Reorienting in Virtual 3D Environments: Do Adult Humans Use Principal Axes, Medial Axes or Local Geometry?

Althea H Ambosta,Debbie M Kelly,James F Reichert,Paul Graham

doi:10.1371/journal.pone.0078985

Abstract

Studies have shown that animals, including humans, use the geometric properties of environments to orient. It has been proposed that orientation is accomplished primarily by encoding the principal axes (i.e., global geometry) of an environment. However, recent research has shown that animals use local information such as wall length and corner angles as well as local shape parameters (i.e., medial axes) to orient. The goal of the current study was to determine whether adult humans reorient according to global geometry based on principal axes or whether reliance is on local geometry such as wall length and sense information or medial axes. Using a virtual environment task, participants were trained to select a response box located at one of two geometrically identical corners within a featureless rectangular-shaped environment. Participants were subsequently tested in a transformed L-shaped environment that allowed for a dissociation of strategies based on principal axes, medial axes and local geometry. Results showed that participants relied primarily on a medial axes strategy to reorient in the L-shaped test environment. Importantly, the search behaviour of participants could not be explained by a principal axes-based strategy.

Highlights

Orientation is the initial phase of navigation whereby an individual determines a sense of heading or direction in which to begin travelling
Distinct panels placed in each corner of the environment served as featural cues and the differential lengths of the walls coupled with sense information served as geometric cues
The current study was the first to examine whether adult humans encode the geometry of an environment using principal axes, medial axes or local geometry

Summary

Introduction

Orientation is the initial phase of navigation whereby an individual determines a sense of heading or direction in which to begin travelling. Cheng [1] was the first to show that rats encoded environmental geometry to reorient despite the presence of salient featural cues. After considerable training the rats eventually learned to search in the corner associated with the correct featural cue; they committed rotational errors by searching in the corner diagonally opposite to the correct corner. This finding of systematic rotational errors supported that, despite the presence of seemingly more salient features, the rats showed a reliance on the geometric shape of the environment to reorient. Following Cheng’s original investigation other studies have supported a widespread encoding of geometry by numerous other species (see [3] for a review)

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