The study of hemispheric specialization for categorical and coordinate spatial relations in animals

This article reviews some of the most representative studies in the animal literature pertaining to the processing of categorical and coordinate spatial relations and of their hemispheric control. Although the processing of coordinate and categorical cognition has been studied directly with nonhuman primates, experiments on cerebral asymmetries in avian spatial orientation are also reviewed. It turns out that Kosslyn's model concerning the existence of two types of spatial representations each with a specific lateralization pattern has received some support in nonhuman primates and is only weakly verified in the avian studies. Procedural differences might explain some but certainly not all of the discrepancies between the human and the animal literature. It is especially the laterality hypothesis of a left hemisphere advantage in relational cognition and a right hemispheric superiority in judging absolute distances that is not supported by the animal data. Studies specifically addressing Kosslyn's hypotheses and bearing on the use of similar stimuli, procedures and methods between the species tested are needed in order to lead to firm conclusions about the existence of coordinate versus categorical processing systems in animals.