Dead Reckoning in a Desktop Virtual Environment

Abstract

Dead reckoning, knowing where one is in relation to a particular location without reference to external landmarks, is a widely cited phenomenon that has been observed in a wide variety of animals. A common test for dead reckoning is the triangle-completion task in which subjects navigate forward a specified distance, then turn and navigate another specified distance, then are allowed to return directly to the starting location (making a triangle). The common finding for ants, hamsters, and blindfolded humans is to commit a positive rotational error, (i.e. to over-rotate).

The present study used a desktop virtual environment to test human distance estimation and dead reckoning. In the first two experiments, a distance estimation task in which the only cue was optical flow was developed, and the accuracy of human distance estimation was assessed. Experiment 1 was a pilot study which instructed methods of improved experimental control for Experiment 2, in which participants produced highly accurate distance estimations in conditions of optical flow (but not in conditions without optical flow). The third experiment was a partial replication of a published virtual-environment study (Kearns, Warren, Duchon & Tarr, 2002) which tested humans in an immersive virtual environment on the triangle-completion task. The present study successfully reproduced the published results, supporting the use of the desktop virtual environment. The final experiment expanded the manipulation of key parameters of the triangle-completion task (i.e., turning angle and leg-length), to assess how larger ranges of each affected human dead reckoning. Participants’ estimates on long itineraries (Experiment 4) were more accurate than on short itineraries (Experiment 3). The improved accuracy on long itineraries suggests that previous findings of highly stereotypic responses were due to methodological limitations, not human limitations. These experiments show that humans are able to make accurate distance and dead reckoning estimations in a desktop virtual environment, and demonstrate the viability of the desktop virtual environment as a research tool.