Rats (Rattus norvegicus) encode the shape of an array of discrete objects.

To navigate efficiently, a traveler must establish a heading using a frame of reference. A large body of evidence has indicated that humans and a variety of nonhuman animals utilize the geometry, or shape, of enclosed spaces as a frame of reference to determine their heading. An important and yet unresolved question is whether shape information from arrays of discrete objects and enclosed environments are represented, and utilized, in the same way. In the present study, rats were presented with a reference memory task in which they had to find water that was hidden in 1 of 4 discrete and unique objects placed at the vertices of a rectangle. The results indicate that rats could utilize both feature and geometry cues to locate the hidden goal. The rats' performance declined during transformation tests using a triangular array, indicating that the rats may have encoded the primary axis of the object array, rather than local cues, to direct their search.