Jack M. Loomis

Visual space perception and visually directed action

The results of two types of experiments are reported. In 1 type, Ss matched depth intervals on the ground plane that appeared equal to frontal intervals at the same distance. The depth intervals had to be made considerably larger than the frontal intervals to appear equal in length, with this physical inequality of equal-appearing intervals increasing with egocentric distance of the intervals (4 m-12 m). In the other type of experiment, Ss viewed targets lying on the ground plane and then, with eyes closed, attempted either to walk directly to their locations or to point continuously toward them while walking along paths that passed off to the side. Performance was quite accurate in both motoric tasks, indicating that the distortion in the mapping from physical to visual space evident in the visual matching task does not manifest itself in the visually open-loop motoric tasks.

Nonvisual Navigation by Blind and Sighted: Assessment of Path Integration Ability

Blindfolded sighted, adventitiously blind, and congenitally blind subjects performed a set of navigation tasks. The more complex tasks involved spatial inference and included retracing a multisegment route in reverse, returning directly to an origin after being led over linear segments, and pointing to targets after locomotion. As a group, subjects responded systematically to route manipulations in the complex tasks, but performance was poor. Patterns of error and response latency are informative about the internal representation used; in particular, they do not support the hypothesis that only a representation of the origin of locomotion is maintained. The slight performance differences between groups varying in visual experience were neither large nor consistent across tasks. Results provide little indication that spatial competence strongly depends on prior visual experience.

TARGET ARTICLE: Immersive Virtual Environment Technology as a Methodological Tool for Social Psychology

Historically, at least 3 methodological problems have dogged experimental social psychology: the experimental control-mundane realism trade-off, lack of replication, and unrepresentative sampling. We argue that immersive virtual environment technology (IVET) can help ameliorate, if not solve, these methodological problems and, thus, holds promise as a new social psychological research tool. In this article, we first present an overview of IVET and review IVET-based research within psychology and other fields. Next, we propose a general model of social influence within immersive virtual environments and present some preliminary findings regarding its utility for social psychology. Finally, we present a new paradigm for experimental social psychology that may enable researchers to unravel the very fabric of social interaction.

Immersive virtual environment technology as a basic research tool in psychology

Immersive virtual environment (IVE) technology has great promise as a tool for basic experimental research in psychology. IVE technology gives participants the experience of being surrounded by the computer-synthesized environment. We begin with a discussion of the various devices needed to implement immersive virtual environments, including object manipulation and social interaction. We review the benefits and drawbacks associated with virtual environment technology, in comparison with more conventional ways of doing basic experimental research. We then consider a variety of examples of research using IVE technology in the areas of perception, spatial cognition, and social interaction.

Interpersonal Distance in Immersive Virtual Environments

Digital immersive virtual environment technology (IVET) enables behavioral scientists to conduct ecologically realistic experiments with near-perfect experimental control. The authors employed IVET to study the interpersonal distance maintained between participants and virtual humans. In Study 1, participants traversed a three-dimensional virtual room in which a virtual human stood. In Study 2, a virtual human approached participants. In both studies, participant gender, virtual human gender, virtual human gaze behavior, and whether virtual humans were allegedly controlled by humans (i.e., avatars) or computers (i.e., agents) were varied. Results indicated that participants maintained greater distance from virtual humans when approaching their fronts compared to their backs. In addition, participants gave more personal space to virtual agents who engaged them in mutual gaze. Moreover, when virtual humans invaded their personal space, participants moved farthest from virtual human agents. The advantages and disadvantages of IVET for the study of human behavior are discussed.

Optical Velocity Patterns, Velocity-Sensitive Neurons, and Space Perception: A Hypothesis

A hypothesis is put forward of how global patterns of optical flow, as discussed by Gibson, Johansson, and others, could be processed by relatively simple physiological mechanisms. It is suggested that there may exist motion-sensitive cells in the visual system which operate on the optical flow over the retina, and, in so doing, structure the visual field in terms of distinct surfaces that move and/or lie at varying distances from the observer. First, concepts of static and dynamic perspective relative to a sphere centered about the eye are developed, partly on the basis of the work of Gordon. It is pointed out that the velocity flow pattern has a very simple form making it amenable to analysis by relatively low-level mechanisms. Next a higher-order variable of optical flow, the ‘convexity’, is defined; under the assumption of a rigid environment, convexity is shown to be related to relative depth. It is then postulated that velocity-sensitive cells having center—surround organization could be linked in such a way as to define a higher-order cell, the convexity cell, having functional properties that make it sensitive to the convexity function. The response profile of a layer of such cells would provide an efficient structuring of the visual field in terms of distinct optical surfaces. Relevant evidence is briefly discussed. Lastly, the optical flow patterns corresponding to rotations of the observer are considered. It is shown that the convexity cell is insensitive to rotations and in consequence responds in an invariant fashion to aspects of the optical flow which are related to the surrounding environment.

Spatial Updating of Self-Position and Orientation During Real, Imagined, and Virtual Locomotion

Two studies investigated updating of self-position and heading during real, imagined, and simulated locomotion. Subjects were exposed to a two-segment path with a turn between segments; they responded by turning to face the origin as they would if they had walked the path and were at the end of the second segment. The conditions of pathway exposure included physical walking, imagined walking from a verbal description, watching another person walk, and experiencing optic flow that simulated walking, with or without a physical turn between the path segments. If subjects failed to update an internal representation of heading, but did encode the pathway trajectory, they should have overturned by the magnitude of the turn between the path segments. Such systematic overturning was found in the description and watching conditions, but not with physical walking. Simulated optic flow was not by itself sufficient to induce spatial updating that supported correct turn responses.

Locomotion Mode Affects the Updating of Objects Encountered During Travel: The Contribution of Vestibular and Proprioceptive Inputs to Path Integration

In two experiments, subjects traveled through virtual mazes, encountering target objects along the way. Their task was to indicate the direction to these target objects from a terminal location in the maze (from which the objects could no longer be seen). Subjects controlled their motion through the mazes using three locomotion modes. In the Walk mode, subjects walked normally in the experimental room. For each subject, body position and heading were tracked, and the tracking information was used to continuously update the visual imagery presented to the subjects on a head-mounted display. This process created the impression of immersion in the experimental maze. In the Visual Turn mode subjects moved through the environment using a joystick to control their turning. The only sensory information subjects received about rotation and translation was that provided by the computer-generated imagery. The Real Turn mode was midway between the other two modes, in that subjects physically turned in place to steer while translating in the virtual maze; thus translation through the maze was signaled only by the computer-generated imagery, whereas rotations were signaled by the imagery as well as by proprioceptive and vestibular information. The dependent measure in the experiment was the absolute error of the subjects directional estimate to each target from the terminal location. Performance in the Walk mode was significantly better than in the Visual Turn mode but other trends were not significant. A secondary finding was that the degree of motion sickness depended upon locomotion mode, with the lowest incidence occurring in the Walk mode. Both findings suggest the advisability of having subjects explore virtual environments using real rotations and translations in tasks involving spatial orientation.

Does the quality of the computer graphics matter when judging distances in visually immersive environments

In the real world, people are quite accurate in judging distances to locations in the environment, at least for targets resting on the ground plane and distances out to about 20 m. Distance judgments in visually immersive environments are much less accurate. Several studies have now shown that in visually immersive environments, the world appears significantly smaller than intended. This study investigates whether or not the compression in apparent distances is the result of the low-quality computer graphics utilized in previous investigations. Visually directed triangulated walking was used to assess distance judgments in the real world and in three virtual environments with graphical renderings of varying quality.

Navigation System for the Blind: Auditory Display Modes and Guidance

The research we are reporting here is part of our effort to develop a navigation system for the blind. Our long-term goal is to create a portable, self-contained system that will allow visually impaired individuals to travel through familiar and unfamiliar environments without the assistance of guides. The system, as it exists now, consists of the following functional components: (1) a module for determining the travelers position and orientation in space, (2) a Geographic Information System comprising a detailed database of our test site and software for route planning and for obtaining information from the database, and (3) the user interface. The experiment reported here is concerned with one function of the navigation system: guiding the traveler along a predefined route. We evaluate guidance performance as a function of four different display modes: one involving spatialized sound from a virtual acoustic display, and three involving verbal commands issued by a synthetic speech display. The virtual display mode fared best in terms of both guidance performance and user preferences.