Animal visual perception

Perception processes can be investigated at the physical (concerning the stimulation from the environment to the receptors), physiological (the processes taking place in the neural system), and psychological (the ‘sense’ of perception, the outcome produced by the physical stimulation and the physiological processes) level. The present paper focuses on visual perception, mainly from a psychological level of investigation, and revises comparative literature, highlighting both similarities and differences in the visual structures and functions in different animal classes. For this purpose, the structure of the current eyes is described in a comparative perspective, as well as perceptual organization and object recognition processes, color perception, three-dimensional structuring of the image, and motion perception. Finally, the literature about comparative susceptibility to various visual illusions will be discussed, as illusory perception has been revealed to be a most useful tool to unveil the perceptual algorithms shared by the different species. In spite of major differences between animal species in the structures in charge of perception and in the adaptations to specific ecological niches, experimental data presented here will lead to the conclusion that a number of basic perceptual principles of organization and functioning are shared between species.