Place learning in humans: The role of distance and direction information

Although the process of establishing a memoryof a location is necessary for navigation,relatively little is known about theinformation that humans use when forming placememories. We examined the relative importanceof distance and angular information aboutlandmarks in place learning. Participantsrepeatedly learned a target location inrelation to three distinct landmarks in animmersive computer-generated (virtual)environment. Later, during testing, theyattempted to return to that location. Theconfigurations of landmarks used during testingwere altered from those participants learned inorder to separate the effects of metricdistance information and information aboutinter-landmark angles. In general,participants showed greater reliance ondistance information than angular information. This reliance was affected by nonmetricrelationships present during learning, as wellas by the degree to which the learnedenvironment contained right or straightangles.     

Three dimensional spatial memory and learning in real and virtual environments

Human orientation and spatial cognition partlydepends on our ability to remember sets ofvisual landmarks and imagine their relationshipto us from a different viewpoint. We normallymake large body rotations only about a singleaxis which is aligned with gravity. However,astronauts who try to recognize environmentsrotated in 3 dimensions report that theirterrestrial ability to imagine the relativeorientation of remembered landmarks does noteasily generalize. The ability of humansubjects to learn to mentally rotate a simplearray of six objects around them was studied in1-G laboratory experiments. Subjects weretested in a cubic chamber (n = 73) and aequivalent virtual environment (n = 24),analogous to the interior of a space stationnode module. A picture of an object waspresented at the center of each wall. Subjectshad to memorize the spatial relationships amongthe six objects and learn to predict thedirection to a specific object if their bodywere in a specified 3D orientation. Percentcorrect learning curves and response times weremeasured. Most subjects achieved high accuracyfrom a given viewpoint within 20 trials,regardless of roll orientation, and learned asecond view direction with equal or greaterease. Performance of the subject group thatused a head mounted display/head tracker wasqualitatively similar to that of the secondgroup tested in a physical node simulator. Body position with respect to gravity had asignificant but minor effect on performance ofeach group, suggesting that results may alsoapply to weightless situations. A correlationwas found between task performance measures andconventional paper-and-pencil tests of fieldindependence and 2&3 dimensional figurerotation ability.     

Human navigation ability: Tests of the encoding-error model of path integration

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.Subjects who were blindfolded or had restricted vision were led through two legs of a triangle and the turn between, then tried to return to the origin. Paths varied in whether experienced legs and turns were small or large (Experiment 1) and in variability of return and outbound course (Experiment 2). Response turn, distance and course were determined. The assumption of immutable encoding functions was not supported; encoding processes were context dependent, although they did not adapt within a block of trials. Although effects of experience could be accounted for by the model, the affected parameters were not always as predicted, and in some cases additional parameters were necessary. Results of manipulating variability in return course were consistent with the model's assumption of object-centered representation.     

Contents of Volume 1

Volume Contents

Contents of Volume 1