Pigeons encode relative geometry

Pigeons were trained to search for hidden food in a rectangular environment designed to eliminate any external cues. Following training, the authors a dministered unreinforced test trials in which the geometric properties of t he apparatus were manipulated. During tests that preserved the relative geo metry but altered the absolute geometry of the environment, the pigeons con tinued to choose the geometrically correct corners, indicating that they en coded the relative geometry of the enclosure. When tested in a square enclo sure, which distorted both the absolute and relative geometry, the pigeons randomly chose among the 4 corners, indicating that their choices were not based on cues external to the apparatus. This study provides new insight in to how metric properties of an environment are encoded by pigeons.