Egocentric Reference System Research Articles

Different strategies in pointing tasks and their impact on clinical bedside tests of spatial orientation

Deficits in spatial memory, orientation, and navigation are often early or neglected signs of degenerative and vestibular neurological disorders. A simple and reliable bedside test of these functions would be extremely relevant for diagnostic routine. Pointing at targets in the 3D environment is a basic well-trained common sensorimotor ability that provides a suitable measure. We here describe a smartphone-based pointing device using the built-in inertial sensors for analysis of pointing performance in azimuth and polar spatial coordinates. Interpretation of the vectors measured in this way is not trivial, since the individuals tested may use at least two different strategies: first, they may perform the task in an egocentric eye-based reference system by aligning the fingertip with the target retinotopically or second, by aligning the stretched arm and the index finger with the visual line of sight in allocentric world-based coordinates similar to using a rifle. The two strategies result in considerable differences of target coordinates. A pilot test with a further developed design of the device and an app for a standardized bedside utilization in five healthy volunteers revealed an overall mean deviation of less than 5° between the measured and the true coordinates. Future investigations of neurological patients comparing their performance before and after changes in body position (chair rotation) may allow differentiation of distinct orientational deficits in peripheral (vestibulopathy) or central (hippocampal or cortical) disorders.

More Personal Knowledge for More Sustainable Higher Education

Abstract The article aims at considering the characteristics of the Anthropocene era from a broader perspective and emhasizing the possibilities of pedagogy to reduce the current unsustain-ability of higher education. The relationships between human and nature are affected by the wicked problems. In particular, they are influenced by intermingling of anthropocentrism, egocentrism and egoism, which affect these relationships by causing changes in the human being, i.e., changes in sensitivity and sensibility occur that are naturally necessary for human adaptation to the environment. For the case study, we have used the processes taking place at the phenomenon level, which are known as the first-person perspective (1PP) characterized by an active and dynamic connection with the environment. It should be noted that 1PP cannot be observed from a distance, as there are a number of interrelated processes that begin with the effects of the environment, the formation of the “self” and the formation of the self-image. It follows that complex consciousness in the 1PP is implemented within an egocentric reference system, where experience is structured according to the image of the human body. The article will present the findings of 1PP study obtained by performing two tasks: (1) development of a personally significant view of a 1PP researcher on the phenomenon of sustainability from an egocentric perspective and (2) involvement of the 1PP researcher in adaptive learning suitable for pandemic conditions. We would like to stress that the case study has been developed as our reaction to the intensification of unsustainable development in the relationship between nature and human, which has been initiated and maintained by the tangle of Anthropocene problems. From the pedagogical perspective, we looked for an opportunity to use the basis of the natural origin of human and nature relations to maintain more integrated activities and more personal knowledge, so that the development of more sustainable higher education could be promoted by means of personal experience. Through the pedagogical lenses of phenomenology, we identified the need to reduce the impact of the Anthropocene tangle through the use of more natural methods. We also recognized the need to use the 1PP and adaptive learning opportunities more carefully. In this way, pedagogy can gain new experiences for a more holistic understanding of individual experience and enhance the use of the unique abilities of adaptive learning to prototype more personal knowledge in order to build more sustainable higher education.

North in the head: spatial reference frame and map orientation

North in the head: spatial reference frame and map orientation

Visuospatial bias in line bisection in Williams syndrome.

Recently, a study using the subjective straight-ahead task showed that individuals with Williams syndrome (WS) present a bias in the representation of body perception. The aim of the present study is to examine the horizontal midline body representation in WS participants using the bisection line task, which is an important benchmark for an egocentric frame of reference. Fifteen WS participants (mean age=21.7±9.5years) were compared with two typical development control groups: one composed of 15 participants matched on chronological age and one composed of 15 children matched on mental age. The task consisted of dividing each line in a series of 18 lines into two equal halves by drawing a vertical mark with a pencil in the centre of the line. Individuals with WS presented a significant leftward bias in comparison to mental age and chronological age groups. The leftward deviation in WS could be linked to the body representation bias and difficulties in the development of the egocentric reference system. An early detection of such deviation should help in the development of targeted interventions for WS individuals to improve visual-spatial skills and learning.

The use of front–back arrays by young children to code locations

Research suggests that during the first 2years of life, children use an egocentric reference system and an extrinsic reference frame, the latter being one allocentric reference system, to encode locations. However, little is known about children’s use of an object’s intrinsic structure, another allocentric reference system. The current study focused on the role of the front–back relationship, one of the simplest intrinsic reference frames, in children’s location encoding. Children (3- to 5-year-olds) participated in a hide-and-find game with one of three different intrinsic front–back array conditions: a facet-induced front–back array, a motion-induced front–back array, or no array. The results showed that whereas the ability to use a facet-induced front–back array began by 3years of age, children used a motion-induced front–back array to encode locations at 4years of age. These results provide evidence that the developmental trajectories of using an intrinsic reference frame to encode locations vary and depend on the specific spatial array involved.

Where is the 'subjective straight ahead' in Williams syndrome?

Individuals with Williams Syndrome (WS) are known to have particular difficulties when performing visuo-spatial tasks, which could be related to their difficulties in using a specific reference system to determine spatial relations. The aim of the present study was to assess the internal representation of the body's sagittal plane, which is an important benchmark for an egocentric frame of reference. The results of 18 WS individuals (mean age=20.5±9.2years) on the subjective straight ahead (SSA) task were compared with those of two healthy control groups composed of 36 participants matched on chronological age matched on chronological age (CA) and 30 young children matched on non-verbal intellectual ability (YC). Individuals with WS showed a significant left deviation on the SSA body's sagittal plane representation compared with the chronological age control group and a marginal left deviation compared with the young children control group. A comparison with the objective SA (0°) showed a significant leftward deviation in the WS group but not in the two control groups. Individuals with WS showed a significant leftward deviation in the SSA task. This bias of the body's longitudinal axe representation could have a negative impact on the use of an egocentric reference system, which could be the cause for their difficulties in defining spatial relations (e.g. location and orientation) necessary for performing spatial tasks.

Asymmetric representations of upper and lower visual fields in egocentric and allocentric references.

Two spatial reference systems, i.e., the observer-centered (egocentric) and object-centered (allocentric) references, are most commonly used to locate the position of the external objects in space. Although we sense the world as a unified entity, visual processing is asymmetric between upper and lower visual fields (VFs). For example, the goal-directed reaching responses are more efficient in the lower VF. Such asymmetry suggests that the visual space might be composed of different realms regarding perception and action. Since the peripersonal realm includes the space that one can reach, mostly in the lower VF, it is highly likely that the peripersonal realm might mainly be represented in the egocentric reference for visuomotor operation. In contrast, the extrapersonal realm takes place away from the observer and is mostly observed in the upper VF, which is presumably represented in the allocentric reference for orientation in topographically defined space. This theory, however, has not been thoroughly tested experimentally. In the present study, we assessed the contributions of the egocentric and allocentric reference systems on visual discrimination in the upper and lower VFs through measuring the manual reaction times (RTs) of human subjects. We found that: (a) the influence of a target's egocentric location on visual discrimination was stronger in the lower VF; and (b) the influence of a target's allocentric location on visual discrimination was stronger in the upper VF. These results support the hypothesis that the upper and lower VFs are primarily represented in the allocentric and egocentric references, respectively.

Topographical disorientation in patients with brain impairment

Topographical disorientation refers to inability to recognize the environment, as well as to orient, to find the right way into a familiar or new environment and to use a map for the orientation. These functions are based on neuronal activity of posterior parietal cortex, retrosplenial cortex and the posterior part of cingular gyrus, medial temporal lobe, lingual gyrus and prefrontal cortex and are considered within egocentric or allocentric (exocentric) reference systems. Object locations in the egocentric system are evaluated with respect to the subject's body position while object locations in the allocentric reference frame are evaluated with respect to the object-to-object relations in the external environment. Topographical orientation disorders are observed in local lesions of the brain and in neurodegenerative diseases. The topographical disorientation may be due to landmark аgnosia, egocentric disorientation, heading disorientation and anterograde disorientation. Clinical tests for the diagnosis of topographical disorientation include blanket methods and navigation tasks in real or virtual space. The restorative and compensatory strategies are used in rehabilitation of patients with topographical disorientation. Clarification of the general strategy and selection of the optimal neurorehabilitation methods depend on the causes and severity of brain lesions.

How directions of route descriptions influence orientation specificity: the contribution of spatial abilities.

Previous studies found mental representations of route descriptions north-up oriented when egocentric experience (given by the protagonist's initial view) was congruent with the global reference system. This study examines: (a) the development and maintenance of representations derived from descriptions when the egocentric and global reference systems are congruent or incongruent; and (b) how spatial abilities modulate these representations. Sixty participants (in two groups of 30) heard route descriptions of a protagonist's moves starting from the bottom of a layout and headed mainly northwards (SN description) in one group, and headed south from the top (NS description, the egocentric view facing in the opposite direction to the canonical north) in the other. Description recall was tested with map drawing (after hearing the description a first and second time; i.e. Time 1 and 2) and South-North (SN) or North-South (NS) pointing tasks; and spatial objective tasks were administered. The results showed that: (a) the drawings were more rotated in NS than in SN descriptions, and performed better at Time 2 than at Time 1 for both types of description; SN pointing was more accurate than NS pointing for the SN description, while SN and NS pointing accuracy did not differ for the NS description; (b) spatial (rotation) abilities were related to recall accuracy for both types of description, but were more so for the NS ones. Overall, our results showed that the way in which spatial information is conveyed (with/without congruence between the egocentric and global reference systems) and spatial abilities influence the development and maintenance of mental representations.

Blind individuals represent the auditory space in an egocentric rather than allocentric reference frame

It is not clear to date how visual deprivation affects auditory spatial perception. Recent psychophysical evidences described a spatial auditory deficit in congenitally blind individuals while some others found a spatial auditory improvement. Particularly, Gori, Sandini, Martinoli, & Burr (2014) and Vercillo, Milne, Gori, & Goodale (2015) reported that people who were born blind were less efficient in localizing sound sources with respect to auditory landmarks than sighted individuals. On the other side, blind people performed similarly or even better than sighted participants during the localization of single sound sources. We investigated auditory spatial perception in early blind using different auditory spatial tasks and found that blind individuals did not succeed in localizing sound sources in an external frame of reference. The performance of early blind was severely impaired during the localization of brief auditory stimuli with respect to acoustic landmarks (allocentric frame of reference) but was comparable to that one of sighted participants when they had to localize sounds with respect to their own body (egocentric reference frame). Our results suggest that, after early visual deprivation, auditory spatial perception is centered on an egocentric reference system.

An egocentric semantic reference system for affordances

This article suggests a theory of egocentric semantic reference systems for human observations of affordances that can be used to semantically account for subjective human observations on the web. Based on the perceptual theory of affordances, which suggests that humans perceive the potential actions the environment affords, an egocentric semantic reference frame is established, which is anchored in the observer’s specific capabilities for perception and action. The theory is completed with transformations that allow to project values of observed affordances from one user’s ordinal reference frame into another user’s ordinal reference frame. The potency of the theory to capture the semantics of human observations is demonstrated through the implementation of a full fledged egocentric semantic reference system for the prototypical affordance of hikability that a mountain path affords to a hiker. The prototype uses real user-ratings from a community driven web portal.

Toward a definition of intrinsic axes: The effect of orthogonality and symmetry on the preferred direction of spatial memory.

Mou, Zhao, and McNamara (2007) proposed the "intrinsic model of human spatial memory," which posits that a viewer's memory of an array of objects will exhibit a preferred direction that is aligned with an intrinsic axis of the array. They defined intrinsic axes as salient axes created in part by the physical (geometric) properties of the array. To date, these geometric characteristics have received little research attention. We begin such an endeavor by evaluating the role of symmetry and orthogonality (i.e., number of right angles in an array of objects) in spatial memory. Participants viewed a layout of objects from a single (Experiment 1) viewpoint or 2 (Experiment 2) viewpoints and then judged relative directions within the layout from memory. Orthogonality and symmetry were associated with decreased reliance on egocentric reference systems but were qualified by a generally greater reliance on egocentric reference frames than is common in the literature. Indeed, for only 1 array-a highly orthogonal and symmetric one-did participants consistently respond nonegocentrically. We suggest that overuse of this array in the literature has led to an overestimation of the importance of allocentricity in spatial memory.

Spatial reference of black capuchin monkeys in Brazilian Atlantic Forest: egocentric or allocentric?

Wild primates occupy large home ranges and travel long distances to reach goals. However, how primates are able to remember goal locations and travel efficiently is unclear. Few studies present consistent results regarding what reference system primates use to navigate, and what kind of spatial information they recognize. We analysed the pattern of navigation of one wild group of black capuchin monkeys, Cebus nigritus , at Atlantic Forest for 100 days in Carlos Botelho State Park (PECB), Brazil. We tested predictions based on the alternative hypotheses that black capuchin monkeys navigate using a sequence of landmarks as an egocentric reference system or an allocentric reference system, or both, depending on availability of food resources. The group location was recorded using a GPS device collecting coordinates at 5 min intervals, and route maps were generated using ArcView v9.3.1. The study group travelled through habitual routes during less than 30% of our study sample, and revisited resources from different starting points, using different paths and routes, even when prominent landmarks near feeding locations were not visible. The study group used habitual routes more frequently when high-quality foods were scarce, and navigated using different paths when revisiting food sources. Results support the hypothesis that black capuchin monkeys at PECB navigate using both egocentric and allocentric systems of reference, depending on the quality and distribution of the food resource they find.

Frame of Reference in the Mental Representation of Objects Layout

Frame of Reference in the Mental Representation of Objects Layout

The egocentric reference for visual exploration and orientation

Clinical signs of damage to the egocentric reference system range from the inability to detect stimuli in the real environment to a defect in recovering items from an internal representation. Despite clinical dissociations, current interpretations consider all symptoms as due to a single perturbation, differentially expressed according to the medium explored (perceptual or representational). We propose an alternative account based on the functional distinction between two separate egocentric mechanisms: one allowing construction of the immediate point of view, the other extracting a required perspective within a mental representation. Support to this claim comes from recent results in the domain of navigation, showing that separate cognitive mechanisms maintain the egocentric reference when actively exploring the visual space as opposed to moving according to an internal map. These mechanisms likely follow separate developmental pathways, seemingly depend on distinct neural pathways and are used independently by healthy adults, reflecting task demands and individual cognitive style. Implications for spatial cognition and social skills are discussed.

Are Rotations in Perceived Visual Vertical and Body Axis After Stroke Caused by the Same Mechanism?

The aim of this study was to investigate whether allocentric and egocentric coordinate systems are congruently biased after hemisphere stroke, which would suggest a single underlying mechanism. The perception of the long body axis (LBA), an egocentric reference, and that of the subjective visual vertical (SVV), an allocentric reference, was assessed in both the upright position and with 30 degrees lateral body tilts in 15 patients with a hemisphere stroke and 12 control subjects. In control subjects, estimates were accurate in upright but rotated in tilted positions (LBA 7 degrees +/-6 degrees overestimation and SVV 8.8 degrees +/-7.8 degrees toward the body). In patients, SVV (-4.4 degrees +/-4.6 degrees ) and LBA (-4.8 degrees +/-5.3 degrees ) were congruent in upright positions and when patients were ipsilesionally tilted (1.5 degrees +/-7 degrees and 1.9 degrees +/-7 degrees , respectively). In contrast, SVV and LBA were dissociated when the body was tilted to the contralesional side with overestimation of the LBA (-9.2 degrees +/-4.6 degrees ) but no effect on SVV (-4.1 degrees +/-6.4 degrees ). Because rotations in egocentric and allocentric reference systems found after stroke are differently modulated by lateral tilts, they are not due to a single underlying mechanism. However, they share common bases and can be simultaneously reduced by ipsilesional body tilt. Differences in the way somesthetic information is integrated may explain the differences in LBA and SVV.

Isolating observer-based reference directions in human spatial memory: Head, body, and the self-to-array axis

Several lines of research have suggested the importance of egocentric reference systems for determining how the spatial properties of one’s environment are mentally organized. Yet relatively little is known about the bases for egocentric reference systems in human spatial memory. In three experiments, we examine the relative importance of observer-based reference directions in human memory by controlling the orientation of head and body during acquisition. Experiment 1 suggests that spatial memory is organized by a head-aligned reference direction; however, Experiment 2 shows that a body-aligned reference direction can be more influential than a head-aligned direction when the axis defined by the relative positions of the observer and the learned environment (the “self-to-array” axis) is properly controlled. A third experiment shows that the self-to-array axis is distinct from – and can dominate – retina, head, and body-based egocentric reference systems.

Visuospatial neglect in near and far space: dissociation between line bisection and letter cancellation

The differential performance on a line bisection and a cancellation task in near and far space was studied. A group of 10 patients with severe left-sided visuospatial neglect and a group of 10 right-brain damaged patients without neglect were examined. The stimuli were presented at a distance of 60 cm (near space) and 160 cm (far space), respectively, and corrected for visual angle. In the line bisection task, patients were asked to point to the estimated line centre with a pencil (near space) or a stick (far space). In the cancellation task, patients pointed to all target stimuli they could detect using either a pencil (near space) or a stick (far space). Most patients with left hemineglect showed a more prominent neglect in far space as compared to near space for the line bisection task, whereas no difference of performance between near and far space was found in the control patients. In contrast, no group showed a distance effect in the cancellation task. The observation that only line bisection is influenced by the distance of the stimulus suggests that line bisection and cancellation are processed differentially. It is proposed that line bisection requires an allocentric reference system focusing attention on objects, whereas cancellation tasks are based on an egocentric reference system responsible for visuospatial attention. Our results indicate that distance changes perception within the allocentric but not within the egocentric system.

Frames of reference in spatial memories acquired from language.

Four experiments examined reference systems in spatial memories acquired from language. Participants read narratives that located 4 objects in canonical (front, back, left, right) or noncanonical (left front, right front, left back, right back) positions around them. Participants' focus of attention was first set on each of the 4 objects, and then they were asked to report the name of the object at the location indicated by a direction word or an iconic arrow. The results indicated that spatial memories were represented in terms of intrinsic (object-to-object) reference systems, which were selected using egocentric cues (e.g., alignment with body axes). Results also indicated that linguistic direction cues were comprehended in terms of egocentric reference systems, whereas iconic arrows were not.

Perceiving Object Rotations — Effects of Egocentric Perspective and Observer Orientation

Indicating the orientation of the axis of rotation of a rotating object is a fundamental part of an operator's ability to understand the motion of the object. Prior research has shown that this ability depends heavily on the orientation of the rotational axis with respect to the observer, the environment and the object. The present study is the first to distinguish between the involvement of egocentric and environment-centered spatial reference systems in rotation perception. Observers indicated the orientation of the axis of rotation for visually displayed motion while sitting upright or being tilted sideways or backwards. Accuracy and response time were recorded. The results showed that egocentric and environment-centered reference systems appear to play differential roles in the ability to accurately indicate the axis of rotation depending on the orientation of the observer. Theoretical and practical implications are discussed.