Author ' s personal copy Using perceptrons to explore the reorientation task

The reorientation task is a paradigm that has been used extensively to study the types of information used by humans and animals to navigate in their environment. In this task, subjects are reinforced for going to a particular location in an arena that is typically rectangular in shape. The subject then has to find that location again after being disoriented, and possibly after changes have been made to the arena. This task is used to determine the geometric and featural cues that can be used to reorient the agent in the arena. The purpose of the present paper is to present several simulation results that show that a simple neural network, a perceptron, can be used to generate many of the traditional findings that have been obtained using the reorientation task. These results suggest that reorientation task regularities can be explained without appealing to a geometric module that is a component of spatial processing. 2009 Elsevier B.V. All rights reserved. 1. The reorientation task The ability to orient and navigate in space is critical for the survival of humans and animals. Studies of navigation in indoor environments have found that humans and other animals can use available external cues to determine direction (Cheng & Newcombe, 2005). Such cues can include the overall shape of the environment (geometric cues), as well as other available landmarks or local elements that might also be placed in the environment (feature cues). Geometric cues are presumed to be relational, while feature cues are not: ‘‘A geometric property of a surface, line, or point is a property it possesses by virtue of its position relative to other surfaces, lines, and points within the same space. A non-geometric property is any property that cannot be described by relative position alone” (Gallistel, 1990, p. 212). One question of considerable interest is the extent to which either geometric or feature cues are used to govern navigation. One approach that has been used extensively to answer this question is the reorientation task, first introduced by Cheng (1986). In this paradigm, an agent is placed within an enclosure or arena that is usually rectangular in shape. The metric properties of the arena (i.e., length of walls, angles between walls) combined with the distinction between left and right (e.g., the long wall is to the left of the short wall) provide geometric cues. Colors of walls, or the visual properties of additional objects added to the arena (e.g., placed at each corner of a rectangular enclosure) can be used to provide feature cues (see Fig. 1). In the reorientation task, an agent learns that a particular place – usually a corner of a rectangular arena – is a goal location. The agent is then removed from the arena, disoriented, and returned to an arena, with the task of using the available cues to relocate the goal. The agent can, of course, be placed back into the original, unaltered arena. Of more interest are experimental conditions in which the arena has been changed in some way. For example, after training in one arena (e.g., Fig. 1B or D) the subject might be placed back into an arena after the feature cues have been moved to different locations (e.g., Fig. 1C or E). This manipulation places feature cues in conflict with geometric cues. Will the agent move to a location defined by geometric information, or will it move to a different location indicated by feature information? Extensive 0010-0277/$ see front matter 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cognition. 2009.09. 006 * Corresponding author. E-mail address: mdawson@ualberta.ca (M.R.W. Dawson). Cognition 114 (2010) 207–226