Spatial Cognition and Computation 2: 135–156, 2000.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Rats in a transparent morris water maze use elemental
and conﬁgural geometry of landmarks as well as
distance to the pool wall
and VALÉRIE DERIVAZ
Laboratoire d’Ethologie, Faculté de Psychologie et des Sciences de l’Education, Université
de Genève, 54, Route des Acacias, CH-1227 Carouge, Switzerland
author for correspondence, E-mail: firstname.lastname@example.org)
Abstract. 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 platform and 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.
Key words: geometric information, place navigation, rodents, spatial memory, stimulus
control, visual landmarks
In the Morris water maze test (Morris 1981), a swimming animal, generally
a rat or a mouse, must repeatedly locate a submerged escape platform hidden
under opaciﬁed water in a round pool. In order to do this, the animal uses the
panorama surrounding the pool to determine its own location within the pool,
both when safely landed on the platform and when swimming to ﬁnd it. The
Morris water maze is a classical test of learning and memory. However, the
ability to return towards an invisible goal by means of surrounding landmarks
has far-reaching implications.
When travelling through known territory rodents resort to two comple-
mentary navigation systems. The ﬁrst is path integration, the process by
which the animal uses information generated by its own movement to