Geometry and landmark representation by pigeons: evidence for species-differences in the hemispheric organization of spatial information processing?

In this study, we investigated how pigeons (Columba livia) represent environmental geometry and landmark information. Birds learned to locate the centre of a square arena by means of geometric cues alone, or by means of both geometric and landmark cues. By manipulating the type of information available at training and testing, we assessed which cues the birds had encoded, and through the use of monocular occlusion we examined how the information was represented by the two brain hemispheres. Our results show that both brain hemispheres encoded geometric and landmark information. During all viewing conditions, the geometric representation was based mainly on an absolute metric for distance. The relative use of geometry and landmarks was experience dependent. With both brain hemispheres available birds relied, to a greater degree, on geometric information and used it in a more integrated way than with either hemisphere alone. Overall, our findings show a different pattern for the hemispheric encoding of geometric and landmark information by the pigeon than that previously reported for the domestic chick. Our results suggest that the organization of spatial information processing in the left and right brain hemispheres of birds may be more diverse than what is currently known.