Rats in a transparent morris water maze use elemental and configural geometry of landmarks as well as distance to the pool wall

The aim of this study is to evaluate what are the dimensions of a panorama of discrete landmarks that a rodent will store in order to return to a previously visited target. Rats were trained to locate a hidden platform in a circular pool of clouded water set within a quasi-spherical enclosure. In order to find the platform, they had to learn the geometric relations between the platformand a surrounding set of three discrete landmarks, highly visible through the transparent wall of the pool. In test trials without a platform, the array of landmarks was so manipulated as to dissociate the effect of actual distance to the landmarks, of their angular separation, and of their apparent dimension. Animals were shown to rely equally on angular separation and apparent dimension. The role of actual distance could not be definitely ascertained, as animals were shown to additionally rely on the distance to the pool wall in order to locate the platform