Dissociation between Visual Perception of Allocentric Distance and Visually Directed Walking of its Extent

Abstract

Walking without vision to previously viewed targets was compared with visual perception of allocentric distance in two experiments. Experimental evidence had shown that physically equal distances in a sagittal plane on the ground were perceptually underestimated as compared with those in a frontoparallel plane, even under full-cue conditions. In spite of this perceptual anisotropy of space, Loomis et al (1992 Journal of Experimental Psychology. Human Perception and Performance 18 906-921) found that subjects could match both types of distances in a blind-walking task. In experiment 1 of the present study, subjects were required to reproduce the extent of allocentric distance between two targets by either walking towards the targets, or by walking in a direction incompatible with the locations of the targets. The latter condition required subjects to derive an accurate allocentric distance from information based on the perceived locations of the two targets. The walked distance in the two conditions was almost identical whether the two targets were presented in depth (depth-presentation condition) or in the frontoparallel plane (width-presentation condition). The results of a perceptual-matching task showed that the depth distances had to be much greater than the width distances in order to be judged to be equal in length (depth compression). In experiment 2, subjects were required to reproduce the extent of allocentric distance from the viewing point by blindly walking in a direction other than toward the targets. The walked distance in the depth-presentation condition was shorter than that in the width-presentation condition. This anisotropy in motor responses, however, was mainly caused by apparent overestimation of length oriented in width, not by depth compression. In addition, the walked distances were much better scaled than those in experiment 1. These results suggest that the perceptual and motor systems share a common representation of the location of targets, whereas a dissociation in allocentric distance exists between the two systems in full-cue conditions.

Frontal extents in virtual environments are not immune to underperception

“…This result replicates numerous real world studies showing that stimulus orientation affects perceived exocentric distance (Kudoh, 2005;Levin & Haber, 1993;Li et al, 2013;Loomis et al, 1992Loomis et al, , 2002; but see the real world conditions of Geuss et al, 2012, andKelly, Loomis, &. Furthermore, judgments of both frontal and depth extents were smaller in the grass VE than the room VE.…”

“…According to Li et al, accurate judgment of frontal extents in the VE could arise from a fortunate balance of underperception caused by the VE and overperception of frontal relative to depth extents (Kudoh, 2005;Levin & Haber, 1993;Loomis, Da Silva, Fujita, & Fukusima, 1992;Loomis, Philbeck, & Zahorik, 2002). Li et al (2013) provide evidence for this alternative hypothesis by showing that pantomime walking judgments were larger for frontal compared to depth extents in a real environment and in a virtual environment, but that all extents were perceived as shorter in the virtual compared to real environment, resulting in relatively accurate walking judgments of frontal extents in the VE.…”

One-Dimensional and Multi-Dimensional Studies of the Exocentric Distance Estimates in Frontoparallel Plane, Virtual Space, and Outdoor Open Field

“…The assistant's height must serve as a hint to determine egocentric distances. However, we claim the validity of these data, as our task was to match an exocentric distance, and research evidence indicates that there is a dissociation between visual perception for ego-and exocentric distances (Kudoh, 2005;Loomis et al, 1992), and also there was independence between distance and size perception (Haber & Levin, 2001). …”

Gaze-Centered Updating of Remembered Visual Space During Active Whole-Body Translations

“…According to this hypothesis, the brain codes remembered space irrespective of gaze fixation and therefore predicts no such reversal of updating errors if translations are misjudged. We emphasize that the central premise behind our test was that subjects misestimate their traveled distance during self-generation motion as shown by many studies (Glasauer et al 1994;Israel et al 1993;Kudoh 2005;Medendorp et al 1999;Philbeck and Loomis 1997), although the exact explanation for why this occurs is not directly relevant (but see later). Our results show that target updating for translational motion is compromised by small errors, which increase with depth from fixation and reverse in direction for opposite depths from fixation.…”