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,

Two studies invesligated updaling q[' se!f-position and heading dwinx real. imagined, wld simuh#ed locomotion. Snl/ects wel'e e.-los('d to (1 IWO-S(',k qHellt pttl]l with a titI'll between segnlentx.' they ,.ponded by tin'rang to,bee the ori,,in as they would if they had walked the path }nd were at the end ' the second stsment. The conalllions q['pathwG eA7oaw'e int htded physical walking. intaxined ,valking j)'om a verbal description. watchbtg another person wall and eperiencing optic flow that simulated walkinx. with or without a phys- ical turn between the path segments. tf .sldgects fitlied to npdaw an internal representation g' heading, but did encode tile pathway tl'ajeo tory. they xhottkl httve overturlcd hv the magnitltde 'the turn between the patJ segments. 5nch svslemalic overturnbig was ./bund in the description and watching comlitions, but not with physical walking. Simulated optic flow was not by itse'sttt'ient to induce spatial ttpdat- ing j/tat supported correct turn t'espon.cs+ An important component of navigation is updating knowledge of one's spatial position and orientation. People navigating on foot receive multiple cues for updating, Vision signals sclf-nolion by the changing positions of distal landmarks and by the optic flow teld. Proprioception (including veslibt, lar sensing as well as kines- hetic feedback from muscles. tendons. and joints) provides cues to the navigator's velocity and acceleration. In 1he research reported here, we asked how well people update heir inlernal representation of location and orientation as they rave[ in space under conditions in which these cues are reduced or unavailable, including conditions in which they do not physically move at all. The conditions examined included wafking without vision (proprioceplive cues...

This paper tests the generality and implications of an "encoding-error" model (Fujita et al. 1993) of humans' ability to keep track of their position in space in the absence of visual cues (i.e., by nonvisual path integration). The model proposes that when people undergo nonvisually guided travel, they encode the distances and turns that they experience, and their errors reflect systematic inaccuracies in the encoding process. Thus when people try to return to the origin of travel, they base their response on mis-encoded values of the outbound distances and turns. The two experiments reported here addressed three issues related to the model: (i) whether path integration is context-dependent and if so, how rapidly it adapts to recently experienced distances and turns; (ii) whether effects of experience can be specifically attributed to changes in the encoding process, and if so, what changes; and (iii) whether the encoding process represents distances and turns in the individual paths without considering their spatial relationship to one another (i.e., an object-centered representation). Testing these issues allows us to evaluate and develop the model.

Human orientation and spatial cognition partly depends on our ability to remember sets of visual landmarks and imagine their relationship to us from a different viewpoint. We normally make large body rotations only about a single axis which is aligned with gravity. However, astronauts who try to recognize environments rotated in 3 dimensions report that their terrestrial ability to imagine the relative orientation of remembered landmarks does not easily generalize. The ability of human subjects to learn to mentally rotate a simple array of six objects around them was studied in 1-G laboratory experiments. Subjects were tested in a cubic chamber (n = 73) and a equivalent virtual environment (n = 24), analogous to the interior of a space station node module. A picture of an object was presented at the center of each wall. Subjects had to memorize the spatial relationships among the six objects and learn to predict the direction to a specific object if their body were in a specified 3D orientation. Percent correct learning curves and response times were measured. Most subjects achieved high accuracy from a given viewpoint within 20 trials, regardless of roll orientation, and learned a second view direction with equal or greater ease. Performance of the subject group that used a head mounted display/head tracker was qualitatively similar to that of the second group tested in a physical node simulator. Body position with respect to gravity had a significant but minor effect on performance of each group, suggesting that results may also apply to weightless situations. A correlation was found between task performance measures and conventional paper-and-pencil tests of field independence and 2&3 dimensional figure rotation ability.

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 subject's 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 invol...