the environment, and computer-controlled electronics to set the timing and initiate the process. Because a real environment is used, most visual distance and depth cues can be manipulated using traditional methods. The system is inexpensive, robust, and its components are readily available in the marketplace. This article describes the system and the timing characteristics of each component. We verified the system's ability to control exposure to time scales as low as a few milliseconds.

Gaze behavior and the perception of egocentric distance.

The ground plane is thought to be an important reference for localizing objects, particularly when angular declination is informative, as it is for objects seen resting at floor level. A potential role for eye movements has been implicated by the idea that information about the nearby ground is required to localize objects more distant, and by the fact that the time course for the extraction of distance extends beyond the duration of a typical eye fixation. To test this potential role, eye movements were monitored when participants previewed targets. Distance estimates were provided by walking without vision to the remembered target location (blind walking) or by verbal report. We found that a strategy of holding the gaze steady on the object was as frequent as one where the region between the observer and object was fixated. There was no performance advantage associated with making eye movements in an observational study (Experiment 1) or when an eye-movement strategy was manipulated experimentally (Experiment 2). Observers were extracting useful information covertly, however. In Experiments 3 through 5, obscuring the nearby ground plane had a modest impact on performance; obscuring the walls and ceiling was more detrimental. The results suggest that these alternate surfaces provide useful information when judging the distance to objects within indoor environments. Critically, they constrain the role for the nearby ground plane in theories of egocentric distance perception.

Peripheral vision benefits spatial learning by guiding eye movements.

The loss of peripheral vision impairs spatial learning and navigation. However, the mechanisms underlying these impairments remain poorly understood. One advantage of having peripheral vision is that objects in an environment are easily detected and readily foveated via eye movements. The present study examined this potential benefit of peripheral vision by investigating whether competent performance in spatial learning requires effective eye movements. In Experiment 1, participants learned room-sized spatial layouts with or without restriction on direct eye movements to objects. Eye movements were restricted by having participants view the objects through small apertures in front of their eyes. Results showed that impeding effective eye movements made subsequent retrieval of spatial memory slower and less accurate. The small apertures also occluded much of the environmental surroundings, but the importance of this kind of occlusion was ruled out in Experiment 2 by showing that participants exhibited intact learning of the same spatial layouts when luminescent objects were viewed in an otherwise dark room. Together, these findings suggest that one of the roles of peripheral vision in spatial learning is to guide eye movements, highlighting the importance of spatial information derived from eye movements for learning environmental layouts.

Two-category place representations persist over body rotations.

We explored a system that constructs environment-centered frames of reference and coordinates memory for the azimuth of an object in an enclosed space. For one group, we provided two environmental cues (doors): one in the front, and one in the rear. For a second group, we provided two object cues: a front and a rear cue. For a third group, we provided no external cues; we assumed that for this group, their reference frames would be determined by the orthogonal geometry of the floor-and-wall junction that divides a space in half or into multiple territories along the horizontal continuum. Using Huttenlocher, Hedges, and Duncan's (Psychological Review 98: 352-376, 1991) category-adjustment model (cue-based fuzzy boundary version) to fit the data, we observed different reference frames than have been seen in prior studies involving two-dimensional domains. The geometry of the environment affected all three conditions and biased the remembered object locations within a two-category (left vs. right) environmental frame. The influence of the environmental geometry remained observable even after the participants' heading within the environment changed due to a body rotation, attenuating the effect of the front but not of the rear cue. The door and object cues both appeared to define boundaries of spatial categories when they were used for reorientation. This supports the idea that both types of cues can assist in environment-centered memory formation.

Distraction shrinks space.

Research investigating how people remember the distance of paths they walk has shown two apparently conflicting effects of experience during encoding on subsequent distance judgments. By the feature accumulation effect, discrete path features such as turns, houses, or other landmarks cause an increase in remembered distance. By the distractor effect, performance of a concurrent task during path encoding causes a decrease in remembered distance. In this study, we ask the following: What are the conditions that determine whether the feature accumulation or the distractor effect dominates distortions of space? In two experiments, blindfolded participants were guided along two legs of a right triangle while reciting nonsense syllables. On some trials, one of the two legs contained features: horizontally mounted car antennas (gates) that bent out of the way as participants walked past. At the end of the second leg, participants either indicated the remembered path leg lengths using their hands in a ratio estimation task or attempted to walk, unguided, straight back to the beginning. In addition to response mode, visual access to the paths and time between encoding and response were manipulated to determine whether these factors would affect feature accumulation or distractor effects. Path legs with added features were remembered as shorter than those without, but this result was significant only in the haptic response mode data. This finding suggests that when people form spatial memory representations with the intention of navigating in room-scale spaces, interfering with information accumulation substantially distorts spatial memory.

Environment width robustly influences egocentric distance judgments.

Past work has suggested that perception of object distances in natural scenes depends on the environmental surroundings, even when the physical object distance remains constant. The cue bases for such effects remain unclear and are difficult to study systematically in real-world settings, given the challenges in manipulating large environmental features reliably and efficiently. Here, we used rendered scenes and crowdsourced data collection to address these challenges. In 4 experiments involving 452 participants, we investigated the effect of room width and depth on egocentric distance judgments. Targets were placed at distances of 2-37 meters in rendered rooms that varied in width (1.5-40 meters) and depth (6-40 meters). We found large and reliable effects of room width: Average judgments for the farthest targets in a 40-meter-wide room were between 16-33% larger than for the same target distances seen in a 1.5-meter-wide hallway. Egocentric distance cues and focal length were constant across room widths, highlighting the role of environmental context in judging distances in natural scenes. Obscuring the fine-grained ground texture, per se, is not primarily responsible for the width effect, nor does linear perspective play a strong role. However, distance judgments tended to decrease when doors and/or walls obscured more distant regions of the scene. We discuss how environmental features may be used to calibrate relative distance cues for egocentric distance judgments.

From the most fleeting of glimpses: on the time course for the extraction of distance information.

An observer's visual perception of the absolute distance between his or her position and an object is based on multiple sources of information that must be extracted during scene viewing. Research has not yet discovered the viewing duration observers need to fully extract distance information, particularly in navigable real-world environments. In a visually directed walking task, participants showed a sensitive response to distance when they were given 9-ms glimpses of floor- and eye-level targets. However, sensitivity to distance decreased markedly when targets were presented at eye level and angular size was rendered uninformative. Performance after brief viewing durations was characterized by underestimation of distance, unless the brief-viewing trials were preceded by a block of extended-viewing trials. The results indicate that experience plays a role in the extraction of information during brief glimpses. Even without prior experience, the extraction of useful information is virtually immediate when the cues of angular size or angular declination are informative for the observer.

A comparison of blindpulling and blindwalking as measures of perceived absolute distance.

Blindwalking has become a common measure of perceived absolute distance and location, but it requires a relatively large testing space and cannot be used with people for whom walking is difficult or impossible. In the present article, we describe an alternative response type that is closely matched to blindwalking in several important respects but is less resource intensive. In the blindpulling technique, participants view a target, then close their eyes and pull a length of tape or rope between the hands to indicate the remembered target distance. As with blindwalking, this response requires integration of cyclical, bilateral limb movements over time. Blind-pulling and blindwalking responses are tightly linked across a range of viewing conditions, and blindpulling is accurate when prior exposure to visually guided pulling is provided. Thus, blindpulling shows promise as a measure of perceived distance that may be used in nonambulatory populations and when the space available for testing is limited.

Automated Assessment System with Cross Reality for Neonatal Endotracheal Intubation Training.

Neonatal endotracheal intubation (ETI) is a resuscitation skill and therefore, requires an effective training regimen with acceptable success rates. However, current training regimen faces some challenges, such as the lack of visualization inside the manikin and quantification of performance, resulting in inaccurate guidance and highly variable manual assessment. We present a Cross Reality (XR) ETI simulation system which registers ETI training tools to their virtual counterparts. Thus, our system can capture all aspects of motions and visualize the entire procedure, offering instructors with sufficient information for assessment. A machine learning approach was developed to automatically evaluate the ETI performance for standardizing assessment protocols by using the performance parameters extracted from the motions and the scores from an expert rater. The classification accuracy of the machine learning algorithm is 83.5%.

The Development of a BMI-Guided Shape Morphing Technique and the Effects of an Individualized Figure Rating Scale on Self-Perception of Body Size.

The creation of personalized avatars that may be morphed to simulate realistic changes in body size is useful when studying self-perception of body size. One drawback is that these methods are resource intensive compared to rating scales that rely upon generalized drawings. Little is known about how body perception ratings compare across different methods, particularly across differing levels of personalized detail in visualizations. This knowledge is essential to inform future decisions about the appropriate tradeoff between personalized realism and resource availability. The current study aimed to determine the impact of varying degrees of personalized realism on self-perception of body size. We explored this topic in young adult women, using a generalized line drawing scale, as well as several types of personalized avatars, including 3D textured images presented in immersive virtual reality (VR). Body perception ratings using generalized line drawings were often higher than responses using individualized visualization methods. While the personalized details seemed to help with identification, there were few differences among the three conditions containing different amounts of individualized realism (e.g., photo-realistic texture). These results suggest that using scales based on personalized texture and limb dimensions are beneficial, although presentation in immersive VR may not be essential.

The various perceptions of distance: an alternative view of how effort affects distance judgments.

D. R. Proffitt and colleagues (e. g., D. R. Proffitt, J. Stefanucci, T. Banton, & W. Epstein, 2003) have suggested that objects appear farther away if more effort is required to act upon them (e.g., by having to throw a ball). The authors attempted to replicate several findings supporting this view but found no effort-related effects in a variety of conditions differing in environment, type of effort, and intention to act. Although they did find an effect of effort on verbal reports when participants were instructed to take into account nonvisual (cognitive) factors, no effort-related effect was found under apparent- and objective-distance instruction types. The authors' interpretation is that in the paradigms tested, effort manipulations are prone to influencing response calibration because they encourage participants to take nonperceptual connotations of distance into account while leaving perceived distance itself unaffected. This in no way rules out the possibility that effort influences perception in other contexts, but it does focus attention on the role of response calibration in any verbal distance estimation task.

Invalidly cued targets are well localized when detected.

Considerable attention has been devoted to understanding how objects are localized when there is ample time and attention to detect them. However, in the real world, we often must react to, or act upon, objects that we have glimpsed only briefly and are not directly at the focus of our attention. This paper describes two experiments examining the role of attentional constraints on 2-D (directional) localization, particularly in cases in which targets have been detected but are not within the spatial focus of attention. Targets were asterisks presented briefly (34-150 ms) above or below a central fixation point. Just prior to the target's appearance, a cue directed attention toward, or away from, the target. Participants indicated whether or not they saw the target, and then used a mouse to indicate the target's location. The impact of guessing was mitigated by removing trials that participants had flagged as not detected. Longer glimpses generally benefitted localization; by contrast, cue validity had very little effect on response sensitivity, bias or precision. At very brief durations, invalid cueing did result in a small increase in foveal bias. These results indicate that the directional location of objects can be extracted reasonably well from brief glimpses even with reduced attention. This directional information provides an important basis for 3-D localization of objects on the ground, via their angular declination. The current studies suggest that egocentric distance perception might be similarly robust to reduced attention when localization is based primarily on a target's angular declination.

Spatial memory during progressive disorientation.

Human spatial representations of object locations in a room-sized environment were probed for evidence that the object locations were encoded relative not just to the observer (egocentrically) but also to each other (allocentrically). Participants learned the locations of 4 objects and then were blindfolded and either (a) underwent a succession of 70 degrees and 200 degrees whole-body rotations or (b) were fully disoriented and then underwent a similar sequence of 70 degrees and 200 degrees rotations. After each rotation, participants pointed to the objects without vision. Analyses of the pointing errors suggest that as participants lost orientation, represented object directions generally "drifted" off of their true directions as an ensemble, not in random, unrelated directions. This is interpreted as evidence that object-to-object (allocentric) relationships play a large part in the human spatial updating system. However, there was also some evidence that represented object directions occasionally drifted off of their true directions independently of one another, suggesting a lack of allocentric influence. Implications regarding the interplay of egocentric and allocentric information are considered.

Misperception of exocentric directions in auditory space.

Previous studies have demonstrated large errors (over 30 degrees ) in visually perceived exocentric directions (the direction between two objects that are both displaced from the observer's location; e.g., Philbeck et al. [Philbeck, J. W., Sargent, J., Arthur, J. C., & Dopkins, S. (2008). Large manual pointing errors, but accurate verbal reports, for indications of target azimuth. Perception, 37, 511-534]). Here, we investigated whether a similar pattern occurs in auditory space. Blindfolded participants either attempted to aim a pointer at auditory targets (an exocentric task) or gave a verbal estimate of the egocentric target azimuth. Targets were located at 20-160 degrees azimuth in the right hemispace. For comparison, we also collected pointing and verbal judgments for visual targets. We found that exocentric pointing responses exhibited sizeable undershooting errors, for both auditory and visual targets, that tended to become more strongly negative as azimuth increased (up to -19 degrees for visual targets at 160 degrees ). Verbal estimates of the auditory and visual target azimuths, however, showed a dramatically different pattern, with relatively small overestimations of azimuths in the rear hemispace. At least some of the differences between verbal and pointing responses appear to be due to the frames of reference underlying the responses; when participants used the pointer to reproduce the egocentric target azimuth rather than the exocentric target direction relative to the pointer, the pattern of pointing errors more closely resembled that seen in verbal reports. These results show that there are similar distortions in perceiving exocentric directions in visual and auditory space.

The role of top-down knowledge about environmental context in egocentric distance judgments.

Judgments of egocentric distances in well-lit natural environments can differ substantially in indoor versus outdoor contexts. Visual cues (e.g., linear perspective, texture gradients) no doubt play a strong role in context-dependent judgments when cues are abundant. Here we investigated a possible top-down influence on distance judgments that might play a unique role under conditions of perceptual uncertainty: assumptions or knowledge that one is indoors or outdoors. We presented targets in a large outdoor field and in an indoor classroom. To control visual distance and depth cues between the environments, we restricted the field of view by using a 14-deg aperture. Evidence of context effects depended on the response mode: Blindfolded-walking responses were systematically shorter indoors than outdoors, whereas verbal and size gesture judgments showed no context effects. These results suggest that top-down knowledge about the environmental context does not strongly influence visually perceived egocentric distance. However, this knowledge can operate as an output-level bias, such that blindfolded-walking responses are shorter when observers' top-down knowledge indicates that they are indoors and when the size of the room is uncertain.

Spatial memory enhances the precision of angular self-motion updating.

Humans are typically able to keep track of brief changes in their head and body orientation, even when visual and auditory cues are temporarily unavailable. Determining the magnitude of one's displacement from a known location is one form of self-motion updating. Most research on self-motion updating during body rotations has focused on the role of a restricted set of sensory signals (primarily vestibular) available during self-motion. However, humans can and do internally represent spatial aspects of the environment, and little is known about how remembered spatial frameworks may impact angular self-motion updating. Here, we describe an experiment addressing this issue. Participants estimated the magnitude of passive, non-visual body rotations (40 degrees -130 degrees ), using non-visual manual pointing. Prior to each rotation, participants were either allowed full vision of the testing environment, or remained blindfolded. Within-subject response precision was dramatically enhanced when the body rotations were preceded by a visual preview of the surrounding environment; constant (signed) and absolute (unsigned) error were much less affected. These results are informative for future perceptual, cognitive, and neuropsychological studies, and demonstrate the powerful role of stored spatial representations for improving the precision of angular self-motion updating.

The Roles for Prior Visual Experience and Age on the Extraction of Egocentric Distance.

OBJECTIVES: In a well-lit room, observers can generate well-constrained estimates of the distance to an object on the floor even with just a fleeting glimpse. Performance under these conditions is typically characterized by some underestimation but improves when observers have previewed the room. Such evidence suggests that information extracted from longer durations may be stored to contribute to the perception of distance at limited time frames. Here, we examined the possibility that this stored information is used differentially across age. Specifically, we posited that older adults would rely more than younger adults on information gathered and stored at longer glimpses to judge the distance of briefly glimpsed objects. METHOD: We collected distance judgments from younger and older adults after brief target glimpses. Half of the participants were provided 20-s previews of the testing room in advance; the other half received no preview. RESULTS: Performance benefits were observed for all individuals with prior visual experience, and these were moderately more pronounced for the older adults. DISCUSSION: The results suggest that observers store contextual information gained from longer viewing durations to aid in the perception of distance at brief glimpses, and that this memory becomes more important with age.

Linking contemporary research to the classics: Celebrating 125 years at APA.

APA is celebrating 125 years this year and at the journal we are commemorating this milestone with a special issue. The inspiration came from our editorial team, who wished to acknowledge the links between game-changing articles that have influenced our research community in the past-we call them classics for short-and contemporary works. The main idea was to feature the work of nine contemporary research teams, while at the same time drawing readers' attention to their links with the classics. In this introduction, we have organized the articles according to several broad themes: active perception, perception for action, action alters perception, perception of our bodies in action, and acting on selective perceptions. As all who have read and contributed to the journal over the past few years have come to realize, it is no longer possible to study perception without considering its role in action. Nor is it possible to study action (formerly called performance, as reflected in the journal title) without understanding the perceptual contributions to action. These nine articles each exemplify, in their own way, how these dynamic interactions play out in contemporary research in our field. (PsycINFO Database Record

Asymmetrical perception of body rotation after unilateral injury to human vestibular cortex.

Vestibular information plays a key role in many perceptual and cognitive functions, but surprisingly little is known about how vestibular signals are processed at the cortical level in humans. To address this issue, we tested the ability of two patients, with damage to key components of the vestibular network in either the left or right hemisphere, to perceive passive whole-body rotations (25-125 degrees) about the yaw axis. In both patients, the posterior insula, hippocampus, putamen, and thalamus were extensively damaged. The patients' responses were compared with those of nine age- and sex-matched neurologically intact participants. The body rotations were conducted without vision and the peak angular velocities ranged from 40 degrees to 90 degrees per second. Perceived rotation was assessed by open-loop manual pointing. The right hemisphere patient exhibited poor sensitivity for body rotations toward the contralesional (left) hemispace and generally underestimated the rotations. By contrast, his judgments of rotations toward the ipsilesional (right) hemispace greatly overestimated the physical rotation by 50-70 degrees for all tested magnitudes. The left hemisphere patient's responses were more appropriately scaled for both rotation directions, falling in the low-normal range. These findings suggest that there is some degree of hemispheric specialization in the cortical processing of dynamic head rotations in the yaw plane. In this view, right hemisphere structures play a dominant role, processing rotations in both directions, while left hemisphere structures process rotations only toward the contralesional hemispace.