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Abstract

Spatial behavior in humans and animals includes a wide variety of behavioral competences that make use of many sensory cues, including vision. The visual input contains
various cues about the observers current position (e.g., from views and local landmarks), the compass direction (e.g., provided by global landmarks), and egomotion (e.g., from optic flow). Here we investigate the role of global vs. local landmarks in a route finding task. If navigation relies more on ‘global’ landmarks for a route finding task then an allocentric description should be remembered; such as “When you reach the church square, go towards the tower on the mountain”. Alternatively, ‘local’ landmarks could guide navigation decisions by view-movement associations; e.g. “When you come to the church, turn right”. Evidence for the last strategy was presented by Gillner and Mallot (Journal of Cognitive Neuroscience, in press).
We performed an experiment in a virtual environment called “Hexatown”. Hexatown consists of a regular hexagonal grid of junctions joined together by streets. At each junction
there are three buildings, or other objects. Additionally, we provide global direction or compass information by placing six global landmarks distributed equally on a mountain range surrounding Hexatown. Subjects navigated in Hexatown by pressing the buttons of a computer mouse. According to their movement decisions, egomotion was simulated.
Subjects had to learn the route back and forth between two specific buildings. Awareness of global landmarks was assessed by an additional pointing task. In the test-phase individual junctions were approached and the subjects’ movement decision was recorded.
Two conditions were used: a ‘consistent’ condition, which was the same as in the training phase, and a ‘conflict’ condition. Conflict was produced by transposition of objects such that the global and local strategies predicted different movement decisions.
In the consistent condition, i.e., with unchanged objects, 20 subjects made 85 correct decisions out of a total of 160. In the conflict condition, 77 of the decisions were in
agreement with the local and 23 with the global strategy. This supports our previous finding that local views play a dominant role in making route judgements.
In a control experiment we tested whether subjects could use the global landmarks at all. We reduced the local information in the maze and instructed the subjects to attend to the global landmarks. In this case, 76 of the 80 decisions were consistent with global landmark information. Since no local information was provided in this control experiment the remaining 24 of the decisions were errors. We conclude that subjects prefer local landmarks when available, but are also able to use global landmarks for route finding, when they are instructed to attend to them.