Judgments of Object Size and Distance across Different Virtual Reality Environments: A Preliminary Study

Emerging technologies offer the potential to expand the domain of the future workforce to extreme environments, such as outer space and alien terrains. To understand how humans navigate in such environments that lack familiar spatial cues this study examined spatial perception in three types of environments. The environments were simulated using virtual reality. We examined participants’ ability to estimate the size and distance of stimuli under conditions of minimal, moderate, or maximum visual cues, corresponding to an environment simulating outer space, an alien terrain, or a typical cityscape, respectively. The findings show underestimation of distance in both the maximum and the minimum visual cue environment but a tendency for overestimation of distance in the moderate environment. We further observed that depth estimation was substantially better in the minimum environment than in the other two environments. However, estimation of height was more accurate in the environment with maximum cues (cityscape) than the environment with minimum cues (outer space). More generally, our results suggest that familiar visual cues facilitated better estimation of size and distance than unfamiliar cues. In fact, the presence of unfamiliar, and perhaps misleading visual cues (characterizing the alien terrain environment), was more disruptive than an environment with a total absence of visual cues for distance and size perception. The findings have implications for training workers to better adapt to extreme environments.

Body Representation in Anorexia Nervosa

Anorexia nervosa (AN) is an eating disorder that mainly affects young women. One of the most striking symptoms of this disorder is the distorted experience of body size and shape. Patients are by definition underweight, but experience and perceive their body as bigger than it in reality is. This body representation disturbance has fascinated scientists for many decades, leading to a rich and diverse body of literature on this topic. Research shows that AN patients do not only think that their body is bigger than reality, and visually perceive it as such, but that other sensory modalities also play an important role in oversized body experiences. Patients for example have an altered (enlarged) size perception of tactile stimuli, and move their body as if it is larger than it actually is. Moreover, patients with AN appear to process and integrate multisensory information differently than healthy individuals, especially in relation to body size. This leads to the conclusion that the representation of the size of the body in the brain is enlarged. This conclusion has important implications for the treatment of body representation disturbances in AN. Traditionally treatment of AN is very cognitive in nature, it is possible however that changed cognitions with respect to body size experiences do not lead to actual changes in metric representations of body size stored in the brain. Recently a few studies have been published in which a multisensory approach in treatment of body representation disturbance in AN has been found to be effective in treating this symptom of AN.

Pictorial size perception in schizophrenia

In this study, we compared visual pictorial size perception between healthy volunteers (CG) and an experimental group (EG) of people diagnosed with schizophrenia. We have been using paintings by Salvador Dalí and Rorschach plates to estimate visual pictorial size perception. In this transversal, ex post facto, and quasi-experimental study, we observed differences between EG and CG. Schizophrenic in-patients perceived sizes about 1.3-fold greater than healthy volunteers (p=0.006), implying that pictorial size perception is altered in some way in schizophrenia. Considering the present and previous results, this measurement of diameter size of first pictorial perception may be a useful estimate of some aspects of perceptual alterations that may be associated with psychotic symptoms in prodromal and acute schizophrenic episodes and other related mental states. Eventually, this may help in preventing people from evolving to acute episodes.

Role of the Dorsal Posterior Parietal Cortex in the Accurate Perception of Object Magnitude in Peripheral Vision

Following superior parietal lobule and intraparietal sulcus (SPL-IPS) damage, optic ataxia patients underestimate the distance of objects in the ataxic visual field such that they produce hypometric pointing errors. The metrics of these pointing errors relative to visual target eccentricity fit the cortical magnification of central vision. The SPL-IPS would therefore implement an active “peripheral magnification” to match the real metrics of the environment for accurate action. We further hypothesized that this active compensation of the central magnification by the SPL-IPS contributes to actual object’ size perception in peripheral vision. Three optic ataxia patients and 10 age-matched controls were assessed in comparing the thickness of two rectangles flashed simultaneously, one in central and another in peripheral vision. The bilateral optic ataxia patient exhibited exaggerated underestimation bias and uncertainty compared to the control group in both visual fields. The two unilateral optic ataxia patients exhibited a pathological asymmetry between visual fields: size perception performance was affected in their contralesional peripheral visual field compared to their healthy side. These results demonstrate that the SPL-IPS contributes to accurate size perception in peripheral vision.

The Influence of Induced Emotions on Distance and Size Perception and on the Grip Scaling During Grasping

Previous studies have shown that our perception of stimulus properties can be affected by the emotional nature of the stimulus. It is not clear, however, how emotions affect visually-guided actions toward objects. To address this question, we used toy rats, toy squirrels, and wooden blocks to induce negative, positive, and neutral emotions, respectively. Participants were asked to report the perceived distance and the perceived size of a target object resting on top of one of the three emotion-inducing objects; or to grasp the same target object either without visual feedback (open-loop) or with visual feedback (closed-loop) of both the target object and their grasping hand during the execution of grasping. We found that the target object was perceived closer and larger, but was grasped with a smaller grip aperture in the rat condition than in the squirrel and the wooden-block conditions when no visual feedback was available. With visual feedback present, this difference in grip aperture disappeared. These results showed that negative emotion influences both perceived size and grip aperture, but in opposite directions (larger perceived size but smaller grip aperture) and its influence on grip aperture could be corrected by visual feedback, which revealed different effects of emotion to perception and action. Our results have implications on the understanding of the relationship between perception and action in emotional condition, which showed the novel difference from previous theories.

Can Assessing Physical Activity Liking Identify Opportunities to Promote Physical Activity Engagement and Healthy Dietary Behaviors?

Improving our understanding of what physical activities are enjoyed and the factors that are associated with physical activity liking can promote participation in regular physical activity. We aimed to study physical activity (PA) liking in college women by modelling interactions between body size perception and dietary behaviors on PA liking, and by examining discrepancies between PA liking versus engagement on body size perception and dietary behaviors. Women (n = 251; 74% white) utilized an online survey to report their level of liking for PA types (scored into a PA liking index) and frequency of PA participation. They also reported their perceived body size, level of dietary restraint, and frequency of consuming foods (scored into a diet quality index). In multivariate analyses, a greater perceived body size was directly associated with lower PA liking and indirectly through greater dietary restraint but lower diet quality. Healthiest dietary behaviors were reported by women who both liked and engaged in PA. Women who reported high PA liking but low PA participation reported a higher dietary restraint and lower diet quality. These findings support the empowerment of women across all body sizes to identify physical activities that they enjoy. Health promotion efforts should encourage women to couple physical activity liking and engagement with a healthy level of dietary restraint and consumption of a healthy diet.

Grasp aperture corrections in reach-to-grasp movements do not reliably alter size perception

When grasping an object, the opening between the fingertips (grip aperture) scales with the size of the object. If an object changes in size, the grip aperture has to be corrected. In this study, it was investigated whether such corrections would influence the perceived size of objects. The grasping plan was manipulated with a preview of the object, after which participants initiated their reaching movement without vision. In a minority of the grasps, the object changed in size after the preview and participants had to adjust their grasping movement. Visual feedback was manipulated in two experiments. In experiment 1, vision was restored during reach and both visual and haptic information was available to correct the grasp and lift the object. In experiment 2, no visual information was provided during the movement and grasps could only be corrected using haptic information. Participants made reach-to-grasp movements towards two objects and compared these in size. Results showed that participants adjusted their grasp to a change in object size from preview to grasped object in both experiments. However, a change in object size did not bias the perception of object size or alter discrimination performance. In experiment 2, a small perceptual bias was found when objects changed from large to small. However, this bias was much smaller than the difference that could be discriminated and could not be considered meaningful. Therefore, it can be concluded that the planning and execution of reach-to-grasp movements do not reliably affect the perception of object size.