Route Memory and Cognitive Maps: Evidence from Behavioral Experiments in Virtual Environments

In the development of navigation behavior, one important step is the transition from routes to maps. Route behavior is characterized by the repetition of previously learned sequences of sensory input and performed movements and can be modeled by chains of stimulus-response-stimulus (SRS) associations. The current view (“local position information”) elicits a movement decision from which in turn the next view may be expected. For each goal, the whole route has to be learned and stored, even if routes to different goals share common segments. Map behavior makes use of goal independent knowledge of the spatial layout of the environment; such knowledge is usually called a cognitive map. In a series of experiments using virtual reality technology, we investigated the navigation ability of human subjects. The maze was composed of streets forming a regular hexagonal grid and buildings placed at the junctions in the angles between the streets (“Hexatown”). Subjects performed simulated movements by hitting the buttons of a computer mouse. Movement started and ended at so-called decision points, i.e. the junctions of the streets. Pure turns could be performed in steps of 60 degrees. When looking into a street, a translation down that street could be performed that ended at the next junction. Subjects were released at some junction and had to find various buildings presented to them as a printout on a sheet of paper (see Gillner and Mallot, J. Cogn. Neurosci., in press). In the talk, we will review a number of experiments performed in the Hexatown environment. With respect to the route vs. map dichotomy, three important results have been obtained: 1. Persistence: Subjects tend to repeat movement decisions when coming back to a previously visited view. This is evidence for simple stimulus-response associations as would be expected in route memory. 2. View-based representation: After learning a given route, we replaced individual buildings along that route. Results indicate that movements are associated to views of individual buildings, not to configurations of buildings at each junction (“places”). 3. Transfer: Subjects were able to transfer knowledge from one route to another. This is an indication of goal-independent knowledge (cognitive map). In conclusion, the data show that humans simultaneously use both route and map type knowledge of the environment. A common framework for the two types of knowledge based on the view-graph (Schölkopf and Mallot, Adaptive Behavior 3:311-348, 1995) will be discussed